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WAQUOIT BAY ESTUARY CONCEPTUAL MODEL
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Figure 7. Waquoit Bay estuary conceptual model, .continued.
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response pathways. Eeigrass habitat is the common assessment endpoint for each of the source-
to-response pathways represented in the model. Common measures (eeigrass habitat cover and
extent) apply to each pathway. These measures are depicted outside the direct source-to-
assessment endpoint pathways because they represent the result of ecological response rather than
a direct measure of the response or attributes of the response pathways.
The following discussion is separated into two parts. The first provides predictive
hypotheses about the effects of primary stressors depicted in the watershed conceptual model
(Figure 2). These hypotheses and predictions are then followed by a descriptive conceptual model
and hypotheses on the multiple pathways for loss of eeigrass from the variety of sources of these
stressors and source-to-response pathways. Each of these pathways is illustrated in the eeigrass
habitat conceptual submodel (Figure 3).
Stressor Hypotheses
The watershed conceptual model (Figure 2) contains five primary stressors for eeigrass:
nutrients, sediments, physical.alteration of habitat, toxics, and disease. Based on conclusions
drawn from available information, multiple stressor effects have caused eeigrass to decline over
the last 40 years. Each stressor has multiple sources. Reduction of one stressor or source is not
likely to be sufficient for reestablishing eeigrass in the bay, although nutrient reduction is a
necessary prerequisite.
Nutrients. Increased nitrogen loading in estuarine waters causes shading from excess
growth of macroalgae, phytoplankton, and epiphytes. Historical and steady state inputs of
nitrogen to ground water .will continue to influence algal growth for up to 100 years. Additional
development in the watershed will add to this nitrogen loading. Light attenuation in-shallow
estuaries might not be great enough to eliminate eeigrass altogether, but continuing inputs of
nitrogen from current activities will prevent eeigrass recovery. Sub-bays with the greatest
nutrient loads will have more macroalgae and less eeigrass. Those sub-bays with less nutrient
loading will have less macroalgae and more eeigrass.
Suspended Sediments. Shadmg from resuspended sediments caused by physical
disruption of bottom sediments results hi decreased growth and the death of eeigrass plants.
Physical Alteration of Habitat Available habitat for eeigrass has changed and will
continue to change .because of (1) loss of appropriate habitat from dock construction; (2)
mechanical disruption from clam digging, boat props, and moorings, which cut eeigrass blades or
uproot and kill eeigrass plants; and (3) subdivision of the meadow as a result of eeigrass death
caused by mechanical disruption, disrupting community integrity and altering meadow
composition.
Toxics.. Toxics cause physiological stress on eeigrass plants, leading to slow growth.
This could exacerbate effects from other stressors.
Disease. Slime mold acts synergistically widi reduced.light to decrease eeigrass growth,
and water currents transport infected eeigrass blades, broken by physical disruption, to new areas.
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Predictions
• The replacement of eelgrass beds with fast-growing macroalgae will continue unless
the amount of nitrogen entering the bay is reduced. Reestablishment of eeigrass will
require reduction of nutrients.
• Reestablishment of eelgrass from reduced nutrient loading will occur only over a long
time period to account for the time travel of nutrient laden ground water to the Bav.
• Reduction of nitrogen is a necessary but not sufficient requirement for eelgrass re-
establishment Habitat alteration from physical disruption will need to be reduced or
confined to specific areas to allow teestablishment
• The co-occurrence of wasting disease, toxics, and reduced water clarity might result in
the complete elimination of eelgrass from the Waquoit Bay system. Complete
elimination means that replanting might be the only means of reestablishing eelgrass
meadows.
Conceptnaj) \fodei
The primary stressors have multiple sources. The opportunity to reduce these sources of
stressors are of primary management concern. The hypotheses below describe the eelgrass-
specific conceptual model to illustrate the multiple ways eelgrass can be lost from this system and
to provide insights on where management action is most feasible... This discussion provides the
basis for the conceptual model diagram shown in Figure 3.
.Disease. The marine slime mold, Labyrinihuia, causes "wasting disease." It is
opportunitistic and likely to cause infection in stressed populations in more saline waters.' The
infection of eelgrass located in higher-salinity areas of .Waquoit Bay leads directly to loss of
eelgrass by death of infected individuals. Exposure pathways for the disease are not known;
however, salinity influences infection such that eelgrass in areas of lower salinity is less likely to
be infected. These areas are important for reestablishment.
Nutrients.. Nitrogen is the primary nutrient of concern in the estuary. Nitrogen
potentially enters the bay through multiple pathways including ground water discharge, air
deposition, point source discharges, and impervious surface run-off. Exposure pathway analysis
by Valiela et at (1992) suggests that the principal pathway is via groundwater from septic system
inputs (Appendix E, Figure E-6). The resulting increase in surface water and sediment nitrogen
concentrations leads to increased growth of epiphytes, macroalgae, and microalgae. Epiphyte
growth on eelgrass leaves decrease light availability by shading and increases leaf effective surface
area, causing possible weighting and burial of eelgrass from increased siltation on leaves.
Increased growth of macroalgal mats leads to direct shading of eelgrass and decreased light
penetration. Phytoplankton growth increases water turbidity, decreasing light penetration to
eelgrass. Algal growth also contributes to increased organic sediment, which might be
resuspended by physical disruption (below) and contains a reserve of nutrients.
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Construction and Recreational Activities. Boat propellers impinging on bottom
sediments; dredging; construction of docks, piers and marinas; clam raking; mooring; and erosion
in the watershed cause increased suspended sediments or resuspension of bottom sediments.
Hydrographic conditions (e.g., wave amplitude, frequency, and direction; current velocity) act as
forcing functions that can increase water turbidity. Turbidity increases shading and decreases
light penetration. This leads to reduced eelgrass photosynthesis, growth decline, and death of
eelgrass. It also causes siltation onto eelgrass leaves, compounding the effect of epiphyte growth
discussed in the previous pathway.
Docks and Piers. Docks directly block light and reduce available habitat for eelgrass,
leading to reduced eelgrass photosynthesis and loss of shaded eelgrass. Docks and piers also
provide the basis for increased boat traffic, which leads to disturbance of sediments and increased
turbidity in areas around the docks and piers. Great River, a tributary in the Waquoit Bay
watershed, will show a loss of eelgrass in correlation with increased dock building.
Lawn Care, Agricultural, and Industrial Activities. Care of residental and commercial
property lawns, agricultural activities (e.g., cranberry bogs), and industrial activities (e.g., MMR)
in the watershed are a source of a variety of toxic chemicals. These may cause physiological
stress in eelgrass, leading to reduced growth and death of eelgrass plants. Exposure pathways
and effects from these sources of potential stress are little known.
Boat Propellers, Clam Rakes, Moorings. Boat propellers, clam rakes, and moorings
directly disrupt bottom sediments, causing physical alteration of habitat and mechanical
destruction of eelgrass blades, resulting in death or stress to the plant Repeated activities without
sufficient recovery time will result in decline in eelgrass beds because of direct loss of plants, and
from the creation of small patches, increasing vulnerability to other stressors (e.g., storm events).
Boating activities that chum up bottom sediments will increase the amount of suspended
sediments, increasing turbidity and decreasing light penetration to eelgrass beds. Epiphytes
growing on eelgrass blades provide good depositional surfaces for suspended solids and can
weigh down the eelgrass blades causing them to sink to the bottom where they die from
insufficient light or suffocation (Short, 1989).
2.32.2 Resident Estuarine Finfish Diversity and Abundance: Risk Hypotheses and
Conceptual Model
The conceptual models and risk hypotheses for the resident finfish diversity and abundance
assessment endpoint include sources and stressors, cascading ecological effects, and response
pathways. Resident finfish is the common assessment endpoint for each of the source-to-response
pathways represented in the model. Common measures (diversity and abundance) apply to each
pathway. These measures are depicted outside the direct source-to-assessment endpoint
pathways because they represent the result of ecological response rather than a direct measure of
the response or attributes of the response pathways.
The following discussion describes the principal stressors represented in the watershed
conceptual model (Figure 2) and specific predictions to. consider. This is followed by the
presentation of the finfish conceptual model and descriptive hypotheses about relationships
depicted in the model.
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Stressor Hypotheses
Multiple stressor effects are resulting in lowered reproductive success of adult resident
finfish, as well as lower survival of eggs and juvenile finfish. Each stressor has multiple sources.
Determining the relative contribution of these stressors will be important for setting management
priorities.
Nutrients. Increased nitrogen loads alter finfish diversity and abundance through
excessive macroalgal growth, which results in (1) loss of eelgrass habitat for breeding, feeding,
and hiding and (2) hypoxic and anoxic conditions that result in physiological stress, exposure to
predation, and suffocation.
Suspended Sediments. Increased sediment hi the water column alters finfish breeding,
feeding, and hiding habitat by (I) reducing growth of eelgrass, (2) covering available habitat, (3)
smothering eggs and juveniles, and (4) reducing feeding success of visual predators.
Physical Alteration of Habitat Development of land adjacent to prime finfish nursery
habitats causes a direct loss of available nursery areas and contributes to sediment and nutrient
loading in the vicinity of nursery areas. Direct physical alteration of nursery areas from dredging,
boat prop disturbance,and changes in flow patterns from inlet changes and armoring of coasts
alters quality or removes habitat from potential use.
Toxic Chemicals. Multiple sources of toxic chemicals from pesticide application, air
pollution, lawn maintenance, point source discharges, nonpoint runoff and chemicals used on
docks and boats combine to alter survival and reproduction of juvenile finfish. Stress from
hypoxic and anoxic conditions exacerbates the effects of toxicity.
Harvest Pressure. Recreational fishing removes reproductive adults from the population
of resident finfish. Although offshore fishing alters the available adult stock returning to Waqupit
Bay, this reflects regional impacts and no hypotheses are pursued for this portion of the finfish
community.
Predictions.
Loss of eelgrass habitat (from multiple stressors) will favor species associated with
open-water, nonvegetated habitats such as Atlantic silverside, adult summer flounder,
and winter flounder as well as rock crabs and green crabs, over those species
associated with vegetated habitats such as tidewater silverside, juvenile summer
flounder, grass shrimp, rainwater killifish. juvenile tautog, fourspine stickleback, and
striped killifish.
Loss of eelgrass habitat and projected changes in the functional aspects of the finfish
community will result in (1) increase-in omnivores; (2) decline in top carnivores; (3);
shift from benthic to pelagic habitats; (4) decline in total number of species, estuarihe
spawner species and estuarine resident species; (5) increase in disease incidence and
morphological abnormalities; (6) decrease in eelgrass habitat quality prior to physical
habitat loss; (7) increase in dominance of eutroohic tolerant species where dominance
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.represents the ntlmber of species accounting for 90 percent of the total numbers or
biomass;-and (8) higher fish density and biomass (abundance) in medium-quality
compared to low-quality habitats (Deegan, 19 ).
« Increasing contaminant inputs from recreational activities and future toxicity from
contaminated ground water plumes from MMR will increase abundance of tolerant
species and increase incidence, of fmfish malformations and disease.
• Anoxia and hypoxia will slow growth, maturation, and reproduction of fmfish (e.g.,
Atlantic silversides, juvenile winter flounder, and juvenile tautogs versus
mummichogs),
Conceptual Model
The primary stressors have multiple sources. The opportunity to reduce these sources of
stressors are of primary management concern. The hypotheses below describe the finfish
conceptual model to illustrate the multiple ways finfish diversity and abundance are likely .to
change and to provide insights on where management action is most feasible. This discussion
provides the basis for the conceptual submodel diagram shown in Figure 4.
Recreational and Commercial Fishing, Estuarine and offshore fishing remove
reproductive aged fish from the population. This mortality will exaccerbate other losses to adults,
juveniles and eggs from other stressors and can change the dynamics of the finfish community
resulting in shifts in competition, feeding patterns and other behaviors.
Nutrient Loading. Nutrient loading increases algal production in the estuary. Increased
production leads to increased organic matter loads and increased respirational oxygen demand,
resulting in periodic oxygen stress and occasional fish kills on warm, cloudy, calm days in
summer, when the bay may stratify. Nutrient loading also might lead to loss of eelgrass (see
eelgrass conceptual submodel Figure 3). Eelgrass beds are a nursery area for juvenile finfish;
hence, loss of eelgrass may lead to declines in fish recruitment and fish populations.
" Toxic Chemicals. Toxic chemicals from lawns, agriculture, impervious surfaces and the
MMR plumes might cause direct morbidity and mortality of resident finfish in all age classes
although some age classes could be more susceptible. Toxic chemicals also might lead to loss of
eelgrass (see eelgrass conceptual submodel Figure 3). Eelgrass beds are a nursery area for
juvenile fmfish; hence, loss of eelgrass might lead to declines in fish recruitment and eelgrass
dependent fish populations.
Sediments, Physical Alteration and Disruption. These stressors all can lead to loss of
eelgrass (see eelgrass conceptual model Figure 3). Eelgrass beds are a nursery area for juvenile
finfish; hence, loss of eelgrass can lead to declines in fish recruitment and fish populations. These
stressors might also lead to loss of salt marshes through direct alteration. Salt marshes are
spawning and nursery areas for several estuarine finfish and forage fish, hence, loss of salt marshes
might lead to declines in fish recruitment and fish populations.
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23.23 Conceptual Models and Hypotheses for Other Assessment Endpoints
Development of conceptual models ar.d risk hypotheses for the remaining six assessment
endpoints is ongoing, but they are not ready for presentation at this time. The models developed
for eeigrass and ftnfish provide a basis for determining how best to present information and
develop the process. The conceptual models represent considerable information, but in many
cases data are not available at this time to conduct an evaluation of posed hypotheses and
predictions for these two endpoints. They are presented to allow managers and scientists in the
watershed to consider potential research that will provide the basis for pursuing a more complete
risk assessment. Further analyses of available data will allow the Team to refine hypotheses for
the these and the other endpoints.
2.4 ANALYSIS PLAN
The large number of assessment endpoints identified in this risk assessment required a
preliminary evaluation of overlap among endpoints. A comparative risk analysis was used to help
define which stressors, assessment endpoints, and relationships should be examined further. To
do this preliminary analysis, stressors were ranked in terms of potential risk to all resources in the
watershed, as well as risk to individual endpoints. Those stressors and endpoints. deemed most
important are featured here, although comparable risk hypotheses have been developed for each
of the assessment endpoints identified. The following analysis was conducted by the risk
assessment team and is considered preliminary, ft requires additional verification and peer review
by scientists in the watershed.
2.4.1 Comparative Risk Analysis
To conduct a comparative risk analysis, a process called "fuzzy set,** which is based on
best professional judgment (Harris et al., 1994; Wenger and Rong, 1987), was used. This
approach was applied to each endpoint and stressbr. The fuzzy set approach is a decision analysis
method for ranking alternatives according to multiple criteria. Applied to ecological risk
assessment (Wenger and Rong, 1987; Harris et al., 1994), stressors are the alternatives and the
assessment endpoints are the criteria. The analysis then ranks the stressors in order of greatest
overall contribution of risk to the endpoints.
An impact matrix for the Waquoit Bay watershed, derived from the conceptual model, is
shown in Table 5. Each column represents a single endpoint, and each row a single stressor from
the conceptual model Every connection in the conceptual model from a ressor to. an assessment
endpoint is represented by a non-zero cell in the effect matrix (Table 5). --marine and freshwater
elements are combined in this matrix, as they are hi the conceptual model. Each cell contains the
effect of a stressor on an endpoint, on an ordinal scale from 0 (no effect) to 3 (severe effect)
(Harris et al., 1994): For example, the effect of nutrients on eeigrass habitat is given a 3 (severe,
indirect effect), but the effect of physical alteration on eeigrass habitat is given a I (slight effect)
(Table 5). The effect of toxic substances on pond trophic state is given a 0, because toxic
substances in the watershed are not thought to affect pond trophic state (no pathway in the
conceptual model).
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Table 5. Hypothesized effects matrix; each ceil represents relative effect of a stressor on an
endpoint.
Suspended
sediments
Rankings were obtained by the difference method, as explained in Wenger and Rong
( 1987) and Harris et al. (1994). The effects of each stressor 7 on endpoint k are subtracted from
the effects of stressor i :
« *» - */* (Harris et at 1994).
The matrix R = (rs) is an m x m matrix of the sums of the above differences for ail endpoints fc
r9 = SD&j). U = 1. 2, .... m
(Harris et al., 1994). See Wenger and Rong (1987) for further formulas. The row sums of matrix
R were used for ranking the stressors; the largest row sum was the dominant stressor (Table 5,
Base Case). Using the impacts of Table 5, nutrients were ranked first, followed by physical
alteration and toxic chemicals, then harvest and flow, and finally suspended sediments and disease
(Table 6).
Stressors can be weighted by me persistence of the stressors if their input is removed.
Persistence of stressors was ranked on a scale of 1 to 5, where 1 represents almost no persistence,
and 5 is an effect that lasts indefinitely (Table 7). Altered flow and physical alteration received a
persistence score of 5 because they are permanent changes that do not reverse themselves. Toxic
chemicals and nutrients received a persistence score of 3 because of the time delay in ground
water travel to reach water bodies. Thus, if sources of either toxics or nutrients were
stopped, substances remaining hi the ground water would still .affect water bodies for some time.
Suspended sediments, harvest pressure, and disease received a score of 1 because they are aH
relatively nonpersistent; Le, if fishing is stopped, there is no "residual" harvest pressure.
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Table 6. Stressor ranks under three scenarios.
Suspended sediments
Results of the weighting are also in Table 6 (weighted column). When weighted, the three
stressors tied previously for third place (altered flow, toxics, and harvest pressure) differentiated,
into third to fifth place (Table 6).
Table?. Relative duration of stressors.
Nutrients
Physical alteration
Altered flow ' •
Toxic chemicals
Harvest pressure
Suspended sediments
Disease
3
5
5
3-
1
1
1
Stressors may interact with one another by exacerbating other stressors (Harris et al.,
1994). interactions among the stressors are shown in Table 8. Bom members of an interacting
pair of stressors receive a score because bom must be present for the interaction to work.
Interaction scores were set at 1 because they are plausible, hypothesized relationships, with no
information on their relative strength or actual existence. Nutrients can enhance the effects of
both suspended sediments and disease by causing excess organic floe that can be resuspended, and
shaded eelgrass may be more susceptible to disease. Excess organic floe contributes to
sedimentation. Toxic chemicals may stress eelgrass plants so that they are more susceptible to
disease.. The resultant rankings reflecting both weighting and interaction (Table 6, rightmost
column) were the same as the weighted scenario only.
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Table 8. Interaction among stressors.
Altered flow
Toxic chemicals
Harvest pressure
Suspended sediments
Disease
0
Ranks were very similar among the three models, showing that the hypothesized effects
matrix (Table 5) was robust to changes in persistence and interaction. Nutrients were always
ranked first; physical habitat alteration was always ranked second. Suspended sediments and
disease were always ranked last Altered riverine flow, toxic chemicals, and harvest pressure
were tied in the middle in the unweighted scenario, but when weights were applied they
differentiated from each other. The robustness of the rankings was due primarily to the" number of
endpoints affected by each stresson Nutrients and physical alteration each affected six endpoints,
and nutrients had two strong effects on two assessment endpoints (eelgrass habitat and pond
trophic status).
The comparative risk analysis presented here must be regarded as preliminary because the
effects matrix (Table 5) has not at this writing been reviewed and agreed to by experts and
knowledgable persons on ecological effects in estuaries. In the absence of quantitative data on
the relative magnitudes of effects of the different stressors, expert consensus is required
2.42 Developinent of a RegtoflalModd of Eelgrass Response to Natrie0tU>adlng
Submerged aquatic vegetation (SAV) is a sensitive indicator of eutrophication in estuaries
(Dennison et aL, 1993) and is easily monitored with aerial photography. As described in Section
2.2, eelgrass beds are preferred habitat of juvenile scallops, and are a nursery and feeding area for
estuarine fish. Eelgrass beds can be identified and quantified from aerial images and can be
distinguished from other S AV (e.g., Ruppia, Codiiari) and from macroalgae and bare sediment
For these reasons, eelgrass cover, was selected as a measurement endpoint for eelgrass habitat,
estuarine finfish habitat, and estuarine benthic invertebrate (including scallop) habitat
Although it has been known for some time that nitrogen loading contributes to estuarine
eutrophication and loss of SAV hi Waquoit Bay and other estuaries of Cape Cod (e.g., Costa
1988; Valiela et aL 1992; D'Avanzo and Kremer, 1994), quantitative relationships between
nitrogen loading or nitrogen sources on the one hand, and the biological response of SAV on the
other have not been developed for estuaries such as Waquoit This is in part because nitrogen,
unlike phosphorus^ is not conserved (le., N may be denitrified or fixed) and because in estuaries,
unlike in lakes, water residence time is more difficult to estimate. The objective of this analysis
will be to develop the link between estimates of modeled nitrogen loading and predicted
ecological effects in the estuary.
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estuaries of Buzzard's Bay. and to larger estuaries such as Tampa Bay (Tampa Bay NEP. 19951.
Therefore, it should also be successful for the estuaries of the South Shore of Cape Cod.
2.4.2.2 Models for Estimating Nitrogen Loading
There are currently three models (CCC, WBLMER. and BBNEP) of nitrogen loading for
Cape Cod estuaries. Each predicts the total N loading from measured watershed variables.
including the amount and distribution of residential septic systems, impervious surfaces, lawns,
natural vegetation, and other sources. The models differ in assumptions on N transformations in
ground water and the fate of atmospheric N deposition on land, but all three result in substantially
similar estimates of total N loading to the estuary (Cadmus, 1995). A fourth model (Sham et al.,
1995) takes into account the time required for nutrient-laden groundwater to travel to surface
waters, where it can contribute to eutrophication. Newly constructed septic systems and
discharges may not contribute to nutrient loading for several decades, depending on the hydraulic
travel time from the source to a surface water body (Sham et al., 1995). By analyzing
construction dates of discharges and travel times. Sham and colleagues, estimated that current
loading to Waquoit Bay is approximately 70 percent of the ultimate loading from existing
structures, and that 90 percent of the ultimate loading is reached in approximately 10 years (Sham
et al., 1995).
The analysis here will take into account ground water travel time, as elucidated by Sham
et aL The Sham et al. analysis used the CCC model as its base and also required a complete land
parcel ^atfth^re for the Waquoit watershed, with date of construction for each parcel, as well as
estimation of ground water flow velocities from the extensive well data in the Waquoit watershed.
A similar analysis at the same level of detail for all watersheds in the model would be prohibitive.
Such a level of detail is probably unnecessaiy.because the three base models for N loading have an
estimated uncertainty of 25 to 40 percent (M. Geist, personal communication). Given the
uncertainty of the base models, it should be possible to develop coarser estimates of travel time
and ccflstniction date and stffite within fe
Given the prediction mat 90 percent of ultimate nitrogen loading is reached in 10 years
(Sham et aL, 1995), travel time can be approximated by estimating areas representing travel times
of 0 to 5 years, 5 to 10 years, and greater than 10 years. On a map, these would appear as
concentric bands around an estuary or parallel to a stream. A first-order approximation would be
to estimate the distance traveled by ground water in 5 years (approximately I km in Sham et al.,
1995) and apply that distance to ail watersheds in the analysis. Land use and dates of .
construction can be estimated for each of the three travel bands from a CIS database, and one of
the N loading models can then be applied to estimate total N from each of the three source areas.
Z4iZ3 Cap* Cod Estnvy ChnnH'tfrf*a*tMi
Approximately 90 semi-enclosed estuaries and subestuaries are on the south shore of Cape Cod
and the islands with a relatively narrow outlet to the sea or to another estuary. Some wiU prove
to be inappropriate for a regional model (e.g., too smalt top isolated, too open), but
approximately 50 estuaries, might be sufficient for development of a regional model. Eelgrass
cover has been digitized from the'Massachusetts DEP aerial images and integrated into the CIS
database for all of these estuaries.
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Characterization of each estuary and subestuary will require assembly of a GIS database
for Cape Cod and the islands. The existing Mass GIS database will provide boundaries,
coastlines, streams, place names, land use, and census data. The Cape Cod Commission has
delineated ground water watersheds for the Cape. The principal activities here will be digitization
of bathymetry from the NOAA charts and characterization of each estuary and subestuary using
GIS. Each estuary and subestuary will be characterized as follows:
Biological (from Mass DEP aerial images):
• Eelgrass cover (percent of total area, percent of area < 4m deep)
• Observations of Ruppia, Codium, and algae in the estuary
Physical (from Mass GIS and NOAA charts bathymetry):
area
maximum Q^ pti^
mean depth
inlet width
inlet length
inlet maximum depth
inlet mean depth
water body type outside of inlet (sound, 1° estuary, 2° estuary)
Total channel length from estuary or subestuary to sound
Watershed and Land Use:
• Watershed area (ground water). Ground water watersheds have been delineated for
Cape Cod estuaries by the Cape Cod Commission.
• Land use (total area hi each land use class)
• Population
• Area, land use, and population within S-year ground water travel time to tidal waters
• Area, land use^and population within 5-to-10 year ground water travel time to tidal
waters .
• Area, land use, and population greater than 10 year ground water travel tune to tidal
waters ...
• Distribution of new construction (< 5 yr old, < 10 yr old) in a watershed
2A2A Eeterass Response Model for Cape Cod Estuaries
Following characterization of each estuary, data.will be plotted to determine whether
relationsHips be delected from scatterplots. The scatterplots will help determine the most
appropriate model: linear, curvilinear, or categorical approaches such as logistic orloglinear
models. At least four alternative models will be examined: models using land use directly as a
predictive variable, models using estimated nitrogen loading as the predictive variable, and models
with and without an estuarine retention time parameter.
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Model 1 (simple land use)
y = a +• bx, +> or, + dx, + e , where
y =- eelgrass cover
.c, = dwellings per unit estuarine surface area in the 0-5 yr travel band
t, = dwellings in the 5- 1 0 yr travel band
.t. = dwellings in the > 10 yr travel band
Model 2 (estimated N loading)
y = a + bx + e , where
x s area! nitrogen loading estimated from one of the N loading models, taking into account the
three ground water travel bands and estimated proportion of new construction in each.
Modeb3and4
Models ! and 2 may be improved with an estuarine retention time parameter, the Vollenweider
parameter (Reynolds, 1984; Costa etaL, 1995):
, where
/„ s average hydraulic retention time •
z * mean depth
Retention time is difficult to estimate in estuaries- because of highly variable wind-induced
and tidal mixing during a tidal cycle (Geyer and Signell, 1994). Retention time can be bounded at
the upper limit by freshwater inflow assuming no tidal exchange (treating the estuary as a lake),
and at the lower limit by freshwater inflow, plus tidal inflow assuming complete mixing every tidal
cycle. Actual mean retention time will be somewhere between these two extremes. A fust-order
approximation for these small estuaries will be to assume 50 percent mixing every tidal cycle, and
calculate retention time accordingly. Alternatively, it has been suggested that macroalgae,
because they are held fast to one spot, intercept nutrients that are carried past them in water
currents and hence are not affected by estuarine retention time. If retention time is unimportant,
then the retention time models will perform poorly relative to models land 2.
2A.2JS Uncertainties Associated with the Eelgrass Response Model
* *
An objective of risk assessment is to characterize uncertainty and its sources that may play
a role in prediction of risk. Sources of uncertainty in the ecological risk assessment include:
• Alternative hypotheses.. Other explanations or interactions operating that were not
addressed or that might impede attainment.of management goals might be 'operating.
• Model uncertainty, m me case of me estoarine analysis, there are three competing.
nitrogen loading models, each of which will be examined for a "best fit" to the eelgrass
response data. The resultant "best fit" model is empirical and does not necessarily
reflect underlying mechanisms; it seeks only the best fit to the data. However, aslong
as the predictions of the best fit model hold, it is sufficient for management
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• Data uncertainty. Data uncertainty includes data collection methods, adequacy of
sample size, random sampling error, and measurement error. Random error (including
natural variability) is part of the data distribution and can be analyzed with empirical or
Monte Carlo methods.
Uncertainties Associated with Factors Affecting Eelgrass
Predictions from the estuarine portion of the risk assessment will include risk of continued
eelgrass habitat loss, or, conversely, probability of eelgrass habitat recovery for given nutrient
management scenarios. These predictions and probabilities will derive from the empirical models
developed in the analysis phase on eelgrass response to predicted nutrient loading. The response
model will not cover several alternative and interacting hypotheses that may also contribute to
eelgrass loss or may prevent eelgrass habitat recovery. Thus, the models are intended to predict
necessary, but not necessarily sufficient, conditions for eelgrass recovery.
Eelgrass requires relatively clear water (Secchi depth = 1-2 m); it will grow in salinities
greater than 10-15 ppt, and sediments composed of fine sands or muddy sands (Batiuk et at.
1992). Necessary and sufficient conditions for eelgrass growth and recovery in Waquoit Bay are:
• Low nitrogen concentrations that are not toxic to eelgrass (<1 MM; Burkholder, 1992)
and that permit eelgrass growth while limiting rapid growth of Cladophora and
Gracilaria. dadophora is characteristic of eutropnic habitats. In Sage Lot Pond, a
subestuary of Waquoit Bay, Cladophora and GracUaria were limited when nitrate
concentration was less than 1 /zM in the. water column and when sediment interstitial
ammonia was less than 1.5 fM (Peckol et aU 1994). Similarly, Batiuk et al. (1992)
recommended nitrogen concentrations less than 0. IS mg/L DIN (<2.4 /jM) to limit
phytoplankton growth in eelgrass habitat of the Chesapeake Bay.
Achieving low nitrogen loading to Waquoit Bay will require some sort of nitrogen
source control* as well as a sufficient lag time to allow nitrogen currently in the ground
water to be flushed out Groundwater travel times hi the watershed might be several
tens of years, depending on distance from a source to a water body (Sham et al.,
1995). Management scenarios to be analyzed will include an estimate of the lag time
necessary for changes in nutrient supply to take effect in the estuary. A secondary
time lag is the pool of nitrogen in the decomposing organic matter, which is thought to
be approximately 3 years' supply (Tampa Bay NEP, 1995). The organic nitrogen pool
may therefore require 3 to5 years to equilibrate to a lower level, but this appears to be
negligible compared to the time lag in the supply rate.
• Absew» of raaoodgal and epiphytic growm capable of overgrowmg and shading
eelgrass. Eutrophication and excess algal production are reversible if nutrient
availability is reduced. Achievement of low nitrogen loading and a reduced nitrogen
pool in the estuary win result in reduced algal growth.
• Low turbidity and tow resuspension of fine organic matter. Because of the sandy-soils
of Cape Cod, mineral turbidity (sift and clay) is not a problem in Cape Cod waters. In
Waquoit Bay, fine organic matter from decomposing algae is resuspended by wind,
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tide, and boat wakes. This organic matter can settle on eeigrass leaves, enhanced by
the surface roughness of epiphytic algae. The epiphytes and the organic sediment
shade the leaves and can inhibit eeigrass growth. Although this mechanism of
sediment entrapment by epiphytes has been proposed to contribute to SAV loss (e.g..
Kemp et al., 1983: Short 1993), it has never been demonstrated to operate in the field
or in the laboratory.
Excess organic matter is a consequence of excess production due to nutrient
enrichment. If the supply of organic matter is reduced, by reducing nutrient loading
and primary production, then the organic matter pool would eventually decline due to
decomposition, burial in the* sediment, or export from the system. Thus, as long as
nutrient loading is reduced, organic matter will decline with it, perhaps delayed by a
time lag of 3 to 5 years (Tampa Bay NEP1995).
• Appropriate sediment for eeigrass growth. Eeigrass can grow in a variety of
sediments, including mixtures of sand and mud, fine sands, and other particle sizes
(Orth and Montfrans, 1984; Bathik et al., 1992; Burkholder et al., 1992). The
sediment has previously been appropriate for eeigrass growth.
• Appropriate salinity for eeigrass growth (>10-15ppt). Available information indicates
that Waqnoit Bay has not freshened.
• Eeigrass propagules. Existing eeigrass root stocks and seed banks might have been
exhausted in the years of decline Natural recolonizan'on is a random event and
depends on nearby seed sources. The remnant eeigrass populations in the subestuaries
Hamblin and Jehu Ponds, as well as offshore populations, may provide seeds to
Waquoit Bay, but there is no way of knowing when such colonization might occur.
Aerial images (1994) show large and extensive eeigrass beds in Vineyard Sound just
. outside the Waquoit Bay inlet Alternatively, eeigrass may be planted to restore
meadows, if habitat requirements have been met Restoration (planting) of habitat mat
meets eeigrass ecological requirements (light, salinity, substrate) has met with mixed
success (up to 80 percent survival but variable; Batiuk et aL, 1992).
Modd Uncertainty
The exposure-response models result in an empirical uncertainty, expressed as. the
confidence intervals of the models. Another type of uncertainty is model uncertainty, or
indeterminacy, because it is not known which loading models are correct, or even which one gives
the best estimates of nitrogen loading and its sources. In the risk assessment framework, the
confidence intervals of the eeigrass response models represent uncertainty of ecological effects,
and the indeterminacy of the loadings models represent uncertainty of exposure.
Data Uncertainty
The standard error of predicted values is'the uncertainty of .the exposure-response model
The exposure model,-in turn, has uncertainty due to uncertainty of its. input variables. The output
uncertainty can be simulated with a Monte Carlo approach and yields a distribution of the output
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variable, N loading. The N-!oading distribution is then combined with distributions ot" other input
variables to the exposure-response model and the uncertainty of the prediction to yield an overall
uncertainty of the combined model. The uncertainty can be expressed as a confidence interval or
a cumulative distribution. A predicted distribution (uncertainty) for each of the models is then
obtained. These uncertainties can be combined to yield an overall uncertainty that includes model
indeterminacy among the three or four models.
The final models and their estimated uncertainties can be used to predict the probable
consequences of specific management scenarios (e.g., effects of complete planned buildout;
effects of sewer installation in selected portions of the watershed, effects of improved septic
'systems, effects of lawn fertilizer ban). They can also be used to estimate the probability that a
management action will fail to achieve its target, and thus, how much effort is necessary to obtain,
for example, 90 percent probability of achieving the objective.
2.4J Potential Future Analysis for Other Stressors
The preliminary comparative risk analysis identified nutrient loading as the dominant
stressor in the* watershed, This risk assessment will explicitly analyze estuarine nutrient loading,
leaving freshwater nutrient loading, habitat alteration, and other stressors for future, more
comprehensive analysis. Drections this future analysis could take are discussed below.
2.4J.1 Quantitative Relative Risk
Experience with ecological risk assessment and with biological assessment has shown that
multiple stressor problems often involve stressors with vastly different magnitudes of effects. If
one or more stressors can be shown to be negligible compared to the dominant stressors, the
problem can be simplified and the risk assessment can be focused on those stressors which are
significant
This risk assessment is proceeding on the basis of the preliminary fuzzy set ranking of
stressors described above, which concluded that nitrogen loading is the principal stressor of the
estuarine component of me system. The ranking, while establishing priorities, does not permit an
overall simplification of the problem because there is no indication of the relative magnitudes of
effects. For example, is estuarine nutrient loading 10 percent more important than habitat
modification or irit 10 times more important?
Several analytical methods are available to develop multiple stressor screening. At the
simplest level, these could include extrapolation of laboratory information or extrapolation of
information from similar systems. Because it is a simple screening-type analysis, the dangers of
extrapolation are considered to be tolerable, as in the quotient method used in toxic risk
assessment The values compared (as ratios) could be the estimated loss of selected endpoints
attributable to each stressor individually.
2.4,3.2 Pond Nutrient Loading
Ashumet and Johns Ponds are subject to nutrient enrichnient (primarily phosphorus) from
ground water and nonpoint runoff.
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Objectives
• Characterize expected trophic state of Cape Cod ponds not subject to discharges,
residential septic seepage, and suburban lawn and road runoff.
• Characterize current trophic state of Ashumet and Johns ponds from ongoing MMR
studies.
• Estimate risk of further eutrophication of the ponds based on projected increases in P
loading, using a Vollenweider eutrophication model.
2.4 JJ Physical Habitat Alteration
Physical habitat alteration has the greatest potential effects on freshwater stream
components and on water dependent wildlife. Effects are well-known: removal of a habitat
results in removal of species dependent on that habitat It is generally not reversible unless the
original habitat is restored. Physical habitat alteration in the Waquoit watershed includes beach
protection, which changes the dynamics of barrier beaches; road and subdivision construction in.
nontidal wetlands: and road and development alterations of streams. Except for beach protection,
the continuing extent of habitat alteration in the Waquoit watershed is poorly known. Salt marsh
is currently protected from further encroachment by development; freshwater wetlands, less so.
Habitat of the Quashnet River has been restored, but not in the Childs River. It is not known
whether further habitat alteration will take place in these rivers.
A second component is temporary habitat disruption, with no permanent habitat loss. If
the disruption is more frequent and more severe than the ability of the system to recover, it can
become a permanent loss. Disruption is often a question of overuse, such as by mountain bikes,
off-road vehicles, or boats. The principal concern in Waquoit has been boat propellers cliroinz
eelgrass-and preventing its recovery.
Qbfecthres
• Measure the present and historical extent of suitable habitat for beach and dime nesting
'birds.
• Quantify the abundance of plovers and terns in the watershed.
* Correlate hflHfitf and bird flbfffi'dancg
Development of Habitat Loss-Response Relationship Between Avian Habitat and
Species Abundances. Habitat loss is well known to cause irreversible loss of species dependent
on the habitat for a key part of their life cycle. Birds are particularly vulnerable to loss of nesting
areas, and fish:are vulnerable to loss or degradation of spawning areas, the U.S. Fish, and
Wi(dlife Service, the National Biological Service, and the Massachusetts Audubon Society might
have information on suitable habitat for beach and dune nesting birds, estimates of past habitat
extent, and bird counts or nest counts in the area. If the information is available, it-may be
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• possible to determine trends in available habitat and nesting activity over time and in relation to
land use and population measurement endpoints.
Eelgrass Disruption. A stress-response relationship between eelgrass and boating
activity is more difficult to develop because data are more difficult to obtain and because boating
activity and nutrient loading are likely to.be collinear in the Cape Cod region. Information from
sites with high boating activity but low nutrient loading, and sites with high nutrient loading but
low boating activity will be needed. A place to look for reports might be Florida, where there are
extensive shallow regions without serious eutrophication problems, but with potentially high
boating activity (e.g., Florida Bay, parts of Tampa Bay, other Gulf Coast embayments).
Alternatively, what information would be required to answer this in the future? A simple
experiment would be to cordon off several areas from boat traffic after nitrogen management is
implemented. Eelgrass regeneration within the fenced areas but not outside would indicate that
boat traffic is significant in inhibiting eelgrass regrowth.
2.4.3.4 Other Stressors
All other stressors identified in this risk assessment ranked lower in priority in the
comparative risk analysis. The MMR toxics assessment will analyze human health risks due- to
toxic substances in the ponds, and an ecological risk analysis is still needed. For the other
stressors, too few data exist for further analysis at this time. Possible hypotheses that would be
addressed in later phases of this risk assessment include:
• Altered riverine flow. Altered flow in the streams from ground water removal,
cranberry cultivation, and storm water runoff decrease stream base flow and increases
stormflow, and increase the risk of habitat degradation for anadromous fish and
invertebrates in the streams of the watershed,
• Toxic chemicals. Toxic chemicals in ground water plumes and from lawn and
suburban stormwater runoff increase the risk of loss of freshwater and estuarine fish
and invertebrates.
• Harvest pressure. Excessive harvest pressure increases the risk of loss of commercial
and recreational fish and shellfish in the estuarine and freshwater systems of the
Waquoit Bay watershed.
* Suspended sediments. Suspended sediments, primarily from resuspension of organic
floe by boat wakes hi the estuary, increases the risk of loss of eelgrass due to
sedimentation of the floe on the eelgrass blades and increased light attenuation, and
therefore also increases the risk of loss of estuarine fish and invertebrate habitat.
A future analysis approach would be to assess the extent and magnitude of each of the
stressors, to address the question of exposure of the system to the stressors. For example, for
altered flow, this might include determining the stormflow hydrography of the most altered stream
(Child's River), and comparing it to less altered streams such as the Quashnet or other rivers.
Alteration of base flow could be addressed by analysis of USGS gauge readings. USGS might
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have determined stormilow'hydrographs for streams with a gauging station. If flow alteration is
minor, even in the most heavily altered stream, flow alteration is a negligible problem..
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3. LITERATURE CITED
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Research Reserve, National Oceanic and Atmospheric Administration and Massachusetts
Department of Environmental Management, Waquoit, MA.
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Proceedings, pp. 41-47. EPA 823-R-95-002. U.S. Environmental Protection Agency,
Office of Water, Washington, DC
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basins on the stability of a small Connecticut estuary. La Estuarine interactions, ed. MX.
Wiley, pp. 381-401. Academic Press. New York..
Wright, S3. 1987, An assessment of the biological and physical changes in the Quashnet River
caused by a stream rehabilitation project Master's Thesis, Northeastern University,
Boston, MA.
YingstJ.Y.,andQ;GRhoads. 1978. Seafloor stability in Long Island Sound: Part n
Biological interactions and their potentM importance for seafloor credibility. In Estuarine
interactions, ed, MX. Wiley, pp. 245-260. Academic Press, New York..
Zimmerman, R. C, J. L. Reguzzoni, S. Wyllie-Echeveiria» M. Josselyn, and R. S. Alberte. 1991.
Assessment of environmental suitability for growth ofZostera marina L. (eelgrass) in San
Francisco Bay. Aquat Boi 39:353-366.
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APPENDIX A
LIST OF PARTICIPANTS IN THE WAQUOIT BAY WATERSHED CASE STUDY
Waauo11 Bav Risk_Assessment WorkaroiiD
Suzanne Marcv
Patti Tyler
Maggie Geisi
David Dow
Jeroen Gerritsen
Chock Spooner
Conchi Rodriguez
Vicki Atwell
Technical Panel Chair, U.S. Environmental Protection Agency. Office of
Water
U.S. Environmental Protection Agency, Region I
Waquoit Bay National Estuarine Research Reserve
National Marine Fisheries Service, Northeast Fisheries Science Center
Tetra Tech, Inc.
U.S. Environmental Protection Agency, Office of Water
U.S. Environmental Protection Agency, Office of Prevention,
Pesticides and Toxic Substances
U.S. Environmental Protection Agency, Office of Research and
Development
Waauoit Bav Risk Assessment Contributors
Edouard Eichner
Joe Costa
Ivan Valiela
Charles CosteHo
Heidi Clarke
Tom Cambareri
Lynn Feldpausch
Jack Gentile
Chi-Ho Sham
Cape Cod Commission
Buzzards Bay National Estuary Program
Boston University
Massachusetts Department of Environmental Protection
Yale University
Cape Cod Commission
U.S. Environmental Protection Agency, Region t
U.S. Environmental Protection Agency, Office of Research and
Development
The Cadmus Group, Inc.
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APPENDIX B
NEWSPAPER ADVERTISEMENT AND ARTICLE
ON WAQUOIT BAY WATERSHEDCASE STUDY
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APPENDIX C
RESULTS OF THE WAQUOIT BAY PUBLIC MEETING
A public r'orum was held September 21. 1993 at the Waqomt Bay Yacht Club. Participants
contributed to the identification of what was valuable in the watershed (Table C-1) and to the
identification of the principal stressors that might be placing those valuable resources at risk
(Tables C-2 and C-3).
Table C-l. Environmental values/concerns that should be protected in the Waquoit Bay
watershed.
Environmental Values/Concerns That Should Be Protected
Open Space
Non-Economic Values
Historical/Political Perspective
Traditional Lifestyles
Scenic Views
Education
Indigenous Wildlife
Flyway Integrity
(migrating waterfowl)
Recreation
(swimming)
Food Resource Safety
Tourists
"Historical" Bay Ecosystem Structure
"Quality of Life"
(pleasant sensual experiences, natural
noise, smells, sights, night
sky/darkness, freedom to enjoy, visual
beauty, access to natural beauty,
wildlife, vegetation, pheasants,
skunks, clean water, clean air)
Shellfishery
Shellfishing
"Clean" Water
Shoreline
Human Serenity
.Marshland
Upland-Marsh Ecotone
"Habitat-
Recreational "Atmosphere"
Water Quality
Rushing Rates
Ak Quality
Questions on General "Health" of Existing
Ecosystem(s)-Health As Measured, (re:
only identified "active" stressor)
Washbum Island
Human Health and Domestic Animals Health
(re: lyme disease)
Habitat
Striped Bass
Navigation
Ground Water Quality
Eel Grass
Wildlife
Marine Organisms
Finfishery
Finfishing
Herring
Aquifer Integrity
.(flow rates)
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Table C-2. Types of stressors affecting the Waquoit Bay watershed.
Stressor
Dredging
Commercial Overfishing
Outside of the Bav
Commercial Trawling;
Water Withdrawal & Effect of
Gcoundwater/Surface Water
Relationship
Non-Native Species
Bacterial Population
Acid Rain
Ignorance,
Lack of Education
Nutrient Loading
— Fertilizers for Lawn, Golf
Courses and Agriculture
— Sewage Treatment, Plants
— Acid Rain
— Road Runoff
— Boats
— Livestock & Pets
—Wildlife (Waterfowl)
Boat Prop Disturbance
Shellfishing
—Raking
—Plunging
Waterfowl
Boat Wake Disturbance
Chemical
X
X
X
X
Physical
X
X
X
X
X
x
X
Biological
X
X
X
X
X
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Stressor
Overpopiuation
— Uncontrolled Growth
— Uncontrolled Access
Habitat Loss
— Loss of Ecotone Between
Marsh and Upland
— Trampling of Marsh by
Boats and People
— Unmonitored Campling
— Upland Development Resulting in
Sedimentation and Hydrologic
Changes
Lack of Values
Non-Nutrient Runoff
Man-Made Noise
Historic Fuel Dumping
— Residual Contamination within
the Atmosphere
Wet Deposition
Dry Deposition
Regional Air Transport and Patterns
Ignorant Tourists
Apathy
Fertilizers
— Insecticides
—Pesticides
Global Wanning
Sea Level Rue
Catastrophic Storms
— Nor'Easter
— Hurricanes
Boating Impacts from
Shade and Anchorage
Docks and Piers
Boat Bottom Paint. Oil and Fuel
Chemical
X
X
X
X
X
X
.•
X
Physical
X
X
X
X
X
X
X
X
X
X
Biological ' I
x :
X '•
X
X
X
X
X
X
X
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Stressor
Boat Speeding
Shoaiing>Loss of Flushing
within Bav
Building/Development
Careless Disposal of Chemicals
Uncontrolled Drainage
—•Road Runoff
— Agricultural
Lead Shot
Cresote on Pilings
Copper Arsemate on Pilings ,
Underground Storage Tanks
Lyme Disease
—Ticks. Deer. White-Footed
Mouse '(Vectors)
Lack of Management
Short-Term Economic Values
Otis Air Force Base
Willful Destruction of
Natural Resources
Lack of Enforcement
Chemical
X
X
X
X
X
X
X
X.
X
X
Physical
X
X
X
X
X
X
X
X
Biological
i
X !
X 1
X
X
X
X
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Table C-3. Waquoit Bay watershed stressors and ecological effects.
Source
Septic systems.
fertilizers.
atmospheric
deposition
Septic systems
Septic systems
Nutrient input
Nutrient input
Nutrient input
Nutrient input
Macroalgal growth
Stressor
Nitrogen
Pathogens
Fecal conforms
Shading by
macroalgae
Shading by
macroalgae
Increase in
macroalgal
growth
Increase in
macroalgal
growth
Icreased
respiration of
macroalgae
Type
Chemical
Biological
Biological
Physical
Biological
Biological
Physical
Chemical
Ecological Effects
Increase in macroaisae and
phytoplankton growth !
Introduction of pathogens and
fecal coliforms to surface
water
Shellfish bed closures
Alteration of substrate and
decrease in light attenuation
Major fauna! alterations in
benthic and fish communities
Alteration of macroalgal
• .^f
species composition
Loss of habitat for submerged
aquatic vegetation
Loss of spawning sites for fish
Loss of hiding places and
protection of fish
Loss of scallop larvae settling
habitat
Change in water coloration
Decrease of dissolved oxygen
within the water column
An increase in respiration rates
in combination with a
tempgfatme and cloud cover
increasesanoxic 'events
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Source
Macroalgal growch
Macroaigal growth
Unleashed dogs,
gulls, crows, red
fox. and eastern
coyote
Mute swan
Fertilizers and
septic systems
Marinas and piers
Gasoline, motor oil.
Automobile and
boat engines'
' Massachusetts
Military
Reservation
(Otis Air Force
Base)
Stressor
Increased
respiration of
macroalaae
Competition by
macroalgae
Wild predators
Introduction of
exotic species. '
Phosphorus
Antifouling
chemical
leachate
Organic
compounds
acetone,
benzene,
naphthalene,
petroleum
hydrocarbons.
polychlorinated
biphenylsand
creosote
*Methyleoe
chloride, cw 1,2'
dichloroemy-
lene.U,K .
trichloroethane,
trichloroethy-
lene, perchloro-
ethane, 1,2-
DBA, toluene,
etfaylbenzene,
xylene in Sergou
Phase I Held GC
Screening Data
Type
Biological
Biological
Physical and
biological
Biological .
Chemical
Chemical
Chemical
Chemical
Ecological Effects
Mortality within benthic
invertebrate and fish
populations
Loss of eelgrass habitat
Disturbing nesting areas for
two endangered
species — piping plover and
least tern and the threatened
roseate tern
Displacing native waterfowl
species
Negative biological effects on
organisms in contact with it
7
?
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Source
Massachusetts
Military
Reservation
(Otis Air Force
Base)
Lawns, golf
courses/cranberry
bogs
Road deicing salt
- Landfill leachates
?
Stressor
DCE. TCE.
PCE. in Ashumet
Valley
Groundwater
Plume
Need
information
Need
information
Unrecorded
dump sites (need
more
information)
Metal*—
arsenic.
cadmium.
chromium.
copper, lead.
mercury.
molybdenum.
nickel, silver.
zinc
Hurricanes or
severe storms
Type
Chemical
Chemical
Chemical
Chemical
.
Chemical
Physical
. Ecological Effects
••>
7
Phytotoxicity, leaf fall
•
7
Looking into obtaining
information: from the EMAP
program
Flooding of upper estuary
-
Shoreline erosion
Altered tidal regime
Increase volume of water input
Sediment resuscension
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Source
Commercial
shellfishing
Construction
development
Otis Air Force Base
Global climate
change
Stressor
Seawalls and
jetties.
Boat propellers
Polar outbreaks
Raking and
plunging for
scallops
Filling wetlands
Thermonuclear
explosion
Sea level rise and
increase in
turbidity and
sediment loading
Type
Physical
Physical
Physical-
Physical
Physical
Physical
Physical
Ecological Effects
Major alteration of shoreline
dynamics
Sediment resuspension
Coastal erosion
Sediment buildup
Change in flushing rates
Rip-up vegetation
Sediment resuspension
Increased turbulence and
mixing in water column
Freezing of bay
Disturbing sediment
Resuspending nutrients
Increasing turbidity
Loss of marsh-uplands ecotone
Increase surface water runoff
(activities such as paving to
lead to an increase in surface
water runoff temperature)
Increase sediment loading
Alter groundwater flow
Intense heat and the end of life
as we know it
Flooding
' Alteration on coastline
increase in turbidity and
sediment loading
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Source
Stressor
Dredging
channels
Type
Physical
Ecological Effects
Sediment disturbance and !
increase in turbiditv
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APPENDIX D
WAQUOIT BAY MANAGEMENT GOALS MEETING
Attendees
Tom Cambareri
Bruce Carlisle
Joe Costa
David Dow
Perry Hlis
Tom Fudala
Jetpen Gerritsen
Steve Hurley
Chuck Lawrence
Sandy McLean
CariMelberg
Jo Ann Muramoto
MarkPatton
Pam Polloni
Bob Shennan
Jan Smith
Pani Tyler
Mary Varteresian
Brooks Wood
Rick York
Cape Cod Commission
Massachusetts Coastal Zone Management
Buzzards Bay National Estuary Program
National Marine Fisheries Service, Northeast Fisheries Science Center
Mashpee Harbor Master
Mashpee Planning Department
Tetra Tech, Inc.
Massachusetts Division of Fisheries and Wildlife
Cape Cod Commission
Citizens for the Protection of Waquoit Bay
U.S. Fish and Wildlife Service
Falmouth Conservation Commission
Otis Installation Restoration Program
League of Women Voters, Falmouth
Mashpee Conservation Commission.
Massachusetts. Coastal Zone Management
U.S. Environmental Protection Agency, Region 1
U.S. Fish and Wildlife Service
Monomoscoy Improvement Trust
Mashpee Shellfish Department
Concern
Ashumet - John's Pond Association
Ashumet Valley Property Owner's Association, Inc.
Association for the Preservation of Cape Cod
Atlantic States Marine Fisheries Commission
Bamstable County Department of Health and Environment
Cape and Islands- Coastal.Waters Steering Committee
Cape and Islands Self Reliance Corporation
Cape Cod Beagle Club
Cape Cod Commission (CCQ
Cape Cod Cooperative Extension Service
Citizens for the Protection of Waquoit Bay
Da vis ville Association
F. A. C. E. S.
Falmouth Rod and Gun Club
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WaqiiQJt Qay Concerned Organizations. Continued
Falmouth Condo Trast
Green Briar Nature Center
Mashpee Briarwood Association, Inc.
Massachusetts Audubon Society
Massachusetts Coastal Zone Management (CZM)
Massachusetts Department of Environmental Management (MADEM)
Massachusetts Department of Environmental Protection (MAOEP)
Massachusetts Department of Fisheries, Wildlife, and Environmental Law Enforcement
Massachusetts Heritage Society
Massachusetts Military Reservation (MMR)
Menauhant Harbor Association
National Oceanographic and Atmospheric Administration (NOAA) National Estuarine Research
Reserve System (NERRS)
NOAA National Marine Fisheries Service (NMFS)
National Science Foundation (NSF) Land Margin Ecosystems Research (LMER)
The Nature Conservancy
Seacoast Shores Owners Association
Shorewood Beach Owners
Sierra Club
South Cape Beach Advocates
The 300 Committee, Inc.
Town of Falmouth
Town of Mashpee
Town of Sandwich
Trout Unlimited
U.S. Army Corps of Engineers (COE).
U.S. Department of Agriculture (USDA) Soil Conservation Service (SCS)
U.S. Fish and Wildlife Service (USFWS)
U.S: Geological Survey
Wampanoag Tribal Council
Waquoit Bay National Estuarine Research Reserve (WBNERR)
Waquoit Bay Watershed Citizens Action Committee (formed of representatives of other groups)
Waquoit Bay Watershed Intermunicipal Committee
Waquoit Bay Yacht Club
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APPENDIX E
ASSESSMENT OF AVAILABLE INFORMATION
A summary of the assessment of available information was provided in Section 2.1 of the
Waquoit Bay Problem Formulation. The following material describes in more detail ihe
ecosystems at risk, reviews ecological effects that have been observed in the watershed, and
provides a preliminary characterization of stressors in the Waquoit Bay watershed based on
studies conducted in the watershed and elsewhere.
E.1 CHARACTERIZATION OF THE ECOSYSTEMS AT RISK
• ,
The Waquoit Bay watershed covers approximately 53 square kilometers (21 square miles)
and spans parts of the towns of Falmouth. Mashpee, and Sandwich on the south coast of Cape
Cod. Massachusetts. The watershed was first delineated by Babione (1990) and further refined by
Cambareri et al. (1992). Recent work by Brawley and Sham (in prep.) reinterpreted the
watershed delineation of Cambareri et al. (1992) to develop a three-dimensional model of the
drainage basin. The watershed covers 8 km (5 mi) from the head of the Bay to the regional
ground water divide in the vicinity of Snake Pond (Figure E-l). The Bay and its tributaries
encompass a total surface water area of 3.9 km2/389 ha (1.5 mi2). The major surface water
components of the watershed include the Waquoit estuary»two major rivers and several smaller
streams, freshwater ponds, and freshwater wetlands. Within the Waquoit Bay watershed are •
seven subwatersheds (Childs River, Sage Lot Pond, Quashnet River, Eel Pond, Head of the Bay,
Hamblin Pond, and Jehu Pond) and four ponds (Ashumet, Johns, Snake, and Flat). These
subwatersheds provide diverse habitats that support a variety of ecological communities, including
barrier beaches along the Atlantic Ocean, eelgrass beds, saltwater and freshwater marshes, erosion
and accretion areas, coastal sand dunes, brackish water ponds, fish spawning and nursery areas,
and wildlife habitat
E.1.1 Watershed-wide Characteristics
The Waquoit Bay watershed lies entirely within the Mashpee pitted outwash plain
(LeBlanc et aL, 1986), a geologically young landfonn composed of glacial materials deposited on
top of bedrock toward the end of the Wisconsinian Glacial Stage, about 12,000 years before
present (Oldate, 1992). Outwash plains were created by broad meltwater streams which size-
sorted the drift materials depositing the heavier boulders and pebbles near the glacial margin and
gravel and sands further away. Because Cape Cod is so young geologically, the glacial materials
have not been significantly altered, resulting in a generally sandy, porous soil throughout the area.
In addition to gravel and sand, there are clay and silt lenses; this finer grained material generally is
found in deeper sediments to the south.
The term "pitted "refers to the numerous kettle ponds dotting me landscape. Kettle ponds
mark the sites where blocks of ice were buried by sediment-laden meltwater streams beyond the
glacial margin. Johns Pond and Ashumet Pond are two examples of kettle ponds in the watershed
(HAZWRAP, 1995). Waquoit Bay, itself, may have originated as a kettle pond. The southern
margin of the bay was flooded by sea-level rise at the close of the Wisconsinan Glacial Stage,
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Subwatersbeds
1- Eel Pond
2-Childs River
3-QuashnetRxver
4 -Head of 4e Bay
5-HambliaPoixl
6-JchnPond
7 -Sage Lot Pood
A-AsttometPond
o * JOfiuS
C - Snake Pood
D'FIatPoaf
Figure E-l. Waquoit Bay watershed and subwatersheds (Banyley ad Sham, in prep.).
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when-the iee sheet'recreated, inundating low lying coastal areas and raising the water table inland
due to hydrostatic pressure at the saltwater-fresh water interface. The action of winds, waves and
currents continually eroded and displaced the loose glacial sand and gravel contributing to the
formation of coastal sand dunes, sea cliffs, barrier beaches and salt marshes. These processes
continue to alter the dynamic shore (Oldale. 1992).
Waquoit Bay's geology controls the region s hydrology, which is typical of a glacial
outwash plain. The Bay, 1.2 km (4,000 ft) wide and 3.4 km (11.000 ft) long, is a shallow estuary.
average depth of 0.9 m (3 ft), fed by freshwater streams and ground water with tidal exchange to
Vineyard Sound through two dredged and maintained channels, and a recent breach caused by
overwash during Hurricane Bob in August 1991 (Valiela et al., 1996). Fifty percent of the water
entering Waquoit Bay comes from the Quashnet and Quids Rivers, 23 percent from direct
precipitation, and 27 percent from ground water recharge in the watershed. Ground water in the
Cape Cod region is generally formed by precipitation. Ground water recharges the area upgrade
from the ponds and discharges from the downgradient portions of the ponds (Cambareri et al.,
1992). The rivers derive most of their water from ground water discharge, draining the shallow
surface aquifer. Ground water is forced to the surface as the permeable aquifer thins from north
to south in the watershed.
The unconsolidated sediments of Cape Cod make ideal aquifers-underground areas that
contain enough water to supply significant amounts of water for community use. The permeable
aquifer ranges from about 46 ra (150 feet) thick near Snake Pond, thinning to 9m (30 feet) near
Waquoit Bay (Garabedian et al., 1991; Cambareri et al., 1992). The porous soils support rapid
percolation of rain, nutrients, and contaminants into the subsoil and eventually to the ground
water. In recognition of the unique ground water characteristics of Cape Cod, the U.S.
Environmental Protection Agency declared this region a Sole-Source Aquifer in 1982, a
designation designed to facilitate protection of the water supply. In actuality, the Cape Cod
aquifer can be subdivided into six ground water "lenses'* or areas of elevated ground water;
surface features, such as rivers, separate the lenses and generally ground water does not flow
between lenses. The Waquoit Bay watershed lies within the Sagamore or western Cape lens of
the Cape Cod Aquifer (Guswa and LeBlanc, 1981).
The watershed's hydrology and habitats are influenced by its climate, which is similar to
that of other areas in the northeastern United States but typically has milder winters and cooler
summers due to surrounding ocean waters. January and February are the coldest months and July
and August are the wannestmonths. Fog may be common in the spring and summer and
humidity is typically high in the summer. Annual precipitation is between 107 and 112 cm (42 and
44 inches), ground water recharge is approximately 45 percent of the total precipitation. Snowfall
is variable from one year to the next but is close to 76 cm (30 inches) per year. Between October
and April the prevailing winds are northwest whereas from May to September winds come from
the southwest Hurricanes are most common in the late summer and early fall and "northeasters"
may occur in winter and early spring.
The surface water ecosystems in the lowlands and uplands of the Waquoit Bay watershed
contain several critical habitats identified by the* Association for the Preservation of Cape Cod
(VanLuven, 1991), including coastal plain pond shores, anadromous fish runs, salt marshes, *'
eelgrass, barrier beaches, and woodlands. Habitats hi the watershed are also affected by the
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southward-flowing cold Gulf of Maine waters and the northward-flowing warm Gulf Stream.
which mix off the coast of Cape Cod to form a biological transition zone between the Virginian
(temperate) and Acadian (boreal) biogeographic provinces (Ayvazian et al., 1992). This overlap
produces more diverse communities than occur in either province. The Waquoit Bay watershed
also lies near the Atlantic coast flyway, an important migratory corridor for many coastal and
arcttc-nesring birds, particularly shorebirds. as well as state and federally protected species. The
flora of the watershed include scrub oak and pitch pine forests (Bailey, 1995); forests covered
26SO ha (6S48 acres) of the watershed in 1990 (Appendix F). Among the state protected plant
species found in the watershed are the sandplain geratdia. Agalinis actua (endangered); the bushy
rockrose, Helianthuemum dumosum (threatened); the knotroot foxtail, Setaria genicidata (of
special concern); and the butterfly-weed, AscUplas tuberose, little ladies' tresses, Spiranthes
tuberosa, eastern lilaeopsis, LUaeopsis chintnsis. New England blazing star, Uatris borealis,
thread-leaved sundew, Droserafiliformis, vetchling, Lathyrus palustris, and wild rice/Zfczma
aquatic*, (on the watch list) (WBNERR, 1993). The following subsections describe in more
detail the physical characteristics and biota of each of the four major surface water components of
the watershed.
E.1.2 Waquoit Estuary
.Waquoit Bay is located at the southern margin of die watershed, protected from Vineyard
Sound by a barrier beach east of the main inlet to the Bay, South Cape Beach, and Washbum
Island, a barrier island to the west of the inlet (WBNERR, 1989). Water from the Sound enters
the Bay through two channels and the overwash breach mentioned above. Several brackish water
ponds (Sage Lot, Jehu, Hambtin, and Eel) connect to the Bay, Waquoit Bay is relatively shallow
and salt marshes occur hi some areas along the margins of the coastal poods and tributaries
(according to aerial interpretations of land use); saltwater wetlands covered 129 ha (319 acres) in
1990 (Cape Cod Commission, unpublished; Appendix F). Bottom habitats include areas of open
sand and mud, as well as patches of eelgrass.
Eelgrass (Zostera marina) is a rooted vascular plant that grows subtidally on mud to
gravel bottoms in zones of fast moving or quiet waters where salinity ranges between 20 and 32
parts per thousand. Eelgrass roots and rhizomes are believed to decrease erosion and increase
sedimentation, and eelgrass blades may act to promote deposition by interrupting water flow and
trapping suspended sediments, thus, adding to the available food within the meadow (Short, 1984;
1989). Eelgrass is highly susceptible to adverse changes in water quality conditions and requires
clear waters with ample light penetration for photosynthesis and suitable levels of nitrogen and
phosphorus nutrients (reviewed in Dennisbn* 1987; Zimmerman et aL. 1991; Murray et ah, 1992;
Dennison et aL, 1993; Submerged Aquatic Vegetation Work Group. 1995). Eelgrass provides
optimum physical and chemical environmental conditions ma protective habitat for many fishes
and invertebrates (Valiela et al., 1992; Heck et aL, 1989; Thayer et aL, 1989). A variety of
bryozoans, sponges, and hydroids attach to eelgrass blades; numerous juvenile ftnfish,
crustaceans, and shellfish inhabit eelgrass meadows. Decaying eelgrass leaves provide food for
the detritivores hi the benthic community as well.. Greater species richness and abundance has
been found hi eelgrass beds than in adjacent unvegetated areas hi Waquoit Bay and Nauset Marsh
on Cape* Cod (Valiela et aL, 1992; Keck et aL, 1989).
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The overlapping biogeographic ranges are evident in the waters of the estuary, with both
year-round residents and seasonal migrants in the finfish communities of Waquoit Bay. A 1968
survey reported that Waquoit Bay had the greatest diversity of finfish species in comparison to'
nine other Massachusetts estuaries (Curley et al., 1971). The resident species include such
species as mummichug (Fundulus heteroditus), striped killifish (Fundulus majalis), tidewater
Mlverside (Menidia beryllina), fourspine stickleback (Apeltes quadracus), and rainwater kitlifish
(Lucania parva), Of the 52 species collected in Waquoit Bay, these resident species comprise 35
percent of the total, with these species dominating the abundance (46 percent) and biomass (4 1
percent) of the overall finfish community (Ayvazian et al., 1992). Table E-l contains a list of
fishes found in the Waquoit Bay watershed
The part-time residents represent a composite of estuarine spawncrs such as winter
flounder (Pseudopleuronectes americanus), longhom sculpin (Myoxocephalus
octodecemspinosus), scup (Stenotomus chrysops), and tautog (Tautoga onitis); marine species
which are estuarine visitors, such as the sand lance (Amodytes americanus), summer flounder
(Paraiichtnys dentatta), and American pollack (Pollackius virens); nursery species or
young-of-the-year, such as winter flounder juveniles^ mullets (MugUcephaau), juvenile tautogs,
menhaden (Brevoortia tyrannys), Atlantic silversides (Menidia menidia), bluefish (Pomatomus
saltatrix), and bay anchovy (Anchoa mitchilli); and adventitious species which have a more
southern distributions but which lack an apparent estuarine dependence, such as ladyflsh (flops
saurus), hallbeak (Hemiramphus bmsiUensis), and crevalle jack (Caranx hippos). Alewives
(Alosa 'pseudoharengus) and biueback herring (Alosa aestvalis) cross Waquoit Bay on their
annual spawning migrations to fresh water, and larger fish such as bluefish and striped bass
(Morone saxitaUs) enter in pursuit of smaller prey fish. Many primarily marine fishes use the
estuary in the winter as a spawning and nursery ground. Bluefish, tomcod (Microgadus tomcod),
white hake (Urophycis tenuis), and pollock inhabit me bay as juveniles but are rarely present as
adults (Boesch and Turner, 1984).
Shellfish species harvested in die estuary include bay scallops (Argopecten uradians
irradians), found in the eelgrass habitat, and hardshell (Mercenaria mercenaria) and softsheil
(Mya arenaria) clams, generally found in the sand and mud habitats, respectively. The biota of
the. estuary also includes a variety of temperate and boreal species of planktonic and benthic algae
and invertebrates, providing food resources for the finfish and shellfish, as well as terrestrial and
avian wildlife in the watershed.
Numerous' shorebirds use the barrier beach and coastal saltmarsh as an important stopover
on their spring journeys north to breeding grounds in Canada and on their fall journeys south to
the southern United States, Central and South America. Shorebirds appearing in abundance in the
spring and fait on Waquoit Bay's barrier beaches include black-bellied (Squatarola squatarola)
and semipalmated (Charadrius semipalmatus) plovers; sanderiings (Crocethia alba); dunlin
(Calidris aipina); semipalmated (Ereunetes pusitlus), least (PisobiafiuicoUu), and western
sandpipers (Pisobia mmutillay, ruddy tumstones (Arenaria interpres); willets (Catoptrophona
semipaimatus); lesser (Totanusflavipes) and greater (Tetanus melanoleucus) yellowlegs; and
Sharp-tailed sparrows (Ammodramits
cudacutus), brack-crowned night-herons (Nycticorax nycricorax), snowy egrets (Leucophoyx
thuia), and mute swans (Cygnus olor) are found in the saltmarshes. Several species of buds that
use the waters as nesting or feeding grounds are state and federally protected species.
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Table E-l. Fishes of the Waquoit Bay Watershed
Genus/ Species- •
Common Name
Reference
Genus/Species
Common Name--
Reference-
Estoarine Residents
Opsanus lau
Funduius
heteroditus
Funduius majalis
Cyprinodon
variegaau
Lucaniaparva
Menidia berylUna
Menidia peninsula*
Pungitiio pungiliuf
Apeltes quadracus
oyster toadtlsh
mummichog
striped kiliifish
rainwater Itillifish
inland silverside
tidewater silverside
nlnespiae
stickleback •
i OttZSOlQC tXCiuCO&dC
Clupea hartngus
Brevoortia rynuuuu
AnchoamiteheUt
Microgadus tomcod
Strongylura marina
Menidia menidia
Atlantic herring
Atlantk menhadea
bayancoovy
A^«|^ir nocdl'tfiMv
Atlantic silvenide
A,C
A.CH
A.C
A.C
A,C
A
C
A.C
A.CH
Gasterosteus
acuUaaa
Casurosteus
.wheatlandi
Syngnaduafuscus
Menticirrhus
f/rmff[ff
Gabioscmabosd
Pkolis gunntiba
Myojoxephalus
aenaeus
Truucus masculaau
Sphotroidts
maculatm '
A
A.C
A
A.C
A.C
A.C
Pomatouuu saluinx
Tautogaonais
Tautogoutlma
adsptnta .
Mugil cephalus
PnudoiflfunHuctfs
Umphycistatuis
pjadfOOOQi (•nadromoui and calnlitmiii
Aag uilla rostntta
Alosa aestivalu
Alosa.
pseudoharengus
American ee4
blueback herring
aliewife
A.CH
A.C
A.C
At*t9M r/fiMu^rvWma
nivuu ju/niiijj»i«
Asmtna mordax
threespine
stickleback
blackspotted
stickleback
northern pipefish (in
eelgrass)
northern kingfish
naked goby
rock gunnel
sn*y . -
bogcboker
Dorthern puffer
A,C
A.C
A.C
- A.C
A
A.C
A,C
A.C
A.C
.
btucfisb
taotog .'
dinner
MrhMrfmnlla*
4U1JIT1J UMIIGI
winter flounder
white hito
Arntriciui shad
• L.
rainbow smeu
A.C
A.C
A.C
A.C
A.C
C
A
C
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Genus/ Species^
Common Name
Reference-
Genus/Speciesr - ~"
•^.. ..-^- _...
'Lxth'uuuirlXailiai-
References-
Marine, Seasonal Visitors as Adults
Anchoa hepsetus
Poilachtus virens
Morone saxarilis
Centropristis striata
Stenotomus
chrysops ,
Mugil curema
Ammodytes.
americanuf
Fwtdulus
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The piping plover (Charadrius melodus), listed as threatened; and the least tem (Sterna
antillarum), listed as being of special concern, nest on South Gape Beach and Washbum Island.
The roseate tern (Sterna dougaLli), a species listed as endangered, forages in the water and rests
on the beach proper (WBNERR. 1993; 1995).
E.I.3 Coastal Plain Rivers
Coastal plain rivers also provide an important source of water for upland species and are
prime habitat for fishes, turtles, ducks, and geese. Forests of scrub oak and pitch, pine are
frequently encountered in the surrounding soils, which are mostly consolidated sand dunes. The
largest and cleanest contributor of fresh water to Waquoit Bay is the Quashnet River (also called
the Moonakis River in Falmouth), which had an average streamflow of 391 L/sec (13.S cubic
ft/sec) or 8.9 million gallons per day from 1988 to 1991 (Barlow and Hess, 1993). The Quashnet
originates in a spring-fed cedar swamp at the top of John's Pond. Outflow from Johns Pond to
the Quashnet can be regulated by a gate-controlled spillway. From the pond, the river enters
cranberry bogs, flows east for 0.6 km (0.4 mi) then flows south for 5.6 km (3.5 miles) (Baevsky,
1991). finally emptying into Waquoit Bay.
Besides providing a source of fresh water to Waquoit Bay, the Quids and Quashnet
Rivers provide a relatively rare and shrinking habitat for several anadromous and catadromous
finfish species (Baevsky, 1991). Brown trout (Salmo tnata), brook trout (Safvelinusfontaudis),
alewtfe (Alosa aestivalis), white perch (Morone americana) use these rivers as a conduit for
spawning grounds either within the rivets themselves or within John's Pond (McLamey, 1988;
S.T. Hurley, 1994, Massachusetts Divsion of Fisheries and Wildlife, pen. coram.). American eels
(Anguilla rostrata) use these riven as a conduit for spawning grounds in the open sea. These
species require very specific ranges of certain water quality parameters (temperature, pH,
dissolved oxygen, salinity) which may vary over the stages of egg, larval and juvenile development
(Hunter, 1991). Under the care of the Northeast Chapter of Trout Unlimited, ecological integrity
and stability in die Quashnet have recently improved significantly. The river now hosts a 1.6 km-
(1 mi-) long trout spawning reach 3.5 to 53 km (22 to 33 mi) downstream from the spillway.
The'upper Quashnet River receives constant temperature groundwater discharge through the sand
and gravel bottom (USGS, 1991), which keeps river temperatures moderate, from 10 °C to 17.9
°C (50 °F to 64 °F) in the spawning reach (Baevsky, 1991). Blueback herring, striped bass, and
white sucker (Cata&cmus commersonilaK also commonly found in this stream.
The characteristics of the high volume of ground water inputs into the Quashnet River
significantly influence the water quality parameters of the river. At present, the waters seeping
into the Quashnet ate fairly pristine, with a dissolved oxygen content of 93 to 12.6 mg/L, (well
above die minimum requirements for the most sensitive brook trout),.pH between 6.0 and 6.4
(coo low for the Class B requirements), and a nearly constant temperature of 14 °C (57 °F)
resulting from groundwater seepage (Baevsky, 1991). For example, the temperature remained
between 10 °C and 17.9 °C (50 °F and 64 °F) in the spawning reach during 1988 (Baevsky-.
1.991). In that same year, the temperature entering the river from John's Pond was 263 "C (79
°F). The inputs from ground water are also crucial to mainnwiif»g sufficient volume in the river
for fish to move upstream.
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The good water quality of the Quashnet River also provides habitat for a variety of
macroinvertebrates which serve as a food source for the finfish communities (Pennak, 1989). As
part of Trout Unlimited's restoration project, macroinvertebrate species were reintroduced to the
Quashnet from other freshwater streams. A survey done in 1982-1983 found species representing
the Trichoptera (caddisfly), Diptera(true flies), Lepidoptera (butterflies and moths),
Ephemeroptera (mayflies), and Plecoptera (stoneflies) orders (Wright. 1987). Stoneflies. and tc
some extent mayflies and caddisflies, are good indicators of healthy water quality as they require
fairly high levels of dissolved oxygen.
E.1.4 Freshwater Ponds
Ashumet Pond and Johns Pond are coastal plain kettle hole ponds located within the
Waquoit Bay watershed, north of the bay itself. There are no surface outlets discharging from
Ashumet Pond. Ground water recharge occurs in the upgradient area and the pond recharges the
ground water on the downgradient side of the aquifer. Johns Pond connects to the Quashnet
River by a surface outlet at a gate-controlled spillway. This spillway can draw down die level of
Johns Pond to 1.2 m (4 ft) below it average elevation. Ashumet Pond covers 82 ha (203 acres).
with an average depth of 7 m (23 ft) and maximum of depth'of 20 m (66 ft); Johns Pond covers
131 ha (324 acres), with an average depth of 5.9 m (19 ft) and maximum depth of 19 m (62 ft)
(Duerring and Rojko, 1984a; I984b).
Fish populations including largemouth (Micropterus sabnoides) and smailmouth .
(Micropterus dolomeiui) bass, trout, and brown, bullhead catfish (Ameiurus nebulosus) reside
within Ashumet Pond and similar fishes have been recorded in Johns Pond. Freshwater mussels
are also abundant in the ponds. A high diversity of phytoplankton is present in the.photic zone.
but limited vegetative growth on the shorelines has been documented (HAZWRAP. 1994,1995).
Within the vicinity of the ponds, several species have been designated as having special concern or
threatened status, including the sandplain flax, the marsh hawk; and the grasshopper sparrow.
The upland sandpiper is listed as a state endangered species.
E.1.5 Fresh water Wedands
The freshwater wetlands of the Waquoit Bay watershed covered approximately 83
hectares in 1990 (Appendix F) and support many wetland plant and animal species. Important
freshwater wetlands include the Ashumet and Johns Ponds shorelines. Waterfowl are dependent
upon these wetlands for breeding, foraging and migratory needs. These habitats provide a
valuable refuge for many types of wildlife, including the osprey (Pandion hdtitutus) which forages
for fish hi freshwater areas.. Many upland wildlife species are seasonally dependent on wetlands,
including song and game birds, opossum (Dtdelphis virginiana), raccoon (frocyon lotor lotor),
and white-tailed deer (Odocoiletu virginianus).
EJ, ECOLOGICAL EFFECTS
The wafers of Waquoit Bay and associated freshwater ponds are exhibiting signs of water
quality degradation and the diversity and abundances of key aquatic species have changed, notably
during the last 30 years. In the Bay, increased phytoplankton populations have decreased water
clarity and the amount of light penetrating the water. Extensive mats of macroalgae consisting
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mainly of the species Cladophora vagabunda and Gracilaria tikvahiae, which was unknown in
the bay in 1969 (Curley et al.. 1971), cover most of the bay (Valiela et ai., 1992). The extent of
eeigrass habitat has declined, from approximately 81 ha (200 acres) in 1950 to only 16 ha (40
acres) in 1987 (Costa et al., 1992). EeJgrass is now restricted to fragmented beds near the mouth
of the bay and the tidal inlet near the mouth of the Eel River adjacent to Washburn Island, to the
small salt pond and salt marshes of Washbum Island, and to small patches in Hamblin Pond, Jehu
Pond, and Sage Lot Pond (Figures E-2 and E-3) (Short et al.. 1993). Physical destruction of
eeigrass and sal tmarsh has also occurred.
Water clarity has also been reduced by increased sediment particulates released into the
Bay, rivers, and ponds. Settling of unconsolidated particulates has adversely affected nursery and
spawning habitats for fishes, as well as benthic invertebrate communities.
Alterations in the composition of species dependent on the eeigrass for nursery or adult
habitat have occurred, with declining abundance of commercially important finfish, such as
flounder, pollack, and hate, and shellfish, particularly the scallops. In July 1987,1988, and 1990.
fish kills occurred in Waquoit Bay and the northern beach was covered with thousands of dead
'winter flounder, shrimp, blue crabs, and other estuarine species (Sloan. 1992; EXAvanzo and
Kremer, 1994). Anoxic conditions in the Quashnet could constitute a barrier to sea-run brook
trout (McLamey, 1988). Phytoplankton blooms in Ashumet and Johns Ponds have changed the
color of the water and depleted oxygen levels in' the hypolimnion of the pond; fish kills occurred
in Ashumet Pond in July 1985 and May 1986 (HAZWRAP, 1995). .
Recent changes and reductions in stream flow have affected netting runs and trout streams
(Bariow and Hess, 1993). These species require certain quantities and depths of water; for
example, alewives that must travel to Johns Pond to spawn need sufficient water
depth to traverse the bogs near the pond and years of low water table levels or reduced flow have
limited their success.
E3 SOURCES AND STRESSORS
Seven physical, chemical, and biological stressors in the Waquoit Bay watershed were
•identified during discussions with the risk management team and the public. The sources of
stressors include human activities within and outside of the watershed. Each stressor was
characterized on the basis of its type, mode of action, and general ecological effects that might
result from exposure to the stressor. In addition, information on the intensity, frequency;
duration, timing, and spatial heterogeneity and extent (scale) were reviewed for each stressor in
the watershed, if available. The susceptibility of the ecosystems to the stressors was also
examined.
EJ.1 Sources of Stressors
Anthropogenic stressors in the Waquoit Bay watershed, are the result of changing land use
patterns along the coastal and upland areas (Appendix F). Land use maps produced by the Cape
Cod Commission and by die LMER group identify land use with respect to commercial, cleared
land and recreation, residential, agricultural, forest, wetland, mining, -waste disposal and
transportation. These maps also depict chaneinff land use oatterns with time. For example, in
F-9.76
-------
_/?
Pond CLy/
u
m
I
' to
$
o
O
o
nl
O
30
O
o
m
Figure E*2. Coastal area of Falmouth and Mushpcc, Massachusetts, showing eelgrass beds
(hutched areas) in Waquoit Bay, neighboring embayments, and Vineyard Sound, summer 1994
(M.Morton, Tetra Tech, Inc.).
-------
4VT 00
41 45
41 30
41 15
41 41)
33
2
o
I
o
o
I
o
o
31
o
o
n!
71 00
70 45
Figure E-3. Martha's Vineyard,, Nantucket, and south coast of Cape Cod, showing eelgrass beds
jh 1994 (heavy lines). Eelgrass beds shown only from Woods Hole 10 Pleasant Day and on the
north coasts of Martha's Vineyard and Naniucket islands (M. Morton, TetraJ^cli, Inc.).
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1950 2% of the watershed was residential; in 1990 20% was considered residential (Sham et al..
1995). Land use in the watershed is primarily residential, particularly along the Childs River
(McDonnell et al., 1994). In 1938.785 houses had been built in the watershed, but more than
8000 residences were counted in the watershed by 1984. Around Waquoit Bay alone the human
population has increased approximately fifteen-fold in the past 50 years, from 400 houses in 1950
to over 4000 houses in 1990 (Sham et al.. 1995). More than 3000 additional single-family homes
could be constructed in the watershed (Waquoit Bay Watershed Citizen Action Committee.
1992).
Cranberry bogs, the major agricultural land use, have declined over the past century: today
there are less than 350 acres of bogs. Cranberry bogs, golf courses and cropland comprise 1.2
percent, 1.2 percent, and 2.0 percent of land use, respectively, in the watershed (Appendix F).
The Massachusetts Military Reservation (MMR) in the northern portion of the watershed (Figure
E-4) is of special concern due to the contaminant plumes emanating from ten separate point
sources; this installation is the closest to an industrial or commercial land use classification in the
watershed (HAZWRAP. 1995).
Although the Quashnet River has been recognized by some as an extremely valuable
resource, development pressure continues to build in the surrounding towns of Mashpee and
Falmouth and with it the search for additional sources of drinking water. To restrict one
proposed housing development, the Commonwealth of Massachusetts purchased 146 ha (361
acres) of land along the river, thereby limiting this housing development to 185 units without river
frontage (Baevsky, 1991). Ashumet and Johns Ponds also face potential susceptibility to
development pressure. The watershed is particularly susceptible to buildup of nutrients and
chemical pollutants because of the porous soils of the watershed and the limited flushing of waters
from the ponds and the Bay (from a few months to over 30 years). Development in the watershed
has also increased human activities in and on the surface waters, particularly in the ponds and bay.
Stressors associated with atmospheric deposition might also contribute to those already present
from the various land and marine uses.
Residential Development. Activities in the watershed associated with residential land
usejthat might add to nutrient-loading within the ecosystem include on-site septic systems;
fertilizer use on lawns, golf courses, and gardens; and housing and road construction with the
attendant increase of impervious surfaces (Valiela and Costa, 1988). Each of the 8000 homes in
the watershed has an on-site wastewater disposal (septic) system that contributes nitrogen to
ground water which travels to Waquoit Bay. Wastewater is a larger contributor of nitrogen to the
estuary man is atmospheric deposition or fertilizers (Valiela et at, 1996). Fertilizer inputs to
Waquoit Bay are primarily from residential lawn applications. Shellfish beds are frequently closed
at the mouth of the Quashnet River to protect consumers from potential exposure to human
pathogens that are not trapped by septic systems or soil and reach the bay. Pesticide applications
on golf courses, cranberry bogs, and lawns add toxic chemicals. Private and municipal well
development alters ground water flow regimes. Housing and road construction also are sources
of sediments as construction uproots vegetation and toads and driveways increase impervious
surf ace cover. Oil hydrocarbons and other chemicals can accumulate on impervious surfaces like
parking lots and roads and be washed off by rain to enter ground and surface waters.
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— —MUNICIPAL BOUNDARY
— — MM BOUNDARY
CAi*» EDWARDS - AIMC
OTIS - ANC
USCG
VTTEflANS AOUIN
USAF
NTS
12-9-S4
IAAH377.DGN
Figure E-4. Location of the Massachusetts Military Reservation. North of Johns and Ashuraet
Ponds (HAZWRAP, 1995).
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Industrial Uses. MMR. composed of Camp Edwards and Otis Air Base, is located on the
upper western'portion of Cape Cod and covers 8903 ha (22,000 acres). Past industrial and
military activities at MMR have mobilized chlorinated solvents and fuel constituents forming
plumes of contaminated ground water. MMR was added to the National Priorities List (NPL) on
November 21, 1989 (HAZWRAP, 1995). Sewage treatment facilities at MMR and increased
runoff from impervious surfaces add nutrients: well development might have altered ground water
flow (Barlow and Hess, 1993). Ashumet Pond is receiving its greatest input of phosphorous from
the MMR sewage treatment plant (STP). If phosphorous levels continue to remain as predicted
over the next ten years, Ashumet Pond will become eutrophic. Freshwater ponds could also be
affected by other contaminants associated with MMR (HAZWRAP, 1995).
Agricultural Activities. Agricultural practices are sources of nutrients via fertilizer
application and runoff from animal wastes. Other agricultural activities that affect the ecosystem
are the addition of pesticides or herbicides, which can be toxic to aquatic life and water-dependent
wildlife, and the construction and use of flow control structures at Johns Pond for irrigating the
cranberry bogs along the Quashnet River, which can alter flow patterns, change the quantities of
surface water in the ponds and streams, and add to sediment-loading. Migration of pesticide and
other chemical constituents from an abandoned cranberry bog in the watershed could also
contribute chemicals to surface, and ground waters (HAZWRAP, 1995).
Aquatic Activities. Water-based activities also are sources of stressors to the estuarine
and freshwater ecosystems (Waquoit Bay Watershed Citizen Action Committee, 1992;
HAZWRAP, 1995; WBNERR, 1995). These activities include recreational boating, which is a
source of nutrients and human pathogens from on-board septic systems and toxic chemicals from
leaching of antifouling paint chemicals from boat hulls and spills of fuel and other discharges from..
marinas; construction of docks and piers using lumber treated 'with heavy metals and other wood
preservatives or antifouling compounds, which can introduce toxic chemicals to the estuary
(Figure E-5); waterway maintenance, including dredging and shoreline modification, which adds
resuspended sediments; shellfishtng in the estuary, which damages eelgrass habitat, resuspends
sediments, and contributes to harvest pressure; recreational fishing in the estuarine, riverine and
pond environments, which contributes to harvest pressure; and swimming in the Bay and Ashumet
and Johns Ponds, which can disrupt benthic communities and resuspend sediments. More than
2100 boats greater than 6.1 m (20 ft) in length are estimated to use the Bay and rivers (Waquoit
Bay Watershed Citizen Action Committee, 1992), with an unknown number of smaller vessels
using the estuary and Ashumet and Johns Ponds.
Activities Outside of the Watershed. Several land and water use activities are not local
or can interact with local sources of stress: Armoring-of the coast outside of the watershed
changes sediment deposition patterns along the barrier beaches of Waquoit Bay. Offshore fishing
depletes the stocks of commercially valuable species such as. winter and summer flounder,
pollack, striped bass and bluefish. Wet and dry atmospheric deposition of nutrients and toxics can
have sources within and outside of the boundaries of the watershed Automobiles, lawn mowers,
.and motor boats generate NOx's locally. These atmospheric gases also originate hi coal-fired
plants hundreds of miles from the watershed. Nitrogen-containing atmospheric deposition adds
nutrients to the watershed (Valiela and Costa, 1988% Other toxic chemicals and metals can be
adsorbed to particulates from coal-fired plants, incinerators, and automobile exhaust fumes,
settling in the watershed. Mercury is a toxic chemical mat also originates outside the watershed
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Dock counts
1993
Waquoft
Bay
Figure E-5. Dock Counts in Waquoit Estuary in 1993. (Data from (L Crawford, WBNERR).
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but is deposited in the watershed where it can be methylated and accumulate in tissues of fishes
and piscivorous wildlife (reviewed in Facemire, 1995; Fitzgerald, 1995; Hurley, 1995: and
Weiner, 1995', HAZWRAP. 1995).
E.3.2 Stressor Characteristics
Altered flow, sediment, physical destruction, nutrients, toxic chemicals, eelgrass disease.
and fisheries harvesting were identified as the major stressors affecting the ecological resources of
Waquoit Bay watershed.
Altered Flow (Riverine). Hydrologic modification is a physical stressor that results in
altered stream flow patterns and reductions in the quantity of fresh water in surface
waters. Anadromous and catadromous finfishes need sufficient water depth to traverse the
shallow Waquoit estuary and streams; sufficient fresh water is needed to sustain certain estuarine
species that require reduced salinities and prevent saltwater incursions in the ground water (Day
et al., 1989; Milham and Howes, .1994). Changes in the hydrology of the Waquoit Bay watershed
can be sporadic, depending on precipitation patterns, especially the number and intensity of
hurricanes or northeasters versus periods of drought, as well as seasonal requirements for
irrigation of cultivated crops. Long-term reductions in ground water occur from municipal wells
that supply drinking water to the residents from the western lens, of the Cape Cod Aquifer.
Around die turn of the century, cranberry bogs were developed along the upper Quashnet
River and water flowing out of Johns Pond was controlled to provide water to the bogs as
needed, particularly in the fall for harvesting .the cranberries. This land use altered the flow
volume, velocity, and path of die river resulting in loss of spawning habitat for anadromous fish
species. Cranberry bop are often flooded in winter to prevent freezing and die water is then
released hi the spring. While the spring release might counteract die effect of groundwater
withdrawals, the harvest flood waters are often released during the time of autumn spawning for
trout (USGS, 1991). An extensive effort by Trout Unlimited and the Massachusetts Department
of Fisheries and Wildlife has restored major sections of the trout habitat, although some species
have not been restored. Alewives and blueback herring that swim to Johns Pond to spawn also
need sufficient water depth to traverse the bogs near die pond. Cranberry cultivation could be
increasing at the headwaters of the Quashnet hi the near future.
In addition, the Quashnet and die ground water that feeds it are currently under pressure
from urban development (Barlow and Hess, 1993). Plans to develop a community drinking water
well could further alter flows and affect the ground water system (Barlow and Hess, 1993),
including thermoregulation of the temperature of spawning beds in the rivers, which protect the
eggs of some fish species. Longitudinal, lateral, and vertical changes in salinity patterns in the
upper bay could have affected the distribution of some estuarine fauna and flora (e.g., Schroeder,
1978; Welsh et al., 1978; Day et aL, 1989). Dredging activity in the channels leading into
Waquoit Bay changes water flow patterns and flushing rates between Waquoit Bay and Eel Pond,
as well as the smaller ponds (Aubrey et aL* 1993). Changes in current patterns can lead to
shoaling near the inlets to the bay, primarily from flood deltas and secondarily from ebb deltas,
that in turn affect current patterns (Geyer and StgnelL 1992; Fitzgerald, 1993).
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Sediment.' Terrigenous and biogenic panicles accumulating in aquatic ecosystems r'rom
land runoff, erosion, and biological productivity are another physical stressor. Sediment can be
easily disturbed by currents, wave action, or organism movements, suspending particles in the
water column. The particle load is referred to as turbidity, which decreases light penetration
through the water, and the fine particuiates can interfere with feeding and respiration in benthic
and pelagic aquatic organisms and feeding in visual predators. Particles can remain in suspension
as long as the velocity of the water is sufficient to counteract gravitational forces. As water
velocity decreases, sediment particles settle, with heavier particles settling first; for example, swift
flowing streams can carry a higher sediment load that is then deposited when the stream empties
into a slower-flowing river or bay. Thus, fine-grained sediments are more likely to remain in
suspension.longer, resulting in increased turbidity. When the particles settle to the bottom,
deposition on surfaces of sedentary plants and animals, as well as the bottom, can cover
organisms that might have a difficult time removing the particles and alter habitat features, for
example, changing gravel bottom to mud (NRC,. 1992).
Changes in sediment loading and deposition in the watershed occur frequently, in concert
with changes in precipitation, surface water volumes, wind* or water-driven current patterns, and
construction or other human activities. Acute changes in sedimentation can occur after
catastrophic natural storms such as hurricanes (Hayes, 1978) and after dredging or construction
activities; chronic increases in sedimentation result as sediments'are resuspeoded by currents in
shallow areas. Swimming and burrowing activities of aquatic organisms can also influence
sediment deposition and resuspension (e.g., Yingst and Rhoads, 1978). Resuspended sediments
can reintroduce adsorbed nutrients and toxics to the water column.
The quantity of sediment entering the surface waters of Waquoit Bay watershed from
runoff and rivejs is unknown. Runoff is not thought to be a problem, since water readily
percolates through the sandy soiL Reductions in streambed permeability might occur if fine-
grained sediments deposit in spawning areas of the rivers (Baevsky, 1991), limiting gas exchange
from the eggs with the surrounding water. Increased turbidity from suspended and resuspended
sediments has reduced light levels needed for photosynthesis by eelgrass in Waquoit Bay,
although eelgrass could grow, slowly, at 10 percent of surface light intensity (Short et at, 1989;
Giesenetal., 1990). Sediment particles also increase the potential stress on eelgrass because
epiphytes growing on eelgrass blades are good depositional surfaces for suspended sediments
(Home et aL, 1994). Suspended sediments might also weight down the eelgrass blades causing
them to sink to die bottom where diey can die from insufficient light or suffocation (Kemp et aL,
1993; Short, 198$).
Protecting the coast from erosion by building of jetties and groins has several effects on
estuarine habitats. Jetties and groins alter regional sandand other sediment transport and
sedimentation patterns (WBNERR, 1995). These alterations can have a negative impact on
barrier beaches, salt marshes, and eelgrass beds, all habjtats for estuarine or water-dependent
wildlife. Shoaling near inlets to the bay has occurred from dredging, also changing sedimentation
patterns (Fitzgerald, 1993). These activities might also adversely-.arTect eelgrass beds in lower
Waquoit Bay.
Loss of eelgrass, in turn, also can change sediment depositional patterns since eelgrass
beds enhance sediment deposition (Short, 1984; 1989). The distribution and abundance of many
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benthic organisms can be adversely affected by sediment deposition. For example, softshells or
steamers grow best in Fine muddy sediments, but they are .more susceptible to predation in these .
habitats (Funderburk et al.. 1991). Siphon-clogging problems might occur in mud substrata which
can offset rapid growth rates in these sediments {Emerson et al.. 1988). Hard clams or quahogs
grow best in sandy sediments, since higher water currents provide more food to these suspension
feeding organisms (Rice and Pechenik. 1992). Juvenile quahogs lack extensible siphons and
attach to sand grains with byssal threads to permit them to feed at the sediment surface. Despite
this affinity for sandy to muddy sand sediments, adult quahogs are found in a variety of sediment
types, with gravely sediments providing protection from predators. The thick shell, lack of shell
gaping, and benthic burrowing limit the predation on these clams. It is not known whether
changes in the composition of the substratum have altered community structure to increase
shellfish predation.
Physical Destruction. Direct and indirect alteration of habitat structure is a physical
stressor that results in changes to the physical, chemical and biological conditions that support
the survival, growth, and reproduction of different species of plants and animals in a community.
In addition to hydroiogic modification, changes in current and flow patterns, and increased
sedimentation, several other mechanisms can alter the estuarine habitat in the Waquoit Bay
watershed, with subsequent effects on the organisms (Day et aL, 1989). These activities occur
sporadically;, the changes in conditions brought about by physical destruction can be short- or
long-term, but restoration of the habitat to its structure and function prior to destruction might be
impossible (NRC 1992).
Shading by docks built from shore- into the estuary, particularly in Great River, a tributary
of Waquoit Bay, decreases light penetration, adversely affecting eelgrass (Burdick and Short.
1995). This is not considered a major stressor on eelgrass or other aquatic lire in Waquoit Bay,
however, since the area covered by docks is small-less than 1 percent of the surface water area in
Waquoit Bay, its tributaries, and ponds (WBNERR, 1995). Mechanical disruption from clam
digging, boat props, and moorings can cut eelgrass blades or uproot eelgrass plants resulting in
death of eelgrass itself. Habitat fragmentation from these activities affects organisms mat reside
in eelgrass meadows. On land, construction of roads near the estuary can stop the landward
progression of salt marshes with deleterious effects on inhabitants.
Nutrients. Nearshore waters worldwide are receiving increased releases of nutrients,
particularly nitrogen, from coastal watersheds (e.g., Nixon et aL. 1986; Valiela et aL, 1990;
USEPA, 1994). Entrophkation, especially nitrogen enrichment in estuarineecosystems and
phosphorus enrichment in freshwater ecosystems, has been implicated as a major cause of
phytoplankton and nuisance macroalgal blooms (Day et aL. 1989; Batiuk et aL. 1992; MALMS,
1992). Inorganic nitrogen and phosphorus, primarily in the form of nitrate and phosphate, are
essential for the growth of photosynthetic algae and plants. La addition to inorganic carbon,
silicon, and other compounds (reviewed in Goldman, 1974, and Day et al., 1989). In the aquatic
environment, nitrogen is converted to various forms through complex biogeochemical cycles that
reduce or oxidize the elements or transform organic compounds to inorganic states, including
decomposition and excretion (of organic forms, ammonium, and phosphate), bacterially-mediated
nitrogen fixation (reduction of inorganic nitrogen to ammonium), nitrification (oxidation of
ammonium to nitrate), and denitrification (conversion of nitrate to'nitrogen gas by anaerobic
processes); Phosphorus is cycled through dissolved inorganic phosphorus, particulate organic
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phosphoms, and dissolved organic phosphorus states involving plants and complexation with
metals in sediments. Plants assimilate nutrients and produce, biomass by various biochemical • •
reactions during photosynthesis and these reactions are driven by the quantities of nutrients
available until they are saturated; usually the concentration of one or more nutritional substances
is less than its saturation level, limiting photosynthesis and plant growth. Day et al. (1989) noted
that aquatic plants have adapted to the average nutrient concentrations to which they have been
exposed.
As noted above, the sources, pathways, and fate of anthropogenic nitrogen are related to
land use patterns and in part to local and regional geology. Much of the nitrogen is believed to
be attenuated during passage through the Waquoit Bay watershed via volatilization, uptake by
flora and fauna, adsorption, and denitrification (see Rhodes et al'., 1985; Nixon and Lee, 1986;
Seitzinger, 1988; Reddy et al., 1989; WBNERR. 1993). The porous, sandy soils of this
. watershed promote rapid percolation of precipitation with the result that there is little run-off
from surface sediments (Strahler, 1968; Valiela et al., 1990; Oldale, 1992). Thus, nitrogen, added
either by precipitation or dry deposition, rapidly enters the ground water and can travel to
Waquoit Bay (Figure E-6). In a like manner, septic system and fertilizer additions of nitrogen and
phosphorus also penetrate the soil and make their way to the ground water and to Waquoit Bay -
(Valiela et at, 1996). Microbial decomposition of biogenic material and direct excretion by
animals into the ponds, rivers, and estuary are biological sources of nutrients. These processes -
interact with chemical processes occurring in the water column and sedunetns related to oxidation
and reduction of the nutrients to increase or decrease the quantities and forms of nutrients
available in the Waquoit Bay watershed (HAZWRAP, 1995).
Ground water concentrations of nitrogen are higher in more developed areas on Cape Cod
than in less developed areas (Figure E-7) (Persky, 1986).. Do the Waquoit Bay complex,
subwatersheds can be identified which have experienced different rates of nutrient loading due to
different patterns of land use. Ground water concentrations of nitrogen are higher in the more
developed than in the less developed subwatersheds (Table E-2) (Valiela et at, 1992; Rudy et al.,
1994). Different ratios of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen
(DIN) were found in the ground water of the Waquoit Bay watershed, with the most urbanized
subwatershed, the Childs River, having a ratio of 1:2, and the least urbanized, Sage Lot Pond,
Table E-2. Nitrogen Levels farGroundwater of the Childs River Sobwafe
to thai of Sage Lot Pond.
shed
Compared
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m
to
oo
Plant accretion (since mid 1800's)
Precipitation
t
Fertilizers
Oenitrification
X
Percolation
Septic systems.
NH4 adsorption
N2l N20
Nitrogen entering
coastal bay
Figure E-6, Inputs and fate of nitrogen (mol N K lO'yr') entering the watershed and traveling toward Buttermilk Bay near Wuijuoii
Bay; Additional sources not shown are precipitation directly onto surface waters and onto impervious surfaces thai aio washed inu>
surface waters. (Reprinted from "Couplings of Watersheds and Coastal Waters: Sources and Consequences o! Nutrient liiuichiucnt in
Waquoit Bay, Massachusetts," by Valielael al., published in Estuaries. December I992, Vol. 15. No. 4, pp. 443-457. wiili
from Estuaries. ©Estuarine Research Federation.)
rn
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*;t
8
9
4O
Building density (nouses
Figure E-7. Nitrate Concentrations in Ground Water Below Areas of Cape Cod Having Different
Densities of Buildings, Based on Data from Persky (1986) (Reprinted from "Couplings of
Watersheds and Coastal Waters: Sources and Consequences of Nutrient Enrichment in Waquoit
Bay, Massachusetts," by Valiela et al, published in Estuaries, December 1992. Vol. 15, No. 4,
pp. 443-457, with permission from Estuaries. ©Estuarine Research Federation.)
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having a iratio of 7:1 (Rudy et al., 1994). DON also appears to be influenced by the presence of
salt marsh, creating anoxic ground water and increasing the accumulation of DON. Ground water
travels at the rate of 13 feet per day in the watershed. Houses built very close to the shore have
the greatest impact on nitrogen loading to the bay. Year-built data and proximity to shore data
show that nearsnore areas were developed first and are the most densely developed (Sham et al..
1995).
Residential septic tanks could also be responsible for the additional input of naturally
occurring nutrients such as phosphorus and nitrogen into both of the freshwater ponds. The
MMR STP plume has been identified as the primary source responsible for increased levels of
phosphorous to the ground water discharging into Ashumet Pond (HAZWRAP, 1995). Since
1936, the disposal of treated sewage from MMR has been accomplished through infiltration beds
to a sand and gravel aquifer, creating a plume of contaminants 914 m (3,000 ft) wide, 23 m (75 ft)
deep, and more than 3353 m (11,000 ft) long, including high levels of sodium, chloride, nitrogen,
detergents, and other sewage-related compounds (LeBlanc, 1984; LeBlanc et al., 1991). Fate and
transport of contaminants in these plumes has proven very difficult to evaluate due to the
influence of the two large kettle hole ponds, Ashumet and Johns Ponds, on ground water flow.
Contaminants appear to be both discharging to the ponds and migrating under the ponds. The
USGS is currently evaluating the current and future impacts of phosphorus on Ashumet Pond; the
concentrations of phosphorus in the hypoliranion are higher in Ashumet Pond than Johns Pond,
but preliminary studies suggest that phosphorus might not be limiting here (Table E-3)
(HAZWRAP, 1995). The Quashnet River and Waquoit Bay are potential future locations for
ground water discharge of MMR plume contaminants in the absence of remediation.
Atmospheric NO3 and SO, deposition are either directly deposited to surface waters or are
transported in terrestrial runoff and drainage into ground water. The latter transport pathways
threaten to lower pH levels hi the Quashnet River and other surface water- or ground water-fed
streams in the watershed because mere is very little natural buffering capacity in the glacial soils.
The pH of the Quashnet is in the range of 6.0 to 6.4, which is not in the optimum range for brown
and brook trout and does not meet the Massachusetts Surface-Water Quality standards of 6.5 to
8.0 for Class B streams (Baevsky,. 1991). The major limitation for assessing the potential
ecological effects of nutrients on the Quashnet River is the paucity of available data.
Conversely, ecological effects of nutrients in the ponds and the bay have been extensively
studied. Phytoplankton blooms have appeared in these ecosystems (HAZWRAP, 1995;
WBNERR, 1995). Increased phytoplankton productivity decreases light penetration, altering the
light regime for submerged aquatic vegetation (Batiuk et al., 1992). Macroalgal matt, consisting
of the fast-growing species Oadophora vagabunda and GracUaria tikvahiae are present in the
shallow bay bottom adjacent to highly developed land areas, particularly the lower Quids and
Quashnet Rivers (Table E4). Epiphytes have grown on eelgrass blades (Valiela et aL, 1992;
Peckol et al., 1994), leading to reductions in the size of eelgrass patches in the bay (Orth and Van
Montfrans, 1984; Costa, 1988;BurkhoideretaL, 1992; Short et al., 1992; Valiela et al., 1992;
Boxhill et al., 1994; Hurlburt et at, 1994). Nutrients might not be the only factors influencing
phytoplankton and macroalgal growth in the ponds and bay, since altered/low ground and surface
water flow, changes in the distribution and abundance of herbivores, and light penetration (which
changes daily and seasonally) could also affect the abundance and distribution of key aquatic flora
(reviewed in Cambridge and McComb, 1984; Cambridge et al., 1986; Day et al., 1989; Necldes et
al., 1993; Boxhill et al., 1994).
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Table 3. Nutrient loading from the Massachusetts Military Reservation. N + P data extracted from Figures 7.26 through 7.29,
Volume II (HAZWRAP, 1995). Biology data extracted from pages 79-410, Volume I, and Figures 7.24 and 7.41 m volume II
(HAZWRAP, 1995).
/
Site
November 1992
Johns Pond
AshumetPond
April 1993
Johns Pond
Ashumet'Pond
June 1993
JohroPond epdimnkm
Johns pond hypolinuUon
Ashufnet Pond epHimnion
AshumetPond
hypoliinnion
August 1993
Johns Pond epUimnton
Johns pond hypolimnion
Ashumet Pond epl|knnkx»
AshumetPond
hypolimnion
Nutrients
Total DIN
«0-N/L
-60
-40
NH,
^g-N/L
-10
-3
NO,
ng-WL
-SO
-38
SRP
xg-p/i
-0.5
-1
TSP
MQ-P/t
-2.5-6
-7-10.5
Biology (Phytoplanklon)
Number of
cells/ml
-3000
-3000
mg fresh wl./m3
81-622
2447-7939
<-67
-750.
40-70
70-460
-60
-80430
<30
40-730
<20
0-660
<5-67
<6
20-40
40-460
-30
.-30430
<10
10-770
<20
0-860
<10
-750
20-30
<5-120
-50
-50
<20
0-30
0
0-40
~<1
<1
-0.5
0.5-5
-0.6 .
0.5-237
-2.8-5.6
-2
-1.6
1.5-15
-10 ,
10-180
<0.5
0.5-4
o
0-360
2.5-4
4-14.5
<5
5-275
11,000-22.000
20,000-78,000
3500-9200
200-1000
100-5600
100
1100-3800
1100-3800
300-2250
75-45
-25-200
<25
4800-37,000
2000-11,000
4800-35,000
-2000
220-4800
100*300
100-1300
<100
m
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Table E-4. Nitrogen loading to water table, chlorophyll concentrations, and mean (±
standard deviation) biomass of macrophytes in three selected subestuaries of Waquoit Bay.
Adapted from Valiela et al. (1992).
Rnfish and shellfish are at indirect risk from effects of nitrogen loading. Macroalgal mats
provide poorer quality finfish habitat than eelgrass beds for many resident finfish and for young-
of-the-year part-time resident finfish (WBNERR, 1995). Small fish can become trapped in the
tangle of algal filaments (Sloan, 1992). Although photosynthesis by the algae on sunny days
replenishes the oxygen, continuous cloud cover for several days can produce hypoxic or anoxic
conditions under the algal mats and send fishes into shallows where dissolved oxygen levels are
higher (Valiela et al., 1992). Johns Pond is classified as oligotrophic/borderiine mesotrophic;
Ashumet Pond is classified as mesotrophic and the hypolimnion becomes oxygen deficient as a
result of increased decomposition during summer stratification (Ashument Pond Trophic State
and EutrophicatioQ Control Assessment Report, 1987, cited in HAZWRAP, 1995). Fish kills
occurred in Ashumet Pond in July 1985 and May 1986. Mass mortalities of finfish and shellfish
occurred in the upper reaches of Waquoit Bay during July 1987,1988, and 1990. Valiela et al.
(1992) also noted that reduced photosynthetic activity by the macroalgal mats resulted in higher
nutrient concentrations in the water column followed by a bloom of phytoplankton during a July .
1988 prolonged overcast period. Preliminary measured rates of gross phytoplankton production-
and gross ecosystem production in the lower Quashnet River varied with time and decreased in
response to a complex suite of physical factors (Harrison et aL, 1994).
The benthic faunal community is affected by nutrient enrichment in two ways. Fust,
hypoxic and anoxic bottom water resulting from increased algal and microbial respiration,
particularly during cloudy days and nights in summer months, can produce physiological stress
and cause mortalities in benthic community organisms (IXAvanzo and Kremer, 1994). All life
stages of hardshell clams appear to be susceptible to low dissolved oxygen levels in the water,
with growth rates of larvae being reduced below 4 rag/L dissolved oxygen (Funderburk et aL,
1991). Adult clams can tightly close their shells and respire anaerobically in anoxic bottom
sediments in order to withstand these episodic events, but they generally fare better when
dissolved oxygen levels in the overlying water exceed 5 mg/L (Funderburk et al., 1991). Second,
although hard and soft clam growth rates from cleared bottom areas can increase in response to-
higher nutrient inputs and increased phytoplankton production (Chalfoun et aL, 1994; Harrison et
al, .1994), loss of eelgrass beds creates a loss of habitat that provided: shelter, refuge .and a food
source for many fishes and invertebrates (Valiela et aL, 1992). Other changes, in estuarine benthic
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communities have also resulted from eutrophication (Frithsen, 1991). Invertebrate species
abundance and diversity is lower in areas without eelgrass in Waquoit Bay (Valiela et al,, 1992V
The loss of eelgrass appears to be directly related to the success of scallop larvae. The
bay scallop larvae attach by byssal threads to eeigrass blades and the small juvenile scallops tend
to move up the eelgrass blade to escape benthic predation by crabs, starfish, oyster drills and
wheiks (Pohle et al.. 1991; Garcia-Esquivel and Bricelj, 1993). Byssal thread attachment by
juveniles is reversible and dynamic, allowing the young scallops to keep pace with the growth of
the eelgrass blades, which turn over rapidly during the summer. Rapid growth of juvenile scallops
occurs during this attached phase that can last a couple of months (Pohle et al., 1991). This stage
is followed by descent to the sediments at the base of the blades, at which time an epibenthic
existence without byssal thread attachment occurs. Adult bay scallops can occur in eelgrass beds
or over bare sandy substrate (Garcia-Esquivel .and Bricelj, 1993). Heavy predation by mud crabs
(Dispanopeus sayii), green crabs (Cardnus maenas), spider crabs (Ubinia sp:), and mobile
predators (northern puffer Sphaeroldes- maculatus) and brachyuran crab (Ovalipes ocellatus)
occurs on the small, epibenthic scallops which have shells and are incapable of complete or
provalve closure (Garcia-Esquivel and Bricelj, 1993). Thus, scallop populations tend to be
limited by predation on the attached larvae/small benthic juveniles and water quality affects the
pelagic larvae (MacKenzie, 1989).
Toxic Chemicals. The biota of the watershed could be exposed to potentially toxic and
bioaccumulative chemical contaminants. Toxic substances are materials that are capable of
producing an adverse response in a biological system, altering or impairing its structure or
function or producing death (Rand, 1995). Toxics can affect the induction or inhibition of
enzymes and/or enzyme systems within die cell, in torn altering the functions of these enzymes.
Enzyme dysfunction leads to disruption of metabolic processes including, but not limited to,
phosphorylatiori, uptake, or detoxification reactions, which is reflected in reduced/increased
production of cellular constituents, changes hi cell cycling and replication* and degeneration of
cellular and nuclear membranes. Effects produced by toxic chemicals ate dependent on the
concentration of the chemical and duration of exposure, as well as the type of chemical, its fate
and transport hi the environment, and other factors. Sublethai effects of toxics include changes in
behavior, growth, development, and reproduction of individuals, that ultimately affect the relative
distribution, abundance, and physiological condition of populations within aquatic communities.
Genotypic and pbenotypic factors operating within individuals affect their susceptibility to
different toxicants and ability to roetaboh^ the chemical to prodiH» other osmpcninds erf reduced
or greater toxicity. Some compounds, particularly the more hydrophobic/lipophilic ones, are not
readily broken down in the environment or by organisms and accumulate rathe fatty tissues.
Toxic effects then occur .when the concentrations of compounds are relatively high or the
chemicals are released when fats are metabolized, as during starvation.
The majority of die information concerning toxic chemicals in the Waquoit Bay watershed
is focused on the contribution of contaminated ground water emanating from the MMR
(HAZWRAP, 1995). Johns Fond and Ashumet Pond are located south of MMR and are subject
to potential contaminated ground water flow from the ™»«> industrialized portions of the bass—
including fiightline and fueling areas, and open storm drainage ditches. Water moving down
through soil contaminated by past industrial and military activities at MMR has mobilized
chlorinated solvents and fuel constituents forming plumes of contaminated ground
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water. Several of these plumes are migrating'within the Waquoit Bay watershed (Figures E-8 and
E-9). Several study sites or areas of concern (AOC) are under investigation north of the ponds
and the plumes could potentially affect both human and ecological receptors. These sites include:
Fire Training Area 2/Landfill-2 (FTA-2/LF-2), the Petroleum Fuel Storage Area (PFSA), and
Storm Drain-5 (SD-5) (HAZWRAP, 1995). For purposes of this investigation,all of the above
described plumes within the Waquoit Bay watershed have been grouped together as the Southeast
Regional Ground Water Operable Unit (SERGOU). SERGOU plumes originate from FTA-2/LF-
2, PFSA and SD-5 and for discussion of the conceptual model. SD-5 will be combined with runoff
from cranberry bogs because of the similar stressors, response pathways and resulting ecological
effects. Areas of concern FTA-2 and LF-2 occupy 20 acres of land used for fire-training exercises
that were conducted on the top of a former industrial/municipal landfill. Compounds disposed of
in the landfill or burned on the fire-training area consist of fuel, waste oils, waste petroleum
distillate solvents and domestic refuse. The PSFA is an active facility that is involved in the
delivery of various types of fuel and was the site of a 2,000 gallon fuel spill in the 1960s (ABB,
1991).
The contaminants from these plumes would affect the northern boundaries of the ponds.
Primary ground water contaminants of concern within SERGOU include chlorinated solvents and
volatile organic compounds such as methanol (Table E-5). Preliminary studies, however,
indicated that levels of volatile and semivolatile organics in surface water and sediments at these
locations hi the ponds were not elevated compared to other sites in the ponds in 1993. Further, it
appeared that some of the detected compounds were introduced as contaminants during
laboratory processing of the samples, e.g., di-n-butylphthalaie and bis(2-ethylhexyi)phthalate
detected in Ashumet Pond in April 1993; memylene chloride, zinc, and chloroform detected in
Johns Pond in April 1993). The greater number of samples collected hi August 1993 in Ashumet
and Johns Ponds did not greatly increase the number of contaminants detected in the surface
water. Neither trichloroethylene nor its metabolite, tetrachloroethylene, nor the common fuel
constitutents of the plumes (e.g., benzene, toluene, and xylene), were detected in fish tissue or
freshwater mussel tissue collected from the pond (HAZWRAP, 1995). The Quashnet River and
Waquoit Bay are potential future sites for MMR ground water discharge effects in the absence of
remediation and therefore the contaminants hi die plumes pose a threat to estuarine receptors.
Little data are available on die quantities and effects of pesticides, polynuclear aromatic
hydrocarbons, polychlorinated compounds, and heavy metals suspected of being present hi the
water, sediments, and biota in the ponds, rivers and streams, wetlands, and estuary. The water
released from tfje.cranberry bogs has contained pesticides and other contaminants that are toxic to
trout and other fish species and die macroinvertebrates on which they feed (MBL Science, 1985).
Pesticides from the MMR SD-5 area are primarily insecticides, rodenticides, and herbicides.
Pesticides widiin the water column can bioconcentrate hi aquatic organisms and accumulate hi
sediments, bioaccomnlate in fish, mussel, or other invertebrate tissues and affect terrestrial wildlife
that prey on these organisms, such as racoons and osprey. Concentrations of PCBs and the
chlorinated pesticides DDD and DDE were higher hi fish from Ashumet Pond man those from
Johns Pond, but all pesticide residues were within die range for comparable reference sites
(HAZWRAP, 1995). Analyses of fish enzymes and freshwater mussel lipids did not indicate
exposure to high concentrations of chemicals; catfish from both ponds exhibited a high incidence
of papUloraas on their jaws and around their mouths and adenocarcmbmas were found in the. •
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Cn>uudw3ter Phiine
— • Wuctshcd Bouoduy
Military
Reservation
Figure E-8. Groundwater plumes in the Waquoit Bay watershed.
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SOUTHEASTERN
IMPUIC
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Table E-5. Chemical contaminants in ground water from the Massachusetts Military
Reservation. Data from Monitoring Well Fence 4, Figures 7.1 through 7.6, Volume II,
HAZWRAP (1995). ND m Not detected.
Wells
MW-528 MW-522 MW-519 MW-518 MW-523
VOC 0*9/1)
Tetrachioroetheno
cis-1 .2-Oichloroetriene
1.2-Oichloroethane
Trichtoroethane
/"»U|^«-J*»-^
wntQIUUJim
Total Xytanes
Benzene
EfMM -»»-.—
etnyiDanzarw
1 ,2-Ofchtafoethen* (total)
SVOCfegA.)
Oki-butytpnthaiata
Naphthalene
2-M0thybfiaphthalen«
TPHOigA.)
ND
ND
W
3
ND
NO
1-2
a
0.6
16
t
0.6
D(nolv«d Inorganics* UoA)
Ca~
As
Fa
.Mn
Totw inorganics v^g/M
Cu
K
Fe
As
Mn
11,200
46.0
1630-
2230
33,000
178-788
NO
1
0.6
11.0
7050
1250
75.4-8600
13.0
1450
0,7
0.3
3
2-43
Z
n
0.3
S
11
ND
7.9-19.8
7050*28,200
400
7560-27,200
5.4-19.8
214-380
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Wells
MW-528 MW-522 MW-519 MW-518 MW-523
Cd
Pb
Mg
3.3
3.4
5630
Nutrients (ng/L)
SRF*
TSP*
NH«J
NO,*
26.23-26.39
25.07-29.87
0.19-0.63
572.1-1397
4.19-
22.64
6.13-1387
0.14-0.68
396-1615
23.62-
43.21
21.07-
35.73
0.09-0.10
1931-2085
6.15-21.33
8.8-19.73
0.05-19.81
2.82-2014
1 Values exceeding background levels
*AsP
3AsN
Table E-5. Continued, Monitoring Well Fence 2 (Figures 7.7 through 7.12, Volume II,
HAZWRAP, 1995).
Wells
MW-540 MW-539 MW-543 MW-544
VOC(M9/L)
Chloroform
Trichloroethene
Metnylene Chloride
Tetrachtoroetherw
Trichloroethene
SVOC(MP/L)
TPH (M9/L)
Olssoived Inorganics1 0
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REVIEW DRAFT -10 May 1996 - DO NOT CITE OR QUOTE
Wells
MW-540 MW-539 MW-543 MW-544
Total Inorganics' (pg/L)
Fe
Mn
K
Pb
Zn
Al
Nutrients fcgft.)
SRP«
TSP»
NH«*
NO,»
US
456
1910
5.17-25.58
8.27-26.67
0.41-6.68
40.84-3521
1600
5.2-5.8
105
3.05-23.29
6.67-23.47
0.25-1.98
1551-3260
802
8,76
10.67
1.55
1032
315
1.25-28.19
5.07-31.2
0.36-39.26
14.74-1977
1 Values exceeding background levels
»AsP
3AsN
Table 5. Continued. Monitoring Wefl Fence 5 (Figures 7.13 through 7.18, Volume H,
HAZWRAP, 1995).
««»-M—
trwnv
MW-82S MW-641 MW-621 UW426 UW-524
voc(M9/L)
TricNoroethene
• Chtoroform
1£-DfcntorotttMfle>
SVOCOigA)
Oi^butyphthai*
TPH(M9«.)
Otoeotved UioVM
Inocganlce
K
Fe
Mn
11
1
0.4-0.8
1640
0.7
NO
NO
605
413
NO
NO
—•
0.4
25
05
2
0.44.6
10-59
OJ
NO
0.3
2310
278
1770-3040
'E-298
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REVIEW DRAFT - 10 May 1996 • DO NOT CITE OR QUOTE
Wells
MW-525 MW-541 MW-521 MW-526 MW-524
Ca
Ba
As
Mg
Mn
Total inorganics1
(M9/L)
K
Mn
Fe
Ca
8a
As
Mg
Al
Be
Cr
V
Nutrient*
SRP»
TSP»
NH4S
NO,3
1600
1.9-3158
18.67-35.47
083-2,5fr
158.8-1938
18.300
368
90.7
18,700
2.88-35.37
0.05-33.6
0.94-51.15
240.7-1404
51.37-71.29
48^7-60^7
0.32-0.69
13.25-111.6
72.0
4.2
2260
137-514
68.7
6.5
2.56-15.62
9.87-20
2.027-15.09
662-4248
28.500-
39.500
5030-5740
250-443
5480
254-597
158-14,500
28,600-.
37,100
8.4
4950-8260
11,000
1.4
24.4
26.5
24.44-73.90
29.33-65.87
0.04-24.78
889.4-1622
1 Values exceeding background tavab
2AsP
'AaN
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Table 6. Chemical contaminants in Ashumet and Johns Ponds (Volume If, HAZWRAP,
1995, Figures 7-33).
Ashumet Pond Aprif 1993
APSW-1 APSW-2 APSW-3 APSW-4
Water concentrations in ugf\
VOCa
SVOCs
Di-n-butylphthaJate
ButyibenzylphthaJate
PEST/PCB*
Metato
Mn
MA
NO
1
NO
34
8660
NO
1
NO
35.7
8780
NO
NO
ND
34.6
8630
NO
1
NO
29.9
8860
Aahunwt Pond August 1993'
APSW-1 APSW-2 APSW-3 APSW-4
VOC»
Acetone
SVOCft
QmntflnhlflmmmLtimmtmt
rentacnioropnenoi
PEST/PC8*
NMato
Ba
Ca
Fa
Pb
Mg
Mn
K
Na
Zn
water concentrations MI MO/I
ND
1
ND
&9-2.1
1920-2900
603-1250
2J
2170-2230
29.6-1770
1170-2060
8560-8920
5.7-12.1
ND
16
ND
ND
2.8-4.3
1930-2540
44
2130-2170
363-344
1170-1230
8370-8770
6.1
NO
NO
NO
3
1885
2195
45.1
1270
9025
ND
ND
ND
2.6
1850
2200
48
125ft
8767
Voi'll, HAZWRAP, Rg. 7-34:
E-300
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Table6. Continued. Ashumet Pond sediments, 3rd quarter results. (Volume II,
HAZWRAP,. 1995, Table 7-4).
Ashumet Pond Sediments August 1993
APSD-1 APSD-2 APSD-3 APSD-4 APCB-1 APCB-2
Compounds
VOCs (uo/kg)
Tetra-chloroethane
1 .1 ,2,2, Tetra-chloroethane
1.1, i, Tricntoro-eihane
Toluene
Chlorobenzene
Acetone
2-Butanone (MEK)
Methyl ene.ChkxWe
. Carton Disulfkto
Ethytbenzene
7
280J
20J
100
22
1J
ND
SVOC* fug/kg)
Di-n-butylphthalate
Bis-2-ethylhexylpnthalate
Di*ethylphthalato
TIC (Benzote Acid)
Pentachtoro-pnenol
Phenanthrene
Carbozoto
RuoranthofM
Pyrene
Benzo
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Ashumet Pond Sediments August 1 993
APSD-1 APSD-2 APSD-3 APSD-4 APC8-1 APCB-2
Pestlcida/PCBs (MS/kg)
4.4'-DDT
ND
ND
ND
ND
ND
8.6
Metals fmg/kgt
Al
AS
Ba
Ca
Cu
Cr
Fe
Pb
Mg
Mn
K
Na
V
Zn
1610
2.2
13
333
1660
19.4J
321
66
223
129
43.7
914/793
9.5/8.2
268/198
1250/1172
12.8/8.7
213/223
72.8/88
115/76
56.3/73
3.6/3.0
15.4/19
1110
9.5
118
2.3
2.3
1860
2.7J
258
17*
174
43.8
4.5
10.2
VOCs • Volatile Organic Compound*
SVOCs - Semfeolatile Organic-Compounds
PCBs - Pdychtorinatod Biphenyta
TIC - Tentatively Identified Compound
548
7.9
128
592
6J
109.
56.9
69.4
60.7
12.4
397
1.8
67.4
732
139
57
43.5
45.5
teso
1.1
13.9
1170
12
7.4
4850
22.4J
773
58.2
369
85.5
12.9
ND'Non Detect
• BsonuuM van
IM
Table £•& C^irtfrMmL CTtrmkul cootamiiuuits in Ashtmwt nmf Johns Ponds (Volume n,
HAZWRAP, 1995, Figure 7-36).
Johns Pond Aprt 1993 .
JPSW-1 JPSW-2 JPSW-3 JPSW-4
voc
Mettrylene chksride
Cartaon disutfid*
SVOCs
watar concentrations in ftyi
ND
ND
ND •
9
.
• — —
ND
«.
OJS
ND '
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Johns Pond April 1 993
JPSW-1 JPSW-2 JPSW-3 JPSW-4
Di-n-butyiphthalate
bis(2-chloroethyl) ether
Diefhylphaiate
PEST/PCBs
Metals
Fe
Mn
Na
Zn
NO
48.9
15.2
8910
4.3
2
ND
73.3
22.4
8780
5.5
2
2
2
ND
NO
48.9
13.5
8810
4.8
14.1
8840
4.3
Johns Pond August 1993
JPSW-1 JPSW-2 JPSW-3 JPSW-4
Water concentrations .in vgfl
VOC»
SVOCa
Tributyl phosphate
PEST/PCBs
Metals
Al
As
Ba
Ca
Fe
Mg
Mn
K
Na
Zn
NO
16
NO
6.9-24.7
2840-3350
54.6-1240
2130-2160
36.5-1320
951-1100
83004630
38.9
NO
ND
NO
6.7-8
2840-3270
2150-2160
25.6
969-998
8440 ftflOn
ND
NO
NO
6.9-11.5
2770-2800
24.5-159
2150-2200
29.2-631
995-1100
84104880
NO
NO
NO
20.1
2.1
7
2874
2148
14.75
955
8924
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REVIEW DRAFT -10 May 1996 - DONOT CITE OR QUOTE
Table 6. Continued; Johns Pond sediments 3rd quarter results. (Volume II, HAZWRAP,
1995, Table 7-5).
Johns Pond Sediments, August 1993
JPSD-1 JPSD-2 JPSD-3 JPSD-4 JPCB-1 JPCB-2
Compounds
VOCs (u
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REVIEW DRAFT - 10 May 1996 - DONOT CITE OR QUOTE
Table 6. Continued. Johns Pond sediments 3rd quarter results. (Volume II, HAZWRAP,
1995, Table 7-5).
VOCs - Volatile Organic Compounds
SVOCs - Semivolatile Organic Compounds
PCBs - Pioychlorinated Bipnenyls
TIC - Tentatively Identified Compound
NO - Non Detect
J - Estimated Value
livers of two catfish from Johns Pond (Table.E-7). The causes of these lesions could be
contaminants, viruses, and/or genetic factors (Harshbarger and Clark, 1990; Baumann, 1992).
Heavy rainfall can result in short-term increases and transport of elevated concentrations of
chemical contaminants. These types of episodic events could cause lethal effects to biota.
Table E-7. Summary of histopathological examinations for brown bullhead catfish from
Ashumet and Johns Ponds, Cape Cod, MA (Volume D, HAZWRAP, 1995, Table 7.17)
Exterior Sores/Growths
Liver Cancer
Macrophage Aggregates
Functional Liver Tissue
47%
0
80% moderate/severe
81%
67*
2 individuals
90% moderate/severe
81%
Another toxic of concern in the watershed is the bioaccumulative and neurotoxic metal mercury.
A concentration of 1.2 mg/kg was detected in one largemouth bass fillet during a study of the
chemical contaminants in Ashumet and Johns Ponds (HAZWRAP, 1995). This concentration
exceeded the U.S. Food and Drag Administration action limit of 1.0 mg/kg to protect human
health. Deposition of mercury into surface waters and accumulation in sediments might produce
sublethal effects in pelagic and benthic aquatic organisms, as well as piscivorous wildlife.
Eelgrass Disease. Pathogens include infectious agents of disease such as viruses, bacteria,
fungi, and protozoa. Disease is any impairment of the vital functions of an organism; it can be
caused by other organisms known as pathogens (biological stressors) or by abiotic factors
(physical and chemical stressors discussed above). Pathogens can be endemic or introduced. The
severity of a disease is influenced by the susceptibility of the host, virulence of the pathogen, and
environmental factors that can affect the ability of the host to resist infection as well as the
proliferation of the pathogen in the environment or in the host. Diseases caused by pathogens
affect commercially important fjnfish and shellfish species in freshwater and estuarine ecosystems,
as well as the organisms on which they depend for food, shelter, and other resources
E-305
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REVIEW DRAFT - 10 May 1996 - DONOT CITE OR QUOTE
(Siridermann. 1990; Couch and Fournie. 1993). Outbreaks of disease can occur sporadically.
although chronic infections can produce siiblethal adverse effects in some individuals of a
population at all times. Biotic diseases can also affect behavior, development, growth.
reproduction, or survival of the population infected by a particular pathogen, as well as indirectly
affecting dependent populations and producing a cascade of effects in an ecosystem.
Although some pathogen-induced diseases of finfishes, shellfishes, and other aquatic organisms
have been reported elsewhere in the Northeast and probably occur in Waquoit Bay watershed and
black-crowned night-herons that feed in the bay have been found with abdominal lesions of
unknown origin (WBNERR, 1993), the .most significant biological stressor recognized in the
watershed is a disease affecting eeigrass. Eelgrass was at one time the dominant submerged
aquatic vegetation in coastal areas of die North Atlantic. In the 1930s the wasting disease, caused
by a slime mold (Labyrinthula) eradicated about 90 percent of the eeigrass meadows on both
sides of the Atlantic. The eeigrass recovered, but then declined again. In the 1980s, another
outbreak of the disease affected eeigrass beds in the United States (Short et al.. 1988). After the
1930s outbreak, many species characteristic of the eeigrass meadows disappeared, including the
gastropod snails Bittium altematun and Miterella, the Atlantic brant (Branta bcrnical hrota), and
the bay scallop (Short et aL, 1988; Short et aL, 1992). Bay scallop larvae and juveniles attach to
eeigrass blades to effectively avoid predators (Pohle et aL, 1991).
The eeigrass wasting disease has been found in a 1989 survey only hi the Hamblin Pond area of'
the Waquoit Bay complex (Short et aL, 1992). The* marine slime mold is adapted to the more
saline waters of die lower reaches of coastal ponds. In the aftermath of die wasting disease, some
eeigrass survived in die less saline parts of estuaries. Today, diese eeigrass beds are threatened by
their proximity to die coasts wim their collateral load of nitrogen and suspended sediments (Short,
1988). The wasting disease might also act synergisticaUy. widi stress from reduced light resulting
in decreased eeigrass growth.
Fisheries Harvesting. Harvesting of finfish and shellfish species by humans is anodw biological
stressor identified hi die Waquoit Bay watershed. Removal of aquatic resources at rates faster
than die organisms can reproduce and replenish die populations results hi reduced abundances and
limitations in distribution, as well as adverse effects on die species that prey on diese
commercially- or recreationally-important species. Qverharvesting has been recognized as serious
tittieat to die stability of freshwater, estuarine, and marine ecosystems (reviewed in Gulland,
.1983). Commercial fisheries can deplete stocks year-round, although fishing pressure is greatest
m summer when weadwr conditions are best
In me Waquoit Bay watershed, most of die finfish harvesting effort occurs offshore, focusing on
winter flounder, summer flounder, tautogs, and Atlantic pollack. Adult winter flounder can be
restricted in tiieir offshore distribution range from certain estuaries, so diat it is not clear dial die
Soutiwm New England (SNE) stock is indeed a distinct subpopulation of fish (biological stock as
opposed to economic stock). The same situation migtitapply to adult tautogs. Summer flounder
are at die northern extension of their range in die SNE area, so that mis species has a lesser
impact in die offshore region, from Waquoit Bay. Quantitative assessments provide evidence of
regional impacts resulting from fishing mortality 'and natural mortality (resulting from habitat
degradation, pollution effects,, eutropbication, meteorological events, and long-term change* in
climate).
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REVIEW DRAFT - 10 May 1996 - OONOT CITE OR QUOTE
Winter flounder and summer flounder are part-time estuarine residents that are important
commercial species in southern New England. Fishing mortality resulted in a 55 percent decrease
in annual survival for summer flounder and a 38 to 42 percent decrease for winter flounder in'
1992 (NMFS/NEFSQCUD, 1992). As a consequence of combined fishing and natural mortality.
the annual survival for summer flounder is 27 percent and that for winter flounder is 24 to 28
percent, which implies that both species suffer from excess harvesting. Thus, regional commercial
and recreational fishing activities play an important role in their distribution and abundance in
Waquoit Bay. The SNE stock biomass levels for summer flounder decreased dramatically from
1985 to 1991, and was dominated in 1991 by fish aged two years and younger (adults are viewed
as two and older). The winter flounder stock in SNE decreased to record low levels between
1989-1991, with a 1991 commercial catch of 4700 metric tons and a recreational catch of 1100
metric tons (NMFS/NEFSC/CUD, 1992).
For the tautog, in Southern New England state waters the maximum estimated fishing mortality
ranges from 0.15 to 0.33 (14 to 28 percent decrease in annual survival). The Massachusetts state
bottom trawl survey for Region 1 (Buzzards Bay and Vineyard Sound) and Region 2 (Nantucket
Sound) has shown a decreased index of abundance from 1982-1986 through 1992, even though a
common indicator of overfishihg, reduction in the average size of the adult tautog caught in
Region i, has not been detected (Caruso, 1993).
Recreational fishing of rainbow trout, brook trout, yellow perch and smallmouth bass within the
freshwater ponds systems is creating a demand on these resources and an increase in local fishing
efforts could reduce these resident finfish populations.
Shellfishing (commercial and recreational) in Waquoit Bay is regulated by the shellfish wardens
in Falmouth and Mashpee; commercial harvest records extend back to 1965 in Falmouth, and
from 1976 through 1987 in Mashpee (Table E-8). Town shellfish landings depend on shellfish
seed set or availability and fishing effort related inversely to shoreside employment opportunities
(MacKenzie, 1989). The quahog landings have been relatively stable during this period. Softshell
landings increased, probably as a consequence of more effort directed toward this shellfishery.
Scallop landings, however, have been mixed due to the short-lived (two years) nature of this
species and variable recruitment. Adult quahogs are susceptible to overfishing because of their
slow growth and variable recruitment; the population in the bay is dominated by commercially
undersized clams (Funderburk et at, 1991). The slow growth rates might also contribute to
increased susceptibility to predation. It takes'approximately two years for juvenile quahogs to
reach a minimum length of two inches in southern. Massachusetts.
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REVIEW DRAFT -10 May 1996 - DONOT CITE OR QUOTE
Table E-8. Shellfish Harvest by Year in Waquoit Bay, From Falmouth Commercial
Harvest Records.
1977
1978
1979
1980
1981
1982
1983
1986
1987
3930
3292
3590
3985
3540
4650
4410
2750
3045
41477
7200
244
596
985
550
3150
2600
232
300
950
1625
1730
1680
1938
1275
1819
54
654
65
100
15
E-308
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REVIEW DRAFT - 10 May 1996 - DONOT CITE OR QUOTE
APPENDIX F
LAiND USE MAPS FOR WAQUOIT BAY WATERSHED
E-309
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Land Use Categories by Classification System
19S1
1971
1980
1985/1990
40 Forest Type*
Agricultural
Agricultural with Walls,
Forest, and Wetland
Agricultural with Fresh
Water Meadow
Abandoned Field
Abandoned Orchard
Orchard
Cranberry Bog
Urban
Fresh Water Meadow
Deep Fresh Water Manh
Shallow Fresh Water
Marsh
Shrub Swamp
Salt Marsh
Fresh Open Water
Salt Open Water
Sand
Tilled/Tillable
Unuse.dTillable
Pasture
Orchard
Abandoned Field
Abandoned Off hf M
Cranberry Bog
Nurseries
Heath
Sand
Power Lines
40 Forest
Dump
Automobile Pumps
Filler Bed
Mining - Sand and Gravel
Mining-Other
Water
7 Fresh Water Wetlands
3 Salt Water Wetlands
4. Water Based Recreation
5 Participation Recreation
S Spectator Recreation
1 Environmental
Recreation
2 Urban Industrial
3 Urban Commercial
10 Urban Residential
S Urban Transportation
2 Urban Open and Public
Agricultural
Pasture
Forest
Open Space
Urban
Water
Cranberry Bog
Oiber
Agricultural
Pasture
Forest
Fresh Water Wetland
Mining
Open Space
Participation Recreation
Spectator Recreation
Water Based Recreation
Multi-Family Residential
High Density Residential
Medium Density
Residential
Low Density Residential
Salt Water Wetlands
Commercial
Industrial
Urban, Open & Public
Urban Transportation
Waste Disposal
Water
Woody Perennial
Cranberry Bog
Golf Course
Marina
Ocean
-------
Cape Cod,
Massachusetts
Pond Recharge Areas
A Snake Pond
B AshumetPond
6 Johns Pond
Drainage Sub-basins
1 Eel Pond
2 Childs River
3 Head of the Bay
4 Quashnet River
5 Hamblin Pond
6 Jehu Pond
7 Sage Lot Pond
Vineyard Sound
S Kaonwtw*
Seal* 1:100.000
-------
Lan
Use Categoric
s
Crop Land
Pasture
Forestland
Fresh Water fell and
Mining
Open Land
Participation Recreation
Spectator Recreatixm
fater Based Recreation
Multi-Family Residential
High Density Residential
Medium Density Residential
Low Densi-ty Residential
Salt let land
Comnercial
Industrial
Urban, Open and Public
Transportation
faste Disposal
fater
foody Perennial
Cranberry Bog
Golf Course
Marina
E-312
-------
Q
-1
1
E-313
-------
1
E-314
-------
c
1 L
0
E-315
-------
i
E-316
-------
4
J_
990
U u \J
E-317
-------
land Use Change over Time (ha!
_anc Use
1951
1971
1980
193;
1990
Acricultural land
Pasrura
Foresc
Fresh Water Weelands
Mining
Open Lands
Outdoor Recreation—Participation
Outdoor Recreation—Spectator
Outdoor Recreation—Water Based
Multi-Family Residential
dense•Residential
Medium Residential
Light- Residential
Salt Hater Wetlands
•Commercial
Industrial
Open and Public Urban Land
Urban .Transportation
Waste Disposal
Open Water
Woody Perennials
Cranberry Bog.
Golf Course
Marina
Total
Total minus open water
358.33
140.53
3717.88
31.19
185.97
90.76
110.21
425.64
321.71
111.11
175.33
23.36
3421.26
74.30
20.09
177.94
0.65
39.70
1.52
122.23
261.83
118.55
4.87
2.54
17.94
580.43
0.92
324.42
25.30
68.91
24.92
0.53
152.07
12.39 '
3201.53
49.56
18.79
191.77
0.22
27.14
286.19
371.56
143.06
1.46
12.58
591.98
324.34
21.58
51.63
25.18
i. ......
28.52
3059.55
80.87
23.50
171. 2S
€..38
3.18
29.43
10.55
34.26
343.30
398.36
129.47
11.84
1.96
203.03
437.01
2.42
354.48
34.18
31.71
26.85
114.13
26.95
2549-91
33.05
27.89
179.52
5.15
3.18
28.05
29.54
43.33
480.40
574.77.
129 . 10
17.22
3.73
22*. 34
440.40
4.07
371.67
14.33
41.77
46.21
2~. 78
5493.39 5493.01 5493.53 5539.58 5549.86
5171.68 5168.59 5169.19 5185.10 5178.19
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DRAFT Review Draft
DO NOT QUOTE OR CITE June 14,1996
DRAFT PROPOSED GUIDELINES
FOR
ECOLOGICAL RISK ASSESSMENT
NOTICE
THIS DOCUMENT IS A PRELIMINARY DRAFT. It has not been released by the U.S.
Environmental Protection Agency and should not at this stage be construed to represent Agency
policy. Tt i« h»ttig t*mil»tfA fine rnr^mj-nt n«i
Risk Assessment Fonnn
U^. Environmental Protection Agency
Washington, DC
•^-319
-------
DISCLAIMER
This document is an internal draft for review purposes only and does not constitute
Agency policy. Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
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CONTENTS
Lists of Figures, Tables, and Text Boxes vi
Executive Summary be
1. INTRODUCTION 1
1.1. ECOLOGICAL RISK ASSESSMENT IN A MANAGEMENT CONTEXT 5
1.1.1. Contributions of Ecological Risk Assessment to Environmental
Detiskramaking 5
1.1.2. Risk Management Considerations 6
12. SCOPE AND INTENDED AUDIENCE 7
13. GUIDELINES ORGANIZATION.... 8
2. PLANNING THE RISK ASSESSMENT: DIALOGUE BETWEEN RISK
MANAGERS AND RISK ASSESSORS 11
2.1. ESTABLISHING MANAGEMENT GOALS 13
22. MANAGEMENT DECISIONS ... 15
23. SCOPE AND COMPLEXITY OF THE RISK ASSESSMENT 17
2.4. PLANNING OUTCOME.. 18
3. PROBLEM FORMULATION PHASE 20
3.1. PRODUCTS OF PROBLEM FORMULATION , 20
3.2. ASSESSMENT OF AVAILABLE INFORMATION 22
33. SELECTING ASSESSMENTENDPOINTS,. 25
33.1. Selecting What to Protect 26
33.1.1. Ecological Relevance 27
33.12, Susceptibility to the Stressor 28
33.13. Representation of Management Goals 30
• 33.2. Defining Assessment Endpomts 31
3.4. CONCEPTUAL MODELS 36
3.4.1. RiskHypotbeses 37
3.4.2. Conceptual Model Diagrams 39
3.43. Uncertainly in Conceptual Models 41
3.5. ANALYSISPLAN 42
35.1. Selecting Measures 44
3.5.2. Relating Analysis Plans to Decisions , 46
4. ANALYSIS PHASE 49
4.1. EVALUATING DATA AND MODELS FOR ANALYSIS 52
4.1.1. Strengths and Limitations of Different Types of Data - - 52
4.1.2.- Evaluating Measurement or Modeling Studies 55
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CONTENTS (Continued)
APPENDIX C: CONCEPTUAL MODEL EXAMPLES ,.. C-l
APPENDDCD: ANALYSIS PHASE EXAMPLES D-l
APPENDDCE: CRITERIA FOR DETERMINING ECOLOGICAL ADVERSITY: A
HYPOTHETICAL EXAMPLE E-l
APPENDDCF: AUTHORS, CONTRIBUTORS, AND REVIEWERS F-l
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LIST OF TABLES
Table 4-1. Uncertainty Evaluation in the Analysis Phase 60
LIST OF TEXT BOXES
Text Box 1-1. Related Terminology 1
Text Box 1-2. Flexibility of the Framework Diagram 2
Text Box 1-3. The Iterative Nature of Ecological Risk Assessment 4
Text Box 2-1. Who Are Risk Managers? 11
Text Box 2-2. Who Are Risk Assessors? 12
Text Box 2-3. Questions Addressed by Risk Managers and Risk Assessors 13
Text Box 2-4. The Rote of Interested Parties , 14
Text Box 2-5. Sustainability as a Management Goal 15
Text Box 2-6. Management Goals for Waqnoh Bay 16
Text Box 2-7. Questions to Ask About Scope and Complexity 17
Text Box 3-1. Avoiding Potential Problems Through Problem Formnlation 20
Text Box 3-2, Uncertainly in Problem Formulation » 22
Text Box 3-3. Imtiatmg a Risk Assessment: What's Different When Stressors, Effects, or
Values Drive the Process? 23
Text Box 3-4. Assessing Availabte Information: Questions to Ask Concerning Stressor
Characteristics, Exposure, Ecosystem Characteristics, and Effects 24
Text Box 3-5. Salmon and Hydropower Why Salmon Would Provide the Basis for an
Text Box 3-6. Onrading Adverse Effects: Primary (Direct) and Secondary (Indirect) 28
Text Box 3-7. Sensitivity and Secondary Effects: The Mussd-Fish Connection 30
Text Box 34*. Examples of Management Goals and Assessment Endpoints 33
Text Box 3-9. Common Problems in Selecting Assessment Endpoints .34
Text Box 3-10. What Are Risk Hypotheses and Why. Are They Important? 37
Text Box 3-11. Examples of Risk Hypotheses 38
Text Box 3-12. What Are the Benefits of Developing Conceptual Models? 39
Text Box 3-13. Uncertainty in Problem Formulation 41
Text Box 3-14. Examples ofAssessment Endpoints and Measures 44
Text Box 3-15. Selecting What to Measure 45
Text Box 3-16. How Do Water Quality Criteria Relate to Assessment Endpoints? 46
Text Box 3-17. Data Quality Objectives (DQO)Process 47
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1 EXECUTIVE SUMMARY
2
3 The ecological problems feeing environmental scientists and decisionmakers are numerous
4 and varied. Growing concern over potential global climate change, loss of biodiversity, acid
5 precipitation, habitat destruction, and die effects of multiple chemicals on ecological systems has
6 highlighted the need far fl«rihle pmhlenvgnlvmg approaches that can link ecological
7 measurements and data with the decisionmaknig needs of environmental managers. Increasingly,
8 ecological risk assessment is being suggested as a way to address this wide array of ecological
9 problems.
10 Ecological risk asscrenwn* "evafagiex the liir eiihnnd that tthjgrsc ffx>iogical effects gnuy
11 occur or are occurring as a result of exposure to one or nrat stresses
12 pnx^ss for organizing and analyzmg data, infbnnadon,assum
13 me likelihood of adverse ecologk^ effects. Ecological risk assessment provides a critical dement
14 far environmental AietiiMiimlt ing hy giving rklc manager* an appmaeh far enma
15 scientific information along with the other factors mey need to consider (e^, social, legal,
16 political, or economic) in selecting a course of action.
17 To heipinipnwe the qualrtyaiid consistency of E^
18 Risk Assessment Foram mhiated development of these gmdelmes. Previous materials prepared by
19 me Forum to support tmseffonitKludc the 1992 report ^nmewodcfe
20 Assessment" (referred to as the Framework Report) as wdl as numerous case studies and issue
21 papers. These guidelines were written by a Forum work group and have been extensively revised
22 based on conmients from outside peer reviewen as well as Agency sti^
23 guidelines Tetam the FraiMwock Report's bro
24 concepts and modifying others to reflect Agency experiences. EPA intends to follow these
25 guidelines with a series of shorter, more detailed documents mat address specific ecological risk
26 assessment topics. This "booksheiT approach provides the flexibility necessary to keep pace with
27 developments in the rapidly evolving field of ecological risk assessment while allowing time to
28 form consensus, where appropriate, on sdenwpoUcy inferences (defiuilt assumptions) to bridge
29 gaps in knowledge.
DRAFT-DO NOT QUOTE OR CITE ix 6/14/96
E-324
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1 or area! extent and patch size of eelgrass). For a risk assessment to have scientific validity,
2 assessment endpoints must be ecologically relevant to the ecosystem they represent and
3 susceptible to the strcssors of concern. To increase the likelihood that the risk assessment will be
4 used in management decisions, assessment endpoints that represent societal values and
5 management goals are more effective. Assessment endpoints that fulfill these criteria provide the
6 best foundation for an effective risk
7 Potential interactions between agggsy*""1* endpoints and stressors are explored by
8 developing a conceptual modeL Conceptual models link anthropogenic activities with stressors
9 and evaluate intenrlationships between exposure pathways, ecological effects, and ecological
10 receptors. Conceptual models include t™** pr|n£>pn' components! risk hypotheses and a
11 conceptual model diagram.
12 Risk, hypotheses describe predicted relationships between stressor, exposure, and
13 assessment endpoint response, Risk hypotheses are hypotheses in me broad scientific sense; they
14 do not necessarily involve statistical testing of noli and alternative hypotheses or any particular
15 analytical approach. Risk hypotheses may predict the effects of a stressor (e^ a chemical
16 release) or they may postulate what stressors may have caused observed ecological effects; Key
17 risk hypotheses are identified for subsequent evaluation in the Tjyfc
18 A useful vay to express the relationships described by the risk hypotheses is through a
19 eaneepftui ™p4fl dfagrmi. «tf eh if t "ifiti rfpm?f^*«qii of" cmFfrfliil HKKM. Conceptual
20 model mflgfAhi* afg iKgnii teftlg'Tnr enrnrnnm.'^ting important |utKm«y« tn a e\**r anH jvnuti*^
21 way and for identifying major sources of uncertainty. Risk assessors can use both conceptual
22 model diagrams qnd risk hypodieses to idffltify tftP rnoA import
23 that will be evaluated in tile analysis phase. Risk assessors justify what wfll be done as well as
24 what will not be done in the assessment in an analysis plan, the analysis plan also describes the
25 data and measures to be used in me risk assessment and how risks will be characterized.
26 The analysis phase, which follows problem formulation, uidudes two prhwipal activities:
27 characterization of exposure and characterization of ecological effects. The process is flexible,
28 and interaction between the ecological effects and exposure evaluations is recommended. Both
29 activities include an evaluation of available data for scientific credibility and relevance to
DRAFT-DO NOT QUOTE OR CITE xi 6/14/96;
E-325
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I Risk assessors describe risks by evaluating the evidence supporting or refuting the risk
2 estimates) and interpreting the adverse effects on the assessment endpoinL Criteria for
3 evaluating adversity include the nature and intensity of effects, spatial and temporal scales, and the
4 potential for recovery. Confidence in the conclusions of a risk assessment is increased when there
5 is agreement among different lines of evidence of risk.
6 When risk characterization is complete, a report describing the risk assessment can be
7 prepared The report may be relatively brief or extensive depending on the nature and the
8 iwflffpgs avaitefrte *"f tUtg JSftgyyf^n and the infonrMftifln required to support a risk management
9 decision. Report dements may include:
10 • A o^scr^oo of risk assesson^risk manager planning resuhs.
12 • A discussion of fee major data sautes and anarya^
13 • A review of the soessor-response and exposure profiles.
14 • A dfliK'i ijrtKTfi flr nifkft tiff ttig aiHHfymiflHt ^itdpoiiifSt mclttdtng risk CTtnnatCT and adversity
15 evaluations.
16 • AsunimaryofinajorareasofuDcenamryandmearjproacnesusedto
17 • A discussion of science policy judgments or default assumptions used to bridge
18 information gaps, and the basis for these assumptions.
19 To facilitate understanding, risk assessors should chara thy pnMir, thff riffk 'rmmiink*'*™" r**^^ 15 ^^^ «^miBrf hy tailoring
25 information to a particular audience. It is important to clearly describe the ecological resources at
26 risk, their value, and die costs of protecting (and failipgtoprotect) the resources (U.S. EPA,
27 1995d). The degree of cc^oerice m me risk assessment arid the ratkmale for risk n^
28 decisions and options for reducing risk are also important (U.S. EPA, 1995d)l
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APPENDIX F
PRELIMINARY IMPLEMENTATION STATEMENTS
-------
KlflXOM f
DRAFT RISK CHARACTERIZATION XXFLEKBMT&TXOM PLAH
Second Draft
August 29, 1995
9.8. Bnvirouantml Protcotioa Ag«acy
Dallasf Tczaa
F-l
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F-2
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REGION «
DRAFT RISK CHARACTERIZATION IKPLJEMENTATION PLAJT
TABLE OF CONTENTS
I. Introduction. .p. 1
Plan in development
Region 6 Risk Characterization Teas
Draft Plan not reviewed by Region 6 Management
II. Purpose of Document ..,. p. 2
Components of the Regional Plan
III. Background of Risk Characterization.... p. 3
Administrator'.s March 1995 memorandum
Agency Characterization Guidance and Policy
Region 6 risk activities and categories
IV. Relationship of Risk Characterization to Risk
Assessment p. 6
The summarizing step to risk assessment
Not. a reiteration of assessment conclusions
V. criteria for Judging Adequacy of Risk
Characterizations .* p. 7
Administrator's characterization goals:
clarity, transparency,. consistency, reasonable
VI. Ensuring Consistency p. 9
Responsibility of Regional 'Characterization Team
Program documentation
VII. Evaluating Special Circumstances p. 10
Regional examples of Category X and II analyses
VIII.Scope of the Region 6 Implementation Plan. ..- p. 14
IX. Guide for Developing Chemical Specific Risk
Characterizations. p. 15
Summarizing major conclusions
Risk conclusions and comparisons
X. -Statement of Commitment*. ..p. 20
Key elements of the Region 6 Characterization Plan
TABLES
Table 1. List of Region 6 Risk Assessment Activities p. 23
Table 2. Glossary of Acronyms / Region 6 Risk
Related Terms p. 25
ATTACHMENTS
Attachment A. Region 6 Risk Characterization Program Documents
Draft Superfund Risk Characterization Plan (6//9S) .p. Al-1
Draft Risk Characterization} Environmental Justice
Index Methodology (8/95) p. A2-1
F-3
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TABLE OP CONTENTS
Attachment A (continued).
Draft Risk Characterization Implementation Plan UIC
Land Ban Response (8/95) p. A3-1
Attachment B. EPA/Region 6 Memoranda
Administrator's Risk Characterization Program
Memorandum (3/95) p. Bl-1
Regional Risk Characterization Implementation Team
Memorandum from Regional Administrator (5/95)*..p. B2-1
Region 6 Nominee to the Risk Characterization
Implementation Team Memorandum from Regional
Administrator (5/95).. .....p. B3-1
Regional Risk Characterization Implementation Team
Memorandum from Regional Administrator .p. B4-1
Response to Comments on Draft Regional Risk
Characterization Plan. Memorandum from
Risk Team. p. BS-1
Attachment C. EPA Policy and Guidance Documents
March 1995 Policy for Risk characterization at the
U.S. Environmental Protection Agency p. Cl-1
Guidance for Risk Characterization
(February, 1995) p. C2-1
F-4
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REGION « EPA
RISK CHARACTERIZATION IHPLZMEJTPATION PLAN
!• Introduction
Risk characterization is the summarizing step of risk assessment.
The risk characterization integrates information from the
preceding components of the risk assessment: Hazard
Identification, Dose Response, and Exposure Characterization.
Risks can be partially described by the individual components of
a risk assessment, but risk"characterization is a conscious and
deliberate process of bringing all important considerations about
risk into an integrated and complete picture. Even more
importantly, as an integrated picture, the risk characterization
is not simply a reiteration of conclusions of the various
components, but a piece which' focusses on how those components
interact.
The following Region 6 Risk Characterization Implementation Plan
is the second draft of an evolving' set of risk characterization
procedures, policies, and guidelines. This draft Plan has not
been reviewed by Region 6 Management or the Region's legal
counsel. The Plan is a product of risk assessors form the major
Region 6 Programs, risk assessors in all EPA Regions, and a
Headouarters Risk Characterization Core Team.
The plan attempts to address the full scope of risk analyses
performed in Region 6; Regional assessments are defined and
placed into three categories: Screening, Intermediate, and
Baseline (Categories I, II,.. and. Ill respectively). These
categories are used to identify what level of risk
characterization effort, can be performed for each.
Full risk characterizations for Regional products are not
possible at this time for several reasons: 1) Agency guidance is
not available for uncertainty analyses, ecological risk, or cost-
benefit studies.; 2) risk characterizations for Programs involving
permits must be coordinated with National, and State partners; 3)
risk characterization policies have not been developed to address
risk analyses performed by industry facilities, 4) resources are
not available to perform additional, more extensive, risk
characterization procedures and studies.
Although Region 6 recognizes the barriers to full implementation
of Agency risk characterization, the Region is committed to
coordination of risk characterization efforts, ensuring
scientific credibility, and striving to attain the
F-5
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Administrator's goals for clarity, transparency, consistency, and
reasonableness of risk assessment conclusions. Transparency
requires that conclusions drawn from science are identified
separately from policy judgments, and the. use of default values,
methods, and assumptions in the risk assessment are clearly
articulated.
II. Purpose
This Implementation Plan addresses all risk evaluation activities
in Region 6 and provides the Region with guidance for
characterizing risk assessment conclusions. The goal is to
institutionalize a consistent risk characterization process. The
Plan emphasizes the concepts of clarity, transparency,
consistency, and reasonableness. By providing an operational
framework for Region 6 risk characterizations, the Plan expands
on the Agency,'s March 1995 Risk Characterization Policy and it3
accompanying Guidance (Attachments).
The Implementation Plan identifies the kind* of assessments
produced by Region 6 Programs and addresses how the principles
and guidance will be reflected in each, of them. Where a
principle or guidance, point cannot be incorporated, reasons are
given or a plan for filling the gap is provided.
The objective of the Risk Characterization Policy and this
Implementation Plan is to ensure that risk characterizations' .forar
a complete and Coherent picture at; a. level of detail appropriate
•for the decision being supported* Accordingly, greater emphasis
is placed on ensuring clarity, consistency, and reasonableness of
the risk picture and transparency of the decision-making process
than on reformatting or otherwise reiterating the conclusions of
risk assessment components that precede the characterization.
Key elements of the Region 6 Risk Characterization Plan include
the following:
1) An inventory of Regional risk activities with each risk
assessment assigned to one or more categories (TABLE 1).
2) Definitions for three categories of Regional risk
evaluations based on level of effort, cost, statutory
requirements, and uses of the assessment results.
3) formation of a Regional Risk Characterization Team
responsible for coordination. Program consistency, reporting
to Senior Management, and assuring scientific credibility of
risk characterization products.
4) Recognition that full implementation is dependent upon
development of specific technology guidance .documents.
F-6
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5) Full implementation is dependent upon technical / statutory
coordination with Headquarters EPA Programs and increased
resources.
6) A schedule for implementing the plan and initiating th«
development of Program specific risk characterization
documents.
7) Recognition that adherence to quality science and rigorous
documentation procedures are the basis for successful risk
characterization in Region 6.
III. Background
In March of 1995, the Administrator issued a policy statement
which requires that risk characterizations be prepared "in a
manner that is clear, transparent, reasonable and consistent with
other risk characterizations of similar scope prepared across
programs in the Agency". The Statement was accompanied by the
Agency guidance jfor Risk Characterj^atj-on. The Administrator's
Risk Characterization memorandum, the Policy and Guidance are in
Attachment A. The guidelines were prepared by the Science Policy
Council in consultation with Regional risk assessors. The
Science Policy council has organized a Risk Characterization
Implementation core Team. The Team is responsible for
coordinating the development of risk characterization plans for
EPA Headquarters and Regions.
Region 6 has participated in the Core Team and Regional risk
assessor's planning conference calls', assisted in development of
a Regional Draft Superfund Risk Characterization Implementation
Plan, and formed a Regional Implementation Team. The Region 6 :
Team is composed of staff risk assessors-from our Water,
Hazardous Waste, Superfund, Air, and Enforcement Divisions* The
Regional -Team is composed of Dr. Jon Rauscher, Dr. Ghassan
Khoury, Blake Atkins, Michael Morton, Young Moo Kim, Maria
Martinez, Mark Hansen, Phil Crocker, Clay Chesriey,- and Dr. Gerald
Carney.
The Regional Team has drafted a List of Region 6 Risk Assessment
Activities (TABLE 1). The Teaa has also assisted in the
formulation of a Program specific risk characterization draft
document. The Draft Superfund Risk Characterization
Implementation Plan was written by Region 2 and reviewed by
Superfund risk assessors representing all ten EPA Regions. The
draft Superfund Plan is Attachment B. The coordination in
writing the Superfund Risk Characterization Plan provided
consistency among Regions for this important Program. The Region
6 Plan directs each Region 6 Program to write a characterization
plan and provides the Superfund. Plan as an example.
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Table 1 provides a listing of various types of Region 6 risk
evaluations divided into three categories relative to data
quality and type, published guidelines, level of effort and cost.
Category I analyses are preliminary or screening risk
evaluations using initial ambient or regulatory data to identify
potential immediate and long-term health impacts from a site or
pollution source. These assessments often include limited or no
sampling data, assumed potential cause and effect: or association,,
evaluation of worst-case exposure scenarios, and a qualitative
uncertainty analysis. Risk managers can utilize this information
to formulate regulatory actions, determine enforcement
prior itization, or to rank various pollution sources.' These
assessments typically cost. less than $50,000 (excluding sample
collection, analysis and corrective action costs) . Level of
effort requirements are usually 1-3 EPA staff or contractor
assistance for 1 to 6 months. Examples of preliminary and.
screening assessments include evaluations for emergency response
activities, enforcement targeting, and risk comparison exercises
using water quality standards.
Category 11 risk assessments are iptefiiaedfrate, analyses and
include- more ambient sampling data* analysis of indirect
exposures, collection of site-specific exposure data, and a
qualitative assessment of uncertainty. The information from
these risk assessments can be used by risk managers to accelerate
.removal actions, to evaluate the effectiveness of remediation
options, water treatment or other regulatory activities.
Typically these assessments cost between $50,000 to $75,000
(excluding sample collection, analysis and corrective action
costs), and require 3 - 7 EPA staff or contractor personnel for 6
to 12 months. - Examples of* intermediate assessments are ranking-
sites for inclusion on the HPL using- the CERCLA Hazard Ranking
System (ERS), Superfund remedial design reviews, and permit
activities in- the HPDES and SDWA Programs.
Category XXX* The baseline or full risk assessment is
exclusively a CERCLA or RCRA program effort in Region 6. They
are analyses of the potential adverse health effects (current or
future) caused by hazardous substances released from a site in
the absence of any actions to control or mitigate these releases.
The baseline risk assessment contributes* to the site
characterization and subsequent development, evaluation and
selection of .appropriate response alternatives.' The results from
the baseline risk assessments provide risk managers with
information to determine if remedial actions are required, modify
remediation goals, -and document the magnitude and causes of the
risks at the site. " These assessments typically involve more
detailed risk characterizations thai} Categories I and IX.
Typically these assessments cost $75,000 or more (excluding
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sample collection, analysis, communication and remediation
costs). Approximately 20 EPA or contract personnel are required
with the effort extending from a 1 to 3 year period. Examples of
Regional baseline risk analyses are RCRA Facility Investigations
(RFI), CERCIA Remedial Investigation/Feasibility Studies (RI/FS),
and RCRA analysis involving incinerators.
It is important to note that these three categories can be a
continuum* The risk assessment activities described under one
category may be found under a different category as the needs for
the assessment and its intended use changes.
The "Guidance for Riafc Characterization* provides general
principles.for characterizing risk. These principles are as
follows:
1) The risk characterization integrates the information from
the hazard identification, dose-response, and exposure
assessments, using a combination of qualitative information,
quantitative information, and information regarding
uncertainties.
2} The risk characterization includes -a discussion of
uncertainty and variability.
3) Well-balanced risk characterizations present risk
conclusions and information regarding the strengths and
limitations of the assessment for other risk assessors, EPA
decision-makers, and the public.
An important early document in the evolution of Risk
Characterization Plans was "Elegants to Consider When Drafting
EPA Risk Characterizationa*. The document was a product of the
Core Team and provided the .following risk characterization
principles;
1) Risk assessments should be transparent, in that the
conclusions drawn from the science are identified separately
from policy judgments, and default values, analytical
methods, and assumptions must be clearly articulated.
2) Risk characterizations should include a summary of the key
issues and conclusions of each of the other components of
the risk assessment, as well as describe the likelihood of
harm. The summary should include a description of the
overall strengths and the limitations (including
uncertainties) of the assessment and conclusions.
3} Risk characterizations should be consistent in general
format,, but recognize the -unique characteristics of each
specific situation.
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4) Risk characterizations should include, at least in a
qualitative sense, a discussion of how a specific risk and
its context compares with other similar risks. This may be
accomplished by comparisons with other chemicals or
situations in which the Agency has decided to act, or with
other situations which the public may be familiar with. The
discussion should highlight the limitations of such
comparisons.
5) Risk characterization is a key component of risk
communication, which is an interactive process involving
exchange of information and expert opinion among
individuals, groups and institutions.
Specific principles for exposure assessment and risk descriptors
are given in the Guidance document. Paraphrased, they are as
follows:
1) Describe the distribution of individual exposures..
2) Describe population exposure.
3) Describe distribution of exposure and risk for subgroups of
the population.
4) Include situation-specific information where appropriate, to
add perspective, for possible future events or regulatory
options*
5) Include an evaluation of the uncertainty in the risk
descriptors.
Clearly it is not always, possible nor even necessary, to include
all risk descriptors for every r4.sk assessment since appropriate
data may not be available or the level of effort required to
obtain the data may not be appropriate for the level 'of decision
being made. An attempt is made in this document, -however, to
address each of the descriptors either by inclusion or by
explanation of why inclusion is not appropriate.
IV. Relationship of Risk Characterization to Risk Assessment
Risk characterization is the summarizing step of risk assessment.
The risk characterization integrates information from the
preceding components of the.risk assessment:'Hazard
Identification, Dose Response, and. Exposure Characterization.
Risks can be partially described by the .individual components of
a risk assessment, but .risk characterization is a .conscious and
deliberate process of bringing all important considerations about
risk into an integrated and complete picture. Even more
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importantly, as an integrated picture, the risk characterization
is not simply a reiteration of conclusions of the various
components, but a piece which focusses on how those components
interact.
V. Criteria for Judging Adequacy of Risk Characterisations
The EPA's commitment to producing risk assessments which include
enhanced, more detailed, and accurate risk characterizations is
dependent upon activities which meet the Administrator's goals of
clarity, transparency, consistency, and reasonableness. Melding
these subjective goals to risk assessment methodologies requires
careful definition of terms. What may be clear-in meaning to one
individual or group may not be so clear to another with different
experiences, training, or biases. Are we to aim for our clarity
and reasonableness toward a technical or non-technical audience?
Understanding that the interests of the Agency is important to
all citizens, it would appear the audience is both. Also assumed
in the qualitative terms transparency and consistency is "full
disclosure" of available information. Again, how transparent and
how consistent? Risk assessors must use the quantitative tools
they have to interpret the Administrator's goals. Setting
measurable criteria for subjective goals will require Program
specific end points. The Groundvater Program will use geological
and hydrological measures. The Drinking.Water Program may use
microbiological measures.
These goals of communicating clearly, having transparent
policies, consistency and reasonable actions can only be realized
if Program methods and logic are accurately documented. This
being accomplished, risk assessment/communication activities can
be clearly chronicled and information more easily accessed by EPA
and others.
1) clarity
Clarity is ultimately determined by understanding. Risk
characterizations should accurately document all data
accessed, the .source and quality of the.data, any bias in
the information, uncertainties, assumptions, and mention of
data not: included or unavailable. .Regulatory data-have a
pre-determined bias. The specificity of the assay used to
measure an ambient concentration or the specific sampling
location for the soil measurement are examples. Although
these are technical factors, they directly affect the
accuracy of the risk analysis. The risk characterization
strengths and limitations should be understood without the
audience having to completely understand the technical
details. Clarity can be accomplished more readily if risk
analysis specifics are easily accessible.
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Region 6 Program risk analyses can identify and assure that
specific bias producing assumptions and default values are
clearly articulated in the Risk Characterization sections of
their analyses. The Region's Risk Characterization Team can
assist each Program in adhering to consistent documentation
approaches and language.
2) Transparency
Transparency is a direct product of clarity and consistency
in risk analysis procedures. The logic.applied to selection
of specific default values should be readily apparent to
reviewers of Region 6 risk assessments. flhere attaining
clarity requires documentation and disclosure of risk
judgements/ transparency requires added statements
explaining the reasoning for assumptions and default values.
(Once I understand what the assessor did, I want to know
why.) with this information the assessment reviewer can
more easily determine the uncertainties and thus the
limitations when presented. The technical reviewer can
calculate risk conclusions based on different logic if
desired. -(Using a different body weight factor for children
or other smaller average weight subpcpulations.)
Accomplishing Regional risk assessment transparency as
defined above can be accomplished by simply defining (and
ultimately justifying) the assumptions and default values
used in risk analyses. This requires bringing these values
out of the dose response;.hazard identification, and
exposure characterization sections of Program risk
assessments. This can be accomplished by referencing and/or
attaching the default documentation used by the Program to
the assessment. Transparency will assist the public in
separating scientific- conclusions from Agency policy
judgements*
3) Consistency ......
Risk methodology consistency within Region 6 Programs, and
between Region 6 Programs, .Headquarter's Offices, State
Agencies, and EPA .contractors will require significant time
to accomplish.' Each EPA Program has developed specific
media terminology, defaults, assumptions, and assessment
guidelines based oa statutory and technical parameters.
Development of risk characterization language for national
permit programs (NPDES, SDWA, UGST) will require extensive
coordination activity among Federal (Headquarters, Regions,
and Laboratories),. State and local governments, and
.industry.
Region- 6 can inventory the risk methodologies, risk guidance
documents employed, decision criteria and logic used for the
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major Programs. This data can be.used to recognize
differences or similarities in report format, interpretation
of regulatory standards, risk language, algorithms, and
application of guidelines. The recognition will enhance
Regional clarity and transparency for risk products.
4) Reasonableness
Reasonableness of conclusions can be determined.if the risk
assessment characterization adheres to the principle of
clarity, transparency, and consistency as described above.
Is it reasonable to. use a 70 Kilogram body weight for a
population of chemical factory workers? Is it reasonable to
not perform an indirect exposure analysis when the source of
pollution is surface water discharge? Proper documentation
of all the risk related data to include information
describing the conservative assumptions and known
uncertainties will ensure more accurate judgements regarding
reasonableness of the analysis.
Procedures taken to document and compare the consistency of
Region 6 risk analyses will afford the Region a means of
comparing one risk to another. If a Superfund analysis
calculates a one in one hundred cancer risk for an exposure
based from water ingestion and the Drinking Water Program
calculates the same exposure at one in ten* thousand, a
reasonableness issue can be raised to both-risk assessors.
VI. Ensuring Consistency
Consistency in .definitions and methods of assessing risk is
fundamental to minimizing confusion, about risk estimates
generated -across the Agency. However, while risk assessments
conducted in Region € share similar goals with risk assessments
prepared by other parts of the Agency, statutory requirements and
regulatory interpretations influence our risk.-assessment .
approaches. The following sections describe areas where Region 6
can use Agency wide definitions, methods, and risk descriptors to
ensure consistency, and areas where such use is constrained.
Reference Doses (RfDs), cancer Potency Factors (Pfs)> Hazard
Indices (HZ),. Health Advisories (HA), Maximum Contaminant Levels
(MCL), Threshold Limit Values (TLVs), Permissible Exposure Limits
(PELS), National Ambient Air Quality Standards (NAAQS), and
Ambient Water Quality Criteria (AWQC) are a few of the many
environmental media standards and risk assessment calculations
used by risk assessors in Region 6. It is common in Region 6 for
risk assessors in our Drinking Water and Superfund Programs to
use an RfD from EPA's Integrated Risk Information System (IRIS).
Therefore., consistency exists among the Programs in using bass
risk assessment values* Inconsistencies occur as each assessor
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applies the value to the specifics of the Hater or Superfund risk
scenarios. Different uncertainty factors or other exposure and
hazard assumptions can be used by assessors. The inconsistency
is compounded when RfDs, Pfs, or MCLs do not exist for a given
compound.
Risk screening and targeting analyses typically use Regionally
derived or national standard toxicity values to infer potential
exposure or health- effects. Screening activities (Category I)
may have the largest range of inconsistent application of risk
values.
The Superfund Hazard Ranking System (HRS) , the National Pollutant
Discharge Elimination System (NPDES) Permit process, and use of
Ambient Water Quality criteria (AWQS)- to determine a screening or
intermediate level risk evaluation all use different algorithms
and exposure factors. The reasons for the. different approaches,
magnitude of the differences, and impacts upon the risk results
can be determined through implementation of the Region 6
characterization plan. The process begins with documentation of
the different analyses, regulatory guidance, and Program
rational*
Region 6 risk assessors from different Programs occasionally meet
to discuss available data and appropriate use of risk values.
The Region 6 Risk Characterization Plan will facilitate this
activity by communicating the Region's inventory of risk
activities, their level -of effort, and analytical processes to
each risk assessor. The Risk Characterization Team can monitor
consistency and be a clearinghouse for Region 6 Program specific
methodologies.
Complete integration, of risk processes is not possible in the
near term. - The Region 6 Plan will immediately begin to identify
and document the different media and statutory characteristics of
each Program 'and to communicate these differences to Regional
risk assessors.
. Evaluatin Secial
The Risk Characterization Policy recognizes that the nature of
the risk characterization will depend upon the information
available, the regulatory application of the risk information,
and the resources (including time) available. Considerations
specific to Region 6 include mandated site specific adherence to
risk assessment guidelines (Superfund Hazard Ranking System,
Remedial Investigation / Feasibility Studies) or analyses which
require coordination between the Region and other State or
Federal offices (FPDES, Air, and RCRA incinerator permits) . Each
have statutory requirements, court-ordered deadlines, or demand
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careful communications with Regional regulatory partners.
Category I and II risk assessment activities in Region 6 require
less than full risk characterization. Category I are screening
evaluations. Such evaluations do not have resources committed to
ambient sampling or extensive literature research. The level of
effort does not justify full characterizations. Category II
analyses are either permit related analyses, Regional guidance
supported by national standards, or risk targeting and
comparative risk studies. These studies usually do not have
level of effort resources to justify full risk: characterizations.
Category II risk evaluation for permit support have the
additional requirement for extensive coordination with our
regulatory partners. There are numerous examples of Category I
and II risk assessment in Region 6. The following are examples
of studies not requiring full risk (Category III)
characterization. Each study does require rigorous documentation
of data sources/ assumptions, data quality, and uncertainties.
1) The Region's Water Quality Management Branch has issued
guidance to our States concerning procedures for development
of water quality standards. The Region's Water Quality
Assessment (WQA) Branch occasionally performs screenings
using water and fish tissue data with State standards. The
Branch may also use national guidance (198$ "gold book*,
Quality Criteria for Water). Cancer risk slop* factors and
RfOs are obtained from IRIS as needed. Although full
characterization is not appropriate for this water analysis,
the Program would be required to document all relative
assumptions, uncertainties, and mathematical manipulations.
The sharing and mixing of Regional, Headquarters, and Stats
guidance and standards will require the Region to address
risk characterization with states
2) . Enforcement Targeting is a screening procedure .using
1990 Census data, Toxic'Release Inventory (TRI) data, chemical
specific information from the Superfund Chemical Data Matrix
document, EPA industry compliance data, and state information
to rank Region 6 industries and federal facilities as. to
potential risk to the surrounding communities. The Region has
performed this screening activity for three years. We share
all information with our State counterparts. Approximately
120 facilities are assessed each year. Environmental justice
(EJ) issues (demographics and proximity to the facility) are
evaluated and each facility is ranked using defined criteria.
The methodology is computerized and developed in coordination
with the Region's environmental justice strategy. A
methodology is written which includes the limitations of the
computer systems used, databases accessed, and assumptions
made by the developers. Separate documents exist' for the
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methodology and computer code. Peer review involves
distribution of the methodology documents inside and outside
of the Region (to .include State agencies and affected
industries).
3) Region 6 Management Division has developed an Environmental
Justice (Computer Assisted Demographic Screening) analysis.
Any Region 6 staff member can obtain population, economic
status, and minority demographic data (1990 Census) for given
communities through the Region's Geographic Information System
EJ methodology. The system requires the requestor to identify
the point which best represents the area and concern, state
the source and .quality of the locational data, and the EPA
program requesting the information. The methodology does not
directly address risk to human health. The system is u'sed
with a risk based analysis (i.e., Enforcement Targeting) to
screen for potential impacts from industry emissions, truck
and rail traffic, proximity to landfills, water treatment
plants, or other regulated facilities.
4) Region 6 Water Supply Program was asked for an opinion on a
pesticide for which there is no MCL or Health Advisory. Water
Supply used the RfD in IRIS and the procedures used by the
OGWDW for developing MCLGs to estimate a safe level in water.
This level was later corroborated with the Health Effects
staff in the office of Ground Water and Drinking water
(OGWDW). This is another screening level risk assessment not
considered to require full (Category III) characterization.
5) In the Public Water Supply .Enforcement Program, risk has been
used to set the national definitions of .significant
noncompliers. The, Regional- enforcement program uses the
national significant noncomplier definition to target
enforcement actions.. In . addition to addressing all
significant noncompliers, the Region also prioritizes certain
acute risks. Targeting according to acute risks and
significant noncompliance assures the highest risk situations
are addressed. This is a Screening Level risk assessment
(Category I).
6) Individual cases of risk are. discussed with water system
owners/operators for determining whether an alternate source
of drinking water should be sought; For example, discussions
with an Indian tribe, which detected high levels of uranium in
drinking water, convinced the tribe to shut down the drinking
water well with the highest levels of uranium and use an
alternate drinking water well with lower detected uranium
levels. As this exercise was part of compliance monitoring,
consider this a screening level risk assessment (Categoryl).
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7} Permitting processes and review in both NPDES and UIC
(Underground Injection Control) use national modeling criteria
which take into account human; health. Hunan health risks are
determined from MCLs and national standards. Consider these
intermediate level risk assessments (Category II).
8) A risk based ranking system for the Underground Storage Tank
(UST) Program is currently implemented by our States. The
analysis (Risk Based Corrective Action - RBCA) examines
contaminants, depth of contamination, population, use of
groundvater and other pathways-exposure criteria. SPA
suggested the methodology and the Region is in a technology
transfer partnership with the States. Questions concerning
risk characterization requirements of State partners for this
shared Program are being addressed by the- Region. The UST
analysis is a Category II activity.
9) The Region 6 Comparative Risk Project required each Program to
submit a "risk assessment* report. Each report discussed
routes of exposure, ambient pollutant concentrations, exposed
populations, and estimates of disease incidence, since the
1990 Region 6 report, Arkansas, .Texas, Houston, and geographic
areas such as the U.S./Mexico border, and the Mississippi
River corridor between Baton Rouge and New Orleans have all
begun some level of comparative risk study. The Arkansas,
Texas, U.S./ Mexico border, and Corridor studies all have EPA
funding. All the studies examine human health, socio-economic
risk, and environmental justice: issues. The Region routinely
participants in the development and review of risk reports
from the different: state, .local government, and academic
analysts. The Region 6 Risk Characterization Plan requires
outside researchers to include risk characterizations
consistent with level' of effort categorization.
An immediate question for Region 6 was what type of risk analysis
(screening, baseline, socio-economic, comparison of a standard to
monitored concentration, qualitative comparative risk study) should
the Regional Risk Characterization implementation Plan address.
The Plan identifies all Regional activities. The identification
process is an on-going activity requiring definitions to separate
risk * assessment from .risk screening, and related analyses. The
three categories were the result of this process.
Examination of the many category I and II risk evaluations
performed in the Region raised several issues. A few of these
question* arer
1) How will risk characterizations address multi-risk projects?
For example, environmental justice requires analyses for human
health, economic, disenfranchisement and other welfare issues?
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2) Rov are enforcement sensitive analyses to be performed? An
. enforcement targeting method for the prioritizing, of chemical
violators is an example. These characterizations will need to
integrate. legal, regulatory, and science issues.
3) Should non-Superfund analyses financed and/or developed with
EPA assistance have risk characterization requirements written
into the grant Statement of WorJc?
4) Should risk characterizations for issuance of EPA Permits be
approved by all parties (Regional permit writer, Headquarters
Office, State Agencies) before incorporation as Regional
policy?
Using the criteria for Category I, II, or III risk, activities vill
determine whether . an assessment requires less-than-full risk
characterization. The Regional. Plan requires full characterization
for category . Ill assessments only. Full characterizations
currently include human health evaluation only. Statistical
uncertainty analyses, ecological and cost-benefit studies are not
required of Category HI risk characterizations. As EPA
guidelines, training, and resources are made available to Region 6,
these evaluation tools and procedures can be implemented.
Communications regarding risk and associated uncertainties are
covered by the Administrator fs Risk Characterization Policy. This
includes communications between scientist*, between scientists and
decision makers, and between Region 6 Programs and the public.
Documents describing components of risk assessments (i.e., hazard
and exposure assessments)..,, even if prepared as separate documents,
will follow the risk characterization policy (striving for clarity,
transparency, c insistency,, and reasonableness) •
Documents related to risk or any of its components which are-
submitted to Region 6 by EPA contractors or other EPA Offices are
expected to follow the Risk Characterization Policy.
Documents from other Agencies or outside sources will conform, to
the Region's Risk Characterization Policy before beincr used for
risk related decisions.
Similarly, Information resource documents such as IRIS documents
which have been produced in the past by SPA but do not follow the
risk characterization- principles will be augmented to meet the
requirements of the risk characterization policy before being used
in making future risk-related conclusions.
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Documents submitted by the public to Region 6 that relate to risk
assessment or any of its components, particularly to support
alternatives to EPA risk assessments, will be evaluated in light of
the Risk Characterization Policy.
Ecological risk assessments are not covered by the Region 6 Risk
Characterization Implementation Plan because detailed guidance are
not available. However, if ecological assessment data is
presented, all ecological risk sections will address the points
discussed in the human health elements document to the extent they
are relevant. Characterizations should address the questions
raised in the Risk Assessment Forum's Framework for Ecological Risk
Assessment.
Assessments of benefits are not included in this Implementation
Plan. Although Region 6 acknowledges the principles of clarity,
transparency of process, consistency, and reasonableness apply also
to analyses of benefits, the Agency has not yet developed guidance
for these types of assessments.
IX. Guide for Developing Chemical-Sped fie Risk Characterizations
The following outline is a guide and formatting aid for developing
risk characterizations for chemical risk assessments. Similar
outlines will be developed for other types of risk
characterizations, including site-specific assessment* and
ecological risk assessments. A common format will assist risk
managers in evaluating and using risk characterization.
The chemical specific risk characterization outline has two parts.
The first part tracks the; risk assessment to bring forward its.
major conclusions. The second part draws all of the information
together to characterize risk. The outline represents the expected
findings for a typical complete chemical assessment for a single
chemical. However, exceptions for the circumstances of individual
assessments exist and should be explained as part of the risk
characterization. For example, particular statutory requirements,
court-ordered deadlines, resource limitations, and other specific
factors may be described to explain why certain- elements are
incomplete.
PART 0KB
SUMMARIZING MAJOR CONCLUSIONS IN RISK CHARACTERIZATION
1) Characterization of Hazard Identification
A. What is the key toxicological study (or studies) that
provides the basis for health concerns?
-How good is the key study?
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—Are the data from laboratory or field studies? In
single species or multiple species?
—If the hazard is carcinogenic, comment on issues such as:
observation of single or multiple tumor sites?
occurrence of benign or malignant tumors; certain
tumor types not linked to. carcinogenicity; use of the
maximum tolerated dose (MTD) .
—If the hazard is other than carcinogenic, what endpoints
vere observed, and what is the basis for the critical
effect?
—Describe other studies that support this finding.
—Discuss any valid studies which conflict with this finding.
B. Besides the health effect observed in the key study, are
there other health endpoints of concern?
-What are the significant data gaps?
C. Discuss available epidemiological or clinical data. For
epidemiological studies:
— What types of studies were used, i.e., ecologic, case-
control, retrospective cohort?
— Describe the degree to which exposures vere adequately
described.
— Describe, the degree to which confounding factors were
adequately accounted for,
— Describe the degree to which other causal factors were
D. Row much is known about fcojt (through what biological
mechanism) the chemical produces adverse effects?
— Discuss relevant studies of mechanisms of action or
metabolism.
— Does this information aid in the interpretation of the
toxicity data?
— What are the implications for potential health effects?
B. Comment on any non-positive data in animals or people,
and whether these data were' considered in the hazard
.identification.
F. If adverse health affects have been observed in wildlife
species, characterize such effects by discussing the
relevant issues as in A through B above.
6. summarize the hazard identification and discuss the
significance of each of he following:
— confidence in conclusions;
— alternative conclusions that are also supported by the
data;
— significant data gaps; and
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— highlights of major assumptions.
2) Characterization of Dose-Response
A. What data were used to develop the dose-response curve?
Would the result have been significantly different if
based on a different data set?
— If animal data were used:
— which species were used? most sensitive, average of
all species, or other?
— were any studies excluded? why?
— If epidemiological data were used:
— Which studies were used? only positive studies, all
studies, or some other combination?
— Were any studies excluded? why?
— Was a meta-analysis performed to combine the
epidemiological studies? what approach-was used?
were studies excluded? why?
B. What'model was used to develop the dose-response curve?
What rational* supports this choice? Is chemical-
specific information available to support this
approach?
— For non-carcinogenic hazards:
~ How was the RfD/RfC (or the acceptable range)
calculated?
— What assumptions or uncertainty factors were used?
— What is the.confidence in. the estimates?
— For carcinogenic hazards:
— What dose-response model was used?. LMS or other
linear-at-low-dose model, a biologically-based model
based on metabolism data, or data about possible
mechanisms- of action?
— What is the basis for the selection of the particular
dose-response model used? Are there other models
that could have been used with equal plausibility and
scientific validity? What is the basis for selection
of the model used in: this instance?
C. Discuss the route, and level of exposure observed, as
compared to expected human exposures.
- Are the available data from the same route of exposure as
the expected human exposures? If not, are
pharmacokinetic data available to extrapolate across
route of exposure?
— How far does one need to extrapolate from the observed
data to environmental exposures (one to two orders of
magnitude? multiple orders of magnitude)? What is the
impact of such an extrapolation?
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D. If adverse health affects have been observed in wildlife
species; characterize dose-response information using the
process outlined in A-C.
3) Characterization of Exposure
A. What are the most significant sources of environmental
exposure?
— Are there data on sources of exposure from different
media? What is the relative contribution of
different sources of exposure?
— What are the most significant environmental pathways
for exposure?
B. Describe the populations that were assessed, including as
the general population, highly exposed groups, and highly
susceptible groups.
C. Describe the basis for the exposure assessment, including
any monitoring, modeling, or other analyses of exposure
distributions such as Monte-Carlo or krieging.
D. What are the key descriptors of exposure?
— Describe the (range of) exposures to: "average*
individuals, 'high end* individuals, general
population, high exposure group(s), children,
susceptible populations.
— How. was the central tendency estimate developed? What
factors and/or methods were used in developing this
estimate?
— Hoy was the high~end estimate developed?
— Is there information on highly-exposed subgroups? Who
are. they? -What are their levels of exposure? - How are
they accounted for in the assessment?
E. Is there reason to be concerned about cumulative or
multiple exposures because of ethnic, racial, o*
socioeconomic reasons?
F. If adverse health affects have been observed in wildlife
species, characterize 'wildlife exposure by discussing
the relevant issues as in A through E above.
G. Summarize exposure conclusions and discuss the following:
— results of different approaches, i.e. modeling,
monitoring, probability distributions;
— limitations of each, and the ranae of most: reasonable
values; and
— confidence in the results obtained, and the limitations
to the results.
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PART
RISK CONCLUSIONS AND COMPARISONS
4) Risk Conclusions
A. What is the overall picture of risk, based on the hazard
identification, dose-response and exposure
characterizations?
B. What are the major conclusions and strengths of the
assessment in each of the three main analyses (i.e.,
hazard identification, dose-response, and exposure
assessment) ?
C. What are the major limitations and uncertainties in the
three main analyses?
D. What are the science policy options in each of the three
major analyses?
— What are the alternative approaches evaluated?
— What are the reasons for the choices made?
5) Risk Context
A. What are the qualitative characteristics of the hazard
(e.g., voluntary vs. involuntary, technological vs.
natural, etc.)? Comment on .findings, if any, from studies
of risk perception that relate to this hazard or similar
hazards.
B. What are the alternatives, to this hazard? How do the
risks compare?
C. How does, this risk compare to other risks?
- How does this risk compare to other risks in this
regulatory program, or other similar risks that the EPA
has. made decisions .about?
- Where appropriate, can this risk be compared with past.
Agency decisions, . decisions by .other federal or state
agencies, or common risks with which people may be
familiar?
- Describe the limitations of making these comparisons.
D. Comment on significant community concerns which
influence public perception of risk?
6) Existing Risk Information
Comment on other risk assessments that have been done on this
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chemical by EPA, other federal agencies, or other
organizations. Are there significantly different conclusions
that merit discussion?
7) other Information
Is there other information that would be useful to the risk
manager or the public in this situation that, has not been
described above?
X*. statement of
Through this Implementation Plan Region 6 intends to ensure that
risk characterizations produced by and for the Region will be
substantially consistent with Agency guidance and policy on risk
characterization, recognizing limitations in time and resources*
The plan will be updated as necessary.
The following is a summary of Key Elements contained in the
Region 6 Risk Characterization Implementation Plan.
1) The Plan addresses all risk evaluation activities providing
general guidance for characterizing, risk assessment
conclusions. The goal is to institutionalize a consistent
risk characterization process in Region 6.
2) The Plan emphasizes the concepts of clarity, consistency, and
reasonableness as stated by the Administrator. Region 6 will
participate in all EPA planned roundtables and workshops to
the. extent possible.
3) The Plan is consistent, in general format and purpose with
other Regions, and Headquarters Programs.
4) The Plan recognizes that full implementation is dependent
upon technical and statutory coordination with Headquarters
Programs. This coordination will be the responsibility of
each Region 6 Program. Full implementation will also require
increased, resources.
5) The Plan recognizes that full implementation is dependent
upon development of specific technology and related guidance
(i.e., statistical tools, ecological evaluation,, cost benefit
analysis, guidance for uncertainty analysis) and Program
specific characterization plans serving as S.O.P.'s.
6) The Plan identifies three risk analysis categories performed
in Region 6. Each category, is defined by specific criteria.
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7) The Plan presents an inventory of Regional risk activities
with each assigned to one or more categories.- A Regional
Risk Characterization Team will maintain a listing of the
Region's various Program assessments, .methods, procedures,
and use of standards.
8) The Plan defines Category III risk analyses as CERCLA and
RCRA baseline assessments.
9) The Plan considers Category II j. analyses as Regional
standards because they have more published guidance,
established EPA policy, and resource commitments.
10) The Plan discusses to what degree specific risk
characterization activities can be accomplished within each
Category.
11) The Plan estimates .the time required to implement specific
risk characterization activities within each category*
12) The Plan suggests an organization structure and Program
policy development plan to ensure consistency of
characterization content for each Regional Program.
13) The Plan provides for a Regional Risk Committee to be formed
providing a forum for risk assessors and managers to monitor
and maintain consistency of .Regional risk products.
14) The Plan requires risk characterization products to be
included in the deliverables for Jteojionally funded risk
assessments.
15) The plan emphasize* the adherence to quality science, .
documentation procedures, and Program institutionalization
of risk characterization*
16) Category I (Screening) assessments should implement the
Regional Risk Characterization immediately.
17) Category X assessments completed after the Regional Risk
Characterization Policy is approved should include
characterization sections to their risk methodology and
summary documents.
18) Category II assessments are to begin coordination activities
with related Region 6" Programs, Headquarters Programs and
Offices, and State partners to determine the feasibility of
including risk characterization sections to their
assessments.
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19) Category III assessments art to consolidate and enhance
risk characterization data and language into a specific
section for methodology and summary documents.
20) Progi
techi
Regie
implf
21) The Category III Programs will develop a five year plan for
Risk characterization implementation.
22) The Region 6 Risk Analysis Team will be accountable for:
- communication, of Regional risk activities
- coordination of cross-Program risk activities in the
Region
- reporting cross-Program activities to Senior Staff
- establishing Program consistency in risk
characterizations
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TABLE 1
List or Region * Risk Assessment Activities
Category Is Screening
Category lit Intermediate
Category Ills Baseline
G8BCL&
CBBCIJk
Time Critical Removals
Engineering Evaluation/
cost Analysis (EE/CA)
RCRA
Multi-media Enforcement
Targeting
8DWA
Risk comparisons using
MCL data
UIC risk comparisons
Hazard Ranking System (HRS)
Interim Record of Decision
Remedial Designs
AVPCOC
Underground Storage Tanks (UST)
RBCA (EPA/state partnership)
Indirect Combustion Analysis
8DWA
EPA HQ risk analyses with
promulgated standards
UIC permits
CBRCLA
Remedial Investigation/
Feasibility Study (RI/FS)
Record of Decision (ROD)
Incineration (Comprehensive
Indirect Exposure Assessment)
(CIERA)
RCRA
Facility Investigation/
Corrective Measures (RFI/CHS)
Incinerators/Boilers
(CIERA)
SOW*
EPA HQ risk analyses with
promulgated standards
CIA CWA
Risk screening of ambient Fish tissue risk analysis using
water using water quality IRIS or guidance values
standards/criteria HPDES permit review/development!
Hater permits (404,305)
Pesticides
Risk comparisons using
HA data
Pesticides
CWA
Risk assessment for a given
subpopulation using
extensive fish tissue
and/or other data with
appropriate assumptions
Pesticides
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TABLB is List of Regiott • Bisk Assessment Activities (continued)
Category I: Screening
Category II: Intermediate
Category III: Baseline
CAA
Risk comparisons using air
quality Btandards/IRXS
MBPa/BXS
CAA
SIPs
Mew-Source Reviews
Mr permits
MBPA/BXS
CAB
MBPA/BXS
Regional Initiatives
U.8 Mexico
Modeling applications
Lower Mississippi River
Corridor
Regional Initiatives
U.S. Mexico
Model development/application
Lower Mississippi River
Corridor
Regional initiatives
.special Projects
Comparative Risk
(Program specific)
Environmental Justice
(Site specific)
Multi-Media Enforcement
Targeting
Special Projects
Comparative.Risk*
(Regional study)
Environmental Justice
(Regional/Program study)
Special Projects
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TABLE 2
Glossary of Acronyaa / Roglon 6 Risk Related Texas
Aix Quality Standards - Criteria Pollutants and National Ambient Air Quality
AL/PCQC (Action Level/Preliminary Chemical of Concern)
AWQC (Ambient Water Quality Criteria)
Boilers - Furnaces/incinerators producing steam for industrial use
CAA (Clean Air Act) -
Comparative Risk * Regional and State analysis which rank environmental risks as to
potential for. adverse impacts to human health* the ecology, economy, and public welfare.
CWA (clean Hater Act)
CERCLA (Comprehensive Environmental Resource*/ Compensation and Liability Act) - Superfund
CMS/SB (Corrective Measure Study/Statement of Basis) - RCRA
CIERA (Comprehensive Indirect Exposure Risk Analysis) - RCRA
EIS (Environmental Impact Statements) - NEPA
EJ (Environmental Justice) - Risk projects which compare demographic data (population,
.race, and household income) for. specific communities iri Region 6.
EE/CA (Engineering Evaluation / Cost Analysis) - CERCLA
HA (Health Advisory) - SDWA, Drinking water standard
HRS (Hazard Ranking System) • CERCLA,. algorithm used to rank sites for possible placement
on the National Priority List-for Superfund.
Incinerators - A furnace for burning wastes under controlled conditions.
IRIS (Integrated Risk Information System) -
Lower Mississippi River Corridor - An area representing the southern one-half of
Louisiana. The corridor defines the river from Baton Rouge, LA to New Orleans.
MCLs (Maximum Contaminant Level) - SDWA
MCLQs (Maximum Contaminant Level Goals) - SDWA
Model Development. - Risk algorithms relating hazard, exposure, emissions, or other risk
factors. Computer model development is often time consuming requiring peer review,
computer specialists, extensive QA, documentation of data sources.
Modeling Applications - Use of risk algorithms to relate hajzard, exposure, emissions, or
other risk factors.
Multi-Media Enforcement Targeting - Evaluations of Region 6J industrial facilities for
enforcement prioritization. Census demographic data and TRI chemical emissions
information is used to estimate potential risk.
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TABLE 21 Glossary of Acronyms/Risk Related Texas (continued)
MTD (Maximum Total Dose) -
NAAQS (National Ambient Air Quality Standards) - Clean Air Act
NEPA (National Environmental Policy Act) Applies to all Federal Agencies
NESHAPS (National Emissions Standards for Hazardous Air pollutants) - CAA
NPDBS (National Pollutant Discharge Elimination System) - CWA
NPL (National Priority List) Sites meeting hazard ranking criteria (HRS) for listing as
Super fund.sites.
OGWDW (Office of Ground Water and prinking water)
PCBs (Polychlorinated Biphenyla) - EPA Program established to regulate disposal and
1 storage of.PCB chemicals.
PELS (Permissible Exposure Levels) - OSHA standards for air pollutant concentrations in
industrial environments.
Pfs (Potency Factors) - Cancer potency judgements found in IRIS
POHC (Principle Organic Hazardous constituent)
QA (Quality Assurance)
RBCA (Risk Based Corrective Action) ••* Underground Storage Tank risk screening activity.
71 EPA and State environmental agencies are in partnership! in implementation and use of
o this ranking system.
ROD (Record of Decision) Public document describing chosen remediation alternative (s)
for a Superfund site. Document includes risk assessment conclusions and data.
RCRA .(Resource Conservation and Recovery Act) - Regulations addressing the classification,
transport, disposal, and documentation retirements for solid wastes.
RfC (Reference Concentration) -
RfD (Reference Dose) - An estimate of a daily exposure to tjhe human population that is
likely to'be without appreciable risk.
RFI (RCRA Facility Investigations) -
RI/FS (Remedial Investigation / Feasibility Study) - CERCLA
Regional Initiatives • Geographic or pollution source specific risk projects specific to
Region 6 (i.e., U.S./Mexico border, Louisiana Corridor, Petro-Chemical 'Industry).
Risk Comparisons • a risk evaluation activity which uses promulgated standards (i.e. MCLs,
Rfds, HA, PELs) to judge the potential risk from a given site or pollution source.
SDWA (Safe Drinking Hater Act) -
SIPs (State Implementation Plans) - CAA
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TABLE 21 Olossacy of Acronyas/Risk Related Texas (continued)
Special Projects •> Risk analysis activities which are generally cross-media in scope and
geographically specific.
TLVs (Threshold Limit Values)
Time Critical Removal - CERCIA
UIC (Underground Injection Control)
UST (Underground Storage Tanks)
27
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DJULFT
RISK CHMiaCTERIZlffXOV ODIDBLIHBI
TOR
TEB OFFXCB Of SOLID «*8YB
U»S.
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TABLE OF COHTEHTS
I. Purpose , 1
II. Background ................ .2
III. Legal Effect.. 4
IV. Scope ............. * ...... 4
V. Relationship of risk characterization
to risk assessment and risk communication . 7
VI. Criteria for judging adequacy of risk characterizations . 8
A. Clarity ....... 8
B. Transparency .....,«..»..... 9
C. Reasonableness • •• • 10
VIZ., Ensuring consistency . . . . . • . 10
VIII.Evaluating Office-specific circumstances ........ 12
IX. Points to consider when preparing risk characterizations
and criteria for evaluating.compliance with the Risk
Characterization Policy .......... . .... . . . . 13
A. Summary, of and confidence in .the major risk conclusions
. . . ... . . ;, . . ... . . . . . . . ...;. 14
B; Summary of key issue* 15.
C. Methods used 16
0. Summary of the overall strengths and. uncertainties
of the risk assessment . . . . .- 17.
B. Put this risk assessment in context with
other similar risks . ............... 19
F. Other information . . . . : 20
6. Mechanism* to evaluate risk characterization ... 21
X. statement-of Commitment 22
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X.
This Risk Characterization Implementation Guideline provides
the operational framework within which all risk characterizations
in the Office of Solid Waste (OSW) are developed. The Guidelines
expand on the March 1995 Risk Characterization Policy and its
accompanying Guidance by providing OSW-specif ic factors which
affect the implementation of the general policy.
The Implementation Guidelines identify the kinds of
assessments produced by OSW which are covered by the Risk
Characterization Policy, and addresses how the principles and
guidance will be reflected in each of them. Where significant
principle or guidance points cannot be incorporated, these
guidelines call on producers of risk characterizations to provide,
reasons for such gaps.
The objective of the Risk Characterization Policy and this
Implementation Guidelines document is to ensure that risk
characterizations produced by this Program form a coherent
picture at a level of detail appropriate, for the decision being
supported. Accordingly, greater emphasis is placed on ensuring
clarity, consistency, and reasonableness of the risk picture and
transparency of the risk assessment process as an input to the
decision-making process than on reformatting or otherwise
reiterating the conclusions of risk assessment components that
precede the characterization.
EPA is developing policies and procedures for several key
issues that cut across the Agency (e.g., uncertainty analysis,
updating IRIS and supplementing IRIS with risk characterization
language in the interim, etc.) . As they are developed they will
become part of OSW' s policy and update this document.
II*
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In March 1995, the Administrator issued a policy statement
requiring that risk characterizations be prepared "in a manner
that is clear, transparent, reasonable and consistent with other
risk characterizations, of similar scope prepared across programs
i
in the Agency."
The "Guidance for Risk Characterization", which accompanies
the Policy Statement, provides general principles for
characterizing risk. These principles are as follows.
l. The risk characterization integrate* the
information from the hazard identification, dose-
response, and exposure assessments, using a
combination of qualitative information-,
quantitative information, and information about
uncertainties.
2. The risk characterization-includes a discussion of
uncertainty and variability.
3. Well-balanced risk characterizations present risk
conclusions and information regarding the
strengths and limitations of the assessment at the
level appropriate for the risk assessment.
Also identified in the "Policy for Risk Characterization" are the
following key aspects-of risk characterizations:
1. Risk assessments should be transparent, in that the
conclusions drawn from the science are identified
separately from policy judgments, and the use of
default values or methods and the use of assumptions in
the risk assessment are clearly articulated.
2. Risk characterizations should include a summary of the
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key issue* and conclusions of each of the other
components of the risk assessment/ as well as describe
the likelihood of harm. The summary should include a
description of the overall strengths and limitations
(including uncertainties) of the assessment and
conclusions.
3. Risk characterizations should be consistent in general
format, but recognize the unique characteristics of
each specific situation.
4. Risk, characterizations should include, at least in a
qualitative sense, a discussion of how a specific.risk
and its context compare with other similar risks. This
may be accomplished by comparisons with other chemicals
or situations in. which the Agency has decided to act,
or with other situations familiar to the public. The
discussion should highlight'the limitations of such
comparisons.
5. Risk characterization iar a key component of risk
communication, which is an interactive process
involving exchange of. information and expert opinion
among individuals, groups and-institutions.
Risk assessments .conducted by OSW require different levels
of effort. They should be viewed as. a continuum, because more
than one level of risk assessment effort may be employed for many
osw actions and activities. Risk assessment activities conducted
to support one level of effort may lead to a different level of
effort as the requirements for the assessment and its intended
uses change. The amount of time, effort and level of detail
devoted to risk characterization in OSW should vary according the
nature and magnitude of the risk assessment.
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Representative assessments done in OSW, including the scope
of the assessments and the level of detail, are described below:
a
1. Baseline Risk Assessments for Hazardous Waste .Listing
Determinations. Multimedia assessments to determine
whether certain specified wastes should be listed as
hazardous. Assessments range from conservative
screening level ones to eliminate wastes from further
consideration to more complex ones for .those wastes
which may be listed.
2. other Regulatory Determinations (hazardous waste
identification rule, hazardous waste combustion
emission standards, cement kiln dust regulatory
assessment, etc.)- Complex multimedia assessments to
determine appropriate regulatory strategies, and/or
standards*
3. Site-specific hazardous waste combustion risk
assessments (guidance and assistance to Regions and
States). Multimedia assessments range from screening
level to highly complex, depending on potential risk at
a facility.
III.. Legal Bffecrfc
This implementation guidelines document and associated
guidance..on risk characterization do not establish or affect
legal rights or obligations.. Rather, they confirm the importance
of risk characterization as a component of risk assessment,
outline relevant principles, and identify factors, that staff from
OSW should consider as they implement this policy.
The implementation guidelines and associated guidance do not
stand alone; nor do they establish a binding norm that is finally
F-38
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determinative of the issues addressed. Except where otherwise
provided by law, OSW»s decision on conducting a risk assessment
in any particular case is within OSW's discretion. Variations in
the application of this policy and associated guidance,
therefore, are not a legitimate basis for delaying or
complicating action on OSW or Agency decisions.
IV.
All risk characterizations prepared by OSW in support of
decision making at EPA are covered fay the Administrator's Risk
Characterization Policy., and this implementation • guidelines
document. Discussion of risk in all OSW-generated reports,
presentations, briefings, decision packages, and other documents
should be substantively consistent with .the policy and this
document*
OSW relies largely on Agency positions and documents for
many aspects of its risk assessments. Two key examples are the
IRIS data base and the "Exposure Factors Handbook1*. When
^utilizing this information, OSW depends on whatever is provided
in these documents and data bases. TO the extent that these
Agency sources do not yet meet the fall requirements of the Risk
Characterization Policy, .OSW*s assessments vill have the same
deficiencies. The Agency is working to ensure that these sources
will'be brought, into -compliance with the policy.
Risk assessment.information is often filtered through
several layers of management before reaching the ultimate
decision maker. In OSW, reasons should be given for filtering
out any risk characterization .information during .this process.
It is OSW policy to require that each risk assessor prepare
a risk characterization for each risk assessment. Each risk
assessment prepared by or for this Officeishould contain one or
F-39
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more sections on risk characterization at a level of detail
appropriate for the type of assessment. The risk assessor will
clearly identify the scope of. the assessment and the reason (s),
if any, for not considering certain factors outlined in the
"Elements" document accompanying the Administrator's Risk
Characterization Policy. The guidance to risk assessors, and the
criteria by which they can be judged, on this point, are that
they:
A. Clearly define the scope at tha assessment
1. Note, with a brief explanation, categories of hazard
end-points (including ecotoxicity) that are
specifically excluded from the review.
2. Also note populations which are specifically excluded
from review.
B. Cleanly define tha level of raviey used in fehia assessment:
1. Give an idea of the types and quantity of data sources,
•reviews, and databases that were utilized.
2. If it is an extensive review, it is especially
important to indicate all major sources of information,
and to highlight any major source not utilized with the
reasons why.
Documents that describe components of a risk assessment
(e.g., stand alone hazard or exposure assessments), even if
prepared as separate documents, will also follow the risk
characterization policy in that they .will strive for clarity,
transparency, consistency, and.reasonableness.
Documents related to.risk or any of its components which are
F-40
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submitted to this Office by EPA contractors or other EPA Offices
are expected to follow the Risk Characterization Policy.
It is OSW's policy that documents from sources outside'EPA
that this office relies on in preparation of risk assessments
will be augmented by adding risk characterization language to
meet the requirements of the. Risk Characterization Policy.
It is OSW policy to clearly explain any circumstances where
assessments, and other information such as IRIS, have been
produced in the past by EPA but which do not fully follow the
risk characterization principles. Additional guidance on how the
use of IRIS and other information systems and documents produced
by ORD and others, that serve as inputs to OSW generated'risk
assessments will be developed by the Science Policy Council..
This document will be updated when such guidance im received.
Documents submitted by the public to this Office that relate
to risk assessment or any of its components, including those that
support alternatives to EPA risk assessments, will be evaluated
in light of the Risk Characterisation Policy and this guidelines
document;
OSW will apply the general principles specified in .the Risk
Characterization Policy to its assessments of ecological risk.
Specifically, until detailed Agency guidance becomes available, .
risk characterization*-involving ecological effects developed by
this Program will strive to include a discussion of the strengths
and limitations of. the assessment and will also strive to achieve
the Risk Characterization values of clarity, transparency,
consistency, and reasonableness.
Assessments of benefits are not included in this
Implementation Guidelines. 'Although this Office acknowledges
that the principles of clarity, transparency of process,
F-41
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consistency,, and reasonableness apply also to analyses of
benefits, the Agency has not yet developed guidance for these
types of assessments.
V. Helationaliip of • rialr character jgation to riafc aaseasment and
As stated in the Risk Characterization Policy, "Risk
Characterization is the summarizing step of risk assessment. The
risk characterization integrates information from. the preceding
components of the risk assessment." In other words, risks can be
partially described by the individual components of a risk
assessment, but risk characterization' is a conscious and
deliberate process of bringing all important considerations about
risk into an integrated picture. Even more importantly, as an
integrated picture, the risk characterization is not simply a
reiteration of conclusions of the various components, but a piece
which focusses on how those components interact:.
"Risk characterization" is not synonymous with "risk
communication. The risk characterization policy addresses the
interface between risk assessment and risk management. -Risk
communication, in contrast, .emphasizes the process of exchanging
information and opinion with,, the public. While the final risk
assessment document (including its risk characterization
sections) is available to the public, the risk communication
process is better served by separate risk information documents
desioned for particular audiences.
Therefore, this risk characterization guidelines document is
written to provide guidance to the risk assessor for. his/her use
in explaining the assessment to risk managers. If this guidance
is followed, the resultant risk characterizations should also be
understandable to an educated and motivated layperson.
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Cfi'fcaria tor udging adeanagtr of gi.i aatMT-i.M
The criteria for judging the extent to which osw's risk
characterizations meet the Administrator's four values are
summarized below and further expanded in sections VII and IX of
this document.
A. Clarity of risk characterizations will be judged by the
extent to which:
l. Brevity is achieved and jargon is avoided;
2. The language and .organization of the risk
characterization are understandable to EPA risk
managers and the informed lay person;
3. The purpose of "the risk assessment is defined and
explained (e.g., regulatory purpose, .policy analysis,
priority setting);
4. The level of" effort (e.g. , quick screen, extensive
characterization) put into the assessment is defined
accompanied- by the reason(s) why this- level of effort
was selected;
5. The strengths and .limitations of the assessment can be
understood, without needing to understand the technical
details of the assessment. .To the extent they are
used, technical- terms are defined;
6. The scientific and policy bases, including biases (e.g.
to err on the side of safety), -used in the assessment
are clearly described;
7. Assumptions are defined and. understandable explanations
F43
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are given for each policy decision made for that
particular risk assessment (e.g., use o£ default
assumptions); Agency policy decisions such as. the use
of linearized cancer models are generally not disussed
for each risk assessment; and
8. Unusual issues specific to a particular risk assessment
are fully discussed and explained.
B. Transparency of the process used to characterize risk will
be judged by the extent to which:
1. conclusions drawn from the science and technical
information are identified separately from policy
judgments;
2. The characterizations incorporate the principles of the
risk characterization policy (e.g., the -assumptions are
explained, the strengths and limitations of the
assessment and the "uncertainties are addressed in a
balanced manner);
3. The risk characterization does what it sets out to do
in an appropriate manner (e.g., it meets the expressed
purpose, the level of effort expended was appropriate
for the decision made, all relevant .portions of the
risk assessment paradigm were addressed);
C. The extent to which risk assessment conclusions and risk
characterizations are reasonable will be judged by whether:
1. They are determined to be reasonable by EPA risk
managers and the lay public;
2. All components .are well integrated into an overall
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conclusion of risk which is complete, informative and
useful in decision-making;
3. They are based on the best scientific information and
judgment readily available to OSW, with. sources
documented appropriately;
4. They use common sense and portray the use of science
and science policy to assess risk in a forthright
manner, acknowledging scientific uncertainty;
VIZ
Consistency in definition* and methods of assessing risk is
fundamental to minimizing confusion about risk' estimates
generated across the Agency. OSW attempts to ensure that risk:
assessments/ done within the Off ice are consistent in 'their
general approaches, selection of models, exposure assumptions,
and information sources. Since the state of the art and
availability of information are continually evolving, current
risk assessments may differ -(sometimes considerably) from those*
done in the past.
As indicated previously, there may be significant
differences in the level of detail" and complexity among osW risk
.assessments, depending on the magnitude of the decision, the time
available, and whether- the assessment represents an initial
screening or a more detailed assessment dictated by an initial
screen.
The following procedures used by OSW help to ensure that its
risk characterizations are consistent with characterizations
produced, by other part* of the Agency. They also serve as
criteria by which our success at ensuring consistency can be
judged.
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1. OSW relies on Agency-vide guidelines, such as those for
exposure analyses and health risk assessment.
2. OSW uses Agency-wide information systems, such as the
Integrated Risk Information System (IRIS) and risk
reference concentrations (RfCs) which are produced by
Agency-wide, consensus workgroups.
3. OSW*s risk assessments are done as part of the
development of regulations which require Agency-wide
work groups whose review includes the risk assessments.
4. OSW actively solicits input from other offices with
expertise in specific risk assessment areas; for
example OPPT for structure/activity analyses of
chemicals, ORD for exposure assessment parameters, and
OW for effects on aquatic'lifer.
5. OSW includes substantial input from the Regional
offices, in developing procedure* and guidance for
conducting site-specif ic risk assessments for hazardous
waste combustion facilities.
6. OSW solicits review and assistance from ORD and OPPT
whenever the .office needs to develop toxicity "numbers1*
for chemicals not. on the IRIS data base.
VIII. Jtvaluaiilpg off i.oa»ap«oi.fflg Olroyms'taBoes
The Risk Characterization Policy recognizes that **[t]he
nature of the risk characterization will depend upon the
information available, the regulatory application of the risk
information, and the resources (including time) available.*1 The
types of risk assessment* performed by OSW were described in
Section II. Considerations specific to OSW which affect the
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degree to which risk characterization can be accomplished include
statutory requirements, courtrbrdered deadlines, availability of
data and/or information {e.g., lack of health effects or exposure
data), and amount of resources available to conduct the risk
assessment and risk characterization.
XX.
Poll
The Administrator's March 1995 Risk Characterization package
provides a list of elements to consider when assessing risk to
human health (see appendix). That list of elements will be .used
by OSW. as the basic set of considerations for each risk
assessment and risk characterization that the Office performs,
recognizing also, however., that there will be reasons for
expanding or contracting that: basic set of elements to fit the
circumstances of a particular case. In modifying the- list of
elements, this Office will clearly state in the risk
characterization the reasons for adding to or subtracting
elements from that basic list* Such reasons may be written at a
general level to cover several elements.at once, or may; be
fc • . '
written at a very specific level-to cover a specific element,
• •>
depending on the level of decision being supported.
The following discussion expands on the summarization and
integration aspects of risk characterization, as a supplement to
Part Two of the pElements Documentp provided in the
Administrator's package. The discussion is meant to give further
explanation to risk assessors of the kinds of specific
information that may be relevant to OSW that will help decision-
makers form a clear, coherent, and integrated picture of risk at
the level of detail appropriate for the decision.
This section contains points' to'consider when characterizing
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risk. These points focus on the principles and key aspects of
risk characterization discussed in Part Two of the "Elements
Document". When special circumstances (e.g., lack of data,
resource limitations, statutory deadlines) preclude addressing
particular issues or factors contained in this section, such
circumstances will be explained and their impact on the risk
assessment discussed.
In. .addition to the criteria for clarity, transparency,
consistency and reasonableness discussed earlier in this
document. OSW has adppted the following policy that applies to
.the three principles and six key aspects of Risk characterization
addressed in Section II to help its staff comply with the
Administrator's Risk Characterization Policy. The following
points should help OSH's risk assessors characterize risk. These
points, also provide criteria that can be used by risk managers to
get the most out of risk assessment briefings and to evaluate the
assessor's performance in characterizing risk.
A. Summary of and Coirfj^ dflFlCP i*^ ^TP MiP jog Rialc Conclusions
in preparing risk characterizations for OSW, risk assessors
should present a brief statement of the bottom line of their risk
conclusions in simple clear language. In order to prepare
effective risk characterization*, risk assessors should give a
qualitative idea of the major risks and their confidence in the
estimates of risk and conclusions.
The risk manager should be able to read this and know what
are the major risks (or potential risks y to what individuals and
populations, and have an idea of whether the conclusion is
supported by a large body of data or if there are significant
data gaps. Explain in a qualitative narrative any quantitative
estimation of risk to assure that the reader understands the
meaning of the numbers.
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B. gyj^airy of Key Tsauea
Successful risk characterizations in OSW require that risk
assessors summarize in clear/ concise language the kjx issues,
conclusions, 'and rationale from each stage of the assessment
paradigm (i.e., hazard identification, dose-response evaluation,
exposure assessment, and/or the integration of these
considerations into a risk assessment) .
* IC«Y ig«qe is one that is critical in order to properly
evaluate the stated conclusion. The idea is not to repeat the
entire hazard, or exposure assessment, but to summarize and
identify those pieces of information that were critical to the
evaluation, so that the risk manager will be alerted to the major
issues and conclusions that are the bases of the assessment.
Short conclusion statements from the assessments can be repeated,
or, if the assessment conclusions are lengthy, summarized.
In looking at the whole risk picture there may be issues
which should be brought to the risk manager**; attention. For
example,' isL there a major imbalance in the assessments, such that
there is a strong case for hazard, but lack of data, or oreat
uncertainty for exposure; or vice versa.
Cut dance -ho fcha rimtc aagaBBorai Criteria for judging- how
T fche ehayacfcatH EA. T*iak in thaii* domniianta and brief ina
1. Briefly discuss the key issues from the reports, or data
sources, used to make the risk assessment; and
2. Look at the whole risk picture and bring issues to the.
risk manager's attention. For example', is there a major
imbalance in the assessment, such that there is a
strong case for hazard, but a lack of data, or great .
uncertainty for exposure, or vice versa.
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C. tfethods Used
Standard Agency methodology is generally followed to
generate risk estimates for each category of assessment conducted
by OSW. When quantitative risk evaluations are performed for
OSW, the resultant risk numbers should be narrated qualitatively
to ensure that the reader understands the meaning of the numbers.
When extensive risk assessments are performed, the risk assessor
is likely deviate from using default methodology. Such departures
should be highlighted in the risk characterization.
The mathematics of the risk calculations are not intended to
be fully articulated in the risk characterization. However, the
risk manager should be provided with qualitative "feel11 for the
numbers.
for judging fch» auccetig with which a rialc
tl)t« frfffal*' in brtiafilnq^ *|*d ift wgi-ttftT i
1. Explain the meaning of standard Agency interpretations
of risk values, (e.g., the hazard quotient) if they are
not. explained elsewhere.
2. Explain any specific methodology that might be easily
misinterpreted, (e.g., the use of ecotoxicity
population models)-.
3. If technical data are presented in numerical terms,
qualitatively discuss the data as well. In this regard,
the use of tables and graphics is strongly encouraged,
including sufficiently descriptive titles and
narrative.
D. smmnayv of fche Overall
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Risk Assessment:
. Discuss in qualitative terns, in clear, concise language the
overall quality of the assessment, and the major uncertainties
associated with each of its components. The'idea is to relay to
the risk manager in frank and open terms the strengths and
weaknesses of the assessment.
An example of possible strengths of an assessment would be
that the overall weight of evidence of the data indicates that
the quality and quantity of .data supporting the hazard and/or
exposure is high. There might also be general consensus within
the scientific community on certain points used to build the
hazard/exposure case. The risk manager needs to know the-amount
of uncertainty in each of the assessment areas, and in the final
risk.conclusions.
success in conveying fcVi^ afcy«*nerfc>m anft uncertainties
Rialc Assessment:;
1.. Identify any uncertainties in the "source term"
information.
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a) Identify what: other reasonable alternatives and
conclusions can be derived from the data set.
b) Discuss how other organizations (e.g., industry
and environmental groups) evaluate the risk and
the pros and cons of their evaluations, compared to
EPA's assessment.
5. Kake clear when:
a) precise conclusions cannot be drawn because of
uncertaintyi
b) conclusions may differ because of variation (e.g.,
when children exposed to a chemical are at a
different risk from adults exposed to the same
chemical because of their different
susceptibility);
6. Identify major data,gaps and, .where appropriate,
indicate whether gathering particular data would-add
significantly to the overall certainty of the. risk.
a) With.respect to toxicity information, OSH risk
assessors should ensure that~any significant
limitations.identified in the. Agency data bases
are. presented to the decision makers..
by if a toxicity-. "number11 was generated by OSW,
identify which other EPA- offices were involved in
the development and .review of the number and what
its*limitations are.
7. Indicate where scientific judgments or default
assumptions were used .to bridge information gaps, and
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explain the bases for these judgments/assumptions*
E. Put this Risk Assessment in Context with Ofchfty similar
Because of the potential for public misunderstanding through
inappropriate risk comparisons, "comparative11 risk discussions
(e.g., the risk of dying in a car accident compared to the risk
of dying in a plane crash) should not be 'included as part of the
risk characterization effort. However, risk comparisons can
provide a valuable tool, to risk managers. Thus, where
appropriate, compare this risk . assessment with past Agency
decisions, and decisions by other federal and state agencies, or
other countries on the same chemical. If possible:
l. let the risk manager know how the risks posed .by this
waste or emission agent compares with the risks posed
by similar wastes or emissions OSW has regulated in the
past;
2. describe how; the strengths and weaknesses of this
assessment; .compare with those of previous assessments
used in regulations;
3. let the risk manager know if other risk assessments
have been performed on the waste or emission and .the
results of those assessments, so the manager can view
this assessment in its historical context.
P. ofchei? Tnf onaati-on
Indicate any other information which might bear on the
evaluation of risk within the scope of the assessment. There may
be information that is obvious to the scientist or technical
assessor but not to the risk manager which would assist in making
a risk-based decision. There may. be a need to put scientific
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arguments used in the assessment into a broader context.
OSW will evaluate the success of its risk assessors and risk
characterizations in this regard to the extent they:
1. inform the risk manager whether the key data used for
the assessment is considered experimental, state/of the
art or generally accepted scientific knowledge;
2. include, where appropriate, information which projects
changes in risk under various candidate risk management
alternatives;
3. highlight areas in the assessment which might be
overlooked or misinterpreted by the risk manager; and
4. make it clear that the risk assessment should be used
tp inform the risk management decision, not drive it.
Other factors that may be considered in addition to
risk in arriving, at .the final decision include:
a. Social (e.g., environmental justice)
b. Economic
c. Policy
d. Legal
6* Meeharilfrmg to Bvaltiata Rialc
Management oversight .of OSW's Risk Characterization Policy
is required: to ensure compliance with the policy, to evaluate its
success, and to make necessary improvements. The. actions OSW
will take to establish effective mechanisms for implementing,
evaluating and . improving its risk characterization 'guidelines
are:
1. Provide Information to risk assessors about what
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information to present to risk managers.
2. Develop a system, with internal reviewers, independent
from the risk, assessor preparing the information, to
ensure that each risk assessment contains a risk
characterization consistent with this policy.
3. Conduct periodic reviews of the risk characterization
portions of the assessments thereafter.
Z. statement of Commitment
Through this Implementation Guidelines document; OSW intends
to ensure that risk characterizations produced by and for the
Office will be substantially consistent with these guidelines and
with Agency guidance and policy on risk characterization,
recognizing limitations in time and resources. The guidelines
will be updated as-necessary.
Director, office of solid Waste Date
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F-56
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JiflJpERFUND ASSESSMENT PROCESS
The Superfund program responds to "releases" of hazardous substances into the environment.
"Releases" include the improper disposal of hazardous substances as well as leaks from storage
tanks and spills due to transportation accidents. The Superfund program uses the following
phased approach to investigate hazardous waste sites:
Preliminary Assessment (PA^
o Review federal, state, and local government permit and judicial files
o Interview federal, state and local government personnel
o Examine records regarding past and present ownership and use of the property
o Analyze available geological, topographical, and hydrogeological data
o Visually inspect the site when possible
Site Inspection (SD
o Collect limited she-specific data to determine the nature of the release (usually not more
than 30 samples including background and QA) *
o Identify potential exposure pathways and receptors
o Evaluate data to determine whether the she should be considered a candidate for cleanup
o Perform emergency removal if the release is considered an inmediate threat to human
heahh or the environment
o Identify potentially responsible parties
o Propose site for inclusion on the National Priorities List (NPL). Findings subject to notice
and comment.
Remedial
o Sample to fully characterize the nature and extent of contamination
o Evaluate if she media are contaminated above appticable Federal and State standards
o Perform Baseline Risk Assessment
Evaluate current and potential future exposures
Supports the decision whether to take remedial action
Documents the magnitude of site risk and hs primary sources
Supports the selection of cleanup levels
o * *** ^
Hazard Identification
Extensive analytical sampling data reviewed
Chemicals of greatest concern selected based on their concentration, toxidty,
mobility, persistence and bioavailabilhy
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Dose-response Assessment
Rety heavily oil toxicity assessments developed by ORD
Adjustments made to site-specific estimates of dose for certain chemicals based on
bioavailability
Exposure Assessment
Emphasis on chronic/long-term average exposures
Exposure point concentrations derived from both sampling data and models
Quality and quantity of data documented
Exposure descriptors most commonly addressed are central tendency and high-end
individual risk (e.g., reasonable maximum exposure; RME), and highly exposed
subpopulations (e.g., childhood exposure to soil)
Cumulative exposure addressed as likelihood of an individual being exposed to
multiple chemicals in the same medium or across media
Description of Site Risk
Estimates of cancer and non-cancer risks traditionally reported as a single number
for each exposure described
Assumptions used in the assessment clearly documented
Uncertainties primarily addressed qualitatively
Superfund regulation directs that she managers focus on risks to the RME
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DRAFT—DO NOT COPY, DISTRIBUTE, OR QUOTE.
APPENDIX G
RISK CHARACTERIZATION POLICY BACKGROUND MATERIALS
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RISK CHARACTERIZATION BACKGROUND MATERIALS
EPA ADMINISTRATOR BROWNERS MARCH 21, 1995
MEMO
POLICY FOR RISK CHARACTERIZATION AT EPA
GUIDANCE FOR RISK CHARACTERIZATION
G-l
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G.-2
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. O.C. 20440
THe_ ADMINISTRATOR
MAR 2 1 1SS5
MEMORANDUM
SUBJECT: EPA Risk Characterization Program
TOi Assistant Ann HI iifti aim l'
tatnXDIStraXOd
Artmypi ^ y ^ *MT
General Counsel
Inspector GeaenI
EPA has achieved significant poflutioa reduction qytf the p«t 20 yean, but the challenges
Mtay more people «r aware of
enviroomenal issues today tbaa intbe past snd their kvd of jopbistialioo and interest ia
understanding these issues cootmuec to ineretie. We DOW work with a populace which is not
only interested k knowing whut EPA timkB about i particular issue; but also how wecoene to
OUT
More ajKiincce key suu:dx?M<»mcmiuuiUiieiitalisaueaw^
allow then to indcpendeotfytsaess fff* *T**T j*nf£nt*ii^f ****sirt **** tfgr'^'^ff"* of environniental
ductioo atlioui. If we are to soccced aod build our
credibflay and stature as a letter ia eovironmeatal prot»ca« forth* neat century, EPA, must be
chaflengta of ecvtronnyntal declaoniulring in the Sice of Kaentific uncertainty.
Asth«iawe»wefiK«becoa)enx)reccwiplex,pieoptebc^insk^
better understajBd the baas for our decisions, as weft as our confidence in the data, the scieoce
DoUcyjiidgnieatj we ha^e m§de,and the uncertainty in them In order to achieve
this better understanding, we must improve the way in which w« characterize and connnumcaie
environmental risk. We niistenjhricecerumnjndanientil values
G-3
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-2-
» that we may begin the process of cfatngiiig the way in w^
public, and key tttkrholdgrs on environmental risk issues. I need your hdp to ensure that these
values ire embraced tad that we change the nay we do busmen.
First, we must idopt as values transparency in our decisku&naJdng process and darky in
communication with etch other and the pobfic regarding eovinxnDisitalri^mdtheuocertunties
with our a wtvivfiHs of environmental rislc Tlus means that we must futty, openly,
and dearly cfaancterize risks. T™» tw» «^«m»«t^ «rv.iy«««
poScfei 'wfaich undofio our dcosboS'ts they STB made throughout tt*f
engaged in the $decti«a of science policy options, and that their choices aad the rationale fbr
«"
znay be CCTKTTTt^f ibo*jt
expect that we wffl see nx«cfaaneog^puttculiriy at first Howcrvtr, Istroogiybdievethat
«
pajticipa&oo, better uiux nation for 4ff^v*v*rt"em^. unproved n^otionsy and more puohc support
and respect for EPA positions and decisions. There is value in sharing with others the
.trmg daAfriiM m rfm Aea af i uw*« ulniy I VJCW making
this change as esseonai to the loag.tenn success of this Agency.
Clarity is communication also means that we wffl strive to help the pubGc put
envtroanentalriskmtfaepioperpqspe^vewfaenwetaJte We most
meet *^*t A*II**WI «fiii fcfi Ifffjttmatf ^"lyt tff h^p the pibfic Hf^tfrco1"^**1*^ tfcg rtMf^?
sigmficawe of environmental riski,
m decisk}nflu&i^
1*^1 tr> tm^Mi ^t»^U> /pu^tu^.;^ ^f ^~ .^imipriftfi* MM! MJ^JJMI poKr^*, w» tnmt hft more
ingflatit ahnnfr *>fffnnrg tM ^r CTtrf Hflnnitt""1* i™* «ffWig* poltaa* ar^ Maairtgnt and
cdrnparabieaooesorogram^wefl grounded in 'sdeo^aodthitt^ Aithin i 'zone of
G-4
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-3-
While I believe that the American public expects us to err on the side of protection in the face of
sriamifi^ imr»Ttflpijy T ppf q^T* "T a^«o^j»ert< tq hg imrfaKjtfajfty CQPSfTVatiye- We CanOOt
lead the fight for. environmental protection into the next century unless we use common sens* in
all we do.
These core values of transparency, darity, consistency, and reasonableness need to guide
each of us in our day-to-day work; from the lexicologist reviewing the indrvidual cancer study, to
fhe exposure und risk assessors, to tfag risk fn*itj|fl*ir, *"^ through to the \iMmity decisionmaker. I
recognize that Hfrf^g *fiif BMIBO will not by itself result in any f^v9^_ You ncfd to believe in the
importance of this change and convey your beliefs to your numagen and staff through your words
and actions in order for the change to occur. You also need to pUy an integral role in developing
the.implementmg policies and procedures lor your programs.
issuing the attached I&A!^ I view
these documents as building blocks for the development of your program-specific policies and
procedures. The Science PoBcy Council (SPQ plans to adopt the same basic approach to
implementation as was used for Peer Review. That is, the Council win form an Advisory Group
that wffl work with A broad Implementation Team made up of representatrves from every Program
OfSce and Regioa Each Program Office and each Region wiD be asked by the Advisory Group
to develop program and region-specific poficies and procedures for risk chanctmTation
consistent with the values of traaspaureaey, cuuity, consistency, and feasomjJbleaess and
consistent with the nfflchfd poficyand guidsnce.
I recognize that as you develop your Program^ecinc policies and prc
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March 1995
POLICY FOR RISK CHARACTERIZATION
at the U.S. Environmental Protection Agency
INTRODUCTION
Many EPA policy decisions are based in part on the results of risk assessment, an
analysis of scientific information on existing and projected risks to human health
and the environment As practiced at EPA/ risk assessment makes use of many
different kinds of scientific concepts and data (e.g., exposure, toxicity, epidemiology,
ecology), all of which are used to "characterize!' the expected risk associated with a
particular agent or action in a particular environmental context. Informed use of
reliable scientific information from many different sources is a central feature of the
risk assessment process.
Reliable information may or may not be available for many aspects of a risk
assessment. Scientific uncertainty is a fact of life for the risk assessment process, and
agency managers almost always must make decisions using assessments that are not
as definitive in all important areas as would be desirable. They therefore need to
understand the strengths and the limitations of each assessment, and to
communicate this information to all participants and the public.
This policy reaffirms the principles and guidance found in the Agency's 1992 policy
(Guidance on Risk Characterization for Risk Managers and Risk Assessors, February
26,1992). That guidance was based on EPA's risk assessment guidelines, which are
products of peer review and public comment. The 1994 National Research Council
(NRC) report, "Science and Judgment in Risk Assessment/' addressed the Agency's
approach to risk assessment/ including the 1992 risk characterization policy. The
NRC statement accompanying the report stated, "... EPA's overall approach to
assessing risks is .fundamentally sound despite often-heard criticisms, but the
Agency must more clearly establish the scientific and policy basis for risk estimates
and better describe the uncertainties in its estimates of risk"
This policy statement and associated guidance for risk characterization is designed to
ensure that critical information from each stage of a risk assessment is used in
forming conclusions about risk and that this information is communicated from
risk assessors to risk managers (policy makers), from middle to upper management,
and from the Agency to the public. Additionally, the policy will provide a b? .Is for
greater clarity/ transparency,, reasonableness/ and consistency in risk assessments
across Agency programs. While most of the discussion and examples in this policy
are drawn from health risk assessment/ these values also apply to ecological risk
assessment. A parallel effort by the Risk Assessment Forum to develop EPA
ecological risk assessment guidelines will include guidance specific to ecological risk
characterization.
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Policy Statement
Each risk assessment prepared in support of derision-making at EPA should
include a risk characterization that follows die principles and reflects the values
outlined in this policy. A risk characterization should be prepared in a manner that
is clear, transparent, reasonable and consistent with other risk characterizations of
similar scope prepared across programs .in the Agency. F 'rther, discussion of risk in
all EPA reports, presentations, decision packages, and other document should be
substantively consistent with the risk characterization. The nature of the risk
characterization will depend .upon the information available, the regulatory
application of the risk information, and the resources (including time) available. In
all. cases, however, the assessment should identify and discuss all the major issues
associated with detenruning the nature and extent of the risk and provide
commentary on any constraints limiting fuller exposition.
Key_A.$p_ec.ts,o£Risk Characterization
Bridging risk assessment and risk management. As the interface between risk
assessment and risk management, risk characterizations should be clearly presented,
and separate from any risk management considerations. Risk management options
should be developed using the risk characterization and should be based on
consideration of all relevant factors, scientific and nonscientific.
Discussing confidence and uncertainties. Key scientific concepts, data and
methods (e.g., use of animal or human data for extrapolating from high to low
doses, use of pharmacokinetics data, exposure pathways, sampling methods,
availability of chemical-specific information, quality of data) should be discussed:
To ensure transparency, risk characterizations should include a statement of
confidence in the assessment that, identifies all ma/or uncertainties along with
comment on their influence on the assessment, consistent with the Guidance on
Risk Characterization (attached).
Presenting several types o£ risk information. Information should be
presented on the range of exposures derived from exposure scenarios and on the use
of multiple risk descriptors (e.g., central tendency, high end of individual risk,
population risk/ important subgroups, if known) consistent with terminology in* the
Guidance on Risk Characterization, Agency risk assessment guidelines, and
program-specific guidance. In decision-making, risk managers should use risk
information appropriate to their program legislation.
EPA conducts many types of risk assessments, including screening-level
assessments of new chemicals, in-depth assessments of pollutants such as dioxin
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and environmental tobacco smoke, and site-specmc assessments for hazardous
waste sites. An iterative approach to risk assessment, beginning with screening
techniques, may be used to determine if a more comprehensive assessment is
necessary. The degree to which confidence and uncertainty are addressed in a risk
characterization depends largely on the scope of the assessment. In general, the
scope of the risk characterization should reflect the information presented in the
risk assessment and program-specific guidance. When special circumstances (e.g.,
lack of data, extremely complex situations, resource limitations," statutory deadlines)
preclude a full assessment, such circumstances should be explained and their impact
on the risk assessment discussed.
Risk Characterization in Context
Risk assessment is based on a series of questions that the assessor asks about
scientific information that is relevant to human and/or environmental risk. Each
question calls for analysis and interpretation of the available studies, selection of the
concepts and data that are most scientifically reliable and most relevant to the
problem at hand, and scientific conclusions regarding the question presented. For
example, health risk assessments involve the following questions:
Hazard Identification — What is known about the capacity of an environmental
agent for causing cancer or other adverse health effects in humans, laboratory
animals, or wildlife species? What are the related uncertainties and science
policy choices?
Dose-Response Assessment - What is known about the biological mechanisms
and dose-response relationships underlying any effects observed in the laboratory
or epidemiology studies providing data for the assessment? What are the
related uncertainties and science policy choices?
Exposure Assessment - What is known about the principal paths, patterns, and
magnitudes of human or wildlife exposure and numbers of persons or wildlife
species likely to be exposed? What are the related uncertainties and science
policy choices?
Corresponding principles and questions for ecological risk assessment are being
discussed as part of the effort to develop ecological risk guidelines.
Risk characterization is the summarizing step of risk assessment The risk
characterization integrates information from the. preceding components of the risk
assessment and synthesizes an overall conclusion about risk that is complete,
informative and useful for dedsiorunakers.
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Risk characterizations vhould clearly highlight both the. confidence and the
uncertainty associated with the risk assessment. For example, numerical risk
estimates should always be accompanied by descriptive information carefully
selected to ensure an objective and balanced characterization of risk in risk
assessment reports and regulatory documents. In essence, a risk characterization
conveys the assessor's judgment as to the nature and existence of (or lack of) human
health or ecological risks. Even though a risk characterization describes limitations
in an assessment, a balanced discussion of reasonable conclusions and related
uncertainties enhances, rather than detracts, from the overall credibility of each
assessment.
"Risk characterization" is not synonymous with "risk communication." This
risk characterization policy addresses the interface between risk assessment and risk
management. Risk communication, in contrast, emphasizes the process of
exchanging information and opinion with the public - including individuals,
groups, and other institutions. The development of a risk assessment may involve
risk communication. For example, in the case of site-specific assessments for
hazardous waste sites, discussions with the pubLL may influence the exposure
pathways included in the risk assessment.. While the «nal risk assessment
document (including the risk characterization) is available to the public, the risk
communication process may be better served by separate risk information
documents designed for particular audiences.
Promoting Clarity. Comparability and Consistency
There are several reasons that the Agency should strive for greater clarity,
consistency and comparability in risk assessments. One reason is to minimize
confusion. For example, many people have not understood that a risk estimate of
one in-a million for an "average" individual is not comparable to another one in a
million risk estimate for the "most exposed individual." Use of such apparently
similar estimates without .further explanation leads to misunderstandings about the
relative significance of risks and the protectiveness of risk reduction actions.
EPA's Exposure-Assessment Guidelines provide standard descriptors of
exposure and risk. Use of these terms in all Agency risk assessments will promote
consistency and' comparability. Use of several descriptors/ rather than a single
descriptor, will enable EPA to present a fuller picture of risk that corresponds, to the
range of different exposure conditions encountered by various individuals and
populations exposed to most environmental chemicals.
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Legal Effect
This policy statement and associated guidance on risk characterization do not
establish or affect legal rights or'obligations Rather, they confirm the importance of
risk characterization as a component of risk assessment outline relevant principles,
and identify factors Agency staff should consider in implementing the policy.
The policy and associated guidance do not stand alone; nor do they establish a
binding norm that is finally determinative of the issues addressed. Except where
otherwise provided by law, the Agency's decision on conducting a risk assessment in
any particular case is within the Agency's discretion. Variations in the application
of the policy and associated guidance, therefore, are not a legitimate basis for
delaying or complicating action on Agency decisions.
Applicability
Except where otherwise provided by law and subject to the limitations on the
policy's legal effect discussed above, this policy applies to risk assessments prepared
by EPA and to risk assessments prepared by others that are used in support of EPA
decisions.
EPA will consider the principles in this policy in evaluating assessments
submitted to EPA to complement or challenge Agency assessments. Adherence to
this Agency-wide policy will improve understanding of Agency rrk assessments,
lead to more informed decisions, and heighten the credibility of both assessments
and decisions.
Implementation
Assistant Administrators and Regional Administrators are responsible for
implementation of this policy within their organizational units. The Science Policy.
Council (SPC) is organizing Agency-wide implementation activities. Its
responsibilities include promoting consistent interpretation, assessing Agency-wide
progress, working with external groups on risk characterization issues and methods,
and developing recommendations for revisions of the policy and guidance, as
necessary.
Each Program and Regional office will develop office-specific policies and
procedures for risk characterization that are consistent with this policy and the
associated guidance. Each Program and Regional office-will designate a risk
• manager or risk assessor as the office representative to the Agency-wide Implementa-
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tion Team, which will coordinate development of office-specific policies and
procedures and other implementation activities. !The SPC will also.designate a
small cross-Agency Advisory Group that will serve as the liaison between the SPC
and the Implementation Team.
In ensuring coordination and consistency among EPA offices, the
Implementation Team will take into account statutory and court deadlines, resource
implications, and existing Agency and program-specific Guidance on risk
assessment. The group will work closely with staff throughout Headquarters and
Regional offices to promote development of risk characterizations that present a full
and complete picture of risk that meets the needs of the risk managers. .
//^L^^y^X/y MAR 2 t 1335
APPROVED: 'Lfrt&K^ 6fSt\£J**A*<)y^*^—' DATE:
Carol M. Brown^t, Administrator
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GUIDANCE
FOR
RISK CHARACTERIZATION
U.S. Environmental Protection Agency
Science Policy Council
February, 1995
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CONTENTS
I. The Risk Assessment-Risk Management Interface
II. Risk Assessment and Risk Characterization
III. Exposure and Risk Descriptors
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PREFACE
This guidance contains principles for developing and describing EPA risk
assessments, with a particular emphasis on risk characterization. The current
document is an update of the guidance issued with the Agency's 1992 policy
(Guidance on Risk Characterization for Risk Managers and Risk Assessors, February
26,1992). The guidance has not been substantially revised, but includes some
clarifications and changes to give more prominence to certain issues, such as the
need to explain the use of default assumptions.
As in the 1992 policy, some aspects of this guidance focus on cancer risk
assessment, but the-guidance applies generally to human health effects (e.g.,
neurotoxicity, developmental toxicity) and, with appropriate modifications, should
be used in all health risk assessments. This document has not been revised to
specifically address ecological risk assessment, however, initial guidance for
ecological risk characterization is included in EPA's Framework for Ecological Risk
Assessments (EPA/630/R-92/001). Neither does this guidance address in detail the
use of risk assessment information (e.g., information from the Integrated Risk-
Information System (IRIS)) to generate site- or media-specific risk assessments.
Additional program-specific guidance will be developed to enable implementation
of EPA's Risk Characterization Policy. Development of such guidance will be
overseen by the Science Policy Council and will involve risk assessors and risk
managers from across the Agency.
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L THE RISK ASSESSMENT-RISK MANAGEMENT INTERFACE
Recognizing that for many people the term risk assessment has wide meaning, the
National Research Council's 1983 report on risk assessment in the federal
government distinguished between risk assessment and risk management.
"Broader uses of the term [risk assessment] than ours also embrace analysis of
perceived risks, comparisons of risks associated with different regulatory
strategies, and occasionally analysis of the economic and social implications of
regulatory decisions — functions that we assign to risk management
(emphasis added). (1)
In 1984, EPA endorsed these distinctions between risk assessment and risk
management for Agency use (2), and later relied on them in developing risk
assessment guidelines (3). In 1994, the NRC reviewed the Agency's approach to and
use of risk assessment and. issued an extensive report on their findings (4). This
distinction suggests that EPA participants in the process can be grouped into two
main categories, each with somewhat different responsibilities/based on their roles
with respect to risk assessment and risk mr.nag3ment.
A. Roles of Risk Assessors and Risk Managers
Within the Risk Assessment category there is a group that develops chemical-
specific risk t-jsessments by collecting, analyzing, and synthesizing scientific data to
produce the hazard identification, dose-response, and exposure assessment portion
of the risk assessment and to characterize risk. This group relies in part on Agency
risk assessment guidelines to address science policy, issues and scientific
uncertainties. Generally, this group includes scientists and statisticians in the Office
of Research and Development; the Office of Prevention, Pesticides and Toxics and
other program offices; the Carcinogen Risk Assessment Verification Endeavor
(CRAVE); and the Reference Dose (RfD) and Reference Concentration (RfC)
Workgroups. .
Another group generates site- or media-specific risk assessments for use in
regulation development or site-specific decision-making. These assessors rely on
existing databases (e.g., IRIS, ORD Health Assessment Documents, CRAVE and
RfD/RfC Workgroup documents, and program-specific toxiciry information) and
media- or site-specific exposure information in developing risk assessments. This
group also relies in part on Agency risk assessment guidelines and program-specific
guidance to address science policy issues and scientific uncertainties. Generally, this
group includes scientists and analysts in program offices, regional offices, and the
Office of Research and Development.
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Risk managers, as a separate category, integrate the risk characterization with other
considerations specified in applicable statutes to make." and justify regulatory
decisions. Generally, this group includes Agency managers and decision-makers.
Risk managers also play a role in determining the scope of risk assessments. The
risk assessment process involves regular interaction between risk assessors and risk
managers, with overlapping responsibilities at various stages in the overall process.
Shared responsibilities include initial decisions regarding the planning and conduct
of an assessment, discussions as the assessment develops, decisions regarding new
data needed to complete an assessment and to address significant uncertainties. At
critical junctures in the assessment, such consultations shape the nature of, and
schedule for, the assessment. External experts and members of the public may also
play a role in determining the scope of the assessment; for example, the public is
often concerned about certain chemicals or exposure pathways in the development
of site-specific risk assessments.
B. Guiding Principles
The following guidance outlines principles for tL_je who generate, review, u^e, and
integrate risk assessments for .decision-making.
1. Risk assessors and risk managers should be sensitive to distinctions between
risk assessment and risk management.
The major participants in the risk assessment process have many shared
responsibilities. Where responsibilities differ, it is important that participants
confine themselves to tasks in their areas of responsibility and not inadvertently
obscure differences between risk assessment and risk management.
For the generators of the assessment, distinguishing between risk assessment and
risk management means that scientific information is selected, evaluated, and
presented .without considering issues such as cost, feasibility, or how the scientific
analysis might influence the regulatory or site-specific decision. Assessors are
charged with (1) generating a credible, objective, realistic, and scientifically balanced
analysis; (2) presenting information on hazard, dose-response, exposure and risk;
and (3) explaining confidence in each assessment by clearly delineating strengths,
uncertainties and assumptions, along with the impacts of these factors (e.g.,
confidence limits/ use of conservative/non-conservative assumptions) on the
overall assessment They do not make decisions on the acceptability of any risk
level for protecting public health or selecting procedures for reducing risks.
For users of the assessment and for decision-makers who integrate these
assessments into regulatory or site-specific decisions', the distinction between risk
assessment and risk management means refraining from influencing the risk
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description through consideration of other factors — e.g., the regulatory outcome -
and from attempting- to shape the risk assessment to avoid statutory constraints,
meet regulatory objectives/ or serve political purposes. Such management
considerations are often legitimate considerations for the overall regulatory decision
(see next principle), but they have no rcle in estimating or describing risk.
However, decision-makers and risk assessors participate in an Agency process that
establishes' policy directions that determine the overall nature and tone of Agency
risk assessments and, as appropriate, provide policy guidance on difficult and
controversial risk assessment issues. Matters such as risk assessment priorities,
degree of conservatism, and acceptability of particular risk levels are reserved for
decision-makers who are charged with making decisions regarding protection of
public health.
2. The risk assessment product, that is, the risk characterization, is only one of
several kinds of. information used for regulatory decision-making.
Risk characterization, the last step in risk assessment, is the starting point for risk
management considerations and the foundation for regulatory decision-making, but
it is only one of several important components in such decisions. As the last step in
risk assessment, the risk characterization identifies and highlights the noteworthy
risk conclusions and related uncertainties. Each of the environmental laws
administered by EPA calls for consideration of other factors at various stages in the
regulatory process. As authorized by differ- nt statutes, decision-makers evaluate
technical feasibility (e.g., treatability, detection limits), economic, social, political, and
legal factors as part .of the analysis of whether or not to regulate and, if so, to what
extent. Thus, regulatory decisions are usually based on a combination of the
technical analysis used to develop the risk assessment and information from other
fields.
For this reason, risk assessors and managers should understand that the regulatory
decision is usually not determined solely by the outcome of the risk assessment. For
example, a regulatory decision on the use of a particular pesticide considers not only
the risk level to affected populations, but also the agricultural benefits of its use that
may be important for the nation's food supply. Similarly, assessment efforts may
produce an RfD for a particular chemical, but other considerations may result in a
regulatory level that is.more or less protective than the RfD itself.
For decision-makers, thi$ means that societal considerations (e.g./ costs and benefits)
that, along with the risk assessment, shape the regulatory decision should be
described as fully as the scientific information set forth in the risk characterization.
Information on data sources and analyses, their strengths and limitations,
confidence in the assessment, uncertainties, and alternative analyses are as
important here as they are for the scientific components of the regulatory decision.
Decision-makers should be able to expect, for example, the same level of rigor from
the economic analysis as they receive from.the risk analysis. Risk management
decisions involve numerous assumptions and uncertainties regarding technology,
economics and social factors, which heed to be explicitly identified for the
decision-makers and the public.
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U. RISK CHARACTERIZATION
A. Defining Risk Characterization in the Context of Risk Assessment
EPA risk assessment principles and practices draw on many sources. Obvious
sources include the environmental laws administered by EPA, the National
Research Council's 1983 report on risk assessment (1), the Agency's Risk Assessment
Guidelines (3), and various program specific guidance (e.g., the Risk Assessment
Guidance for Superfund). Twenty years of EPA experience in developing,
defending, and enforcing risk assessment-based regulation is another. Together
these various sources stress the importance of a clear explanation of Agency
processes for evaluating hazard, dose-response, exposure, and.other data that
provide the scientific foundation for characterizing risk.
This section focuses on two requirements for full characterization of risk. First, the
characterization should address qualitative and quantitative features of the . .
assessment. Second, it should identify the important strengths and uncertainties in
the assessment as part of a discussion of the confidence in the assessment. This
emphasis on a full description of all elements of the assessment draws attention to
the importance of the qualitative, as well as the quantitative, dimensions of the
assessment. The 1983 NRC report carefully distinguished qualitative risk
assessment from quantitative assessments, preferring risk statements that are not
strictly numerical. •
The term risk assessment-is often given narrower and broader meanings
than we have adopted here. For some observers, the term is synonymous
with quantitative risk assessment and emphasizes reliance on numerical
results. Our broader definition includes quantification, but also includes
qualitative expressions of risk. Quantitative estimates of risk are not always
feasible, and they may be eschewed by agencies for policy reasons. (1)
EPA's Exposure Assessment Guidelines define risk characterization as the final step
in the risk assessment process that
• Integrates the individual characterizations from the hazard identification, dose-
response, and exposure assessments;
• Provides an evaluation of the overall quality of the assessment and the degree
of confidence the authors have in the estimates of risk and conclusions drawn;
• Describes risks to individuals and populations in terms of extent and severity of
probable harm; arid
• Communicates results of the risk assessment to the risk manager. (5)
Particularly critical to full characterization of risk is a frank and open discussion of
the uncertainty in the overall assessment and in each of its components. The
uncertainty discussion is important for several reasons.
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1. Information from different sources, carries different-kinds of uncertainty and
knowledge of these differences is important when uncertainties are combined
for characterizing risk.
2. Tae risk assessment process, with management input, involves decisions
regarding the collection of additional data (versus living with uncertainty); in
the risk characterization, a discussion of the uncertainties will help to identify
where additional information could contribute significantly to reducing
uncertainties in risk assessment.
3. A clear and explicit statement of the strengths and limitations of a risk
assessment requires a clear and explicit statement of related uncertainties.
A discussion of uncertainty requires comment £n such issues as the quality and
quantity of available data, gaps in the data base for specific chemicals, quality of the
.measured data, use of default assumptions, incomplete understanding of general
biological phenomena, and scientific judgments or science policy positions that were
employed to bridge information gaps.
In short, broad agreement exists on the importance of a full picture of risk,
particularly including a statement of confidence in the assessment and the
a. .-ocia'-ed uncertainties. This section disc1' •" *s information content and uncertainty
aspects of risk characterization, while Section ffl discusses various descriptors used
in risk characterization.
B. Guiding Principles
1. The risk characterization integrates the information from the hazard
identification, dose-response, and exposure assessments, using a combination of
qualitative information, quantitative information, and information regarding
uncertainties.
Risk assessment is based on a series of questions that the assessor asks about the data
and the implications of the data for human risk. Each question calls for analysis and
interpretation of the available studies, selection of the data that are most
scientifically reliable and most relevant to the problem at hand, and scientific
conclusions regarding, the question presented. As suggested below, because the
questions and analyses are complex, a complete characterization includes several
different kinds of information, carefully selected for reliability and relevance.
a. tfgzard Identiftcatigrj ~ What is Hiown about the capacity of an environmental
agent for causing cancer (or other adverse effects) in humans and laboratory
animals?
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Hazard identification is a qualitative description based on factors such as the kind
and quality of data on humans or laboratory animals, the availability of ancillary
information (e.g., structure-activity analysis, genetic toxicity, pharmacokinetics)
from other studies, and the weight-of-the-evidence from all of these data sources.
For example, to develop this description, the issues addressed include:
1) the nature, reliability, and consistency of. the particular studies in humans and
in laboratory animals;
2) the available information on the mechanistic basis for activity; and
3) experimental animal responses and their relevance to human outcomes.
These issues make clear that the task of hazard identification is characterized by
describing the .full range of available information and the implications of that
information for human health.
b. Dose-Response Assessment ~ What is known about the biological mechanisms
and dose-response relationships underlying any effects observed in the
laboratory or epidemiology studies providing data for the assessment?
The dose-response assessment examines qvnti'ative relationships between
exposure (or dose) and effects in the studies used to identify and define effects of
concern. This information is later used along with "real world" exposure
information (see below) to develop, estimates of the likelihood of adverse effects in
populations potentially at risk. It should be noted that, in practice, hazard
identification for developmental toxicity and other non-cancer health effects is
usually done ir conjunction with an evaluation of dose-response relationships,
since the determination of whether there is a hazard is often dependent on whether
a dose response relationship is present. (6) Also, the framework developed by EPA
for ecological risk assessment does not distinguish between hazard identification
and dose-response assessment, but rather calls for a "characterization of ecological
effects." (7)
Methods for establishing dose-response relationships often depend on various
assumptions used in lieu of a-complete data base, and the method chosen can
strongly influence the overall assessment. The Agency's risk assessment guidelines
often identify so-called "default assumptions" for use in the absence of other
information. The risk assessment should pay careful attention to the choice of a
high-to-low dose extrapolation procedure. As a result, an assessor who is
characterizing a dose-response relationship considers several key issues:
1) the relationship between extrapolation models selected and available
information on biological mechanisms;
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2) how appropriate data sets were selected from, those that show the range of
possible potencies both in laboratory animals and humans;
3) the basis for selecting interspecies dose scaling factors to account for scaling
doses from experimental animals to humans;
4) the correspondence between the expected route(s) of exposure and the exposure
route(s) utilized in the studies forming the basis of the dose-response
assessment as well as the interrelationships of potential effects from different
exposure routes;
5) the correspondence between the expected duration of exposure and the
exposure durations in the studies used in forming the basis of the dose-response
assessment, e.g., chronic studies would be used to assess long-term, cumulative'
exposure concentrations/ while acute studies would be used in assessing peak
levels of exposure; and
6) the potential for differing susceptibilities among population subgroups.
The Agency's Integrated Risk Information System (IRIS) is a repository for such
information, for EPA. EPA program offices also maintain program-specific
databases, ruch as the OSWER Health Effec' ".Assessment Summary Tables (HEAST).
IRIS includes data summaries, representing Agency consensus on specific chemicals,
based on a careful review of the scientific issues listed above. For specific risk.
assessments based on data from any source, risk assessors should carefully review
the information presented, emphasizing confidence in the data and uncertainties
(see subsection 2 below). Specifically, when IRIS data are used, the xRIS statement of
confidence should be included as an explicit part of the risk characterization for
hazard and dose-response information.
c. Exposure Assessment — What is known about the principal paths, patterns, and
magnitudes of human exposure and numbers of persons who may be exposed?
The exposure assessment examines a wide range of exposure parameters pertaining
to the environmental scenarios of people who may be exposed to the agent under
study. The information considered for .the exposure assessment includes
monitoring studies of chemical concentrations in environmental media, food, and
other materials; modeling of environmental fate and transport of contaminants;
and information on different activity patterns of different population subgroups.
An assessor who characterizes exposure should address several issues:
1) The basis for the values and input parameters used for each exposure scenario.
If the values are based on data, there should be a discussion of the quality,
purpose, and representativeness of the database. For. monitoring data, there
should be a discussion of the data tjuality objectives as they are relevant to risk
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assessment, including the appropriateness of the analytical detection limits. If
models are applied, the appropriateness of the models and information on their
validation should be presented. When assumptions are made, the sour.ce and
general logic used to develop the assumptions (e.g., program guidance, analogy,
professional judgment) should be described.
2) The confidence in the assumptions made about human behavior and the
relative likelihood of the different exposure scenarios.
3) The major factor or factors (e.g., concentration, body uptake, duration/frequency
of exposure) thought to account for the greatest uncertainty in the exposure
estimate, due either to sensitivity or lack of data.
4) The link between the exposure information and the risk descriptors discussed
in Section EH of this Appendix. Specifically, the risk assessor needs to discuss
the connection between the conservatism or non-conservatism of the
data/assumptions used in the scenarios and the choice of descriptors.
5) Other information that may be important for the particular risk assessment
For example, for many assessments, other sources and background levels in the
environment may contribute significantly to population exposures and should
He discussed.
2) The risk characterization includes a discussion of uncertainty and variability.
In the risk characterization, conclusions about hazard and dose response are
integrated with those from the exposure assessment. Irt addition, confidence about
these conclusions, including information about the uncertainties associated with
each aspect of the assessment in the final risk summary, is highlighted. In the
previous assessment steps and in the risk characterization, the risk assessor must
distinguish between variability and uncertainty.
Variability arises fr 'in true heterogeneity in characteristics such as dose-response
differences within a population, or differences in contaminant levels in the
environment The values of some variables used in an assessment change with
time and space, or across the population whose exposure is being estimated.
Assessments should address the resulting variability in doses received by members
of the target population. Individual exposure, dose, and risk can vary widely in a
large population. The central tendency and high end individual risk descriptors
(discussed in Section in below) are intended to capture the variability in exposure,
lifestyles, and other factors that lead to a distribution of risk across a population.
Uncertainty, on the other hand, represents lack of knowledge about factors such as
adverse effects or contaminant levels which may be reduced with additional study.
Generally, risk assessments carry several' categories of uncertainty, and each merits
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consideration. Measurement uncertainty refers *o the usual error that accompanies
scientific measurements-standard statistical techniques can often be used to express
measurement uncertainty. A substantial amount of uncertainty is often inherent iu
environmental sampling, and assessments should address these uncertainties.
There are likewise uncertainties associated with the use'of scientific models, e.g./
dose-response models, models of environmental fate and transport. Evaluation of
model uncertainty would consider the scientific basis for the model and available
empirical validation.
A different kind of uncertainty stems from data gaps — that is, estimctes or
assumptions used in the assessment. Often, the data gap is broad, such as the
absence of information on the effects of exposure to a chemical on humans or on
the biological mechanism of action of an agent. The risk assessor should include a
statement of confidence that reflects the degree to which the risk assessor believes
that the estimates or assumptions adequately fill the data gap. For some common
and important data gaps, Agency or program-specific risk assessment guidance
provides default assumptions or values. Risk assessors should carefully consider all
available data before deciding to rely on default assumptions. If defaults are used,
the risk assessment should reference the Agency guidance that explains the default
assumptions or values.
Often risk assessors and managers simplify discussion of risk issues by speaking only
of the numerical components of an assessment. That is, they refer to the alpha-
numeric weight-of-the-evidence classification, unit risk, the risk-specific dose or the
qi* for cancer risk, and the RfD/RfC for health effects other than cancer, to the
exclusion of'other information bearing on the risk case. However, since every
assessment carries uncertainties, a simplified numerical presentation of risk is
always incomplete and often misleading, for this reason, the NRC (1) and EPA risk
assessment guidelines (2) call for "characterizing" risk to include qualitative
information, a related numerical risk estimate and a discussion of uncertainties,
limitations, and assumptions-default and otherwise.
Qualitative information on methodology, alternative interpretations, and working
assumptions (including defaults)- is an important component of risk
characterization. For example, specifying that animal studies rather than human
studies were used in an assessment tells others that the risk estimate is based on
assumptions about human response to a particular chemical rather than human
data. Information that human exposure estimates are based en the subjects'
presence in the vicinity of a chemical accident rather than tissue measurements
defines known and unknown aspects of the exposure component of the study.
Qualitative descriptions of this kind provide crucial information that augments
understanding of numerical risk estimates. Uncertainties such as these are expected
in scientific studies and in any risk assessment based on these studies. Such
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uncertainties do not reduce the validity of the assessment. Rather, they should be
highlighted along with other important risk assessment conclusions to inform
others fully on the results of the assessment.
In many cases, assessors must choose among available data, models, or assumptions
in estimating risks. Examining the impact of selected, plausible alternatives on the
conclusions of the assessment is an important .part of the uncertainty discussion.
The key words are "selected" and "plausible;" listing all alternatives to a particular
assumption, regardless of their merits would be superfluous. Generators of the
assessment, using best professional judgment, should outline the strengths and
weaknesses of the plausible alternative approaches.!
An adequate description of the process of alternatives selection involves several
aspects.
a. A rationale for the choice.
b. Discussion of the effects of alternatives selected on the assessment.
c. Comparison with other plausible alternatives, where appropriate.
The degree to which variability and uncertainty are addressed depends largely on
the scope of the assessment and the resources available. For example, the Agency
does not expect an assessment to evaluate 3nd assess every conceivable exposure
scenario for every possible pollutant, to examine all susceptible populations
potentially at risk, or to characterize .every possible environmental scenario to
estimate the cause and effect relationships between exposure to pollutants and
adverse health effects. Rather, the discussion of uncertainty and variability should
reflect the type and complexity of the-risk assessment, with the level of effort for
analysis and discussion of uncertainty corresponding to the level of effort for the
assessment.
3. Well-balanced risk characterizations present risk conclusions and information
regarding the strengths and limitations of the assessment for other risk
assessors, EPA decision-makers-, and the public.
The risk assessment process calls for identifying and highlighting significant risk
conclusions and related uncertainties partly to assure full communication among
risk assessors and partly to assure that decision-mak..»rs are fully informed. Issues
are identified by acknowledging noteworthy qualitative and quantitative factors that
make a difference in the overall assessment of hazard and risk, and hence in the
ultimate regulatory decision. The key word is "noteworthy." Information that
l In cases where risk assessments within an Agency program routinely address similar sets 'of
alternatives, program guidance may be developed to streamline and simplify the discussion of these
alternatives.
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significantly influences the analysis-is explicitly noted — in ail future-presentations
of the risk assessment and in the related decision. Uncertainties and assumptions
that strongly influence confidence in the risk estimate also require special attention.
Numerical estimates'should not be separated from the descriptive information that
is integral to risk characterization. Documents and presentations supporting
regulatory or site-specific decisions should include both the numerical estimate and
descriptive information; in short reports, this information can be abbreviated. Fully
visible information assures that important features of the assessment are
immediately available at each level of review for evaluating whether risks are
acceptable or unreasonable.
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EXPOSURE ASSESSMENT AND RISK DESCRIPTORS
A. Presentation of Risk Descriptors
The results of a risk assessment axe usually communicated to the risk manager in
the risk characterization portion of the assessment This communication is often
accomplished through risk descriptors which convey information and answer
questions about risk, each descriptor providing different information, and insights.
Exposure assessment plays a key role in developing these risk descriptors since each
descriptor is based in part on the exposure distribution within the population of
interest.
The following guidance outlines the different descriptors in a convenient order that
should not be construed as a hierarchy of importance. These descriptors should be
used to describe risk in a variety of ways for a given assessment, consistent with the
isment's purpose, the data available, and the information the risk manager
needs. Use of a range of descriptors instead of a single descriptor enables Agency
programs to present a picture of risk mat corresponds to the range of different
exposure conditions encountered for most environmental chemicals. This analysis,
in turn, allows risk managers to identify populations at greater and lesser risk and to
shape regulatory solutions accordingly.
Agency risk assessments will be expected to address or provide descriptions of (1)
individual risk mat include the central tendency and high end portions of the risk
distribution, (2) population risk; and (3) important subgroups of the population,
such as highly exposed or highly susceptible groups. Assessors may also use
additional descriptors of risk as needed: when these add to the clarity of the
presentation. With the exception of assessments where particular descriptors dearly
do not'apply, some form of these three types of descriptors should be routinely
developed and presented for Agency risk assessments*. In other cases, where a
descriptor would be relevant but the program lacks the data or methods to develop
it, the program office should design and implement a plan, in coordination with
other EPA offices, to meet these assessment needs. While gaps continue to exist,
risk assessors should malt their best efforts to address each risk descriptor, and at a .
minimum, should briefly discuss the lack of data or meuicJ.... Finally, presenters of
risk assessment information should be prepared to routinely answer questions by
risk managers concerning these descriptors.
It is essential mat presenters not only communicate the results of the assessment by
addressing each of the descriptors where appropriate, but that they also
^Program-specific guidance will need to address these situations. For example, for site-specific
sments, the utility and * pp ro pria*TWff of population risk estimates will be determined based on
the available data and program guida
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communicate .their confidence- that these results portray a. reasonable-picture ol the
actual or projected exposures. This task will usually be accomplished by frankly
commenting on the key assumptions and parameters that have the greatest impact
on the results, the basis or rationale for choosing these assumptions/parameters,
and the consequences of choosing other assumptions.
B. Relationship Between Exposure Descriptors and Risk Descriptors
In the risk assessment .process, risk is estimated as a function of exposure, with the
risk of adverse afreets increasing as exposure increases. Information on the levels of
exposure experienced by different members of the population is key to
understanding the range of risks mat may occur.. Risk-assessors and risk managers
should keep in mind, however, mat exposure is not synonymous with risk.
Differences among individuals in absorption rates, susceptibility, or other factors
mean that individuals with the same level of exposure may be at different levels of
risk In most cases, the state of the science is not yet adequate to define distributions
of factors such as population susceptibility. The guidance principles below discuss a
variety of risk descriptors that primarily reflect differences in estimated exposure. If
a full description of the range of susceptibility in the population cannot be
presented, an effort should be made to identify subgroups that for various reasons,
may be particularly susceptible.
C Guiding Principles
L Information about the distribution of individual exposures is important to
communicating the results of a risk assessment
The risk manager is generally interested in answers to questions such as the
following:
• Who are the people at the highest risk?
• .What risk levels are they subjected'to?
• What are they doing, where do they live, etc., that might be putting them at this
higher risk?
• What is the average risk for individuals in the population of interest?
Individual exposure and risk descriptors are intended to provide answers, to these
questions so as to illuminate the risk management decisions that need to be made.
In order to describe the range of risks, bom high end and central tendency
G-28
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descriptors are used to convey the variability in risk levels experienced by different
individuals in the population.
a. High end descriptor
For die Agency's purposes, high end risk descriptors are plausible estimates of the
individual risk for those persons at the upper end of the risk distribution. Given'
limitations in current understanding of variability in individuals' sensitivity to
toxins, high end descriptors wiH usually address high end exposure or dose {herein
referred to as exposure for brevity). The intent of these descriptors is to convey
estimates of exposure in die upper range of the distribution, but to avoid estimates
which are beyond the true distribution. Conceptually, high end exposure means
exposure above about the 90th percentile of the population distribution, but not
higher than the individual in the population who has the highest exposure. When
large populations are assessed, a large number of individuals may be included
within the "high end" (e.g., above 90th or 95th percentile) and information on the
range of exposures received by these individuals should be presented
High end descriptors are intended to estimate the exposures that are expected to
occur in small, but definable, "high end" segments of the subject population.? The
individuals with these exposures may be members of a special population segment -
or individuals in the general population who are highly exposed because of the
inherent stochastic nature of the factors which give rise to exposure. Where
differences in sensitivity cja be identified within the population, high end estimates
addressing sensitive individuals or subgroups can be developed.
In those few cases in which the complete data on die population distributions of
exposures and doses are available, high end exposure or dose estimates can be
represented by reporting exposuresor doses at a set of selected percentites of the
distributions, such aaithe 90lh, 956% and 98th percentile. High end exposures or
doses, as appropriate/ can men be used to calculate high end risk estimates.
In the majority of cases where the complete distributions are not available, several
methods help estimate a high end exposure or dose. If sufficient information about
the variability in chemical concentt jtiona, activity patterns, or other factors are .
available, the distribution may be estimated through the use of appropriate-.
modeling (e.g., Monte Carlo sinvilation or parametric statistical methods). The
Sffigh end estimates focus c« estimates of exposure mtteexp^ Bounding
estimates, on the other hand, an constructed to be equal to or greater than the highest actual risk in
the population (or the highest risk that could be expected in a future scenario). A "worst ease scenario"
refers to a combination of events and conditions such that taken together, produces the highest
conceivable risk Although it'is possible that such an exposure, dose, ox sensitivity combination might
occur in a given population of interest the probability of an individual receiving this combination of
events and conditions is usually small, and often so small that such a combination will not occur in a
particular, actual population.
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determination of whether available information- is sufficient to support the use- of
probabilistic estimation methods .requires careful review and documentation by. the
risk assessor. If the input distributions are based on limited data, the resulting
distribution should be evaluated carefully to determine whether it is an
improvement over more traditional estimation techniques. If a distribution is
developed, it should be described with a series of percentiles or population
frequency estimates, particularly in the high end range. The assessor and risk "
manager should be aware, however, that unless a great deal is known about
exposures and doses at the high end of the distribution, these estimates will involve
considerable uncertainty which the exposure assessor will need to describe. Mote
that in this context, the probabilistic analysis addresses variability of exposure in the
population. Probabilistic techniques may also be applied to evaluate uncertainty in
estimates (see section 5, below). However/ it is generally inappropriate to combine
distributions reflecting bom uncertainty and variability to get a single overall
distribution. Such a result is not readily interpretable for the concerns of
environmental decision-making.
If only limited information on the distribution of the exposure or dose factors is
available, die assessor should approach estimating the high end by identifying the
most sensitive variables and using high end values for a subset of these variables/
leaving others at their central values.* m doing this, the assessor needs to avoid -
combinations of. parameter values that are inconsistent (e.g., low body weight used
in combination with high dietary intake rates)/ and must keep in mind the ultimate
objective of being within the distribution of actual expected exposures and.doses,
and not beyond it
If very little data are available on the ranges for the various variables, it will be
difficult to estimate exposures or doses and associated risks in the high end with
much confidence. One method mat has been used in such cases is to start with a
bounding estimate and "back off the limits used until the combination of
parameter values is/ in the judgment .of the assessor/ within the distribution of
expected exposure, and stifl lies within the upper 10% of persons exposed.
Obviously/ this method results in a large uncertainty and requires explanation.
b. Central tendency descriptor.
Central tendency descriptors generally reflect central estimates of exposure or dose.
The descriptor addressing central tendency may be based on either the arithmetic
mean exposure (average estimate) or the median exposure (median estimate), either
^Maximizing all variables will- in virtually all <•*?» result in an- estimate that is above the
actual values seen in the population. When the principal parameters of the dose equation; eg.,
concentration (appropriately integrated over titne)«.mtake rate, and duration, are broken out into sub-
components, it may be necessary to use maximum values fcrincw than two of these sub-component
parameters, depending on a sensitivity analysis.
G-30
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of which should be dearly labeled. The average estimate, -used to approximate the
arithmetic mean, can often be derived by using average values for all the exposure
factors.5 It does.not necessarily represent a particular individual on the distribution.
Because of the skewness of typical exposure profiles, the arithmetic mean may differ
substantially from the median estimate (Le., 50th percentile estimate, which is equal
to the geometric mean for a log normal distribution). The selection of which
descriptor(s) to present in the risk characterization will depend on the available data
and tiie goals of the assessment When data are limited, it may not be possible to
construct true median or mean estimates, but it is still possible to construct
estimates of central tendency. The discussion of the use of probabilistic techniques
in Section l(a) above also applies to estimates of central tendency.
2. Information about population exposure leads to another important .way to
describe risk
Population risk refers to an assessment of the extent of harm for the population as a
whole. In theory, it can be calculated by summing the individual risks for all
individuals within the .subject population. This task, of course, requires a great deal
more information man is normally, if ever, available.
The kinds of questions addressed by descriptors of population risk include the
following:
* How many cases of a particular health effect might be probabilistically estimated
in mis population for a specific time period?
* For non-carcinogens, what portion of the population is within a specified range
of some reference level; eg., exceedance of the RfD (a dose), the RfC (a
concentration), or other health concern level?
* For carcinogens, what portion of the population is above a certain risk level,
such as 10*?
These questions can lead to two different descriptors of population risk.
a. Probabilistic number of cases
the first descriptor is the probabilistic numzK? of health effect cases estimated in the
population of interest over a specified time period. This descriptor can be obtained
either by (a) summing the individual risks over all the individuals in the
population, e.g. using an estimated distribution of risk in the population, when
5*nus holds true when variables are added (eg., exposures Toy different routes) or when
independent variables are multiplied (eg., concentration x intake). However, it would be incorrect for
products.of correlated variables, variables used as divisors, or for formulas involving exponents.
G-31
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such information is .available, or.(b) through-trie. use of a riskmodpl that assumes a.
linear non-threshold response to exposure, such as many carcinogenic models. In
these calculations, data will typically be available to address variability in individual
exposures. If risk varies linearly with exposure/ multiplying the mean risk by the
population size produces an estimate of the number of cases.6 At the present time,
most cancer potency values represent plausible upper bounds on risk. When such a
value is used to estimate numbers of cancer cases, it is important to understand-that
the result is also an upper bound. As with other risk descriptors, this approach may
not adequately address sensitive subgroups for which different dose-response curve
or exposure estimates might be needed.
Obviously, the more information one has, the more certain the estimate of this risk
descriptor, but inherent uncertainties in risk assessment methodology place
limitations on the accuracy of the estimate. The discussion of uncertainty involved
in estimating the number of «*i»i?y should indicate mat this d^ffgriptor is not to be
CPTfftl-'flsd with an acttigrja] oTedfgtioit of <*a«gg 'in the population (which is a
statistical prediction based on a great deal of empirical data).
In general, it should be recognized that when small populations are exposed,
population risk estimates may be very small. For example, if 100 people are exposed
to an individual lifetime cancer risk of 1(H, the expected number of cases is 0.01. In
such situations, individual risk estimates will usually be a more meaningful
parameter for decision-makers.
b. Estimated percentage of population with ride greater than some level
For non-cancer effects, we generally have not developed the risk assessment
techniques to the point of knowing how to add risk probabilities, so a second
descriptor is usually more appropriate: An estimate of the percentage of the
population, or the number of persons, above a specified level of risk or within a
specified range of some reference level eg., exceedanos of the RfD or the RfC,
LOAEL, or other specific level of interest This descriptor must be obtained through
measuring or simulating the population distribution.
3* Information about the distribution of exposure and risk for different S3
of the population are important components of a risk assessment .
A risk manager might also ask questions about the distribution of the risk burden
among various segments of the subject population such as the following: How do
exposure and risk impact various subgroups?; and, what is the population risk of a
6However, certain important cautions apply (ace EPA's Exposure Assessment Guidelines). Also,
this is not appropriate for non-earonogmic effects or for other types of cancer models. Fornon-linear
cancer models, an estimate of population risk must be calculated using the fitctrifrutiffn of individual
risks.
G-32
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particular subgroup? Questions about the distribution of exposure and risk among
such population segments require additional risk descriptors.
a. Highly exposed
Highly exposed subgroups can be identified, and where possible/ characterized and
the magnitude of risk quantified. This descriptor is useful when there is (or is
expected to be) a subgroup experiencing significantly different exposures or doses
from that of the larger population. These sub-populations may be identified by age/
sex, lifestyle/ economic factors, or other demographic variables. For example,
toddlers who play in contaminated soil and high fish consumers represent sub-
populations that may have greater exposures to certain agents.
b. Highly susceptible
Highly susceptible subgroups can also be identified, and if possible, characterized and
the magnitude of risk quantified. This descriptor is useful when die sensitivity or
susceptibility to the effect for specific subgroups is (or is expected to be) significantly
different from mat of the larger population. In order to calculate risk for these
subgroups, it will sometimes be necessary to use a different dose-response-
relationship; e.g./ upon exposure to a chemical pregnant women, elderly people,
children, and people with certain illnesses may each be more sensitive than me
population as a whole. For example, children are thought to be both highly exposed
and highly susceptible to the effects of environmental lead. A model has been
developed that uses data on lead concentrations in different environmental media
to predict the resulting blood lead levels in children. Federal agencies are working
together to develop specific guidance on blood lead levels mat present risks to
children.
It is important to note, however, that the Agency's current methodologies for
developing reference doses and reference concentrations (RfDs and RfCs) are
designed to protect sensitive populations. If data on sensitive human populations
are available (and there is confidence in the quality of the data), then the RfD is set at
the dose level at which no adverse effects are observed in the sensitive population
(e.g., RfDs for fluoride and nitrate). If no such data are waflable (for example, if the
RfD is developed using data from humans of average or unknown sensitivity) then
an additional 10-fold factor is used to account for variability between me average
human response and (he response of more sensitive i idividuals.
Generally, selection of the population segments is a matter of either a priori interest
in the subgroup (e.g., environmental justice considerations)/ in which case the risk
assessor and risk manager can jointly agree on which subgroups.to highlight, or a
matter of discovery of a sensitive or nighty exposed subgroup during the assessment
G-33
-------
process. In either case, .once, identified, the subgroup can be treated as-a. population.
in itself, and characterized In die same way as the larger population using the
descriptors for population and individual risk.
4. Situation-specific information adds perspective on possible future events or
regulatory options.
"What if.-?" questions can be used to examine candidate, risk management options.
For example/ consider the following:
• What if a pesticide applicator applies this pesticide without using protective
equipment?
• What if this site becomes residential in the future?
• Whatrisk level will occur if we set the standard at 100 ppb?
Answering these "What if...?" questions involves a calculation of risk based on
specific combinations of factors postulated within the assessment?. The answers to
these "What if...?" questions do not, by .themselves, give information about how
likely the combination of values might be in the actual population or about how
many (if any) persons might be subjected to the potential future risk However,
.information on the likelihood of the postulated scenario would also be desirable to
include in the assessment.
When addressing projected changes for a population (either expected future
developments or consideration of different regulatory options), it is usually
appropriate to .calculate and consider all the risk descriptors discussed above When
central tendency or high end estimates are developed for a future scenario, these
descriptors should reflect reasonable expectations about future activities. For
example, in site-specific risk assessments, future scenarios should be evaluated
when they are supported by realistic forecasts of future land use, and the risk
descriptors should be developed within mat context
5. An evaluation of the uncertainty in Che risk descriptors is an important
component of the uncertainty discussion in the assessment
Risk descriptors are intended to address variability of risk within the population and
the overall adverse impact on the population. In particular, differences between
high end and central tendency estimates reflect variability in the population, but not
the scientific uncertainty inherent in the risk estimates. As discussed above, there
7Some programs routinely develop future scenarios as part of developing a risk assessment
Program-specific guidance nay addr0*^ future yw^ri^f in more detail ^*v they ace described here.
G-34
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will be uncertainty in all estimates of risk. These uncertainties can include .
measurement uncertainties, modeling uncertainties, and assumptions to fill data
gaps. Risk assessors should address the impact of each of these factors on the
confidence in the estimated risk values.
Both qualitative and quantitative evaluations of uncertainty provide useful
information to users of the assessment The techniques of quantitative uncertainty
analysis are evolving rapidly and both the SAB (8) and the NRC (4) have urged the
Agency to incorporate these techniques into its risk analyses. However, it should be
noted that a probabilistic assessment mat uses only 'the assessor's best estimates lor
distributions of population variables addresses variability, but not uncertainty.
Uncertainties in the estimated risk distribution need to be separately evaluated.
G-35
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REFERENCES
1. National Research Council. ffi^V Assessment in the Federal Government:
' 1983.
2. U.S. EPA. K^fc /^ssgsamgnt and Kf^nflBfflmP"^ T*Tairigwork for
1984.
3. US EPA. "Risk Assessment Guidelines." 51 Federal Register, 33992-34054,
September 24, 1986.
4. National Research Council. Science and Tufjg^rnfllP^ *** ^^k Asfi^88131^^^- 1994
5. US EPA ."Guidelines for Exposure Assessment" 57 Federal Register, 22888-
22938, May 29, 1992.
6. U;S. EPA. "Guidelines for Developmental Toxicity Risk Assessment" 56 Federal
Register, 67398-63826, December 5, 1991.
7. US' EPA. Framg^york for Ecological Risk Assessment 1992.
8. Loehr, RJL> and Matanoski, G.M., Letter to Carol M. Browner, EPA
Administrator, Re Quantitative Uncertainty Analysis for Radiological
Assessments. EPA Science Advisory Board, July 23, 1993 (EPA-SAB-RAC-COM-
93-006).
G-36
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ATTACHMENT 3
CHARACTERIZATIONS
— Risk Charartorirafirm
There are a number of principles which form the basis for a risk characterization:
• Risk assessments should be transparent, in that the conclusions drawn from the
science are identified separately from policy judgements, and the use of default
values or methods and the use of assumptions in the risk assessment are dearly
articulated.
• Risk characterizations .should include a summary of the key issues and
conclusions of each of the other components of the risk assessment as well as
describe the likelihood of harm. The summary should include a description of
the overall strengths and the limitations (including uncertainties) of the
assessment and conclusions.
• Risk characterizations should be consistent in general format, but recognize the
unique characteristics of each specific situation.
• Risk characterizations should include, at least in a qualitative sense, a discussion
of how a specific risk and its context compares withi other similar risks This may
be accomplished by comparisons with other, chemicals or situations in which the
Agency has decided to act, or with other situations which the public may be
familiar with. The discussion should highlight the limitations of such
comparisons.
• Risk characterization is a key component of risk communicatiorv whkh is an
interactive process involving exchange of information and export opinion
among individuals, groups and institutions.
Conceptual Guide for Developing Chemical-Specific Risk Characterizations
The following outline is a guide and formatting aid for developing risk
characterizations for chemical risk assessments. Similar outlines will be developed
for other types of risk characterizations, including site-specific assessments and
ecological risk assessments. A common format will assist risk managers in
evaluating and using risk characterization.
y'Tie outline has two parts. The first part tracks the risk assessment to bring forward
s major conclusions. The second part draws all of the information together to
haracterize risk. The outline represents the expected findings for a typical complete
hemical assessment for a single chemical. However, exceptions for the
-------
circumstances of individual assessments exist and should be explained as part of the
risk characterization: For example, particular statutory requirements, court-ordered
deadlines, resource limitations, and other specific factors may be described to explain
why certain elements are incomplete.
This outline does not establish or affect legal rights or obligations. Rather, it ~
confirms the importance of risk characterization, outlines relevant principles, and
identifies factors Agency staff shouM cc«isito m impleinfinting the policy. Qua
continuing basis, Agency management is expected to evaluate the policy as well as
the results of its application throughout the Agency and undertake revisions as
necessary. Therefore, the policy does not stand alone; nor does it establish a binding
norm that is finally determinative of the issues addressed. Minor variations in its
application from one instance to another are appropriate and expected; they thus are
not a legitimate basis for delaying or complicating action on otherwise satisfactory
scientific, technical, and regulatory products. •
PART ONE
SUMMARIZING MAJOR CONCLUSIONS IN RISK CHARACTERIZATION
Characterization of Hazard Identification
A. What is the key toxkologkal study (or studies) that provides the basis for
health concerns?
- How good is the key study?
- Are the data from laboratory or field studies? m single species or
multiple species?
- If the hazard is carcinogenic/ comment on issues such as: observation of
single or multiple tumor sites; occurrence of benign or malignant
rumors; certain tumor types not linked to cartinogenicity; use of the
maximum tolerated dose (MTD).
- If the hazard is other than carcinogenic, what endpoints were observed,
.. and what is the basis for the critical effect?
— Describe other studies that support this finding.
- Discuss any valid studies which conflict with mis finding.
B. Besides the health effect observed in the key study, are mere other health
endpoints of concern?
- What are the significant data gaps?
C Discuss available epidemiological or clinical data. For epidemic-logical
studies:
— What types of studies were used, Le., ecologic, case-control, cohort?
G-38
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- Describe the degree to which exposures were adequately described.
- Describe the degree to which confounding factors.were adequately
accounted for.
- Describe the degree to. which other causal factors were excluded.
D. How much is known about how (through what biological mechanism) the
chemical produces adverse effects?
- Discuss relevant studies of mechanisms of action or metabolism.
- Does this information aid in the interpretation of the toxiciry data?
- What are the implications for potential health effects?
E. Comment on any non-positive data in,animals or people, and whether
these data were considered in the hazard identification.
F. If adverse health affects have been observed in wildlife species, characterize
such effects by discussing the relevant issues as in A through 1 above.
G. Summarize the'hazard identification and discuss the significance of each of
he following:,
- confidence in conclusions;
- alternative conclusions that are also supported by the data;
- significant data gaps;^nd
- highlights of major assumptions.
IL Characterization of Dose-Response
A. What data were used to develop die dose-response curve? Would the
result have been significantly different if based on a different data set?
- If animal data were used:
— which species were used? most sensitive, average of all species, or
other?
— were any studies excluded? why?
- If epidemiologies! data were used:
- Which studies were used? only positive studies, all studies, or
some other combination?
- Were any studies excluded? why?
— , Was a meta-analysis performed to combine the epidemiological
studies? what approach was used? were studies excluded? why?
B. What model was used to develop the dose-response curve? What rationale
supports this choice? Is chemical-specific information available to support
this approach?
- For non-carcinogenic hazards:
— How was the RfD/RfC (or the acceptable range) calculated?
G-39
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— What assumptions or uncertainty factors were used?
— What is the confidence in the estimates?
- For carcinogenic hazards:
- What dose-response model was used? LMS or other finear-at-Iow-
dose model, a biologically-based model based on metabolism data,
or data about possible mechanisms of action?
— What is the basis for the selection of the particular dose-response
model used? Are there other models mat could have been used
with equal plausibility and scientific validity? What is the basis for
selection of the model used in this instance?
C Discuss the route and level of exposure observed, as compared to expected
human exposures.
- Are the available data from the same route of exposure as me expected
human exposures? If not are pharrnacokinetic data available to
extrapolate across route of exposure?
- How far does one need to extrapolate from the observed data to
environmental exposures (one to two orders of magnitude? multiple
orders of magnitude)? What is the impact of such ah extrapolation?
D. If adverse health- affects have been observed in wildlife species, characterize
dose-response information using the process outlined in A-C
Dl Characterization of Exposure
A. What are the most significant sources of environmental exposure?
- Are mere data on sources of exposure from different media? What is the
relative contribution of different sources of exposure?
- What are the most significant environmental pathways for exposure?
B. Describe the populations that were assessed, including as the general
population, highly exposed groups, arid highly susceptible groups.
C Describe the basis for the exposure assessment, including any monitoring,
modeling, or other analyses of exposure distributions such as Monte-Carlo
or krieging.
D. What are the key descriptors of exposure?
- Describe the (range of) exposures to: "average" individuals, "high.end"
individuals, general population, high exposure group(s), children,.
susceptible populations.'
- How was the central tendency estimate developed?' What factors and/or
methods were used in developing this estimate?
- How was the high-end estimate developed?
G-40
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— Is there information on highly-exposed subgroups? Who are they?
What are their levels of exposure? How are they accounted for in the
assessment?
E Is there reason to be concerned about cumulative or multiple exposures
because of ethnic, racial, or socioecpnomic reasons?
F. If adverse health affects have been observed in wildlife species, characterize
wildlife exposure by discussing the relevant issues as in A through E above.
G. Summarize exposure conclusions and discuss the following:
- results of different approaches, Le. modeling; monitoring,, probability
distributions;
- limitations of each, and the range of most reasonable values; and
- confidence in the results obtained/ and the limitations to the results.
PART TWO
RISK CONCLUSIONS AND COMPARISONS
FV. Risk Conclusions
A. What is the overall picture of risk, based on the hazard identification, dose-
response and exposure characterizations?
B. What are the major conclusions and strengths of the assessment in each of
the three main analyses (Le., hazard identification, dose-response, and
exposure assessment)?
C What are the major limitations and uncertainties in the three main
analyses?
D. What are the science policy options in each of the three major analyses?
- What are the alternative approaches evaluated?
- What are the reasons for the choices made?
V. Risk Context
A. What are the qualitative characteristics of the hazard (e.g., voluntary vs.
involuntary, technological vs. natural, etc)? Comment on findings, if, any,
from studies of risk perception mat relate to this hazard or similar hazards.
B. What, are the alternatives to this hazard? How do the risks compare?
G-41
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C How does mis risk compare to other risks?
•1. How does this risk compare to other risks in this regulatory program, or
other similar risks that the EPA has made decisions about?
2. Where appropriate, can this risk be compared with past Agency
decisions, decisions by other federal or state agencies, or common risks
warn which people may be familiar?
3. Describe the limitations of making these comparisons.
D. Comment on significant community concerns which influence public
perception of risk?
VL Existing Risk Information
Comment on other risk assessments mat have been done on this chemical by
EPA, other federal agencies, or other organizations. Axe there significantly
different conclusions that merit discussion?
VH. 'Other Information
Is there other information that would be useful to the risk manager or the
public In mis situation that has not been described above?
G-42
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ATTACHMI-NT
i
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March '1995
IMPLE3VIENTATION PROGRAM
FOR
THE EPA POLICY ON RISK CHARACTERIZATION
*<• PRO**- «|vvsmvs»vvvvsf5r»Mvvs«yvvsrvvvvvvvvvvM
Introduction
The EPA Science Policy Council (SPC) is implementing the Administrator's policy on
risk characterization through a year-long program of activities that will involve
risk assessors' and risk managers in .the practice of fully 'characterizing risk. This
interactive approach calls for inter- and intra-office activities to gain experience
with the fundamentals of the policy and to resolve issues that were identified during
Agency-wide review of early drafts. ' Implementation will include program-specific
guidance development; case study development; and risk characterization workshops
and ronntables for risk assessors and managers.
A SPC-sponsored "advisory group" will plan and execute, these implementation
activities. This advisory* group will 'organize an "implementation team" composed of
representatives, from the program offices, regions and ORD laboratories and centers.
This team will work closely with the advisory group to coordinate implementation
activities within their offices.
I
!
i
Program Guidance Development
Risk characterizations often differ
according to the type of assessment
involved. The aim is to work closely with
die Program Offices and Regions to
identify and address their specific risk
characterization needs and, where
appropriate, to develop assessment-
specific guidance.
This program updates and implements the
risk characterization guidance issued in
early 1992. The policy features a paper
entitled "Elements to Consider When
Drafting EPA Risk Characterizations."
This paper outlines generic elements for
characterizing risk, and provides a
prototype for assessment-specific
guidance. Program and Regional
offices win use this paper to identify
and address risk characterization issues
associated with specific assessment
types that 'differ from the general
prototype (e.g., site-specific and
ecological risk assessments). Lessons
learned from the case studies,
ronndtables and workshops (discussed
below) will also contribute to program-
specific guidance development
Case Studies
Today, when asked to provide an
example of a "good" risk
characterization, few people can
identify good examples, let alone
examples that others would agree are
RISK CHARACTERIZATION
IMPLEMENTATION SCHEDULE
Case Studies
RouiultaDtes taut WoricstioiM
1995
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G-43
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DR.4FT-DO NOT COPY, DISTRIBLTE. OR QUOTE.
APPENDIX F
PRELIMINARY IMPLEMENTATION STATEMENTS
for
C-l and C-2 Risk Characterization Colloquia
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RBOXOV *
DRAFT RISK CHARACTERIZATION IMPLEHEHTATIOM PLA*
8«eoad Draft
August 2t» H95
9rot«otioa
Dallas, TI
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REGION «
DRAFT RISK CHARACTER!2ATIOH ZHPLEHEHTATION PLAN
TABLE OF CONTENTS
I. Introduction. .p. i
Plan in development
Region 6 Risk Characterization Team
Draft Plan not reviewed by Region 6 Management
II. Purpose of Document p. 2
Components of the Regional Plan
III. Background of Risk Characterization.... p. 3
Administrator'.9 March 1995 memorandum
Agency Characterization Guidance and Policy
Region 6 risk activities and categories
IV. Relationship of Risk Characterization to Risk
Assessment p. 6
The summarizing step to risk assessment
Not.a reiteration of assessment conclusions
V. Criteria for Judging Adequacy of Risk
Characterizations. ..p. 7
Administrator's characterization goals:
clarity, transparency, consistency, reasonable .
VI. Ensuring Consistency ..........;............ .p. 9
Responsibility of Regional Characterization Team
Program documentation
VIZ. Evaluating Special Circumstances. .......p. 10
Regional examples of category I and II analyses
VIII.Scope of the Region 6 Implementation Plan p. 14
IX. Guide for Developing chemical .Specific Risk
Characterizations • ..p. 15
Summarizing major conclusions
Risk conclusions and comparisons
X. ^Statement of Commitment. p. 20
Key elements of. the Region 6 Characterization Plan
TABLES
Table l. List of Region 6 Risk Assessment Activities p. 23
Table 2. Glossary of Acronyms / Region 6 Risk
Related Terms. p. 25
ATTACHMENTS
Attachment A. Region 6 Risk Characterization Program Documents
Draft Superfund Risk Characterization Plan (6//9S) p. Al-l
Draft Risk Characterization: Environmental Justice
Index Methodology (8/95) ;..... p. A2-1
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TABLE OP CONTENTS
Attachment A (continued).
Draft Risk Characterization Implementation Plan UIC
Land Ban Response (8/95) p. A3-1
Attachment B. EPA/Region 6 Memoranda
Administrator'* Risk Characterization Program
Memorandum (3/95) p. Bl-1
Regional Risk Characterization Implementation Team
Memorandum from Regional Administrator (5/95)...p. B2-1
Region 6 Nominee to the Risk Characterization
Implementation Team Memorandum from Regional
Administrator (5/95).. ..p. B3-1
Regional Risk Characterization Implementation Team
Memorandum from Regional Administrator p. B4-1
Response to Comments on Kraft Regional Risk
Characterization Plan. Memorandum from
Risk Team. p. B5-1
Attachment C. EPA Policy and Guidance Documents
March 1995 Policy for Risk Characterization at the
U.S. Environmental Protection Agency..' p. Cl-l
Guidance for Risk Characterisation
(February, 1995) p. C2-1
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REOIOH 6 EPA
RISK CHARACTERIZATION IKFLEMBHTATXOH PLAN
I. Introduction
Risk characterization is the summarizing step of risk assessment.
The risk characterization integrates information from the
preceding components of. the risk assessment: Hazard
Identification, Dose Response, and Exposure Characterization.
Risks can be partially described by the individual components of
a risk assessment, but risk characterization is a conscious and
deliberate process of bringing all important considerations about
risk into an Integrated and complete picture. Even more
importantly, as an intaara-fcad picture, the risk characterization
is not simply a reiteration of conclusions of the various
components, but a piece which* focusses on.hov those components
interact.
The following Region 6 Risk Characterization Implementation Plan
is the second draft of an evolving* set of risk characterization
procedures, policies, and guidelines. This draft Plan has not
been reviewed by Region 6 Management or the Region's legal
counsel. The Plan is a product of risk assessors form the major
Region 6 Programs, risk assessors in all EPA Regions, and a
Headquarters Risk Characterization Core Team.
The plan attempts to address the full scope of risk analyses
performed in Region «. Regional assessments ars defined and
placed into three categories: Screening^ Intermediate, and
Baseline (Categories I, II,.. and. III.respectively). These
categories are used to identify what level of risk
characterization effort can be performed for each.
Full risk characterizations for Regional products are not
possible at this time for several reasons: 1) Agency guidance is
not available for uncertainty analyses, ecological risk, or cost-
benefit studies! 2) risk characterizations for Programs involving
permits must be coordinated with National, and State partnerst 3)
risk characterization policies have not -been developed to address
risk analyses performed by industry facilities, 4) resources are
not available to perform additional, more extensive, risk
characterization procedures and studies.
Although Region * recognizes the barriers to full implementation
of Agency risk characterization, the Region is committed to
coordination of risk characterization efforts, ensuring
scientific credibility, and striving to attain the
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Administrator's goals for clarity, transparency, consistency, and
reasonableness of risk assessment conclusions. Transparency
requires that conclusions drawn from science are identified
separately from policy judgments, and the.use of default values,
methods, and assumptions in the risk assessment are clearly
articulated.
IX. Purpose
This Implementation Plan addresses all risk evaluation activities
in Region 6 and provides the Region vita guidance for
characterizing risk assessment conclusions. The goal is to
institutionalize a consistent risk characterization process. The
Plan emphasizes the concepts of clarity, transparency,
consistency, and reasonableness.* By providing an operational
framework for Region 6 risk characterizations, the Plan expands
on the Agency's March 1995 Risk Characterization Policy and its
accompanying Guidance (Attachments)...
The Implementation Plan identifies the kinds of assessments
produced by Region 6 Programs and addresses how the principles
and guidance will bet reflected in each, of them. Where a
principle or guidance point cannot be' incorporated, reasons are
given or a plan for filling the gap is provided.
The objective of the Risk Characterization Policy and this
Implementation Plan is to ensure that risk characterizations' fonr
a complete and Coherent picture at. a. level of detail appropriate
for the decision being supported. Accordingly, greater emphasis
is placed on ensuring clarity, consistency, and reasonableness of
the risk picture and transparency of the decision-making process
than on reformatting or otherwise reiterating the conclusions of
risk assessment components that precede the characterization*
Key elements of the Region 6 Risk Characterization Plan include
the. following;
1) An inventory of Regional risk activities with each risk
assessment assigned to one or more categories (TABLE 1).
2) Definitions for three Categories of Regional risk
evaluations based on level of effort, cost, statutory
requirement*, and uses of the assessment results.
3) Formation of a Regional Risk Characterization Team
responsible for coordination. Program consistency, reporting
to Senior Management, and assuring scientific credibility of
risk characterization products.
4) Recognition that full implementation is dependent upon
development of specific technology guidance .documents.
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5) Full implementation is dependent upon technical / statutory
coordination with Headquarters EPA Programs and increased
resources.
6) A schedule for implementing the plan and initiating the
development of Program specific risk characterization
documents.
7) Recognition that adherence to quality science and rigorous
documentation procedures are the basi.4 for successful risk
characterization in Region 6.
III. Background
In March of 1995, the Administrator issued a policy statement
which requires that rislc characterizations be prepared "in a
manner that is clear, transparent, reasonable and consistent with
other risk characterizations of similar scope prepared across
programs in the Agency". The statement vas accompanied by the
Agency Guidance for Risk Characterization. The Administrator's
Risk Characterization memorandum, the Policy and Guidance are in
Attachment A. The guidelines were prepared by the Science Policy
Council in consultation with Regional risk assessors. The-
Science Policy Council has organized a Risk Characterization
Implementation Core Team. The Teaa is responsible for
coordinating the development of, risk characterization plans for
EPA Headquarters and Regions.
Region 6 has participated in the Core Team and Regional risk
assessor's planning conference call*; assisted in development of
a Regional Draft Superfund Risk Characterization Implementation
Plan, and formed a Regional Implementation Team. The Region 6 '
Team is composed of staff risk assessors .from our Water,
Hazardous Waste, Superfund, Air, and Enforcement Divisions. The
Regional Team is composed of Dr. Jon Rauscher, Dr. Ghassan
Khoury, Blake Atkins, Michael Morton, Young Moo Kim, Maria
Martinez, Mark Hansan, Phil Crocker, Clay Chesney/ and Dr. Gerald
Carney.
The Regional Team has drafted a List of Region 6 Risk Assessment
Activities (TABLE 1). The Teas has also assisted in the
formulation of a Program specific risk characterization draft
document. The Draft Superfund Risk Characterization
implementation Plan was written by Region 2 and reviewed by
Superfund risk assessors representing all ten EPA Regions. The
draft Superfund Plan i» Attachment: a. The coordination in
writing the Superfund Risk Characterization Plan provided
consistency among Regions for this important Program. The Region
6 Plan directs each Region € Program to write a characterization
plan and provides the Superfund. Plan as an example.
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Table 1 provide* a listing of various types of Region 6 risk
evaluations divided into three categories relative to data
quality and type, published guidelines, level of effort and cost.
Category I analyses* are preliminary or screening risk
evaluations using initial ambient or regulatory data to identify
potential immediate and long-term health impacts from a site or
pollution source. These assessments often include limited or no
sampling data, assumed potential cause and effect or association,
evaluation of worst-case exposure scenarios, and a qualitative
uncertainty analysis. Risk managers can utilize this information
to formulate regulatory actions, determine enforcement
prioritization, or to rank various pollution sources.' These
assessments typically cost less than $50,000 (excluding sample
collection, analysis and corrective action costs). Level of
effort requirements are usually 1-3 EPA staff or contractor
assistance for 1 to 6 months. Examples of preliminary and.
screening assessments include evaluations for emergency response
activities, enforcement targeting, and risk comparison exercises
using water quality standards.
Category XX risk assessments are intermediate analyses and
include* more ambient sampling data, analysis of indirect
exposures, collection of site-specific exposure data, and a
qualitative assessment of uncertainty. The information from
these risk assessments can be .used by risk managers to accelerate
removal actions, to evaluate the effectiveness of remediation
options, water treatment or other regulatory activities.
Typically these assessments cost between $50,000 to $75,000
(excluding sample collection, analysis and corrective action
costs), and require. 3-7 EPA staff or contractor personnel for 6
to 12 months. Examples of -intermediate assessments are ranking
sites for inclusion on the KPL using the CERCLA Hazard Ranking
System (HRS), Superfund remedial design reviews, and permit
activities in the HPDBS and SDWA Programs.
Category XXX. The baseline or full riate assessment is •
exclusively a CERCLA or RCRA program .effort in Region 6, They
are analyse* of the potential adverse health effects (current or
future) caused by hazardous substances released from a site in
the absence of. any actions to control or mitigate these releases.
The baseline risk assessment contributes to the site
characterization and subsequent development, evaluation and
selection of appropriate response alternatives. The results from
the baseline risk assessments provide risk managers with
information to determine if remedial actions are required, modify
remediation goals, and document the magnitude and causes of the
risks at the site. These assessments typically involve more
detailed risk characterizations .than Categories I and II. .
Typically these assessments cost $75,000 or. more (excluding
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sample collection, analysis, communication and remediation
costs). Approximately 20 EPA or contract personnel are required
with the effort extending from a 1 to 3 year period. Examples of
Regional baseline risk analyses are RCRA Facility Investigations
(RFI), CERCIA Remedial Investigation/Feasibility Studies (RI/FS),
and RCRA analysis involving incinerators.
It is important to note that these three categories can be a
continuum* The risk assessment activities described under one
category may be found under a different category as the needs for
the assessment and its intended use changes.
The "Guidance for Risk Characterization" provides general
principles for characterizing risk. These principles are as
follows:
1) The risk characterization integrates the information .from
the hazard identification, dose-response,, and exposure
assessments, using a combination of qualitative information,
quantitative information, and information regarding
uncertainties.
2) The risk characterization includes a discussion of
uncertainty and variability.
3) Well-balanced risk characterizations present risk
conclusions and information regarding the strengths and
limitations of the assessment for other risk assessors, EPA
decision-makers, and the .public.
An important early document in the evolution of Risk
Characterization Plans was "Elements to Consider When Drafting
EPA Risk Characterization*". The document was a product of the
Core Teas and provided the .following risk characterization
principles.;
1) Risk assessments should be transparent, in that the
conclusions drawn from the science are identified separately
from policy judgments, and default values, analytical
methods, and assumptions must be clearly articulated.
2) Risk characterizations should include a summary of the key
issues and conclusions of each of the other components of
the risk assessment, as well as describe the likelihood of
harm. The summary should include a description of the
overall strengths and the limitations (including
uncertainties) of the assessment and conclusions.
3) Risk characterizations should be consistent in general
format,. but recognize the -unique characteristics of each
specific.situation.
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4) Risk characterizations should include, at least in a
qualitative sense, a discussion of how a specific risk and
its context compares with other similar risks. This may be
accomplished by comparisons with other chemicals or
-situations in which the Agency has decided to act, or vith
other situations which the public may be familiar with. The
discussion should highlight the limitations of such
comparisons.
5) Risk characterization is a key component of risk
communication, which is an interactive process involving
exchange of information and expert opinion, among
individuals, groups and institutions.
Specific principles for exposure assessment and risk descriptors
are. given in the Guidance document. Paraphrased, they are as
follows:
1) Describe the distribution of individual exposures.
2) Describe population exposure.
3) Describe distribution of exposure and risk for subgroups of
the population^
4) Include situation-specific information where appropriate, to
add perspective,, for possible future events or regulatory
options.
5) Include an evaluation of the uncertainty in the risk
descriptors*
Clearly it is not always possible nor even necessary to include
all risk descriptors for every risk assessment since appropriate
data may not be available or the level of effort required to
obtain the data may not be appropriate for the level of decision
being made. An attempt is made in this document, -however, to
address each of the descriptors either by inclusion or by
explanation of why inclusion is not appropriate.
IV. Relationship of Risk Characterization to Risk Assessment
r. • . , * ,
Risk characterization is the summarizing step of risk assessment.
The risk characterization Integrates information from the
preceding components of the risk assessment:-Hazard
Identification, Doss Response, and Exposure Characterization,
Risks can be partially.described by the .Individual components of
a risk assessment, but .risk characterization is a conscious and
deliberate process of bringing all important considerations about
risk into an integrated .and complete picture. Even more
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importantly, as an integrated picture, the risk characterization
is not simply a reiteration of conclusions of the various
components, but a piece which focusses on how those components
interact.
V. Criteria for Judging Adequacy of Riafc yharaetarizafciong
The EPA'* commitment to producing risk assessments which include
enhanced/ more detailed, and accurate risk characterizations is
dependent upon activities which meet the Administrator's goals of
clarity, transparency, consistency, and reasonableness. Melding
these subjective goals to risk assessment methodologies requires
' careful definition of terms. What may be clear in meaning to one
individual or group may not be so clear to another with different
experiences, training,.or biases. Are we to aim for our clarity
and.reasonableness toward a technical or non-technical audience?
Understanding that the interests of the Agency is important to
all citizens, it would appear the audience is both. Also assumed
in the qualitative terms transparency and consistency is "full
disclosure" of available information. Again, how transparent and
how consistent? Risk assessors must use the quantitative tools
they have to interpret the Administrator's goals. Setting
measurable criteria for subjective goals will require Program
specific end points. The Groundwater Program will us* geological
and hydrological measures. The Drinking Water Program may use
microbiological measures.
These goals of communicating clearly, having transparent
policies, consistency and reasonable actions can only be realized
if Program methods and logic are accurately documented. This
being accomplished, risk assessment/communication activities can
be clearly chronicled and information more easily accessed by EPA
and others.
1) Claritj
Clarity is ultimately determined by understanding. Risk
characterizations should accurately document all data
accessed, the source and quality of the data, any bias in
thm information,- uncertainties, assumptions, and mention of
data not included or unavailable. .Regulatory data have a
pre-determined bias. The specificity of the assay used to
measure an ambient concentration or the specific sampling
location for the soil measurement are examples. Although
these are technical factors, they directly affect the
accuracy of the risk analysis. The risk characterization
strengths and limitations should b* understood without the
audience having to completely understand the technical '
details. Clarity can be accomplished more readily if risk
analysis specifics are easily accessible*
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Region 6 Program risk analyses can identify and assure that
specific bias producing assumptions and default values are
clearly articulated in the Risk Characterization sections of
their analyses. The Region's Risk Characterization Team can
assist each Program in adhering to consistent documentation
approaches and language.
2) Transparency
Transparency is a direct product of clarity and consistency
in risk analysis procedures. The logic applied to selection
of specific default values should be readily apparent to
reviewers of Region 6 risk assessments. Where attaining
clarity requires documentation and disclosure of risk
judgements/ transparency requires added statements
explaining the reasoning for assumptions and default values.
(Once 1 understand what the assessor did, I want to know
why.) with this information the assessment reviewer can
more easily determine the uncertainties and thus the
limitations when presented. The technical reviewer can
calculate risk conclusions based on different logic if
desired. (Using a different body weight factor for children
or other smaller average weight: subpopulations.)
Accomplishing Regional risk assessment transparency as
defined above can be accomplished by simply defining (and
ultimately justifying) the assumptions and default values
used in risk analyses. This requires bringing these values
out of the dose response, hazard identification, and
exposure characterization sections of Program risk
assessments. This can be accomplished by referencing and/or
attaching the default documentation used by the Program to
the assessment. Transparency vill assist the public in
separating scientific-conclusions from Agency policy
judgements.
3) consistency
Risk methodology consistency within Region 6 Programs, and
between Region € Programs,.Headquarter's Offices, State
Agencies, and EPA contractors will require significant time
to accomplish. Bach EPA Program has developed specific
media terminology, defaults, assumptions, and assessment
guidelines based on statutory and technical -parameters.
Development of risk characterization language for national
permit programs (NPDES, SDWA, UGST) will require extensive
coordination activity among Federal (Headquarters, Regions,
and Laboratories), State and local governments, and
industry.
Region 6 can inventory the risk methodologies, risk guidance
documents employed, decision criteria and logic used for the
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major Programs. This data can be used to recognize
differences or similarities in report format, interpretation
of regulatory standards, risk language, algorithms, and
application of guidelines. The recognition will enhance
Regional clarity and transparency for risk products.
4) Reasonableness
Reasonableness of conclusions can be determined .if the risk
assessment characterization adheres to the principle of
clarity, transparency, and consistency as described above.
Is it reasonable to use a 70 Kilogram body weight for a
population off chemical factory workers? Is it reasonable to
not perform an indirect exposure analysis when the source of
pollution is surface water discharge? Proper documentation
of all the risk, related data to include information
describing the conservative assumptions and known
uncertainties will ensure more accurate judgements regarding
reasonableness of the analysis.
Procedures taken to document and compare the consistency of
Region 6 risk analyses will afford- the Region a means of
comparing one risk to another. If a Superfund analysis
calculates a one in one hundred cancer risk for an exposure
based.from water ingestion and tht Drinking Water Program
calculates the same exposure at one in ten thousand, a
reasonableness issue can be raised to both -risk assessors.
VI. Ensuring Consistency
Consistency in definitions and methods of assessing risk is
fundamental to minimizing confusion about risk estimates
generated .across the Agency. However, while risk assessments
conducted in Region 6 share similar goals with risk assessments
prepared by other part* of the Agency, statutory requirements and
regulatory interpretation* influence our risk assessment
approaches. The following sections describe areas where Region 6
can use Agency wide definitions, methods, and .risk descriptors to-
ensure consistency, and areas where such use is constrained.
Reference. Doses (RfDs), cancer Potency Factors (Pfs), Hazard
Indices (HZ), Health Advisories (HA), Maximum Contaminant Levels
(MCL), Threshold Limit Values (TLVs), Permissible Exposure Limits
(PELs), National Ambient Air Quality Standards (HAAQS), and
Ambient Water Quality Criteria (AWQC) are a few of the many
environmental media standards and risk assessment calculations
used by risk assessors in Region 6. It is common in Region 6 for
risk assessors in our Drinking Water and Superfund Programs to
use an RfD from EPA's Integrated Risk Information System (IRIS).
Therefore, consistency exists among the Programs in using base
risk assessment values. Inconsistencies occur as each assessor
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applies the value to the specifics of the Water or Superfund risJc
scenario*. Different uncertainty factors or other exposure and
hazard assumptions can be used by assessors. The inconsistency
is compounded when RfDs, Pfs, or MCLs do not exist for a given
compound.
Risk screening and targeting analyses typically use Regionally
derived or national standard toxicity values to infer potential
exposure or health effects. Screening activities .(Category I)
may have the largest range of inconsistent application of risk
values *
The Superfund Hazard Ranking System (HRS) , the National Pollutant
Discharge Elimination System (NPDE3) Permit process, and use of
Ambient Water Quality 'Criteria (AWQS)- to determine a screening or
intermediate level risk evaluation all use different algorithms
and exposure factors. The reasons for the different approaches,
magnitude of the differences, and impacts upon the risk results
can be determined through implementation of the Region 6
characterization plan* The process begins with documentation of
the different analyses, regulatory guidance, and Program
rational.
Region 6 risk assessors from different Programs occasionally meet
to discuss available data and appropriate use of risk values.
The Region 6 Risk Characterization Plan will facilitate this
activity by communicating the Region's inventory of risk .
activities, their level -of effort, and analytical processes to
each risk assessor. The Risk Characterization Team can monitor
consistency and be a clearinghouse for Region 6 Program specific
methodologies.
Complete integration of risk processes is not possible in the
near term; The Region 6 Plan will immediately begin to identify
and document the different media and statutory characteristics of
each Program and to communicate these- differences to Regional
risk assessors.
VII. Evaluatin Special'
The Risk Characterization Policy recognizes that the nature of
the risk characterization will depend upon the information
available, the regulatory application of the risk information,
and the resources (including time) available. ' Considerations
specific to Region 6 include mandated site specific adherence to
risk assessment guidelines (Superfund Hazard Ranking System,
Remedial Investigation / Feasibility studies) or analyses which
require coordination between the Region and other State or
Federal offices (NPDES, Air, and RCRA .incinerator permits) . Each
have statutory requirements, court-ordered deadlines, or demand
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careful communications with Regional regulatory partners.
Category I and II risk assessment activities in Region 6 require
less than full risk characterization. Category I are screening
evaluations. Such evaluations do not have resources committed to
ambient sampling or extensive literature research. The level of
effort does not justify full characterizations. Category II
analyses are either permit related analyses, Regional guidance
supported by national standards, or risk targeting and
comparative risk studies. These studies usually do not have
level of effort resources to justify full risk characterizations.
Category II risk evaluation for permit support have the
additional requirement for extensive coordination with our
regulatory partners. There are numerous examples of Category I
and II risk assessment in Region 6. The following are examples
of studies not requiring full risk (Category III)
characterization. Each study does require rigorous documentation
of data sources, assumptions, data quality, and uncertainties.
1) The Region's Water Quality Management Branch has issued
guidance to our States concerning procedures for development
of vater quality standards. The Region's Hater Quality
Assessment (WQA) Branch occasionally performs screenings
using water and fish tissue, data with State standards. The
Branch may also use national guidance (1986 "gold book".
Quality Criteria, for Water). Cancer risk slope factors and
RfDs are obtained from IBIS as needed. Although full
characterization is not appropriate for this water analysis,
the Program would be required to document all relative
assumptions, uncertainties, and mathematical manipulations.
The sharing and mixing of Regional, Headquarters, and State
guidance; and standards will require the Region to address
risk characterization with States
2) Enforcement Targeting is a screening procedure using
1990 Census data. Toxic'Release Inventory (TRI) data, chemical
specific information, from the Superfund Chemical Data Matrix
document, EPA industry compliance data, and State information
to rank Region 6 industries and federal facilities as to
potential risk to the surrounding communities* The Region has
performed this screening activity for three .years. We share
all information with our State counterparts. Approximately
120 facilities are assessed each year. Environmental justice
(EJ) issues (demographics and proximity to the facility) are
evaluated and each facility is ranked using defined criteria.
The methodology ip computerized and developed in coordination
with the Region's environmental justice strategy* A
methodology is written which includes the limitations of the
computer systems used, databases accessed, and assumptions
made by the developers. Separate documents exist for the
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methodology and computer code. Peer review involves
distribution of the methodology documents inside and outside
of the Region (to Include State agencies and affected
industries).
3) Region 6 Management Division has developed an Environmental
Justice (Computer Assisted Demographic screening) analysis.
Any Region 6 staff member can obtain population, economic
status, and minority demographic data (1990 Census) for given
communities through the Region's Geographic Information System
EJ methodology. The system requires the requestor to identify
the point which best represents the area and concern, state
the .source and.quality of the locational data, and the EPA
program requesting the information. The methodology does not,
directly address .risk to human health. The system is used
with a risk based analysis (i.e., Enforcement Targeting) to
screen for potential impacts from industry emissions, truck
and rail traffic, proximity to landfills, water treatment
plants, or other regulated facilities.
4) Region 6 Water Supply Program was asked for an opinion on a
pesticide for which there is no MCL or Health Advisory. Water
Supply used the RfD in-IBIS and the procedures used by the
OGWDW for developing XC&Gs to estimate a safe level in water.
This level was later corroborated with the Health Effects
staff in the Office of Ground Water and Drinking water
(OGWDW). This is another screening level risk assessment not
considered to require full (Category IZZ) characterization.
5) In the Public Water Supply Enforcement Program, risk has been
used to set the national definitions of significant
noncompliers.'. The: Regional, enforcement program uses the
national significant noncomplier definition to target
enforcement actions. In . addition to addressing all
significant noncompliers, the Region also prioritizes certain
acute risks. Targeting according to acute risks and
significant noncompliance assures the highest risk situations
are addressed. •This is a Screening level risk assessment
(Category I).
6) Individual cases of risk are. discussed with water system
owners/operators for determining whether an alternate source
of drinking water should be sought; For example, discussions
with an Indian tribe, which detected high levels of uranium in
drinking water, convinced the tribe to shut down the drinking
water well with the highest levels of uranium and use an
alternate drinking water well with lower detected uranium
levels. As this exercise was part of compliance monitoring,
consider this.a screening level risk assessment (Category!).
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7} Permitting processes and review in both NPDES and Uiq
(Underground Injection Control) use national modeling criteria
which take into account human health. Hunan health risks are
determined from MCLs and national standards. Consider these
intermediate level risk assessments (Category II).
8) A risk based ranking system for the Underground Storage Tank
(UST) Program is currently implemented by our States. The
analysis (Risk Based Corrective Action - RBCA) examines
contaminants, depth of contamination, population, use of
groundwater and other pathway-exposure criteria. EPA
suggested the methodology and the Region is in a technology
transfer partnership with the States. Questions concerning
risk characterization requirements of State partners for this
shared Program are being addressed by the Region. The UST
analysis is a Category IX activity.
9) The Region 6 Comparative Risk Project required each Program to
submit a "risk assessment" report. Each report discussed
routes of exposure, ambient pollutant concentrations, exposed
populations, and estimates of disease incidence. Since the
1990 Region 6 report, Arkansas, Texas, Houston, and geographic
areas such as the U.S./Mexico border, and the Mississippi
River corridor between Baton Rouge and New Orleans have all
begun some level of comparative risk study. The Arkansas,
Texas, U.S./ Mexico border, and Corridor studies all have EPA
funding. All the studies examine human health, socio-economic
risk, and environmental justice issues. The Region routinely
participants in the development and review of risk reports
from the different State, local government, and academic
analysts. The Region .6 Risk Characterization Plan requires
outside researcher* to include risk characterizations
consistent with level of effort categorization.
An immediate question for Region 6 vac what type of risk analysis
(screening, baseline, socio-economic, comparison of a standard to
monitored concentration, qualitative comparative risk study) should
the Regional Risk Characterization Implementation Plan address.
The Plan identifies all Regional activities. The identification
process is an on-going activity requiring definitions to separate
risk assessment from risk screening, and related analyses. The
three categories were the result of this process.
Examination of the many Category I and II risk evaluations
performed in the Region raised several issues. A few of these
questions are:
l) How will risk characterizations address multi-risk projects?
For example, environmental justice requires analyses for human
health, economic, disenfranchisement and other welfare issues?
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2) How are enforcement sensitive analyses to be performed? An
. enforcement targeting method for the prioritizing, of chemical
violators is an example. These characterizations will need to
integrate. legal, regulatory, and science issues.
3) Should non-Super fund analyses financed and/or developed with
EPA assistance have risk characterization requirements written
into the grant Statement of Work?
4) Should risk characterizations for issuance of EPA Permits be
approved by all parties (Regional 'permit writer, Headquarters
Office, State Agencies) before incorporation as Regional
policy?
Using the criteria for Category X, II* or III risk activities will
determine whether . an assessment requires less-than-full risk
characterization. The Regional. Plan requires full characterization
for category -III assessments only. Full characterizations
currently include human health evaluation only. Statistical
uncertainty analyses, ecological and cost-benefit studies are nat
required of Category III risk characterizations. As EPA
guidelines, training, and resources are mad* available to Region 6,
these evaluation tools and procedures can be implemented.
Communications regarding risk and associated uncertainties are
covered by the Admlnistratorfs Risk Characterization Policy. This
includes communications between scientists, between scientists and
decision makers, and between Region 6 Programs and the public.
Documents describing components of risk assessments (i.e., hazard
and exposure assessments) ^ even if prepared as separate documents,
will fdllov the risk characterization policy (striving fox clarity,
transparency, consistency, and reasonableness) .
Documents related to risk or any of its components which are
submitted to Region. 6 by EPA contractors or other EPA Offices are
expected to follow the Risk Characterization Policy.
Documents from other Agencies or outside sources will conform to
the Region's Risk Characterization Policy before being used for
risk related decisions.
Similarly, information resource documents such as XRXS documents
which have been produced in the past by EPA but do not follow the
risk characterization principles will be augmented to meet the
requirements of the risk characterization policy before being used
in making future risk-related conclusions.
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Documents submitted by the public to Region 6 that relate to risk
assessment or any of its components, particularly to support
alternatives to EPA risk assessments, will be evaluated in light of
the Risk Characterization Policy.
Ecological risk assessments are ns£ covered by the Region 6 Risk
Characterization Implementation Plan because detailed guidance are
not available. However, if ecological assessment data is
presented, all ecological risk sections will address the points
discussed in the human health elements document to the extent they
are relevant. Characterizations should address the questions
raised in the Risk Assessment Forum's Framework for Ecological Risk
Assessment.
Assessments of benefits are not included in this Implementation
Plan. Although Region 6 acknowledges the principles of clarity,
transparency of process, consistency, and reasonableness apply also
to analyses of benefits, the Agency has not yet developed guidance
for these types of assessments.
IX. Guide for Developing Chemical—Specific Risk Characterizations
The following outline is a guide and formatting aid for developing
risk characterizations for chemical risk assessments. similar
outlines will . be developed for other types of risk
characterizations, including site-specific assessments and
ecological risk assessments.- A common format vill assist risk
managers in evaluating and using risk characterization.
The chemical specific risk characterization outline has two parts.
The first part tracks the risk assessment to bring forward it*
major conclusions. The second part draws all of the information
together to characterize risk* The outline represents the expected
findings for a typical complete chemical* assessment for a single
chemical. However, exceptions for the circumstances of individual
assessments exist and should be explained as part of the risk
characterization. For example, particular statutory requirements,
court-ordered deadlines, resource limitations, and other specific
factors may be described to explain why certain elements are
incomplete:.
PART ONE
SUMMARIZING MAJOR CONCLOSIONS IN RISK CHARACTERIZATION
1) Characterization of Hazard Identification
A. What is the key toxicological study (or studies) that
provides the basis for health concerns?
—How good is the key study?
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the data from laboratory or field studies? In
single species or multiple species?
—If the hazard is carcinogenic, consent on issues such a*:
observation of single or multiple tumor sites;
occurrence of 'benign or malignant tumors; certain
tumor types not linked to carcinogenicity; use of the
maximum tolerated dose (MTO) .
-If the hazard is other than carcinogenic, what endpoints
were observed, and what is the basis for the critical
effect?
-Describe other studies that support this finding.
-Discuss any valid studies which conflict with this finding.
B. Besides the health effect observed in the key study, are
there other health endpoints of concern?
-What are the significant data gaps?
C. Discuss available epidemiological or clinical data. For
epidemiological studies:
— What types of studies were used, i.e., ecologic, case-
control, retrospective cohort:?
— Describe the degree to which exposures were adequately
described.
— Describe the degree to which confounding factors were
adequately accounted for*
— Describe the degree to- which other causal factors were .
excluded.
D. How much is known about how I through what biological
mechanism) the chemical produces: adverse effects?
- Discuss relevant studies of mechanisms of action or
metabolism. - .
— Does this information aid in the interpretation of the
toxicity data?
- What are the implications for potential health effects?
B. Comment on any non-positive data in animals or people,
and whether these data were' considered, in the hazard
identification.
F. if adverse health affects have been observed in wildlife
species, characterize such effects by discussing the
relevant issues as in A through B above.
G. Summarize the hazard identification and discuss the
significance of each of he following:
— confidence in conclusions i
— alternative conclusions that are also supported by the
data;
— significant data gaps; and
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— highlights of major assumptions.
2) Characterization of Dose-Response
A. What data were used to develop the dose-response curve?
Would the result have been significantly different if
based on a different data set?
— If animal data were used:
— which species were used? most sensitive, average of
all species, or other?
— were any studies excluded? why?
— If epidemioiogical data were used:
— Which studies were used? only positive studies, all
.studies, OFT some other combination?
— Were any studies excluded? why?
—- Was a meta-analysis performed to combine the
epidemioiogical studies? what approach-was used?
were studies excluded? why?
B. What model was used to develop the dose-response curve?
What rationale supports this choice? Is chemical-
specific information available to support this
approach?
— For non-carcinogenic hazards:
—How was the RfD/RfC (or the acceptable range)
calculated?
— What assumptions or uncertainty factors were used?
— What is the confidence in. the estimates?
— For carcinogenic hazards:
—• What dose-response model was used?. IMS or other
linear-at-low-dos* model, a biologically-based model
based on metabolism data, or data about possible
mechanisms-of • action? .
— What is the basis for the selection of the particular
dose-response model used? Are there other models
that could have been used With equal plausibility and
scientific validity? What is the basis for selection
of the model used in, this instance?
C. Discuss the route and level of exposure observed, as
compared to expected human exposures.
— Are the available data from the same route of exposure as
the expected human exposures? If not, are
pharmacokinetic data available to extrapolate across
route of exposure?
— How far does one need to extrapolate from the observed
data to environmental exposures (one to two orders of
magnitude? multiple orders of magnitude)? What is the
impact of such an extrapolation?
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D. If adverse health affects have been observed in wildlife
species, characterize dose-response information using the
process outlined in A-C.
3) Characterization of. Exposure
A. What are the most significant sources of environmental
exposure?
— Are there data on sources of exposure from different
media? What is the relative contribution of
different sources of exposure? •
— What are the most significant environmental pathways
for exposure? . '
B. Describe the populations that were assessed, including as
the general population, highly exposed groups, and highly
susceptible groups.
C. Describe the basis for the exposure assessment, including
any monitoring, modeling, or other analyses of exposure
distributions such as Monte-Carlo or krieging.
D. What are the key descriptors of exposure?
— Describe the (range of X exposures tot "average*
individuals, high end* individuals, general
population, high exposure group (s) , children,
susceptible populations.
— How was the central tendency estimate developed? What
factors and/or methods were used in developing this
estimate?
— HOW was the high-end estimate developed?
— Is there information on highly-exposed subgroups? Who
are they?- What are their levels of exposure?' How are
they accounted for in the assessment?
R. Is there reason to be concerned about cumulative or
because of ethnic, racial, or
iple exposures' bec
oeconomie reasons?
F. If adverse health affects have been observed in wildlife
species, characterise wildlife exposure by discussing
the relevant issues as in A through B above.
6. Summarize exposure conclusions and discuss the following s
- results of different approaches, i.e. modeling,
monitoring, probability distributions; ~
— limitations of each, and the range of most reasonable
values} and
- confidence in the results obtained, and the limitations
to the results.
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PART TWO
RISK CONCLUSIONS AND COMPARISONS
4) Risk Conclusions
A. What is the overall picture of risk, based on the hazard
identification, dose-response and exposure
characterizations?
B. What are the major conclusions 'and strengths of the
assessment in each of the three main analyses (i.e.,
hazard identification, dose-response, and exposure
assessment)?
C. What are the major limitations and uncertainties in the
three main analyses?
D. What are the science policy options in each of the three
major analyses?
— What are the alternative approaches evaluated?
— What are the reasons for the choices made?
5) Risk Context
A. What are the qualitative characteristics of the hazard
(e.g., voluntary vs. involuntary, technological vs.
natural, etc.)? Comment on findings, if any, from studies
of risk perception that relate to this hazard or similar
hazards.
B. What are the alternatives, to this hazard? How do the
risks .compare?*7
C. How does, this risk compare to other risks?
- How does this risk compare to other risks in this
regulatory program, or other similar risks that the EPA
has made decisions about?
- Where appropriate, can this risk be compared with past
Agency decisions, decisions by .other federal or state
agencies, or common risks with which people may be
familiar?
- Describe the limitations of making these comparisons.
D. Comment on significant community concerns which
influence public perception of risk?
6) Existing Risk Information
Comment on other risk assessments that have been done on this
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chemical by EPA, other federal agencies, or other
organizations. Are there significantly different conclusions
that merit discussion?
7) other Information
Is there other information that would be useful to the risk
manager or the public in this situation that has not been
described above?
X. Statement of
Through this implementation Plan Region 6 intends to ensure that
risk characterizations produced by and for the Region will be
substantially consistent with Agency guidance and policy on risk
characterization, recognizing limitations in time and resources.
The plan will be updated as necessary.
The following is a summary of Key Elements contained in the
Region 6 Risk Characterization Implementation Plan.
1) The Plan addresses all risk evaluation activities providing.
general guidance for characterizing risk assessment
conclusions. The goal is to institutionalize a consistent
risk characterization process in Region 6.
2) The Plan emphasizes the concepts of clarity, consistency, and
reasonableness as stated by the Administrator. Region 6 will
participate in all EPA planned roundtables and workshops to
the* extent possible.
3) The Plan is consistent, in general format and purpose with
other Regions, and Headquarters Programs.
4) The Plan recognizes that full implementation is dependent
upon technical and statutory coordination with Headquarters
Programs. This coordination will be the responsibility of
each Region 6 Program* Full implementation will also require
increased, resources.
5) The Plan recognizes that full implementation is dependent
upon development of specific technology and related guidance
(i.e., statistical tools, ecological evaluation,, cost benefit
analysis, guidance for uncertainty analysis) and Program
specific characterization plans serving as S.O.P.'s.
6) The Plan identifies three risk analysis categories performed
in Region 6. Each category is defined by specific criteria.
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7) That Plan presents an inventory of Regional risk activities
with each assigned to one or more categories. A Regional
Risk.Characterization Team will maintain a listing of the
Region's various Program assessments, methods, procedures,
and use of standards,
8) The Plan defines Category III risk analyses as CERCIA and
RCRA baseline assessments.
9) The Plain considers Category ZlJt analyses as Regional
standards because they have more published guidance,
established EPA policy, and resource commitments.
10) The Plan discusses to what degree specific risk
characterization activities can be accomplished within each
Category.
11) The Plan estimates the time required to implement specific
risk characterization activities within each category.
12) The Plan suggests, an organization structure and Program
policy development plan to ensure consistency of
characterization content for each Regional Program.
13) The Plan provides for a Regional Risk Committee to be formed
providing a forum for risk assessor* and managers to monitor
and maintain consistency of Regional risk products.
14) The Plan requires risk characterization products to be
included in the deliverable* for Regionally funded risk
assessments.
15) The plan emphasizes the adherence to quality science,
documentation procedures, and Program institutionalization
of risk characterization.
16) Category I (Screening) assessments should implement the
Regional Risk Characterization immediately*
17) Category I assessments completed after the Regional Risk
Characterization Policy is approved should include
characterization sections to their risk methodology and
summary documents•
18) Category II assessments are to begin coordination activities
with related Region 6 Programs, Headquarters Programs and
Offices, and State partners to determine the feasibility of
including risk characterization sections to their
assessments.
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19) Category ZZZ assessments are to consolidate and enhance
risk characterization data and language into a specific
section for methodology and summary documents.
20) Programs with Category ZZZ products will identify needed
technical guidance documents, policy determinations, an*
Regional resources required for full risk characterization
implementation.
21) The Category ZZZ Programs vill develop a five year plan for
Risk characterization implementation.
22) The Region 6 Risk Analysis Team will be accountable for:
- communication of Regional risk activities
- coordination of cross-Program risk activities in the
Region
- reporting cross-Program activities to Senior Staff
- establishing Program consistency in risk
characterizations
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TABLE 1
List of Region * Risk Assessment Activities
Category It Screening
Category Us Intermediate
Category Ills Baseline
CSBCLX
Time critical Removals
Engineering Evaluation/
Coat Analysis (BB/CA)
RCRA
Multi-Media Enforcement
Targeting
8DW&
Risk comparisons using
MCL data
UIC risk comparisons
Hazard Ranking System (MRS)
Interim Record of Decision
Remedial Designs
Underground Storage Tanks (UST)
RBCA (EPA/State partnership)
Indirect Combustion Analysis
EPA HQ risk analyses with
promulgated standards
UIC permits
CBRCLA
Remedial Investigation/
Feasibility Study (RI/FS)
Record of Decision (ROD)
Incineration (Comprehensive
Indirect Exposure Assessment)
(CIERA)
RCR*
Facility Investigation/
Corrective Measures (RFI/CMS)
Incinerators/Boilers
(CIERA)
SDWA
EPA HQ risk analyses with
promulgated standards
era . ci*
Risk screening of ambient Fish tissue risk analysis using
water using water quality IRIS or guidance values
standards/criteria NPDES permit review/development
Hater permits (404,305)
Pesticides
Risk comparisons using
HCL/IRI8/ HA data
Pesticides
cm
Risk assessment for a given
subpopulation using
extensive fish tissue
and/or other data With
appropriate assumptions
Pesticides
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T1BLH is List of Region < Risk Assessment activities (continued)
Category Is Screening
Category II: Intermediate
category III: Baseline
CAA
Risk comparisons using air.
quality standards/mis
New Source Reviews
Air permit.
to
oo
Begioaal Initiativea
U.8 Mexico
Modeling applications
Lower Mississippi River
Corridor1
Regional Initiatives
U.S. Mexico
Model development/application
ower Mississippi River
Lower
Corridor
Regional Initiativea
special Projects
Comparative Risk
(Program specific)
Environmental Justice
(Site specific)
Multi-Media Enforcement
Targeting
special Projects
Comparative Risk
(Regional study)
Environmental Justice
(Regional/Program study)
special Projects
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TABLE 2
Glossary of Acronym* / Region 6 Bisk Related Texas
Aiz Quality Standards - Criteria Pollutants and National Ambient Air Quality
AL/PCOC (Action Level/Preliminary chemical of concern) -
AWQC (Ambient Water Quality Criteria) -
Boilers - Furnaces/incinerators producing steam for industrial use
CAA (clean Air Act) -
Comparative Risk - Regional and State analysis which rank environmental risks as to
potential Cor adverse impacts to human health, the ecology, economy, and public welfare.
CWA {Clean Hater Act) *
CERCLA (comprehensive Environmental Resource,/ Compensation and Liability Act) - Super fund
CMS/SB (Corrective Measure Study/Statement of Basis) - RCRA
CZERA (Comprehensive Indirect Exposure Risk Analysis) - RCRA
BIS (Environmental Impact Statements)- - NEPA
EJ (Environmental Justice) • Risk projects which compare demographic-data (population,
.race, and household income) for specific communities ir| Region 6.
EE/CA (Engineering Evaluation / Cost Analysis) - CERCLA
HA (Health Advisory) - SDWA, Drinking water standard
HRS (Hazard Ranking System) - CERCLA,. algorithm used to rank sites fox possible placement
on the National Priority List for Super fund.
incinerators - A furnace for burning wastes under controlled conditions.
IRIS '(Integrated Risk Information System) -
Lower Mississippi River Corridor - An area representing the southern one-half of
Louisiana. The corridor defines the river from Baton Rouge, LA to New Orleans.
MCLs (Maximum Contaminant Level) - SDWA
MCLGs (Maximum Contaminant Level Goals) • SDWA ,
Model Development' - Risk algorithms relating hazard, exposure, emissions, or other risk
factors. Computer model development is often time consuming requiring peer review,
computer specialists, extensive QA, documentation of data sources.
Modeling Applications - Use of risk algorithms to relate hazard, exposure, emissions, or
other risk factors. I
Multi-Media Enforcement Targeting • Evaluations of Region 6) industrial facilities for
enforcement prioritization. Census demographic data and TRI chemical emissions
information is used to estimate potential risk.
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TABLE 21 Glossary of Acronv»«/Ri»k Related Tens (continued)
MTD (Maximum Total Dose) - •
NAAQS (National Ambient Air Quality Standards) - Clean Air Act
NEPA (National Environmental Policy Act) - Applies to all Federal Agencies
NESHAPS (National Emissions Standards for Hazardous Air Pollutants) • CAA
NPDES (National Pollutant Discharge Elimination System) - CWA
NPL (National Priority List) Sites meeting hazard ranking criteria (HRS) for listing as
Superfund.sites.
OGWDW (Office of Ground Water and prinking Water) -
PCBs. (Polychlorinated Biphenyls) - EPA Program established to regulate disposal and
storage of PCB chemicals. '
PELS (Permissible Exposure Levels) • OSHA standards for air pollutant concentrations in
industrial environments.
Pfs (Potency Factors) * Cancer potency judgements found in IRIS
POHC (Principle Organic Hazardous Constituent)
QA (Quality Assurance)
£ RBCA (Risk Based Corrective Action) * Underground Storage Tank risk screening activity.
0 EPA and State environmental agencies are *in partnership) in implementation and use of
this ranking system. * .
ROD (Record of Decision) -.Public document describing chosen remediation alternative(s)
for a Superfund site: Document includes risk assessment conclusions and data.
RCRA (Resource Conservation and Recovery Act) - Regulations addressing the classification,
transport, disposal, and documentation requirements for solid wastes.
RfC (Reference Concentration) -
Rfb (Reference Dose) - An estimate of a daily exposure to the human population that is
likely to be without appreciable risk.
RFI (RCRA Facility investigations) -
RI/FS (Remedial investigation / Feasibility Study) - CERCLAi
Regional Initiatives - Geographic or pollution source specific risk projects specific to
Region 6 (i.e., U.S./Mexico border, Louisiana Corridor,
Petro-Chemical -Industry)
Risk Comparisons - a risk evaluation activity which uses promulgated standards (i.e. MCLs,
Rfds, HA, PELS) to judge the potential risk from a given site or pollution source.
SDWA (Safe Drinking Hater Act) •
SIPS (State Implementation Plans) - CAA
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TABLE 21 Glossary of Acronyms/Risk Related Tenu (continued)
Special Projects .- Risk analysis activities which ace generally cross-media in scope and
geographically specific.
TLVS (Threshold Limit Values) -
Time Critical Removal - CBRCLA
UIC (Underground Injection control) -
UST (Underground Storage Tanks) •
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DRAFT
RISK CHARACTERIZATION GUIDELINES
FOR
REGION IX
U.S. ENVIRONMENTAL PROTECTION AGENCY
AUGUST 1995
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TABLE OF CONTENTS
T. Purpose . . . i
II. Background 1
III. Legal Effect . 2
IV. Applicability 3
V. Relationship of risk characterization
to risk assessment and 'risk communication 4
VI. Criteria for judging adequacy of risk characterizations . 4
A. clarity - - 4
B. Transparency . . .5
C. Reasonableness • • • • • • ... . . . . . . . . . .5
VIZ. Ensuring consistency • . • •. . . . .5
VIII. Evaluating Region XX-specific circumstances . . . . . .6
IX. Content of Risk Characterizations . . 6
A. summary of key issues 7
B. summary of and confidence in the major risk
conclusions . . . ;....... . ... 7
C, Methods used ..... 7
D. Summary of the overall strengths and limitations
of the risk assessment . . . . .7
E. Placing the risk assessment in context with
other similar risks . . . 8
F. Other information .................. 8
G. Mechanisms to evaluate risk characterization . . . . 8
X. Statement of Commitment .......... 9
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I.
This Draft Risk Characterization Implementation Guideline
(the Guideline) provides the operational framework for developing
risk characterizations in Region IX. The Guideline builds on the
Administrator1 s March 21, 1995 memorandum on Risk
Characterization including the Policy-, Elements, and Guidance
documents. It describes Region IX-specific factors which guide
the implementation of the Risk Characterization Policy. The
Guideline identifies the kinds of risk assessments produced in
Region IX and describes how the Risk Characterization Policy will
be reflected in each type of assessment.
The primary objective of the Risk Characterization Policy
"... is to provide a better understanding for the basis for our
decisions and our confidence in the data, the science policy,
judgements and uncertainty in the information base . . . " . This
draft Guideline is amendable based on a Region IX review of
policies and procedures for several key issues. that cut across
Agency programs (e.g., uncertainty analysis, training program for
risk managers and updating .and supporting with resources the
Integrated Risk Information System (IRIS).
XI.
In 1984, the National Academy of Sciences defined risk
assessment as involving one or more of the following four steps:
hazard identification, dose-response, exposure assessment and
risk characterization.. The Administrator' s memo stated that risk
characterizations will.be-written "in a manner that is clear,
transparent, reasonable and consistent with other risk
characterizations of similar scope prepared across programs in
the Agency." Specifically,, the risk characterization should:
1. Integrate the information from the hazard
identification,. dose-response, and exposure
assessments, using a combination of qualitative
and quantitative information.
2. Include a discussion of uncertainty and
variability^
3. Present risk conclusions and information regarding'
the strengths and limitations of the assessment.
It should also be responsive to the risk questions
raised by the risk manager, the stakeholder and
the public during the preparation of the risk .
assessment. .
Moreover, the Administrator! s memo, stipulated that:
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1. Conclusions drawn from the science will be
clearly delineated from policy judgements, and the
use of default values or methods or assumptions
will be clearly, explained..
2. Key. issues and conclusions of each risk assessment
component will joe summarized appropriately,
including a description of the overall strengths
and limitations of the assessment and its
conclusions.
3. While consistency in general format is preferable,
the unique characteristics of each specific
situation or public involvement will be also
recognized.
4. A discussion will, be prepared that will compare
the risks identified in the risk assessment with
other similar risks. The discussion should
include the limitations and usefulness of such
comparisons, comparisons with other chemicals or
situations, or situations familiar to the public.
5. A clear and transparent risk characterization will
enhance the effectiveness of the risk .
communication effort* which is a process used by
EPA and the public to discuss environmental
hazards, their impacts and how they should be
addressed. Risk communication embodies a two way
communication process that addresses the different
perceptions of risk held by the Aaencv.
stakeholder and the oublic.
The additional amount of time and level of detail devoted to
risk characterization in Region IX should vary according to the
nature and magnitude of the risk assessment, as well as the
number of risk issues that are- generated by the risk manager, the
stakeholder and. the public.
This Draft Guideline document and associated guidance on
risk characterization do*not establish or affect legal rights or
obligations. Rather, they confirm the importance of risk
characterization as a component of risk assessment, outline
relevant principles, and identify factors that staff from Region
IX should consider as they implement this policy.
The Draft Guidelines and associated guidance do not stand
alone; nor do they establish a binding norm that is finally
determinative .of the issues addressed.. Except where otherwise
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provided by law, Region IX' s decision on conducting a risk
assessment in any particular case is within Region IX' s
discretion. Variations in the application of this policy and
associated guidance/ therefore, are not a legitimate basis for
delaying or complicating action on Region IX 's or Agency
decisions.
iv.
Except where otherwise provided by law, and subject to the
limitations on the policy's legal effect discussed above, this
Guideline applies to risk assessments prepared by EPA and to risk
assessments prepared by others that are used in support of EPA
decisions.
EPA will consider the principles in this policy in
evaluating assessments submitted to EPA to complement or
challenge Agency assessments. Adherence to this Agency-wide
policy will improve understanding of Agency risk assessments,
lead, to more informed decisions, and heighten the credibility of
both assessments and decisions. Thus a clear and transparent
risk characterization can add to the trust and credibility that
EPA is trying to achieve with a concerned public.
It is Region IX policy that each risk assessment prepared by
or for Region IX should contain a risk characterization that is
responsive to the risk questions raised by the risk manager and
the public and at a level of detail appropriate for the type of
assessment. The risk assessor will clearly identify the scope of
the assessment and the reason(s), .if any, for deviating from
.certain factors outlined in the "Elements" document accompanying
the Administrator's Risk Characterization Policy.
The risk characterization will:
1. Clearly define the scope of the assessment, integrate
the information in the risk assessment, be responsive
to th» risk question* raised by the risk manager or the
public, discuss the uncertainties and
variabilities, and
2. Clearly define the data quality, both the strength and
weaknesses, and assumptions used in the assessment.
Region IX will also apply the general principles specified
in the Risk Characterization Policy to its assessments of
ecological risk when detailed Agency guidance becomes available.
In the interim, risk characterizations involving ecological
effects developed by this Region will strive to include a
discussion of the strengths and limitations of the assessment and
will reflect the risk characterization values of clarity,
transparency, consistency, and reasonableness.
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Cost-benefit analyses will not be described in this
Guideline until'Guidance is available from Headquarters.
V.
As stated in the Risk Characterization Policy, "Risk
Characterization is the summarizing step of risk assessment. The
risk.characterization integrates information from the preceding
components of the risk assessment." In other words, while risks
can only be partially described by the individual components of a
risk assessment,- risk characterization is a conscious and
deliberate process of integrating all important considerations.
and significant questions about risk into an integrated picture.
The risk characterization provides the risk manager with an
integrated view of the interaction of the individual components
for better decision making. The risk characterization also
provides valuable information that is useful in risk
•communication and public involvement.
A clear and transparent risk characterization can be a
powerful tool for risk communication. While the risk
characterization policy addresses the interface between risk
assessment and risk management, rick communication emphasizes the
establishment of trust and credibility through the two way
communications process of discussing health/risk information with
individuals, communities 'and stakeholder.
VI. criteria for •frvfcHjMt adeflUflCTY Of risk Characteri
The criteria, for determining whether Region IX* s risk
characterizations meet the Administrator's four values are
summarized below and* further expanded in sections vil and IX of
this document.
A. Clarity of risk characterizations will be determined by
whether:
1. The language and organization of the risk
characterization are understandable and responsive to
the questions raised .by the risk managers;
2. The purpose; of the risk assessment is defined and
explained (e.g., regulatory purpose, community
concerns, policy analysis, and priority setting);
3. The assessment's level of effort (e.g., screening, in-
depth and community based characterization) is defined
and discussed;
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4. The strengths and limitations, including the
uncertainties and variabilities of the assessment are
clearly defined along with technical terns;
5. Key scientific and policy decisions, and assumptions
used in the assessment are•identified and clearly
described; and
6. Unique deviations from the standard specific to a
particular risk assessment are fully discussed and
explained.
B. Transparency of the process used.to characterize risk will
be determined by the extent to which:
1. Conclusions drawn from scientific and technical
information are identified separately from policy
judgements; and
2. The risk characterization assures that all relevant
portions of the risk assessment paradigm were
addressed.
C. Reasonableness in the risk characterization will be
evaluated by whether:
1. All components are integrated into an overall
conclusion of risk which .is.complete, informative and
useful in decision-making and for risk communication
and public involvement;
2. Conclusions are based on the best'available scientific
policy information and judgement with appropriate
source documentation; and
3. Informed judgement, sound science, and science policy
and scientific uncertainty are acknowledged.'
VII; I
Consistency in definitions and'methods of assessing risk is
fundamental to minimizing confusion about risk estimates
generated across the Agency. However, while risk assessments
conducted in Region IX share similar goals with risk assessments
prepared by other parts of the Agency, statutory requirements,
regulatory.interpretations, level of public concerns and state
policies influence Region IX risk assessment approaches. The
following sections describe situations where Region IX can use
Agency-wide definitions, methods, and risk descriptors to ensure
consistency, and areas where such use is constrained.
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The following procedures used by Region IX ensure that its
risk characterizations are consistent within the Region and with
characterizations elsewhere in the Agency. Region IX uses:
1. Agency-wide and program-specific guidance, such as
those for exposure analyses and health risk assessment
(e.g.,cancer guidelines, risk assessment guidance for
superfund}?
2. Agency or program specific consensus.information
systems, such as the Integrated Risk Information System
(IRIS), which are produced by Agency-wide workgroups;
or HEAST which is generated by QRD for OSWER.
VIII.
TV... uTimt-if <«*• el
In accordance with the Risk Characterization Policy,
considerations within Region IX which affect the scope to which
risk characterization can be accomplished include statutory
requirements, court-ordered or regionally imposed deadlines,
state/EPA agreements, public concerns and involvement, data
and/or information, and resources. Region IX* • risk assessments
can be categorized into screening level, In-depth assessments and
community based. Examples of risk, assessments within these
categories are:
X. A screening-level analysis of preliminary remediation
goals, for an operating unit at a superfund site,
2. An in-depth baseline risk assessment for a Federal base
closure involving 250 different waste units, tens of
chemicals and multi-media exposure*, and
3. A'community baaed risk, assessment to evaluate risks
from ambient exposure to a mixture of pesticides that
drift from farmland to urban housing.
The risk manager should be able to' use the information in
the risk characterisation for decision-maXing, to respond to his
or her risk issues., for communicating risks and for public
involvement.
IX. Content of risk characterization*
This section focuses on the guidance for risk conclusions
and comparisons provided in the "Elements" document of the Risk
Characterization Policy, including:
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A.
Region IX risk characterizations should clearly summarize
the key components and issues, conclusions, and rationale from
each state pf the risk assessment paradigm. The characterization
should be responsive to the key risk issues raised by the .risk
manager, the stakeholder and the public during the development of
the risk assessment. A key issue identifies and summarizes those
pieces of information that were critical to the evaluation.
B. fimnnmrv of and confidence in the major* risfc conclusions
Region IX risk characterizations should clearly present risk
conclusions. Questions articulated by the risk manager should be
answered. Risk characterizations should include a qualitative
statement of the major risks, what they mean, their significance
and the confidence in the estimates of those risks.
C. Method* used
Region IX will use Agency-wide and program-specific guidance
to generate risk estimates and include a discussion of the
results' of the analysis to ensure that all parties; the risk
manager , the stakeholder and the public understands the meaning
of the numbers.
D. giimmnrv of th* overall Bfrr^iyEh* and limitations of the risk
assessment
Region IX will discus* in clear, concise language the
strengths', .significance and limitations of the assessment
including the major uncertainties associated with each component.
The discussion should include:
1. A review and summary of the major strengths, limitations
and uncertainties for each component of the assessment.
2. A discussion of the significance of , alternative
conclusions that are also supported by the data,
including:
a discussion of alternative dose-response or
exposure models, or other sampling schemes, and
an evaluation of different susceptible and exposed
subpopulationsi including children, the old, the
typically and high end exposure groups, individual
exposure vs population exposure, high background
exposures (natural or cumulative exposure such as
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in environmental justice areas), in the exposure
assessment.
3 . Identify significant strengths ( key chemicals of
concern and the supporting toxicity data base,
important exposure pathways, quality of the sampling
and modeling and the inclusion of the significant
exposure populations), identify which components
significantly affect. the risk estimates as well as the
data gaps and distinguish between policy-based and
scientific judgement and uncertainty.
4. Indicate where scientific judgements or default
assumptions were used to bridge .information gaps, and
explain the strengths, limitations and basis for these
judgements and assumptions.
E. Placing the risk aaaaaanient in context wittj other
similar riaka
A discussion of how a specific risk compares with other
risks of similar nature requires careful consideration.
Concerned communities that raise .health/risk issues react
negatively to risk comparisons} especially when a community has
not asked 'for the comparison. A community will often interpret
the risk comparison with skepticism and believe that the Agency
is txving to downplay the magnitude of the specific risk that.
they are concerned about. The discussion should include the
limitations of such comparisons, the. usefulness, comparisons with
other chemicals or situations, or similar situations familiar
with the public.
F« Other information
The description of other : information useful to the risk
manager or the 'public, will include:
1. Informing the risk manager /public about the scientific
confidence in the. data, answering the risk
manager's/public risk questions, and the identification
of the science or risk policy issues that remain
unanswered.
2. Socioeconomic considerations.
G. Meehariiamo feo evaluate rialf characterization
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Management involvement is required to ensure compliance
with the:policy, to guide and evaluate its success, and to make
necessary improvements. The actions Region IX will take to
establish effective mechanisms for implementing, evaluating and
improving its risk characterization guidelines are:
1. Provide training for risk assessors, managers and the
public. Region 9 is a leader in the Agency in risk .
assessment'and risk communication training. This
policy, along with the new changes in the cancer
guidelines and increasing requests from communities for
risk training will place additional demand to improve
the risk managers and the publics understanding of risk
assessment, the.science, the policy, the assumptions
and all of the uncertainties.
2. Develop an approach to ensure that each risk assessment
and briefing contains a risk characterization
consistent with this guideline.
3. Peer-review will follow the Region' s Standard operating
Procedure.
Through this Guideline, Region XX intends to ensure that
risk characterizations produced by and for Region'IX will be
consistent with this Guideline and with Agency guidance and
policy on risk characterization, recognizing limitations in time
and resources. The Guideline will b« updated as necessary.
Regional Administrator
for Region IX
Data
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THE SUPERFUND ASSESSMENT PROCESS
The Superfund program responds to "releases" of hazardous substances into the environment.
"Releases" include the improper disposal of hazardous substances as well as leaks from storage
tanks and spills due to transportation accidents. The Superfund program uses the following
phased approach to investigate hazardous waste sites.
Preliminary Assessment (PA)
Review federal, state, and local government permit and judicial files
Interview federal, state, and -local government personnel
Examine records regarding past and present ownership and use of the property
Analyze available geological, topographical, and hydrogeological data
Visually inspect the site when possible
Site Inspection (511
• Collect limited site-specific data to determine the nature of the release (usually not
more than 30 samples including background and QA)
• Identify potential exposure pathways and receptors
• Evaluate data to determine whether the site should be considered a candidate for
cleanup
• Perform emergency removal if the release is considered an immediate threat to
human health or the environment
• identify potentially responsible parties
• Propose site for inclusion on the National Priorities List (NPL). Findings subject
to notice and comment
Remedial Investigation (Rh
• Sample to fully' characterize the nature and extent of contamination
• Evaluate if site media are contaminated above applicable Federal and State
standards
• Perform Baseline Risk Assessment
Evaluate current and potential future exposures
Support the decision whether to take remedial action
- Document the magnitude of site risk and its primary sources
Support the selection of cleanup levels
Summary of Current Approach to Baseline Risk Assessment
• Hazard Identification
Extensive analytical sampling data reviewed
Chemicals of greatest concern selected based on their concentration,
toxicity, mobility, persistence, and bioavailability
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Dose-response Assessment
^ely heavily on toxicity assessments developed by ORD
Adjustments made to site-specific estimates of dose for certain chemicals
oased on bioavailability
Exposure Assessment
Emphasis on chronic/long-term average exposures
Exposure point concentrations derived from both sampling data and
models
Quality and quantity of data documented
Exposure descriptors most commonly addressed are central tendency and
high-end individual risk (e.g., reasonable maximum exposure, RME), and
highly exposed subpopulations (e.g., childhood exposure to soil)
Cumulative exposure addressed as likelihood of an individual being
exposed to multiple chemicals in the same medium or across media
Description of Site Risk
Estimates of cancer and non-cancer risks traditionally reported as a single
number for each exposure described.
Assumptions used in the assessment clearly documented
Uncertainties primarily addressed qualitatively
Superfund regulation directs that site managers focus on risks to the RME
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RISK CDtiUkCTH&XIlXXaV OOXDBZiXMBt
TOR
THB OFTXd Of 8OLXO TO9YB
moon itti
F-47
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OF UUMTUT8
t
I. Purposa . . . .1
IZ. Background . . . . . . . . 2
III. Lagal Bffact..-.. . . . . . . . . • • • •• . .4
ZV. SCOpa . . . ... . ..... . .•••"• . . . . » . ,. . . . . 4
V. Relationship of risk characterization
to risk aMMnent and riak covaunication ........ 7
VI. critaria for judging adequacy of riak charaetarizationa .8
A.. Clarity k ...... s
B. Transparency ... .................. 9
C. Raaaonablanaaa .................. 10
* • ' ' . •
VII. Ensuring eonaiataney . . ..... ... . . . . . . . . . 10
VIII.Bva3.uating Offio«~apacifio oiremurtanoaa ........ 12
IX. Pointa to conaidar vhaa praparing riak eharaetarieationa
and critaria for avaluating coaplianca vith tna Riak
C&aractarization Policy . « ................ 13
A. Summary of and confidanca in tha major riak eoneluaiona
...... ... . . . * ... h ,. .....'.. 14
B. Summary of kay iaaua» ............... 15
C. Kathoda uaad . ^ ............... . .' 16
D. Summary of tha ovarall atrangina and uncartaintiaa
of tha riak aaaaaamaht ......... 17
E. Put thia riak aaaaaamant in eoataxt vith
othar aimilar rick*.. ............... 19
F. othar information . . . . i, .............. 20
6. Machftntama to avaluata riak charactarization ... 21
' *
X. Statamantr of Commitmaat ................ 22
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Z.
This Risk Characterization Implementation Guideline provides
the operational framework within which all risk characterizations
in the Office of Solid Haste (OSW) are developed. The Guidelines
expand on the Harch 1995 Risk Characterization Policy and its
accompanying Guidance by providing OSW-specif ic factors which
affect the implementation of the general policy.
The implementation Guidelines identify the kinds of
assessment* produced by OSW which are covered by the Risk
Characterization Policy, and addresses how the. principles and
.guidance will be reflected in each of them. Where significant
principle -or guidance points -cannot be incorporated, these
• * • •
guidelines call on producers of risk characterizations to provide
reasons for such gaps*
The objective of the Risk Characterization Policy and this
* • •
Implementation Guidelines document is to ensure that risk
characterizations produced by this Program form a coherent
picture at a level of detail appropriate for the decision being
supported. Accordingly, greater emphasis is placed on ensuring
clarity, consistency,1 and reasonableness of the risk picture and
transparency of the risk assessment process as an input, to the
decision-making process than on reformatting or otherwise
reiterating the conclusions of risk assessment components that
precede the characterization.
.EPA is developing policies and procedures for several key
issues that cut across the Agency (e.g., uncertainty analysis,
updating IRIS and supplementing IRIS with risk characterization
language in the interim, etc.) . As they are developed they will
become part of OSW*s policy and update this document.
II. Ba,elcg
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In Match 1995, the Administrator issued a policy statement
requiring that risk charact«rizatioti« be prepared "in a manner
that is clear, transparent, reasonable and consistent vita other
risk characterizations. of similar scop* prepared across programs
in the Agency.11
The "Guidance for Risk Character ization*, which accompanies
the Policy Statement, provides general principles for
characterizing risk* These principles are as follows.
1. The risk characteritation integrates the
information from the hatard identification, dose*
response, and exposure assessments, using a
combination "of qualitative information,
quantitative information, and information about
uncertainties.
2. The risk characterization -includes » discussion of
variability*
3. Hell-balanced risk characterizations present risk
conclusions amd iaf ormatioa regardimg the
strengths and limitations of the assessment at the
level appropriate for the risk assessment.
Uso identified in the '•Policy for. Risk Characteritation" are the
'olloving key aspects .of risk characterizations:
l. RisX assessments should be transparent, in that the
conclusions drawn from the science are identified
separately from policy judgments, and the use of
default values or methods and the use of assumptions in
the risk assessment are clearly articulated.
2. Risk characterizations should include a summary of the
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key. issues and. conclusions of each of the other
components of the risk assessment, as well as describe
the likelihood of harxu The summary should include a
description of the overall strengths and limitations
(including' uncertainties) of the assessment and
conclusions.
3. Risk characterizations should be consistent in general
. format, but recognize the unique characteristics of
each specific situation.
4. Risk, characterizations should include, at least in a
qualitative sense, a discussion of how a specific.risk
and its contest compare with, other similar risks. This
may be ftcffflpplighed by comparisons with other chemicals
or situations in. which the Agency has decided to act,
or with other situations familiar to the public. The
discussion should highlight'the limitations of such
comparisons.
5. Risk: characterization i»"a key component of risk
communication, which is an .interactive process
involving exchange of. information and expert opinion
* —
among individuals, groups .and institutions.
Risk assessments conducted by OSW require different levels
of effort. They should .be viewed as. a continuum, because more
than one level of risk assessment effort may be employed for many
OSW actions and activities* Risk assessment activities conducted
to support one level of effort may lead to a different level of
effort as the requirements for the assessment and its intended
uses change. The' amount of 'time, effort and level of detail
devoted to risk characterization in OSW should vary according the
nature and magnitude of the risk assessment.
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Rsprasantativa asaaaamant* dona in OSft, including tha •cop*
'of tha 'asMSSBsnts" and tha laval of detail, ara described balov:
1. Basalina Risk Assassmants for Hazardous Wast* iisting
Datarsinationa. Multiaadia assaaamanta to datarsina
vhatoar cartain apacif lad vaatas should te li»t«d a«
hatardoua. AMMOMntc ranga frcm conaarvativa
•craaning laval ona» to alimlnata vwtw from f urtter
con»idaration to aor» ccaqplax onaa for thoaa vartaa
Which may ba liatad.
2. othar Hagulatory Datar»iTtaiion« (ha«ardou« va«ta
idantif ication rula, hazardous waata combiiation
amiaaion •tandarda, caaant kiln duct ragulatory
aaaaaamant, ate.) • Coaplaac Mlt imadla aaaaaaBanta to
datariaina appropriata ragolatory stratagiaa and/ or
3. 8ita»apaoitio baxardou* vacta eoabiurtion
aaaaaa»antc- -(guidane* and aaaiatanoa to Bagioai and
stataa). Mffltiaadta aaaaaavants rang* from •eoraaning
lava! to highly coaplax, dapanding cm potential risk at
a facility.
II.
. Thia iaplaaantation gnidalinaa docmaant and aaaociatad
Idanca an riak coaraotarlsatlon do not aatabllah or af f act
ral righta or obligation*.. Ilatbar, thay eonf im tha ia^ortaaca
riak charactarisatioB a* a onayonant of risk aaaaaa«anty
lina ralavant principlaa, and idantify factors that ataff from
should consider as thay iaplaaant this policy.
Tha tffplOTMiirtT€l;t'ffn guidallnaa ai*4 associatad guidanca do not*
I alona; nor do thay aatabliah a binding norm that is finally
F-52
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determinative of the lames addressed. Except, where otherwise
provided by law, OSH*s decision on conducting a risk assessment
in any particular case is within OSW's discretion.. Variations in
' • : •
the application of this policy and.associated guidance,
therefore, are not a legitimate basis for delaying or
complicating action on OSW or Agency decisions.
IV. fiflfifie.
All risk characterizations prepared by OSW in support of
decision making at EPA are covered by the Administrator's Risk
Characterization Policy.and this implementation guidelines
document. Discussion of risk in all OSW-generated reports,
presentations,'briefings, decision packages, and other, documents
should be substantively consistent with .the policy and this
document.
osa relies largely on Agency positions and documents for
many aspects of its risk assessments. Two key examples are the
IRIS data base and the "Exposure Factors Handbook". When
-utilizing this information; OSW depends on whatever is provided
in these documents and data bases. To the extent that these.
Agency sources do not yet meet the full requirements of the Risk
Characterization Policy, OSW's assessments will have the same
deficiencies. The Agency is working to ensure that these sources
will be brought, into compliance with the policy.
Risk assessment.information is often filtered through
several layers of management before reaching the ultimate
.decision maker. In OSW, reasons should be given for filtering
out any risk characterization information during .this process.
It'is OSW policy to require -that each risk assessor prepare
a risk characterization for each risk assessment. Each risk
assessment prepared by or for this Office should contain one or
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more sections on- .risk characterization at a level of detail
appropriate for the type of assessment. -The risk assessor will
clearly identify the scope of. the assessment and the reason (s) ,
if any, for not considering certain factor* outlined in the
"Element*" document accompanying the Administrator's Risk
Characterization Policy* The guidance to risk assessors, and the
criteria by which they can be judged, on thi» point, are that
they:
A. qi
1. Note., with a brief explanation, categories of hazard
end-point* (including ecotoxicity) that are
specifically excluded from the review.
2. Also note populations which are specifically excluded
from review.
B.
1. Give an idea of the types and quantity of data sources,
reviews, and databases that were utilized.
2. If it is an extensive review, it is especially
important to indicate all major sources of information,
and to highlight any major source not utilized with the
reasons why.
Documents that describe components of a risk assessment
(e.g., stand 'alone hazard or exposure assessments), even if
prepared as separate documents, will also follow the risk
characterization policy in that they .will strive for -clarity,
transparency, consistency,, and. reasonableness.
Documents related to risk or any of its components which are
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submitted to this office toy EPA contractors or other EPA Offices
are expected to follov the Risk Characterization Policy.
It is OSW's policy that documents from sources outside'EPA
that this Office relies on in preparation of risk assessments
will be augmented by adding risk characterization language to
meet the requirements of the Risk Characterization Policy.
It is OSW policy to clearly explain any circumstances where
assessments, and other information such as IRIS, have been
produced in the past by EPA but which do not fully follov the
risk characterization principles. Additional guidance on how the
use of IRIS and other information systems and documents produced
by ORD and others, that serve as inputs to OSW generated'risk
assessments will be developed by the Science Policy Council..
This * document will be updated when such guidance is received.
Documents submitted by the public to this Office that relate
to risk assessment or any of its' components, including those that
support alternatives to EPA risk assessments, will be evaluated
in light of the Risk Characterization Policy and this guidelines
documenti
OSW will apply the general principles specified in. the Risk
Characterization Policy to its assessments of ecological risk.
Specifically,, until .detailed Agency guidance becomes available,
risk characterizations-involving ecological effects developed by
this Program will strive to include a discussion of the strengths
and limitations of the assessment and vill also strive to achieve
.the Risk Characterization values of clarity, transparency,
consistency, and reasonableness.
Assessments of benefits are not included in this
Implementation Guidelines. Although this Office acknowledges
that the principles of clarity, transparency, of process,
' F-55
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consistency,, and reasonableness apply also to analyses of
benefits, the Agency has not yet developed guidance for these
types of assessments.
V.
* *_ je*we»em»*«Ji ^ MSI ^4 Mem*
As stated in the Risk Characterization Policy, "Risk
Characterization is the summarizing step of risk assessment. The
risk characterization integrates information from the preceding .
components of the risk assessment. • In other words, risks can be
partially described. by the individual components of a risk
assessment, but risk characterization is a conscious and
deliberate process of bringing all important considerations about
risk into an integrated picture.. Even more importantly, as an
picture, the risk characterization is not simply a
reiteration of conclusions of the various components/ but a piece
which foeusses on how those components interact.
"Risk characterization11 is not synonymous with "risk
communication* The risk characterization policy addresses the
interface between risk assessment end. risk management. Risk
communication, in contrast, .emphasizes the process of exchanging
information and opinion vita the public. While the final risk
assessment document (including its risk characterization
sections) is available to the public, the risk communication
process is better served by separate risk information documents
designed for particular audiences.
Therefore, this risk characterization guidelines document is
Written to provide guidance to the risk assessor for, his/her use
in explaining the assessment to risk managers. If this guidance
is followed, the resultant risk characterizations should also be
understandable to an educated and motivated layperson.
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VI
The .criteria for judging the extent to which OSW'» rink
characterization* meet the 'Administrator'* four values are
summarized below and further expanded in sections VII and IX of
this document.
A* Clarity of risk characterizations will be judged by the
extent to which:
1. Brevity is achieved and jargon is avoided;
2. The language and organization of the risk
characterization are understandable to EPA risk
managers and the informed lay person;
3. The purpose of the risk assessment is defined and
explained (e.g., regulatory purpose, policy analysis,
priority setting) ;
4. The level of* effort (e.g., quick screen, extensive
characterization) put into the assessment is defined
accompanied by the reason (s) why this level of effort
was selected;
5. The strengths and .limitations of the assessment can be
understood without needing to understand the technical
details of the 'assessment. .To the extant they are
used, technical terms are defined;
6. '.The scientific and policy .bases, including biases (e.g.
to err on the side of safety), -used in the assessment
are clearly described;
7. Assumptions are defined and. understandable explanations
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are given for each policy decision mad* for that
particular risk assessment (e.g., use of default
assumptions); Agency policy decisions such as the use
of. linearized cancer models are generally not disussed
for each risk assessment; and
8. Unusual .issues specific to a particular risk assessment
are fully discussed and explained.
B. Transparency of the process used to characterize risk will
be judged by the extent to which:
1. Conclusions drawn from the science and technical
information are identified separately from policy
judgments;
2. The characterisations incorporate the principles of the
risk characterization policy (e.g., the assumptions are
,»•*•• '"."*
explained, the strengths and limitations of the
assessment .and the uncertainties are addressed in a
balanced manner);
3. The risk characterization does what it sets out to do
in an appropriate manner (e.g., it meets the expressed
' ' * * » , * *
purpose, the level of effort expended was appropriate
for the decision made, all relevant .portions of the
risk assessment paradigm were addressed) .;•
C. The extent to which risk assessment conclusions and risk
characterizations are reasonable will be judged by whether:
1. They are determined to be reasonable by EPA risk
managers and the lay public;
2. &11 components are well integrated into an overall
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conclusion of risk vhlch is complete, informative and
useful in decision-making;
3. They are based on the best scientific information and
judgment readily available to OSW, with sources
documented appropriately;
4. They use common sense and portray the use of science
and science policy to assess risk in a forthright
manner, acknowledging scientific uncertainty;
VIZ* *n«m»iiig Conelatency
Consistency in definition* and methods of assessing risk is
fundamental to minimizing confusion about risk' estimates
generated across the Agency; OSW attempts'to ensure that risk.
assessments, done within the office are consistent in 'their
general approaches, selection, of models, exposure assumptions,
and information sources. Since the state of the art and
availability of information are continually evolving, current
risk assessments may differ-(sometimes considerably) from those1
done in the past.
As indicated previously, there may be significant
differences in the level of detail and complexity among OSW risk
.assessments, depending on the magnitude of the decision, the time
available, and whether the assessment represents an initial
screening or a more detailed assessment dictated by an initial
screen.
The following procedures used by osw help to ensure that its
risk characterizations are consistent with characterizations
produced by other parts- of the Agency. They also serve as
criteria by which our success at ensuring consistency can be
judged.
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1. OSW relies on Agency-vide guideline*, such as those for
exposure analyses and health risk assessment.
2. OSW uses. Agency-vide information system, such as* the
Integrated Risk Information System (IRIS) and risk
reference concentrations (RfCs) which are produced by
Agency-wide, consensus workgroups.
3. OSW1* risk assessment* are done as part of the
development of regulations which require Agency-vide
work groups whose review includes the risk assessments.
4. OSW actively solicits input from other offices with
expertise in specif ic risk assessment areas; for
example OPPT for structure/activity analyses of
chemicals, ORD f or exposure assessment parameters, and
Off for effects on aquatic life.
5. OSH includes substantial, input from the Regional
offices in developing -procedures and guidance for
conducting site-specific risk assessments for hazardous
Waste combustion facilities.
6. OSW solicits review and assistance from ORD and OPPT
whenever the Office needs, to develop toxicity "numbers"
for chemicals not on the IRIS data base.
VIII
The Risk Characterization Policy recognizes that *[t]he
nature of the risk characterization will depend upon the
information available, the regulatory application of the risk
information, and the resources (including time) available." The
types of risk assessments performed by OSW were described in
Section II. Considerations specif ic to OSW which affect the
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degree -to which risk characterization can be accomplished include
statutory requirements, court -ordered deadlines, availability of
data and/ or information (e,g. , lack of health effects or exposure
data) , and amount of resources available to conduct the risk
assessment and risk characterization.
XX* ' Points fo Congi^*** Wlieii Preparing Ri«k GhejreBtegi.yeti.one
fey BvaTtiip tiflCf Cfl^pii***ge with the ttiek
Polic
The_ Administrator's March i995 Risk Characterization package
provides a list of elements to consider when assessing risk to
human health (see appendix) . That list of elements will be .used
by OSW. as the basic set of considerations for each risk
assessment and risk characterization that the Office performs,
recognizing also, however, that there will be reasons for
expanding or contracting that basic set of elements to fit the
circumstances of a' particular case. In modifying the- list of
elements, this Office will clearly state in the risk
characterization the reasons for- adding to or subtracting
elements from that basic list. Such reasons may be written at a
general level to cover several elements at once, or may.be.
written at a very specific level to cover a specific element,
depending on the level of decision being supported.
• The following discussion expands on 'the summarization and
.integration aspects, of risk characterization, as a supplement to
Part Two of the pElements Document^ provided in the
Administrator's package. The . discussion is meant to give further
explanation to risk assessors of the kinds of specific
information that may be relevant to OSW that will help decision-
makers form a clear, coherent, and integrated picture of risk at
the level of detail appropriate for the decision.
This. section contains points' to consider when characterizing
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risk. These point* focus on the principles and key aspects of
risk characterization discussed in Part Two of the "Elements
Document", Whan special circumstances (e.g., lack of data,
resource limitations, statutory deadlines) preclude addressing
particular issues or factors contained in this section/ such
circumstances will be explained and their impact on the risk
assessment discussed.
In addition to the criteria for clarity, transparency,
consistency and reasonableness discussed earlier in this
document, QSW has adopted the following policy that applies to
the three principles and six key 'aspects of Risk Characterization
addressed in Section II to help its staff comply with the
Administrator's Risk Characterization Policy. The following
points should help OSW's risk assessors characterize risk. These
points also provide criteria that can be used by risk managers to
get the most out of risk assessment brief ing* and to evaluate the
assessor's performance in characterizing risk.
A. gipmaary of and Confidence in the tfajoir Risk Coneluaiong
In preparing risk characterizations for OSW, risk assessors
should present a brief statement of the bottom line of their risk
conclusions in simple clear language. In order. to prepare
effective risk characterization*, risk assessors should give a
qualitative idea of the major risks and their confidence in the
estimates of risk and conclusions.
The risk manager should be able to read this and know what
are the major rick* (or potential risks) to what individuals and
populations, and have an idea of whether the conclusion is
supported by a large body of data or if there are significant
data gaps. Explain in a qualitative narrative any quantitative
estimation of risk to assure that the reader understands the
meaning of the numbers.
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B« Simmayy of Kay Tgauag
Successful risk characterizations in osw require that, risk
assessors summarize in clear, concise language the lud. issues,
conclusions, and rationale from each stage of the assessment
paradigm (i.e., hazard .identification, dose-response evaluation,
exposure, assessment, and/or the integration of these
considerations into a risk assessment) .
x key i««ne is one that is critical in order. to properly
evaluate the stated conclusion. The idea is not to repeat the
entire hazard, or exposure assessment, but to summarize and
identify those pieces of information that were critical to the
evaluation, so that the risk manager will be alerted to the major
issues and conclusions that are the bases of the assessment.
. *•
Short conclusion statements from the assessments can be repeated,
or, if. the assessment conclusions are lengthy, summarized.
In looking at the vhbl* risk picture there may be issues.
•• '. . . f t
which should be brought to the risk manager's attention. For
example,' is there a major imbalance in the assessments, such that
there is a strong case for hazard, but lack of data, or. great
uncertainty for exposure; or vice versa.
Cuidanea to fehe iriak ««««««Qyg* pritayja tor Hudainer how
e. 4«lt iti 'tiaJT* jftgtnuanfea and
1. Briefly discuss the key issues from the reports, or data
sources, used to make the risk assessment; and
2. Look at the whole risk picture and bring issues to the.
risk manager's attention. For example', is there a major
imbalance in the. assessment, such that there is a
strong case for hazard, but a lack of data, or great
uncertainty for exposure, or vice versa.
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C. Mot-hods Uaad
Standard Agency methodology is generally followed to
generate risk estimates for each category of assessment conducted
by OSW. When quantitative risk evaluations are performed for
OSW, the resultant risk numbers should be narrated qualitatively
to ensure that the reader understands the meaning of the numbers.
When extensive risk assessments are performed, the risk assessor
is likely deviate from using default methodology. Such departures
should be highlighted in the risk characterization.
The mathematics of the risk calculations are not intended to
be fully articulated in the risk characterization. However, the
risk manager should -be provided with qualitative "feel11 for the
numbers.
for udin fcha miee*»«« Vt-fch nhteti
*»fo<»1* In briaf-tnam ami in
1. Explain the meaning of standard Agency interpretations
of risk values, (e.g., the hazard quotient) if they are
not explained elsewhere.
2. Explain any specific methodology that Bight be easily
misinterpreted, (e.g., the use of eootoxicity
population models)-.
3. If technical data are presented in numerical terms,
qualitatively discuss the data, as well. In this regard,
the use of tables and graphics is strongly encouraged,
including sufficiently descriptive titles and
narrative.
fititimmyv of the Overall Staf^tierfc'ha un "neeytfri-ftti.es 'of fcha
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Rislc AflaeaaiBBnt
Discuss in qualitative tens, din clear, concise language the
overall quality of the assessment, and .the major uncertainties
associated with each of its components. The 'idea is to relay to
the risk manager in frank and open terms the strengths and
weaknesses of the assessment..
An example of possible strengths of an assessment would be.
that the overall weight of evidence of the data indicates that
the quality and quantity of .data supporting the hazard _and/ or
exposure is 'high. There might also be general consensus within
the scientific, community on certain points used to build the
hazard/ exposure case. The risk manager needs to know the amount
of uncertainty in each of the assessment areas, and in the final
risk conclusions.
and eri-teria £ or • *
, ^
succeaa in eonv»ylTtg' the «tn*»ngrtiha fl||d fftieaart a i. titles of the
Risk ABB
1. Identify any uncertainties in the "source term"
information '< i.e. emissions data, etc.).
2. Review the major uncertainties presented in the .
characterisations for each component of the risk
assessment paradigm and summarize them.
3. Discuss the incomplete knowledge and absence of
•consensus concerning scientific phenomena which were
evaluated in the risk assessment*
4. Apprise the risk manager of the level of understanding,
and major differing viewpoints surrounding the
scientific judgments made.
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a) Identify what other reasonable alternatives and
conclusions can be derived from the data set.
b) Discuss how other organizations (e.g., industry
and environmental groups) evaluate the risk and
the pros and cons of their evaluations, compared to
EPA's assessment.
5. Hake clear when:
a) precise conclusions cannot be drawn because of
uncertainty;
b) conclusions may differ because o£ variation (e.g.,
when children exposed to a chemical are at a
different risk from adults exposed to the same
chemical because of their different
susceptibility);
6. Identify major data. gaps and, where appropriate,
indicate whether gathering particular data would add
significantly to the overall certainty of the risk.
a) With. respect to toxicity information, OSW risk
assessors should ensure that any significant
limitations- identified in the. Agency data bases
are presented to the decision makers..
b) If a toxicity- "number* was generated by OSWf
identify which other EPA- offices were involved in
the development and review of the number and what
its limitations are.
7. Indicate where scientific judgments or default
assumptions were used to bridge information gaps, and
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explain thm bases for these judgments/assumptions <
E. Put -fchia Riak Assessment in. Context with
Because of the potential for public misunderstanding through
inappropriate risk cxsaparisons, ."comparative11 risk discussions
(e.g./ the risk of dying in a car accident compared to the risk.
of dying in a plane crash) should not be included as part of the
risk characterization effort. However, risk comparisons can
" • • • * -
provide a valuable tool, to risk managers. Thus, where
appropriate, compare this "risk. assessment with past Agency
decisions, and decisions by other federal and state agencies, or
other countries on the same chemical. If possible:
l. let the risk manager know how the risks posed by this
waste or emission agent compares with the risks posed
by similar wastes or emissions OS* has regulated in the
past;
2. describe how; the strengths and weaknesses of this
assessment .compare with those of previous assessments
used in regulations;
3 . let the risk manager know if other risk assessments
have been performed on the waste or emission and the
results of those' assessments, so the manager can view
this assessment, in its historical context.
P. QthaT*
Indicate any other information which might bear on the
evaluation of risk within the scope, of the assessment. There may
be information that is obvious to the scientist or technical
assessor but not to the risk' manager which would assist in making
a risk-based decision. There may. be a need to put scientific
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arguments used in the assessment into a broader context.
OSW will evaluate the success of its risk assessors and risk
characterizations in this recrard to the extent they:
1. inform the risk, manager whether the key data used for
the assessment is considered experimental, state,of the
art or generally accepted scientific knowledge;
2. include, where appropriate, information which projects
changes in risk under various candidate risk management
alternatives;
3. highlight areas in the assessment which might be
overlooked or misinterpreted by the risk manager; and
4. make it clear that the risk .assessment should be used
tjo inform the risk management decision, not drive it.
Other factors that may be considered in addition to
risk in arriving at the final decision include:
a. Social, (e.g., environmental justice)*
b. Economic
c. Policy
d. Legal
G.
Management oversight of OSW's Risk Characterization Policy
is required to ensure compliance with the policy, to evaluate its
success, and to make necessary improvements. The actions OSW
will take to establish effective mechanisms for implementing,
evaluating and . improving its risk characterization 'guidelines
are:
1. Provide Information to risk assessors about what
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information to present to risk managers.
2. Develop a system, with internal reviewers, independent
from the risk assessor preparing the information, to
ensure that each risk assessment contains a risk
characterization consistent with this policy.
3. Conduct periodic reviews of the risk characterization
portions of the assessments thereafter.
Z. statement of Commitment
Through this Implementation Guidelines document, OSW intends
to ensure that risk characterizations produced by and for the
Office will be substantially consistent with these guidelines and*
with Agency guidance and policy on risk characterization,
recognizing limitations in time and resources* The guidelines
will be updated as. necessary.
Director,.offlee of .•olid Waste Date
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DRAFT-DO NOT COPY. DISTRIBUTE, OR QUOTE.
APPENDIX G
RISK CHARACTERIZATION POLICY BACKGROUND MATERIALS
. for
C-l and C-2 Risk Characterization Colloquia
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RISK CHARACTERIZATION BACKGROUND MATERIALS
EPA ADMINISTRATOR BROWNER'S MARCH 21, 1995
MEMO
POLICY FOR RISK CHARACTERIZATION AT EPA
3UIDANCE FOR RISK CHARACTERIZATION
G-l
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G-2
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j*"!T>*
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. O.C. 20460
THE ADMINISTRATOR
MAR 2 1
SUBJECT: EPA Risk Characterization Pr
TO: Assistant A
Regional Adnanattato
General C
Inspector1
EPA has achieved significant pollution reduction over the past 20 yeers, but the challenges
Many more people ire «wm of
* ----- 1
^
I ji_i|«iu *!»«•• M* *it* flta^ an ri *lh«» IMM! M^««MJ^B«£J^«£M« --- • ^^___^ 1_
lOOBf U1BU. B^ (a* PHI •wCDHTWd OC miiliHK JIMJO 1DB ifBrTriti 01
undmtandmg these issues cootimee to nxrease. We aowwoik with a populace which is not
only interested m knowing wb« EPA diinks about A nartfculsr issue, but also how w« come to
More and more key
aOowtiwmtoii
about the ttgDJtonce
wvm to nocced tod build our
ify,EP\aBmb«
credibility and
of envuiOTiMirtil
-------
.2.
so ttat we msy begin the process of ctagtag to
public, vyj key ftiV^^^Mfin on environmental ride issues. I need your faflp to ensure *h*f these
values are embraced and dot we) change the way we do busmen.
we nut adopt as values transparency in our decttonrnaking process and dariry in
lOtCertlQfl. Wufl fittCD Qtflflf 4100 CH0 OtlOttO rC8Httlfl8 CnVffOCBO60l^» RIUC flUd tflkd
cf environmental risk. This means that we must fully, openly,
and dearly duracterize risks. In dang so. we wffl disclose tbAScieiiiffcamlys^
i ttijy §jpy myfo tfaffllghCTIt thff
risk assessment and risk managenMnt processes. I want to be sure oat key science poEcy issues
are identified as such during the risk assessnKntproc^ that poBcvmiken are fulty aware and
options,
those choices are dearty articulated and visible hi our comnijijicatkios about environmental risk.
Iund«rsta^thatsoinemaybecooceraedabc^a<1fl1ti^ I
expect that we wffl see more diaJlengecp^rtlcularfy at first However, I strongly befieve that
participation, better inabfittidoiilbrdecisic^aiiaaittg, iniproveddefisioot, and more public support
complexities said rhakngeswenice in maleiag decisions iatfaefkce of uncertauity. I view miking
rfi««g|f u esseodil to tfat lo&£tcnn iWftii of this Agcocy.
Clarity in cominunicatkxi also means that we wffl strive to help tf» public put
i!DARZiD^S§^DBDC^u K^SaC Ik^L fBaW BftDaQfla? BflinB90dn^B YI^DB& vVv VF^HBB lUaC flu|^|K|BBQABBK a^sfieilfl^ttM v* w a^DimK
•tgirffc..^
^ *
C* » '
m. ^•
lead to more outside questioning of our assumptions and science poBcka,w« must be more
vigilant about eofuring diat our core assumptk>matti science policies Araiableacrea«prograim,wea grounded m*scienc% ATthin a "zone of
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-3-
White I believe that the American public expects us to err on die side of protection in the face of
sdet^cimcertamry, I c!o not want our assessment We cannot
lead the fight for environment*! protection into the next century ^ghai we use co****"**** **ntf in
all we do.
Thcae con value* of transparency, clarity, consistency, and reasonableness need to guide
eachofusmourday-toKiaywoffcfrxnthefox^
the exposure and risk assessors, to the risk manager, andthnxightotheuhimatedecisionniaker. I
recognize that issuing this niemowifl not by nsetfreiu^ Youneedtobefieveinthe
importance of this change and convey your befieft to vourraana«en arid staff through your words
and actions m older for the change to occur. You also need to play an mtegral role m developing
the implementing policies and procedural far your programs.
I an issuhg the attached EPA Risk Characterization I view
these documents as building blocks fcr the devdopmemc^ your progranwpecificpoacies and
procedure*. The Scit&ctPoBcyCoi^(SPQ plans to adopt the sa^^
implementation as was used for Peer Review. That ia^ttaOiuncflwfflfbnn an Advisory Group
that wiD work with a broad IpptepentitiQii Team made up of representatives from every Piugiau
Office and Region. E^PrQpimOfa^<^'&&n^teutedby to Advisory Group
to develop piugiaui and regton-specoic poBoet and pioceduref for nsk chanctcntation
consistent with the value* of transp*K»cyt darfty, nmtontj, tmd reasoBableaess and
consistent wMi the attached poficy-and guidance.
I recognize tbjtMytjydevdop your Program^ped&
likely to need addrdc«altc<)b to fi^hBpleme« this poBcy, I want you to ideutiry these needed
tools and work cooperatively with tbs Science PoBcyajuncflm their d^vebotaent I want your
draft ptoyain and tegioi>*apeuac poitoiMH prpcouureaj and Bonjflinfiniitloo pdns to be developed
and submitted to the Advisory Group for review by no lit* than May 30,1993. You wuVbe
coTtfictad shorty by thgSPC Steering CuumiiflM to obtain flit names of your ncmoec* to tht
Implementation Te
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G-6
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March 1995
POLICY FOR RISK CHARACTERIZATION
at the U.S. Environmental Protection Agency
INTRODUCTION
Many EPA policy decisions are based in part on the results of risk assessment, an
analysis of scientific information on existing and projected risks to human health
and the environment. As practiced at EPA/ risk assessment makes use of many
different kinds of scientific concepts and data (e.g., exposure, toxkity, epidemiology,
ecology), all of which are used to "characterize!' the expected risk associated with a
particular agent or action in a particular environmental context. Informed use of
reliable scientific information from many different sources is a central feature of the
risk assessment process.
Reliable information may or may not be available for many aspects of a risk
assessment. Scientific uncertainty is a fact of life for the risk assessment process, and
agency managers almost always must mate decisions using assessments that are not
as definitive in all important areas as would be desirable. They therefore need to
understand the strengths and the limitations of each assessment, and to
communicate this information to all participants and the public.
This policy reaffirms the principles and guidance found in the Agency's 1992 policy
(Guidance on Risk Characterization for Risk Managers and Risk Assessors, February
26,1992). That guidance was based on EPA's risk assessment guidelines, which are
products of peer review and public comment. The 1994 National Research Council
(NRC) report, "Science and Judgment in Risk Assessment," addressed the Agency's
approach to risk assessment, including the 1992 risk characterization policy. The
NRC statement accompanying the report stated,"... EPA's overall approach to
assessing risks is .iindamentally sound despite often-heard criticisms, but the
Agency must more clearly establish the scientific and policy basis for risk estimates
and better describe me uncertainties in its estimates of risk."
This policy statement and associated guidance for risk characterization is designed to
ensure mat critical information from each stage of a risk assessment is used in
forming conclusions about risk and that this information is communicated from
risk assessors to risk managers (policy makers), from middle to upper management,
and from the Agency to the public. Additionally, the policy will provide a br .:* for
greater clarity, transparency^ reasonableness, and consistency in risk assessments .
across Agency programs. While most of the discussion and examples in this policy
are drawn from health risk assessment, these values also apply to ecological risk
assessment. A parallel effort by the Risk Assessment Forum to develop EPA
ecological risk assessment guidelines will include guidance specific to ecological risk
characterization.
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Statement
Each risk assessment prepared in support of decision-making at EPA should
include a risk characterization that follows the principles and reflects the values
outlined in this policy. A risk characterization should be prepared in a manner that
is clear, transparent, reasonable and consistent with other risk characterizations of
similar scope prepared across programs .in the Agency. F «rther, discussion of risk in
all EPA reports, presentations, decision packages, and other document should be
substantively consistent with the risk characterization. The nature of the risk
characterization will depend upon the information available, the regulatory
application of the risk information, and the resources (including time) available. In
all. cases, however, the assessment should identify and discuss all the major issues
associated with determining the nature and extent of the risk and provide
commentary on any constraints limiting fuller exposition.
Aspects of Risk Characterization
Bridging risk assessment and risk management As the interface between risk
assessment and risk management, risk characterizations should be clearly presented,
and separate from any risk management considerations. Risk management options
should be developed using die risk characterization and should be based on
consideration of all relevant factors, scientific and nonsdentific.
' Discussing confidence and uncertainties. Key scientific concepts, data and
methods (e.g., use of animal or human data for extrapolating from high to low
doses, use of pharrnacokinetics data, exposure pathways, sampling methods,
availability of chemical-specific information, quality of data) should be discussed:
To ensure transparency, risk characterizations should include a statement of
confidence in the assessment that identifies all ma/or uncertainties along with
comment on their influence on the assessment, consistent with the Guidance on
Risk Characterization (attached).
Presenting several types of risk information. Information should be
presented on the range of exposures derived from exposure scenarios and on the use
of multiple risk descriptors (e.g., central tendency, high end of individual risk,
population risk, important subgroups, if known) consistent with terminology in the
Guidance on Risk Characterization, Agency risk assessment guidelines, and
program-specific guidance. In decision-making, risk managers should use risk
Information appropriate to their program legislation.
EPA conducts many types of risk assessments, including screening-level
assessments of new chemicals, in-depth assessments of pollutants such as dioxin
G-8
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and environmental tobacco smoke, and site-specihc assessments for hazardous
waste sites. An iterative approach to risk assessment, beginning with screening
techniques, may be used to determine if a more comprehensive assessment is
necessary. The degree to which confidence and uncertainty are addressed in a risk
characterization depends largely on the scope of the assessment. In general, the
scope of the risk characterization should reflect the information presented in the
risk assessment and program-specific guidance. When special circumstances (e.g.,
lack of data, extremely complex situations, resource limitations," statutory deadlines)
preclude a full assessment, such circumstances Should be explained and their impact
on the risk assessment discussed.
Risk Characterization in Context
Risk assessment is based on a series of questions that the assessor asks about
scientific information that is relevant to human and/or environmental risk. Each
question calls for analysis and interpretation of the available studies/ selection of the
concepts and data that are most scientifically reliable and most relevant to the
problem at hand, and scientific conclusions regarding the question presented. For
example, health risk assessments involve the following questions:
Hazard Identification — What is known about the capacity of an environmental
agent for causing cancer or other adverse health effects in humans, laboratory
animals, or wildlife species? What are the related uncertainties and science
policy choices?
Dose-Response Assessment — What is known about the biological mechanisms
and dose-response relationships underlying any effects observed in the laboratory
or epidemiology studies providing data for the assessment? What are the
related uncertainties and science policy choices?
Exposure Assessment - What is known about the principal paths, patterns, and
magnitudes of human or wildlife exposure and numbers of persons or wildlife
species likely to be exposed? What axe the related uncertainties and science
policy choices?
Corresponding principles and questions for ecological risk assessment are being
discussed as part of the effort to develop ecological risk guidelines.
Risk characterization is the summarizing step of risk assessment. The risk
characterization integrates information from the. preceding components of the risk
assessment and synthesizes an overall conclusion about risk that is complete,
informative and useful for decisionmakers.
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Risk characterizations should clearly highlight both the. confidence and the
uncertainty associated with the risk assessment For example, numerical risk
estimates should always be accompanied by descriptive information carefully
selected to ensure an objective .and balanced characterization of risk in risk
assessment reports and regulatory documents. In essence, a risk characterization
conveys the assessor's judgment as to the nature and existence of (or lack of) human
health or ecological risks. Even though, a risk characterization describes limitations
in an assessment, a balanced discussion of reasonable conclusions and related
uncertainties enhances, rather than detracts, from the overall credibility of each
assessment.
"Risk characterization" is not synonymous with "risk communication." This
risk characterization policy addresses the interface between risk assessment and risk
management Risk communication, in contrast, emphasizes the process of
exchanging information and opinion with the public - including individuals,
groups, and other institutions. The development of a risk assessment may involve
risk communication. For example, in the case of site-specific assessments for
hazardous waste sites, discussions with the pubik may influence the exposure
pathways included in the risk assessment. While the final risk assessment
document (including the risk characterization) is available to the public, the risk
communication process may be better served by separate risk information
documents designed for particular audiences.
Promoting Clarity. Comparability and Consistency
There are several reasons that the Agency should strive for greater clarity,
consistency and comparability in risk assessments. One reason is to minimize
confusion.* For example, many people have not understood that a risk estimate of
one in a million for an "average" individual is not comparable to another one in a
million risk estimate for the "most exposed individual." Use of such apparently
similar estimates without further explanation leads to misunderstandings about the
relative significance of risks and the protectiveness of risk reduction actions.
EPA's Exposure-Assessment Guidelines provide standard descriptors of
exposure and risk. Use of these terms in all Agency risk assessments will promote
consistency and comparability. Use of several descriptors, rather than a single
descriptor, will enable EPA to present a fuller picture of risk that corresponds, to the
range of different exposure conditions encountered by various individuals and
populations exposed to most environmental chemicals.
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Legal Effect
This policy statement and associated guidance on risk characterization do not
establish or affect legal rights or obligations Rather, they confirm the importance of
risk characterization as a component of risk assessment, outline relevant principles,
and identify factors Agency staff should consider in implementing the policy.
The policy and associated guidance do not stand alone; nor do they establish a
binding norm that is finally determinative of the issues addressed. Except where
otherwise provided by law, the Agency's decision on conducting a risk assessment in
any particular case is within the Agency's discretion. Variations in the application
of the policy and associated guidance, therefore, are not a legitimate basis for.
delaying or complicating action on Agency decisions.
Applicability
Except where otherwise provided by law and subject to the limitations on the
policy's legal effect discussed above, this policy applies to risk assessments prepared
by EPA and to risk assessments prepared by others, that are used in support of EPA
decisions.
EPA will consider the principles in this policy in evaluating assessments
submitted to EPA to complement or challenge Agency assessments. Adherence to
this Agency-wide policy will improve understanding of Agency rirk assessments,
lead to more informed decisions, and heighten the credibility of both assessments
and decisions.
Im pi ementation
Assistant Administrators and Regional Administrators are responsible for
implementation of this policy within their organizational units. The Science Policy
Council (SPC) is organizing Agency-wide implementation activities. Its
responsibilities include promoting consistent interpretation, assessing Agency-wide
progress, working with external groups on risk characterization issues and methods,
and developing recommendations for revisions of the policy and guidance, as
necessary.
Each Program and Regional office will develop office-specific policies and
procedures for risk characterization that are consistent with this policy and the
associated guidance. Each Program and Regional office-will designate a risk
manager or risk assessor as the office representative to the Agency-wide Implementa-
G-li
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tion Team, which will coordinate development of office-specific policies and
procedures and other implementation activities. TThe SPC will also designate a
small cross-Agency Advisory Group that will serve as the liaison between the SPC
and the Implementation Team.
In ensuring coordination and consistency among EPA offices, the
Implementation Team will take* into account statutory and court deadlines, resource
implications, and existing Agency and program-specific guidance on risk
assessment The group will work closely with staff throuj^iout Headquarters and
Regional offices to promote development of risk characterizations that present a full
and complete picture of risk that meets the needs of the risk managers.
//S3s+jf*&/n * MAR2.119S5
APPROVED: fL&*Cfr<^ 6fSt\(J*sA***»~*^—* DATE"
Carol M. Brownlr, Administrator
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GUIDANCE
FOR
RISK CHARACTERIZATION
U.S. Environmental Protection Agency
Science Policy Council
February, 1995
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CONTENTS
I. The Risk Assessment-Risk Management Interface
II. Risk .Assessment and Risk Characterization
III. Exposure and Risk Descriptors
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PREFACE
This guidance contains principles for developing and describing EPA risk
assessments, with a particular emphasis on risk characterization. The current
document is an update of the guidance issued with the Agency's 1992 policy
(Guidance on Risk Characterization for Risk Managers ar.d Risk Assessors, February
26,1992). The guidance has not been substantially revised, but includes some
clarifications and changes to give more prominence to certain issues, such as the
need to explain the use of default assumptions.
As in the 1992 policy, some aspects of this guidance focus on cancer risk
assessment, but the guidance applies generally to human health effects (e.g.,
rieurotoxicity, developmental toxicity) and, with appropriate modifications, should
be used in all health risk assessments. This document has not been revised to
specifically' address ecological risk assessment, however, initial guidance for
ecological risk characterization is included in EPA's Framework for Ecological Risk
Assessments (EPA/630/R-92/001). Neither does this guidancb address in detail the
use of risk assessment information (e.g., information from the Integrated Risk
Information System (IRIS)) to generate site or media-specific risk assessments.
Additional program-specific guidance will be developed to enable implementation
of EPA's Risk Characterization Policy. Development of such guidance will be
overseen by the Science Policy Council and will involve risk assessors and risk
managers from across the Agency.
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L THE RISK ASSESSMENT-RISK MANAGEMENT INTERFACE
Recognizing that for many people the term risk assessment has wide meaning, the
National Research Council's 1983 report on risk assessment in the federal
government distinguished between risk assessment and risk management.
"Broader uses of the term [risk assessment] than ours also embrace analysis of
perceived risks/ comparisons of risks associated with different regulatory
strategies, and occasionally analysis of the economic and social implications of
regulatory decisions— functions that we assign to risk management
(emphasis added). (1)
In 1984, EPA endorsed these distinctions between risk assessment and risk
management for Agency use (2), and later relied on them in developing risk
assessment guidelines (3). In 1994, the NRC reviewed the Agency's approach to and
use of risk assessment and.issued an extensive report on their findings (4). This
distinction suggests that EPA participants in the process can be grouped into two
main categories, each with somewhat different responsibilities, based on their roles
with respect to risk assessment and risk mr.nag2ment.
A. Roles of Risk Assessors and Risk Managers
Within the Risk Assessment category there is a group that develops chemical-
specific riskfcjsessments by collecting, analyzing, and synthesizing scientific data to
produce the hazard identification, dose-response, and exposure assessment portion
of the risk assessment and to characterize risk. This group relies in part on Agency
risk assessment guidelines to address science policy issues and scientific
uncertainties. Generally, this group includes scientists and statisticians in the Office
of Research and Development; the Office of Prevention, Pesticides and Toxics and
other program offices; the Carcinogen Risk Assessment Verification Endeavor
(CRAVE); and the Reference Dose (RfD) and Reference Concentration (RfC)
Workgroups.
Another group generates site- or media-specific risk assessments for use in
regulation development or site-specific decision-making. These assessors rely on
existing databases (e.g., IRIS, ORD Health Assessment Documents, CRAVE and
RfD/RfC Workgroup documents, and program-specific toxiciry information) and
media- or site-specific exposure information in developing risk assessments. This
group also relies in part on Agency risk assessment guidelines and program-specific
guidance to address science policy issues and scientific uncertainties. Generally, this
group includes scientists and analysts in program offices, regional offices, and the
Office of Research and Development.
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Risk managers, as a separate category, integrate the risk characterization with other
considerations specified in applicable statutes to make'and justify regulatory
decisions. Generally, this group includes Agency managers and decision-makers.
Risk managers also play a role in determining the scope of risk assessments. The
risk assessment process involves regular interaction between risk assessors and risk
managers, with overlapping responsibilities at various stages in the overall process.
Shared responsibilities include initial decisions regarding the planning and conduct
of an assessment, discussions as the assessment develops, decisions regarding new
data needed to complete an assessment and to address significant uncertainties. At
critical junctures in the assessment such consultations shape the nature of, and
schedule for, the assessment. External experts and members of the public may also
play a role in determining the scope of the assessment; for example, the public is
often concerned about certain chemicals or exposure pathways in the development
of site-specific risk assessments.
B. Quiding Principles
The following guidance outlines principles for tL-pe who generate, review, u^e, and
integrate risk assessments for decision-making.
1. Risk assessors and risk managers should be sensitive to distinctions between
risk assessment and risk management.
The major participants in the risk assessment process have many shared
responsibilities. Where responsibilities differ, it is important that participants
confine themselves to tasks in their areas of responsibility and not inadvertently
obscure differences between risk assessment and risk management.
For the generators of the assessment, distinguishing between risk assessment and
risk management means that scientific information is selected, evaluated, and
presented without considering issues such as cost feasibility, or how the scientific
analysis might influence the regulatory or site-specific decision. Assessors are
charged with (1) generating a credible, objective, realistic, and scientifically balanced
analysis; (2) presenting information on hazard, dose-response, exposure and risk;
and (3) explaining confidence in each assessment by clearly delineating strengths,
uncertainties and assumptions, along with the impacts of these factors (e.g.,
confidence limits, use of conservative/non-conservative assumptions) on the
overall assessment They do not make decisions on the acceptability of any risk
level for protecting public health or selecting procedures for reducing risks.
For users of tfrg pssfssjnent ahtf for decision-makers who integrate these
assessments into regulatory or site-specific decisions, the distinction between risk
assessment and risk management means refraining from influencing the risk
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description through consideration of other factors — e.g., the regulatory outcome -
and from attempting to shape the risk assessment to avoid statutory constraints,
meet regulatory objectives, or serve political purposes. Such management
considerations are often legitimate considerations for the overall regulatory decision
(see next principle), but they have no rcie in estimating or describing risk.
However, decision-makers and risk assessors participate in an Agency process that
establishes* policy directions that determine the overall nature and tone of Agency
risk assessments and, as appropriate, provide policy guidance on difficult and
controversial risk assessment issues. Matters such as risk assessment priorities,
degree of conservatism, and acceptability of particular risk levels are reserved for
decision-makers who are charged with making decisions regarding protection of
public health.
2. The risk assessment product, that is, the risk characterization, is only one of
several kinds of. information used for regulatory decision-making.
Risk characterization, the last step in risk assessment, is the starting point for risk
management considerations and the foundation for regulatory decision-making, but
it is only one of several important components in such decisions. As the last step in
risk assessment, the risk characterization identifies and highlights the noteworthy
risk conclusions and related uncertainties. Each of the environmental laws
administered by EPA calls for consideration of other factors at various stages in the
regulatory process. As authorized by differ nt statutes, decision-makers evaluate
technical feasibility (e.g., treatability, detection limits), economic, social, political, and
legal factors as part .of the analysis of whether or not to regulate and, if so, to what
extent. Thus, regulatory decisions are usually based on a combination of the
technical analysis used to develop the risk assessment and information from other
fields.
For this reason, risk assessors and managers should understand that the regulatory
decision is usually not determined solely by the outcome of the risk assessment. For
example, a regulatory decision on the use of a particular pesticide considers not only
the risk level to affected populations, but also the agricultural benefits of its use that
may be important for the nation's food supply. Similarly, assessment efforts may
produce an RfD for a particular chemical, but other considerations may result in a
regulatory level that is.more or less protective than.the RfD itself.
For decision-makers/ this means that societal considerations (e.g., costs and benefits)
mat, along with the risk assessment shape the regulatory decision should be
described as fully as the scientific information set form in the risk characterization.
Information on data sources and analyses, their strengths and limitations,
confidence in the assessment, uncertainties, and alternative analyses are as
important here as they are for the scientific components of the regulatory decision.
Decision-makers should be able to expect, for example, the same level of rigor from
the economic analysis as they receive from the risk analysis. Risk management
decisions involve numerous assumptions and uncertainties regarding technology,
economics and social factors, which need to be explicitly identified for the
decision-makers and the public.
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RISK CHARACTERIZATION
A. Defining Risk Characterization in the Context of Risk Assessment
EPA risk assessment principles and practices draw on many sources. Obvious
sources include the environmental laws administered by EPA, the National
Research Council's 1983 report on risk assessment (1), the Agency's Risk Assessment
Guidelines (3), and various program specific guidance (e.g., the Risk Assessment
Guidance for Superfund). Twenty years of EPA experience in developing,
defending, and enforcing risk assessment-based regulation is another. Together
these various sources stress the importance of a clear, explanation of Agency
processes for evaluating hazard, dose-response, exposure, and other data that
provide the scientific foundation for characterizing risk.
This section focuses on two requirements for full characterization of risk. First, the
characterization should address qualitative and quantitative features of the
assessment. Second, it should identify the important strengths and uncertainties in
the assessment as part of a discussion of .the confidence in the assessment. This
emphasis on a full description of all elements of the assessment draws attention to
the importance of the qualitative, as well as the quantitative, dimensions of the
assessment. The 1983 NRC report carefully distinguished qualitative risk
assessment from quantitative assessments, preferring risk statements that are not
strictly numerical.
The term risk assessment-is often given narrower and broader meanings
than we have adopted here. For some observers, the term is synonymous
with quantitative risk assessment and emphasizes reliance on numerical
results. Our broader definition includes quantification, but also includes
qualitative expressions of risk. Quantitative estimates of risk are not always
feasible, and they may be eschewed by agencies for policy reasons. (1)
EPA's Exposure Assessment Guidelines define risk characterization as the final step
in the risk assessment process that:
• Integrates the individual characterizations from the hazard identification, dose-
response, and exposure assessments;
• Provides an evaluation of the overall quality of the assessment and the degree
of confidence the authors have in the estimates of risk and conclusions drawn;
• Describes risks to individuals and populations in terms of extent and severity of
probable harm; arid
• Communicates results of the risk assessment to the risk manager. (5)
Particularly critical to full characterization of risk is a frank and open discussion of
the uncertainty in the overall assessment and in each of its components. The
uncertainty discussion is important for several reasons.
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1. Information from different sources, carries different kinds of uncertainty and
knowledge of these differences is important when uncertainties are combined
for characterizing risk.
2. Tae risk assessment process, with management input, involves decisions
regarding the collection of additional data (versus living with uncertainty); in
the risk characterization, a discussion of the uncertainties will help to identify
where additional information could contribute significantly to reducing
uncertainties in risk assessment.
3. A clear and. explicit statement of the strengths and limitations of a risk
assessment requires a clear and explicit statement of related uncertainties.
A discussion of uncertainty requires comment on such issues as the quality and
quantity of available data, gaps in the data base for specific chemicals, quality of the
.measured data, use of default assumptions, incomplete understanding of general
biological phenomena, and scientific judgments or science policy positions that were
employed to bridge information gaps.
In short, broad agreement exists on the importance ot a full picture of risk,
particularly including a statement of confidence in the assessment and the
a.:ncta*ed uncertainties. This section disc- •-»$ information content and uncertainty
aspects of risk characterization, while Section HI discusses various descriptors used
in risk characterization.
8. Guiding Principles
1. The risk characterization integrates the information from the hazard
identification, dose-response, and exposure assessments, using a combination of
qualitative information, quantitative information, and information regarding
uncertainties.
Risk assessment is based on a series of questions that the assessor asks about the data
and the implications of the data for human risk. Each question calls for analysis and
interpretation of the available studies, selection of the data that are most
scientifically reliable and most relevant to the problem at hand, and scientific
conclusions regarding the question presented. As suggested below, because the
questions and analyses are complex, a complete characterization includes several
different kinds of information, carefully selected for reliability and relevance.
a. Hazard Identification — What is known about the capacity of an environmental
agent for causing cancer (or other adverse effects) in humans and laboratory
animals?
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Hazard identification is a qualitative description based on factors such as the kind
and quality of data on humans or laboratory animals, the availability of ancillary
information (e.g., structure-activity analysis, genetic toxicity, pharmacokinetics)
from other studies, and the weight-of-the-evidence from all of these data sources.
For example, to develop this description, the issues addressed include:
1) the nature, reliability, and consistency of, the particular studies in humans and
in laboratory animals;
2) the available information on the mechanistic basis for activity; and
3) experimental animal responses and their relevance to human outcomes.
These issues make clear that the task of hazard identification is characterized by
describing the full range of available information and the implications of that
information for human health.
b. Dose-Response Assessment ~ What is known about the biological mechanisms
and dose-response relationships underlying any effects observed in the
laboratory or epidemiology studies providing data for the assessment?
The dose-rrsponse assessment examines qvnti*ative relationships between
exposure (or dose) and effects in the studies used to identify and define effects of
concern. This information is later used-along with "real world" exposure
information (see below) to develop, estimates of the likelihood of adverse effects in
populations potentially at risk. It should be noted that, in practice, hazard
identification for developmental toxicity and other non-cancer health effects is
usually done ir conjunction with an evaluation of dose-response relationships,
since the determination of whether there is a hazard is often dependent on whether
a dose response relationship is present (6) Also, the framework developed by EPA
for ecological risk assessment does not distinguish between hazard identification
and dose-response assessment, but rather calls for a "characterization of ecological
effects." (7)
Methods for establishing dose-response relationships often depend on various
assumptions used in lieu of a-complete data base, and the method chosen can
strongly influence the overall assessment The Agency's risk assessment guidelines
often identify so-called "default assumptions" for use in the absence of other
information. The risk assessment should pay careful attention to the choice of a
high-to-low dose extrapolation procedure. As a result, an assessor who is
characterizing a dose-response relationship considers several key issues:
1) the relationship between extrapolation models selected and available
information on biological mechanisms;
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2) how appropriate data sets were selected from those that show the range of
possible potencies both in laboratory animals and humans;
3) the basis for selecting interspecies dose scaling factors to account for scaling
doses from experimental animals to humans;
4) the correspondence between the expected route(s) of exposure and the exposure
route(s) utilized in the studies forming the basis of the dose-response
assessment as well as the interrelationships of potential effects from different
exposure routes;
5) the correspondence between the expected duration of exposure and the
exposure durations in the studies used in forming the basis of the dose-response
assessment, e.g., chronic studies would be used to assess long-term, cumulative
exposure concentrations, while acute studies would be used in assessing peak
levels of exposure; and
6) the potential for differing susceptibilities among population subgroups.
The Agency's Integrated Risk Information System (IRIS) is a repository for such
information, for EPA. EPA program offices also maintain program-specific
databases, ruch as the QSWER Health Effec' -.Assessment Summary Tables (HEA5T).
IRIS includes data summaries, representing Agency consensus on specific chemicals,
based on a careful review of the scientific issues listed above. For specific risk
assessments based on data from any source, risk assessors should carefully review
the information presented, emphasizing confidence in the data and uncertainties
(see subsection 2 below). Specifically, when IRIS data are used, the JUS statement of
confidence should be included as an explicit part of the risk characterization for
hazard and dose-response information.
c Exposure Asstssmtnt — What is known about the principal paths, patterns, and
magnitudes of human exposure and numbers of persons who may be exposed?
The exposure assessment examines a wide range of exposure parameters pertaining
to the environmental scenarios of people who may be exposed to the agent under
study. The information considered for the exposure assessment includes
monitoring studies of chemical concentrations in environmental media, food, and
other materials; modeling of environmental fate and transport of contaminants;
and information on different activity patterns of different population subgroups.
An assessor who characterizes exposure should address several issues:
1) The basis for the values and input parameters used for each exposure scenario.
If the values are based on data, there should be a discussion of the quality,
purpose, and representativeness of the database. For monitoring data, there
should be a discussion of the data quality objectives as they are relevant to risk
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assessment, including the appropriateness of the analytical detection limits. If
models are applied, the appropriateness of the models and information on their
validation should be presented. When assumptions are made, the source and
general logic used to develop the assumptions (e.g., program guidance, analogy,
professional judgment) should be described.
2) The confidence in the assumptions made about human behavior and the
relative .likelihood'of the different exposure scenarios.
3) The major factor or factors (e.g., concentration, body uptake, duration/frequency
of exposure) thought to account for the greatest uncertainty in the exposure
estimate, due either to sensitivity or lack of data.
4) The link between the exposure information and the risk descriptors discussed
in Section HI of this Appendix. Specifically, the risk assessor needs to discuss
the connection between the conservatism or non-conservatism of the
data/assumptions used in the scenarios and the choice of descriptors.
5) Other information that may be important for the particular risk assessment
For example, for many assessments, other sources and background levels in the
environment may contribute significantly to population exposures and should
be discussed.
2) The risk characterization includes a discussion of uncertainty and variability.
In the risk characterization, conclusions about hazard and dose response are
integrated with those from the exposure assessment. In addition, confidence about
these conclusions, including information about the uncertainties associated with
each aspect of the assessment in the final risk summary, is highlighted. In the
previous assessment steps and in the risk characterization, the risk assessor must
distinguish between variability and uncertainty.
Variability arises fr m true heterogeneity in characteristics such as dose-response
differences within a population, or differences in contaminant levels in the
environment. The values of some variables used in an assessment change with
time and space, or across the population whose exposure is being estimated.
Assessments should address the resulting variability in doses, received by members
of the target population. Individual exposure, dose, and risk can vary widely in a
large population. The central tendency and high end individual risk descriptors
(discussed in Section in below) are intended to capture the variability in exposure,
lifestyles, and other factors that lead to a distribution of risk across a population.
Uncertainty, on the other hand, represents lack of knowledge about factors such as
adverse effects or contaminant levels which may be reduced with additional study.
Generally, risk assessments carry several'categories ot uncertainty, and each merits
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consideration. Measurement uncertainty refers to the usual error that accompanies
scientific measurements-standard statistical techniques can often be used to express
measurement uncertainty. A substantial amount of uncertainty is often inherent in
envircnmental sampling, and assessments should address these uncertainties.
There are likewise uncertainties associated with the use of scientific models, e.g.,
dose-response models, models of environmental fate and transport. Evaluation of
model uncertainty would consider the scientific basis for the model and available
empirical validation.
A different kind of uncertainty stems from data gaps — that is, estimctes or
assumptions used in the assessment. Often, the data gap is broad, such as the
absence of information on the effects of exposure to a chemical on humans or on
the biological mechanism of action of an agent. The risk assessor should include a
statement of confidence that reflects the degree to which the risk assessor believes
that the estimates or assumptions adequately fill the data gap. For some common
and important data gaps, Agency or program-specific risk assessment guidance
provides default assumptions or values. Risk assessors should carefully consider all
available data before deciding to rely on default assumptions. If defaults are used,
the risk assessment should reference the Agency guidance that explains the default
assumptions or values.
Often risk assessors and managers simplify, discussion of risk issues by speaking only
of the numerical components of an assessment. That if, they refer to the alpha-
numeric weight-of-the-evidence classification, unit risk, the risk-specific dose or the
qi* for cancer risk, and the RfD/RfC for health effects other than cancer, to the
exclusion of other information bearing on the risk case. However, since every
assessment carries uncertainties, a simplified numerical presentation of risk is
always incomplete and often misleading, for tills reason, the NRC (1) and EPA risk
assessment guidelines (2) call for "characterizing" risk to include qualitative
information, a related numerical risk estimate and a discussion Of uncertainties,
limitations, and assumptions-default and otherwise.
Qualitative information on methodology, alternative interpretations, and working
assumptions (including defaults) is an important component of risk
characterization. For example, specifying that animal studies rather than human
studies were used in an assessment tells others that the risk estimate is based on
assumptions about human response to a particular chemical rather than human
data. Information that human exposure estimates are based on the subjects'
presence in the vicinity of a chemical accident rather than tissue measurements
defines known and unknown aspects of the exposure component of the study.
Qualitative descriptions of fius kind provide crucial information that augments
understanding of numerical risk estimates. Uncertainties such as these axe expected
in scientific studies and in any risk assessment based on these studies. Such
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uncertainties do not reduce the validity of the assessment. Rather> they should be
highlighted along with other important xisk assessment conclusions to inform
others fully on the results of the assessment.
In many cases, assessors must choose among available data, models, or assumptions
in estimating risks. Examining the impact of selected, plausible alternatives on the
conclusions of the assessment is an important .part of the uncertainty discussion.
The key words are "selected" and "plausible;" listing all alternatives to a particular
assumption, regardless of their merits would be superfluous. Generators of the
assessment, using best professional judgment, should outline the strengths and
weaknesses of the plausible alternative approaches.!
An adequate description of the process of alternatives selection involves several
aspects.
a. A rationale for the choice.
b. Discussion of the effects of alternatives selected on the assessment.
c. Comparison with other plausible alternatives, where appropriate.
The degree to which variability and uncertainty are addressed depends largely on
the scope of the assessment and the resources available. For example, the Agency
does not expect an assessment to evaluate »nd assess every conceivable exposure
scenario for every possible pollutant, to examine all susceptible populations
potentially at risk, or to characterize every possible environmental scenario to
estimate the cause and effect relationships between exposure to pollutants and
adverse health effects. Rather, the discussion of .uncertainty and variability should
reflect the type and complexity of the-risk assessment, with the level of effort for
analysis and discussion of uncertainty corresponding to the level of effort for the
assessment.
3. Well-balanced risk characterizations present risk conclusions and information
regarding the strengths and limitations of the assessment for other risk
assessors, EPA decision-makers, and the public
The risk assessment process calls for identifying and highlighting significant risk
conclusions and related uncertainties partly to assure full communication among
risk assessors and partly to assure that decision-makers are fully informed. Issues
are identified by acknowledging noteworthy qualitative and quantitative factors that
make a difference in the overall assessment of hazard and risk, and hence in the
ultimate regulatory decision. The key word is "noteworthy." Information that
tin cases where risk assessments within an Agency program routinely address similar sets of
alternatives, program guidance may be developed to streamline and'simplify the discussion of these
alternatives.
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significantly influences the analysis.is, explicitly noted — in all future-presentations
of the risk assessment and in the related decision. Uncertainties and assumptions
that strongly influence confidence in the risk estimate also require special attention.
Numerical estimates should not be separated from the descriptive information that
is integral to risk characterization. Documents and presentations supporting
regulatory or site-specific decisions should include both the numerical estimate and
descriptive information; in short reports, this information can be abbreviated. Fully
visible information assures that important features of the assessment are
immediately available at each, level of review for evaluating whether risks are
arcep table or unreasonable.
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EL EXPOSURE ASSESSMENT AND RISK DESCRIPTORS
A. Presentation of Itisk Descriptors
The results of a risk assessment are usually communicated to the risk manager in
the risk characterization portion of the assessment This communication is often
accomplished through risk descriptors which convey information and answer
questions about risk, each descriptor providing different information and insights.
Exposure assessment plays a key role in developing these risk descriptors since each
descriptor is based in part on the exposure distribution within the population of
interest.
The following guidance outlines the different descriptors in a convenient order that
should not be construed as a hierarchy of importance. These descriptors should be
used to describe risk in* a variety of ways for a given assessment consistent with the
assessment's purpose, the data available, and the information the risk manager
needs. Useof a rangeof d^scriptorsmste^of a sirtgledes<3iptor enables Agency
programs to present a pictured risk tturtcorrespciruia to tte .
exposure conditions encountered for most environmental chemicals. This analysis,
in turn, allows risk managers to identify populations at greater and lesser risk and to
shape regulatory solutions accordingly.
Agency risk assessments win be .expected to address or provide descriptions of (1)
individual risk mat include the central tendency and high end portions of the risk
distribution, (2) population risk; end (3) important subgroups of the population,
such as highly exposed or highly susceptible groups. Assessors may also use
additional descriptors of risk as needed when these add to the clarity of the
presentation. With the exception of iimnrtents where particular descriptors clearly
do not apply, some form of these three types of desciiplois should be routinely
developed and presented for Agency risk assessments*. In other cases, where a
descriptor would be relevant, but me program lacks the data or method* to develop
it, the program office should design and implement« plan/ in coordination with
other EPA offices/ to meet these assessment needs. Whue gaps continue to exist,
risk assessors should maJfe their best efforts to address each risk descriptor, and at a .
minimum, should briefly discuss tilt lack of data or metttaJU. Finally, presenters of
risk assessment information should be prepared to routinely answer questions by
risk managers concerning these descriptors.
It is essential that presenters not only communicate the results of the assessment by
addressing each of the descriptorswhere appropriate, but that they also
ZProgram-specific guidance will need to addicts these situations. For example, for site-specific
assessments, the utility and appropriateness of population risk estimates will be determined based on
the available data and program guidance.
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communicate their confidence that these results portray a reasonable picture of the
actual or projected exposures. This task will usually be accomplished by frankly
commenting on the key assumptions and parameters that have the greatest impact
on the results, the basis or rationale for choosing these assumptions/parameters,
and the consequences of choosing other assumptions.
B. Relationship Between Exposure Descriptors and Risk Descriptors
In me risk assessment .process, risk is. estimated as a function of exposure, with the
risk of adverse affects increasing as exposure increases. Information on the levels of
exposure experienced by different members of the population is key to
understanding the range of risks that may occur.. Risk assessors and risk managers
should keep in mind, however, that exposure is not synonymous with risk.
Differences among individuals in absorption rates, susceptibility, or other factors
mean that individuals with the same level of exposure may be at different levels of
risk. In most cases, the state of the science is not yet adequate to define distributions
of factors such as population susceptibility. Ihe guidance principles below discuss a
variety of risk descriptors that primarily reflect differences fo estimated exposure. If
a full description of the range of susceptibility in the population cannot be
presented, an effort should be made to identify subgroups that for various reasons,
may be particularly susceptible.
C Guiding Principle*
1. InfeMMrion about tha diatrftmthm nt hidfyldaal •MMMUUM i« Important in
communicating the results of a risk assessment*
Hie risk manager is generally interested in answers to questions such as me
following:
• Who are the people at the highest risk?
• What risk levels are they subjected to?
• What are they doing, when do they live, etc., that might be putting mem at this
higher risk?
• What is the average risk for individuals in the population of interest?
Individual exposure and risk descriptors are intended to provide answers, to these
questions so as to illuminate the risk management decisions mat need to be made.
In order to describe the range of risks, both high end and central tendency
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descriptors are used to convey the variability in risk levels experienced by different
individuals in the population.
a. High end descriptor
For the Agency's purposes, high end risk descriptors are plausible estimates of the
individual risk for those persons at the upper end of the risk distribution. Given"
limitations in current understanding of variability in individuals' sensitivity to
toxins, high end descriptors will usually address high end exposure or dose (herein
referred to as exposure for brevity). The intent of these descriptors is to convey
estimates of exposure in the upper range of the distribution, but to avoid estimates
which are beyond the true distribution. Conceptually, high end exposure means
exposure above about the 90th percentue of the population distribution, but not
higher than the individual in the population who has the highest exposure. When
large populations are assessed, a large number of individuals may be included
within the "high end" (e.g., above 90th or 95th percentik) and information on the
range of exposures received by these individuals should be presented.
High end descriptors are intended to estimate the exposures that are expected to
occur in small, but definable, "high end" segments of the subject population.^ The
individuals with these exposures may be members of a special population segment -
or individuals in the general population who are highly exposed because of the
inherent stochastic nature of me factors which give rise to exposure. Where
differences in sensitivity SUL be identified within the population, high end estimates
addressing sensitive individuals or subgroups can be developed.
In those few cases in which me complete data on the population distributions of
exposures and doses are available, high end exposure or dose estimates can be
represented by reporting exposuresor doses at a set of selected percentiks of the
distributions, such as th«9<^ 95th, and 98th oeroentile. High end exposures or
doses, as appropriate/ can men be used to calculate high end risk estimates.
In the majority of cases when the complete distributions are not available, several
methods help estimate a high end exposure or dose, It sufficient information about
the variability in chemical concentx :tiona, activity patterns, or other factors are
available, the distribution may be estimated through the use of appropriate.
modeling (e.g., Monte Carlo smvilation or parametric statistical methods). The
3Hfficnd«tfaui«»focuton«rtiMtMofecpo«uMfat^ Bounding
estimate*, on the other hind, an comtructatd to bt equal to or greate than trtthighttt actual risk in
the pofnilatkMortrtthighrt risk trutt could be expect AVrotstcmioeiuio"
refm to a combiruticnclcvato and condition
conceivable risk. Although it is poM&fe that such an'exposurc, doM, or aeradttviry cosztbixuktian might
occur in a given population of interest, th» probability of an ixi^Uvidualrecdvingthit combination ol
pa i« ii«n»Hy «m>n ^p^ ftftjn *O gflili that TUth-a CTmbiMttPn vffll HO* nft^rr hi »
particular, actual population.
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determination of whether available information is sufficient to support the use of
probabilistic estimation methods requires careful review and documentation by the
risk assessor. If the input distributions are based on limited data, the resulting
distribution should be evaluated carefully to determine whether it is an
improvement over more traditional estimation techniques. If a distribution is
developed, it should be described with a series of percentiles or population
frequency estimates, particularly In the high end range. The assessor and risk *
manager should be aware, however/ mat unless a great deal is known about
exposures and doses at the high end of the distribution, these estimates will involve
considerable uncertainty which the exposure assessor will need to describe. Note
that in mis context, the probabilistic analysis addresses variability of exposure in the
population. Probabilistic techniques may also be applied to evaluate uncertainty in
estimates (see section 5, below). However, it is generally inappropriate to combine
distributions reflecting both uncertainty and variability to get a single overall
distribution. Such a result is not readily interpretable for the concerns of
environmental decision-making.
If only limited information on the distribution of the exposure or dose factors is
available/ the assessor should approach estimating the high end by identifying the
most sensitive variables and using high end values for a subset of these variables/
leaving others at their central values.* m doing mis, the assessor needs to avoid -
combinations of. parameter values that are inconsistent (e.g., low body weight used
in combination with high dietary intake rates)/ and must keep in mind die ultimate
objective of being within the distribution of actual expected exposures and-doses,
and not beyond it
If very little data are available on the ranges for the various variables, it will be
difficult to estimate exposures or doses and associated risks in the high end with
much confidence. One method mat has been used m such cases is to start with a
bounding estimate and "back off the limits used until the combination of
parameter values is, in the Judgment .of the assessor/ within the distribution of
expected exposure/ and itiH lies within the upper 10% of persons exposed.
Obviously, this method results in a large uncertainty and requires explanation.
2r. Central tendency descriptor
Central tendency descriptors generally reflect central estimates of exposure or dose.
The descriptor addressing central tendency may be based on either the arithmetic
mean exposure (average estimate) or the median exposure (median estimate), either
'Maximizing all vaziablH will in virtually all cam mutt in an estimate that is above the
actual values seen in the population. When the prfcidpal parameter* of the dace equation; egv
concentration (appropriately integrated over tfene)«.intaJc* rate, and duration, are broken out into sub-
component*, it may be necessary to use maximum values for moze than two olthew sub-component
parameters, depending on a sensitivity analysis.
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of which should be dearly labelled. The average estimate,-used to approximate the
arithmetic mean, can often be derived by using average values for all the exposure
factors.s It does not necessarily represent a particular individual on the distribution.
Because of the skewness of typical exposure profiles, die arithmetic mean may differ
substantially from the median estimate (ie., 50th percentile estimate, which is equal
to the geometric mean for a log normal distribution). The selection of which
descriptors) to present in the risk characterization will depend on the available data
and the goals of the assessment When data are limited/it may not be possible to
construct true median or mean estimates, but it is still possible to construct
estimates of central tendency. The discussion of the use of probabilistic techniques
in Section l(a) above also applies to estimates of central tendency.
2. Information about population exposure leads to another important way to
describe risk.
Population risk refers to an assessment of the extent of harm for the population as a
whole. In theory, it can be calculated by summing the individual risks for afl
individuals within the subject population. This task, of course, requires a great deal
more information man is normally, if ever, available.
The lands of questions addressed by descriptors of population risk include the
following:
• How many cases of a particular health effect might be probabilistically estimated
in mis population for a specific time period?
* For non-carcinogens, what portion of the population is within a specified range
of some reference level; eg* exceedance of the RfD (a dose), the RfC (a
ntration), or other health concern level?
• For carcinogens, what portion of file population is above a certain risk level,
such as 10-*?
These questions can lead to two different descriptors of population risk.
a. Probabilistic number of outs
the first descriptor Is the probabilistic nunux? of health effect cases estimated in the
population of interest over a specified time period. This descriptor can be obtained
either by (a) summing the individual risks over all the individuals in the
population, e.g. using an estimated distribution of risk in the population, when
SThis holds true when variables are added (eg., exposure* by different routes) or when
independent variables are multiplied (eg., concentration x intake). However, it would b« incorrect for
products.of correlated variable*, variables used as divisors, or for formulas involving exponents.
G-31
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such information is .available, or.(b) thtough-tfic.iise:oi a_riskmodfil.thatassvunes a.
linear non-threshold response to exposure, such as many carcinogenic models. In
these calculations, data will typically be available to address variability in individual
exposures. If risk varies linearly with exposure, multiplying the mean risk by the
population size produces an estimate of the number of cases. 6 At the present time,
most cancer potency values represent plausible upper bounds on risk. When such a
value is used to estimate numbers of cancer cases, it is important to understand-that
the result is also an upper bound. As with other risk descriptors, this approach may
not adequately address sensitive subgroups for which different dose-response curve
or exposure estimates might be needed.
Obviously, the more information one has, the more certain the estimate of mis risk
descriptor, but inherent uncertainties in risk assessment methodology place
limitations on the accuracy of the estimate. The discussion of uncertainty involved
in estimating the number of rut** should indicate mat thia descriptor i« not to be
confused with M* «rtai«riai pydietion of cases in the population (which is a
statistical prediction based on a great deal of empirical data).
In general, it should be recognized mat when small populations are exposed,
population risk estimates may be very smalL For example, if 100 people are exposed
to an individual, lifetime cancer risk of 10-*, the expected number of cases is 0.01. Jri
such situations, individual risk estimates will usually be a more meaningful
parameter for decision-makers.
b. Estimated percentage of population with risk greater than some level
For non-cancer effects, we generally have not developed the risk assessment
techniques to the point of knowing how to add risk probabilities, so a second
descriptor is usually more appropriate: An estimate of the percentage of the
population, or the number of persons, above a specified level of risk or within a
specified range of some reference level, e.g., exceedance of fee RfP or the RfC,
LOAEL, or otiier specific level of interest This descriptor must be obtained through
measuring or simulating the population distribution.
3. Information about the distribution of exposure and risk for different
of the population ate important components of a risk assessment. .
A risk manager might also ask questions about the distribution of the risk burden
among various segments of the subject population such as the following: How do
exposure and risk impact various subgroups?; and, what is the population risk of a
^However, certain important cautions apply (see EPA's Exposure Assessment Guidelines). Also,
this is not appropriate for norbcarcinogenk effects or for other types of cancer models. Faction-linear
cancer models, an estimate of population risk must be calculated using the dj**rih^tifm of individual
risks.
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particular subgroup? Questions about the distribution of exposure and risk among
such population segments require additional risk descriptors.
a. Highly exposed
Highly exposed subgroups can be identified, and where possible, characterized and
the magnitude of risk quantified. This descriptor is useful when there is (or is
expected to be) a subgroup experiencing significantly different exposures or doses
from that of the larger population. These sub-populations may be identified by age,
sex, lifestyle, economic factors, or other demographic variables. For example,
toddlers who play in contaminated soil and high fish consumers represent sub-
populations that may hive greater exposures to certain agents.
b. Highly susceptible
Highly susceptible subgroups can also be identified, and if possible, characterized and
the magnitude of risk quantified. This descriptor is useful when the sensitivity or
susceptibility to the effect for specific subgroups is (or is expected to be) significantly
different from that of the larger population. In order to calculate risk for these
subgroups, it wffl sometimes be necessary to use a different dose-response-
relationship; e.g., upon exposure to a chemical pregnant women, elderly people,
children, and people with certain illnesses may each be more sensitive man the
population as a whole. For example, children axe thought tooe bom highly exposed
and highly susceptible to the effects of environmental lead. A model has been
developed mat uses data on lead concentrations in different environmental media
to predict the resulting blood lead levels in children. Federal agencies are working
together to develop specific guidance on bk>od lead levels that present risks to
children.
It is important to note, however, mat the Agency's current methodologies for
developing reference doses and refierenos concentrations (RfDs and RfCs) are
designed to protect sensitive popuktion*. If data on sensitive human populations
are available (and there Is confidence in the quality of the data), oien the RfD is set at
the dose level at which no adverse effects are observed in the sensitive population
(e.g., RfDs for fluoride and nitrate). If no such data arc waflabte (for example, if the
RfD is developed using data from humans of average or unknown sensitivity) then
an additional 10-fold factor is used to account for variability between the average
human response and the response of more sensitive i idividuals.
Generally, selection of the population segments is a matter of either « priori interest
in the subgroup (eg., environmental Justice considerations), in which case the risk
assessor and risk manager can jointly agree oh which subgroups to highlight, or a
matter of discovery of a sensitive or highly exposed subgroup during the assessment
G-33
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process. In either case, once identified, the subgroup can be treated as_a population
in itself, and characterized in the same way as the larger population using the
descriptors for population and individual risk.
4. Situation-specific Information adds perspective on possible future events or
regulatory option
"What if-?" questions can be used to examine candidate, risk management options.
For example, consider the following:
* What if a pesticide applicator applies this pesticide without using protective
equipment?
• What if mis site becomes residential in the future?
• What risk levdwm occur if we set uV standard at 100 ppb?
Answering these ''What if~.?~ questions involves a calculation of risk based on
specific combinations of factors postulated within the assessment?. The answers to
these "What if...?" questions do not, by themselves, give information about how
likely the combination of values might be in the actual population or about how
many (if any) persons might be subjected to the potential future risk However,
information on the likelihood of the postulated scenario would also be desirable to
include in the assessment
When addressing projected changes for a population (either expected future
developments or consideration of different regulatory options), it is usually
appropriate to calculate a*d consider afl the ri^ de* When
central tendency or high end estimates an developed for a future scenario, these
descriptors should reflect reasonable expectations about future activities. For
example, in site-specific risk assessments/ future scenarios should be evaluated
when they are supported by realistic forecasts of future land use, and the risk
descriptors should be developed within that context
5. An evaluation of the uncertainty la the risk descriptors is an important
component of the uncertainty discussion in the assessment.
Risk descriptors are intended to address variability of risk within the population and
the overall advene impact on the population. In particular, differences between
high end and central tendency estimates reflect variability in the population, but not
the scientific uncertainty inherent in the risk estimates. As discussed above, mere
7Sotne program routinely develop future scenarios as past of developing a risk assessment.
Program-specific guidance may addnsa futun scenarios in mow detail than thty an described her*.
G-34
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will be uncertainty in all estimates of risk. These uncertainties can include
measurement uncertainties, modeling uncertainties, and assumptions to fill data
gaps. Risk assessors should address the impact of each of these factors on the
confidence in the estimated risk values.
Both qualitative and quantitative evaluations of uncertainty provide useful
information to users of the assessment The techniques of quantitative uncertainty
analysis are evolving rapidly and both the SAB (8) and Ac NRC (4) have urged the
Agency to incorporate these techniques into its risk analyses. However, it should be
noted mat a probabilistic assessment that uses oruy 'the assessor's best estimates for
distributions of population variables addxesses variability, but not uncertainty.
Uncertainties in the estimated risk distribution need to be separately evaluated.
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1. National Research Council. Rfelc Assessment in the Federal Government:
the PTQC**&. 1983.
2. U.S. EPA- l^fok AyufJMMiMiit and Manao*>rngnt; pyamework for I^flsioQ Making.
1984.
3. 133. EPA. "Risk Assessment Guidelines." 51 Federal Register, 33992-34054,
September 24, 1986.
4. National Research Council. Science and Ju«joetn«»nf |n. Fifk A!TWtff1Ttent. 1994.
5. U3. EPA -Guidelines for Exposure Assessment * 57 Federal Register, 22888-
22938, May 29, 1992.
6. UiS. EPA. "Guidelines for Developmental Toxicity Risk Assessment'" . 56 Federal
Register, 67398-63826, December 5, 1991.
8. Loehr, RA., and Matanoeki, G M>, Letter to Carol M. Browner, EPA
Administrator, Re: Quantitative Uncertainty Analysis for Radiological
Assessments. EPA Sdence Advisory Board, July 23, 1993 (EPA-SAB-RAC-COM-
93-006).
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ATTACHMENT
DRAFTING EPA RISK
CHARACTERIZATIONS
March 1995
There are a number of priiidples which form the basis for a risk characterization:
• Risk assessments should be transparent, in. that the conclusions drawn from the
science are identified separately from policy judgements, and the use of default
values or methods and the use of assumptions in the risk assessment are dearly
articulated.
• Risk characterizations should include a summary of the key issues and
conclusions of each of the other components of the risk assessment, as well as
describe the likelihood of harm. The summary should include a description of
the overall strengths and the limitations (including uncertainties) of the
assessment and conclusions.
• Risk characterizations should be consistent in general format, but recognize the
unique characteristics of each specific situation.
• Risk characterizations should include/ at least in a Qualitative sense, a discussion
of how a specific risk and its context compares with other similar risks This may
be accomplished by comparisons with other chemicals or situations in which the
Agency has decided to act, or with other situations which the public may be
familiar with. The discussion should highlight the limitations of such
comparisons.
• Risk characterization is a key component of risk communication, whkh is an
interactive process involving exchange of information and export opinion
among individuals/ groups and institutions.
The following outline is a guide and formatting aid for developing risk
characterizations for chemical risk assessments. Similar outlines will be developed
for other types of risk characterizations/ including site-specific assessments and
ecological risk assessments. A common format will assist risk managers in
evaluating and using risk characterization.
The outline has two parts. The first part tracks the risk assessment to bring forward
its major conclusions. The second part draws all of the information together to
characterize risk. The outline represents the expected findings for a typical complete
chemical assessment for a single chemical. However/ exceptions for the
G-37
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circumstances of individual assessments exist and should be explained as part of the
risk characterizatioiit. For example, particular statutory requirements, court-ordered
deadlines/ resource limitations, and other specific factors may be described to explain
why certain elements are incomplete.
This outline does not establish or affect legal rights or obligations. Rather, it "
confirms the importance of risk characterization, outlines relevant principles, and
identifies factors Agency staff shouM cx)nsider in mTplernenting me policy. On a
continuing basis, Agency management is expected to evaluate the policy as wen as
the results of its application throughout the Agency and undertake revisions as
necessary. Therefore, the policy does not stand alone; nor does it establish a binding
norm that is finally determinative of the issues addressed. Minor variations in its
application from one instance to another are appropriate and expected; they thus are
not a legitimate basis for delaying or complicating action on otherwise satisfactory
scientific, technical, and regulatory products.
PART ONE
SUMMARIZING MAJOR CONCLUSIONS IN RISK CHARACTERIZATION
1 Characterization of Hazard Identification
A. What is the key tcodcological study (or studies) mat provides the basis for
health concerns?
- How good is the key study ?
- Are the data from laboratory or field .studies? In single species or
multiple species?
-. If the hazard is carcinogenic/ comment on issues such as: observation of
single or multiple tumor sites; occurrence of benign or malignant
tumors; certain tumor types not linked to carcmogeruoty; use of the
maximum tolerated dose (MTD).
- If the hazard is other than carcinogenic, what endpointa were observed,
and what is the basis for.me ottfcal effect?
- Desoibe other studies that support this finding.
- Discuss any valid studies which conflict with this finding.
8; .Besides the health effect observed in the key study, axe mere other health
endpoints of concern?
- What are the significant data gaps?
C Discuss available epidemiological or clinical data. For epidemiblogical
studies:
- What types of studies were used, Le., ecologic, case-control cohort?
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- Describe the degree to which exposures were adequately described.
- Describe the degree to which confounding factors .were adequately
accounted for.
- Describe the degree to. which other causal factors were excluded.
D. How much is known about how (through what biological mechanism) the
chemical produces adverse effects?
- Discuss relevant studies of mechanisms of action or metabolism.
- Does mis information aid in the interpretation of the toxicity data?
- What are the implications for potential health effects?
£. Comment on any non-positive data irv animals or people, and whether
these data were considered in the hazard identification.
F. If adverse health affects have been observed in wildlife species, characterize
such effects by discussing the relevant issues as in A through E above
G. Summarize the'harard identification and discuss the significance of each of
he following:.
- confidence in conclusions;
- alternative conclusions that are also supported by the data;
• significant data gaps;
-------
— What assumptions or uncertainty factors were used?
— What is the confidence in the estimates?
- For carcinogenic hazards:
- What dose-response model was used? LMS or other linear-at-low-
dose model, a biologically-based model based on metabolism data,
or data about possible mechanisms of action?
- What is the basis for the selection of the particular dose-response
model used? Are there other models mat could have been used
with equal plausibility and scientific validity? What is the basis for
selection of the model used in this instance?
C Discuss the route and level of exposure observed, as compared to expected
human exposures.
- Are the! available data from the same route of exposure as the expected
human exposures? If not, are pharfnacoldnetic data available to
extrapolate across route of exposure?
- How far does one need to extrapolate from me observed data to
environmental exposures (one to two orders of magnitude? multiple
orders of magnitude)? What is the impact of such an extrapolation?
D. If adverse health affects have been observed in wildlife species, characterize
dose-response information using tine process outlined in A-C
HL Characterization of Exposure
A. What are the most significant sources of environmental exposure?
- Are there data on. sources of exposure from different media? What is the
relative'contribution of different sources- of exposure?
- What are the most significant environmental pathways for exposure?
6. Describe the populations that were assessed, including as the general
population, highly exposed groups/ and highly susceptible groups.
C Describe the basis for the exposure assessment, including any monitoring,
modeling, or other analyses of exposure distributions such as Monte-Carlo
or krieging.
D. What are the key descriptors of exposure?
- Describe the (range of) exposures to: "average" individuals, "high end"
individuals, general population, high exposure group(s), children,
susceptible populations.
- How was the central tendency estimate developed?- What factors and/or
methods were used in developing this estimate?
- How was the high-end estimate developed?
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- Is there iaf ormation on highly-exposed subgroups? Who are they?
What are their levels of exposure? How are they accounted for in the
assessment?
E. Is there reason to be concerned about cumulative or multiple exposures
because of ethnic, racial, or socioeconomic reasons?
F. If adverse health affects have been observed in wildlife species, characterize
wildlife exposure by discussing the relevant issues as in A through E above
G. Summarize exposure conclusions and discuss the following:
% - results of different approaches/ ie. modeling, monitoring,, probability
distributions;
- limitations of each/ and the range of most reasonable values; and
- confidence in the results obtained/ and the limitations to the results.
PART TWO
RISK CONCLUSIONS AND COMPARISONS
IV. Risk Conclusions
A. What is the overall picture of risk, based on the hazard identification, dose-
response and exposure characterizations?
B. What are the major conclusions and strengths of the assessment in each of
the three main analyses (i.e., hazard identification, dose-response, and
exposure assessment)?
C What are the major limitations and uncertainties in the three mam
analyses?
D. What axe the science policy options in each of the three major analyses?
- What are the alternative approaches evaluated?
- What are the reasons for the choices made?
V. Risk Context
A. What are the qualitative characteristics of the hazard (e.g., voluntary vs.
involuntary, technological vs. natural, etc}? Comment on findings, if, any,
from studies of risk perception mat relate to this hazard or similar hazards.
B. What are the alternatives to this hazard? How do the risks compare?
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C How does fills risk compare to other risks?
1. How does this xisk compare to other risks in this regulatory program/ or
otter similar risks that the EPA has made decisions about?
2. Where appropriate, can this risk be compared with past Agency
decisions, decisions by other federal or state agencies, or common risks
•with which people may. be familiar?
3. Describe the limitations of making these comparisons.
D. Comment on significant community concerns which influence public
perception of risk?
VL Existing Risk Information,
Comment on other xisk assessments mat nave been done on mis chemical by
EPA, other federal agerudes, or other organizations. Are there significantly
different conclusions that merit discussion?
VIL Other Information
Is there other information that would be useful to the risk manager or the
public in mis situation mat has not been described above?
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ATTACHMENT
I
I
I
Knpwvwsmwag
March '1995 2
IMPLEMENTATION PROGRAM
FOR
THE EPA POLICY ON RISK CHARACTERIZATION
Introduction
The EPA Science Policy Council (SPQ is implementing die Administrator's policy on
risk characterization through a year-long program of activities that will involve
risk assessors'and risk managers in .the practice of fully characterizing risk. This
interactive approach calls for inter- and intra-office activities to gain experience
with the fundamentals of die policy and to resolve issues that were identified during
Agency-wide review of early drafts. Implementation will include program-specific
guidance development; case study development; and risk characterization workshops
and ronntables for risk assessors and manages.
A SPC-sponsored "advisory group" will plan and execute these implementation
activities. This advisory* group will •organize an "implementation team" composed of
representatives, from the program offices, regions and ORD laboratories and centers.
This team will work closely with the advisory group to coordinate implementation
activities within their' offices.
Program
Risk characterizations often differ
according to the type of assessment
involved. The-aim is to work closely with
the Program Offices and Regions to
identify and address their specific risk
characterization needs and. where
appropriate, to develop assessment-
specific guidance.
This program updates and implement! the
risk characterization guidance issued in
early 1992. The policy features a paper
entitled. "Elements to Consider When
Prafting EPA Risk Characterizations.'*
This paper outlines generic elements for
characterizing risk, and provides a
prototype for assessment-specific
gui(
Program' and Regional
offices wiO use this paper to identify
and address risk characterization issues
with specific assessment
types that 'differ from the general
prototype (e.g.. site-specific and
ecological risk assessments). Lessons
learned from the case studies,
ronndtables and workshops (discussed
below) win also contribute to program-
specific ' guidance development
Case Studies
Today.- when asked to provide an
example of a "good** risk
characterization, few people can
identify good examples, let alone
examples that others would agree are
RISK CHARACTERIZATION
IMPLEMENTATION
*»»»
Mar i Apr < May JJ»*« i J»lr AnCjS«» I Oet No*
y!?-XJ5»S«Sn«ffKftfli«KM«9ff^f5fti/
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