United States
Environmental Protection
Agency
Otlice of Water
Regulations and Standards
Wasnmgton, DC 20460
Water
Juno, 1965
Environmental Profiles
and Hazard Indices
for Constituents
of Municipal Sludge:
Molybdenum
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PREFACE
This document is one of a series of preliminary assessments dealing
with chemicals of potential concern in municipal sewage sludge. The
purpose of these documents is to: (a) summarize the available data for
the constituents of potential concern, (b) identify the key environ-
mental pathways for each constituent related to a reuse and disposal
option (based on hazard indices), and (c) evaluate the conditions under
which such a pollutant may pose a hazard. Each document provides a sci-
entific basis for making an initial determination of whether a pollu-
tant, at levels currently observed in sludges, poses a likely hazard to
human health or the environment when sludge is disposed of by any of
several methods. These methods include landspreading on food chain or
nonfood chain crops, distribution and marketing programs, landfilling,
incineration and ocean disposal.
These documents are intended to serve as a rapid screening tool to
narrow an initial list of pollutants to those of concern. If a signifi-
cant hazard is indicated by this preliminary analysis, a more detailed
assessment will be undertaken to better quantify the risk from this
chemical and to derive criteria if warranted. If a hazard is shown to
be unlikely, no further assessment will be conducted at this time; how-
ever, a reassessment will be conducted after initial regulations are
finalized. In no case, however, will criteria be derived solely on the
basis of information presented in this document.
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TABLE OP CONTENTS
Page
PREFACE i
1. INTRODUCTION 1-1
2. PRELIMINARY CONCLUSIONS FOR MOLYBDENUM IN MUNICIPAL SEWAGE
SLUDGE 2-1
Landspreading and Distribution-and-Marketing 2-1
Landfilling 2-2
Incineration 2-2
Ocean Disposal 2-2
3. PRELIMINARY HAZARD INDICES FOR MOLYBDENUM IN MUNICIPAL SEWAGE
SLUDGE 3-1
Landspreading and Distribucion-and-MarkeCing 3-1
Effect on soil concentration of molybdenum (Index 1) 3-1
Effect on soil biota and predators of soil biota
(Indices 2-3) -. 3-2
Effect on plants and plant tissue
concentration (Indices 4-6) 3-4
Effect on herbivorous animals (Indices 7-8) 3-8
Effect on humans (Indices 9-13) 3-11
Landf illing 3-19
Index of groundwater concentration increment resulting
from landfilled sludge (Index 1) 3-19
Index of human toxicity resulting from
groundwater contamination (Index 2) 3-25
Incineration 3-26
Ocean Disposal 3-26
4. PRELIMINARY DATA PROFILE FOR MOLYBDENUM IN MUNICIPAL SEWAGE
SLUDGE 4-1
Occurrence 4-1,
Sludge 4-1
Soil - Unpolluted 4-1
Water - Unpolluted 4-2
Air 4-3
Food 4-3
11
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TABLE OP CONTENTS
(Continued)
Page
Human Effects 4-4
Ingestion 4-4
Inhalation 4-4
Plant Effects 4-5
Phytotoxicity 4-5
Uptake 4-6
Domestic Animal and Wildlife Effects ". 4-6
Toxicity 4-6
Uptake 4-7
Aquatic Life Effects 4-8
Soil Biota Effects 4-9
Physicochemical Data for Estimating Fate and Transport 4-9
5. REFERENCES 5-1
APPENDIX. PRELIMINARY HAZARD INDEX CALCULATIONS FOR
MOLYBDENUM IN MUNICIPAL SEWAGE SLUDGE A-l
111
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SECTION 1
INTRODUCTION
This preliminary data profile is one of a series of profiles
dealing with chemical pollutants potentially of concern in municipal
sewage sludges. Molybdenum (Mo) was initially identified as being of
potential concern when sludge is landspread (including distribution and
marketing) or placed in a Landfill.* This profile is a compilation of
information that may be useful in determining whether Mo poses an actual
hazard to human health or the environment when sludge is disposed of by
these methods.
The focus of this document is the calculation of "preliminary
hazard indices" for selected potential exposure pathways, as shown in
Section 3. Each index illustrates the hazard that could result from
movement of a pollutant by a given pathway to cause a given effect
(e.g., sludge •* soil •+• plant uptake •* animal uptake •*• human toxicity).
The values and assumptions employed in these calculations tend to repre-
sent a reasonable "worst case"; analysis of error or uncertainty has
been conducted to a limited degree. The resulting value in most cases
is indexed to unity; i.e., values >1 may indicate a potential hazard,
depending upon the assumptions of the calculation.
The data used for index calculation have been selected or estimated
based on information presented in the "preliminary data profile",
Section 4. Information in the profile is based on a compilation of the
recent literature. An attempt has been made to fill out the profile
outline to the greatest extent possible. However, since this is a pre-
liminary analysis, the literature has not been exhaustively perused.
The "preliminary conclusions" drawn from each index in Section 3
are summarized in Section 2. The preliminary hazard indices will be
used as a screening tool to determine which pollutants and pathways may
pose a hazard. Where a potential hazard is indicated by interpretation
of these indices, further analysis will include a more detailed exami-
nation of potential risks as well as an examination of site-specific
factors. These more rigorous evaluations may change the preliminary
conclusions presented in Section 2, which are based on a reasonable
"worst case" analysis.
The preliminary hazard indices for selected exposure routes
pertinent to landspreading and distribution and marketing or landfilling
practices are included in this profile. The calculation formulae for
these indices are shown in the Appendix. The indices are rounded to two
significant figures.
* Listings were determined by a series of expert workshops convened
during March-May, 1984 by the Office of Water Regulations and
Standards (OWRS) to discuss landspreading, landfilling, incineration,
and ocean disposal, respectively, of municipal sewage sludge.
1-1
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SECTION 2
PRELIMINARY CONCLUSIONS FOR MOLYBDENUM IN MUNICIPAL SEWAGE SLUDGE
The following preliminary conclusions have been derived from Che
calculation of "preliminary hazard indices", which represent conserva-
tive or "worst case" analyses of hazard. The indices and their basis
and interpretation are explained in Section 3. Their calculation
formulae are shown in the Appendix.
I. LANDSPREADING AND DISTRIBUTION-AND-MARKETING
A. Effect on Soil Concentration of Molybdenum
Mo levels in soil are expected to increase when Mo-containing
sludges are applied at high cumulative rates' (50 to 500 me/ha)
(see Index 1).
B. Effect on Soil Biota and Predators of Soil Biota
Conclusions were not drawn because index values could not be
calculated due to lack, of data.
C. Effect on Plants and Plant Tissue Concentration
Landspreading of sludge is not expected to result in a concen-
tration of Mo in soil which exceeds a phytotoxic concentration
(see Index 4).
The concentration of Mo in plants grown on sludge-amended soil
may be expected, in general, to exceed the background tissue
concentration when sludge is applied at high cumulative rates
(50 and 500 mt/ha). An exception may be found for plants con-
sumed by animals "which may concentrate Mo higher chan the
background tissue concentration when sludge containing a high
concentration of Mo is applied at any rate. Another exception
is for human-consumed plants which are expected to have a tis-
sue Mo concentration higher than the background concentration
when sludge containing a typical concentration of Mo is
applied at a high rate (500 mt/ha) (see Index 5). The plant
tissue concentrations predicted by Index 5 are not precluded
by phytotoxicity (see Index 6).
D. Effect on Herbivorous Animals
Landspreading of sludge is not expected to pose a toxic hazard
due to Mo for herbivorous animals which feed on plants grown
on sludge-amended soil, except when sludge with a high concen-
tration of Mo is applied at a high rate (500 mt/ha) (see
Index 7). Also, a toxic hazard due to Mo is not expected to
result from landspreading of sludge for herbivorous animals
which incidentally ingest sludge or sludge-amended soil (see
Index 8).
2-1
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E. Effect on Humans
The consumption of crops grown on sludge-amended soil by
humans is not expected to pose a health threat due to Mo (see
Index 9).
Landspreading of sludge is not expected to result in a health
hazard due Co Mo for humans who consume animal products
derived from stock fed crops grown on sludge-amended soil (see
Index 10); who consume animal products derived from stock.
which had incidentally ingested sludge-amended soil (see
Index 11); or who ingest sludge-amended soil (see Index 12).
An aggregate human health hazard due to Mo is not expected to
result from landspreading of sludge (see Index 13).
II. LANDFILUNG
Landfilled sludge may slightly increase the groundwater concentra-
tion of Mo above background 'concentrations; this increase may be
large at disposal sites with all worst-case conditions (see
Index 1). The disposal of sludge in landfills is not expected to
pose a hazard to human health due to Mo in groundwater (see
Index 2).
III. nrCIHEHATION
Based on the recommendations of the experts at the OWES meetings
(April-May, 1984), an assessment of this reuse/disposal option is
not being conducted at this time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
IV. OCEAN DISPOSAL
Based on the recommendations of the experts at the OWRS meetings
(April-May, 1984), an assessment of this- reuse/disposal option is
not being conducted at this time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
2-2
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SECTION 3
PRELIMINARY HAZARD INDICES FOR MOLYBDENUM
IN MUNICIPAL SEWAGE SLUDGE
I. LAHDSPREADING AND DISTRIBUTION-AND-MARKETING
A. Effect on Soil Concentration of Molybdenum
1. Index of Soil Concentration Increment (Index 1)
a. Explanation - Shows degree of elevation of pollutant
concentration in soil to which sludge is applied.
Calculated for sludges with typical (median if
available) and worst (95th percentile if available)
pollutant concentrations, respectively, for each of
four sludge loadings. Applications (as dry matter)
are chosen and explained as follows:
0 tnt/ha No sludge applied. Shown for all indices
for purposes of comparison, to distin-
guish hazard posed by sludge from pre-
existing hazard posed by background
levels or other sources of the pollutant.
5 rat/ha Sustainable yearly agronomic application;
i.e., loading typical of agricultural
practice, supplying -^50 kg available
nitrogen per hectare.
50 mt/ha Higher application as may be used on
public lands, reclaimed areas or home
gardens.
500 mt/ha Cumulative loading after years of
application.
b. Assumptions/Limitations - Assumes pollutant is dis-
tributed and retained within the upper 15 cm of soil
(i.e., the plow layer), which has an approximate
mass (dry matter) of 2 x 10^-mt/ha.
c. Data Used and Rationale
i. Sludge concentration of pollutant (SC)
Typical 9.8 Ug/g DW
Worst 40 ug/g DW
The typical and worst sludge concentrations are
the median and 95th percentile values, respec-
tively, statistically derived from sludge con-
centration data from a survey of 16 publicly-
3-1
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owned treatment works (POTWs) (Furr et aL.,
1976b). (See Section 4, p. 4-1.)
ii. Background concentration of pollutant in soil
(BS) =2.6 Ug/g DW
The normal concentration of Mo in unpolluted
soil is reported by Allaway (1968) to be 2 ppm.
The range of Mo concentrations is reported to
be 0.2 to 5 ppm (Allaway, 1968). The value of
2.6 ppm was selected as being approximately the
midpoint of this range. (See Section 4,
p. 4-1.)
Index 1 Values
Sludge Application Rate (mt/ha)
Sludge
Concentration
Typical
Worst
0
1
1
5
1.0
1.0
50
1.1
1.4
500
1.6
3.9
e. Value Interpretation - Value equals factor by which
expected soil concentration exceeds background when
sludge is applied. (A value of 2 indicates concen-
tration is doubled; a value of 0.5 indicates
reduction by one-half.)
f. Preliminary Conclusion - Mo levels in soil are
expected to increase when Mo-containing sludges are
applied at high cumulative rates (50 to 500 mt/ha).
B. Effect on Soil Biota and Predators of Soil Biota
1. Index of Soil Biota Toxicity (Index 2)
a. Explanation - Compares pollutant concentrations in
sludge-amended soil with soil concentration shown to
be toxic for some organism.
b. Assumptions/Limitations - Assumes pollutant form in
sludge-amended soil is equally bioavailable and
toxic as form used in study where toxic effects were
demonstrated.
c. Data 'Used and Rationale
i. Index of soil concentration increment (Index 1)
. See Section 3, p. 3-2.
3-2
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ii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
iii. Soil concentration toxic to soil biota (TB) -
Data not immediately available.
d. Index 2 Values - Values were not calculated due to
lack of data.
e. Value Interpretation - Value equals factor by which
expected soil concentration exceeds toxic concentra-
tion. Value >1 indicates a toxic hazard may exist
for soil biota.
f. Preliminary Conclusion - Conclusion was not drawn
because index values could not be calculated.
2. Index of Soil Biota Predator Toxicity (Index 3)
a* Explanation - Compares pollutant concentrations
expected in tissues of organisms inhabiting sludge-
amended soil with food concentration shown to be
toxic to a predator on soil organisms.
b. Assumptions/Limitations - Assumes pollutant form
bioconcentrated by soil biota is equivalent in tox-
icity to form used to demonstrate toxic effects in
predator. Effect Level in predator may be estimated
from that in a different species.
c. Data Used and Rationale
i. Index of soil concentration increment (Index 1)
See Section 3, p. 3-2.
ii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
iii. Uptake slope of pollutant in soil biota (UB) -
Data not immediately available.
iv. Background concentration in soil biota (BB) -
Data not immediately available.
v. Feed concentration toxic to predator (TR) -
Data not immediately available.
d. Index 3 Values - Values were not calculated due to
lack of data.
3-3
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e. Value Interpretation - Value equals factor by which
expected concentration in soil biota exceeds that
which is toxic to predator. Value > 1 indicates a
toxic hazard may exist for predators of soil biota.
f. Preliminary Conclusion - Conclusion was not drawn
be'cause index values could not be calculated.
C. Effect on Plants and Plant Tissue Concentration
1. Index of Phytotoxicity (Index 4)
a. Explanation - Compares pollutant concentrations in
sludge-amended soil with the lowest soil
concentration shown to be toxic for some plant.
b. Assumptions/Limitations - Assumes pollutant form in
sludge-amended soil is equally bioavailable and
toxic as form used in study where toxic effects were
demonstrated.
c. Data Used and Rationale
i. Index of soil concentration increment (Index 1)
See Section 3, p. 3-2.
ii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
iii. Soil concentration toxic to plants (TP) =
65 Ug/g DW
Using the worst-case values for uptake of Mo by
plants (0.769 ug/g[kg/ha]~^) and the 'assumed
plant tissue concentration associated wich phy-
totoxicity (100 ug/g), the phytotoxicity con-
centration in soil was derived (65 ug/g). See
Indices 5 and 6 for uptake of Mo by plants and
the plant tissue concentration associated wich
phytotoxicity.
d. Index 4 Values
Sludge Application Rate (mt/ha)
Sludge
Concentration 0 5 50 500
Typical
Worst
0.040
0.040
0.040
0.041
0.043
0.054
0.062
0.16
3-4
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e. Value Interpretation - Value equals factor by which
soil concentration exceeds phytotoxic concentration.
Value > 1 indicates a phytotoxic hazard may exist.
f. Preliminary Conclusion - Landspreading of sludge is
not expected to result in a concentration of Mo in
soil which exceeds a phytotoxic concentration.
2. Index of Plant Concentration Increment Caused by Uptake
(Index 5)
a. Explanation - Calculates expected tissue concentra-
tion increment in plants grown in sludge-amended
soil, using uptake data for che most responsive
plant species in the following categories: (1)
plants included in the U.S. human diet; and (2)
plants serving as animal feed. Plants used vary
according to availability of data.
b. Assumptions/Limitations - Assumes a linear uptake
slope. Neglects che effect of time; i.e., cumula-
tive loading over several years is treated equiva-
lently to single application of the same amount.
The uptake factor chosen for the animal diet is
assumed to be representative of all crops in the
animal diet. See also Index 6 for consideration of
phytotoxicity.
c. Data Used and Rationale
i. Index of soil concentration increment (Index 1)
See Section 3, p. 3-2.
ii. Background concentration of pollutant in soil
(BS) =2.6 Ug/g DW
See Section 3, p. 3-2.
iii. Conversion factor between soil concentration
and application rate (CO) = 2 kg/ha
Assumes pollutant is distributed and retained
within upper 15 cm of soil (i.e. plow layer)
which has an approximate mass (dry matter) of
2 x 103.
iv. Uptake slope of pollutant in plant tissue (UP)
Animal diet:
Fodder rape 0.769 Ug/g tissue DW (kg/ha) "^
Human diet:
Leeks 0.048 Ug/g tissue DW (kg/ha) ~1
3-5
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The uptake slope obtained for a crop consumed
by animals was 0.769 ug/gCkg/ha)'1 for fodder
rape grown on sludge-amended soil (Page, 1974).
This is the only uptake slope in the profile
for a crop consumed by animals. The only
uptake slopes available for plant tissues con-
sumed by humans were calculated from the field
data of Page (1974) for leeks and roots of
beets, potatoes, and carrots. Only leeks and
beet roots had positive uptake slopes; the val-
ues were 0.048 and 0.012 ug/g(kg/ha)~l, respec-
tively. The value for leeks was selected
because it was the highest, in keeping with a
conservative approach. (See Section 4,
p. 4-11.)
v. Background concentration in plant tissue (BP)
Animal diet:
Fodder rape 1.1 Ug/g DW
Human diet:
Leeks 0.5 Ug/g DW
Background concentrations in plant tissue were
taken from the same study from which the uptake
slopes were obtained (Page, 1974). (See
Section 4, p. 4-11.)
d. Index 5 Values
Sludge Application
Rate (mt/ha)
Sludge
Diet Concentration 0 5 50 500
Animal
Typical
Worst
1.0
1.0
1.0
1.1
1.2
2.3
3.0
11
Human Typical 1.0 1.0 1.0 1.3
Worst 1.0 1.0 1.2 2.4
Value Interpretation - Value equals factor by which
plant tissue concentration is expected co increase
above background when grown in sludge-amended soil.
Preliminary Conclusion - The concentration of Mo in
plants grown on sludge-amended soil may be expected,
in general, to exceed the background tissue concen-
tration when sludge is applied at high cumulative
rates (50 and 500 mt/ha). An exception may be found
for plants consumed by animals which may concentrate
Mo higher than the background tissue concentration
when sludge containing a high concentration of Mo is
3-6
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applied at any rate. Another exception is for
human-consumed plants which are expected to have a
tissue Mo concentration higher than the background
concentration when sludge containing a typical
concentration of Mo is applied at a high rate
(500 rat/ha). .
3. Index of Plant Concentration Increment Permitted by
Phytotoxicity (Index 6)
a. Explanation - Compares maximum plant tissue concen-
tration associated with phytotoxicity with back-
ground concentration in same plant tissue. The
purpose is to determine whether che plant concentra-
tion increments calculated in Index 5 for high
applications are truly realistic, or whether such
increases would be precluded by phytotoxicity.
b. Assumptions/Limitations - Assumes that tissue con-
centration will be a consistent indicator of
phytotoxicity.
c. Data Used and Rationale
i. Maximum plant tissue concentration associated
with phytotoxicity (PP) = 100 ]ig/g DW
Plant specific data were not immediately avail-
able for plant tissue concentrations associated
with phytotoxicity, but a more general value of
phytotoxicity at concentrations >100 Ug/g has
been conservatively assumed from information
provided by Allaway (1968). Allaway indicated
that low toxicity is seen when Mo concentration
exceeds 100- Ug/g. (See Section 4, p. 4-10.)
ii. Background concentration in plant tissue (BP)
Animal diet:
Fodder rape L.I Ug/g DW
Human diet:
Leeks 0.5 ug/g DW
See Section 3, p. 3-6.
d. Index 6 Values
Plant Index Value
Fodder rape 91
Leeks 200
3-7
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e. Value Interpretation - Value gives Che maximum
factor of tissue concentration increment (above
background) which is permitted by phytotoxicity.
Value is compared with values for the same or simi-
lar plant tissues given by Index 5. The lowest of
the two indices indicates the maximal increase which
can occur at any given application rate.
f. Preliminary Conclusion - The plant tissue concentra-
tions predicted by Index 5 are not precluded by
phytotoxicity.
D. Effect on Herbivorous Animals
1. Index of Animal Toxicity Resulting from Plant Consumption
(Index 7)
a. Explanation - Compares pollutant concentrations
expected in plant tissues grown in sludge-amended
soil with food concentration shown to be toxic to
wild or domestic herbivorous animals. Does not con-
sider direct contamination of forage by adhering
sludge.
b. Assumptions/Limitations - Assumes pollutant form
taken up by plants is equivalent in toxicity to form
used to demonstrate toxic effects in animal. Uptake
or toxicity in specific plants or animals may be
estimated from other species.
c. Data Used and Rationale
i. Index of plant concentration increment caused
by uptake (Index 5)
Index 5 values used are chose for an animal
diet (see Section 3, p. 3-6).
ii. Background concentration in plant tissue (BP) =
1.1 Jlg/g DW
The background concentration value used is for
the plant chosen for Che animal diet (see
Section 3, p. 3-6).
iii. Feed concentration toxic to herbivorous animal
(TA) = 5 ug/g DW
5 Ug/g of Mo is a conservative toxic value for
cattle when copper (Cu) levels of feed or for-
ages are in Che normal range of 3 to 10 ppm
(Buck, 1978). High Mo in diet may lead to a
disturbed Cu metabolism in ruminants (Buck,
1978). . Lower concentrations of Mo can be toxic
3-8
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to animals when Cu concentrations in feed are
not in the normal range. Other values of Mo
are reported to be toxic, but 5 Ug/g was chosen
as a worst-case value because it is the lowest
value observed with adverse effects on animals.
(See Section 4, p. 4-15.)
d. Index 7 Values
Sludge Application Rate (mt/ha)
Sludge
Concentration 0 5 50 500
Typical
Worst
0.22
0.22
0.23
0.25
0.27
0.50
0.66
2.5
e. Value Interpretation - Value equals factor by which
expected plant tissue concentration exceeds that
which is toxic to animals. Value > 1 indicates a
toxic hazard may exist for herbivorous animals.
f. Preliminary Conclusion - Landspreading of sludge is
not expected to pose a toxic hazard due to Mo for
herbivorous animals which feed on plants grown on
sludge-amended soil, except when sludge with a high
concentration of Mo is applied at a high rate
(500 mt/ha).
Index of Animal Toxicity Resulting from Sludge Ingestion
(Index 8)
a. Explanation - Calculates the amount of pollutant in
a grazing animal's diet resulting from sludge adhe-
sion to forage or from incidental ingestion of
sludge-amended soil and compares this with the
dietary toxic threshold concentration for a grazing
animal.
b. Assumptions/Limitations - Assumes that sludge is
applied over and adheres to growing forage, or that
sludge constitutes 5 percent of dry matter in the
grazing animal's diet, and that pollutant form in
sludge is equally bioavailable and toxic as form
used to demonstrate toxic effects. Where no sludge
is applied (i.e., 0 mt/ha), assumes diet is 5 per-
cent soil as a basis for comparison.
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Data Used and Rationale
i. Sludge concentration of pollutant (SC)
Typical 9.8 ug/g DW
Worst 40 ug/g DW
See Section 3, p. 3-1.
ii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
iii. Fraction of animal diet assumed to be soil (GS)
= 5%
Studies of sludge adhesion Co growing forage
following applications of liquid or filter-cake
sludge show that when 3 to 6 mt/ha of sludge
solids is applied, clipped forage initially
consists of up to 30 percent sludge on a dry-
weight basis (Chaney and Lloyd, 1979; Boswell,
1975). However, this contamination diminishes
gradually with time and growth, and generally
is not detected in the following year's growth.
For example, where pastures amended at 16 and
32 mt/ha were grazed throughout a growing sea-
son (168 days), average sludge content of for-
age was only 2.14 and 4.75 percent,
respectively (Bertrand et al., 1981). It seems
reasonable to assume that animals may receive
Long-term dietary exposure to 5 percent sludge
if maintained on a forage to which sludge is
regularly applied. This estimate of 5 percent
sludge is used regardless of application rate,
since the above studies did not show a clear
relationship between application rate and ini-
tial contamination, and since adhesion is not
cumulative yearly because of die-back.
Studies of grazing animals indicate that soil
ingestion, ordinarily <10 percent of dry weight
of diet, may reach as high as 20 percent for
cattle and 30 percent for sheep during winter
months when forage is reduced (Thornton and
Abrams, 1983). If the soil were sludge-
amended, it is conceivable that up Co 5 percent
sludge may be ingested in this manner as well.
Therefore, this value accounts for either of
these scenarios, whether forage is harvested or
grazed in the field.
3-10
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iv. Feed concentration toxic to herbivorous animal
(TA) = 5 Ug/g DW
See Section 3, p. 3-8.
d. Index 8 Values
Sludge Application Rate (mt/ha)
Sludge
Concentration 0 5 50 500
Typical
Worst
0.030
0.030
0.10
0.40
0.10
0.40
0.10
0.40
e. Value Interpretation - Value equals factor by which
expected dietary concentration exceeds toxic concen-
tration. Value > 1 indicates a toxic hazard may
exist for grazing animals.
£. Preliminary Conclusion - A toxic hazard due to Mo is
not expected from landspreading of sludge for herbi-
vorous animals which incidentally ingest sludge or
sludge-amended soil.
E. Effect on Humans
1. Index of Human Toxicity Resulting from Plant Consumption
(Index 9)
a. Explanation - Calculates dietary intake expected co
result from consumption of crops grown on sludge-
amended soil. Compares dietary intake with accept-
able daily intake (ADI) of the pollutant.
b. Assumptions/Limitations - Assumes that all crops are
grown on sludge-amended soil and that all those con-
sidered to be affected take up the pollutant at the
same rate as the most responsive plant(s) (as chosen
in Index 5). Divides possible variations in dietary
intake into two categories: toddlers (18 months to
3 years) and individuals over 3 years old.
c. Data Used and Rationale
i. Index of plant concentration increment caused
by uptake (Index 5)
Index 5 values used are those for a human diet
(see Section 3, p. 3-6).
ii. Background concentration in plant tissue (BP) =
0.5 ug/g DW
3-11
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The background concentration value used is for
the plant chosen for the human diet (see
Section 3, p. 3-6).
ill. Daily human dietary intake of affected plant
tissue (DT)
Toddler 74.5 g/day
Adult 205 g/day
The intake value for adults is based on daily
intake of crop foods (excluding fruit) by vege-
tarians (Ryan et al., 1982); vegetarians were
chosen to represent the worst case. The value
for toddlers is based on the FDA Revised Total
Diet (Pennington, 1983) and food groupings
listed by the U.S. EPA (1984). Dry weights for
individual food groups were estimated from
composition data given by the U.S. Department
of Agriculture (USDA) (1975). These values
were composited 'to estimated dry-weight
consumption of all non-fruit crops.
iv. Average daily human dietary intake of pollutant
(DI)
Toddler 112 Ug/day
Adult 335 Ug/day
Wester (1974, in Friberg et al., 1975) deter-
mined the average daily intake of 4 patients.
Schroeder (1970, in Friberg et al., 1975) esti-
mated the daily intake in the average U.S. diet
to be 335 ug/day. The Schroeder value is pre-
ferred for this index because it is based on
the average U.S. diet, and the Wester values
are based on diets of only a few individuals.
An average U.S. total Mo intake for toddlers
has not been established. The value for
toddlers was assumed to be 1/3 of the adult
value. (See Section 4, p. 4-3.)
v. Acceptable daily intake of pollutant (ADI) =
3712 Ug/day
Suttle (1973, in Jarrell et al., 1980) states
that, where the Mo content of human dietary
meat and vegetables exceeds 4000 Ug/kg DW,
there is a concern for upsetting the Cu metabo-
lism. The total adult food intake (2875 g/day
WW) (FDA, 1980a; 1980b) was converted to dry
weight (928 g/day DW) using values from USDA
(1975). The total intake (0.928 kg/day DW) was
then multiplied by the maximum human dietary Mo
3-12
-------
concentration, 4000 Ug/kg DW, to obtain an
acceptable daily intake of 3712 ug/day. (See
Section 4, p. 4-4.)
d. Index 9 Values
Sludge Application
Rate (mt/ha)
Sludge
Group
Toddler
Adult
Concentration
Typical
Worst
Typical
Worst
0
0.030
0.030
0.090
0.090
5
0.030
0.030
0.090
0.091
50
0.031
0.032
0.091
0.095
500
0.033
0.45
0.098
0.13
e. Value Interpretation - Value equals factor by which
expected intake exceeds ADI. Value > 1 indicates a
possible human health threat. Comparison with the
null index value at 0 mt/ha indicates the degree to
which any hazard is due to sludge application, as
opposed to pre-existing dietary sources.
f. Preliminary Conclusion - The consumption of crops
grown on sludge-amended soil by humans is not
expected to pose a health threat due to Mo.
2. Index of Human Toxicity Resulting from Consumption of
Animal Products Derived from Animals Feeding on Plants
(Index 10)
a. Explanation - Calculates human dietary intake
expected to result from consumption of animal
products ' derived from domestic animals given feed
grown on sludge-amended soil (crop or pasture land)
but not directly contaminated by adhering sludge.
Compares expected intake with ADI.
b. Assumptions/Limitations - Assumes that all animal
products are from animals receiving all their feed
from sludge-amended soil. The uptake slope of pol-
lutant in animal tissue (UA) used is assumed to be
representative of all animal tissue comprised by the
daily human dietary intake (DA) used. Divides pos-
sible . variations in dietary intake into two categor-
ies: toddlers (18 months to 3 years), and
individuals over 3 years old.
3-13
-------
Data Used and Rationale
i. Index of plant concentration increment caused
by uptake (Index 5)
Index 5 values used are those for an animal
diet (see Section 3, p. 3-6).
ii. Background concentration in plant tissue (BP) =
1.1 Ug/g DW
The background concentration value used is £or
the plant chosen for the animal diet (see
Section 3, p. 3-6).
iii. Uptake slope of pollutant in animal tissue (UA)
= 1.028 ug/g tissue DW (ug/g feed DW)'1
The only data immediately available for uptake
slopes were for guinea pigs (Furr at al.,
1976a). It is assumed that the uptake for
guinea pigs is representative of larger
herbivores. (See Section 4, p. 4-17.)
iv. Daily human dietary intake of affected animal
tissue (DA)
Toddler 0.97 g/day
Adult 5.76 g/day
The FDA Revised Total Diet (Pennington, 1983)
lists average daily intake of beef liver (fresh
weight) for various age-sex classes. The 95th
percentile of liver consumption (chosen in
order to be conservative) is assumed to be
approximately three times the mean * values.
Conversion to dry weight is based on data from
the USDA (1975).
v. Average daily human dietary intake of pollutant
(DI)
Toddler 112 Ug/day
Adult 335 Ug/day
See Section 3, p. 3-12.
vi. Acceptable daily intake of pollutant (ADI) =
3712 ug/day
See Section 3, p. 3-12.
3-14
-------
Index 10 Values
Sludge Application
Rate (mt/ha)
Sludge
Group Concentration 05 50 500
Toddler
Typical
Worst
0.030
0.030
0.030
0.030
0.030
0.031
0.031
0.033
Adult Typical 0.090 0.090 0.091 0.09A
Worst 0.090 0.090 0.092 0.11
e. Value Interpretation - Same as for Index 9.
f. Preliminary Conclusion - Landspreading of sludge is
not expected to result in a health hazard due to Mo
for humans who consume animal products derived from
stock fed crops grown on sludge-amended soil.
3. Index of Human Toxicity Resulting from Consumption of
Animal Products Derived from Animals Ingesting Soil
(Index 11)
a. Explanation - Calculates human dietary intake
expected to result from consumption of animal prod-
ucts derived from grazing animals incidentally
ingesting sludge-amended soil. Compares expected
intake with ADI.
b. Assumptions/Limitations - Assumes that all animal
products are from animals grazing sludge-amended
soil, and that all animal products consumed take up
the pollutant at the highest rate observed for
muscle o'f any commonly consumed species or at the
rate observed for beef liver or dairy products
(whichever is higher). Divides possible variations
in dietary intake into two categories: toddlers
(18 months to 3 years) and individuals over three
years old.
c. Data Used and Rationale
i. Animal tissue = Guinea pig liver
See Section 3, p. 3-14,
ii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
3-15 .
-------
iii. Sludge concentration of pollutant (SC)
Typical 9.8 Ug/g DW
Worst 40 Ug/g DW
See Section 3, p. 3-1.
iv. Fraction of animal diet assumed to be soil (GS)
= 5%
See Section 3, p. 3-10.
v. Uptake slope of pollutant in animal tissue (UA)
= 1.028 ug/g tissue DW (ug/g feed DW)'1
See Section 3, p. 3-14.
vi. Daily human dietary intake of affected animal
tissue (DA)
Toddler 0.97 g/day
Adult 5.76 g/day
See Section 3, p. 3-14.
vii. Average daily human dietary intake of pollutant
(DI)
Toddler 112 Ug/day
Adult 335 Ug/day
See Section 3, p. 3-12.
viii. Acceptable daily intake of pollutant (ADI) =
3712 US/day
See Section 3, p. 3-12.
d. Index 11 Values
Sludge Application
Rate (mt/ha)
Group
Toddler
Adult
Sludge
Concentration
Typical
Worst
Typical
Worst
0
0.030
0.030
0.090
0.090
5
0.030
0.031
0.091
0.093
50
0.030
0.031
0.091
0.093
500
0.030
0.031
0.091
0.093
Value Interpretation - Same as for Index 9.
3-16
-------
£. Preliminary Conclusion - Landspreading of sludge is
not expected to pose a health hazard due to Mo for
humans who consume animal products derived from
stock, which had incidentally ingested sludge-amended
soil.
4. Index of Human Toxicity from Soil Ingestion (Index 12)
a. Explanation - Calculates the amount of pollutant in
the diet of a child who ingests soil (pica child)
amended with sludge. Compares this amount with ADI.
b. Assumptions/Limitations - Assumes that the pica
child consumes an average of 5 g/day of sludge-
amended soil. If an ADI specific for a child is not
available, this index assumes that the ADI for a
10 kg child is the same as that for a 70 kg adult.
It is thus assumed that 'uncertainty factors used in
deriving the ADI provide protection for the child,
taking into account the smaller body size and any
other differences in sensitivity.
c. Data Used and Rationale
i. Index of soil concentration increment (Index 1)
See Section 3, p. 3-2.
* ii. Sludge concentration of pollutant (SC)
Typical 9.8 ug/g DW.
Worst 40 Ug/g DW
See Section 3, p. 3-1.
iii. Background concentration of pollutant in soil
(BS) = 2.6 Ug/g DW
See Section 3, p. 3-2.
iv. Assumed amount of soil in human diet (DS)
Pica child 5 g/day
Adult 0.02 g/day
The value of 5 g/day for a pica child is a
worst-case estimate employed by U.S. EPA's
Exposure Assessment Group (U.S. EPA, 1983a).
The value of 0.02 g/day for an adult is an
estimate from U.S. EPA (1984).
3-17
-------
d.
v. Average daily human dietary intake of pollutant
(DI)
Toddler 112 Ug/day
Adult 335 Ug/day
See Section 3, p. 3-12.
vi. Acceptable daily intake of pollutant (ADI) =
3712 Ug/day
See Section 3, p. 3-12.
Index 12 Values
Sludge Application
Rate (mt/ha)
Group
Toddler
Adult
Sludge
Concentration
Typical
Worst
Typical
Worst
0
0.034
0.034
0.090
0.090
5
0.034
0.034
0.090
0.090
50
0.034
0.035
0.090
0.090
500
0.036
0.044
0.090
0.090
Pure
Sludg'
0.043
0.084
0.090
0.090
e. Value Interpretation - Same as for Index 9.
f. Preliminary Conclusion - Landspreading of sludge is
not expected to pose a health hazard due to Mo for
humans who ingest sludge-amended soil.
5. Index of Aggregate Human Toxicity (Index 13)
a. Explanation - Calculates the aggregate amount of
pollutant in the human diet resulting from -pathways
described in Indices 9 to 12. Compares this amount
wich ADI.
b. Assumptions/Limitations - As described for Indices 9
to 12.
c. Data Used and Rationale - As described for Indices 9
to 12.
3-18
-------
d. Index 13 Values
Sludge Application
Rate (mt/ha)
Sludge
Group
Toddler
Adult
Concentration
Typical
Worst
Typical
Worst
0
0.034
0.034
0.090
0.090
5
0.034
0.035
0.091
0.094
50
0.034
0.038
0.092
0.10
500
0.039
0.062
0.10
0.15
e. Value Interpretation - Same as for Index 9.
f. Preliminary Conclusion - An aggregate human health
hazard due to Mo is not expected to result from
landspreading of sludge.
II. LAMDFILLING
A. Index o£ Groundwater Concentration Increment Resulting from
Landfilled Sludge (Index 1)
1. Explanation - Calculates groundwater contamination which
could occur in a potable aquifer in the landfill vicin-
ity. Uses U.S. EPA Exposure Assessment Group (EAG)
model, "Rapid Assessment of Potential Groundwater Contam-
ination Under Emergency Response Conditions" (U.S. EPA,
1983b). Treats landfill leachate as a pulse input, i.e.,
the application of a constant source concentration for a
short time period relative to the time frame of the anal-
ysis. In order to predict pollutant movement in soils
and groundwater, parameters regarding transport and fate,
and boundary or source conditions are evaluated. Trans-
port parameters include the interstitial pore water
velocity and dispersion coefficient. Pollutant fate
parameters include the degradation/decay coefficient and
retardation factor. Retardation is primarily a function
of the adsorption process, which is characterized by a
linear, equilibrium partition coefficient representing
the ratio of adsorbed and solution pollutant concentra-
tions. This partition coefficient, along with soil bulk
density and volumetric water content, are used to calcu-
late the retardation factor. A computer program (in
FORTRAN) was developed to facilitate computation of the
analytical solution. The program predicts pollutant con-
centration as a function of trime and location in both the
unsaturated and saturated zone. Separate computations
and parameter estimates are required for each zone. The
prediction requires evaluations of four dimensionless
input values and subsequent evaluation of the result,
through use of the computer program.
3-19
-------
2. As sumptions/Limitations - Conservatively assumes that the
pollutant is 100 percent mobilized in the leachate and
that all leachate leaks out of the landfill in a finite
period and undiluted by precipitation. Assumes that all
soil and aquifer properties are homogeneous and isotropic
throughout each zone; steady, uniform flow occurs only in
the vertical direction throughout the unsaturated zone,
and only in the horizontal (longitudinal) plane in the
saturated zone; pollutant movement is considered only in
direction of groundwater flow for the saturated zone; all
pollutants exist in concentrations that do not signifi-
cantly affect water movement; the pollutant source is a
pulse input; no dilution of the plume occurs by recharge
from outside the source area; the leachate is undiluted
by aquifer flow within the saturated zone; concentration
in the saturated zone is attenuated only by dispersion.
3. Data Used and Rationale
a. Unsaturated zone
i. Soil type and characteristics
(a) Soil type
Typical Sandy
Worst Sandy loam
These two soil types were used by Gerritse et
al. (1982) to measure partitioning of elements
between soil and a sewage sludge solution
phase. They are used here since these parti-
tioning measurements (i.e., Kj values) are con-
sidered the best available for analysis of
metal transport from landfilled sludge. The
same soil types are also used for nonmetals for
convenience and consistency of analysis.
(b) Dry bulk density
Typical 1.925 g/mL
Worst 1.53 g/mL
Bulk 'density is the dry mass per unit volume of
the medium (soil), i.e., neglecting the mass of
the water (Camp Dresser and McKee, Inc. (CDM),
1984).
(c) Volumetric water content (9)
Typical 0.133 (uhitless)
Worst 0.195 (unitless)
3-20
-------
The volumetric water content is the volume of
water in a given volume of media, usually
expressed as a fraction or percent. It depends
on properties of the media and the water flux
estimated by infiltration or net recharge. The
volumetric water content is used in calculating
the water movement through the unsaturated zone
(pore water velocity) and the retardation
coefficient. Values obtained from CDM, 1984.
ii. Sice parameters
(a) Landfill leaching time (LT) = 5 years
Sikora et al. (1982) monitored several
landfills throughout the United States and
estimated time of landfill leaching to be 4 or
5 years. Other types of landfills may leach
for longer periods of time; however, the use of
a value for entrenchment sites is conservative
because it results in a higher Leachate
generation rate.
(b) Leachate generation rate (Q)
Typical 0.8 m/year
Worst 1.6 m/year
It is conservatively assumed that sludge
leachate enters the unsaturated zone undiluted
by precipitation or other recharge, that the
total volume of liquid in the sludge leaches
. out of the landfill, and that leaching is
complete in 5 years. Landfilled sludge is
assumed to be 20 percent solids by volume, and
depth of sludge in the landfill is 5 m in the
typical case and 10 m in the worst case. Thus,
the initial depth of liquid is 4 and 8 m, and
average yearly leachate generation is 0.8 and
1.6 m, respectively.
(c) Depth to groundwater (h)
Typical 5 m
Worst 0 m
Eight landfills were monitored throughout the
United States and depths to groundwater below
them were listed. A typical depth of ground-
water of 5 m was observed (U.S. EPA, 1977).
For the worst case, a. value of 0 m is used to
represent the situation where the bottom of the
landfill is occasionally or regularly below the
water table. The depth to groundwacer must be
3-21
-------
estimated in order to evaluate the likelihood
that pollutants moving through the unsaturated
soil will reach the groundwater.
(d) Dispersivity coefficient (a)
Typical 0.5 m
Worst Not applicable
The dispersion process is exceedingly complex
and difficult to quantify, especially for the
unsaturated zone. It is sometimes ignored in
the unsaturated zone, with the reasoning that
pore water velocities are usually large enough
so that pollutant transport by convection,
i.e., water movement, is paramount. As a rule
of thumb, dispersivity may be set equal to
10 percent of the distance measurement of the
analysis (Gelhar and Axness, 1981). Thus,
based on depth to groundwater listed above, the
value for the typical case is 0.5 and that for
the worst case does not apply since leachate
moves directly to the unsaturated zone.
iii. Chemical-specific parameters
(a) Sludge concentration of pollutant (SC)
Typical 9.8 mg/kg DW
Worst 40 mg/kg DW
See Section 3, p." 3-1.
(b) Degradation rate (u) = 0 day'1
The degradation rate in the unsaturated' zone is
assumed to be zero for all inorganic chemicals
(c) Soil sorption coefficient
Typical 43.4 mL/g
Worst 8.58 rnL/g
K
-------
b. Saturated zone
i. Soil type and characteristics
(a) Soil type
Typical Silty sand'
Worst Sand
A silty sand having the values of aquifer por-
osity and hydraulic conductivity defined below
represents a typical aquifer material. A more
conductive medium such as sand transports the
plume more readily and with less dispersion and
therefore represents a reasonable worst case.
(b) Aquifer porosity (0)-
Typical 0.44 (unitless)
Worst 0.389 (unitless)
Porosity is that portion of the total volume of
soil that is made up of voids (air) and water.
Values corresponding to the above soil types
are from Pettyjohn et al. (1982) as presented
in U.S. EPA (1983b).'
(c) Hydraulic conductivity of the aquifer (K)
Typical 0.86 m/day
Worst 4.04 m/day
The hydraulic conductivity (or permeability) of
the aquifer is needed to estimate flow velocity
based on Darcy's Equation. It is a measure of
the volume of liquid that can flow through a
unit area or media with time; values can range
over nine orders of magnitude depending on the
nature of the media. Heterogenous conditions
produce large spatial variation in hydraulic
conductivity, making estimation of a single
effective value extremely difficult. Values
used are from Freeze and Cherry (1979) as
presented in.U.S. EPA (1983b).
ii. Site parameters
(a) Average hydraulic gradient between landfill and
well (i)
Typical 0.001 (unitless)
Worst 0.02 (unitless)
3-23
-------
The hydraulic gradient is the slope of the
water table in an unconf ined aquifer, or the
piezometric surface for a confined aquifer.
The hydraulic gradient must be known to
determine the magnitude and direction of
groundwater flow. As gradient increases, dis-
persion is reduced. Estimates of typical and
high gradient values were provided by Donigian
(1985).
(b) Distance from well to landfill (AZ)
Typical 100 m
Worst 50 ra
This distance is the distance between a
landfill and any functioning public or private
water supply or livestock water supply. !
(c) Dispersivity coefficient (a)
Typical 10 m
Worst 5 m
These values are 10 percent of the distance
from well to landfill (A&), which is 100 and
50 m, respectively, for typical and worst
conditions.
(d) Minimum thickness of saturated zone (B) = 2 m
The minimum aquifer thickness represents the
assumed thickness due to preexisting flow;
i.e., in the absence of leachate. It is termed
the "minimum thickness because in the vicinity
of the site , it may be increased by leachate
infiltration from the site. A value of 2 m
represents a worst case assumption that
preexisting flow is very limited and therefore
dilution of the plume entering the saturated
zone is negligible.
(e) Width of landfill (W) = 112.8 m
The landfill is arbitrarily assumed to be
circular with an area of 10,000 m^.
iii. Chemical-specific parameters
(a) Degradation rate (ji) = 0 day~^-
Degradation is assumed not to occur in the
saturated zone.
3-24
-------
(b) Background concentration of pollutant in
groundwater (BC) = 10 ]ig/L
Adequate groundwater data is not available.
Friberg et al. (1975) reported groundwater val-
ues in a mining area in Colorado (25,000 yg/L)
and Hem (1970) reported values for an area in
the USSR (3 Ug/L). The concentration of Mo
(10 Ug/L) in typical U.S. surface waters is
considered to be the most analogous to
groundwater values (NAS, 1977). (See
Section 4, pp. 4-2 and 4-3.)
(c) Soil sorption coefficient (K^) = 0 mL/g
Adsorption is assumed to be zero in Che
saturated zone.
4. Index Values - See Table 3-1.
5. Value Interpretation - Value equals factor by which
expected groundwater concentration of pollutant at well
exceeds the background concentration (a value of 2.0
indicates the concentration is doubled, a value of 1.0
indicates no change).
6. Preliminary Conclusion - Landfilled sludge may slightly
increase the groundwater concentration of Mo above back-
ground concentrations; this increase may be large at
disposal sites with all worst-case conditions.
B. Index of Human Toxicity Resulting from Groundwater
Contamination (Index 2)
1. Explanation - Calculates human exposure which could
result from groundwater contamination. Compares exposure
with acceptable daily intake (ADI) of pollutant.
2. Assumptions/Limitations - Assumes long-term exposure to
maximum concentration at well at a rate of 2 L/day.
3. Data Used .and Rationale '
a. Index of groundwater concentration increment result-
ing from landfilled sludge (Index 1)
See Section 3, p. 3-27.
b. Background concentration of pollutant in groundwater
(BC) = 10 ug/L
See Section 3, p. 3-25.
3-25
-------
c. Average human consumption of drinking water (AC) =
2 L/day
The value of 2 L/day is a standard value used by
U.S. EPA in most risk assessment studies.
d. Average daily human dietary intake of pollutant (DI)
= 335 Ug/day
See Section 3, p. 3-12.
e. Acceptable daily intake of pollutant (ADI) =
3712 Ug/day
See Section 3, p. 3-12.
4. Index 2 Values - See Table 3-1.
5. Value Interpretation - Value equals factor by which pol-
lutant intake exceeds ADI. Value >1 indicates a possible
human health threat. Comparison with the null index
value indicates the degree to which any hazard is due to
landfill disposal, as opposed co preexisting dietary
sources.
6. Preliminary Conclusion - The disposal of sludge in land-
fills is not expected to pose a hazard to human health
due to Mo in groundwater.
III. INCINERATION
Based on the recommendations of the experts at Che OWRS meetings
(April-May, 1984), an assessment of this reuse/disposal option is
not being conducted at thi's time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
IV. OCEAN DISPOSAL
Based on the recommendations of the experts at the OWRS meetings
(April-May, 1984), an assessment of this reuse/disposal option is
not being conducted at this time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
3-26
-------
NJ
Site Characteristics 1
Sludge concentration T
Unsaturated Zone
Soil type and charac- T
teristics^
Site parameters6 T
Saturated Zone
Soil type and charac- T
teristics^
Site parameters^ T
Index 1 Value 1.0
i
Index 2 Value 0.090
Condition of Analysisa»b»c
23456
W T T T T
T W NA T T
T T W T T
T T T W T
T T T T W
1.1 1.0 1.0 1.1 2.0
0.091 0.090 0.090 0.091 0.096
7 8
W N
NA N
U N
W N
W N
24 0
0.22 0.090
aT = Typical values used; W = worst-case values used; N = null condition, where no landfill exists, used as
basis for comparison; NA = not applicable for this condition.
blndex values for combinations other than those shown may be calculated using the formulae in the Appendix.
cSee Table A-l in Appendix for parameter values used.
^Dry bulk density (Pdry) and volumetric water content (6).
eLeachate generation rate (Q), depth to groundwater (h), and dispersivity coefficient (a).
^Aquifer porosity (0) and hydraulic conductivity of the aquifer (K).
^Hydraulic gradient (i), distance from well to landfill (All), and dispersivity coefficient (a).
-------
SECTION 4
PRELIMINARY DATA PROFILE FOR MOLYBDENUM IN MUNICIPAL SEWAGE SLUDGE
I. OCCURRENCE
A. Sludge
1. Frequency of Detection
Data not immediately available.
2. Concentration
Mean, 28 Ug/g, Median 30 ug/g
•Range 5 to 39 Ug/g
40 Ug/g (DW) anaerobic sludge
3.6 Ug/g (DW)
2 to 30 Ug/g (DW), with 35 of 42
samples <10 Ug/g
Trace to 1,000 ug/g
Range = 1.2 to 40.0 ug/g
Mean = 14.25 Ug/g
Median =9.8 Ug/g
95th percentile = 40 Ug/g in sludges
of 16 U.S. cities
B. Soil - Unpolluted
1. Frequency of Detection
Data not immediately available.
2. Concentration
"Normal" 2 ug/g
Range 0.2 to 5 ug/g
Sommers, 1976
in Council for
Agricultural
Science and
Technology
(CAST), 1976
(p. 34)
Baxter et al.,
1983a (p. 313)
Furr et al.,
1976a (p. 87)
Berrow and
Webber, 1972 in
Friberg et al.,
1975 (p. 17)
Page, 1974
(p. 15)
»
Furr et al.,
1976b
Allaway, 1968
(p. 242)
4-1
-------
"Typical" 4 kg/ha
Range 0.4 to 10 kg/ha
C. Water - Unpolluted
1. Frequency of Detection
32.7% detection in American rivers
516 of 1577 surface waters
2. Concentration
a. Freshwater
<10 Ug/L median concentration
1.4 ug/L median of 100 largest U.S.
cities
5 to 30 mg/L in American rivers
0.068 mg/L mean, 0.002 to 1.5 mg/L
range observations in 516 out of
1,577 (32.7 percent detection)
U.S. streams
10 Wg/L in typical U.S. surface
waters
b. Seawater
10 Ug/L
0.01 mg/L
c. Drinking Water
1.4 Ug/L median from 100 U.S. cities
0.01 mg/L upper limits for irriga-
tion water
Page, 1974
(p. 71)
Page, 1974
(p. 25)
Friberg et al.,
1975 (p. 13)
Turekian and
Scott, 1967 in
Friberg et al. ,
1977 (p. 347)
Page, 1974
(p. 25)
HAS, 1977
Friberg et al.,
1975 (p. 13)
Hem, 1970
(p. ID
Friberg et al.,
1975 (p. 13)
U.S. Federal
Water Pollution
Control Admini-
stration, 1968
in Hem, 1970
(p. 200)
4-2
-------
d* Groundwater
2SOOO Ug/L in groundwater in mining
areas in Colorado
3 Ug/L in groundwater in USSR
D. Air
1. Frequency of Detection
Data not immediately available.
2. Concentration
a. Urban
10 to 30
b. Rural
0.1 to 3.2 ng/ra2
E. Pood
1. Total Average Intake
335 Ug/day in average diet;
210 to 460 ug/day, range
110, 210, and 460 ug daily intake for
3 hospitalized persons studied
115 to 245 ug average daily intake for
10 days for 4 hospitalized persons
2. Concentration
73 ppb (WW) Mo in milk, average
18 to 120 range
30 to 160 (WW) ppb in potatoes
Friberg et al.,
1975 (p. 14)
Hem, 1970
(p. 200)
Schroeder, 1970
in Friberg, 1977
(p. 347)
Schroeder, 1970
in Friberg, 1977
(p. 347)
Schroeder, 1970
in Friberg et
al., 1975
(p. 18)
Friberg et al.,
1975 (p. 19)
Wester, 1974 in
Friberg et al.,
1975 (p. 19)
Archibald, 1951
in Friberg et
al., 1975
(p. 18)
Friberg et al.,
1975 (p. 24)
4-3
-------
20 ppb (WW) in cabbage
310 to 4,800 ppb in peas (WW)
640 to 5,870 ppb in wheat (WW)
II. HUMAN EFFECTS
A. Ingestion
1. Carcinogenicity
Data not immediately available.
2. Chronic Toxicity
a. ADI
Human dietary concentrations exceed-
ing 4 mg/kg DW per day are cause for
concern.
b. Effects
Excess of Mo in diet leads to excess
uric acid formation and gout-like
illnesses.
3. Absorption Factor
25 to 752
4. Existing Regulations
Present drinking water standards contain
no limit for Mo.
B. Inhalation
1. Carcinogenicity
Data not immediately available.
2. Chronic Toxicity
a. Inhalation Threshold or MPIH
See below, "Existing Regulations."
b. Effects
Exposure for long periods (4 years or
more) to metallic Mo has been known
to cause pneumoconiosis.
Schroeder, 1970
in Friberg et
al., 1975
(p. 24, 25)
Suttle, 1973 in
Jarrell, 1980
(p. 22)
Friberg et al.,
1977 (p. 352)
Friberg et al.,
1975 (p. 31)
Hem, 1970
(p. 200)
Friberg et al.,
1975 (p. 63)
4-4
-------
Friberg et al.,
1975 (p. 27)
ACGIH, 1983
3. Absorption Factor
No data available on absorption after
inhalation
4. Existing Regulations
Soluble compounds = 5 mg/m^ Time
Weighted Average (TWA)
Insoluble compounds = 10 mg/nP TWA
III. PLANT EFFECTS
A. Phytotoxicity
1. Soil concentration causing phytotoxicity
See Table 4-1.
HC1 and hot water, extractable Mo in soils Rohde, 1962 in
Created with sewage sludge, and effects Page, 1974
on plants (p. 30)
Molybdenum Concentration (ug/g) and
Plant Effect
Berlin. Paris
HC1
Hot Water
Healthy
1.7
0.25
Unhealthy
2.6
0.159
Healthy
2.3
1.4
Unhealthy
3.1
1.5
0.12 kg/ha of M<3 added to soil from
sewage sludge; no adverse effect on corn
Hinesly et-al.,
1972 in Page,
1974 (p. 41)
Mo concentration in surface 20 cm of soil Anderson and
following application of 84" metric tons Nilsson, 1972
of sewage sludge over a period of 12 in Page, 1974
years (ug/g): (p. 59)
Control Soil Treated Soil Total Applied
0.53 0.68 0.23
For sewage sludge containing 5 ppm Mo,
800 metric tons of sludge applied to a
hectare of soil would be required to
produce Mo concentration levels equal to
those observed naturally in soil at 4 ppm.
Page, 1974
(p. 74)
4-5
-------
2000 to 4000 metric tons/hectare would
be required to produce Mo soil concentra-
tion in excess of the natural range
(>10 ppm)
Concentration of Mo in all sludges is
such that yield reductions caused by
toxicities of Mo in sludge-amended soils
is unlikely.
2. Tissue concentration causing phytotoxicity
Mo is required in very small amounts in
plants. It does not appear to be very
toxic to plants, even at levels of a few
hundred ppm in plant tissue.
Mo toxicity to crops is not a problem
since plant levels of a few hundred ppm
Mo are not toxic.
Uptake
See Table 4-2.
0.1 to 3 ppm (DW) range of Mo concentration
in normal herbage
Page, 1974
(p. 74)
Page, 1974
(p. 77)
1 to 100 ppm DW
IV. DOMESTIC ANIMAL AND WILDLIFE EFFECTS
A. Toxicity
See Table 4-3. -
Required at <0.1; moderate to high toxicicy
depending on Cu concentration
31
5 ppm Mo coupled with <4 ppm Cu toxic to
ruminants
10 to 20 ppm Mo toxic to ruminants
Sludge with 39 ppm Mo applied at a rate of
60 metric tons/hectare would result in
application of 2.3 kg of Mo. This addition
would not pose a threat to the health of
grazing animals.
Repeated applications of sludge with high Mo
concentration over a long period of time
might cause animal health problems,
CAST, 1976
(p. 33)
Baxter et al.,
1983b (p. 14)'
Underwood, 1977
in MAS, 1980
(p. 330)
Allaway, 1968
(p. 242)
Allaway, 1968
(p. 242)
Allaway, 1968
(p. 259)
CAST, 1976
(p. 34)
Hornick et al.,
1976 in CAST,
1976 (p. 34)
4-6
-------
especially on soils of high pH which are not
subject Co leaching.
It is doubtful that Mo in sludge would CAST, 1976
present a serious hazard to the health of (p. 34)
grazing animals except where forages from
sites treated with sludge high in Mo form a
major part of the animal diet.
Feed and food plants can grow at normal or Page, 1974
near normal rates and still contain suffi- (p. 77)
cient Mo to cause either direct toxicity or
metabolic imbalance in animals that consume
these crops.
Depending on the Mo concentration in sewage Page, 1974
sludge, it is possible that soils would (p. 78)
become enriched to the extent that plants
would absorb quantities of Mo sufficient to
be toxic to animals.
Baxter, et al.,
1983b (p. 14)
Because sewage sludges contain Low concentra-
tions of Mo that are accompanied with Cu and
phosphorus (P), there is little concern that
Mo in sludges constitute a hazard to grazing
animals.
Ratio of Cu:Mo <2:1 in forage causes Mo
poisoning in cattle.
>6 ppm Mo with 8 to 11 ppm Cu (normal range
for Cu) toxic to cattle
1 to 2 ppm Mo with 8 to 11 ppm Cu and high
304 toxic to cattle
High levels of Cu in forage (13-16 ppm) will
protect cattle against Mo levels as high as
150 ppm.
ff. Uptake
1. Normal range of tissue concentrations
2 to 4 ppm (DW) in liver of animals on MAS, 1980
normal diet (p. 334)
See Table 4-4.
Milcimore and
Mason, 1971 in
Buck., 1978
(p. 497)
Buck, 1978
(p. 498)
Underwood, 1977
in Buck, 1978
(p. 498)
4-7
-------
Tissue concentration where intake is elevated
Mo concentration (ppm DW) in tissues of
cattle exposed to sludge via direct
ingestion from land application compared
to control animals.
Baxter et al.,
1983c (p. 318)
Tissue
Control
Exposed
Kidney
Liver
Bone
Muscle
1.7 + 0.5
3.2 + 0.3
0.15 + 0.02
<0.03
1.6 * 0.4
2.7 + 0.5
0.35 + 0.27
<0.05
42.3 ppra (DW) in kidney, 95 ppm (DW) in
spleen, and 10.4 ppm (DW) in liver of
cows fed 53 mg/kg diet
46 ppm (WW) in kidney and 20 ppm (WW) in
liver of guinea pigs, 4 hours after
administration of 50 mg of MoC>3
7 ppm (WW) in kidney and 3 ppm (WW) in
liver 48 hours after administration
Mo concentration in livers of rats fed
20 ppb and 200 ppb Mo for 3 generations
(ppra DW):
Huber et al.,
1971 in Friberg
et al., 1975
(p. 36)
Fairhill et al.,
1945 in Friberg
et al., 1975
(p. 43)
Higgins et al.,
1956 in Friberg
et al., 1975
(p. 50)
Feed Concentration Liver Concentracion
20 ppb
200 ppb
1.89 + 0.15 ppm
2.24 + 0.19 ppm
Mo concentration in tissues of chicks fed Higgins et al . ,
20 ppb and 200 ppb Mo (ppm DW):
Feed Cone.
20 ppb
200 ppb
Control*
Liver Cone.
2.52
3.35
3.56
Kidney Cone.
3.09
3.48
4.44
*250 ppb from slope line
V. AQUATIC LIFE EFFECTS
Data not immediately available.
1956 in Friberg
et al., 1975
(p. 60)
4-8
-------
VI. SOIL BIOTA EFFECTS
Data not immediately available.
VII. PHYSIOCHEMICAL DATA FOR ESTIMATING PATE AND TRANSPORT
Mo molecular wt: 95.95 Hodgman et al.,
Specific gravity: 10.2 1960
Melting point (°C): 2620 ± 10
Solubility
cold water: insoluble
hot water: insoluble
MoS2 (molybdenite) molecular wt: 160.08 Hodgman, et al.,
Specific gravity: 4.81 1960
Melting point C°C): 1185
Solubility
cold water: insoluble
hot water: insoluble
Distribution (Kjj) (mL/g) Gerritse et al.,
Sandy soil 1982
mean: 43.4
range: 18.9 - 100
Sandy loam soil
mean: 8.58
range: 1.5 - 48.9
4-9
-------
TABLE 4-1. PHYTOTOXIcm OF MOLYBDENUM
Plant/Tissue
Corn/grain
Rye/grass
Rye/grass
Rye/grass
Rye/grass
Forage crops
Most plants
Most plants
Most plants
Chemical
Form Appl led
(study type) Soil pll
Sludge (field/ NUa
anaerobicall y
digested)
Sludge (field/ NU
liquid sludge)
Sludge NU
Sludge NH
Sludge NH
Sludge (field/ NU
anaerobic and
aerobic)
Naturally NU
occurring
Naturally NU
occurring
Naturally NU
occurring
Control Tissue Soil
Concentration Concentration
(pg/g DW) (pg/g DW)
'NR NR
NR NU
NU 0.53
NH 4.0
NH 10
NU 1.25-1.90
<0.1 NH
1-100 NH
MOO NU
Application
Bate
(kg/ha)
0.12
3.2
0.23 pg/g
0.5
1.25-2.55
NR
NR
NR
NH
Experimental
Tissue
Concentration
(Mg/g DW) Effects
NR No adverse effect
NR No adverse effect
NU NU
NR NH
NU NR
NU Unaffected
NH Required
NH Normal
NU Low toxicity
References
Page, 1974
Page, 1974
Page, 1974
Page, 1974
Page, 1974
Baxter et al . ,
1983a
Allauay, 1968
a NU = Not reported.
-------
TABLE 4-2. UPTAKE OP MOLYBDENUM BV PLANTS
Plant/Tissue
Fodder rape
bean/leaf
Tomato/leaf
liar ley/ leaf
Leeks
Beet/routs
Potato/roots
Carrot/roots
Chemical
form Applied
(Study type)
Sludge
Saturation extracts
of sludge (pot)
Saturation extracts
of sludge (pot)
Saturation extracts
of sludge (pot)
Sludge (field)
Sludge (field)
Sludge (field)
Sludge (field)
Soil pit
NHb
NU
NR
NU
NU
Nil
NU
NU
Application Uate
(kg/ha)
0.7B
NU
NU
NR
12. 3C
12. 3C
12. 3C
12. 3C
Control Tissue
Concentration
(tig/g DU)
1.1
2.4
2.9
5.0
0.50
0.10
0.40
0.12
Uptake
Slope"
0.769
NR
MR
NU
0.0484
0.0121
-0.0105
No slope
References
Page, 1974
Bradford
et al., 1975
Page, 1974
a Slope - y/x: y = M8/8 plant tissue UW; x = kg/ha applied.
b NK = Mot reported.
c Estimated from average Mo concentration in sludge and sludge application rate (66 mt/ha/19 years).
-------
TABLE 4-3. TOXlCm Of MOLYbDENUM TO DOMESTIC ANIMALS AND WILDLIFE
Species (N)a
Cattle (50)
Ca t u 1 e
Cattle
Ca 1 1 1 e
Cattle (B)
i
10 Cattle (It)
Cattle (25)
CattU (32)
Cattle (1)
Sheep (2)
Sheep U)
Peed
Chemical Form Concentration
fed (|Jg/6 UU)
Natural forage NKb
High Ho pasture Nit
High Mo pasture NK
High Ko pasture HH
Molybdate Mr
Molybdate Mil
MoOi MR
MoOj NK
NaHoO^ NK
(Ntlj^MoOii Nit
Md2MoO^ MB
Wa l e r
Concent ration
Ug/L)
NH
NK
Nit
NK
NH
NU
NH
Nit
NU
NU
KH
Daily Intake
(rag/kg DU)
Up to 6.2 ppra
25.6 ppoi
100-201) ppm
400 ppin
53-100 ppm
IV 3-300 ppm
as ppu
100 ppra
2.34 g/d
10 mg/d
50 mg/d
Duration
of Study
5 to 12 months
23 days
23 days
23 days
Up to 6 months
Up to 6 months
11 days
1 year
7 months
34 days
IB days
Effects References
Abnormal distal metacarpal HAS, 19BO
and tarsal growth plates
Diarrhea; emaciation;
anemia achrouiot richia i death
Transient increase in Ho
level in milk
Increased milk Ma and toxic
effects
Mo effect on liver, blood,
or milk Mo levels
Diarrhea; inanition;
increased milk Cu; decreased
I i ve r Cu
Diarrhea and tocomoior
disturbances within 5 days
Actiromatrichia; diarrhea;
reduced gains
Diarrhea; acromot richia;
201 weight loas
Increased blood Ho to 2 ppra
Rumen SO^ increased from
1,576 co 805 ppm
-------
TABLE 4-3. (continued)
Chemical Form
Species (N)a Fed
Mule deer Na2Mo04
Na2MuOA
Na2MoO<
Swine (6) Na^MoSO^
Swine (208) Wa2Mu304
Swine Na2MuS04
Swine Na2MoO/i -2ll20
Chicken (30) Na2Mo04
Chicken (20) Na2MoO^
Na2Mo04
Chicken (4) Ma2Mo04
Na.MoO,,
Turkey (23) NajMuO^
Horse Pasture
Feed
Concentration
pm S04
50 ppm with
500 ppm Cu
1 ,000 ppm
1,500 ppra with
\7.8 ppm Cu
and 0.42 S
200-300 ppm
500 ppm-
4,000 ppm
5,000 ppm
1,000 ppm
300 ppm
5-22 ppra
Duration
of Study
27 days
27 days
27 days
9 weeks
9 weeks
9 weeks
61 days
90 days
69 days
4 weeks
4 weeks
4 weeks
21 days
21 days
4 weeks
Daily
Effects References
No clinical effect noted HAS, 1980
Diarrhea
Anorexia
No adverse effect
Slight decrease in rate of
gain} increase in liver Cu
Decreased rate of gain
No prevention of Cu
toxicosis
No adverse effect
Depressed growth with time
Enhanced plasma Cu clearance
Slight growth reduction
Decreased growth
Decreased growth and anemia
Weight loss and reduced
hatcliabil i ty
Decreased egg production
Growth rate reduced 25Z; no
diarrhea or anemia
Associated with rachitis
-------
TAULk 4-3. (continued)
Chemical Form
Species (N}a Fed
Rabbit (31) Na^HuO^ • 2II20
Uabbil Na2Ho04-2H20
Habl.ll Na2MoO^- 211^,0
Hat NaMoO^
NaMoO^
Rat NaMoO;,
Ual Na2Mo04 -21120
Feed
Concentration
(Mg/B DM)
NR
NU
NK
UK
NH
NU
NU
NU
NU
NU
NU
Water
Concentration
(mg/L)
NR
Nil
NK
NH
NH
NH
NU
NR
NR
NR
Nit
Daily Intake
(rag/kg DU)
140 piira with
16.4 ppm Cu
J^iOO ppm
-r|000 ppm
2000 ppm
4000 ppm with
200 ppm Cu
10-100 ppm in
Cu deficient
diet
10 ppm uith
3 ppm Cu
75 ppm
100 ppm
SOU ppm with
uitti 6 ppm Cu
1000 ppm with
Duration
of Study
4 months
4 weeks
4 weeks
4 weeka
4 months
4 weeks
4 weeks
5 weeks
S weeks
4 weeks
4 weeks
Effects References
Ho adverse effect HAS, 1980
No adverse effect
Anorexia;
weight loss;
dermatosis; reduced bone
phosphorous
Splayed forelegs and death.
No adverse effect
Decreased growth; liver Cu;
and hemoglobin levels.
No adverse effect
Increased liver Cu and Mo
Reduced growth (preventable
with S04)
Reduced ceruloplasmin
Reduced ceruloplasmin
1 ppm Cu and
20 or 60 Cu IV
-------
TAUI.li 4-3. (continued)
Species (N)a
Rat (6)
Hat (10)
Itat (10)
Hat
Rat (48)
Guinea |>ig
Cattle
Sheep
Pig
Feed
Chemical Form Concentration
Fed (Mg/g DM)
NaMo04 Nil
Nit
NaHo04 NR
Nit
Na2HoO^-2ll20 NU
Nit
NU
Na2MoO^-2ll2O NR
NR
Nit
feed or forages 5-6
feed or forages 10-12
feed 1000
Water
Concentration
Ug/L)
NU
NU
NU
NR
NR
NU
NR
NR
NH
NR
NR
NR
NR
Daily Intake
(rag /kg DM)
800 ppm with
1 .22 methionine
800 ppm with
0.6% me Chi one
plua 300 ppra Cu
BOO ppm with
15.6 ppm Cu
BOO ppm with
15.6 ppm Cu
plua 0.29Z
304
14.24 mg/d
14.24 mg/d
plua 4 ing Cu
500-5000 ppm
400-1200 ppm
4000 ppm
100 ppm
NR
NR
NR
Dural ion
of Study
6 weeks
41 days
41 days
3 weeks
3 weeks
4 weeks
7 weeks
7 weeks
6 weeks
NU
NU
3 months
Effects
Reduced growth spared by
methionine
Reduced toxicosis signs
Increased liver Cu
No adverse effect
Increased blood and liver
CuJ increased sp. gr. of
blood
No adverse effect
Reduced growth at 500 ppm
Mo and above; no diarrhea
Rough hair; reduced growth;
increased tissue Mo
Rough hair; reduced growth;
increased tissue Mo
Increased liver Mo; no other
effect
Poisoned
Poisoned
No ill effects
References
NAS, 19BO
Buck, 1978
Buck, 1978
Buck, 1978
-------
TAULK 4-3. (continued)
Species (N)a
Rats
Rat (24)
Hat (8)
(10)
(10)
•0- (8-8)
I
ON Rat (10)
(10)
(10)
(10)
(10)
Rat (fl)
-------
TABLE 4-4. UPTAKE OP MOLYBDENUM BY DOMESTIC ANIMALS AND WILDLIFE
^
1
I-J
Chemical
Species Form Fed
Guinea pigs Swiss ctiard grown
on sludge field
Hange
of Feed
Concentrationa
(pg/g DM)
1.1-2.8
Tissue
Analyzed
1 iver
kidney
muscle
Control Tissue
Concentration
(Mg/g DU)*
1.5
0.6
0.]
Uptake" »b
Slope
1.028
0.2533
0.3225
References
Furr et al. , 1976a
a When tissue values were reported as wet weight, unless otherwise indicated a moisture content of 77Z was assumed for kidney, 701 for liver and 12Z
tor muscle.
b Uptake slope = y/x: y = yg/g tissue UUj * = (Jg/g feed DM.
-------
SECTION 5
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and Molybdenum and Copper Concentrations in Ruminant Feeds. Can.
J. Ani. Sci. 51-193-200. (As cited in Buck, 1978.)
National Academy of Sciences. 1977. Drinking Water and Health.
Committee on Safe Drinking Water of the National Research Council,
National Research Council, Washington, D.C.
National Academy of Sciences. 1980. Mineral Tolerances of Domestic
Animals. National Review Council Subcommittee on Mineral Toxicity
in Animals, National Academy of Sciences, Washington, D.C.
Page, A. L. 1974. Fate and Effects of Trace Elements in Sewage Sludge
When Applied to Agricultural Lands. EPA-670/2-74-005. U.S.
Environmental Protection Agency, Cincinnati, OH.
Pennington,.J. A. T. 1983. Revision of the Total Diet Study Food Lists
and Diets. J. Am. Diet. Assoc. 82:166-173.
Pettyjohn, W. A., D. C. Kent, T. A. Prickett, H. E. LeGrand, and F. E.
Witz. 1982. Methods for the Prediction of Leachate Plume
Migration and Mixing. U.S. EPA Municipal Environmental Research
Laboratory, Cincinnati, OH.
5-3
-------
Rohde, G. 1962. The Effects of Trace Elements on the Exhaustion of
Sewage Irrigated Land. Inst. Sew. Purifi., London, Journal and
Proceedings. (As cited in Page, 1974.)
Ryan, J. A., H. R. Pahren, and J. B. Lucas. 1982. Controlling Cadmium
in the Human Food Chain: A Review and Rationale Based on Health
Effects. Environ. Res. 28:251-302.
Schroeder, J. A. 1970. A Sensible Look at Air Pollution by Metals.
Arch. Env. Health, 21:798-806. (As cited in Friberg, 1977.)
Sikora, L. J., W. D. Burge, and J. E. Jones. 1982. Monitoring of a
Municipal Sludge Entrenchment Site. J. Environ. Qual. 2(2):321-
325,
Thornton, I., and P. Abrams. 1983. Soil Ingestion - A Major Pathway of
Heavy Metals into Livestock Grazing Contaminated Land. Sci. Total
Environ. 28:287-294.
Turekian, K. K., and M. R. Scott. 1967. Concentrations of Cr, Ag, Mo,
Ni, Co, and Mn in Suspended Materials in Streams. Environ. Sci.
and Techn. 1:940-942. (As cited in Friberg et al., 1977.)
Underwood, E. J. 1977. Trace Elements in Human and Animal Nutrition.
4th edition. Academic Press. (As cited in MAS, 1980, and Buck.,
1978.)
U.S. Department of Agriculture. 1975. Composition of Foods.
Agricultural Handbook No. 8.
U.S. Environmental Protection Agency. 1977. Environmental Assessment
of Subsurface Disposal of Municipal Wastewater Sludge: Interim
Report. EPA/530/SW-547. Municipal Environmental Research
Laboratory, Cincinnati, OH.
.U.S. Environmental Protection Agency. 1983a. Assessment of Human
Exposure to Arsenic: Tacoma, Washington. Internal Document.
OHEA-E-075-U. Office of Health and Environmental Assessment,
Washington, D.C. July 19.
U.S. Environmental Protection Agency. 1983b. Rapid Assessment of
Potential Groundwater Contamination Under Emergency • Response
Conditions. EPA 600/8-83-030.
U.S. Environmental Protection Agency. 1984. Air Quality Criteria for
Lead. External Review Draft. EPA 600/8-83-028A. Environmental
Criteria and Assessment Office, Research Triangle Park, NC.
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cited in Hem, 1970.)
5-4
-------
Wester, P. 0. 1974. Trace Element Balance in Relation to Variations in
Calcium Intake. Artfaerosclerosis. 20:207-215. (As cited in
Friberg et al., 1975.)
5-5
-------
APPENDIX
PRELIMINARY HAZARD INDEX CALCULATIONS FOR MOLYBDENUM
IN MUNICIPAL SEWAGE SLUDGE
I. LANDSPREADING AND DISTRIBUTION-AND-MARKETING
A. Effect on Soil Concentration of Molybdenum
1. Index of Soil Concentration Increment (Index 1)
a. Formula
T j i (SC x AR) + (BS x MS)
Index L = BS (AR + MS) *~
where :
SC = Sludge concentration of pollutant
(Ug/g DW)
AR = Sludge application rate (mt DW/ha)
BS = Background concentration of pollutant in
soil (ug/g DW)
MS = 2000 mt DW/ha = Assumed mass of soil in
upper 15 cm
b. Sample calculation
(9.8 Ug/g DW x 5 mt/ha) + (2.6 Ug/g DW x 2000 mt/ha)
1.007 = 2000 mt/ha)
Effect on Soil Biota and Predators of Soil Biota
1. Index of Soil 'Biota Toxicity (Index 2)
a. Formula
i x BS
Index 2
where :
II - Index 1 = Index of soil concentration
increment (unitless)
BS = Background concentration of pollutant in
soil (ug/g DW)
TB = Soil - concentration toxic to soil biota
(Ug/g DW)
b. Sample calculation - Values were not calculated due
to lack of data.
A-l
-------
2. Index of Soil Biota Predator Toxicity (Index 3)
a. Formula
- 1}(BS x UB) + BB
where :
IL = Index 1 = Index of soil concentration
increment (unitless)
BS = Background concentration of pollutant in
soil (ug/g DW)
UB = Uptake slope of pollutant in soil biota
(Ug/g tissue DW [ug/g soil DW]'1)
BB = Background concentration in soil biota
(Ug/g DW)
TR = Feed concentration toxic to predator (ug/g
DW)
b. Sample calculation - Values were not calculated due
to lack of data.
C. Effect on Plants and Plant Tissue Concentration
1. Index of Phytotoxicity (Index 4)
a. Formula
Ii x BS
Index 4
where :
!]_ = Index 1 = Index of soil concentration
increment (unitless)
BS = Background concentration of pollutant in
soil (ug/g DW)
TP = Soil concentration toxic to plants (ug/g
DW)
b. Sample calculation
0 0403 = 1-007 * 2.6 Ug/g DW
°'0403 65 Ug/g DW
A-2
-------
2. Index of Plant Concentration Increment Caused by Uptake
(Index 5)
a. Formula
(Ii - 1) x BS
Index 5 = — = - x CO x UP + 1
BP
where :
II - Index 1 = Index of soil concentration
increment (unitless)
BS = Background concentration of pollutant in
soil (ug/g DM)
CO = 2 kg/ha (ug/g)~* = Conversion factor
between soil concentration and application
rate
UP = Uptake slope of pollutant in plant tissue
(Ug/g tissue DW [kg/ha]"1)
BP = Background concentration in plant tissue
(Ug/g DW)
b. Sample calculation
(1.007-1) x 2.6 ug/g DW 2 kg/ha
-
0.769 Ug/g tissue .
X kg/ha
Index of Plant Concentration Increment Permitted by
Phytotoxicity (Index 6)
a. Formula
PP"
Index 6 = —
where:
PP = Maximum plant tissue concentration
associated with phytotoxicity (ug/g DW)
BP = Background concentration in plant tissue
(Ug/g DW)
b. Sample calculation
on QI - 100
90'91 1.1 Ug/g DW
A-3
-------
C. Effect on Herbivorous Animals
1. Index of Animal Toxicity Resulting from Plant Consumption
(Index 7)
a. Formula
15 x BP
Index 7 = _____
where:
15 = Index 5 = Index of plant concentration
increment caused by uptake (unitless)
BP = Background concentration in plant tissue
(Ug/g DW)
TA = Feed concentration toxic to herbivorous
animal (ug/g DW)
b. Sample calculation
n ,,„«.. 1.0251 x 1.1 Ug/g DW
°-2255 = 5 Ug/g DW
2. Index of Animal Toxicity Resulting from Sludge Ingestion
(Index 8)
a. Formula
IfAR-0, 18=^^
IfAR^O, I8=^^
where:
AR = Sludge application rate (mt DW/ha)
SC = Sludge concentration of pollutant
(Ug/g DW)
BS = Background concentration of pollutant in
soil (Ug/g DW)
GS = Fraction of animal diet assumed to be soil
(unitless)
TA = Feed concentration toxic to herbivorous
animal (ug/g DW)
b. Sample calculation
i Ug/g DW x Q.Q5
rf AP - n n n™ -
If AR - 0, 0.026 -
5 ug/g DW
Tf AR ^ 0 0 098 - 9.8 Ug/g DW x 0.05
If AR r 0, 0.098 -
A-4
-------
Effect on Humans
1. Index of Human Toxicity Resulting from Plant Consumption
(Index 9)
a. Formula
[(I5 - 1) BP x DT] + DI
Index 9 = - - -
ADI
where :
15 = Index 5 = Index of plant concentration
increment caused by uptake (unitless)
BP = Background concentration in plant tissue
(Ug/g DW)
DT = Daily human dietary intake of affected
plant tissue (g/day DW)
DI = Average daily human dietary intake of
pollutant (ug/day)
ADI - Acceptable daily intake of pollucant
( Ug/day)
b. Sample calculation (toddler)
f(1.0251 - 1) x Q.5 ug/g DW x 74.5 g/dayl + 112 ug/day
°*030 = 3712 Ug/day
2. Index of Human Toxicity Resulting from Consumption of
Animal Products Derived from Animals Feeding on Plants
(Index 10)
a. Formula
[(Is - 1) BP x UA x DA] + DI
Index 10 =
where:
15 = Index 5 = Index of plane concentration
increment caused by uptake (unitless)
BP = Background concentration in plant tissue
(Ug/g DW)
UA = Uptake slope of pollutant in animal tissue
(Ug/g tissue DW [ug/g feed DW]'1)
DA = Daily human dietary intake of affected
animal tissue (g/day DW)
DI = Average daily human dietary intake of
pollutant (ug/day)
ADI = Acceptable daily intake of pollutant
(Ug/day)
A-5
-------
b. Sample calculation (toddler)
F(l.0251-1) x 1.1 Ug/g DW x 1.028 ug/g tissuefug/g feed]"1 x 0.97 g/day] + 112 Ug/day
|S 3712 Ug/day
3. Index of Human Toxicity Resulting from Consumption of
Animal Products Derived from Animals Ingesting Soil
(Index 11)
a. Formula
_. A0 . _ . .. (BS x GS x UA x DA) •*• PI
If AR = 0, Index 11 = TTT
Tr ,_ , . . . .. (SC x GS x UA x DA) + PI
If AR t 0, Index 11 =
where:
AR = Sludge application rate (mt PW/ha)
BS = Background concentration of pollutanc in
soil (ug/g PW)
SC = Sludge concentration of pollutant
(Ug/g DW)
GS = Fraction of animal diet assumed to be soil
(unitless)
UA = Uptake slope of pollutant in animal tissue
(Ug/g tissue PW [ug/g feed PW"1]
PA = Average daily human dietary intake of
affected animal tissue (g/day PW)
PI = Average daily human dietary intake of
pollutant (Ug/day)
ADI = Acceptable daily intake of pollutanc
(Ug/day)
b. Sample calculation (toddler)
_ (9.8 Ug/g PW x 0.05 x 1.028 Ug/g tissue I" Ug/g feed]"1 x 0.97 g/day PW) + 112 Ug/day
30 " 3712 Ug/day
4. Index of Human Toxicity Resulting from Soil Ingestion
(Index 12)
a. Formula
(II x BS x PS) + PI
Index 12
API
i j - T j 11 (SC x PS) + PI
Pure sludge ingestion: Index 12 = -rrr
where:
Ij_ = Index 1 = Index of soil concentration
increment (unitless)
A-6
-------
SC = Sludge concentration of pollutant
(Ug/g DW)
BS - Background concentration of pollutant in
soil (ug/g DW)
DS = Assumed amount of soil in human diet
(g/day)
DI = Average daily dietary intake of pollutant
(Ug/day)
ADI = Acceptable daily intake of pollutant
( Ug/day)
b. Sample calculation (toddler)
_ .--_ (1.007 x 2.6 ug/g DW x 5 g soil/day) + 112 ug/day
°*0337 = 3712 Ug/day
Pure sludge:
- (9.8 ug/g DW x 5 g soil/day) + 112 ug/dav
- 3?12 ug/day
S. Index of Aggregate Human Toxicity (Index 13)
a. Formula
Index 13 = I9 + I10 + IU * I12 - j
where :
Ig - Index 9 = Index of human toxicity
resulting from plant consumption
(unitless)
= Index 10 = Index of human toxicity
resulting from consumption of animal
products derived from animals feeding on
plants (unitless) *
= Index 11 = Index of human toxicity
resulting from consumption of animal
products derived from animals ingesting
soil (unitless)
= Index 12 = Index of human toxicity
resulting from soil ingestion (unitless)
DI = Average daily dietary intake of
pollutant (ug/day)
ADI = Acceptable daily intake of pollutant
(Ug/day)
b. Sample calculation (toddler)
0.0335 = (0.030 * 0.030 + 0.030 + 0.034) - (
A-7
-------
II. LANDFILLING
A. Procedure
Using Equation 1, several values of C/C0 for the unsaturated
zone are calculated corresponding to increasing values of t
until equilibrium is reached. Assuming a 5-year pulse input
from the landfill, Equation 3 is employed to estimate the con-
centration vs. time data at the water table. The
concentration vs. time curve is then transformed into a square
pulse having a constant concentration equal to the peak
concentration, Cu, from the unsaturated zone, and a duration,
to, chosen so that the total areas under the curve and the
pulse are equal, as illustrated in Equation 3. This square
pulse is then used as the input to the linkage assessment,
Equation 2, which estimates initial dilution in the aquifer to
give the initial concentration, Co, for the saturated zone
assessment. (Conditions for B, thickness of unsaturated zone,
have been set such that dilution is actually negligible.) The
saturated zone assessment procedure is nearly identical to
that for the unsaturated zone except for the definition of
certain parameters and choice of parameter values. The maxi-
mum concentration at the-well, Cmax, is used Co calculate the
index values given in Equations 4 and 5.
B. Equation 1: Transport Assessment
C(y ,t) =T [exp(Ai) erfc(A2) + exp(B^) erfc(B2)] = P(x,t)
Requires evaluations of four dimensionless input values and
subsequent evaluation of the result. Exp(A^) denotes the
exponential of A]_, e , where erfc(A2) denotes the
complimentary error function of A2. Erfc(A2) produces values
between 0.0 and 2.0 (Abramowitz and Stegun, 1972).
where:
A. - 2_ [V* - (V*2 + 4D* x- u
Al ~ 2D*
Y - t (V*2 -i- 4D* x u*)^
2 ~ (4D* x t)?
Bl - I [V* -c (V*2 + 4D* x
Dl 9n*
Y + t (V*2 * 4D* x
= (4D* x c)±
and where for the unsaturated zone:
C0 = SC x CF = Initial leachate concentration (ug/L)
A-8
-------
SC = Sludge concentration of pollutant (mg/kg DW)
CF = 250 kg sludge solids/m3 leachate =
PS x 103
1 - PS
PS = Percent solids (by weight) of landfilled sludge
20Z
t = Time (years)
X = h = Depth to groundwater (m)
D* = a x V* (m2/year)
a = Dispersivity coefficient (m)
V* = — 2 — (m/year)
0 x R
Q = Leachate generation rate (m/year)
0 = Volumetric water content (unitless)
R = 1 •»• _d£Z x Kd = Retardation factor (unitless)
0
P(j-y = Dry bulk density (g/mL)
K^ = Soil sorption coefficient (mL/g)
. 365 x u , ,_i
U* = — - - tt (years) L
1
U = Degradation rate (day"1)
and where for the saturated zone:
C0 = Initial concentration of pollutant in aquifer as
determined by Equation 2 (ug/L)
t = Time (years)
X = AA = Distance from well to landfill (m)
D* = a x V* (m2/year)
a = Dispersivity coefficient (m)
u* = K * L (m/year)
d x R
K = Hydraulic conductivity of the aquifer (m/day)
i = Average hydraulic gradient between landfill and well
(unitless)
<& = Aquifer porosity (unitless)
R = 1 + dr"y x K^ = Retardation factor = 1 (unitless)
0
since Kj is assumed to be zero for the saturated
zone
C. Equation 2. Linkage Assessment
Q x W
C
'« " °u X 365 [(K x i) * 0] x B
A-9
-------
where:
Co = Initial concentration of pollutant in the saturated
zone as determined by Equation 1 (ug/L)
GU = Maximum pulse concentration from the unsaturated
zone (ug/L)
Q = Leachate generation rate (m/year)
W = Width of landfill (m)
K = Hydraulic conductivity of the aquifer (m/day)
i = Average hydraulic gradient between landfill and well
(unitless)
0 = Aquifer porosity (unitless)
B = Thickness of saturated zone (m) where:
B > P * W « • and B > 2
— K x i x 365 —
D. Equation 3. Pulse Assessment
C(XTI:) = P(x,c) for 0 < t < t0
= P(X,t) - P(x,C - t0) for t > t(
where:
to (for unsaturated zone) = LT = Landfill leaching time
(years)
to (for saturated zone) = Pulse duration at the water
table (x = h) as determined by the following equation:
t0 = [ £ * C dt] -s- Cu
C(y,t)
P'Xjt' = —r as determined by Equation 1
co
B. Equation 4. Index of Groundwater Concentration Increment
Resulting from Landfilled Sludge (Index 1)
1. Formula
Index 1 =
BC
where :
= Maximum concentration of pollutant at well =
Maximum of C(A£,t) calculated in Equation 1
(Ug/D
BC = Background concentration of pollutant in
groundwater (ng/L)
A-10
-------
2. Sample Calculation
,
1'
- 0.267 ug/L + 10 Ug/L
- 10 Ug/L
P. Equation 5. Index of Human Toxicity Resulting from
Groundwater Contamination (Index 2)
1 . Formula
[Cli - 1) BC x AC] + DI
index 2= — -i - — -
where :
II - Index 1 = Index of groundwater concentration
increment resulting from landfilled sludge
BC = Background concentration of pollutant in
groundwater (ug/L)
AC'= Average human consumption of drinking water
(L/day)
DI = Average daily human dietary intake of pollutant
(Ug/day)
ADI = Acceptable daily intake of pollutant (ug/day)
2. Sample Calculation
n nan/ [(1.0267 - 1) x 10 Ug/L x 2 L/day] + 335 ug/day
°*°904 " 3712 ug/day
III. INCINERATION
Based on the recommendations of the experts at the OWRS meetings
(April-May, 1984), an assessment of this reuse/disposal option is
not being conducted at this time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
IV. OCEAN DISPOSAL
Based on the recommendations of the experts at the OWRS meetings
(April-May, 1984), an assessment of this reuse/disposal option is
not being conducted at this time. The U.S. EPA reserves the right
to conduct such an assessment for this option in the future.
A-ll
-------
TABLE A-l. INPUT DATA VARYING IN LANDFILL ANALYSIS AND RESULT FOU EACH CONDITION
* Condition of Analysis
Input Data
Sludge concentration of pollutant, SC (pg/g DM)
Unsaturated zone
Soil type and characterist ics
Dry bulk density, Pjry (g/mL)
Volumetric water content', 6 (unitless)
Soil sorption coefficient, Kj (mL/g)
Site parameters
l.eachate generation rate, Q (in/year)
Depth to grounduater, h (in)
Diapers! vity coefficient, O (in)
Saturated zone
Soil type and characteristics
Aquifer porosity, 0 (unit I ess)
Hydraulic conductivity of the aquifer,
K (in/day)
Site parameters
Hydraulic gradient, i (unitless)
Distance from well to landfill, AH (in)
Dispersivity coefficient, Q (m)
1
9.8
1.925
0.133
43.4
0.8
5
0.5
0.86
0.001
100
10
2
40
1.925
0.133
43.4
0.8
5
0.5
0.44
0.86
0.001
100
10
3
9.8
1.53
0.195
6.58
0.8
5
0.5
0.44
0.86
0.001
100
10
4 5
9.8 9.8
NAb 1.925
NA 0.133
NA 43.4
1.6 0.8
0 5
NA 0.5
0.44 0.389
0.86 4.04
0.001 0.001
100 100
10 10
6
9.8
1.925
0.133
43.4
0.6
5
0.5
0.44
0.86
0.02
50
5
7 8
40 Na
NA N
NA N
NA N
1.6 N
0 N
NA N
0.389 N
4.04 N
0.02 N
50 N
5 N
-------
TABLE A-l. (continued)
Condi lion of Analysis •
Results
Unsaturated z.one assessment (Equations 1 and 3)
Initial leachate concentration, C0 ((Jg/l.)
Peak concentration, Cu (pg/L)
Pulse duration, ta (years)
Linkage asaeasment (Equation 2)
Aquifer thickness, B (m)
Initial concentration in saturated zone, Ca
(Mg'L)
1
2450
26.1
469. B
126
26.1
2
10000
106.4
469. 8
126
106.0
3
2450
163.8
74. B
126
164.0
4
2450
2450
5.00
253
2450
5
2450
26.1
469. B
23. 8
26.1
6
2450
26.1
469. a
6.32
26.1
7
10000
10000
5.00
2.38
10000
a
N
N
N
N
N
Saturated zone assessment (Equations 1 and 3)
Maximum well concentration, C|nax (pg/L)
Index of grounduater concentration increment
resulting from landfilled sludge,
Index 1 (unitless) (Equation 4)
Index of human toxicity resulting from
grounduater contamination, Index 2
(unitless) (Equation 5)
0.267
1.03
1.09
1.11
0.0904 0.0908
0.266
1.03
0.0904
0.266
1.03
1.42
1.14
10.12 231.5 N
2.01
24.15 0
0.0904 0.0910
0.0960 0.215 0.0902
"N - Null condition, where no landfill exists; no value is used.
DHA = Not applicable for this condition.
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