svEPA
United States
Environmental Protection
Agency
Office of Water
Planning and Standards (WH-553)
Washington DC 20460
January 1979
EPA-440/4- 79-016
Water
Identification and
Evaluation of Waterborne
Routes of Exposure from
Other Than Food and
Drinking Water
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DISCLAIMER
This report has been reviewed by the Office of Water
Planning and Standards, EPA, and approved for publication.
Approval does not signify that the contents necessarily
reflect the views and policies of the Environmental Protec-
tion Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
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EPA-440/4-79-016
January. 1979
IDENTIFICATION AND EVALUATION OF WATERBORNE ROUTES OF
EXPOSURE FROM OTHER THAN FOOD AND DRINKING WATER
Contract No. 68-01-3857
Task 4
Project Officer: Martin P. Halper
Task Manager: Michael A. Callahan
Monitoring and Data Support Division
Office of Water Planning and Standards
Washington, D.C. 20460
OFFICE OF WATER PLANNING AND STANDARDS
OFFICE OF WATER AND WASTE MANAGEMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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ABSTRACT
The purposes for this task were (1) to identify major human exposure
routes (other than food and drinking water) for waterborne pollutants; (2)
to develop a methodological framework for establishing the significance of
these routes for quantifying the risks to humans associated with these
routes; and (3) to incorporate this framework into a risk assessment
methodology and test its usefulness for risk assessments of chlordane and
heptachlor.
Inhalation of vapors from polluted water and absorption of pollutants
through the skin during direct contact with water were chosen as the most
significant alternative exposure routes for consideration in this report.
The process of estimating water exposure consists of (1) identification of
human activities that can result in exposure; (2) identification of
subpopulations involved in these activities; (3) assessment of activity
duration or degree of daily exposure to the different sources of water;
and (4) summation of average daily exposures for different subpopulations.
Seventeen exposure activities (bathing, dishwashing, etc.) in personal,
recreational, and household categories were identified. Estimates for
these activities were made of average daily exposure by inhalation or skin
absorption routes, exposure extent, and total national yearly exposure,
with subpopulations identified by age, sex, and geographic location in
several cases.
Calculations for chlordane and heptachlor showed inhalation of vapors from
polluted water to be negligible compared to other intakes, but for
chlordane, skin absorption from water contact may be a significant
exposure route.
ii
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FOREWORD
This report is part of a series of reports being prepared under the
Monitoring and Data Support Division's risk assessment program. This
program is directed towards investigating the risks due to presence of 129
Priority Pollutants in our nation's waters.
Some of the reports prepared under this program will address specific
pollutants. Others, such as this one, are generic in nature and are meant
to be tools to use when performing risk assessments on a wide variety of
pollutants.
The information in this report can be used to assess the significance of
two general exposure routes to humans from waterborne pollutants:
inhalation of vapors from polluted water and dermal absorption from
contact with polluted water. The properties of the specific pollutant
being assessed are used along with the general information contained in
this report to determine the significance of either of these two exposure
routes.
The information in this report was used in two test cases: chlordane and
heptachlor. For both chemicals, inhalation of vapors from polluted water
was shown to be an insignificant exposure route when compared to other
sources of exposure. For heptachlor, dermal absorption was also shown to
be a relatively minor exposure route. But in the case of chlordane, the
exposure levels from dermal absorption for certain scenarios could not be
termed insignificant, as they could possibly be of the same order of
magnitude as other exposures. Use of the information in this report in
this way has therefore highlighted a potentially important exposure route
for some subpopulations, and any risk assessment for chlordane from
waterborne sources must address this exposure route.
A companion report is now being prepared which investigates the
significance of waterborne pollution in contaminating food and drinking
water. The report will look at various ways in which waterborne
pollutants may end up in food or drinking water, and estimate the
importance of the various routes. These two reports are being
incorporated into the overall risk assessment methodology used in
Monitoring and Data Support Division's risk assessment program.
Michael A. Callahan
Task Manager
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TABLE OF CONTENTS
I. SUMMARY 1
II. INTRODUCTION 4
III.GENERAL METHODOLOGY 6
A. WATER EXPOSURE 6
B. AVERAGE DAILY INTAKE 8
C. RISK ESTIMATION 10
IV. EXPOSURE TO PRIORITY POLLUTANTS 13
A. FRAMEWORK FOR ANALYSIS 13
B. EXPOSURE ROUTES 13
C. EXPOSURE ACTIVITIES 14
D. SOURCES OF WATER 17
E. SITUATIONAL CATEGORIES 17
F. EXTENT'OF EXPOSURE 18
G. FREQUENCY/DURATION 18
H. SUBPOPULATION CATEGORIES 19
I. RESULTS OF EXPOSURE ESTIMATES 19
V. EFFECTIVE DOSE RATE 27
A. INTRODUCTION 27
B. VAPOR INHALATION 27
C. SKIN ABSORPTION 35
VI. APPLICATION OF METHODOLOGY TO CHLORDANE AND
HEPTACHLOR RISK ASSESSMENTS 39
References 43
APPENDICES
A. MATHEMATICAL APPENDIX A-l
B. RECREATIONAL SUBPOPULATION EXPOSURES B-l
IV
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I. SUMMARY
Previous assessments of risks to man from waterborne priority pollu-
tants, conducted for the Monitoring and Data Support Division of the
Environmental Protection Agency, have focused on food and water ingestion
as the primary routes of exposure. The purposes of this task were to:
» Identify other major human exposure routes for waterborne
priority pollutants.
e Develop a methodological framework for establishing the
significance of these routes and for quantifying the risk
to humans associated with these routes.
o Incorporate this framework into a risk assessment methodology
and test its usefulness by application to chlordane and
heptachlor/heptachlor epoxide risk assessments.
Inhalation of vapors from water containing priority pollutants and
absorption of priority pollutants through the skin during direct contact
with water were chosen as the most significant alternative exposure routes
for consideration in this analysis. The methodological framework
developed for assessing human risks by these routes incorporated three
areas: estimation of water exposure by subpopulation and water source:
estimation of an "average daily intake" for persons subjected to inhala-
tion or skin absorption exposure, and consideration of potential toxicity
via these routes.
The process of estimating water exposure consists of identifying
human activities that can result in exposure and subpopulations involved
in these activities, assessing activity duration and/or degree of daily
exposure to different sources of water and summation of average daily
exposures for different subpopulations. Seventeen exposure activities
(e.g., bathing, washing, fishing, swimming, dishwashing, etc.) in personal,
recreational and household categories were identified and estimates of
average daily exposure by inhalation or skin absorption routes, exposure
extent, and total national yearly exposure were made with subpopulations
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identified by age, sex and geographic location in several cases. Repre-
sentative exposure results are given below:
Activity
Breathing humdified
air in home
Household cleaning
Bathing/Showering
Water Therapy
Boating
Swimming
Total Popula-
tion Exposed
78 x 1(T
71 x 10
215 x 1(T
68 x
181 x 10'
Total
Annual
Exposure
(person-hrs/yr)
59 x 109
26 x 109
9.9 x 109
6.2 x 106
1.6 x 109
3.2 x 109
Extent*
0.1
1.0
0.6
0.4
1.0
Routes
inhalation
absorption &
inhalation
absorption &
inhalation
absorption &
inhalation
absorption &
inhalation
absorption &
inhalation
Several methods for estimating the "average daily intake" of priority
pollutants via inhalation and skin absorption were examined. The concept
of "effective dose rate," i.e., the rate of transfer of pollutant to the
body for different types of exposure, was used in developing daily intakes
for inhalation and skin absorption. For vapor Inhalation, the critical
parameters in estimating the effective dose rate are the rate of ventila-
tion, the concentration of pollutant in the water, the vapor pressure of
the pollutant and the chemical activity of the pollutant in water.**
Example calculations show that daily inhalation intake might range from
-9
as low as 1 x 10 mg/day of chlordane at an ambient water concentration
of 1 ppb to 28 mg/day chloroform at an ambient water concentration of
1 ppm. In general, we concluded that because of the relatively low vapor
pressure of priority pollutants and the low concentrations found in
ambient water, inhalation of vapor will probably not be a significant
^Estimated fraction of body surface area exposed.
To be conservative, we assumed that any pollutant inhaled remained in the .
body. Further, we did not consider metabolism or excretion of the priority
pollutant, but focused only on the total amount inhaled or absorbed.
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exposure route, compared to food and water ingestion, unless a fog or
mist of water is inhaled. In the latter case, the moisture content of
the fog and the actual exposure duration are critical elements in the
analysis.
Examination of the skin absorption exposure route indicated that
the critical factors in establishing the effective dose rate are the
extent of surface exposed, the concentration of pollutant in the water,
and the diffusion rate through the stratum corneum layer of the skin,
which is in turn dependent upon the permeability coefficient of the pollu-
tant and/or the partition coefficient of the pollutant between the skin
and water. Although no physical/chemical data were readily available in
the literature on skin absorption of specific priority pollutants, general
methods for estimating the effective dose rate for skin absorption were
developed. Our calculations suggested that the effective dose rate of
priority pollutants might range from about 10 to 0.1 mg/day for total
body exposure to priority pollutants at ambient water concentrations of
1 ppb to 1 ppm, respectively. Therefore, depending upon the actual
frequency and extent of water exposure, and pollutant concentrations,
the average daily intake of priority pollutants from skin absorption
might be the same order of magnitude as the daily intake from food or
water ingestion. Future risk assessments should consider the skin absorp-
tion route, especially for subpopulations with high water exposure
potential.
The methods developed for estimating effective dose rate and daily
intake by inhalation and skin absorption were used to determine the daily
intakes of chlordane, heptachlor and heptachlor epoxide. The results showed
that inhalation of vapor from water containing these pollutants at ambient
levels would result in average daily intakes that are negligible compared
to intake via food and drinking water ingestion. Similarly, average daily
intake by skin absorption of heptachlor and heptachlor epoxide was estimated
to be about 1% to 5% of the intake via food and drinking water ingestion
for 24-hour total body exposure to water at ambient concentration levels.
Calculations for chlordane, however, indicated that skin absorption could
possibly result in average daily exposure of comparable magnitude to food
and water ingestion. Thus this mechanism needs to be considered in the
chlordane risk assessments.
3
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II. INTRODUCTION
The Monitoring and Data Support Division, Environmental Protection
Agency, is conducting a systematic investigation of the sources and distri-
bution of 129 priority pollutants in the nation's environment in order to
determine the exposure and risks to man, fish and other biota. The results
of this effort will be the development of recommendations for regulatory
action.
One part of this program is the preparation of risk assessments for
specific chemicals, which identify the populations chronically exposed and
give estimates of the health risks to man, fish and wildlife. In the
conduct of these risk assessments, it is important to identify and quantify
the major water-based routes of human exposure to the priority pollutants.
Most previous work has focused on food and drinking water ingestion as the
primary routes of human exposure, since they affect the broadest segment
of the population. However, there are a number of other potential water-
related routes of exposure that might be significant for specific pollu-
tants or human subpopulations. For example, inhalation exposure might
occur through humidified air in the home; skin absorption might occur
through bathing, swimming or occupational exposure.
The objectives of this task are to:
• Identify major human exposure routes for waterborne pollutants
other than direct ingestion of food and drinking water and the
populations exposed through some of these routes.
• Develop a methodological framework for establishing the signifi-
cance of these routes and for quantifying the risk to humans
associated with these routes.
• Incorporate this framework into the risk assessment methodology
previously developed and test its usefulness by applying it to
chlordane and heptachlor/heptachlor epoxide risk assessments.
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In order to complete this task within the authorized level of effort,
we have adopted an approach which is based upon the following assumptions
and conditions:
• Two principal exposure routes are considered—inhalation of vapor
or mist from a water source which contains a priority pollutant
and skin absorption of a priority pollutant due to immersion of
portions of the body in water containing the pollutant.
• Activities which can result in exposure by these two routes are
identified, but the numbers of persons engaged in these activities,
and the duration and/or frequency of exposure are quantified only
for some examples for which data were readily available.
• Details of the mechanisms of skin absorption and vapor inhalation,
and the toxic effects of chemicals via these routes are not ex-
amined. Methods are described only to estimate the quantities
absorbed or inhaled. It is assumed that these quantities can be
directly compared to those ingested in food and water, and that
the physiological response to absorption and inhalation of
priority pollutants is known or can be evaluated.
• The main focus of this task is methodological, with the aim of
establishing an approach to calculation of risk for subpopulations
exposed to priority pollutants by routes other than food and
drinking water.
Section III briefly describes the methodology that can be used to
estimate human risk from inhalation and skin absorption routes. A more
mathematical treatment of the approach is given in Appendix A. Section
IV discusses the number of persons exposed and the frequency and duration
of exposure to water in selected exposure activities. Section V presents
methods for estimating the rates at which priority pollutants are inhaled or
are absorbed through the skin. Section VI contains some sample calcula-
tions using chlordane, heptachlor and heptachlor epoxide to compare the
daily intake of these pollutants by inhalation of vapor and by absorption
through the skin to the daily intake from food and drinking water inges-
tion.
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III. GENERAL METHODOLOGY
A primary objective of this task was to develop a methodological
framework for quantifying both exposure and risk to humans from waterborne
pollutants, for exposure routes other than ingestion. This framework was
to be incorporated into an overall risk assessment methodology, which
originally focused upon the ingestion route. Our approach consisted of
expanding and generalizing the risk assessment methodology to account
for the more complex .exposure mechanisms associated with non-ingestion
routes, and to permit identification of subpopulations with significant
exposure levels. The effort was divided into three methodological areas:
1. Develop methods to allow estimation of total human water expos-
ure by subpopulation and water type.
2. Develop methods to allow estimation of average human daily
pollutant intake by subpopulation.
3. Indicate the use of these methods in estimation of risk to
humans.
These areas are addressed separately below and are displayed in diagrammatic
form in Figure 1. Note that the double-bordered boxes refer to calcula-
tions involving a specific pollutant. The other boxes, which describe
the estimation of total water exposure, need to be performed only once
for all pollutants.
A. WATER EXPOSURE
For each exposure route that is identified, the average daily human
exposure to water can be estimated in the following ways:
- Identify the activities which could result in exposure along that
route.
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FIGURE 1: Exposure and Intake Estimates
Identify Exposure
Routes (e.g.,
Inhalation)
Estimate Pollutant
Concentration by
Water Source
Identify Relevant
Activities for
Each Route (e.g.,
Swimming)
Determine Relevant
Physical or Chem-
ical Properties
(e.g., Vapor
Pressure)
Identify Water
Source (e.g., Lake)
Identify Subpopu-
1 ation Groups
(e.g., Housewives^
1
Estimate Effective
Dose Rate for
Each Route
Estimate Activity
Rates for Each
Group (Degree of
Exposure)
I
I
Compute Average
Daily Intake for
Each Group by
Activity and Water
Source
Compute Average
Daily Exposure
for Each Group by
Water Source
I
Compute Average
Daily Intake of
Pollutant for
Each Group
Compute National
Average Daily '
Water Exposure
T
Use in Risk Calculations
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Identify the subpopulation categories which might be involved
in these activities.
Identify the sources of water relevant to exposure through these
activities.
- Using average daily activity rates, estimate the degree of daily
exposure for each of these activities.
Sum overall activities to obtain the average daily water exposure
for each subpopulation group, by water source.
Compute the national average daily water exposure using the
relative sizes of different subpopulations.
The degree of exposure will be defined in different ways for differ-
ent exposure routes. In the case of inhalation, the degree of exposure
is simply the total volume of air inhaled per day. (It is assumed that
the air may contain traces of pollutants which were originally waterborne,
and subsequently vaporized). In the case of skin absorption, the degree
of exposure is the product of a number of factors, primarily the extent
of exposed skin area and the duration of exposure. Of course, for inges-
tion, the degree of exposure is simply the amount of solid or liquid in-
gested per day. Thus the degree of exposure is a measure of daily exposure
per capita for each different exposure route. These concepts are elabor-
ated in Section IV below, as well as in the Mathematical Appendix.
B. AVERAGE DAILY INTAKE
For a specific pollutant, the average daily intake may be estimated
from a knowledge of the pollutant concentration in water and the total
daily exposure to water derived above. In the case of water ingestion,
the average daily intake is simply the product of daily water intake and
concentration. However, with other exposure routes it is necessary to
compute an effective dose rate, which relates pollutant concentration in
water to the actual amount of pollutant entering the human body. The
effective dose rate will be defined as the quantity of pollutant taken in
(via absorption, inhalation, ingestion, etc.) per unit of exposure. Thus,
if exposure is measured in area-hours per day (e.g., skin contact), then
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the effective dose rate would be measured in ug per area-hour. Table 1
displays all the units of measurement necessary to apply this methodology
to three principal exposure routes. Note that the effective dose rate
for ingestion is equivalent to pollutant concentration.
For the non-ingestion routes, the effective dose rate must be computed
from the pollutant concentration, certain physical and chemical properties
of the substance in question, and pertinent human physiological parameters.
For vapor inhalation, the relevant properties are the vapor pressure of the
substance and the activity coefficients of the solution, etc. , which deter-
mine the amount of pollutant in the vapor above a solution. For skin
absorption, the relevant properties are the diffusion and/or the perme-
ability coefficients, partition coefficients for tissues vs solution, and
skin thickness. The basis for calculating effective dose rate for both
of these routes is explained more fully in Section V. Again, the necessary
computational steps are diagrammed in Figure 1:
- Determine the values of the relevant physical, or chemical proper-
ties of the pollutant, and the relevant human physiological
properties for each exposure route being considered.
- Estimate the effective dose rate as a function of these properties
and of the concentrations of the pollutant in various sources of
water.
- Multiply the effective dose rate by the degree of exposure for
each activity to obtain the average daily intake via that activity,
for various population groups.
- By summing over all activities and water sources, determine the
average daily intake of pollutant for each group, via the differ-
ent routes.
If so desired, the summation can be adjusted to yield total intake
through a given water source, or via a particular activity. These computa-
tions would be analogous to those shown for total water exposure in the
Mathematical Appendix.
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C. RISK ESTIMATION
Once the average daily intake has been determined, risk can be
estimated by two possible approaches:
Method A: Assuming the toxicity is independent of the exposure
route (i.e., once the pollutant enters the human, the
toxicity is a function only of the amount of intake, not
the site of intake), risk can be computed from the
average daily intake from any route, e.g., from inhala-
tion or skin absorption.
Method B: If the toxic effects are dependent on a specific route
(e.g., skin absorption), then risk should be computed
from the degree of exposure, the pollutant concentration
and the toxicity resulting from that specific exposure
route.
One form in which toxicity data are expressed, after appropriate
normalization and extrapolation, is "excess risk per unit of exposure."
For chronic effects such as carcinogenicity, some investigators assume a
linear relationship between exposure and risk, and for other types of
toxicological responses non-linear dose-response models are often found.
If one considers toxicity based on inhalation exposure, the risk from a
carcinogenic substance could be expressed as the probability of a tumor
being induced in an organism chronically exposed to a given airborne
concentration of that substance. For a linear model, the excess risk per
unit of exposure is simply the slope of the dose-response curve, and can
be interpreted as the increase in probability of tumor per unit of In-
creased concentration. There may be a background incidence of tumors,
so that a positive probability of tumors exists even at zero exposure.
The units of measurement for risk estimation, as well as the formulae
to be used, are given in Table 1. The two approaches can be summarized
as follows:
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Table 1
Units of Measurement
Extent or Quantity
Frequency
Degree of Exposure
Concentration
Effective Dose Rate
Average Daily Intake
Toxicity Based
on Intake (Method A)
Toxicity Based on
Concentration
(Method B)
INGESTION
Liters
per Day
Liters per Day
ug./l.
ug./l.
ug./bay
ABSORPTION
p
Area (e.g. m )
Hours/Day
Area-Hours/Day
ug./l
ug./Area-Hrv
ug./Day
INHALATION*
m. /Hour
Hours/Day
m.3/Day
ug./m.3
ug./m.3
ug./Day
% Increased Probability of Effect per ug./Day
% Increase
per ug./l.
% Increase
per ug./l.
% Increase
per ug./m.3
Degree of Exposure » Extent (or Quantity) x Frequency
Average Per Capita Daily Intake - Degree of Exposure x Effective Dose-Rate
Risk per Capita - Average per Capita Daily Intake x Toxicity Based on
Intake
or
Risk per Capita - Concentration x Toxicity Based on Concentration
(for specific route)
Total Risk - Number Exposed x Risk per Capita
n
Note: In this r.eport we have used the term inhalation to represent
the route of exposure, and ventilation to represent the actual
quantity breathed per time.
11
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Method A: Toxicity. is expressed as excess risk per unit of
daily pollutant intake. Risk per capita is obtained
by multiplying the average daily intake by the
toxicity of the substance.
Method B: Toxicity is expressed as excess risk per unit of
pollutant concentration, for a specific exposure
route. In extrapolating from experiments with
laboratory animals, adjustments must be made to
compensate not only for species differences in toxic
effects but also for the degree of exposure. Then
the risk per capita is obtained from the product of
concentration and adjusted toxicity.
In most cases, available data will be suitable only for Method A.
However, the advantage of Method B is that there is no need to calculate
an effective dose rate, which is based on idealized physical and chemical
pi-
laws or assumptions.
Finally, the risk per capita can be multiplied by the number exposed
in a subpopulation to obtain the total risk for that subpopulation. The
Mathematical Appendix shows various ways to calculate risk, focusing on
either a specific water source or a specific activity.
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IV. EXPOSURE TO PRIORITY POLLUTANTS
A. FRAMEWORK FOR ANALYSIS
In order to develop reasonable estimates of exposure of certain sub-
populations to priority pollutants, a general framework describing the
nature of the exposure must first be specified. The framework presented
here consists of a number of factors which characterize the exposure of
an individual or groups of individuals to priority pollutants. Quanti-
fication of these characteristics then permits estimates of populations
exposed to priority pollutants. The factors include:
Exposure Route—The anatomical sites through which the pollutant
contacts or enters humans.
Exposure Activities—The human functions which lead to exposure to
water by some exposure route.
Sources of Water—The nature of the water source, containing the
priority pollutant, to which persons are exposed.
Situational Categories—The environmental, geographic or locational
factors which influence exposure.
Extent of Exposure—The fraction of the body exposed to water con-
taining the priority pollutant.
Frequency/Duration—The number of hours (per day, year, etc.)
during which exposure occurs.
Subpopulation Categories—Demographic factors which influence ex-
posure (male, female, adult, children, etc.)
In this section we will first discuss these factors individually
and then develop representative estimates of the numbers and durations
of persons exposed by different routes through different exposure
activities.
B. EXPOSURE ROUTES
The exposure route was defined as the means by which a waterborne
pollutant enters the human body. For this task, dermal absorption and
inhalation were considered to be the most significant routes encountered
in normal, every-day activity. Other exposure routes, such as sub-cutaneous
13
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injection, and exposure of a specific organ (eyes), or finer detail in
identified routes, such as greater absorption potential in certain areas
of the body (forehead, scrotum) or dermal absorption of vapors were not
examined because of limited data.
Several assumptions were made when considering the dermal absorp-
tion route. As mentioned above, the potential for absorption was con-
sidered to be equal for all parts of the body. The absorption rate was
considered to be constant under all conditions such as varying water
temperatures, flow rates, or intensities of activity. In addition, the
volume of water to which a person was exposed was not considered Impor-
tant. For example, being totally submerged in a pool of water was con-
sidered equivalent to being thoroughly sprayed by water. Spray coats the
body with a film of water which is available for absorption. Similarly,
wet clothing holds a small reservoir of water against the body which can
be absorbed over time.
In considering inhalation, some simplifying assumptions can also be
made which result in conservative (high) values of exposure. We assumed
that any pollutant vapor inhaled is removed (absorbed) by the lungs,
whether it was in the form of vapor or*droplets of varying sizes. Ventila-
tion rate varies with activity, but for our estimates, we considered a
normal ventilation rate for persons engaged in moderate activity.
C. EXPOSURE ACTIVITIES
Exposure activities were generally defined as human functions or
processes which may lead to exposure to waterborne pollutants through
inhalation and/or dermal absorption. A large number of water-related
activities were identified and grouped into five categories: personal,
recreational,' household, occupational and incidental exposure. Table 2
lists those activities that were selected for developing exposure
estimates.
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Table 2
Activities for Which Exposure Estimates were Developed
Personal Recreational Household
Bathing/Showering Boating Breathing artificially
Dental Care Fishing humidified air
Hand and Face Washing Swimming Automobile washing
Shaving Water skiing Hand clothes-washing
Toothbrushing Hand dishwashing
Water Therapy Household cleaning
Ironing
Lawn watering
A large number of other water-related activities were initially
identified but excluded from the analysis because of lack of data and/or
a presumably low risk. Some of the activities worth noting are: personal
activities such as wearing cosmetics and contact lenses, douching; snow
sports, puddle playing, ice skating, water-related entertainment (e.g.,
amusement park rides); and incidental breathing and contact with natur-
ally humidified air (e.g., fog, living near lakes), rain and snow.
Some of the exposure activities we examined may have equally
low risk; nevertheless, to provide a data base representative of a wide
range of exposures, consideration of low risk activities is warranted
when data are readily available.
Another important exposure activity category is occupational expos-
ure. Table 3 lists occupational categories that could result in signi-
ficant water exposure. In this task, however, determination of occupa-
tional exposure was not possible. No information was readily available
on the frequency of exposure to water in different occupations. Avail-
able information on water intake and discharge rates for industry sectors
was not believed to be representative of the amount of water potentially
available for exposure because a significant percentage of it is enclosed
and never comes in contact with employees. Within an occupation, employees
have different exposure frequencies and extents. For example, two people
working in a carwash, a washer and a cashier, would have significantly
different exposures-. Information on the number of people employed in
15
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Table 3
Occupational Categories with Potential for Water Exposure
Coast Guard, Navy, Merchant Marine Snowmakers
Skin divers (police)
Fisherman Aquarium employees
Underwater photographers Zoo keepers
Professional swimmers, instructors, lifeguards Fish farmers
Rowers, professional water sportsmen
Water transportation workers Gardeners
Greenhouse workers
Skating instructors Landscape workers
Ski instructors
Amusement park workers Farm laborers
Firemen
Food service people, bartenders
Dishwashers
Cleaning people
Laundry workers
Window washers
Plumbers
Barbers, hairdressers, manicurists
Carwashers
Heating/ventilation/air-conditioning workers
Textile workers
Meat packers
Food processers
Physicians, nurses, therapists, dentists
Researchers (laboratory)
Researchers (field)
Sewage treatment plant workers
Dredge workers
Tunnel makers
Miners, oil drillers
Hydro-electric utility workers
Sawmill workers
Well diggers
Quarriers
(Utility workers in holes)
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various occupational categories does not clearly differentiate between
people with different types of jobs within the category. A great amount
of time and effort would have to be devoted in contacting different
industries and commercial establishments and interviewing representative
water-exposed employees to make useful estimates of occupational exposure.
Nonetheless, the methods given in Appendix A do permit computation of
occupational exposure, provided that the data become available.
For all activities, the associated exposure route was either inhala-
tion alone or dermal absorption plus inhalation. Under all conditions
when dermal contact with a body of water was made, the water was assumed
to have vaporized into the air around it. An individual with his hands
submerged in water would therefore also inhale water vapor at the same
time. Inhalation of water vapor alone, without dermal contact, was possi-
ble, however, as in the breathing of artificially humidified air. For the
purpose of this task, when a dermal absorption exposure was calculated, the
concurrent inhalation exposure was not considered.
D. SOURCES OF WATER
Depending upon the activity being considered and the environmental
characteristics, people may be exposed to different types of water. These
may be classified as follows:
(i) ocean (v) lake
(ii) water supply (vi) rivers and streams
(iii) process water (vii) other (pools, drainage, etc.)
(iv) precipitation
Exposure computations ideally should distinguish between exposure to
various water sources, since ultimately a different level of pollutant
concentration may be ascribed to each water source. Of course, some
activity classifications will correspond to only one water source (e.g.,
household dishwashing—water supply). In other cases, such as recreational
activities, different water sources must be identified. Because the pollu-
tant concentration is the most 'important variable, we did not attempt to
distinguish between different sources of water in our example calculations.
E. SITUATIONAL CATEGORIES
Geographic and environmental conditions will imply fluctuations in
both the number of 'people involved in certain occupations and the sources
17
-------
of water encountered. Hence, the possible situations should be sub-
divided into a matrix of environmental and habitational categories. The
environmental categories describe the prevalent geographic and climatic
conditions, whereas the habitational categories characterize the density
and nature of human settlement.
Environmental Habitational
coastal urban
near lakes suburban/town village
rivers rural
arid regions wilderness
To simplify our work, we did not consider these situational categories
in our examples.
F. EXTENT OF EXPOSURE
The extent value is an estimate of the portion of the body exposed
through skin absorption. (For inhalation we assumed that the same
area of body is exposed to water particles or vapor during each breath, and
no extent estimate was necessary.)
Extent values, ranging from 0.1 to 1.0, are based on the percent of
the total body surface area exposed. Hands (including lower arms) or
face (and neck) each have values of 0.1, for example, while the entire
body has a value of 1.0. Each activity with a dermal exposure was assign-
ed an average extent value estimated to be representative of the degree
of contact with water.
G. FREQUENCY/DURATION
Frequency was defined as the number of hours per year an individual
is exposed to water through an activity. Frequency was developed in two
forms from literature data or through estimates by knowledgeable staff.
In some cases, the population exposed and the actual number of events per
person annually was available (as for swimming). The product of these two
was multiplied by an estimated number of hours per event to provide hours
per annum. In other cases (for example, water therapy), only the number
of person-hours per year was available with no information on the actual
number of people exposed or the average number of experiences per
18
-------
individual. The number of person-hours was useful in determining the
exposure of the total population via the activity but would not enable
subpopulation breakdown.
H. SUBPOPULATION CATEGORIES
Subpopulations exposed to waterborne pollutants within each activity
were identified when possible. Identification was most successful in
activities, such as recreational, for which a large body of statistical
information was available. In these cases, subpopulations by age group,
sex, and, occasionally, region could be identified and their associated
exposures determined. In most cases, however, the information available
was an estimation of the total population at risk. Further estimation
of subpopulation exposure,using census data or other sources, could be
performed but the usefulness is questionable in this methodology task.
To maintain consistency throughout the report, the 1976 U.S. popula-
tion census figure of 215,118,000 was chosen and used whenever possible. In
cases where the percent of population involved in the activity during another
year (such as 1975) was available, it was updated for the 1976 population
assuming that the percentage had not changed over time. In some cases,
however, only absolute numbers of participants during a previous year were
available. It was assumed, then, that the numbers roughly represented
1976 participation as well.
I. RESULTS OF EXPOSURE ESTIMATES
Using the framework described above, and the mathematical formula-
tion of exposure given in Appendix A, we estimated exposure values for
the total U.S. population and subpopulations using readily available
data. The results and discussion which follow are representative and
are not intended to be complete or exhaustive. They are presented here
to give some useful information and to show how one can estimate various
exposure factors if data are available.
Table 4 summarizes data on exposure activity, populations exposed,
extent, water sources and exposure route for household, personal and recrea-
tional categories. A more detailed discussion of the exposure estimates
is provided below.
19
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Table 4
N>
O
Summary of Exposure Information
Exposure
Activity
HOUSEHOLD
Artificially humidified air
humdifier
dishwasher
Hand clothes washing
Hand dishwashing
Household cleaning
Ironing
Outdoor household water use
PERSONAL
Bathing/Showering
Dental Care
Hand and face washing
Shaving
Population
Exposed
(million)
76.5
90
65
71
71
74
63
215
215
215
80
Total
Exposure
(10 person-hrs/yr)
59,000
16,000
840
25,900
7,400
7,700
3,300
9,900
57
3,900
960
Extent
NA2
NA
0.1
0.1
0.1
NA2
0.1
1.0
0.1
0.2
0.1
Water Source
water supply
water supply
water supply
water supply
water supply
water supply
water supply
water supply
water supply
water supply
water supply
Routes
vapor inhalation
vapor inhalation
absorption, vapor
inhalation
absorption, vapor
inhalation
absorption, vapor
inhalation
vapor and droplet
inhalation
absorption, vapor
and droplet inhalation
absorption, vapor
and droplet inhalation
absorption, vapor
and droplet inhalation
dermal absorption
absorption
All sources cited in text.
Not applicable.
-------
Table 4, (Continued)
Exposure
Activity
Toothbrushing
Water therapy
RECREATIONAL
Boating
Fishing
2 Swimming
Water skiing
Population
Exposed
(million)
177
19
person-events
annually
68
54
181
20
Total
Fvpn.ciirp
(10 person-hrs/yr)
2,200
Extent Water Source
0.1 water supply
0.6 water supply
Routes
absorption
absorption and
inhalation
1,600
6,600
3,300
0.4 ocean, lake,
river and
stream
0.2 lake, river
and stream,
ocean, pond
1.0 outdoor pool,
ocean, lake,
absorption, vapor
and droplet inhalation
absorption, vapor
and droplet inhalation
absorption, vapor
and inhalation
rivers and stream
260
1.0 ocean, lake,
river and
stream
absorption, vapor and
droplet inhalation
-------
1. Household
Six household activities involving exposure to water were examined.
The activities were Ironing, hand dishwashing, household cleaning, hand
clothes washing, outdoor household activities and breathing artificially
humidified air. For ironing, cleaning, dishwashing and outdoor activities,
it was assumed that one person per household was involved in each
activity. The number of households in the United States was obtained
(23)
from the Bureau of Census. ' The number of households owning irons
(4)
was found in Merchandising annual statistics. In the case of hand
clothes washing, the population exposed was assumed to be all females
aged 18 to 64 years old, probably a conservative over-estimation of the
lingerie hand washing inclinations of women. The extent of exposure
was estimated to be 0.1 (hands and forearms) for each activity with
the exception of ironing, which is an inhalation route exposure.
Frequency/duration of household activities were estimated by ADL staff
as follows:
Ironing—2 hours per week
Cleaning—2 hours per week
Dishwashing—7 hours per week
Clothes Washing—1/4 hour per week
Outdoor activities—1 hour per week
In all cases the water source is water supply.
Two sources of artificial household humidity were considered:
humidifiers and dishwashers. Clothes dryers, steam heat systems and
washing machines were excluded from analysis because venting or covers
usually prevents the escape of more than a small amount of vapor. Infor-
mation on the number of humidifiers, the hours per year in use,estimated
at 776 hours (in Akron, OhioX and quantity of water released was found
in a Federal Energy Administration report on energy efficiency. ' It
was assumed that each humidifier exposed three people to humid air and
that Akron, Ohio was representative of the average of different humidi-
fier usage patterns in the U.S. The potential total U.S. exposure to
humidified air was calculated to be 59,000,000,000 person/hours/year.
22
-------
Information on the number of homes with dishwashers was found in
(4)
Merchandising, and again, a three-person exposure was assumed for
each appliance. Duration (30 minutes) and number of annual events (365)
were estimated by case team members. The potential total U.S. exposure
to humidified air was calculated to be 16,000,000,000 hours/year. The
source of water used by both appliances is water supply.
2. Personal Activities
For each of the personal activities the population involved was
estimated on the basis of age, as follows:
• toothbrushing: the total U.S. population; ages 5 to 64;
• hand and face washing: the total U.S. population; and
• shaving: che total U.S. population; males 13 years of age
and older.
(6)
U.S. Census data was used to obtain the population number for each
activity. Duration estimates for the activities were made by the Technical
(7)
Services staff of the American Water Works Association. ADL staff
then estimated the frequency and extent of each exposure. The source of
water used for personal activities is water supply.
Activity Duration (per event) Frequency Extent
Toothbrushing 1 minute 12 hours per year 0.1
Hand and Face 1 minute 18.25 hours per year 0.2
Washing
Shaving 2 minutes 12 hours per year 0.1
(8)
The 1975 data on dental visits from the Vital and Health Statistics
were updated for the 1976 population by assuming that an individual still
makes 1.6 dental visits per year. Duration was estimated at 10 minutes
exposure to water. Thus, in 1976 the total U.S. population, 215 million,
made 344 million dental visits for a total exposure of 57 million hours
annually. The water source is water supply. The extent of skin absorption
was estimated to be .1 assuming some facial contact with water spray.
Although realistically this is a negligible exposure relative to activities
such as swimming or bathing, it is representative of the lower range of
23
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exposures encountered by a large number of people. Exposure was calculat-
ed in order to determine the magnitude of such a low exposure activity
where data were available.
Bathing and showering are generally treated as one activity in the
literature so the assumption was made that their exposures are equal
(duration, number of annual events). We assumed that the total U.S.
population engaged in this activity. Only bathing/showering in water
supply sources was considered. Salt water and fresh water showering were
(9)
excluded. A previous ADL study estimated the time duration to be 15
minutes per event and the number of events per week to be 3.5 (182 events
per year). Based on this information, an individual spends 46 hours
annually bathing and/or showering and the total population spends 9.9
billion hours annually. The extent of the body exposed is considered
to be 1.0 (total body).
An estimate was made of the number of person-hours spent in some
form of hospital-administered hydrotherapy (for instance, whirlpools,
Hubbard tanks, swimming pools). Persons receiving water therapy at home
or at sports facilities were excluded from consideration because of lark
of available data. Personal communication with physical therapists at
five Boston area hospitals provided the basis for a quantitative
estimate of number of person-events at hospitals. Neither the actual
number of individuals treated annually nor the number of treatments per
individual is easily retrievable by hospital personnel or from literature.
The total number of hospitals and physical therapy departments in the
U.S. was obtained from Hospital Statistics. ' According to the physical
therapists we talked to, the standard duration of one hydrotherapy session
is 20 minutes. It was estimated that 18.7 million person-events occur
annually. Hence the total U.S. exposure is 6.2 million hours per year.
Extent was averaged at .6 since the degree of exposure may range from
.1 for a hand whirlpool to 1.0 for the more common total body whirlpool.
The water source is water supply.
24
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3. Recreational Activities
A reasonable amount of information was found on recreational
activities. Greater detail on subpopulations (by age, sex, region) ex-
posed was available for most of the activities. The subpopulation expos-
ure estimates are presented in Appendix R. The following discusses the
more general results.
Information on boating was found in a publication of the U.S.
(12)
Department of Interior's Bureau of Outdoor Recreation. The activity of
boating includes canoeing, sailing, and other boating. A total of 68
million people participate in all boating activities, each on the average
of six activity days per year. Total population exposure was computed
to be Id,000 million hrs annually. The duration of one boating event was
estimated by case team members to be four hours. Extent of dermal expos-
ure was considered to be part of the body or .4. For each type of boat-
ing, further data are presented in Appendix B for sex, age, residence
and region. No information was available on boating in specific water
sources. Included in the total number, therefore, is boating in oceans,
lakes, streams and rivers.
The data source for information on fishing was a U.S. Department of
Interior publication, the 1975 National Survey of Hunting, Fishing and
Wildlife. A total of 54 million people engage in recrea-
tional fishing. Each angler spends an average of 25 days fishing annually.
The case team estimated the time spent per day as five hours. The total
number of hours of exposure annually for all participants is 6600 million.
Dermal exposure was estimated to be hands and feet (0.2) which may come
into contact with water during fishing. Information was also available
on exposure by sex, age and water source presented in Appendix B. The
sources of water for which data were available were salt water (oceans and
estuaries) and freshwater (lakes, rivers and streams, ponds).
All information on swimming was found in a publication on outdoor
recreation from the U.S. Department of the Interior, Bureau of Outdoor
(12)
Recreation. The total population swimming annually is approximately
181 million. An individual participates in swimming an average of nine
25
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activity days per year for roughly two hours per day (case team assump-
tion) totaling 18 hours per capita annually. The total population swims
3.3 billion hours per year. The extent of dermal exposure was considered
to be 1.0, the entire body. The available data also allowed subpopulations
to be distinguished in terms of sex, age, residence, and region (see
Appendix B). Information was available for swimming in two water sources:
outdoor pool swimming and outdoor swimming in natural bodies of water
(ocean, lake, river and stream). No information was found on indoor pool
swimming.
(12)
Literature from the Bureau of Outdoor Recreation documented water
skiing as an activity with 20 million participants annually. Each person
engages in water skiing an average of six activity days per year. Dura-
tion was estimated by the case team to be two hours per day. Extent was
estimated to be total body (1.0). No information was available on water
skiing by water sources so the presented data include skiing on lakes,
rivers and streams, and oceans. Total U.S. exposure equals 260 million
hours per year. Exposure estimates for subpopulations are presented in
Appendix B by sex, age, residence and region.
26
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V. EFFECTIVE DOSE RATE
A. INTRODUCTION
As explained earlier, the risk to a given subpopulation is a func-
tion of the average daily intake of the pollutant and the toxiclty asso-
ciatiated with the exposure route. The average daily intake was defined
as the product of the degree of exposure with the effective dose rate.
In this section we will discuss methods of estimating the effective dose
rate when persons breathe air contaminated by vapors from solutions contain-
ing priority pollutants, or are in contact with water containing priority
pollutants. General calculational methods are presented, and the critical
parameters which influence the effective dose rate are discussed.
B. VAPOR INHALATION
In this analysis, we assume that persons exposed to water containing
priority pollutants breathe air that is in equilibrium with the water.
The amount of priority pollutant inhaled is then equal to the inspiration
rate times the concentration of pollutant in the air, or:
Effective Dose Rate = Ventilation Rate x Concentration Pollutant in Air
(Inhalation)
EDRI = (VR) * Cp, air [1]
To be conservative, we assume that all of the pollutant inhaled is
absorbed in the lungs and remains in the body. Data on breathing rates
for persons performing various activities are available in the literature,
and for worst case exposure estimates one can use the inspiratory flow rate
at strenuous exercise of 6 nr/hour as an upper limit in calculations.
The key variable influencing the effective dose rate is the concentra-
tion of priority pollutant in the air above the water source.
The concentration can be determined by several methods:
• Measurement of typical pollutant concentrations in air in repre-
sentative, field situations;
27
-------
• Measurement of concentrations of pollutants in air in controlled
laboratory tests and extrapolation to field conditions; and
• Estimation based upon the physical and chemical properties of the
pollutant.
There are limited data available from field or laboratory measurements
of priority pollutant concentrations so that estimates based upon physical
and chemical properties and thermodynamic principles will most often have
to be used.
The concentration of priority pollutants in air in equilibrium with
water containing the pollutant in solution is given by the following
general equation:
P Y = Y P X [2]
t p p vp p
where:
P = total pressure of the gas phase (usually one atm in this
analysis) (atm)
p = vapor pressure of the pure priority pollutant at the system
^ temperature (atm)
Y = mole fraction in the vapor phase of priority pollutant
P
X « mole fraction in the liquid phase of priority pollutant
P
Y = activity coefficient of priority pollutant in solution
The term P Y equals P , the partial pressure of the priority pollu-
t p p
tant in the vapor phase (air) and can be related to weight concentration
by the ideal gas laws as follows:
'p, air ~ ~RT
P Y M
n a-i •*• t»T! *• J
where:
C . = concentration of pollutant in air (gm/liter)
p, air
M = molecular weight of pollutant (gin/mole)
28
-------
T = system temperature (°K)
R = gas constant (liter-atm/mole °K)
Combining equations [2] and [3] one obtains:
Y P X M
c = P vg P P [4]
p,air RT
In most cases of practical significance, equation [4] can be further
simplified by relating the mole fraction of pollutant in the liquid, X ,
P
to the weight concentration of pollutant in the liquid, C (the
usually measured quantity) as:
c
_P-J
, /M
liq P
C
+ M
w
C 1± M
1000
18
0.018 C . .
p,lz
M
P
where:
C ,. = concentration of pollutant in liquid phase (gm/liter)
C = concentration of water in liquid phase - 1000 gm/liter
wat
M = molecular weight of water = 18 gm/mole
In developing equation [5] we have assumed that the sum of concentra-
tions of all pollutants in the water is small, i.e., negligible compared
to the concentration of water. This certainly is true for pollutants which
are typically in the parts per million range.
Combining equations [4] and [5] we obtain:
.018y P C
C = P VP PiUq [6]
p.air RT l J
29
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Thus the key physical parameters which influence the weight concentra-
tion in the air are: (1) the liquid activity coefficient, (2) the liquid
concentration of the pollutant, and (3) the vapor pressure of the pollu-
tant. Within the range of exposure conditions encountered, the absolute
temperature does not vary much (say from 255°K to 311°K or 0°F to 100°F),
although it must be remembered that the vapor pressure is a strong function
of temperature.
In using equation [6], vapor pressure data are available in the
literature for most of the priority pollutants. Similarly the weight
concentrations of priority pollutants in water are available from screen-
ing and other data. Unfortunately, data are most likely not readily
available on activity coefficients of priority pollutants. In this method-
ological study, we did not thoroughly review the chemical literature on
this subject.
Some further simplifications can be made to enable order of magnitude
estimates of vapor concentrations. Certain combinations of fluids are
considered "ideal solutions," and Raoult's law can be used to estimate
vapor concentration. Raoult's law states:
P Y = P X [7]
t p vp p
Basically this infers a value of unity for the liquid phase activity co-
efficient in equation [2]. Raoult's law is usually followed by: (1)
members of homologous series in combination (e.g., propane, butane,
straight chain alcohols, etc.); (2) combination of substances with similar
hydrogen bonding characteristics; and (3) all mixtures for any component
as it approaches 100 percent concentration. Thus Raoult's law would hold
for the water concentration in dilute solutions of priority pollutants in
water since the water mole fraction (or concentration) approaches 1. As
a first approximation, however, Raoult's law can be used for other sub-
stances at lower concentrations, recognizing there may be substantial
positive or negative deviations (activities of 0.3 to 20 are not uncommon).
More detail on estimating activity coefficients and deviations from
30
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Raoult's law is given in the Chemical Engineers Handbook and in
The Properties of Gases and Liquids.
For dissolved gases in solution, or for dilute solutions of a volatile
solute in a solvent, Henry's law states that the partial pressure of the
solute in the gas phase is directly proportional to the concentration in
the solution or:
P = K,, C . . [8]
p TI p,liq
where: K = Henry's law coefficient
Although this law would hold for most of the priority pollutants in
dilute solution, there are only few data available for coefficients for
priority pollutants. (Note that equation [8] is the same as equation [2] if
the Henry's law coefficient is the same as y p •) Additional information
P vp
on the applicability of Henry's law is given in the two references cited
above. Methods for estimating Henry's law coefficients are also available
in the literature.
From the methods described above, one can make rough estimates of
the vapor phase concentrations of priority pollutants and thus the effec-
tive dose rate for some representative priority pollutants at a range of
concentrations in water. Some typical results are shown in Table 5.
High vapor pressure compounds and those with high water concentrations
could result in significant inhalation values, if exposure is continuous.
Note that many of the priority pollutants, pesticides, PCB's, metals, have
low vapor pressures and, in general, only the low molecular weight or
short chain compounds have vapor pressures of one mm Hg or more. Thus for
most priority pollutants at concentrations of 1 ppb or less, inhalation in-
take even for continuous exposure should be below 1 ug/day. However, each individual
chemical and exposure condition should be examined independently in risk
assessments.
31
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Table 5
Chemical
Chloroform
Benzene
to
Phenol
Chlordane
Estimated Vapor Concentration and Inhalation Intake
for Representative Conditions
Vapor
Pressure
(mmHg @
approx 25°C)
200
100
0.35
io-5
Water
Concentration
1 PPt
1 PPb
1 ppm
10 ppm
1 ppt
1 ppb
1 ppm
10 ppm
1 ppt
1 ppb
1 ppm
10 ppm
1 ppt
1 ppb
1 ppm
10 ppm
Estimated
Vapor
Concentration
(gm/liter)
1.93 x 10~13
1.93 x IO"10
_7
1.93 x 10 '
1.93 x 10~6
.966 x IO"13
.966 x 10~10
.966 x 10~7
.966 x IO"6
.338 x 10~15
.338 x 10~12
.338 x 10~9
.338 x 10~8
.966 x 10"2°
.966 x IO"17
.966 x IO"14
.966 x 10~13
Estimated
Vapor
Concentration
(mg/m3)
1.93 x 10~?
1.93 x 10~4
_i
1.93 x 10
1.93
.966 x 10~7
.966 x 10~4
.966 x 10"1
.966
.338 x 10~9
.338 x 10~6
.338 x 10~3
.338 x IO"2
.966 x 10~14
.966 x 10~U
.966 x 10~8
.966 x 10~7
Daily
Inhalation
Intake*
(mg)
2.78 x 10
2.78 x 10
27.8
278
-5
-2
1.39 x 10
1.39 x 10
13.9
139
-5
i
-2
4.87 x 10
4.87 x 10
4.87 x 10
.487
-8
-5
-2
1.39 x 10
1.39 x 10
1.39 x 10
1.39 x 10
-12
-9
-6
-5
Assumes 24-hour exposure at a ventilation rate of 6 m3/hr.
-------
In addition to breathing vapors from water containing priority
pollutants, persons may be exposed to priority pollutants by breathing
fog or mist generated from polluted water sources. The quantity of
pollutant inhaled by an individual will depend upon the ventilation rate,
duration of exposure to fog or mist, and the quantity of pollutant in
the fog or mist. The inhalation rate has already been considered. To be
conservative, one can assume that any pollutant inhaled in a fog or mist
remains in lungs and is absorbed into the body. The duration of exposure
to fog or mist will vary greatly depending upon occupational, geographical,
and climatological factors. In this program we could not develop gener-
alized exposure estimates because of this variability. However, one can
make estimates of the quantities of pollutants contained in fog or mist
for subsequent use in specific exposure/risk calculations.
The quantity of priority pollutant contained in a fog or mist depends
upon both the number and size of droplets or particles of water in the
fog or mist and the concentration of the pollutant in the droplets or
particles. Each of these factors will depend upon the mechanism of
generation of the fog or mist. For example, if contaminated water
vaporizes and subsequently condenses into a fog or mist, the size and
loading of the particles will depend upon atmospheric conditions. Further-
more, the concentration of pollutant in the droplets or particles will,
in general, be less than that of the original contaminated water because
of the fractionation process that has occurred. If contaminated water
is mechanically formed into a fog or mist, the particle size and loading
might be different from a condensing fog and the concentration of the
pollutant in the particles or droplets might be the same as in the
original source. The latter case represents an upper limit of the
quantity of pollutant inhaled, assuming that the pollutant generally has
a lower vapor pressure than water and is initially in a relatively low
concent rat ion.
The water content of fog has been studied by Radford who related
liquid water content to visibility. In practical terms, Radford finds,
as expected, an inverse relationship between liquid water content and
33
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horizontal visibility. Visibility of 3000 ft is consistent with a liquid
water content of 0.02 gm/m3; visibility of 100 ft is consistent with a
water content of 2 gm/m . Another estimate of the maximum moisture content
of fogs can be obtained by assuming the air to be saturated at
some temperature between the ambient air temperature and the water
temperature from which the fog is formed. For example, saturated air
Q
at 35°F contains about 5.8 gm/m water vapor whereas saturated air at
90°F contains about 36 gm/m . Thus if a 90°F saturated air stream were
cooled to form a saturated fog at 35°F, the water particles in the fog
could amount to almost 30 gm/m if the water droplets do not settle out.
For estimating purposes, we might consider fogs to contain a maximum
o
of 5 gm/m liquid water (corresponding to Radford's horizontal visibility
3
of 55 ft or 16.7 meters). Thus a person inhaling 6 m /hr of fog or mist
might inhale 30 gm of water per hour (clearly much of this will be ex-
haled) . At a pollutant concentration in the mist or fog equal to that
in the polluted water (a maximum case) the amount of pollutant inhaled
could be 0.03 mg/hr at a concentration of 1 ppm or .03 ug/hr at a pollu-
tant concentration of 1 ppb.
Comparison with Table 5 shows that inhalation of fog of water drop-
lets containing phenol at 1 ppm for one hour would give about the same
order of magnitude intake as breathing vapor for 24 hours from a water
source polluted with 1 ppm phenol. For lower vapor pressure pollutants,
breathing a mechanically produced fog for a short period of time could
result in a higher intake than prolonged breathing of vapor from the
contaminated source.
Clearly these estimates are not very precise but suggest that fog
or mist inhalation could be a significant source for some pollutants
and exposure conditions.
34
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C. SKIN ABSORPTION
A great deal of research has been done over the years on the process
of percutaneous transport of compounds; however, much of the work has been
clinically oriented and very little physical/chemical data have been
developed to enable accurate prediction of the rates of penetration and
permeation through the skin. From a brief review of the literature we
conclude the following.
The process of percutaneous absorption results from a combination of
adsorption onto the stratum corneum (the thin coherent membrane of
epithelial cells that comprise the "dead" surface layer of the epidermis).
diffusion through it and through the viable epidermis, and through the
papillary dermis into the microcirculation.
In general, diffusion through the stratum corneum is the rate-limit-
ing step.
The diffusion of solutes in water solution through the stratum corneum
may result from two mechanisms: (a) diffusion concurrent with solvent
transport or (b) a combination of preferential absorption on the stratum
corneum and diffusion through it.
A review article by Scheuplein and BlaiR provides equations and
data to estimate the order of magnitude of transport through the skin.
Considering the first mechanism, the diffusivity of the skin has been
measured and found to vary with location on the body. However, the thick-
ness of stratum corneum also varies, and the complementing effect of in-
creasing diffusivity with increasing thickness seems to yield a relatively
uniform steady state permeability and flux through the skin. The water
2 ^18)*
flux through the skin is approximately 0.2 to 0.5 mg/cm hr. The flux
of the solute (priority pollutant) could be estimated by multiplying this
water flux by the weight fraction of pollutant in the water. Thus at a con-
centration of 1 ppm, the flux of pollutant would be 0.2 x 10 to 0.5 x 10
*In this review article, several references to water flux through the skin
show different values ranging from 0.2 to 0.9 mg/cm^ hr for the abdomen,
back, forearm, etc., and even higher values for the palm, sole, scrotum, etc.
In another article, Galey (et al.)^) report the diffusivity of water in
whole human skin to be 4.4 + 1.7 x 10~7 cm/sec. The corresponding flux
value would be about 1.6 mg/cnn hr.
35
-------
2 —9 —9 2
mg/cm hr; at 1 ppb, the flux would be 0.2 x 10 to 0.5 x 10 mg/cm /hr.
2 42
Since a representative body surface area is about 1.8 m or 1.8 x 10 cm ,
the pollutant flux for twenty-four hour exposure might be on the order of
8.6 x 10" to 21.5 x 10~2 mg/day or 8.6 x 10~5 to 21.5 x 10~5 mg/day at
pollutant concentrations of 1 ppra and 1 ppb, respectively.
Considering the second mechanism which includes preferential absorp-
tion on the stratum corneum, and diffusion through it, the flux of solute
(priority pollutant) through the skin is given by the following equation:
K DAC
J
s 6 p s
where :
2
J = steady state flux of solute (moles/cm hr)
S
K = membrane/solvent partition coefficient =
m
solute sorbed per cc tissue _
solute in solution per cc solvent
2
D = average membrane diffusion coefficient (cm /hr)
5 = membrane thickness (cm)
AC = concentration difference of solute across membrane
(moles /cm^)
k = permeability constant for solute (cm/hr)
P
In examining equation [9] we see that the key variables affecting
the flux of pollutant through the skin are the concentration of pollutant
in the water (for practical purposes we can assume that the concentration
of the pollutant in the body is zero, so that the flux is directly propor-
tional to the pollutant concentration in the water) , and the permeability
constant for the solute. As noted above, the membrane diffusion co-
efficient and the skin (membrane) thickness seem to be mutually dependent,
so that the key variable may be the membrane (skin) /solvent (water)
partition coefficient.
36
-------
If data were available, equation [9] could be used to estimate the
flux (effective dose rate) of priority pollutants. In our brief litera-
ture search, we could not find the needed permeability or diffusion data
for the priority pollutants, and only limited data for other substances.
(The data seem to be of interest primarily to the pharmaceutical/cosmetics
industry and to the military.) Some typical values of the diffusion and
permeability coefficients and ranges of values of flux rates for several
water concentrations are given in Table 6. Note that the values estimated
by transport of solute through the stratum corneum by equation [9] are the
same order of magnitude (actually both smaller and larger depending upon
the chemical) as those estimated from diffusion of the solvent containing
the solute. This suggests that accurate estimates of the skin absorption
must take into the importance of K , the membrane (skin)/water partition
m
coefficient.
Since octanol seems to have a very high value of K. , it is plausible
that substances similar to octanol would also have a high value of K and
0 m
a possibly high permeability constant, k . This also suggests that
P
chemicals with a high octanol/water partition coefficient, might also have
a high membrane/water partition coefficient and a high permeability constant
for human tissue. Unfortunately, sufficient data are not available on
chemicals other than straight chain alcohols to support this hypothesis.
37
-------
Table 6
Chemical
Aqueous Solutions
Methanol
Ethanol
Butanol
Octanol
Ethyl Ether
2-Butanone
2-3 Butane diol
Progesterone
Cortisone
Hydrocortisone
Estradiol
Amphetamine
Ouabain
Representative Values of Skin Absorption Parameters and Rates
Tissue/
Permeability
Constant (k )
(cm/hr) p
0.5 x IO"3
0.8 x 10~3
2.5 x 10~3
52 x 10~3
16 x 10~3
4.5 x 10~3
.05 x 10~3
1.5 x 10~3
.01 x 10~3
.003 x IO"3
1.1 x 10~6
-,-j
0.039 x 10
0.011 x 10~7
Diffusion Co-
efficient (D)
(cm2/sec)
.62 x IO"9
.66 x 10~9
.74 x 10~9
.77 x 10~9
io-9
io-9
io-10
2 x ID'11
1 x IO-12
3 x 10~13
_
-
-
Solvent
Cone. Ratio
0.6
0.9
2.5
50
12
3.4**
.37**
55**
7.4**
7**
_
-
—
Flux through Skin at
1 ppm 1 ppb
(mg/cm^hr)
.5 x 10"6 .5 x 10~9
.8 x 10"6 .8 x 10"9
ft Q
2.5 x 10 2.5 x 10 *
fi Q
52 x 10" 52 x 10~
-6 -Q
16 x 10 16 x 10
4.5 x 10~6 4.5 x 10~9
.05 x 10~6 .05 x 10~9
£. Q
1.5 x 10~b 1.5 x 10
-ft -9
.01 x 10 .01 x 10
f Q
.003 x 10 .003 x 10
1.1 x 10~9 l.l x 10"12
-10 -1?
0.39 x 10 U l.l x 10.
0.011 x 10"10 1.1 x 10'12
Effective Dose Rate at
1 ppm 1 ppb
(mg/day)*
2.16 x Hf1
3.45 x 10~L
1.08
22.5
6.9
1.9
_o
2.16 x 10
•I
6.5 x 10
-3
4.3 x 10
Q
1.3 x 10 °
4.7 x 10~4
-4
4.7 x 10
4.7 x 10"4
2.16 x 10~4
3.45 x 10~4
1.08 x IO"3
-3
22.5 x 10
6.9 x 10"
1.9 x IO"3
-5
2.16 x 10
-4
6.5 x 10
. _ _ «~6
4.3 x 10
-6
1.3 x 10
4.7 x 10~7
-7
4.7 x 10
4.7 x 10~7
* 2
Calculated for continuous exposure of the entire body (1.8 m ) for 24 hours.
**
Estimated using a tissue thickness of 27 microns.
Source: References 18 and 19.
-------
VI. APPLICATION OF METHODOLOGY TO CHLORDANE AND
HEPATACHLOR RISK ASSESSMENTS
The methods described above can be used to estimate the "average
daily intake" of chlordane and heptachlor by inhalation and skin adsorp-
tion and compare these values to the average daily intake of these chemi-
cals by food and water ingestion. In this way one can determine the
significance of the non-ingestion routes.
Table 7 gives data from earlier assessments pertinent to the discussion.
The average daily intakes of heptachlor from food and chlordane from
drinking water were 0.3-0.64 ug/day and 0.01-0.02 ug/day. respectively. The
range of ambient water concentrations of the same chemicals was 5-50 ppt
and .01 to 1 ppb, respectively.
Table 7
Data From Chlordane and Heptachlor
Risk Assessments
Chlordane
Heptachlor
Heptachlor Epoxide
Average Daily Intake
(ug/day)
Ambient Water
Concentration Range
.01-1 ppb
5-50 ppt
7-70 ppt
Food
.002-. 007
-.3 to .64
-
Drinking
Water
.01-. 02
<.006
—
Assuming that a person was continuously exposed to vapor from water
containing these chemicals, the effective dose rate for inhalation can be
estimated from equation [6] in Section V, and assuming Raoult's law to
*
hold with the following results:
39
-------
25°C
Chlordane
Heptachlor
Heptachlor
epoxide
~
mmHg
-4
3 x 10 mmHg
2.6 x 10
mmHg
-6
Estimated Vapor -
Concentration (mg/m )
.966 x 10~13 at
.01 ppb liq cone
1.45 x 10~12 at
5 ppt liq cone
2.5 x 10~14 at
10 ppt liq cone
Daily
Inhalation
Intake
(ug/day)
1.39 x 10
-8
2.1 x 10
-7
3.6 x 10
-9
Thus inhalation of vapor in equilibrium with ambient water containing
low levels of chlordane, heptachlor and heptachlor epoxide yields only
negligible intakes of the chemicals compared to that obtained from food
ingestion. Even if the activity of the compounds in water were high (say
50 to 100) the quantity inhaled would still be small. Only if a mist or
fog from water contaminated with chlordane were breathed continuously were
breathed continuously could this inhalation source of pollutant be significant.
For skin adsorption of these chemicals, several estimates can be made.
It was shown in Section V that the adsorption flux of water (for entire
body surface) would range from about 3.6 g/hr to 9 g/hr. At ambient
concentrations of chlordane, heptachlor and heptachlor epoxide, the follow-
ing effective dose rates could occur.
Chlordane
Heptachlor
Heptachlor
epoxide
3.6-9 x 10 6 mg/hr @ 1 ppb to 3.6-9 x 10 8 mg/hr @ .01 ppb
1.8-4.5 x 10~8 mg/hr <§ 5 ppt to 1.8-4.5 x 10~7 mg/hr @ 50 ppt
2.5-6.3 x 10"8 mg/hr @ 7 ppt to 2.5-6.3 x 10~ mg/hr @ 70 ppt
Thus for total exposure for 24 hours/day, skin absorption rates would
be as follows:
Chlordane .08 ug/day to .22 ug/day @ 1 ppb
.0008 ug/day to .0022 ug/day @ .01 ppb
Heptachlor .0004 ug/day to .0011 ug/day @ 5 ppt
.004 ug/day to .011 ug/day @ 50 ppt
40
-------
-4 -3
Heptachlor epoxide 5.6 x 10 ug/day to 1.5 x 10 ug/day @ 7 ppt
.0056 ug/day to .015 ug/day @ 70 ppt
Thus continuous exposure to water containing heptachlor or heptachlor
epoxide at ambient levels might result in daily skin adsorption intakes
only about 1 to 5% of that from food ingestion, i.e., .015 ug/day skin
absorption compared to 0.3-0.64 ug/day food ingestion.
For chlordane, however, skin absorption seems to be a potentially
significant mechanism if the ambient water contains 1 ppb chlordane. The
estimates above were based on continuous 24 hour total surface exposure
to water containing chlordane. Using the exposure data of Section 4, one
could develop better estimates of average intake by skin absorption. For
example, for bathing the exposure was 46 hours/year or .126 hrs/day; thus
the average daily skin absorption of chlordane from bathing would be from
-4 -3
4.2 x 10 to 1.1 x 10 ug/day. This may be as much as 10% of the average
daily intake from food and drinking water. Dishwashing for 365 hours per
year, i.e., 1 hour/day would give about the same average daily skin absorp-
tion intake because only about 10% of the body is exposed. Although the
"average" daily intake by skin absorption seems to be only as much as 10%
of the average daily food intake, certain activities could give high
specific daily intakes. For example, if one swam for 4 hours in any given
day in water containing 1 ppb chlordane, from .013 to .036 ug chlordane
might be adsorbed, an amount comparable with the average dally food intake.
In Section V another method was given for estimating skin absorption,
i.e., use of equation [9]. If chlordane had the same permeability constant
as cortisone (they have similar molecular weights but very different
structures) about .004 ug/day could be absorbed for total continuous 24-
hour exposure at 1 ppb, a value somewhat smaller than the .08 to .22 ug/
day estimated above, but still not negligible compared to chlordane
food and drinking water ingestion. If chlordane had a permeability constant
more nearly equal to that of progesterone or an alcohol, from .6 to
1 ug/day might be adsorbed at concentrations of 1 ppb for 24 hours total
exposure.
41
-------
These results indicate that skin absorption of chlordane cannot be
neglected entirely, and suggests that additional effort be devoted to
understanding the mechanisms of skin absorption and developing data for
absorption of priority pollutants. It becomes particularly important
when considering subpopulations who have high exposure for prolonged periods
to water which may be contaminated with priority pollutants.
42
-------
REFERENCES
1. Day, R., "Regional Heat Loss," pp 240-261 in: Newburgh, L.H. (ed.)
(1949) Physiology of Heat Regulation and the Science of Clothing.
W. B. Saunders Co., Philadephia.
2. U.S. Bureau of Census (1975), Current Housing Reports, Series H-lll.
As quoted in Statistical Abstract (1976).
3. U.S. Bureau of Census (1975), Annual Housing Survey; 1975, Part A,
Series H-150-75. As quoted in Statistical Abstract (1976).
4. Anon. (1976) Merchandising. Annual Statistical issues. Billboard
Publications, Inc., New York, N.Y.
5. Federal Energy Administration (1977) Energy Efficiency Program for
Appliances. Final Report. By Booz-Allen and Hamilton, Inc.
6. U.S. Bureau of Census (1976) Current Population Reports, Series P-25,
Nos. 310, 371, 519, 643 and 704. Dept. of Commerce, Washington, D.C.
7. Craft, George (May 30, 1978), Personal communication. Technical
Services, American Water Works Association, Denver, Colorado.
8. U.S. National Center for Health Statistics (1975), Vital and Health
Statistics, Series 10, No. 115.
9. Arthur D. Little (1977) Study of Energy-Saving Options for Refrigerators
and Water Heaters, Vol. 2: Water Heaters. Prepared for Federal
Energy Administration, Washington, D.C.
10. Personal communication with staff at New England Rehabilitation Center,
Woburn; Otis Hospital, Cambridge; Tufts-New England Medical Center,
Boston; Syrames Hospital, Arlington; Milton Hospital, Milton.
11. American Hospital Association (1977), Hospital Statistics 1976,
Annual Survey.
12. U.S. Dept. of Interior (1973) Outdoor Recreation; A Legacy for
America. Bureau of Outdoor Recreation, Washington, D.C.
13. U.S. Dept. of Interior (1977), 1975 National Survey of Hunting. Fishing.
and Wildlife—Associated Recreation. U.S. Fish and Wildlife Service,
Washington, D.C.
14. Comroe, Julius H. (1966), Physiology of Respiration, Year Book Medical
Publishers, Inc., Chicago, Illinois.
43
-------
15. Perry, J.H. (edit) (1950), Chemical Engineer's Handbook, 3rd Edition,
McQraw Hill, New York.
16. Reid, R.C. and Sherwood, T.K. (1958), McGraw Hill, New York,
The Properties of Gases and Liquids.
17. Houghton, H.G. and Radford, W.H., "On the Measurement of Drop Size
and Liquid Water Content in Fogs," Pap. Phys. Ocean Meteor. Mass.
Inst. of Tech., Woods Hole Ocean. Instn., Vol. 6, No. 4 (1938) as
reported in "Compendium of Meteorology," ed. by Thomas F. Malone,
American Meteorological Society, Boston, Mass. 1951.
18. Scheuplein, R.J. and Blank, I.H. (1971), "Permeability of the Skin,
Physiological Reviews, 51, No. 4, p702.
19. Galey, William R., Lonsdale, H.K., and Nacht, Sergio, "The In Vitro
Permeability of Skin and Buccal Mucosa to Selected Drugs and Tritiated
Water." The Journal of Investigative Dermatology, 67^713-717, 1976
20. Forbes, W.H., "Laboratory and Field Studies" (Chapter 11), pp320-388,
in: Newburgh, L.H. (ed.) (1949) Physiology of Heat Regulation and the
Science of Clothing. W.B. Saunders Co., Philadelphia.
44
-------
APPENDIX A
MATHEMATICAL APPENDIX
Definitions of Symbols
B = normal breathing
A = activity leading to exposure (e.g., swimming)
P = demographic subpopulation (e.g., children)
G = environmental category (e.g., coastal)
H = habitational category (e.g., urban)
J = occupational category (e.g., farmers)
W.(G,H) = source of water to which activity A is exposed.
MT(G,H) = fraction of total population having occupation J.
J
FA(P) = frequency of exposure for subpopulation P via
activity A. (hours/day)
F ,E * = frequency and extent of exposure for occupation J.
J J
EA*(P) = extent of exposure for P via A.
N(P) = fraction of general population falling in subpopulation P.
POP = total population of U.S.
Q(G,H) = fraction of general population falling in this category.
R(P) = ventilation rate for subpopulation P (m. /hr.)
* For dermal route, extent = dermal factor (0-1)
A-l
-------
Exposure Computations
1. Activities
D (P) = degree of exposure for member of P through activity A.
= EA(P) ' FA(P) for dermal
A A
= R(P) • FA(P) for inhalation
X.(6,H,P) = exposure of subpopulation P in situation G,H as percent
of total population exposure
= N(P)'Q(G,H)'DA(P)
T
X. = total exposure of general population to water source T via
A
activity A
= POP • E. [X (G,H,P): W (G,H) - T]
G.H.P A
XA
= total exposure via activity A (person-hours/day)
= E x?
2. Occupations
DT = degree of exposure in occupational category J.
u
EJ j for dermal
= R (adult) • Fj for inhalation
X, = exposure in occupational category J to water Source T
POP [MT(G,H)D. : WT(G,H) = T]
G,H J J J
X. = total exposure in occupation J (person-hours/day)
•% T
T J
A-2
-------
3. Inhalation (Adjustment for Occupational Exposure)
F0(P) - 1 - Z»F.(P) where the summation includes only activities
A
for which inhalation occurs
DBR(P)1
J
x£ = POP • £ [XB(G,H,P) : WB(G,H) = T]
G.H.P
XB = Z *B (person-m.3/yr.)
T
4. Total exposure by water source
T
X = total exposure to water source T (person-hours)
ET* v* T
X. + 2-r X f°r dermal (person-hr . /yr . )
J A
J A A
V V
T / I / T
-f x + X
j j
"\
for inhalation (person-m. /yr.)
Inhalation exposure through occupations and activities has been sub-
tracted from total exposure through breathing, so that there is no
redundancy in the above calculation.
X = total U.S. water exposure
XT
A-3
-------
Effective Dose Rate and Risk Computations
Let physical/chemical properties of interest be designated as
(z z,...) = z
CT - Pollutant concentration in water source T
S(C ,30 = Effective dose rate
Y = Toxicity coefficient (excess risk/ppb)
then V. = average daily intake via A and T
= X* • S (CT,Z) and
R. = Risk from activity A
T A
Y
' Y
Similarly R = Risk in occupation J
J
-E* '
~ T J
. Y
Also R_ = Risk from normal breathing
X B . S (CT,Z) . Y
Also R = Risk from water type T
) - S(CT,Z) -
or R
(dermal)
(inhalation)
A-4
-------
Hence, total risk to U.S. population is given by
R=£RT or R-5 RA
Note that if the concentration C depends on location, the
above computations may be suitably modified.
A-5
-------
APPENDIX B
BOATING
(12)
Sailing
Canoeing
RECREATIONAL SUBPOPULATION EXPOSURES*
Population
Sex ,
males 5 x 10
females 3 x 106
Age (yrs1*
12-17 2 x 106
18-24 2 x 106
25-44 2 x 106
45-64 2 x 106
65+ .3 x 106
Residence
in SMSA 5 x 106
not in SMSA 3 x 10*
Region
Northeast 3 x 106
North Central 2 x 106
South 2 x 106
West 1 x 106
Sex
males 6 x 106
females 4 x 10&
Age (yrs)
12-17 2 x 106
18-24 3 x 106
25-44 4 x 106
45-64 1 x 106
65+
Residence f
in SMSA 6 x 10°
not in SMSA 4.8 x 106
Total
Exposure
(person-hours)
150 x 106
114 x 106
83.2 x 106
40.8 x 106
52.8 x 106
99.2 x 106
2.4 x 106
136.0 x 106
136.8 x 106
139.2 x 106
33.6 x 106
29.6 x 106
52.4 x 106
120 x 106
46.4 x 106
41.6 x 10J?
45.6 x 10?
44.8 x 10*
32.8 x 10°
1.36 x 10
91.2 x lOJ?
76.8 x 10°
T*he subpopulations may not add up exactly to the total given in Table 5
because of rounding errors. Further, the precision of the estimates is not
as great as might be perceived from the values given here. Most likely, the
the estimates are only precise to two significant figures.
B-l
-------
Population
Total
Exposure
(person-hours)
Other Boating
Region ,
Northeast 3 x 10
North Central 4 x
South 2 x 10°
West 1 x 10°
Sex ,
Males 25 x 10b
Females 25 x 106
Age (yrs) ,
12-17 11 x 10
18-24 9 x 10*
25-44
45-64
65+
19 x 10
11 x 10*
2 x 106
74.4 x 10*
44.8 x 10°
32.8 x 10°
12.0 x 10°
630.0 x 10
480.0 x 10
6
224.4 x 10
144.0 x 10:
448.4 x lO;
268.4 x 10*
57.6 x 10°
Residence
in SMSA 31 x 10°
not in SMSA 19 x 10*
669.6 x 10,
425.6 x 10*
FISHING
(13)
Region ,
Northeast 11 x 10
North Central 13 x
South 17 x 106
West 10 x 106
9-17 years t
men 8.9 x 10 ,
women 3.4 x 10
18-24 years ,
men 4.2 x 10
women 2.2 x 10b
25-34 years ,
men 7.9 x 10 ,
women 3.8 x 10
35-44 years ,
men 5.1 x 10 ,
women 2.5 x 10
45-54 years ,
men 4.7 x 10°
women 1.9 x 10e
55+ years ,
men 3.5 x 10 ,
women 2.5 x 10
224.4 x 10'
306.8 x 10'
367.2 x 10*
220.0 x 10*
1090.3 x 10
416.5 x 10
514.5 x 10*
269.5 x 106
967.8 x 10*
465.5 x 10
624.8 x 10*
306.3 x 10
575.8 x 10*
232.8 x 10°
428.8 x 10*
306.3 x 10
B-2
-------
SWIMMING
(12)
Outdoor pool
swimming
Population
Sex 6
male 31 x 10 ,
female 34 x 10
Total
Exposure
(person-hours)
477.4 x 10
693.6 x 10
Age
12-17
18-24
25-44
45-64
65+
6
21 x 10°
12 x 10^
21 x lg6
9 x 10^
1 x 106
537.6 x 10'
160.8 x 10f
331.8 x 10;
117.0 x 10
10.8 x 106
Residence ,
in SMSA 46 x 10°
not in SMSA 19 x 10*
901.6 x 10;
269.8 x 10*
Region
Northeast 20 x 10°
North Central 16 x 10e
South 18 x 106
West 10 x 106
368.0 x 10C
313.6 x 10*
252.0 x 10:
220.0 x 10e
Other swimming
outdoors
Sex
male 57 x 10 ,
female 59 x 10
1071.6 x 10"
1038.4 x 106
Age (years)
12-17
18-24
25-44
45-64
65+
30 x 10;
24 x 10*
44 x 10*
16 x 10*
2 x 10*
672.0 x
446.4 x 10
712.8 x 10
256.0 x 10
32.4 x 106
Residence
in SMSA 79 x 106
not in SMSA 37 x 10°
Region
Northeast 38 x 106
North Central 24 x 10e
South 34 x 106
West 20 x 106
1311.4 x 10
799.2 x 106
767.6 x 10°
350.4 x 106
598.4 x 106
392.0 x 106
B-3
-------
Total
Exposure
Population (person-hours)
Waterskiing< Sex ,
male 10.8 x 10? 159.8 x 10°
female 9.1
.
x 10 96.5 x 106
Age (years) ,
12-17 5 x 10° 97.0 x 10°
18-24 6 x 10° 67.2 x 10b
25-44 8 x I0j 91.2 x 10°
45-64 1 x 106 7.8 x 106
65+ Ox 106 0
Residence , ,
In SMSA 12 x 10° , 168.0 x 10
not in SMSA 8 x 10 92.8 x 10b
Region ,
Northeast 4 x 10° 44.0 x 10°
North Central 5 x 106 48.0 x 10b
South 7 x 106 84.0 x 106
West 4 x 106 87.2 x 106
B-4
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-440/4-79-016
3. RECIPIENT'S ACCESSION NO.
». TITLE AND SUBTITLE
Identification and Evaluation of Waterborne Routes of
Exposure -From Other Than Food and Prinking Hater
5. REPORT DATE
January. 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Kate Scow1
Melba Wood
i
Alfred E. Wechsler1, Janet Stevens1,
Michael A. Callahan2
8. PERFORMING ORGANIZATION REPORT NO
». PERFORMING ORGANIZATION NAME AND ADDRESS
Arthur D. Little, Inc.
Acorn Park
Cambridge, Massachusetts 02140
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA-68-01-3857
Task #4
12. SPONSORING AGENCY NAME AND ADDRESS
2U.S. Environmental Protection Agency
Office of Water Planning and Standards
Monitoring and Data Support Division (WH-553)
Washington. D.C. 20460
13, TYPE OF REPORT AND PERIOD COVERED
Final Task Report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The purposes for this task were (1) to identify major human exposure routes
(other than food and drinking water) for waterborne pollutants; (2) to develop a
methodological framework for establishing the significance of these routes for
quantifying the risks to humans associated with these routes; and (3) to incorporate
this framework into a risk assessment methodology and test its usefulness for risk
assessments of chlordane and heptachlor. Inhalation of vapors from polluted water
and absorption of pollutants through the skin during direct contact with water were
chosen as the most significant alternative exposure routes for consideration In this
report. The process of estimating water exposure consists of (1) identifying human
activities that can result in exposure; (2) identifying subpopulations involved in
these activities; (3) assessing activity duration or degree of daily exposure to
the different sources of water; and (4) summation of average daily exposures for
different subpopulations. Seventeen exposure activities (bathing, dishwashing, etc.)
in personal, recreational, and household categories were identified. Estimates for
these activities were made of average daily exposure by inhalation or skin absorption
routes, exposure extent, and total national yearly exposure, with subpopulations
identified by age, sex, and geographic location in several cases. Calculations for
chlordane and heptachlor showed inhalation to be negligible compared to other Intakes,
but for chlordane, skin absorption may be a significant exposure route.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Risk
Exposure
Water pollution
Public health
Chlordan
Heptachlor
06F
G8G
57H
8. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
58
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
PA Form 2220-1 (t-73)
-- U.S. GOTDWMlin FKINTWGOfTICE 1979-281-147/49
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