Modeling of Human Exposure to Airborne Toxic ... - ACS Publications

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Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 15, 2018 | https://pubs.acs.org Publication Date: August 30, 1983 | doi: 10.1021/bk-1983-0225.ch004

Modeling of Human Exposure to Airborne Toxic Materials G. E . ANDERSON Systems Applications, Inc., San Rafael, CA 94903

Under contract to the Systems and Strategy Development D i v i s i o n of the OAQPS/EPA, Systems A p p l i c a t i o n s developed and a p p l i e d modeling methods f o r the e s t i m a t i o n of human exposure and dosage from airborne m a t e r i a l s . The model is intended f o r a screening a n a l y s i s of the impacts of chemicals under EPA review as p o t e n t i a l l y hazardous by the d e f i n i t i o n s of the NESHAPS program. The a n a l y s i s methods are n a t i o n a l in scope and address emissions from a wide v a r i e t y of i n d u s t r i a l and community source types. The m a t e r i a l s reviewed are o f widely d i s p a r a t e n a t u r e s . They include metals, and bulk and trace hydrocarbons, i n c l u d i n g c h l o r i n a t e d and oxide d e r i v a t i v e s of hydrocarbons. The analyses are intended to be p r e l i m i n a r y screening analyses f o r use i n scoping and prioritizing regulatory a t t e n t i o n t o t o x i c exposures from the chemicals studied. The modeling package, d e l i v e r e d t o the EPA, i n c l u d e s nationwide data bases f o r emissions, d i s p e r s i o n meteorology, and population p a t t e r n s . These data are used as input f o r a Gaussian plume model f o r point sources and a box model f o r urbanwide area sources. Prototype modeling is used f o r point sources that are too numerous t o d e f i n e i n d i v i d u a l l y . Building wake e f f e c t s and atmospheric chemical decay are addressed.

0097-6156/83/0225-0067$06.00/0 © 1983 American Chemical Society

Swann and Eschenroeder; Fate of Chemicals in the Environment ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

F A T E OF CHEMICALS I N T H E E N V I R O N M E N T

The modeling approach has r e c e n t l y been modified to a g r i d form so as to address problems of exposure from m u l t i p l e sources and/or m u l t i p l e chemicals simultaneously.


O r i g i n s of Atmospheric Risk A n a l y s i s T r a n s f e r s of m a t e r i a l s across t i s s u e surfaces exposed to the atmosphere are c r i t i c a l t o l i f e processes f o r humans, other animals, and p l a n t s . Thus, l i v i n g things are p a r t i c u l a r l y s u s c e p t i b l e t o harm by airborne i r r i t a n t s or t o x i n s . The r i s k of such harm has been a major m o t i v a t i o n f o r the development of techniques f o r the a n a l y s i s of atmospheric dispersion. Much of the i n i t i a l development of Gaussian modeling and d e f i n i t i o n of d i s p e r s i o n paramenters was done during and a f t e r World War I i n addressing the problem of poison gas dispersal. These s t u d i e s i n v o l v e d the d e f i n i t i o n of r i s k f a c t o r s , such as exposure and dose. The next i n t e n s i v e development e f f o r t came during and a f t e r World War I I with the nuclear weapons program. Airborne poisons i n the nuclear weapons progam were not l i m i t e d to r a d i o a c t i v e m a t e r i a l s r e l e a s e d from weapons. The weapons technology i n v o l v e d the use of many e x o t i c m a t e r i a l s , some of which were t o x i c (e.g., b e r y l l i u m ) . Hazardous r e l e a s e s of these m a t e r i a l s occurred i n i n d u s t r i a l s e t t i n g s i n urban areas and were studied by the Atomic Energy Commission as o c c u p a t i o n a l and p u b l i c h e a l t h problems. D e f i n i t i o n s and techniques of r i s k a n a l y s i s f o r atmospheric p o l l u t a n t s developed i n these m i l i t a r y and d e r i v a t i v e programs were d e s c r i b e d i n depth i n "Meteorology and Atomic Energy" (1). At the time that the weaponsr e l a t e d concerns were b e i n g c o d i f i e d , p u b l i c concerns f o r and governmental r e g u l a t i o n of the n a t i o n ' s s e v e r e l y d e t e r i o r a t e d a i r q u a l i t y was l e a d i n g t o the development of a g r e a t l y expanded array of a n a l y s i s techniques. Elements of Atmospheric R i s k A n a l y s i s Although s e l e c t i o n of the appropriate a n a l y s i s techniques i s o f t e n very problem s p e c i f i c , the b a s i c elements of human h e a l t h r i s k a n a l y s i s are few, as presented i n Figure 1. The f i g u r e shows that the aggregate r i s k to human h e a l t h from exposure t o an airborne p o l l u t a n t r e s u l t s from two factors: (1) the spread of the primary agent (and/or i t s transformation products) from i t s source(s) to contact w i t h people, and (2) the c h a r a c t e r i s t i c s of the agent's a c t i o n on the people who are exposed to i t . The u s e f u l e x p r e s s i o n of



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ANDERSON

Human Exposure Models: Airborne Materials

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the r i s k depends on j o i n t s t a t i s t i c a l c o n s i d e r a t i o n s of agent d i s p e r s i o n and c h a r a c t e r i s t i c s of the human r e c e p t o r s . Each of the main r i s k a n a l y s i s elements c o n s i s t s of three i n t e r a c t i v e s t u d i e s . Exposure estimates r e s u l t from the i n t e g r a t i o n of p o l l u t a n t d i s p e r s i o n p a t t e r n s and human population patterns. The d i s p e r s i o n patterns, i n t u r n , r e s u l t from the j o i n t a c t i o n of emissions and d i s p e r s i o n processes. The h e a l t h e f f e c t side of the diagram shows that u n i t r i s k estimates r e s u l t from i n t e r a c t i v e analyses of h e a l t h a f f e c t i n g processes i n the human body and observed e f f e c t s i n human populations (epidemiology). Health e f f e c t s are i d e n t i f i e d by i n t e g r a t i n g c l i n i c a l s t u d i e s on humans or animals with studies of p h y s i c a l and chemical responses t o p o l l u t a n t agents i n the human body. Weaknesses i n any of the r i s k - s t r u c t u r e " b u i l d i n g b l o c k s " l i m i t the c r e d i b i l i t y or usefulness of the r i s k estimates. Conversely, each c o n s t i t u e n t a n a l y s i s should, most a p p r o p r i a t e l y and e f f i c i e n t l y , be of comparable r i g o r and d e t a i l with regard to each other. Note, however, that the r e s u l t s of each b u i l d i n g block study are of value i n themselves. T h i s paper focuses on i s s u e s i n the " d i s p e r s i o n " block of Figure 1. These i s s u e s must be addressed, however, i n the context of a h e a l t h e f f e c t s problem. Some knowledge of the h e a l t h r i s k i s necessary to p r o p e r l y scope the exposure analysis. A h e a l t h r i s k f o r atmospheric p o l l u t a n t s i s based on the concept that adverse p h y s i o l o g i c a l changes may be produced i n human t i s s u e t h a t has contacted or absorbed some airborne m a t e r i a l . The change might depend—at l e a s t s t a t i s t i c a l l y — o n some c h a r a c t e r i s t i c s of the i n d i v i d u a l (e.g., age, sex, occupation, r a c i a l background), on the complete time p a t t e r n o f the p o l l u t a n t r e c e i v e d (amount of dosage r e c e i v e d over exposed time), and on any measure of that p a t t e r n . (Exposure i s t h e occurrence of contact between human and p o l l u t a n t s . Dose i s the t o t a l amount of material received. In t h i s paper the c o n c e n t r a t i o n to which a person i s exposed on an annual average b a s i s i s a measure of the p o t e n t i a l dose he may r e c e i v e . I n d i v i d u a l dose, summed over a l l exposed persons, i s r e f e r r e d to here as dosage.) P o l l u t a n t p a t t e r n s can be measured i n s e v e r a l ways: t o t a l dosage, dosage i n a given time, exposure at or above a given dose r a t e , and l i n e a r or nonlinear and continuous or noncontinuous f u n c t i o n s of any of the above measures. Appropriate methods of exposure a n a l y s i s depend on the form of the h e a l t h e f f e c t f u n c t i o n , which must be presumed to depend on some f u n c t i o n of the time h i s t o r y of concentration to which a person i s exposed. Even


Swann and Eschenroeder; Fate of Chemicals in the Environment ACS Symposium Series; American Chemical Society: Washington, DC, 1983. A6GREGATE R I S K

TATISTICAL CQNSIDERVTION FREGUENCY OF OCCURRENCE)

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Human Exposure Models: Airborne Materials Cited

David H. Slade, "Meteorology and Atomic Energy 1968;" A i r Resource L a b o r a t o r i e s , Environmental Science S e r v i c e s A d m i n i s t r a t i o n , U.S. Department of Commerce, 1968. U.S. EPA, D i s c u s s i o n a t EPA workshop on " P r e d i c t i v e Exposure Assessment," Washington, D.C. (unpublished), 6-7 April 1982. W. R. O t t , "Models of Human Exposure t o A i r P o l l u t i o n , " T e c h n i c a l Report No. 32, Department of Statistics, Stanford U n i v e r s i t y , Stanford, C a l i f o r n i a , 1979. T. Johnson and R. Paul, "The NAAQS Exposure Model (NEM) and I t s A p p l i c a t i o n t o N i t r o g e n D i o x i d e , " PEDCo Environmental, Inc., Durham, North C a r o l i n a , 1981. K. R. Peterson and T. F. Harvey, "Meteorology and Demography Models f o r Risk Assessments of A c c i d e n t a l Atmospheric Releases of Nuclear Waste Phase 2 Methodology," Lawrence Livermore Laboratory, Berkeley, C a l i f o r n i a , 1980. B. E. Suta, "Assessment o f Human Exposures t o Atmospheric Benzene from Benzene Storage Tanks," Center f o r Resource and Environmental Systems S t u d i e s , Report No. 119, SRI I n t e r n a t i o n a l , Menlo Park, C a l i f o r n i a , 1980. T. Johnson and J. Capel, " P o p u l a t i o n Exposure to Ozone i n the Northeast Corridor from May through October, 1979," PEDCo Environmental, Inc., Durham, North C a r o l i n a , 1980. G. E. Anderson, S. R. Hayes, M. J. Hillyer, J . P. Killus, and P. V. Mundkur, " A i r Q u a l i t y i n the Denver M e t r o p o l i t a n Region: 1974-2000," EPA-908/1-77-002, Systems A p p l i c a t i o n s , Inc., San R a f a e l , C a l i f o r n i a , 1977. T. W. Tesche and C. S. Burton, "Simulated Impact of A l t e r n a t i v e Emissions Control S t r a t e g i e s on Photochemical Oxidants in Los Angeles," RF78-22R, Systems A p p l i c a t i o n s , Inc., San R a f a e l , C a l i f o r n i a , 1978. S. R. Hanna, "A Simple D i s p e r s i o n Model f o r the A n a l y s i s of Chemically Reactive P o l l u t a n t s , " Atmos. E n v i r o n . 1973, 7, 803-817.

R E C E I V E D April 15, 1983.


Modeling of Human Exposure to Airborne Toxic ... - ACS Publications

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