appended to those parameters that are specific to the pollutant. The derivation of E k proceeds from Equations 5-8 (with appropriate additions of subscript k and deletion of the consumer product sum) and the relations cF,k
= CA,hfAF,h-k CW,hfWF,k
CW,k = fAW,kCA,k and with the last being substituted into Equation 16 to obtain Equation 19. I t should be noted that the interaction characterized by B12 is biological rather than environmental. The derivation of E k (Equation 20) assumes independent transport of the two chemical species through the environment, an assumption that may be false for some pairs of pollutants. From the foregoing discussion, we see that each critical air concentration pair (CA,J, C A , ~lies ) on the curve defined by Equation 19. Moreover, when a concentration pair converts Equation 19 into a >1inequality, the image burdens (Q1, Qz) in the reference organ lie outside the shaded region in Figure 2, which implies unacceptable composite levels. The above analysis applies for multiple pollutants in one sampling medium which produce the same biological effect. The application may be extended to incorporate multiple effluent types and multiple sampling media in a manner similar to that given above for single pollutants. Multiple Pollutants, Different Biological Effects. The discussion of multiple pollutant effects given above applies strictly only if the multiple pollutants affect the same target organ and influence the same biological effects. If the pollutants affect different organs or produce different biological effects in the same or different organs, then other considerations must be included in the model. For example, each pollutant may have to be weighted according to its influence on the total well being of the organism. Research along such lines should eventually lead to a comprehensive approach for determination of composite hazard indices. Conclusions I t is conceptually feasible to determine multimedia, mul-
tipathway, and multipollutant composite hazard indices such that control of pollutant concentrations in one or two sampling media (corresponding to one or more effluent modes) will assure that total human intake will not exceed some preselected value. These composite hazard indices are site specific in terms of emission sources and sampling media, but there is no conceptual barrier to determination of indices for multiple sources as well as multiple pathways to the sampling medium. Composite hazard indices conceptually provide an interface between human exposure assessments and human health risk assessment. Their practical determination, however, requires detailed knowledge of source emission characteristics, environmental transport processes, metabolism in man, and biological effects. Thus composite hazard indices provide a framework to assimilate such knowledge and to point out where more research is needed. Their application will be more definitive as information develops; however, it is certain that such concepts will have to be applied conservatively before all desired information is available. Literature Cited (1) Booth, R. S., Kaye, S. V., Rohwer, P. S., “A Systems Analysis
Methodology for Predicting Dose to Man from a Radioactivity Contaminated Terrestrial Environment”, Proceedings of Third International Symposium on Radioecology, AEC-CONF-710501, 1971. (2) Killouah. G. G.. McKav, L. R., “A Methodoloev for Calculating Radiation Doses from Radioactivity Released to ;he Environment’? ONRL-4992,1976. (3) R u m . E. M.. Parzvck. D. C.. Walsh. P. J.. Booth. R. S.. Raridon. R. J.: Whitfield, B. L., Enuiron. Sei. Technol., 12,802 (1978). (4) National Science Foundation, Washington, D.C., “Chemicals and Health”, Report of the Panel on Chemicals and Health of the President’s Science Advisory Committee, Science and Technology Policy Office, 1973. ( 5 ) Vandegrift, A. E., Shannon, L. J., Gorman, P. G., Lawless, E. W., Sallee. E. E.. Reichel. M.. “Particulate Pollutant System Studv. Volume I-Mass Emissions”, Midwest Research Institute, 197i, NTIS P B 203 128, Springfield, Va. 22151.
Receiued for review August 1 , 1977. Accepted January 13, 1978. Research sponsored by the Department of Energy under contract with Union Carbide Corp.
Composite Hazard Index for Assessing Limiting Exposures to Environmental Pollutants: Application Through a Case Study Elizabeth M. Rupp’, Dennis C. Parzyck’, Phillip J. Walsh’”, Ray S. Booth2, Richard J. Raridon3, and Bradford L. Whitfield4 Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tenn. 37830
Application of the composite hazard index assessment methodology ( I ) requires implementation of atmospheric, terrestrial, and aquatic transport models and selection of an exposure or dose limit that should not be exceeded because of health risk to man. Models in present use a t Oak Ridge National Laboratory for this purpose are: an atmospheric transport model (ATM), based on a Gaussian plume model (2, 3 ) capable of predicting wet and dry deposition and air concentration of gaseous and particulate pollutants a t various receptor points located within 50 km of a source or sources; Health and Safety Research Division. Instrumentation and Controls Division. Computer Sciences Division. Environmental Mutagen Information Center. 802
Environmental Science & Technology
a terrestrial transport model, TERMOD ( 4 , 5 ) ,which uses the output of ATM in pg/mZ/day of pollutant deposition on soil and plants as inputs and yields intakes of pollutants by man through consumption of milk, beef, and plant parts; and an aquatic transport model, AQUAMOD ( 6 ) ,which is being developed to simulate pollutant flow through aquatic food chains. The human exposure or intake determination, based upon transport models, may be linked to the exposure concentration of dose limits for organs by physiological transport models. The physiological models used in each application will vary with the properties of the pollutant being studied. The model discussed by Friberg et al. and Kjellstrom (7,8) was used for the assessment of cadmium release described in this paper. Selection of an exposure, dose, or concentration limit de-
0013-936X/78/0912-0802$01 .OO/O
@ 1978 American Chemical Society
H The composite hazard index assessment methodology described in the previous paper is applied to cadmium releases from a smelter complex in East Helena, Mont. Environmental transport models are used to estimate cadmium dispersion through air, concentrations in air, deposition on soil and plant surfaces, uptake by plants, intake by animals, and human intake through inhalation and ingestion. A physiological model is used to estimate cadmium uptake and distribution
Table 1. Average Cadmium Concentrations Sample medium
U.S.( 7 )
Air (pg Cd/m) Water (pg Cd/L)
0.02 Urban 0.003 Nonurban
