Dependence of Intake Fraction on Release Location in a Multimedia Framework

A Case Study of Four Contaminants in North America

Authors

  • Matthew MacLeod,

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      Matthew MacLeod is a postdoctoral fellow in the Environmental Energy Technologies Division of the Lawrence Berkeley National Laboratory in Berkeley, California.

  • Deborah H. Bennett,

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      Deborah Bennett is an assistant professor of environmental health and risk assessment at the Harvard School of Public Health in Boston, Massachusetts.

  • Merike Perem,

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      Merike Perem is a research associate at the Canadian Environmental Modeling Centre, Trent University.

  • Randy L. Maddalena,

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      Randy Maddalena is a scientist in the Environmental Energy Technologies Division of the Lawrence Berkeley National Laboratory.

  • Thomas E. McKone,

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      Thomas McKone is a senior scientist in the Environmental Energy Technologies Division of the Lawrence Berkeley National Laboratory and an adjunct professor in the School of Public Health, University of California in Berkeley, California.

  • Don Mackay

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      Don Mackay is the Director of the Canadian Environmental Modeling Centre at Trent University, Peterborough, Ontario, Canada.


Matthew MacLeod Lawrence Berkeley National Laboratory One Cyclotron Road, 90R3058 Berkeley, CA 94720-8132 mjmacleod@lbl.gov

Summary

A defining feature of industrial ecology is the design of processes to minimize any disruption of the functioning of the natural ecosystem that supports life, including human beings. The extent of human exposure to anthropogenic contaminants in the environment is a complex function of the amount of chemical emitted, its physicochemical properties and reactivity, the nature of the environment, and the characteristics of the pathways for human exposure, such as inhalation, dermal contacts, and intake of food and water. For some chemicals, the location of emissions relative to areas of high population density or intense food production may also be an important factor. We explore the relative importance of these variables using the regionally segmented Berkeleyf-Trent (BETR) North America contaminant fate model and data for food production patterns and population density for North America. The model is applied to fourfff contaminants emitted to air: benzene, carbon tetrachloride, benzo-a-pyrene, and 2,3,7,8 tetrachlorodibenzo-pff-dioxin. The total continental intake fraction (iF), relating exposure quantity to emission quantity, is employed as a metric for assessing population exposure to these contaminants. Results show that the use of continentally averaged parameters for population density and food production provides an accurate estimate of the median of iF calculated for emissions in individual regions; however, iF can range from this median by up to 3 orders of magnitude, especially for chemicals transferred to humans through foods. The locations of population and food production relative to sources of chemicals are important variables that should be considered when assessing the possible human health impacts of chemical emissions as in life-cycle assessment.

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