Aggregate exposure

ILSl, A Framework for Estimating Pesticide Concentrations in Drinking Water for Aggregate Exposure Assessments, Workshop Report 5/19/99. International Life Sciences Institute, Washington, DC (1999). 

In the SRI report (2) the release information on benzene was used with atmospheric dispersion models and data on geographic distribution of population to obtain aggregate exposure estimates (shown in Table IV). 

Aggregate exposure to a pesticide from all dietary sources drinking water, residential and other routes must be taken into account ... 

For pesticides that pose human risks through a common biological mode of action (like the OP insecticides), aggregate exposures to all such pesticides must be evaluated together in determining whether a given... 

These data suggest that there are significant sources of exposure to these OPs other than those EPA identified as contributing most heavily to aggregate exposure. These might be additional crop uses in the USA or uses abroad, leading to exposures via imported foods. 

Although causal evidence in humans of the link between chemical exposure and cancer is quite limited, one might expect that greater aggregate exposure to chemicals in an increasingly industrial society would cause higher aggregate cancer rates over time. 

Wilson et al. (2003), studying the aggregate exposures of preschool children to persistent organic pollutants at day care and at home, reported that the indoor... 

Clayton, C.A., Pellizzari, E.D., Whitmore, R.W., Quackenboss, J.J., Adgate, J. and Sefton, K. (2003) Distributions, assodations, and partial aggregate exposure of pesticides and polynuclear aromatic hydrocarbons in the Minnesota Children s Pestidde Exposure Study... 

Pang, Y., Macintosh, D.L, Camann, D.E. and Ryan, P.B. (2002) Analysis of aggregate exposure to chlorpyrifos in the NHEXAS-Maryland investigation. Environmental Health Perspectives, 110, 235 10. 

Wilson, N.K., J.C. Chuang, C. Lyu, R. Menton, and M.K. Morgan. 2003. Aggregate exposures of nine preschool children to persistent organic pollutant at day care and at home. J. Expo. Anal. Environ. Epidemiol. 13(3) 187-202. 

Shurdut, B.A., L. Barraj, and M. Francis. 1998. Aggregate exposures under the Food Quality Protection Act An approach using chlorpyrifos. Regul. Toxicol. Pharmacol. 28(2) 165-177. 

Until very recently the risks associated with different types of chemicals such as food additives, pesticides, environmental contaminants and natural constituents of food were assessed and managed separately. However, a particular substance might fall into two or more of these categories and so the opportunity for simultaneous exposure might be overlooked. Furthermore, exposure to a chemical could occur through diet, drinking water, air pollution or dermal absorption. Aggregate exposure assessment aims to take all of the possible sources and routes of exposure into account in a realistic manner and thereby obtain a better overall estimate of risk. Initiatives have been set up in both the... 

Aggregate exposure assessment is naturally more complex than the methods used for dietary risk assessment. In the simplest analysis a worst case can be established for each source and exposure route and then summed to give a total exposure. If this were below any threshold of concern such as the PTWI then no further action would be required. However, if the total worst case exposure was above a PTWI then it is unlikely to reflect the real situation since the probability that any individual would be exposed to each source by each route at the maximum level is very remote. 

Micro-exposure event modelling combined with probabilistic modelling provides a great opportunity to assess real aggregate exposures in the real world. However, the method is highly dependent on the availability of complete and accurate information about levels of contamination and human behaviour. Whilst some of this is available, particularly in the context of pesticides, for other chemicals it may be a long time before this approach can be employed. 

Aggregate exposure is the exposure to a single substance from all exposure pathways and routes. 

ILSI (1998). International Life Science Institute Risk Science Institute. Workshop on Aggregate Exposure Assessment. Washington, DC. 

USEPA (2000). General Principles for Performing Aggregate Exposure and Risk Assessments, Report No. 6040, Office of Pesticide Programs and Office of Prevention, Pesticides and Toxic Substances, (http //www.epa.gov/pesticides/trac/science/) Washington, DC, November 21. 

Cumulative risk assessments evaluate the health risk for aggregate exposures accumulated over time and for multiple contaminants or stressors. In some contexts (e.g. USEPA pesticide risk assessments), cumulative refers specifically to combined exposures to chemicals that share a common mechanism of toxicity (see http // www.epa.gov/oppsrrdl/cumulative/). Populations may be defined by their location relative to sources, their activities and customs, and their susceptibility to exposures. In this context, populations can include different ethnic groups, different communities, or different age groups. Cumulative risk is a very important concept in understanding environmental health risks to children in different settings, particularly in underdeveloped countries where children may be facing multiple stressors. 

Hazardous Air Pollutant Exposure Model (HAPEM) Semistochastic, sequential simulation, producing aggregate exposure distributions Used by USEPA to evaluate national exposures to hazardous air pollutants (part of Trim.Expo model) Palma et al. (1996)... 

A United States study examined the aggregate exposures of preschool children to chlorpyrifos and its degradation product, 3,5,6-trichloro-2-pyridinol (TCP) (Morgan et al., 2005). Samples that were collected included duplicate diet, indoor and outdoor air, urine, solid and liquid food, indoor floor dust, play area soil, transferable residues, and surface wipes (hand, food preparation, and hard floor). Generally, levels of chlorpyrifos were higher than levels of TCP in all media, except for solid food samples. For these samples, the median TCP concentrations were 12 and 29 times higher than the chlorpyrifos concentrations at homes and day-care centres,... 

Aggregate exposure is total exposure to one stressor from several sources and/or via several pathways over time. 

EPA must estimate aggregate exposures to pesticides from food, drinking water, and nonfood (home, lawn, garden, etc.) uses when doing risk assessments. 

ASSESSMENT OF RISKS TO HUMANS EXPOSED TO PESTICIDES 2 The Four Steps in Risk Assessment 2 Hazard Identification 2 Dose-Response Assessment 3 Margin of Safety Approach 3 Quantitative Risk Assessment 3 Exposure Assessment 4 Risk Characterization 4 RISK MANAGEMENT 5 ADVANCES IN DATA INTERPRETATION 5 Probabilistic Approaches 5 Recognition of the Tier Approach 5 Aggregate Exposure 6 Cumulative Exposure 6 Impact of New Scientific Advances 7 Post-Registration Monitoring 7 HARMONIZATION OF REGULATORY APPROACHES SUMMARY 9... 

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