Exposure Factors Handbook

USEPA] US Environmental Protection Agency. 1993b. Wildlife exposure factors handbook, Vol. 1. United States Environmental Protection Agency, Method EPA 600-R-93- 187a. 

EPA. 1989c. Exposure factors handbook. Washington, DC U.S. Environmental Protection Agency, Office of Health and Environmental Assessment. EPA/600/8-89/043. 

FIGURE 7.1 Inhalation - correlation between exposure concentration and internal dose. (Modified from US-EPA, Exposure Factors Handbook, National Center for Environmental Assessment, Washington DC, 1997.) Available at http //www.epa.gov/ncea/efh/... 

The US-EPA Exposure Factors Handbook (US-EPA 1997), first published in 1989, provides a summary of the available data on consumption of drinking water consumption of fmits, vegetables, beef, dairy products, and fish soil ingestion inhalation rates skin surface area soil adherence lifetime activity patterns body weight consumer product use and the reference residence (data that are available on residence characteristics that affect exposure in an indoor environment). 

The US-EPA Child Specific Exposure Factors Handbook (US-EPA 2006), first published in 2002, consolidates all children s exposure factors data into one document. The document provides a summary of the available and up-to-date statistical data on various factors assessing children s exposures. These factors include drinking water consumption soil ingestion inhalation rates dermal factors including skin area and soil adherence factors consumption of fruits, vegetables, fish, meats, dairy products, homegrown foods, and breast milk activity patterns body weight consumer products and life expectancy. 

In 2002, the European Exposure Factors (ExpoFacts) database started as a 2-year project funded by CEFIC-LRI (European Chemical Industry Council, Long Range Research Initiative) to create a European database of factors affecting exposure to environmental contaminants. The aim was to create a public access data source, similar to the US-EPA Exposure Factors Handbook (US-EPA 1997), which has been widely used by European researchers, but with European data. Since 2006, the project is hosted by the European Commission s Joint Research Centre (JRC 2007). 

In the Exposure Factors Handbook, US-EPA (1997) has identified five key studies and five other studies on VRs. The results of these studies, which are all from the United States, show the following general tendencies ... 

The recommended VRs in the Exposure Factors Handbook (US-EPA 1997) are summarized in Table 7.3 the VR for each age group was calculated as the average of the VRs for the various activity levels, see Table 7.2. 

ECETOC (2001) has collected exposure data in the Exposure Factors Sourcebook for European Populations. For VRs, the Sourcebook presents the values, which are recommended by the US-EPA in the Exposure Factors Handbook (US-EPA 1997), see Table 7.3. ECETOC states that these values are probably representative of Europeans as well. 

In the Exposure Factors Handbook, US-EPA (1997) has identified seven key studies which employ methods based on measurements of tracer elements, and nine other studies on soil intake among children. The individual key studies used between three and eight different tracer elements. Not all the tracer elements turned out to be useful for estimation of the daily soil intake aluminum, silicon, and yttrium appeared to be the most reliable. The results of the studies are summarized in Table 7.4. 

In the Exposure Factors Handbook, US-EPA (1997) has identified three studies where the daily soil intake for adults has been estimated. In one of these studies, an annual average soil intake of 60.5 mg/day was estimated based on assumptions regarding the amount of soil and dust on the hands, so-called mouthing behavior , and indoor and outdoor activities. In the second study, a daily soil intake of 50 mg/day was estimated based on measurements of urinary arsenic, mouthing behavior , and information about behavior patterns. In the third study, a daily soil intake of 30-100 mg/day was estimated based on tracer element measurements. The latter study was evaluated by the US-EPA as the most reliable one. 

Table 7.6 summarizes soil ingestion recommendations in the Exposure Factors Handbook (US-EPA 1997). 

In the Exposure Factors Handbook, US-EPA (1997) has identified three key studies and nine other studies on drinking water intake. The results of these studies, which apart from one are aU from the United States, showed a good agreement across studies for the estimate of the mean and 90th percentile. The results also showed an increase in drinking water intake with age, with level of physical activity, and with ambient temperature, and US-EPA notes that based on body weight, children consume more water than adults, and old people consume more than middle-aged people. Table 7.7 presents the results of one central study (Ershow and Cantor 1989 - cited in US-EPA 1997). Table 7.8 summarizes the results of the three key studies and Table 7.9 the results of the nine other studies. 

Daily Intake of Drinking Water. Results from Other (Nonkey) Studies Cited in the Exposure Factors Handbook... 

US-EPA. 2006. Child Specific Exposure Factors Handbook 2006 (External Review Draft). Washington, DC National Center for Environmental Assessment. Office of Research and Development. Presently undergoing update (In press), http //cfpub.epa.gov/ncea/cfm/recordisplay.cfm7deid = 56747 US-EPA. 2007a. EPA/OPPT Exposure Assessment Tools and Models website, http //www.epa. gov/opptintr/ exposure /pub s/opptexpo. htm... 

The EPA controls the regulation of poisonous substances in the drinking water and in food, and provides an Integrated Risk Information System (IRIS) database for assessment in their Exposure Factors Handbook. They published drinking water standards in 1994 in terms of MCE in mg/L and as a health advisory RfD in mg/(kg day) of intake (Chapter 6). Some typical values are given in table 10.3, which shows a tremendous range of five orders of magnitude between the mildly toxic xylene and the extremely toxic white phosphoms. 

US EPA (1997a) Exposure factors handbook — final report. Washington, DC, US Environmental Protection Agency (EPA/600P-95/002Bc). 

Default values have been published for use in estimating exposures — for example, from food and water consumption in adults and children, soil ingestion in children, and respiration rates in children and adults (USEPA, 1990). The Child-Specific Exposure Factors Handbook summarizes data on human behaviour and characteristics that affect children s exposure to environmental agents and recommends values to use for these factors (USEPA, 2002a). 

Exposure assessment involves the specification of values for parameters, either for direct determination of the exposure or as input for mechanistic or empirical or distribution-based models that are used to fill the exposure scenario with adequate information. Numerical values for exposure parameters are obtained using various approaches, such as the USEPA s Exposure Factors Handbook (USEPA, 1997a), the European Union s (EU) Technical Guidance Document (EU, 2003), the German XProb project (Mekel, 2003) and the European KTL s ExpoFacts (Vuori et al., 2006). 

USEPA (1997) Exposure Factors Handbook, Vol. 1 - General Factors. US Government Printing Office, EPA/600/P-95/002. Washington, DC. 

USEPA (2002) Child-Specific Exposure Factors Handbook. National Center for Environmental Assessment, EPA-600-P-00-002B, Washington, DC. 

USEPA (1999). Exposure Factors Handbook, EPA/600/C-99/001, United States Environmental Protection Agency, National Centre for Environmental Assessment, Cincinnati, OH, USA. 

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