Exposure data sources

Table 1. Air Quality Measurement Technology Available for Obtaining Population Exposure Data (Source Mueller et al. )... 

Control field matrices are usually placed at the field site upwind and at a significant distance from the spray or re-entry area so as to avoid all obvious routes of contamination at the test site that may destroy the integrity of the control samples. However, the control matrices should not be placed so far away from the test site as to avoid any suspected contamination that might occur from drift or other sources of contamination. One may want to define better the conditions at the test site in order to interpret better the exposure data collected from the volunteers matrices. 

In this chapter the risk assessment is briefly introduced. Risk assessment is divided into four steps hazard identification, hazard characterization, exposure assessment, and risk characterization. This chapter also highlights five risk and life cycle impact assessment models (EUSES, USEtox, GLOBOX, SADA, and MAFRAM) that allows for assessment of risks to human health and the environment. In addition other 12 models were appointed. Finally, in the last section of this chapter, there is a compilation of useful data sources for risk assessment. The data source selection is essential to obtain high quality data. This source selection is divided into two parts. First, six frequently used databases for physicochemical... 

Associations between breast cancer and total and specific fruit and vegetable group intakes were examined using standardized exposure definitions (Smith-Warner and others 2001). Data sources were eight prospective studies that had at least 200 incident breast cancer cases, included assessment of usual dietary intake, and had completed a validation study of the diet assessment method or a closely related instrument. 

Occupational exposure to higher than background levels of chloroform can be expected to occur in some occupations although few quantitative exposure data were located. Populations with the highest potential exposures appear to be workers employed in or persons living near industries and facilities that manufacture or use chloroform operators and individuals who live near municipal and industrial waste water treatment plants and incinerators, and paper and pulp plants and persons who derive their drinking water from groundwater sources contaminated with leachate from hazardous waste sites. 

Exposure data and other information on an agent under consideration are also reviewed. In the sections on chemical and physical properties, on analysis, on production and use and on occurrence, published and unpublished sources of information may be considered. 

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). 

Data from any source may be prone to errors or bias. Bias can be difficult to assess however, validation with an independent data source (e.g., vital or hospital records) or use of biomarkers of exposure or outcome, where possible, may help identify bias and increase confidence in the results of the study. 

Several estimates concerning the human daily intake of tin have been reported (EPA 1987 Klaassen et al. 1986 Krigman and Silverman 1984 WHO 1980). However, these estimates are not based on recent monitoring data and need to be revised in accordance with current data. Since canned food is a primary source of tin exposure, data on current levels of tin in canned foods and revised estimates of daily intake would help to better evaluate human exposure to tin. 

Given the limitations above, the national and local records may be considered as useful sources for the identification of the study population. They can be used for the restriction of the study to a population in which the particular exposure is fairly common thus increasing the effectiveness of the study. However, the data on occupational exposures in these registers are often unspecific or missing. The specific exposure data during the critical period of pregnancy must be clarified from other sources. 

BOX 5.1 Example of a spreadsheet calculation of the expected combined defined effect for a multiple mixture using different amounts of information. Note Tier-1 prediction relies on exposure and EC50 information (toxic unit summation), Tier-2 needs additional concentration response information for calculation of expected combined effects according to the reference models of response addition or concentration addition, and Tier-3 calculation (mixed models) requires information on the relevant mode of action. The sample is based on real analytical and effect data. Source Redrawn from data from Altenburger et al. (2004). 

The exposure assessment characterizes the pathways, magnitude, frequency, and duration of human exposures from various sources. Chapter 5 provides an overview of these components and addresses the principles of exposure assessment in children. General principles of exposure assessment have been reviewed in a number of publications (USEPA, 1992a, 2005a IPCS, 1999a, 2000 Needham et al., 2005). This chapter will focus on the considerations that are important when applying the exposure data to a children s health risk assessment (see Box 2). 

When using ERPG data, keep in mind that human responses vary widely and that particular responses cannot be attributed to exact levels of exposure. Other sources of hazards data in some case can be found in Material Safety Data Sheets (MSDS) issued by the manufacturer of the material or in the National Institute of Occupation Safety and Health (NIOSH) publication NIOSH Pocket Guide to Chemical Hazards (DHHS, 1990). 

Although human exposure data are essential for accurate evaluation of an agent s risk potential, data of sufficient quality and quantity are frequently unavailable. Thus, there is uncertainty in the exposure component of the evaluative process, even as there is in hazard characterization. When toxicity data indicate the potential for an adverse effect, the need to estimate the nature of human exposure becomes imperative. In those instances, exposure estimates can be derived using modeling approaches based on data from other sources, and one or more default assumptions can be used. The greater the number of default assumptions employed, the greater the uncertainty about the accuracy of the expert judgment. 

The National Center for Environmental Assessment (NCEA), which is part of the EPA Office of Research and Development (ORD), serves as the national resource center for the overall process of human health and ecological risk assessments the integration of hazard, dose-response, and exposure data and models to produce risk characterizations. NCEA prepares a variety of documents, many of which are the source of scientific information used by EPA decision makers in developing or revising regulations. The documents can pertain to a specific medium, such as air or water, or they can be comprehensive analyses of scientific data. Many NCEA documents contain analyses... 

Further work needs to be conducted in order to obtain a better understanding of the sources of variability in DFRs, TCs and re-entry worker exposure data. Stochastic methods may provide a way to better quantify the uncertainties associated with these data. 

The residential exposure assessment process presents numerous challenges and data sources which must be taken into consideration (Figures 4.2-4.5). 

Other research activities related to residential exposure assessment currently being sponsored by the USEPA include the National Human Exposure Assessment Survey (NHEXAS) (website http //www.epa.gov/heasd/edrb/nhexas.htm). In addition, the USEPA concluded a Co-operative Agreement, referred to as the Residential Exposure Assessment Project (REAP) with the Society for Risk Analysis (SRA) and the International Society of Exposure Analysis (ISEA) which resulted in a reference textbook (Baker et al, 2001) describing relevant methodologies, data sources and research needs for residential exposure assessment. The REAP and other efforts complement other USEPA initiatives, such as the development of the Series 875 guidelines, and will facilitate a sharing of information and other resources between the USEPA, other Federal and State agencies, industry, academia and other interested parties. 

The exposure data were categorized according to formulation type and application technique and presented in graphs, in order to obtain a comprehensive overview of the large spread in exposure data per literamre source and formulation type (for mixing/loading) and per application technique (for application). 

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