Exposure assessment tools

A Resources to identify chemicals of concern B Chemical toxicity C Exposure assessment tools D Hazard and risk assessment tools E Safer chemistry design tools... 

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... 

USEPA Exposure Assessment Tools and Models, United States Environmental Protection Agency, 2005. http //www.epa.gov/oppt/exposure/docs/episuite.htm... 

The Office of Pollution Prevention and Toxics (OPPT) has developed a series of methods, databases, and predictive models to help in evaluating what happens to chemicals when they are used and released into the environment. These tools are intended to be used by scientists and engineers famihar with exposure assessment principles. 

The impetus for this flurry of activity has been the recognized need for cost-effective tools, based on sound scientific principles (i.e., state-of-the-art), to assist in the performance of exposure assessments for new and existing chemical compounds and toxic wastes. 

Despite the fact that there exist some differences between both methodologies, the cooperation between the aforementioned tools seems to be advantageous to use in environmental management [7]. Moreover, there are also steps in LCIA that also exist in the risk assessment (i.e., exposure assessment). Therefore, models used in LCIA can be used also to assess human or environmental exposure to chemicals. For that reason LCIA models are also included in the review of models of risk assessment. 

When evaluating the safety of chemicals in humans, it is very important to know the fate of chemicals in the human body and the amounts of exposure in daily activity. This section reviews the metabolic reactions of pyrethroids in humans, and the biomonitoring of pyrethroid metabolites in human urine for the exposure assessment. Mathematical modeling is a useful tool to predict the fate of chemicals in humans. This section also deals with the recent advance of mathematical modeling of pyrethroids to predict the pharmacokinetics of pyrethroids. 

The approach to exposure assessment is not as internationally harmonized as hazard assessment. A synopsis of current activities regarding exposure assessment for industrial chemicals in a number of OECD Member countries has been published (OECD 2006). The executive summary of this document states that while there is a significant level of sharing of approaches used for hazard characterization for risk assessment, this is not the case for exposure characterization. Although broad consistency in the overall approaches used by different countries in conducting exposure assessment exists, there is variation in policy-related factors, including the regulatory context for assessment and the way that information is applied, as well as in the types of approaches and tools used. 

The European Commission s Joint Research Centre (on behalf of DG S ANCO) has started a project known as European Information System on Risks from Chemicals Released from Consumer Products/Articles (EIS-ChemRisks) (EU 2004), which is designed as a network to collect exposure data, exposure factors, exposure models, and health-related data. The overall objective is to develop tools and reference data to enable harmonized exposure assessment procedures in the EU. A toolbox has been designed to collect exposure information from four reference systems to systematically support exposure assessors in the EU ... 

A distinguishing characteristic of Total Diet Surveys like the NZTDS (Cressey et al., 2000) is that foods are analysed as normally consumed (e.g. bananas peeled, meat cooked etc.). They therefore frequently provide the most relevant means of assessing the consumer s exposure. A Total Diet Survey is essentially a public health risk assessment tool, and not a compliance monitoring tool. 

Where effects are known to be dependent on pulsed exposures, and the temporal nature of the exposures is modeled or measured, the exposures can be characterized using a tool such as the Risk Assessment Tool to Evaluate Duration and Recovery (RADAR), developed as part of the efforts of ECOFR AM (ECOFRAM1999 Reinert et al. 2002). This tool provides information on pulse magnitude, duration, and interpulse interval, which is particularly useful for assessing likely effects on classes of organisms with known recovery times and time-exposure responses. 

Mangels G] Waterborne Environmental, Inc. 2001. The development of MUSCRAT (multiple scenario risk assessment tool) a software tool for conducting surface water exposure assessments, http //www.waterborne-env.com/modeling/model down-load muscrat.html (accessed January 2, 2007). 

When appropriately validated and understood, biomarkers present unique advantages as tools for exposure assessment (Gundert-Remy et al, 2003). Biomarkers provide indices of absorbed dose that account for all routes and integrate over a variety of sources of exposure (IPCS, 1993, 2001a). Certain biomarkers can be used to represent past exposure (e.g. lead in bone), recent exposure (e.g. arsenic in urine), and even future target tissue doses (e.g. pesticides in adipose tissue). Once absorbed dose is determined using biomarkers, the line has been crossed between external exposure and the dose metrics that reflect the pharmacokinetics and toxicokinetics of an agent (see section 5.3.3). 

Because data on non-professional exposure is scarce but exposure assessments are necessary, models have become a main tool in assessing residential exposure. It appears to be easier to obtain good quality data on exposure factors (room sizes, typical amounts used, etc.), which can be used as parameters in models, than to obtain direct exposure measurements. Critics of the modeling process say that the information generated through models is suspect because of the inherent simplifications involved. This criticism may be valid if risk assessors who utilize models do not make the appropriate selections that are needed in their application. They need to ask the following which model should be used which data should be fed into the model why do these two (three) models produce different results, and are the differences significant for risk assessment which data are necessary... 

Approaches for aggregating exposure for simple scenarios have been proposed in the literature (Shurdut et al., 1998 Zartarian et al., 2000). The USEPA s National Exposure Research Laboratory has developed the Stochastic Human Exposure and Dose Simulation (SHEDS) model for pesticides, which can be characterized as a first-generation aggregation model and the developers conclude that to refine and evaluate the model for use as a regulatory decision-making tool for residential scenarios, more robust data sets are needed for human activity patterns, surface residues for the most relevant snrface types, and cohort-specific exposure factors (Zartarian et al, 2000). The SHEDS framework was used by the USEPA to conduct a probabilistic exposure assessment for the specific exposure scenario of children contacting chromated copper arsenate (CCA)-treated playsets and decks (Zartarian et al, 2003). 

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