Risk assessment exposure data

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... 

In the risk assessment, some steps are not well described. For example, subchronic toxicity studies and not chronic toxicity studies are used in the risk assessment. Exposure duration and frequency considerations are not discussed. Route-to-route extrapolation is considered acceptable implicitly, without further evaluation of the various issues involved. The rationale for using a dermal absorption default of 10 %, in the absence of data is also not discussed. 

This model has a straightforward structure and is simple to use. It is based on studies carried out in part for the specific purpose of model development. However, not all of the required information is publicly available. The databases are not described at the study level the exposure data are only available in classes, although more detailed information is available on request. The choice of the statistics is not discussed. In the risk-assessment approach, some steps are not clearly presented. Sub-chronic toxicity studies, and not chronic toxicity studies, are used in the risk assessment. Exposure duration and frequency considerations are not discussed. Route-to-route extrapolation is considered acceptable implicitly, without further evaluation of the various issues involved. The rationale for using a dermal absorption default of 10 %, in the absence of data, is not discussed. 

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... 

Haber, Lynne has more than 12 years of experience in applying risk assessment methods in evaluating the toxicity, toxicokinetics, and mode of action of chemicals. Her current interests are in the application of mechanistic information in risk assessment and in methods for extending the dose-response curve to low doses. Other current work includes research on children s risk issues, consideration of mode of action in cancer risk assessment, incorporating data on polymorphisms into risk assessment, and development of scientifically based occupational exposure limits. 

In order to evaluate options, it is important to understand what could be done to limit the uncertainty, especially when this radically changes the options. For example, if the exposure level for safety is based on a conservative approach, necessitated by the uncertainty in an assessment, and an experiment could reduce the uncertainty by a factor of ten, then the control level may be able to be set much lower. This could change the control options significantly. A level of 10 ppb could require destruction of 1/2 of a crop, while a level of 100 ppb could have little, if any, economic consequences. For the present data deficiencies which contribute to the major uncertainties in the assessment, it is useful to identify the research, if any, which could limit uncertainty. Research such as this could lead to re-evaluation of a risk assessment after data are obtained, making delay of a decision unnecessary, and leading to increased use of relevant information in a risk assessment. 

Statistical Analysis of Risk and Exposure Data Collected for the Risk Assessment of Acute Exposure to Jet Fuel Study James Surles, Ben Duran, Hossein Mansouri,... 

Toxicity data (the SF and RfD) for As have been derived from toxicological studies performed using soluble forms of As. Therefore, site-specific bioavailability data obtained by in vitro or in vivo methods require conversion to relative bioavailability (RBA), as presented in the previous section, prior to its use in risk assessment. Bioavailability data can be used to provide more accurate exposure assessments that will result in more reasonable and site-specific risk estimates. Using RBA values, adjustments to toxicity values can be made as follows ... 

Summary Primary hepatocellular carcinoma is one of the most common cancers in the world and is prevalent on the continents of Africa and Asia. A number of classical epidemiological studies have determined that the exposure status of people to aflatoxin B1 is an important risk factor in the etiology of liver cancer. However, these studies have only relied upon the criteria of presumptive intake data, rather than information obtained from quantitative analyses of food samples, biological fluids and from people exposed to aflatoxin. Information obtained by monitoring exposed individuals for specific DNA adducts and metabolites will define the pharmacokinetics of aflatoxin B1 in people, thereby facilitating risk assessments. Preliminary data, reported here, support the concept that measurement of the major, rapidly excised AFB-N7-Gua adduct in urine and quantification of the more persistent aflatoxin albumin adduct are appropriate dosimeters for estimating exposure status and possibly risk in individuals consuming this mycotoxin. 

The information necessary for the assessment of environmental hazard and risk, resulting from the use of chemicals, is preferably obtained from field monitoring and laboratory studies, but often it has to be supplemented by estimates based on various modelling techniques. The input data set required for risk assessments comprises data on the persistence, accumulation, mobility and ecotoxicity of chemicals as well as detailed information on the particular environment, to estimate in stepwise fashion the exposure concentration and the toxic levels for a regional scenario (Figure 9.1). 

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Hazard identification involves gathering and evaluating data on the types of health injury or disease that may be produced by a chemical and on the conditions of exposure under which injury or disease is produced. It may also involve characterization of the behavior of a chemical within the body and the interactions it undergoes with organs, cells, or even parts of cells. Hazard identification is not risk assessment. It is a scientific determination of whether observed toxic effects in one setting will occur in other settings. 

Thus, tlie focus of tliis subsection is on qualitative/semiquantitative approaches tliat can yield useful information to decision-makers for a limited resource investment. There are several categories of uncertainties associated with site risk assessments. One is tlie initial selection of substances used to characterize exposures and risk on tlie basis of the sampling data and available toxicity information. Oilier sources of uncertainty are inlierent in tlie toxicity values for each substance used to characterize risk. Additional micertainties are inlierent in tlie exposure assessment for individual substances and individual exposures. These uncertainties are usually driven by uncertainty in tlie chemical monitoring data and tlie models used to estimate exposure concentrations in tlie absence of monitoring data, but can also be driven by population intake parameters. As described earlier, additional micertainties are incorporated in tlie risk assessment when exposures to several substances across multiple patliways are suimned. 

Risk characterization is tlie process of estimating tlie incidence of a healtli effect under tlie various conditions of human or animal exposure as described in the exposure assessment. It evolves from both dose exposure assessment and toxicity response assessment. The data are then combined to obtain qualitative and quantitative expression of risk. 

Lack of exposure data for most organotins together with limited toxicity information for marine organisms preclude the calculation of risk factors for the marine environment. For dibutyltin, measured concentrations in seawater reflect the use of tributyltin as a marine anti-foulant rather than the use of dibutyltin in plastics. It is therefore not possible to conduct a reliable risk assessment for the current uses of the compormd. 

In environmental risk assessment, the objective is to establish the likelihood of a chemical (or chemicals) expressing toxicity in the natural environment. Assessment is based on a comparison of ecotoxicity data from laboratory tests with estimated or measured exposure in the field. The question of effects at the level of population that may be the consequence of such toxicity is not addressed. This issue will now be discussed. 

In this phase of the risk assessment, the validity and reliability of conclusions and advice to risk managers depend on the quality, reliability, and relevance of available exposure data. Therefore it is necessary to (1) critically review the facts from food composition tables and the reasons for differences reported by and within countries, (2) consider the way foods are categorized and thus made comparable (or not) in food consumption surveys, and (3) explore how to refine assessments as more information becomes available. ... 

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

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