Risk assessment minimizing exposure

EPA research investments since 1995 in pesticide exposure and risk assessment methods have helped pioneer novel approaches to quantify risk levels. A team at the University of Washington s School of Public Health and Community Medicine found that 2-5 year olds consuming predominantly organic foods over a 3-day period had 8.5-fold lower mean levels of OP insecticide metabolites in their urine than children eating mosdy conventional (unlabeled) foods (Curl et al., 2003). The study was carefully designed to minimize potentially... 

Risk assessment An evaluation of the potential impacts of a chemical or physical hazard on human health or the environment. A risk assessment is the first step in managing and minimizing risks. Risk assessments often include identifying human health or environmental threats, possible exposure routes (e.g. inhalation, digestion, or contact with skin), the likely duration of any exposure, and the individuals that are at risk (e.g. workers, the general public, or both). A risk assessment may also involve defining the probability of an adverse effect and establishing safety limits based on health standards. 

We must recognize, however, that our abilities may be limited by a lack of other types of data and by the limitations of the rapidly evolving science of risk assessment. In an effort to minimize these limitations, the Office of Solid Waste is investigating the best available risk assessment techniques. These include estimation of the movement of pollutants through soil, air, and water prediction of adverse human health and environmental effects on the basis of available toxicity data and prediction of the effects of simultaneous exposures to numerous toxic substances. OSW is, in addition, actively compiling data relative to the cost, applicability, and effectiveness of currently available waste treatment, storage, and disposal technologies. 

A hazard is anything that will produce an adverse effect on human health and the environment. In environmental risk assessment, the hazard component generally refers to toxicity. Exposure is the quantitative or qualitative assessment of contact to the skin or orifices of the body by a chemical. Traditional pollution prevention techniques focus on reducing waste as much as possible however, risk assessment methods used in pollution prevention can help quantify the degree of environmental impact for individual chemicals. This approach provides a powerful tool that enables engineers to better design processes and products by focusing on the most beneficial methods to minimize all aspects of risk. 

Because human pharmacokinetic data are often minimal, absorption data from studies of experimental animals-by any relevant route of exposure-might assist those who must apply animal toxicity data to risk assessment. Results of a dermal developmental toxicity study that shows no adverse developmental effects are potentially misleading if uptake through the skin is not documented. Such a study would be insufficient for risk assessment, especially if it were interpreted as a negative study (one that showed no adverse effect). In studies where developmental toxicity is detected, regardless of the route of exposure, skin absorption data can be used to establish the internal dose in the pregnant animal for risk extrapolation to human dermal exposure. For a discussion pertinent both to the development and to the application of pharmacokinetic data, risk assessors can consult the conclusions of the Workshop on the Acceptability and Interpretation of Dermal Developmental Toxicity Studies (Kimmel and Francis 1990). 

Several years later, EU risk assessment data confirmed TCE as a carcinogen, but a RRS has yet to be completed. TCE is a commonly used solvent that has several applications that may not easily be substituted, so several Member States have adopted different national regulatory controls for TCE [246]. Achieving future consensus on EU action to control this substance may therefore prove particularly difficult. Evidence suggests that, with the possible exception of setting (minimal) occupational exposure Limits, developing and implementing RRS to protect occupational health should remain at the national level for this substance. 

Risk assessment is a scientific process whereby the level and nature of the risk is determined. If there is no exposure to a particular chemical then there will be no risk at all, for example potassium cyanide in a sealed container is a hazard but not a risk. Risk can therefore be minimized if exposure is minimized. If the chemical is effectively non-hazardous, that is the amount needed to cause harm is unrealistically high, such as with common salt or saccharin, then even if there is a level of exposure, the risk will be so small as to be virtually non-existent. Therefore both the level of exposure and the nature of the chemical (whether or not it is hazardous) must be known if the risk is to be assessed. 

Interspecies and intraspecies UFs have been used in the development of safe or threshold exposure levels for chronic, noncancer toxicity by health organizations throughout the world. Examples include the acceptable daily intake (ADI) (Lu 1988 Truhaut 1991 Lu and Sielken 1991), the tolerable daily intake (TDI) or tolerable concentration (TC) (Meek et al. 1994 IPCS 1994), the minimal risk level (MRL) (Pohl and Abadin 1995), the reference dose (RfD) (Barnes and Dourson 1988 Dourson 1996), and the reference concentration (RfC) (EPA 1994 Jarabek et al. 1990). The importance of using distribution-based analyses to assess the degree of variability and uncertainty in risk assessments has been emphasized in recent trends in risk analysis. This will enable risk managers to make more informed decisions and... 

The initial process in the application of toxicity (dose-response) data in risk assessment is the extrapolation of findings to establish acceptable levels (AL) of human exposure. These levels may be reference values (inhalation reference concentrations, RfC or oral reference doses, RfD), minimal risk levels (MRL) values, occupational exposure limits, and so on. When the toxicity data are derived from animals, the lowest dose representing the NOAEL (preferably) or the LOAEL defines the point of departure (POD). In setting human RfD, RfC, or MRL values, the POD requires several extrapolations (see [13] and revisions). Extrapolations are often made for interspecies differences, intraspecies variability, duration of exposure, and effect level. Each area is generally addressed by applying a respective uncertainty factor having a default value of 10 their multiplicative value is called the composite uncertainty factor (UF). The UF is mathematically combined with the dose at the POD to determine the reference value ... 

In summary, having established an animal MOA and human relevance for this MOA, it is appropriate to address dose-response assessment, human exposure analysis, and risk characterization. Thus, the purpose of the human relevance framework is to establish which chemicals (or chemical mixtures) should be considered for a quantitative risk assessment and which do not require further consideration because they present a minimal risk or no risk to humans. Several thoroughly worked examples are presented in Meek et al. (2003). 

Additional Analyses. Although the Main Analyses provided in Risk As-sistant cover the essential core of site-specific risk assessment, it is anticipated that risk assessors will also need assistance in other areas. The software system currently addresses three concerns the need for setting priorities for site review based on minimal data, the frequent need to use models to predict the transport of chemicals from the site to populated areas, and the need to distinguish between probable and less likely conditions of exposure. 

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