Health risk characterization

A risk estimate indicates Uie likelihood of occurrence of the different types of health or enviroinnental effects in exposed populations. Risk assessment should include both liuimn health and environmental evaluations (i.c., impacts on ecosystems). Ecological impacts include actual or potential effects on plants and animals (other than domesticated species). The number produced from the risk characleriznlion, representing the probability of adi crse 

There me two major types of risk ina. imuin individual risk and population risk. Maximum risk is defined e.xacUy as it implies, Uiat is the ma.ximum risk to an individual person. Tliis person is considered to have a 70-year lifetime of exposure to a process or a chemical. Population risk is Uie risk to a population. It is expressed as a certain number of deaths per Uiousand or per million people. For example, a fatal annual risk of 2 x 10 refers to 2 deatlis per year for every million individuals. These risks are based on very conser ative assumptions, llich may yield too high a risk. 

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The TGD has been revised and the second edition was published in 2003 (EC 2003). However, the human health risk characterization part was not included in this second edition. A final draft version of the human health risk characterization part was released in 2005 with a detailed guidance on, among others, the main issues to be included in derivation of the reference MOS (MOSref), which is analogous to an overall assessment factor. The individual factors contributing to the MOSref are described separately and guidance is given on how to combine these into the MOSref. The guidance provided in this draft version has been extensively used in relation to the risk assessment of prioritized substances carried out since the draft version was released however, this version is not publicly available. 

The human health risk characterization is typically carried out by comparing the No-Observed-Adverse-Effect-Level (NOAEL) to the human exposure level. The ratio is called Margin of Safety. If human exposure is estimated to exceed the NOAEL, the substance is considered to be of concern . If the exposure estimate is less than the NOAEL, the appropriate margin of safety is assessed case-by-case (European Commission 2003a). 

See also Benchmark Dose Exposure Assessment Exposure Criteria Hazard Identification Hormesis, LD50/ LC50 (Lethai Dosage 50/Lethai Concentration 50) Levels of Effect in Toxicoiogicai Assessment Maximum Allowable Concentration (MAC) Maximum Tolerated Dose (MTD) Pharmacokinetics/Toxicokinetics Reference Concentration (RfC) Reference Dose (RfD) Risk Assessment, Ecological Risk Assessment, Human Health Risk Characterization Toxicity, Acute. 

See also Ames Test Analytical Toxicology Animal Models Biomarkers, Human Health Epidemiology Good Laboratory Practices (GLP) In Vitro Test In Vivo Test Risk Assessment, Human Health Risk Characterization Toxicity, Acute Toxicity, Chronic Toxicity, Subchronic. 

See also Clean Air Act (CAA), US Clean Water Act (CWA), US Federal Insecticide, Fungicide, and Rodenti-cide Act, US Food, Drug, and Cosmetic Act, US Risk Assessment, Ecological Risk Assessment, Human Health Risk Characterization Risk Management Safe Drinking Water Act, US Toxic Substances Control Act, US. 

See also Risk Assessment, Ecological Risk Assessment, Human Health Risk Characterization Risk Management. 

CHPPM (2000) Depleted uranium - Human exposure assessment and health risk characterization in support of the environmental exposure. Report Depleted Uranium in the Gulf (II) Health risk assessment consultation No. 26-MF-7555-99D. OSAGWI, Washington, DC... 

An adequate treatment of health risk characterizations for Pb in humans requires that all three input components be evaluated. Reliable dose—toxic response data also require reliable exposure characterizations to complete the risk assessment. Conversely, well-characterized exposures would further require well-established dose—response relationships for the particular toxic contaminant. Absence of hazard assessment data prevents the evaluation of toxic responses in any dose—response relationships regardless of the quality of the dose or exposure characterizations. 

This section presents three case examples of site-based lead exposure characterizations for subsequent risk assessment purposes. The case studies are based on research where environmental media-specific levels of Pb were determined as part of the epidemiological and statistical designs. For purposes of this section, such two-part case studies are desirable for, first, quantifying baseline exposure characterizations and eventual baseline human health risk characterizations and, second, for identification of which... 

Health Risk Characterization of Lead Effects in Human Populations... 

Communities where increased environmental lead exposures and various toxic endpoints have been explicitly incorporated into a dose—response framework currently highlight health risk characterization using case-specific evidence. Data generated in such communities typically first permit determination of distributions of risk group PbB values, specifically prevalences and incidences of PbB above an accepted health risk threshold. These PbB statistics are then incorporated into health risks using dose—toxic response relationships. 

METHODOLOGICAL AND INTERPRETIVE ISSUES FOR LEAD HEALTH RISK CHARACTERIZATION IN HUMANS... 

There are several ways one can quantify human health risk characterization for humans at risk through lead exposure. The first and simplest examines the prevalences or incidences of blood lead levels above some health risk threshold, with frequencies of exceedance identifying those at more risk (compared to those with PbB values below the risk threshold). Expressions of health risk in terms of elevated PbB occurrences (e.g., 10 jig/dl) do not simultaneously provide quantitative estimates of organ- or system-specific toxic harm, such as actual loss of IQ points or increases in SBP or DBP. A health risk threshold indexed in terms of a PbB level, however, represents the synthesis of numerous empirical dose—toxic response relationships, as developed and discussed in previous chapters. 

This chapter presents several case examples of health risk characterization for lead in various U.S. lead exposure scenarios. Two of these follow case examples described in the previous chapter for selected actual exposure scenarios derived from U.S.-based measurement or modeled data. In these cases, risk is characterized at some accepted value for an operational, i.e., empirical... 

Health Risk Characterization of Pb at the Silver Valley, ID/Superfund Site... 

Health Risk Characterization for Pb at Multiple U.S. Communities Providing Pooled Soil and Dust Pb Loading Data... 

U.S. EPA s Health Risk Characterizations for Air Pb and Standard Setting Using Case Studies... 

Besides some of the technical complexities noted above, air Pb at toxic levels for human exposures is at microlevel and submicrolevel amounts. A brief reading of the levels of air Pb permissible in emissions to the human environment makes this apparent. This analytical reality meant that quantitative analysis of air Pb for purposes of health risk characterization and evaluation of dose—response relationships was not feasible. Second, the fact that lead entered ambient air where people live by either mobile (largely vehicular emissions) or point sources (e.g., smelters, incinerators, other pyrogenic sources) meant legislation and associated rales and regulations had to be crafted with these sources in mind. 

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