Human exposure evaluation

Human exposure evaluation is used in describing the nature and size of the population exposed to a substance and the magnitude and duration of their exposure. The evaluation could concern past or current exposures, or exposure anticipated in the future. 

The discerning reader may have noticed that the contents of the chapters of this book match the steps of risk assessment. Hazard evaluation concerns the type of material presented in Chapters 3 through 8. Dose—response was treated in 9, and human exposure evaluation was briefly reviewed in Chapters 1 and 2. 

And what is that dose range Human exposure evaluation comes next. What populations are of interest For aflatoxin it would be all individuals who consume peanut products. For trichloroethylene it might be those individuals who consume water derived from contaminated ground water supplies. What dose of the chemicals do these individuals receive, and for what period of time Because not all individuals in the population groups of interest will be exposed to identical doses, the risk assessor would attempt to understand the distribution of doses in the populations the number of people exposed to each of several different doses, or dose ranges. 

These three steps — hazard evaluation, dose-response evaluation, and human exposure evaluation - provide all that is necessary to... 

The pharmacological activities of the isomers should be compared in vitro and in vivo in both animals and humans. Separate toxicological evaluation of the enantiomers would not usually be required when the profile of the racemate was relatively benign but unexpected effects - especially if unusual or near-effective doses in animals or near planned human exposure - would warrant further studies with the individual isomers. 

Reliable evaluation of the potential for human exposure to endosulfan depends in part on the reliability of supporting analytical data from environmental samples and biological specimens. In reviewing data on endosulfan levels monitored or estimated in the environment, it should also be noted that the amount of chemical identified analytically is not necessarily equivalent to the amount that is bioavailable. 

A) The examination, summary, and interpretation of available toxicologic information and epidemiologic evaluations on a hazardous substance to ascertain the levels of significant human exposure for the substance and the associated acute, subacute, and chronic health effects ... 

Hazard characterization is a quantitative or semi-quantitative evaluation of the nature, severity, and duration of adverse health effects associated with biological, physical, or chemical agents that may be present in food. The characterization depends on the nature of the toxic effect or hazard. Eor some hazards such as genotoxic chemicals, there may be no threshold for the effect and therefore estimates are made of the possible magnitude of the risk at human exposure level (dose-response extrapolation). 

The degree of confidence in the final estimation of risk depends on variability, uncertainty, and assumptions identified in all previous steps. The nature of the information available for risk characterization and the associated uncertainties can vary widely, and no single approach is suitable for all hazard and exposure scenarios. In cases in which risk characterization is concluded before human exposure occurs, for example, with food additives that require prior approval, both hazard identification and hazard characterization are largely dependent on animal experiments. And exposure is a theoretical estimate based on predicted uses or residue levels. In contrast, in cases of prior human exposure, hazard identification and hazard characterization may be based on studies in humans and exposure assessment can be based on real-life, actual intake measurements. The influence of estimates and assumptions can be evaluated by using sensitivity and uncertainty analyses. - Risk assessment procedures differ in a range of possible options from relatively unso-... 

Methods for Determining Parent Compounds and Degradation Products in Environmental Media. Analytical methods with the required sensitivity and accuracy are available for quantification of americium, both total and isotopic, in environmental matrices (see Table 7-2). Knowledge of the levels of americium in various environmental media, along with the appropriate modeling (see Chapters 3 and 5), can be used to evaluate potential human exposures through inhalation and ingestion pathways. 

Major questions that arise whenever a pesticide exposure evaluation is completed are how good are the data and how close to the real answer have we gotten For most commercially sold insecticides, there are no appreciable pharmacokinetic data in human systems, although some data normally exist for animal models. Because such pharmacokinetic data do not exist for most active insecticides, passive dosimetry measurements must be used to estimate the exposure and eventually dose. Once such passive dosimetry data exist, certain assumptions must be made to arrive at an estimate of dose. 

Estimates of human exposure by route and subpopulation can be used directly, without comparison to health effects data, to evaluate potential pollutant problems in an area. For example, the following analyses can be performed ... 

The CalTOX model was originally developed as a set of spreadsheet models and spreadsheet data sets for assessing human exposures from continuous releases to air, soil, and water [7]. Hertwich [65-67] applied the CalTOX model for the assessment of human toxicity in Life Cycle Assessment (LCA). Ecotoxicicity is not evaluated in the model. 

---