Hazard assessment expected exposure concentration

Geographic Information System (GIS) A system that allows for the interrelation of quality data (as well as other information) from a diversity of sources based on multilayered geographical information-processing techniques, hazard (toxic) The set of inherent properties of a stressor or mixture of stressors that makes it capable of causing adverse effects in humans or the environment when a particular intensity of exposure occurs. See also risk, hazard assessment (HA) Comparison of the intrinsic ability to cause harm with expected environmental concentration. In Europe, it is typically a comparison of predicted environmental concentration (PEC) with predicted no-effect concentration (PNEC). It is normally based on a single value for effects and exposure. It is sometimes incorrectly referred to as risk assessment. 

EPA risk assessment practice, (and the Risk Assistant software) reflects this distinction between generic and site-specific information in the prediction of the risks associated with an agent at a specific site. The results of authoritative Hazard Identifications and Dose-Response Assessments are not expected to be re-evaluated by the risk assessors evaluating specific sites these assessors are expected to concentrate on site-specific Exposure Evaluation and Risk Characterization. 

Determining anticipated route and magnitude of exposure is an important component in the overall assessment of safety and must be done on a nanomaterial-by-nanomaterial basis, with secondary exposures taken into consideration when necessary. The estimated exposure levels for a nanomaterial may then be compared with the calculated safe dose derived from the hazard identification evaluation. The procedures and factors considered in the exposure assessment process are not expected to be any different for nanomaterials than for larger particles or chemicals. The degree of hazard associated with exposure to any chemical or substance, regardless of its physicochemical characteristics, depends on several factors, including its toxicity, dose-response curve, concentration, route of exposure, duration and/or frequency of exposure. However, depending on the route of anticipated exposure (dermal, inhalation, oral) and types of associated toxicities (local or systemic), a chemical may not pose any risk of adverse effects if there is no... 

It is advisable, then, in a tiered approach to concentrate first on crops and activities (scenarios) that are considered to be relevant with respect to the expected level of exposure and to exclude those not relevant. Second, whether or not the toxicological properties of the product may lead to general restrictions on re-entry should be investigated. If both the likelihood of reentry and the hazard due to the toxicity of the compound cannot generally be neglected, a risk assessment over several steps should be carried out. The assessment may be based on surrogate data and "worst-case" assumptions at first and then refined, if necessary. One possible approach to a tiered evaluation procedure is presented in Figure 1. 

Exposure Levels in Environmental Media. Very few data are available regarding the presence of 2-hexanone in any environmental media (CLPSD 1989 Lucas 1984 Myers 1983). Although high levels of this compound are not expected to occur in ambient air, water, or soil, concentrations of 2-hexanone in these media near effluent sources or hazardous waste sites would be helpful in assessing the potential extent and magnitude of human exposures. 

Przybylowski 1971). However, limitations associated with this study preclude its use in assessing the potential cardiovascular risk to humans from exposure to gasoline. No adverse cardiovascular effects have been observed in animals exposed to levels of up to 2,056 ppm unleaded gasoline vapors for up to 2 years. The air and water concentrations of gasoline expected to be present at hazardous waste sites are unlikely to cause adverse cardiovascular effects. 

Respiratory Protection To assess the safety of any particular operation, measurement of the solvent vapor exposure to workers in the area is recommended. If it is determined that the concentration in air is less than the recommended TWA for the solvent, no injury would be expected to workmen. If changes are made in the operation, which may result in an increase in concentration, duration, or frequency of exposure, measurements should be repeated. The degree of hazard can be minimized by containing the cleaning operation in an enclosed area, such as a hood, by ventilation that removes the vapors from the workroom air away from workers. The use of personal protective devices, such as gas masks, respirators, and self-contained or remote breathing apparatus, are not recommended for continuous use but can be effective for handling spills or similar upsets. 

Risk may arise from any chemicals released into the environment, intentionally or by accident, during manufacture, use or dissipation of the products. The expected concentration time profile for chemicals at specific locations in the various environmental media - water, air, soil and biota - may result in hazards to humans and the environment. Hence, ecological risk assessment must evaluate the probability whether the exposure level of potential contaminants may exceed effective (i.e. toxic) concentrations in the environmental compartment of concern. The basic principle is the comparison of the environmental and the toxic concentrations of the contaminants ... 

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