Aggregate exposure defined

Cumulative risk assessments evaluate the health risk for aggregate exposures accumulated over time and for multiple contaminants or stressors. In some contexts (e.g. USEPA pesticide risk assessments), cumulative refers specifically to combined exposures to chemicals that share a common mechanism of toxicity (see http // www.epa.gov/oppsrrdl/cumulative/). Populations may be defined by their location relative to sources, their activities and customs, and their susceptibility to exposures. In this context, populations can include different ethnic groups, different communities, or different age groups. Cumulative risk is a very important concept in understanding environmental health risks to children in different settings, particularly in underdeveloped countries where children may be facing multiple stressors. 

In the USA and Canada, aggregate exposure is defined as the combined exposure of a target to a single pesticide via all relevant pathways and sources . 

Aggregate exposure assessment A process for developing an estimate of the extent of exposure of a defined population to a given chemical by all relevant routes and from all relevant sources (ILSI, 1998). 

Cumulative exposure is defined as the combined exposure of a target to two or more pesticides (with a common mechanism of action) via all relevant pathways and sources . The US FQPA and the Canadian PCPA mandate the consideration of aggregation of pesticide chemical residues from dietary and residential exposures, and cumulative exposures of pesticide chemical residues with common mechanisms of action. This presents a formidable methodological challenge to exposure assessors. 

To quote the editor CRM may be defined as "a structure composed of non-metallic, chemically inert masonry units such as brick, stone, block or other aggregate bonded together with a mortar or mortars of adequate adhesion to the units and possessing suitable chemical and thermal resistance for the anticipated exposure. Such a structure may be assembled from units and mortars of a single type or from a combination of several different types of such units and mortars in order to achieve optimum and most economically satisfactory results." CRM structures as such comprise three components (1) Masonry units such as brick or tile (2) Mortars to bond them together, and (3) Membranes to attain a liquid-tight, fully resistant system. All of these components are available in various forms and are produced from many different materials. All three components must be chosen to meet both the environmental conditions and the design requirements of each application. 

Hazard severity is defined as the aggregate of the worst credible outcomes of a hazards-related incident, considering the exposure. 

Relevant threshold limit values for terpenes are rare because of a lack of basic information about specific terpene products and by-products on the one hand, and occupational and environmental exposures on the other hand. The threshold limit values which have been documented the best concern oil of turpentine. A MAK-value of 100 ppm is defined in German regulations and noted to be dermally sensitive. For other terpenes, such as d-limonene which is also classified as dermally sensitive, it has not yet been possible to establish a MAK-value because of a lack of information of their effects on animals or humans. With terpenes, as is often the case, aggregate concentration parameters are used as limit values such as the minimum level goals recommended by the former German Federal Flealth Authority. These suggested minimum values bear in mind actual levels detected in indoor areas. 

The fact that conjugated polymers are powerful tools in agglutination assays was first demonstrated by the exposure of biotinylated PPE 129 to avidin or streptavidin. Streptavidin binds to 129 and leads to agglutination and complete disappearance of the fluorescence in solution. Instead, a highly fluorescent pellet is formed. If 129 is treated with streptavidin-coated PS spheres, well-defined aggregates are formed. If similar biotinylated PPEs were treated with streptavidin, efficient energy transfer occurred when the streptavidin was labeled with Texas Red dye [127-129]. 

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