Indirect exposures

U.S. EPA recommends that site-specific risk assessments, incorporating direct and indirect exposures, be considered during the combustion unit s permitting process. These risk assessments may be used to evaluate the unit s impact on the surrounding environment. If a site-specific risk assessment shows that additional protection should be afforded to the surrounding environment, U.S. EPA typically will use the omnibus authority to impose the necessary permit conditions. 

U.S. EPA, Methodology for Assessing Health Risks Associated with Indirect Exposure to Combustor Emissions, EPA/600/6-90/003, U.S. Environmental Protection Agency, Washington, DC, 1990. 

Grandjean P, Bach E. 1986. Indirect exposures The significance of bystanders at work and at home. Am Ind Hyg Assoc J 47 819-824. 

Exposure assessment a) For the human population, workers, consumers and indirect exposure via the environment b) For the different environment compartments likely to be exposed to the substances water, sediment, soil, and air ... 

Indirect exposure of humans via the environment may occur by consumption of food (fish, crops, meat, and nulk) and drinking water, inhalation of ambient air, and ingestion of soil. For existing substance, measured levels in various environmental compartments may be available however, for new substances, usually no relevant measured data are available and concentrations of a substance in the environment must be estimated. 

The indirect exposure is estimated by the use of FUSES. FUSES estimates concentrations in food and the total daily intake of a substance based on predicted environmental concentrations for (surface) water, groundwater, soil, sediment, and ambient air. The indirect exposure is principally assessed on two spatial scales locally near a point source of the substance, and regionally using averaged concentrations over a larger area. A third spatial scale, the continental scale, is... 

Current knowledge about the combined toxicological effects that may occur from exposures to different chemicals in mixtures is outlined in this chapter. Special attention is paid to the low levels of exposures normally encountered from the unintended, indirect exposure to chemical mixtures through food and environment. It should be recognized that it has not been possible to cover all possible combined exposures to chemicals in this book. 

Avoid direct and indirect exposure to sunlight (even when using sunscreen), discontinue at first signs of phototoxicity, avoid re-exposure to sunlight until completely recovered from reaction... 

Urticaria A vascular reaction of the skin marked by the appearance of wheals may be caused by direct or indirect exposure to a toxic substance. Also known as hives. 

Indirect exposure assessment, both human and environmental, starts with emission data and a prediction of the fate of chemicals in the environment and the resulting concentrations in different environmental compartments. Foster et al. (2005) outlined 5 steps in a strategy to conduct exposure assessment of complex mixtures, consisting of many different components, such as gasoline. These steps, as outlined below, are also relevant when assessing exposure to less complex mixtures. 

Environmental exposures form the basis for determining indirect exposures to the general public that will usually occur during a lifetime. Direct consumer exposure assessments prove equally challenging, and may vary from acute to chronic exposure scenarios. Ideally the data set for consumer exposure from a substance in a product should include [127] ... 

The indirect exposure to PFCAs through ingestion of chemicals applied to food contact paper packaging was investigated by D eon and Mabury [146]. In this study, the load of PFCAs in rats was quantified following exposure to polyfluoroalkyl phosphate surfactants (PAPS), a class of nonpolymeric PFCs approved for application to food contact paper products. Increased levels of PFOA were observed in the dosed animals, linking ingestion of PAPS with in vivo production of perfluorinated acids [146]. 

In addition to direct contact with the pesticide, indirect exposure is also likely through such actions as brushing against plants, animals, or other items just treated with pesticides or from overhead fallout of pesticide, such as mists, drips, or dusts. 

Aggregate assessments require consideration of indirect exposure measurements (e.g., dermal exposure by measurement of residues that are transferable from a surface such as residential turf to clothing, skin, or relevant surrogate media inhalation exposure by measurement of air concentration in the breathing zones of individuals ingestion exposure by measurement of concentrations in water, food, etc., ingested by an individual), and where available, direct exposure measurements (e.g., measurement of the concentration of the chemical or its biotransformation products in biological tissues or fluids). 

The purpose of this article is to consider the nature of soils, how soils are contaminated by human activities, how these contaminants are transported and transformed in the soil column, and the types of human activities that could result in human exposure to soil contaminants. Soils are complex systems that exist at the interface among atmosphere, biosphere, hydrosphere, and lithosphere. A true soil includes gas, water, mineral, and organic components. Potential human contacts with soil can result in inhalation, ingestion, and dermal uptake of soil contaminants through both direct and indirect exposure pathways. The magnitude and persistence of exposure depends not only on the level of soil contamination, but also on the physical and chemical properties of soil, the chemical properties of the contaminant, and the frequency and duration of human activities such as occupational and recreational activities or use of home-grown food, which result in direct and indirect soil contacts. Toxicologists should be aware of the complex nature of soils, of the potential of soil contamination, and of types of direct and indirect contacts that human populations have with soil. 

Possible indirect exposure from transplacental and/or translactational exposure Both direct and possible indirect exposure (nursing pups also self-feeding)... 

Wild, L.G., H.G. Ortega, M. Lopez, and J.E. Salvaggio. 1997. Immune system alteration in the rat after indirect exposure to methylmercury chloride or methylmercury sulfide. Environ. Res. 74(l) 34-42. 

Selenium can exist at hazardous waste sites in many forms. However, specific forms have not been analyzed at sites where selenium is reported. At hazardous waste sites, you could be exposed to selenium by swallowing the soil or water, or by breathing the dust. Eating plant products that have taken up selenium from soil and water in areas of high concentration could also result in indirect exposure at regulated waste sites. The form selenium takes at any given time depends on the environmental conditions. This is further discussed in Chapter 6. 

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