EXPOSURE ASSESSMENT OF CHILDREN

Children s environmental health risks result from exposure of the parents before conception and of the child during the prenatal period and through childhood and adolescence. In this context, a child can be defined by a series of life stages from conception through adolescence, where each life stage has distinct anatomical, physiological, behavioural, and/or functional characteristics that contribute to potential differences in exposure, resulting in overall differences in susceptibility. 

Children, like adults, may be exposed to chemicals through the air they breathe, the water they drink, the foods they eat, and the surfaces and materials they contact. Children also have unique routes of exposure, including transplacental exposure for the developing fetus and ingestion of breast milk for infants. Because of their unique physiology and behaviour, children s exposures may be higher than those of adults as a result, children may have greater health risks than adults in the same environments. 

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The exposure assessment characterizes the pathways, magnitude, frequency, and duration of human exposures from various sources. Chapter 5 provides an overview of these components and addresses the principles of exposure assessment in children. General principles of exposure assessment have been reviewed in a number of publications (USEPA, 1992a, 2005a IPCS, 1999a, 2000 Needham et al., 2005). This chapter will focus on the considerations that are important when applying the exposure data to a children s health risk assessment (see Box 2). 

Approaches for aggregating exposure for simple scenarios have been proposed in the literature (Shurdut et al., 1998 Zartarian et al., 2000). The USEPA s National Exposure Research Laboratory has developed the Stochastic Human Exposure and Dose Simulation (SHEDS) model for pesticides, which can be characterized as a first-generation aggregation model and the developers conclude that to refine and evaluate the model for use as a regulatory decision-making tool for residential scenarios, more robust data sets are needed for human activity patterns, surface residues for the most relevant snrface types, and cohort-specific exposure factors (Zartarian et al, 2000). The SHEDS framework was used by the USEPA to conduct a probabilistic exposure assessment for the specific exposure scenario of children contacting chromated copper arsenate (CCA)-treated playsets and decks (Zartarian et al, 2003). 

Assessment of children exposure doses to ultrafine particles in primary schools... 

Fernandez, F.J. (1975). Micromethod for lead determination in whole blood by atomic absorption with use of the graphite furnace. Clin. Chem., 21, 558-561 Hansen, O.N., Lyngbye, T., Trillingsgaard, A., Beese, I. and Granjean, P. (1985). A neuropsychological and behavioral assessment of children with low level lead exposure. In Lekkas, T.D. (ed.) Heavy Metals in the Environment. (Edinburgh CEP Consultans)... 

The exceeded value for children via the environment from exposure to dioctyltin (356% of the TDI) relates to the consumption of local produce close to a PVC processing plant and largely derives from default values on release to the environment. Further refinement of this exposure assessment is currently under way. Until this is clarified, dioctyltin remains a compound of concern via this exposure route for children. 

Exposures of Children. More studies are needed to assess the exposures of children living in agricultural areas to methyl parathion residues in air, soil, or water. More studies are also needed to assess the exposures of children in the general population to residues of methyl parathion that might be present in food, milk, or water, or on contaminated clothing and skin from occupationally exposed household members. 

Exposures of Children. Data need to be developed to properly assess the exposure of infants who eat processed baby foods containing residues of pesticides such as endosulfan. Several studies have estimated exposure based on endosulfan concentration found in foods typically eaten by infants however, no studies that directly studied infant exposure could be located. Attention should also be given to infant formulas and to the tap water used to prepare infant formulas from condensed or powdered forms. More data are also required to properly assess endosulfan exposure to children who live, play, or attend school near farmlands that are treated with endosulfan. Maps that catalog endosulfan use on crops and present average application rates would better allow an assessment of the potential for children in farming communities to be exposed. The possibility that farming parents work clothes and shoes may carry endosulfan residues into the home also should be studied. In addition, home use of endosulfan, which may result in exposure of children, needs to be investigated. 

One common objective of an LSMBS is to refine the estimates of actual exposure of consumers to ingredients or impurities in one or more products. For example, study results might be intended to determine a realistic human dietary exposure to pesticide residues in fresh fruits and vegetables. The advent of the Food Quality Protection Act of 1996 (FQPA) has produced an enhanced focus on the exposure of children to pesticides. A well-designed and implemented LSMBS would afford the opportunity to delineate better the exposure and risk to children and other population subgroups. The LSMBS would provide consumer-level data at or near the point of consumption, allowing the refined, relevant, and realistic assessments of dietary exposure. 

Exposures of Children. Children will be exposed to americium in the same manner as adults in the general population (i. e., ingestion of food and water and inhalation of air). Americium is potentially found at hazardous waste sites at elevated levels. Since children may have oral exposure to soil through hand-to-mouth activity, bioavailability studies of americium in soil via the oral route may be useful to assess the risk of this type of exposure. 

The only information that provided an assessment of exposure of children and adolescents to hydrogen sulfide was that developed during the South Karelia Air Pollution Study (Mortilla et al. 1994b) however, these exposures were complicated by simultaneous exposure to other sulfur-containing compounds as well as particulates. Additional exposure information is needed from communities where only hydrogen sulfide exceeds background levels. 

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