Age-specific exposures

A child s anatomy, physiology, and metabolism change over time, as well as their behaviour and interaction with their 

The exposure pathway and physicochemical characteristics of a particular environmental chemical can provide useful information on the likelihood of childhood exposure (chapter 5). Age-specific exposure pathways of particular relevance include those during the prenatal and early developmental years postnatally (e.g. placental transfer, breast milk, toys, soil, indoor air/dust, child-care centres). Exposures to persistent environmental chemicals are of special concern, since the internal exposure may continue and result in a level sufficient to cause effects during critical developmental stages, even after the external exposure has ceased or been removed. 

At birth, the child is exposed to the environment directly. At this time, the child s respiration rate is rapid, food and water 

Infants/toddlers are small in stature, crawling or just beginning to walk, and prone to be in contact with rugs, floors, lawns, and compounds that layer at low levels. The limited variety of their diets may shield them from many exposures, but may make them particularly vulnerable to others. This is especially true if the exposure pathway of an agent is through particular foods that comprise a large portion of the diet, such as fruits and milk or milk products. This is also the stage at which hand-to-mouth behaviours may result in exposure. 

Default values have been published for use in estimating exposures — for example, from food and water consumption in adults and children, soil ingestion in children, and respiration rates in children and adults (USEPA, 1990). The Child-Specific Exposure Factors Handbook summarizes data on human behaviour and characteristics that affect children s exposure to environmental agents and recommends values to use for these factors (USEPA, 2002a). 

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Persons with a history of convulsive disorders would be expected to be at increased risk from exposure to endrin. Children may be more sensitive than adults to the acute toxic effects of endrin. In an endrin poisoning episode in Pakistan, children 1-9 years old represented about 70% of the cases of convulsions (Rowley et al. 1987). The causative factor responsible for the outbreak was not identified, however, and the age distribution of cases could be explained by age-specific exposure situations. In general, following oral administration, female animals appear to be more susceptible to endrin toxicity than males (Gaines 1960 Treon et al. 1955). The difference may be due to the more rapid excretion of endrin by male versus female rats (Hutson et al. 1975 Klevay 1971 Korte et al. 1970). A sex-related difference in toxicity was not apparent following dermal exposure (Gaines 1960, 1969). No sex-based differences in endrin-related... 

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