such as domoic acid. Toxic chemicals in food can be divided into three categories: (1) pesticides that have been deliberately applied to the food source; (2) colors, flavors, or preservatives deliberately added to food during processing; and (3) chemicals that inadvertently enter the food chain, such as PCBs, heavy metals, and persistent pesticides such as DDT. Particular effects of food contaminants on children include such behavior changes as hyperactivity (Carter et al., 1993) and developmental neurotoxicity from pesticide exposure in food (National Research Council, 1993).

Infectious Agents

Children also are a demographic subgroup prone to infectious diseases because of their exploratory behavior, lack of prior exposure to most infectious agents, and association with other children. Substantial advances in vaccines have reduced rates of many infectious diseases during the past decades. Nonetheless, infectious agents remain a major threat to children’s health, particularly with the increase in antibiotic resistance among various infectious organisms and the emergence of new infectious agents (i.e., new strains of flu).

Children are highly exposed and susceptible to some infections that are spread by droplets from coughing and sneezing. Respiratory syncytial virus, the leading cause of serious upper and lower respiratory tract infection in infants and children, accounts for 125,000 hospitalizations and 450 deaths annually in the United States, and it may predispose children to asthma later in life. Annual epidemics occur from November to April, and virtually all infants are infected by age 2 (Black, 2003). Cytomegalovirus infection is spread in child care centers through both urine and saliva containing live virus; rates for preschool-age children in the United States range from approximately 5 to 30 percent (Centers for Disease Control and Prevention, 1985). Children are also particularly susceptible to other infectious agents, such as rotavirus and Norwalk virus, salmonella, and E. coli O157:H7, which cause diarrhea and dehydration and sometimes severe complications.

Children are also more highly exposed to vector-borne (e.g., via ticks, fleas) or certain zoonotic (e.g., hosted by dogs, cats, horses) pathogens due to their increased time outdoors, play activities, and behaviors. Vector-borne pathogens include Lyme disease, highest among 5–9-year-olds (Centers for Disease Control and Prevention, 2002a), and Rocky Mountain spotted fever, most prevalent under age 10 (Centers for Disease Control and Prevention, 2000b). Some arboviruses, which are transmitted by different species of mosquitoes, preferentially infect the young (e.g., La Crosse encephalitis carried by a woodland mosquito; Centers for Disease Control and Prevention, 1990a, 1998a). Cat scratch disease, carried by cats, has an estimated annual incidence of 22,000 cases, with the highest age-specific incidence in children less than age 10. Up to 25 percent of

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