Keeping America's Children Out Of Harm's Way

Pediatric Environmental Health:

The environment into which American children are born has chaged in a dramatic way over the past 50 years. This has resulted in many positive outcomes, including lowered infant mortality (although this reduction is not equal across subpopulations). In addition, the classic infectious diseases are greatly reduced in incidence and are no longer the leading cause of illness and death.

American children today are confronted with a group of chronic conditions of multifactorial etiology that have been described as the "new pediatric morbidity." Some forms of childhood cancer have increased substantially, and the incidence and mortality of asthma have more than doubled in the last decade. The incidence of neurodevelopmental and behavioral disorders, dis eases caused by exposure to environmental tobacco smoke, and some congenital defects of the reproductive organs (such as hypospadias) have also doubled over the past two decades (Landrigan, Schecter, Lipton, Fahs, & Schwartz, 2002).

Unfortunately, the etiologies of pediatric developmental disabilities and chronic diseases that are so prevalent in the U.S. today are poorly understood. Familial or genetic origins are thought to account for 10% to 20% of these diseases, with trauma, infections, and obstetrical difficulties accounting for another small percentage. The causes for the vast majority are only beginning to be known and have not previously been explained. The World Health Organization (WHO) confirms that more than one-third of the global burden of diseases among children is due to modifiable environmental factors (WHO, 2006). In the U.S. alone, it is estimated that the total costs of environmentally attributable pollutant-related diseases (such as lead poisoning, asthma, and cancer) is $54.9 billion annually (Landrigan et al., 2002).

Chemicals in the Environment

Over the past two decades, an emerging body of evidence has pointed to the exposure of children to toxic chemicals in the environment as a cause or contributing factor to certain types of these diseases. The U.S. National Academy of Sciences estimates that environmental exposures contribute to the development of approximately 28% of neurobehavioral disorders in children. Exposures may include even a variety of chemical exposure in utero or after birth (National Academy of Sciences Committee on Development Toxicology, 2000). These chemicals include methyl mercury (found in certain fish including shark, swordfish, King Mackerel, Tilefish, and albacore tuna), lead, polychlorinated biphenyls (also found in some fish), and certain pesticides. Prenatal exposures to certain chemicals have been linked to elevated risks for many birth defects and illnesses including pediatric cancers like leukemia. Shu et al. (2004) linked parental occupational exposures to hydrocarbons (such as chlorinated solvents, benzene, and paints) to elevated leukemia risk in their children.

Children have extensive exposure to synthetic chemicals in toys, home furnishings, clothing, food, and water. More than 80,000 synthetic chemicals have come into production and commercial usage in the last 50 years. A group of chemicals, the so-called high-production volume chemicals (produced in quantities greater than one million pounds per year) are widely dispersed in water, air, soil, food, communities, waste sites, schools, and even homes. Although most Americans assume that these chemicals are tested for safety, approximately half of them have not been tested for basic toxicity (Chalupka, 2005). This lack of data about acute and chronic toxicity, developmental and reproductive toxicity, and mutagenicity (the ability to cause changes or mutations at the chromosome or gene level) poses a threat to children in particular because of their unique susceptibilities.

Unique Susceptibilities

Several factors influence an individual's risk for environmentally related illness. Among them are age, gender, previous/concomitant exposure, poverty, race, and genetic endowment. The risk for children is a particularly complex problem because of their unique behavioral factors, toxicokinetic patterns, differential susceptibility that changes through various periods of development, and longer life span.

Behavioral Factors

Children are highly vulnerable to chemical toxicants because of their disproportionately heavy exposures. From birth, they breathe more air, drink more water, and eat more food than an adult. An infant's respiratory rate is double that of an adult. From birth to age 6 months, children drink 7 times as much water, and from 1 to 5 years of age consume 3 to 4 times more food than adults. The relatively small variety of foods that characterizes the diet of a young child may lead to increased exposure to contaminants unique to certain foods including pesticides used on fresh fruit. Even normal play at ground level (where dust and chemical residue settles) and hand-to-mouth activity further magnify their exposure. Finally, the higher surface area to body mass ratio increases exposure to toxicants that are absorbed dermally (Agency for Toxic Substances and Disease Registry [ATSDR], 2002).