Children Are Not Little Adults
Children are affected by environmental contaminants differently from adults. Children typically may be more highly exposed to contaminants and are more vulnerable to their toxic effects.
Children generally eat more food, drink more water, and breathe more air relative to their size than adults do, and consequently they may be exposed to relatively higher amounts of contaminants. Children's normal activities, such as putting their hands in their mouths or playing on the ground create opportunities for exposures to contaminants that adults do not face. In addition, environmental contaminants may affect children disproportionately because their immune defenses are not fully developed or their growing organs are more easily harmed.
Children's environmental health is important because children experience:
Children, beginning in the womb and continuing through adolescence, are in a dynamic state of growth, with cells multiplying and organ systems developing at a rapid rate. At birth their nervous, respiratory, reproductive and immune systems are not yet fully developed. Young children breathe more rapidly and take in more air in proportion to their body weight than do adults.
Different Absorption Rates
The rate at which children absorb nutrients during digestion is likewise different than the rate for adults, a fact that can affect their exposure to toxicants. For example, children have a greater need for calcium for bone development than adults and will absorb more of this element when they eat it. When lead has been swallowed, however, the body will absorb it in place of calcium. An adult will absorb 10 percent of swallowed lead, while a toddler will absorb 50 percent of swallowed lead.
Because metabolic systems are still developing in the fetus and child, their ability to detoxify and expel toxins differs from that of adults. This difference is sometimes to the child's advantage, but more frequently they are not able to get rid of toxins as well as adults, and thus are more vulnerable to them. Not only does a child's bodily processes differ from an adult's, so does its environment. In its first environment, its mother's womb, the fetus may be permanently damaged by exposure to a wide variety of chemicals that can cross into its bloodstream through the placenta. These chemicals include lead, polychlorinated biphenyls, methylmercury, ethanol and nicotine from environmental tobacco smoke.
Behaviors characteristic of early childhood also affect a child's exposure to toxicants. A child spends hours close to the ground where he or she may be exposed to toxicants in dust, soil and carpets as well as to pesticides in low-lying layers of air.
Normal development in early childhood includes a great deal of putting hands in mouths, providing another avenue for exposure to harmful things like lead in paint dust or chips and pesticide residues.
Children also spend more time outdoors than most adults and are often engaged in vigorous play. Because children breathe more air per pound of body weight than adults and because their respiratory systems are still developing, they are prone to greater exposure to and potential adverse effects from air particulates, ozone and other chemicals that pollute outdoor air.
Finally, a child's diet differs in important ways from an adult. Because children eat more fruits and vegetables and drink more liquids in proportion to their body weight, their potential exposure to harmful things when swallowed such as lead, pesticides, and nitrates is greater. For example, the average infant's daily consumption of six ounces of formula or breast milk per kilogram of body weight is equivalent to an adult male drinking 50 eight-ounce glasses of milk a day. Likewise, proportionate to its body weight, the average one-year-old eats two to seven times more grapes, bananas, pears, carrots and broccoli than an adult.
The Arizona Department of Health Service's Summary of Primary Environmental Health Factors is now available online.