UNIQUENESS AND STAGES OF DEVELOPMENT OF THE CHILD AFFECTED BY ENVIRONMENTAL STRESSES
(See endnotes 2, 11)
This presentation will examine, without going into great specifics, the unique physiological and behavioral traits of the fetus and child and how they respond to environmental pollutants; the several different environments the child is exposed to and subsequent potential increase in disease and injury; and various problems and sub-problems of high-level and low-level exposure to environmental contaminants.
The child is recognized as a distinct entity with varying responses to the environment based on time of exposure, physiologic maturity, differential reaction to a given exposure, and age of the child. The exposed fetus or infant may have many more years than the adult to develop a particular disease due to an exposure to an environmental contaminant. For the infant, toddler and child, differences in his/her physiology, metabolic rate, mobility, increased surface area of body to in relation to body mass, as well as body weight, consumption of water and food and intake of air, especially close to the ground, potentially create additional burdens from levels of environmental contaminants that might even be safe for adults. The differences in behavioral patterns of children, such as considerable hand-to-mouth contact, eating of dirt, constantly exploring the environment and tasting inedible things, may lead to the ingestion of environmental contaminants. Chronic low- level exposures to chemicals and metals further complicate the potential for disease in children. An infant’s respiratory rate is twice that of an adult. In the first 6 months of life, children consume seven times as much water per kilogram of body weight as an adult does. From 1 to 5 years of age, children consume three to four times more food per kilogram of weight than an adult. Children have fewer dietary choices. Some toxicants can penetrate a child’s skin much more readily than that of an adult.
Exposure of the child to toxic substances which may lead to disease is determined by the toxicity of the substance, the route of exposure, and the various host factors. In order for a disease to occur as a result of a given environmental contaminant, it must:
- • Be dispersed into the environment
- • Be in a medium to which the person is exposed
- • Be in a medium which enables biological uptake of the substance
- • Be absorbed into the body after exposure
- • Cause a biological change in the person
- • Affect a target organ adversely
- • Create clinical symptoms of disease in a person
Environmental contaminants are found in air, water, soil, and food sources. The route of exposure is through breathing, skin, eating, and drinking, through the placenta or intravenously. The contaminants may be found in: agriculture, such as pesticides and fertilizers; occupational settings, such as solvents and other chemicals; incinerators, such as a variety of hazardous air pollutants and particulate matter; mobile sources, such as particulate matter and gases such as nitrogen oxides, sulfur oxides, and carbon monoxide; in folk medicines and special cosmetics, such as lead and other heavy metals; in the home, school, and recreational environment; and brought home from the occupational environment. A new potential threat is the terrorist attack, which can create a multitude of very serious air pollutants which can be inhaled by people within a reasonable distance of the attack, can be consumed in food or water, or contaminants which can be absorbed through contact with various parts of the body.
It is estimated that in the first 5 years of life, a child will consume an estimated 50% of the pesticides that the individual will ingest over a lifetime. About 80% of the individual’s lifetime exposure to damaging ultraviolet light occurs before 18 years of age. Despite the reduction in lead poisoning from leaded gasoline, over 1 million children in the United States have elevated blood lead levels, and another approximately 2 million children are at risk of lead poisoning, which can be congenital in nature. Asthma, the most significant of the chronic diseases in children under 18 in the United States, affects approximately 5 million children.
The differences in the child’s daily environment compared to that of the adult, such as in the home, play areas, daycare environment, schools, and school buses, may contribute to the spread of disease and injury, based on exposure to other children and the peculiarities and dangers of those environments. (See Chapter 6, “Environmental and Occupational Injury Control” for additional information on children’s injuries.)