Visualizing Environmental Science

Determining Health Effects of Pollutants 89

body weight as an adult. This means that a child also

breathes more air pollutants into the lungs. A 1990 study

in which autopsies were performed on 100 Los Angeles

children who died for reasons unrelated to respiratory

problems found that more than 80 percent had subclini-

cal lung damage, which is lung disease in its early stages,

before clinical symptoms appear. (Los Angeles has some

of the worst air quality in the world.)

1. What is a dose–response curve?


2. What is one way that scientists determine
   whether a chemical causes cancer? What are
   two problems with this method?


3. What are the three ways that chemical mixtures
   interact?


4. Why are children particularly susceptible to
   toxicants?

potential risks from exposures. Consequently, they are
often more susceptible than adults to the effects of chem-
icals. Consider a toxicant with an LD 50 of 100 mg/kg. A
potentially lethal dose for a child who weighs 11.3 kg (25
lb) is 100 × 11.3 = 1130 mg, which is equal to a scant ¼
teaspoon if the chemical is a liquid. In comparison, the
potentially lethal dose for an adult who weighs 68 kg (150
lb) is 6800 mg, or about 2 teaspoons. Consequently, poli-
cies designed to protect children from chemical expo-
sures must account for these differences.

Children and Pollution Consider the toxicants in
air pollution. Air pollution is a greater health threat to
children than it is to adults (Figure 4.14). Lungs con-
tinue to develop throughout childhood, and air pollu-
tion restricts lung development. In addition, a child has a
higher metabolic rate than an adult and therefore needs
more oxygen. To obtain this oxygen, a child breathes
more air—about two times as much air per pound of

Daniel LeClair/Reuters/Landov

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A Honduran mother gives oxygen to her baby, who suffers from environmentally linked respiratory disease. Farmers nearby burn
land to prepare for the planting season; the resulting smoke triggers breathing problems, mostly in children and the elderly.