Visualizing Environmental Science

substance. The precautionary principle might require

that all new industrial chemicals be tested for acute and

chronic toxicity before they can be sold.

The precautionary principle is also applied to ex-

isting technologies when new evidence suggests that

they are more dangerous than originally thought. For

example, when observations and experi-

ments suggested that lead added to gasoline

as an anti-knock ingredient was contami-

nating soil, particularly in inner cities near

major highways, the precautionary principle

led to the phase-out of leaded gasoline

(Figure 4.15).

To many people the precautionary prin-

ciple is just common sense, given that science

and risk assessment often cannot provide

1. Discuss the precautionary principle as it relates
   to the introduction of new technologies or
   products.

Y

ou’ve probably heard the expression “An
ounce of prevention is worth a pound of
cure.” This statement is the heart
of the precautionary principle
that many politicians and environmental activ-
ists advocate. According to the precautionary
principle, we should not introduce new
technology, practice, or material until it is
demonstrated that (a) the risks are small and
(b) the benefits outweigh the risks. The pre-
cautionary principle puts the burden of proof
on the developers of the new technology or

The Precautionary Principle

LEARNING OBJECTIVE

precautionary

principle The idea

that new technologies,

practices, or materials

should not be adopted

until there is strong

evidence that they

will not adversely

affect human or

environmental health.

Andy Levin/Science Source Images

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In addition to air pollution, these children are probably exposed to lead in the soil (from leaded gasoline)
and in paint from old buildings. Children with even low levels of lead in their blood may suffer from partial
hearing loss, hyperactivity, attention deficit, lowered IQ, and learning disabilities.