The following appears in a box on page 47 of the printed report.

Measuring the Effectiveness of a Risk Management Action

Few actions to reduce health or ecosystem risks lend themselves easily to measurement and validation. For example, it is difficult to observe changes in cancer risk because it can take many years for a tumor to develop after exposure occurs. Some other effects are easier to observe because they can appear soon after exposure—such as birth defects, anemia from lead, and asthma from sulfur oxides in the air. Relationships between action and effect often are detectable only when the action causes a sizable change in how much of a pollutant (or other stressor) populations are exposed to, or when the health effect of interest is easy to recognize because it is rare and distinctive (such as the unusual type of liver tumor caused by breathing vinyl chloride in the workplace).

One difficulty in measuring effectiveness is that most environmental health risks are low compared with the risks of such directly countable effects as occupational injuries, motor-vehicle collisions, infant mortality, total cancer rates, and total birth defect rates. For example, suppose that a particular exposure is expected to cause no more than one additional case of cancer per year in a population of 10,000 and action is taken to reduce exposure to a level anticipated to cause, at most, one additional case of cancer per year in one million people (corresponding to one extra case per 100 years in that population of 10,000). With or without this action, cancer still will be the cause of death in 24% of the population. No health study or surveillance activity can measure the very small decrease in cancer incidence that would occur at the lower exposure level. Instead, risk managers must rely on indirect measures that indicate cancer incidence may decrease—such as decreased emissions, decreased exposure, and possibly decreases in biological markers of exposure or effects.

Progress is needed in several areas if we are to improve our ability to implement and measure the effectiveness of public health interventions. Specifically, we need to: