Laboratory animal tests and human cancer.

The use of the results of laboratory animal tests to predict human cancer is effective in identifying potential human carcinogens before human exposure, permitting measures to be taken to prevent that exposure, a foolproof way to prevent human cancer. The purported, and highly publicized, faults of these tests, when examined critically, are shown not to be significant. Most chemicals are not carcinogenic; only about 1 in 10 are truly carcinogenic. The high doses used to maximize sensitivity do not produce false positives. All human carcinogens are carcinogenic in laboratory animals, and almost all animal carcinogens for which there is human exposure, when analyzed by epidemiological studies, show responses that are not statistically different. Most carcinogens are not banned, some are regulated, but many are not. The claimed costs of these health regulations are typically overestimated, and often greatly overestimated. Using the results of laboratory animal studies is good science and good public health.

Can laboratory animal carcinogenicity studies predict cancer in exposed children?

A key to the prevention of childhood cancer is the control of carcinogens to which children are exposed. The first step in this process is to identify those chemicals that are likely to cause cancer in children. The best way to identify carcinogens, today, is the use of the rodent lifetime cancer test--the bioassay. The test has vocal critics, but is adequately reliable if properly used. Perhaps the major criticism concerns the use of the maximum tolerated dose as the highest dose tested. Critics claim that this dose causes cellular killing. The resultant cellular proliferation "fixes" preexisting mutations that can lead to cancer. This occurs but in a small fraction of the tests, and the high dose is necessary to achieve statistical sensitivity. All human carcinogens have been shown, when properly studied, to be carcinogenic in rodents. Many human carcinogens were first shown to cause cancer in rodent tests. Regulators rarely ban chemicals that have been demonstrated to be carcinogenic. Further, most chemicals in use today have not been properly tested. The potential errors in the rodent cancer test seem small when compared to the errors in the economic projections of the effects of restricting chemicals. Although not perfect, the rodent cancer test, when used properly, can help protect our children, and us, from cancer.

Disease-causing effects of environmental chemicals.

Both toxicologic studies and studies in environmental chemistry are important in assessing the potential adverse health effects of human exposures to hazardous environmental agents. This article discusses the toxic effects of chemical concentration at the target organ or site and how the concentration is related to the level of external exposure.

Toxic agent and radiation control: progress toward objectives for the nation for the year 1990.

In 1980, the Department of Health and Human Services set national prevention objectives for 1990 in 15 health priority areas, 1 of which is the control of toxic agents and radiation. Ten objectives related to this area are priorities for the national control effort. Progress is reviewed on those priorities within the responsibilities of the Public Health Service. Six key program elements, or types of support activities, are deemed essential to preventing, identifying, and controlling toxic agent and radiation threats. Significant progress has been made toward achieving objectives for which all key program elements have been successfully implemented to provide the requisite know-how, manpower, and tools. Important advances have been made in reducing the blood lead levels of the population, reducing unnecessary exposure to medical X-rays, evaluating the toxicities of chemicals in toxic waste dumps, and improving the scientific and technical information base and its availability for prevention and control efforts. The most important priority for the forseeable future will be to expand our knowledge of potential health risks posed by toxic agents and radiation. Expanded surveillance systems and data bases are essential to determining the extent of the problems in terms of human health effects and for measuring the impact of prevention programs. Emphasis on the activities embodied in the key elements will encourage the expansion of the knowledge base and its effective application to prevention and control problems.