How can every community with the fear of a health hazard in its midst get the help it needs from overworked or indifferent public health agencies?

The authors of "The Health Detective's Handbook," all affiliated with the University of Texas, encourage citizens to conduct their own research to document genuine problems with their earth, air or water -- evidence that can force government to act.

Their leading example is Love Canal, near Niagara Falls, N.Y., where concerned homeowners were not only the first to alert government officials to the tragic health problems caused by toxic chemicals, but also "did a far better job of evaluating the health of the community than did the professionals of the New York Health Department," according to Marvin S. Legator, one of the authors of the handbook and former chief of the Genetic Toxicology Branch of the Food and Drug Administration.

The so-called amateurs may not always surpass the skill of professionals trained in science and probability, but they do have the advantage of greater personal interest, energy and manpower. Still, professionals should not fear that this practical guide will unleash thousands of greenhorn sleuths crying "cancer" at every turn. If the advice of the authors is followed, this handbook could go a long way in preventing citizens from sounding false alarms.

For example, the authors take care to detail how suspicious clusters of birth defects, among other problems, may just be chance. There are step-by-step instructions for writing community questionnaires, determining the expected frequency of disease, how to fairly compare death rates, set up control groups and the like.

As much as the authors tried to simplify these steps, it is unlikely that many citizens groups will deal with the intricacies of chi-square analysis or ask their neighbors fairly personal questions about birth control and fertility, both of which are suggested. What will be of value is the easy-to-understand listings of cancer-causing agents, industrial processes linked to cancer and the research and dispassionate analysis that must be undertaken before alarm bells are sounded. In other words, this book should warn off those calling for the TV cameras at the discovery of the first rusty barrel.

There also are invaluable chapters on how to get help from state and federal agencies once it is determined that help is needed. But what is worth the price of the book is a 32-page resource guide, compiled by the Farmworker Justice Fund, which lists experts in epidemiology, biostatistics and public health, testing labs, as well as computer data bases, journals, libraries and directories devoted to the issues surrounding health and the environment. From a firefighter worried about the health effects of his job to a homeowner concerned about the effects of termite-killing chemicals, the person, agency or publication with an answer is listed here.

The enormity of America's toxic legacy is an emotional and frightening issue, but the "Health Detective's Handbook" arms citizens with procedures for turning the unknown into the factual.