Citizens frequently organize around environmental issues on which little scientific evidence exists to back activists' claims. Should we then dismiss such claims as spurious? Or should we side with citizens against the polluters? The author aims to take neither path. In exploring the problem of scientific uncertainty about links between pollution and public health, Sylvia Noble Tesh shows that much of the problem can be traced to the newness of the environmental movement. The inability of scientists to find data corroborating citizens' claims stems partly, she says, from the "pre-environmentalist" assumptions still influencing the environmental health sciences. On the other hand, the conviction of activists that industrial pollutants threaten their health results from the enviromental movement's success in promoting new ideas about nature. Tesh points to ways that environmentalist ideas have begun to affect science, thus making more likely the discovery of links between exposure to industrial pollutants and a community's health problems. Those ways include the expansion of diseases construed as environmental in cause, the study of society's most vulnerable citizens in determining safe levels of pollution and a new focus on the effects of exposure to chemical mixtures.