Gulp.

Still, it is hard not to be sympathetic to Morris's claims, which rely in part on the same crack epidemiological detective work used by Snow 150 years ago. Indeed, I switched from tap to bottled water while reading his book (although Morris also warns that bottled water "is less closely regulated than tap water and is not required to meet stricter standards for purity").

Loretta Schwartz-Nobel is a journalist, not a scientist, but if anything her outrage is even greater than Morris's. In "Poisoned Nation," she describes a series of diseases, ranging from asthma to cancer, that she believes are on the rise due to pollution. Her book has a much more conspiratorial tone. She is largely uninterested in presenting both sides of the issues in question, even when defenders of the status quo are respected scientists and government agencies.

For example, she tells the now familiar story of how childhood vaccines containing the mercury additive thimerosal supposedly led to an enormous rise in cases of autism. Similarly, she charges that companies in the forefront of breast cancer awareness campaigns produce the very environmental toxins that cause the disease.

To be sure, Schwartz-Nobel is right when she points out how profits and politics led industry to conceal the potential dangers of mercury in tuna and other foods. Similarly, the breast cancer movement only recently has turned from a focus on mammography and chemotherapy to investigating the connection between toxic waste and cancer rates. And she tells compelling stories about individuals with autism and breast cancer whose diseases seem to have emerged just after a toxic exposure. One such person was Chris, a bright 2-year-old who, after a reaction to a vaccine, "could no longer concentrate on his books or anything else for more than a few seconds." Eventually, he was diagnosed as having severe learning disabilities.

But what does one do with this information when organizations such as the esteemed Institute of Medicine, one of the four U.S. National Academies, have found no association between thimerosal and autism? Or when the Long Island Breast Cancer Study did not find evidence that toxins were responsible for high rates of the disease? It is hard to accept, as Schwartz-Nobel apparently does, that the scientists involved in these studies make decisions based mostly on industrial connections and political pressure.

A big part of the problem, both books acknowledge, is the difficulty of achieving definitive scientific proof when trying to determine causes of disease outbreaks. Such studies, which rely on retrospective data and participants' recollections, are notoriously difficult to carry out.

So it is disappointing that neither book mentions the so-called precautionary principle, a moral and political argument often invoked by activists when there is no scientific consensus about potential harms. In this case, the principle would argue that society should err on the side of cleaning up possibly toxic environmental waste.

Rather than characterizing industry as villains, it is time for critics such as Morris and Schwartz-Nobel to enlist activists, government and business in constructive partnerships. But this effort will require engaging the public, which can then put pressure on politicians. In making this point, Schwartz-Nobel quotes longtime breast cancer activist Barbara Brenner: "We figured that if people really knew what was happening with the Cancer Industry, they would be furious."

Unfortunately, such anger has not yet materialized over breast cancer or other diseases with possible environmental causes. If, despite their limitations, these books alert the public to such environmental connections, they are doing a great service.