Scientists Dump Cold Water on Environmental, Health Scares
It’s been a difficult couple of months for purveyors of junk science and others actively spreading scientific misinformation on environmental issues.
Where once sensational headlines heralded toxic terror, scientists, to paraphrase Shakespeare, says it was all much ado about nothing. The unraveling began late last October when the New England Journal of Medicine reported on a meticulous study, conducted by the Harvard School of Public Health, which found no evidence that exposure to the chemicals DDT and PCBs is linked to breast cancer.
The following month, an expert panel convened by the American Cancer Society (ACS) reported that trace amounts of pesticides on fruits and vegetables pose practically no risk of cancer to people. Indeed, “a diverse diet that has plenty of fruits and vegetables is very important in reducing cancer,” Dr. Clark Heath of the American Cancer Society told the Associated Press. “Compared to that, the risk of cancer from man-made chemicals is negligible.”
“It’s extremely unlikely that pesticides in the diet have any meaningful contribution to cancer rates,” observed Len Ritter, a Canadian environmental biology professor on the ACS panel and executive director of the Canadian Network of Toxicology Centres. Results of the panel’s study were published in the November issue of the journal Cancer.
The alleged risk of cancer from another source has also been challenged in recent months. According to a review of over 100 studies, reported in the Journal of the National Cancer Institute, there is little evidence that silicone breast implants increase the risk of breast cancer. In fact, the researchers found reason to believe that breast implants could help protect against breast cancer--a possibility they conclude should receive further study.
Saccharin, the low-calorie sweetener of choice for many weight-conscious Americans, may also soon receive a clean bill of health. The National Toxicology Program (NTP), a division of the National Institutes of Health (NIH), has been petitioned by an industry group to remove saccharin from the government’s list of suspected carcinogens. In a move that surprised many scientists, an independent panel asked by the NTP to review the question voted 4 to 3 last October not to recommend that saccharin be delisted.
Speaking for the panel’s majority, Franklin Miller, director of the health and safety department for the United Auto Workers, said the data were “equivocal.” “What I’m saying is,” he told The New York Times, “the epidemiology is perhaps not strong enough to identify saccharin as a carcinogen, but it doesn’t rule out that it’s a risk.”
Miller’s cautious remarks are in sharp contrast to the hysteria that broke out in 1981, when studies were released showing saccharin caused bladder cancer in rats. In the 17 years since the saccharin studies were made public, scientists have become increasingly skeptical of the value of experiments that find that rats fed prodigious amounts of a chemical develop cancer. Rats, it turns out, are highly susceptible to cancer, and their physiology differs markedly from that of humans. Moreover, the amount of saccharin pumped into their bodies bears no relation to the small quantities consumed by humans.
Two government panels have recommended removing saccharin from the list. That decision, which is expected shortly, is in the hands of Kenneth Olden, director of the NTP.
Frog Deformities Get Second Look
At the same time, another rush to judgment--this one involving deformities in frogs--is also getting a second look. In 1995, middle school students on a field trip to a Minnesota wetland were started when they encountered frogs with deformities, including missing limbs in some and too many limbs in others. Similar deformities were reported at other sites in the Midwest, as well as the northeastern, southern, and western U.S. and Canada. While such deformities are not uncommon among roughly 1 percent of frog populations, some sites showed deformities occurring in 10 percent or more of the croaking amphibians.
The Minnesota Pollution Control Agency (MPCA) and the National Institute of Environmental Health Sciences (NIEHS) lost little time in publishing their initial findings on the matter, linking chemicals to the deformities. They were quickly called on the carpet by, of all people, scientists at EPA.
According to the Washington Post, researchers at EPA’s Mid-Continent Ecology lab in Duluth, Minnesota duplicated the experiments conducted by MPCA and NIEHS and arrived at radically different results. “The NIEHS acted irresponsibly in a rush for headlines,” said Gil Veith, associate director at EPA’s National Effects Laboratory. “They overlooked some very basic rules for running bioassays.”
Miscarriages and Sperm Counts
Late last year, the journal Epidemiology reported on a study linking higher rates of miscarriage to exposure to trihalomethanes, a byproduct of chlorine used to purify drinking water. Women who drink five glasses or more of normal tap water daily have shown slightly higher rates of miscarriages than do women who are less exposed to trihalomethanes, the study said. The researchers, however, were quick to underscore the preliminary nature of their findings and emphasized the importance to human health of chlorinating water.
“Miscarriage is a distressing but common event that usually results from natural errors in early embryo development,” explains Anthony R. Scialli, MD, department of obstetrics and gynecology, Georgetown University Medical Center. By far the most common cause of miscarriage are chromosomal abnormalities, followed by increasing age of the mother, hormone levels, maternal immune systems, reproductive tract abnormalities, maternal lifestyle-related exposures (tobacco, alcohol, and caffeine), and some prescription drugs. Exposure to chemicals, notes Scialli, is not among the common causes of miscarriage.
Exposure to man-made chemicals has also been linked to declining sperm counts. Yet the more scientists explore the topic, the more they have become convinced that this issue, too, is far from settled.
The November 1997 issue of Risk in Perspective, published by the Harvard Center for Risk Analysis, cautions, “The question of whether human sperm counts are changing over time has no clear answer in the mixed body of evidence now available. If there is an effect, it is certainly less universal and inexorable than was first suggested. What may be causing any such phenomenon is much less clear, and the hypothesis of chemical exposure is at present mostly speculative.”
In all of these cases, real science has asserted itself at the expense of junk science. Now, even the courts are starting to catch on. In a ruling with far-reaching implications, the U.S. Supreme Court--by an 8 to 1 vote--recently gave federal trial judges broader latitude to throw out conclusions by “expert” witnesses that go beyond valid scientific underpinnings. “A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered,” Chief Justice William H. Rehnquist wrote.