By Joby Warrick
More than 100 major studies in the past 13 years have examined health consequences of passive smoking, and most -- about 63 percent -- found evidence of harm, from respiratory problems to cancer, according to a literature review published in May in the Journal of the American Medical Association.
Of the reports that were inconclusive or found no health effects, nearly three-quarters were written by scientists funded by cigarette companies, the JAMA article said. In fact, it said, the evidence "suggests that the tobacco industry may be attempting to influence scientific opinion by flooding the scientific literature with large numbers of review articles supporting its position."
"This conclusion is consistent with the industry's previous strategies related to tobacco," said the article by Deborah E. Barnes and Lisa A. Bero, whose work was funded in part by the National Cancer Institute.
Friday's ruling by a North Carolina federal judge focused on a 1993 Environmental Protection Agency conclusion that environmental tobacco smoke is a potent carcinogen that causes about 3,000 cancer deaths a year. The judge faulted the EPA for failing to follow standard statistical and scientific procedures. But other studies have backed EPA's contention that passive smoking raises the risk of cancer and other ailments.
Last year, a comprehensive survey conducted by California's environmental protection agency linked secondhand smoke to cancers of the lungs and cervix as well as to an increased risk of sudden infant death syndrome and spontaneous abortion. In September, researchers at the Minnesota Cancer Center reported detecting signs of a cancer-causing substance in the urine of nonsmokers who were exposed daily to high levels of tobacco smoke.
But while the case against secondhand smoke continues to build, proving the cancer link remains problematic. That's partly because of the uncertainties inherent in epidemiological research, weaknesses that make it difficult to prove that anything causes cancer, even smoking itself. Some independent studies continue to find no statistically significant connection between passive smoke and cancer, including a report this year by the International Agency for Research on Cancer, a study funded by the World Health Organization and immediately championed by the tobacco industry.
But cancer risks aside, there's solid evidence linking environmental smoke to serious respiratory illnesses, especially in children. Those alone are sufficient to warrant policies curbing smoking in restaurants and other public places, longtime veterans of the tobacco wars say.
"The tobacco industry focuses on cancer because it's always harder to prove," said Philip Schiliro, staff director for Rep. Henry A. Waxman (D-Calif.). "But what is absolutely undisputed is the impact secondhand smoke has on the respiratory system, especially with kids. With them, there's not a latency period of 40 years before you see the effects. You see it the next day."