This afternoon, I attended a briefing on Capitol Hill about light pollution, a subject that has filled many of my notebooks. A representative of a major utility company, a conservation scientist, a medical researcher, and other experts addressed a roomful of congressional staffers in an effort to move the federal legislature to take action against wasteful artificial lighting. Several states, including Texas, and hundreds of towns across the country, including Homer Glen, Ill., have taken measures to control how much light gets cast into the sky rather than onto targets on the ground. But the federal government has not made rules aimed at limiting light pollution.
One presenter, biologist Travis Longcore of the Urban Wildlands Group in Los Angeles, ran through a litany of species that are harmed by misdirected illumination, such as migratory birds, which can become disoriented and crash fatally into lighted towers, and sea turtle hatchlings, which can be lured away from the sea—and to their inevitable death—by illuminated roadways. Another presenter, David Blask of the Bassett Research Institute in Cooperstown, N.Y., focused on explaining why nocturnal illumination is linked to health problems in one important species in particular: humans.
I've covered the harmful effects of artificial light elsewhere, so I won't rehash them here. But it's worth mentioning that the June 18 issue of the Journal of the National Cancer Institute describes yet another scientific advance in our understanding of why women who work in lighted conditions during the night have elevated rates of breast cancer. Eva Schernhammer of Harvard Medical School and her colleagues report that postmenopausal women who have low levels of melatonin, a hormone that the body makes primarily when it's dark, are more likely to develop breast cancer.
Schernhammer previously led a study that found that women who work at night, such as nurses who work the graveyard shift, are at high risk of breast cancer. That finding, published in 2001, was among the first scientific hints that frequent exposure to light at night can lead to health problems. Since then, shift work has been labeled a probably human carcinogen by a branch of the World Health Organization.