from the Brocktown News, Nevada

LONDON – Like UV rays and diesel exhaust fumes, working the graveyard shift will soon be listed as a “probable” cause of cancer.

Next month, the International Agency for Research on Cancer, the cancer arm of the World Health Organization, will add overnight shift work as a probable carcinogen. The American Cancer Society says it will likely follow. Up to now, the U.S. organization has considered the work-cancer link to be “uncertain, controversial or unproven.”

However, scientists suspect that overnight work is dangerous because it disrupts the circadian rhythm, the body’s biological clock. The hormone melatonin, which can suppress tumor development, is normally produced at night.

Among the first to spot the night shift-cancer connection was Richard Stevens, a cancer epidemiologist and professor at the University of Connecticut Health Center. In 1987, Stevens published a paper suggesting a link between light at night and breast cancer.

But in recent years, several studies have found that women working at night over many years were indeed more prone to breast cancer. Also, animals that have their light-dark schedules switched develop more cancerous tumors and die earlier.

Because these studies mostly focused on nurses and airline crews, bigger studies in different populations are needed to confirm or disprove the findings.

Among the long list of agents that are listed as “known” carcinogens are alcoholic beverages and birth control pills. Such lists say nothing about exposure amount or length of time or how likely they are to cause cancer. The American Cancer Society Web site notes that carcinogens do not cause cancer at all times.

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