LONDON — Like UV rays and diesel exhaust fumes, working the graveyard shift will soon be listed as a “probable” cause of cancer. It is based on research that finds higher rates of breast and prostate cancer among women and men whose workday starts after dark.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.”
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. Experts estimate that nearly 20 percent of the working population in developed countries works night shifts.
