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

It is a surprising step validating a concept once considered wacky. And it is based on research that finds higher rates of breast and prostate cancer among women and men whose work day 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.(source)