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. 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.''
The higher cancer rates don't prove working overnight can cause cancer. There may be other factors common among graveyard shift workers that raise their risk for cancer.
Some research also suggests that men working at night may have a higher rate of prostate cancer.
Because these studies mostly focused on nurses
and airline crews, bigger studies in different populations are needed to confirm or disprove the findings.
There are still plenty of skeptics. And to put the risk in perspective, the ''probable carcinogen'' tag means that the link between overnight work and cancer is merely plausible.