The designation by the International Agency for Research on Cancer, or IARC, puts shift work in the same classification as exposure to PCBs or anabolic steroids, and it could shake up the American workforce. Agencies like the EPA, FDA and OSHA take findings by IARC very seriously.
This comes after decades of study by a disparate collection of researchers looking at light exposure, circadian rhythms, and cancer. Richard Stevens, an epidemiologist at the University of Connecticut Health Center started exploring this link while studying the mystery of breast cancer. He spoke on WNPR's Where We Live: "We just don't know why breast cancer is so common in the industrialized world. We used to think it was changes is diet and lots of fat, but that has not panned out. So, beginning about 20 years ago we started thinking about what else changes with industrialization. Lighting changes, people doing shift work, people not getting enough dark."
That "lack of dark" supresses the production of the hormone melatonin. But, that's just one of many connections considered by the WHO, including diet, sleep schedule, and exposure to outside agents at times when the body is more vulnerable. Vincent Cogliano is head of the IARC program: "We decided to look at this because we do try to indentify all causes of human cancer. When we saw several studies in the publised literature over the last several years indicating this, we thought that this would be a good topic for review."
The findings are being released in the journal "Lancet Oncology." Dr. Richard Stevens says a new area of study will focus on a different class of worker; those who get up very early in the morning.