Burning the midnight oil increases the risk of cancer - and bosses should consider the dangers of shift work alongside other on-the-job health hazards, experts say.
Working the late shift overnight is a cancer risk on a par with exposure to diesel exhaust fumes and insecticides in the workplace, a Cancer Society and Massey University public health conference has been told.
Researchers are now likening deaths from cancers caused in the workplace to the road toll, and say more needs to be done to highlight dangerous - and lesser-known - carcinogens.
And there is increasing pressure for workplaces to change their cultures around sun protection for outdoor workers, with skin cancer estimated to account for about 80 per cent of new cancers each year.
Aaron Blair, of the US National Cancer Institute, said the dangers of shift work were a growing concern, as globalisation and technology meant more people were working nights.
Up to 25 per cent of the world's population were now shift workers, he said.
"It is pretty clear that shift work affects breast cancer, and there is emerging evidence that links it to ovarian cancer and prostate cancer.
"Shift work also affects the immune system, so this has an impact too."
The main danger of shift work was that it interrupted natural circadian rhythms, increasing exposure to artificial light and preventing the body from producing the hormones that would usually be replenished with sleep.
International research was focused on identifying the extent of the cancer link, and developing different types of lights to reduce harsh glare at night.
In 2009, the Danish Government began paying compensation to women who had developed breast cancer after sustained night work.
Massey University researcher Andrea 't Mannetje said about 8 per cent of all cancer in New Zealand was linked to workplace carcinogens, a number that rose to about 25 per cent for blue-collar workers.
There were more than 50 known human carcinogens in New Zealand workplaces, including asbestos, benzene, and sun exposure, and more than 100 other possible or probable ones.
Some of the lesser-known carcinogens included viruses, pharmaceuticals, wood dust and shift work - and those needed attention too, she said.
"We can't [hazard] label a piece of wood, we can't label a piece of steel, we can't label dirty laundry from a hospital, though it may be contaminated with carcinogenic drugs . . . the question is about how we will deal with these exposures."
Those most at risk worked in agriculture, construction, health services and manufacturing, Dr Mannetje said.
Wellington Hospital oncologist David Hamilton said the cancer he saw most frequently in patients was caused by the sun.
Non-melanoma skin cancers were so common that incidences were not even recorded in the national database.
"It tends to get a low profile because it isn't considered as dangerous as lung cancer or bowel cancer, but I see many people dying of skin cancer.
"People whose scalps and arms are just covered in cancers can have a pretty horrible time, even if it doesn't kill them."
Asbestos was also a problem and, like skin cancer, might not show up until 20 to 30 years after exposure, he said.
Cancer Society health promotion adviser Barbara Hegan said that between 237 and 425 Kiwis died each year from occupational cancer, a number on a par with the road toll.
The forum was an attempt to highlight the importance of workplace safety, which had been neglected until the events of Pike River, she said.
Government health and safety department Worksafe New Zealand, an offshoot of the Ministry of Business, Innovation and Employment, will be launched next month.
- The Dominion Post
How soon will you visit the new war memorial park?Related story: War memorial park all but completed