Working night shifts long term is expected to become a basis for compensation claims to ACC now that it has been established internationally as a probable cause of cancer.
The Government of Denmark has become the first to recognise the link between night shifts and cancer, paying compensation to 40 women who developed the disease after working night shifts in state sector jobs. But it rejected claims from those who had a family history of breast cancer.
Its move came after a United Nations health body concluded that working nights probably increased the risk of cancer.
The International Agency for Research on Cancer (IARC), which looked at studies of nurses, flight attendants and animals, placed shift work in the same category as ultraviolet radiation, anabolic steroids and diesel engine exhausts in terms of cancer risk.
One report on which the IARC based its findings showed a 36 per cent greater risk of breast cancer for women who had worked night shifts for more than 30 years, compared with women who had never worked nights.
Cancer researcher Professor Neil Pearce, of Massey University, said the link was well proven in animal studies and there was "some evidence in humans". A 36 per cent increased risk was "not huge" but breast cancer was the most common cancer in women, "so it's not a trivial risk".
The IARC report came out only in October 2007, so its implications were still being worked out internationally.
As with all occupational cancers, the aim should be to prevent breast cancer being caused by work hazards, Professor Pearce said.
"We are not doing a very good job with the ones that are absolutely conclusively proven, let alone with new ones like this where the evidence is not quite so conclusive.
"Certainly this is something that would be added to the list of known or probable causes of occupational cancer and just like the others on the list I expect someone might eventually make an ACC claim."
A Massey survey found that among workers, 4 per cent of women and 10 per cent of men had worked a night shift - at least three hours between midnight and 5am - in the preceding four weeks.
An ACC spokesman said last night he was not aware of any claims regarding breast cancer linked to night work.
"Each case is determined on its own merits. We would take into account any credible research that existed on the issue and also the individual circumstances of the person making the claim ... we would normally seek expert advice from scientists and specialists, for example toxicologists."
- ADDITIONAL REPORTING: INDEPENDENT