KEY POINTS:
Nurses have a higher risk of dying from leukaemia and teachers from breast cancer, a study has found.
By analysing more than 7200 cancer deaths among women between 1988 and 1997, researchers at Otago University's Dunedin School of Medicine have established links between certain occupations and specific cancers.
The study is the first analysis of cancer deaths by occupation among New Zealand women, with findings that are in line with other overseas studies. The findings appear in the latest New Zealand Medical Journal.
One of the researchers, associate professor of cancer epidemiology Brian Cox, said some cancers have well-known occupational associations, such as exposure to asbestos, but in others, the link was not as clear.
Professor Cox said one of the main findings was the elevated risk of health workers dying from leukaemia.
"For women, nurses are by far the biggest group of health professionals and the figure for nurses suggested that they had a 42 per cent greater chance of developing leukaemia than other female workers."
Health workers in general had a 52 per cent increase in death rates from leukaemia compared with other workers. Professor Cox said the reasons were unclear.
"There are proposals as to why that might be. Some branches of nursing involve handling fairly toxic drugs, such as anti-cancer drugs. Another theory about the cause of leukaemia is that it's associated with some rare complication of common infectious disease - nurses again would be in the frontline to be quite heavily exposed to infectious agents from patients that they're looking after ... Or it could be something else entirely."
Teachers had about a 30 per cent increased risk of breast cancer. But Professor Cox said the scope of study could not take into account other factors known to be important in cancer. "We weren't in a position to make allowance for reproductive factors, which are known to be related to one's risk of breast cancer.
"So it could be for example that teachers were less likely to have had children, which slightly increases one's risk of breast cancer, or had children later in life rather than earlier, which also tends to increase one's risk."
He said it was an "overall description" of cancer risk.
"Sometimes these risks are due to inherent characteristics of the individuals, but sometimes they're due to the feature of the workplace or the work processes."
But, he said, studies of this nature were increasingly difficult as the past decade has seen the recording of occupational data become more "haphazard".
"The issue really is to explore why some of these particular occupational groups seem to have a higher chance of death from these particular cancers."
* JOBS AND CANCER
Occupational risk in cancer deaths:
Clerical workers: Increased risk of non-Hodgkin's lymphoma, and cancers of the breast, bladder, uterus, brain and rectum.
Health professionals: Increased risk of leukaemia and colon cancer.
Teachers: Increased risk of multiple myeloma and cancers of the breast, uterus and colon. Decreased risk of lung cancer.
Farmers: Increased risk of cancer of the peritoneum (the membrane that lines the abdominal and pelvic cavities).
Cleaners: Increased risk of cervical and ovarian cancers. Reduced risk of breast cancer.
Textile workers: Increased risk of stomach cancers.
Restaurant workers: Increased risk of thyroid cancer.
