A study of over 6600 meat industry workers around New Zealand has found a significantly high rate of cancers, particularly lung cancer, which may be caused by exposure to cancer causing agents carried by animals.
The study, by Dr Dave McLean, Centre for Public Health Research, followed the health status of 6647 people who work or have worked in the meat processing industry from three plants, in the North and South Islands. International research indicates there is an increased risk of cancers of the lung and larynx, and of leukaemia and lymphoma, among butchers and slaughterhouse workers. The aim of this project was to see whether the same was true for New Zealand and to identify the exposures associated with any increased risks.
Dr McLean says the study found that the rate of lung cancer in the group was signficantly higher than in the general population. He says while it is possible that smoking and the ethnicity of the workers had an impact on these findings, it is highly unlikely that either factor is sufficient to account for more than a small part of the excess observed.
“ There are two key findings that are of considerable interest. The first is that there is an excess of lung cancer, for which there is a strong dose-response relationship based on how long people had worked in certain jobs. Lung cancer was most strongly associated with exposures to biological material in animal urine, faeces or blood – we don’t know what the cause is but one possibility is that they are exposed to a biological element, caused by something like a bacteria, virus or fungi, which is carried by the animals.
“ The second finding is that despite small numbers there is evidence of an association of cancers of the lymphohaematopoietic system with how long people had worked in meat processing and plant services. This was particularly associated with exposure to animal faeces. This effect appears to exist for non-Hodgkin’s lymphoma, and possibly also for leukaemia.”
Dr McLean says that while there has been very little research into the types of exposures that occur in the meat industry, potentially hazardous exposures are primarily biological, including bacterial and viral infectious agents as well as non-infectious bioaerosols. There is also a limited range of potential exposures from chemicals either used in the process or in the maintenance of plant and equipment, or encountered as residues of animal remedies or pesticides used on farms.
Dr McLean emphasises that there is no evidence to implicate the meat processed in the plants, or indicate any risk to consumers
“Evidence would appear to suggest that the risk is associated somehow with the handling of live animals and the slaughter process itself, and the high exposures to that proces, and that it disappears completely in those jobs that involve the further handling of meat, such as the meat cutters or retail butchers. But further research is required before we could positively identify the causes.”
He says the findings could have significance for public health policy making because of the number of people employed in the meat processing industry in New Zealand. However, further research is required to identify the specific agents responsible, so preventive measures can be developed.
The study found that mortality from all causes was higher than expected based on the general population (227 deaths compared with 204 expected), and from all cancers (69 deaths compared with 61 expected). Among the cancers, significant excess mortality was observed for lung cancer (23 deaths compared with 13 expected).
Of the 6647 people studied the majority had been employed on the slaughter board (44 percent) or in meat cutting (28 percent), with a further 10 percent employed in departments associated with the processing of edible and inedible offal and meat wastes.
Dr McLean worked with Soo Cheng and Professor Neil Pearce, from the Public Health Research Centre, Andrea ‘t Mannetje, from the International Agency for Research on Cancer (a branch of WHO) and Alistair Woodward, Wellington School of Medicine, on the project which was funded by the Health Research Council.