Cancer risks and immunological effects in agriculture

Sammanfattning: In general, farmers and agricultural workers are characterized by relatively low mortality rates when considering all causes of death and deaths due to all types of cancer. However, several studies have shown that this occupational category tend to be at increased risks of developing the following forms of malignancies: leukaemia, lymphomas, multiple myeloma, and cancers of the skin, lip, prostate, stomach, brain, and connective tissue. Although the reported excesses have not been consistent in different studies, they nevertheless suggest that agricultural exposures, especially pesticides, contribute to cancer aetiology through different mechanisms of action. It has been hypothesised that immunotoxic effects may play a role, since most of the malignancies found to be increased in workers employed in agriculture are also elevated in patients suffering from innnunodeficiencies. The present studies were conducted to ascertain whether agricultural activities and exposures influence the risk of developing cancer, and to evaluate the innnunological effects of phenoxy herbicides as possibly important for the aetiology of lymphomas.Different types of cancer were considered in relation to farming in two case-control studies, focused one on men and the other on women. A decreased risk of postmenopausal breast cancer (odds ratio [OR] 0.4) and an excess of skin melanoma (OR 2.7) and bladder cancer (OR 2.7) were observed in the women. The main finding in the men was an excess of prostate cancer (OR 1.5). Further analyses showed that this malignancy was associated with exposure to chlorinated compounds (OR 2.5), and, more specifically, to DDT (OR 2.1) and dicofol and tetradifon (OR 2.8).Mortality in selected groups of farmers and their relatives was investigated in two cohort studies. Farmers and their wives showed reduced mortality from all causes and all cancers although there was a tendency towards increased risk of leukaemia, particularly among wives of pesticide users (standardised mortality ratio [SMR] 2.4). Adult sons and daughters of green-house owners exhibited increased mortality from all types of cancer (SMR 1.9).A study was also performed to compare pre- and post-exposure values of selected immunological parameters in a group of ten farmers exposed to phenoxy herbicides. The most notable fmdings were reduced levels of the following: circulating natural killer (NK) cells (-38%), NK cytotoxic activity (-53%), and lymphocyte response to mitogenic stimulation (-50%).