Epidemiologic studies of cancer in agricultural workers

Abstract

The incidence of cancer in agricultural workers is generally low, in part due to the low prevalence of cigarette smoking in this group. However, agricultural workers have elevated risks for several specific cancer types including leukemia, Hodgkin's disease, non-Hodgkin's lymphoma, multiple myeloma, and cancers of the lip, stomach, prostate, brain, and connective tissue. Two major groups of risk factors have been proposed as causes of hematologic malignancies in agricultural workers. The first group includes various agricultural chemicals. In particular, several studies have found increased risks of malignant lymphoma and soft tissue sarcoma in persons exposed to phenoxy herbicides. However, the evidence is inconsistent and there is a wide variation in relative risk estimates. The second group of risk factors includes various animal viruses. There is currently little evidence concerning the zoonotic nature or human carcinogenicity of these viruses. However, leads have been suggested by recent evidence of increased risks of hematologic malignancies in abattoir workers, veterinarians, and meat inspectors. A third hypothesis, for which little evidence is currently available, is that agricultural work may involve prolonged antigenic stimulus leading to lymphoproliferation. The factors responsible for the increased risks for cancers other than hematologic malignancies are not well understood but may also involve exposure to chemicals or viruses.

Distribution of different occupations in multiple myeloma patients- a hospital based study at a tertiary care hospital, Guwahati, Assam, India

“…Pearce NE demonstrated the risk of the occurrence of myeloma in patients who used pesticides. 11 Thus, although present study results are statistically insignificant, yet it is comparable with the study. Moreover, it appeared that both fruit seller and pesticide sellers had given the history of selling these for more than 10 years.…”

The Agricultural Health Study.

“…The special recruitment effort will draw respondents from several eastern North Carolina counties, the historic locus of African-American farming in North Carolina. Approximately 1,800 minority subjects will be enrolled through the normal recruitment process and 1,400 more will result from the supplemental minority recruitment effort in North Carolina for a total of 3 illiteracy. This has not been a significant problem for enrollment.…”

“…Farmers and farm workers have long been recognized as being at high risk of injury, nonmalignant respiratory disease (e.g., farmers' lung), and some types of dermatitis (e.g., cattle ringworm, chemical burns, and irritant dermatitis) (1). On the other hand, studies from North America, Europe, Australia, and New Zealand have established that farmers have a lower overall mortality rate, a lower heart disease mortality rate, and lower mortality rates for cancers of the lung, esophagus, bladder, and colon than the general population (2)(3)(4)(5). Low mortality rates from these cancers and for heart disease have been attributed to lower smoking rates among farmers (2,(6)(7)(8)(9), with possible additional contributions from diet and a physically active lifestyle (2).…”

“…Despite an excellent overall mortality experience, farmers in many countries appear to have higher rates than the general population for Hodgkin's disease, leukemia, multiple myeloma, nonHodgkin's lymphoma, and cancers of the lip, stomach, prostate, skin (melanotic, nonmelanotic), brain, and connective tissue (2)(3)(4)(5). While each cancer is not elevated in every study of agricultural workers, the tendency toward excess is intriguing given the diversity in agricultural practices within and between countries.…”

“…Agricultural workers and their families may have exposure to pesticides, animal viruses, mycotoxins, dust, fuels, oils, engine exhaust, and fertilizers. Cancer patterns in related agricultural groups, including flour millers (15), agricultural extension agents (16), soil and forest conservationists (17), commercial pesticide appliers (18), slaughterhouse workers (3), and veterinarians (3,5), also suggest that agricultural exposures deserve attention. To date, however, the strongest links of exposures and malignancies have been with pesticides (4,19).…”