Little is known about the occurrence of cancer in migrant workers. Yet, they are exposed to potentially carcinogenic pesticides and other chemicals in their work place (1). Adults and children may be exposed to pesticides during planting, weeding, thinning, and harvesting crops. Migrants who work in other industries such as construction, canning factories, and meat processing may be exposed to other types of chemicals used in the production process. Working conditions in fields and factories provide little or no opportunity to take appropriate steps for exposure prevention, such as washing skin or clothing to minimize pesticide absorption or using protective gear while working with potentially toxic substances.
In spite of the toxicological evidence of a connection between certain chemical substances and breast cancer, minimal data has been collected regarding human subjects. Occupational studies show associations between breast cancer and exposure to certain organic solvents and polycyclic aromatic hydrocarbons (PAHs). In 1999, Petralia et al. assessed women’s exposure to benzene and PAHs, using lifetime job histories and exposures adjusted for breast cancer risk factors. The findings revealed a two–fold increased risk for women ever exposed to benzene and PAHs, and a higher risk for women who were exposed for over four years. The study evaluated bus and truck drivers, mechanics, garage and service station employees, painters, laboratory technologists and sculptors (2).
A case–control study of 995 incident breast cancer cases in British Columbia, Canada reported elevated risk among women who had job titles associated with exposure to solvents and pesticides (3). Other studies have reported no effect of chemical exposures on breast cancer. These results may be complicated by the healthy worker effect Workers who develop work related diseases are often forced to leave their jobs, leaving only workers who are healthy. The Carolina Breast Cancer Study found a lower risk in women who worked on a farm (probably due to increased physical activity), but a higher risk for those not wearing protective gear when using pesticides (4).
In general, occupational studies support the association, independent of socioeconomic status, between increased cancer risk and exposure to benzene, organic solvents and PAHs. However, studies in this area face several potential confounds, such as exposure to many chemicals at a time, failure to identify protective factors (like increased physical activity), self report bias when inquiring about exposures, and the long latency of cancer development. More research with innovative techniques is needed to better understand the relationship between cancer and occupational exposures.
A New Study Summary Pesticide Exposures & Farm Worker Tasks published in February 2004 by Researchers at the Fred Hutchinson Cancer Research Center and the University of Washington compared farm workers and their families based on the kind of work tasks they did. The study evaluated data on the organophosphate pesticide Guthion (azinopos–methyl) in the dust of 156 homes and 190 vehicles and Guthion breakdown products (dimethyl metabolites) in urine samples from adults and children in 211 households (5).
They found that:
- Thinners (workers who remove small buds from tree limbs to increase fruit size) had a greater likelihood of having Guthion detected in their homes and vehicles than those who didn’t thin (5).
- A greater number of children of thinners had dimethyl metabolites in their urine than did the children of non–thinners. (Thinners themselves did not have more metabolites than non–thinners. This could be associated with the longer half–life of pesticides in the home environment, greater opportunity for children to be exposed in this environment, or a lessened ability of children’s bodies to break down pesticides.) (5)
- A slightly lower number of house and vehicle dust samples for mixers, loaders and applicators had Guthion in them as compared to field workers. Although the difference was not statistically significant, the finding contradicted expectation (5).
- A very high percentage of workers in every job had dimethyl metabolites in their urine. For example, 93.3% of harvesters had DMTP. Dispite access to personal protective equipment and other protections, 90.0% of the pesticide mixers and loaders and 95.6% of the sprayers had detectable levels of dimethyl metabolites (5).
According to the latest review of the American Cancer Society (ACS), Cancer Facts & Figures for Hispanics/Latinos 2006–2008, mortality and selected cancer–related behaviors of Hispanic–Americans, Hispanics have a lower rate of incidence of the major cancer killers (breast, prostate, lung and bronchus, and colon and rectum). However, they have a higher incidence of and mortality from cancers that are related to infectious agents (stomach, liver, uterine cervix, and gallbladder), lower rates of screening for cervical cancer, and the least access to medical care (6).
According to the United States Census, in the year 2004 there were 42 million Hispanic or Latino* living in the United States, representing 14% of the total population. About 39,940 new cancer cases in men and 42,140 cases in women are expected to be diagnosed among Hispanics in 2006 (6). The most commonly diagnosed cancers among Hispanic men are: prostate (30%), colon and rectum (11%), and lung and bronchus (8%) Non–Hodgkin lymphoma (5%), Kidney & renal pelvis (5%). Among Hispanic women they are: breast (34%), colon and rectum (9%), and lung and bronchus (6%), uterine corpus (5%), uterine cervix (5%), thyroid (5%) (6).
Breast cancer is the leading cause of death among Hispanic women. Every year the ACS estimates the number of new cancer cases and deaths expected in the United States, for 2006 they projected 14,300 new breast cancer cases and an estimated 1740 deaths. Compared with non–Hispanics, Hispanic women had an overall lower incidence of breast cancer during 1994 – 2003, however the cancer was diagnosed at a later stage and therefore harder to treat making increased access to early detection of utmost importance. For example, during the period 2000–2003, 54% of breast cancers among Hispanic women were diagnosed at a local stage, compared to 63% of cases among non–Hispanic white woman. Differences in mammography utilization and delayed follow up of abnormal screening results may contribute to this difference. Hispanic woman are 20% more likely to die of breast cancer than non–Hispanic white women diagnosed at similar age and stage (6).
Colorectal cancer is the second leading cause of cancer in both Hispanic men and women. An estimated 8,000 patients were expected to be diagnosed with colorectal cancer in 2006. The stage of the cancer at diagnosis is later compared with other groups, factors that may contribute to survival disparities include lower use of colorectal cancer screening tests and less access to timely and high–quality treatment. Since 1994 mortality from colorectal cancer has declined in Hispanic men but remained unchanged in Hispanic women (6).
Prostate cancer is the most commonly diagnosed cancer among Hispanic men. ACS estimated 11,830 Hispanic men are expected to be diagnosed with prostate cancer in 2006. Although prostate cancer rates during 2000–2003 for Hispanics were approximately 20% lower than the rate among non–Hispanic whites, prostate incident rates changed very little in both Hispanic men and non–Hispanic white men from 1994 through 2003. An estimated 1,140 death from prostate cancer are expected in 2006 among Hispanic men in 2006, making prostate cancer the third leading cause of cancer death. From 1994–2003, the death rate per year dropped in both Hispanic (3.2%) and non–Hispanic white men (4.1%)(6).
About 90% of the 5–year relative survival rate for patients diagnosed at a localized or regional stage approached 100%, survival rate for distant stage is 33%. Even though there was a drop in the death rate for men diagnosed with prostate cancer more Hispanic men are likely to die than white men after being diagnosed with the disease, this may reflect a lower likelihood of timely, high–quality treatment and inadequate monitoring during the “watchful waiting” period (6).
*The term “Hispanic” and “Latino” refer to the same ethnic group.
- Brody JG, Rudel RA. Environmental pollutants and breast cancer, Environ Health Perspect 2003;111:1007–1019
- Petralia SA, et al. Risk of premenopasualmenopausal breast cancer in association with occupational exposure to PAH and benzene, Scand J Work Environ Health 1999; 25:215–221
- Band PR et al. Identification of occupation cancer risks in British Columbia: a population based case–control study of 995 incident breast cancer cases by menopausal status, controlling for confounding factors. J Occup Eviron Med 2000; 42:284–310
- Duell EJ et al. A population based case–control study of farming and breast cancer in North Carolina, Epidemiology 2000; 11:523–531
- http://ehpnet1.niehs.nih.gov/members/2003/6412/6412.pdf See Coronado, “Agricultural Task and Exposure to Organophosphate Pesticides Among Farmworkers”, Environmental Health Perspectives 112(2), 142–147 (Feb 2004)
- Cancer Fact & Figures for Hispanics/Latinos 2006–2008, American Cancer Society