Environmental Risk Factors for Prostate Cancer in Overburdened, Understudied Populations
National Institute on Minority Health and Health Disparities (NIMHD)
Leading scientific research to improve minority health and reduce health disparities.
Authored by Lauren Hurwitz , Ph.D., MHS
Prostate cancer is the second most frequently diagnosed cancer among men globally, and the leading cause of cancer death among men in 48 countries, most of which are in Africa, the Caribbean, and South America (1). In the United States, prostate cancer is also the cancer with the largest disparities by race, with incidence rates 60-70% higher and mortality rates 100-120% higher in Black men as compared to non-Hispanic White men (2). The underlying drivers of prostate cancer racial disparities are not well understood but likely involve a complex interplay of genetic, social, structural, and environmental factors (2).
As a Postdoctoral Fellow at the National Cancer Institute (NCI), I am part of group studying environmental and occupational risk factors for prostate cancer, including how they may be inequitably distributed and contributing to these disparities. Using studies of highly exposed occupational groups in the U.S., we have been investigating pesticide exposure and its potential impact on prostate cancer risk among farmers. Evidence from the Agricultural Health Study, a large prospective cohort study, suggests that specific pesticides (certain organophosphate and organochlorine insecticides) are associated with risk of more aggressive forms of prostate cancer (3, 4). Similar associations have been observed in case-control studies as well (5). While informative, the prior studies have one major limitation—most studies of pesticides and prostate cancer risk have been conducted in non-Hispanic White populations.
These prior studies indicate that exposure to specific pesticides may increase prostate cancer risk among White men. However, we do not know if these same pesticides also increase risk of prostate cancer among Black men from the U.S., or men from the Caribbean and sub-Saharan Africa, where both exposure to pesticides and prostate cancer incidence and mortality rates are particularly high. Men from different racial and ethnic groups may be exposed to different types or levels of pesticides due to different historical patterns of pesticide use within and across countries, and due to interacting social and structural factors. This was highlighted in the news recently (6)?in studies from the French islands of Martinique and Guadeloupe—islands with primarily African-descent populations, and some of the highest prostate cancer incidence rates in the world. These studies found a link between prostate cancer risk and chlordecone and the dichlorodiphenyltrichloroethane (DDT) metabolite DDE, organochlorine insecticides that were widely used on these islands (7,8), underscoring the need to investigate pesticides and cancer risk across geographically and racially diverse populations.
Sub-Saharan Africa is another region of the world with heavy use of pesticides and a high burden of prostate cancer, yet no epidemiologic studies to date have investigated pesticides and prostate cancer risk among African men (9). Exposure to organochlorine insecticides, and specifically DDT and its metabolites, may be particularly high in sub-Saharan Africa; though most countries have now banned the use of DDT for agricultural purposes, many countries in this region still use DDT to combat mosquitos that spread malaria. Like other organochlorine insecticides, DDT is extremely persistent and known to have detrimental effects on the environment, but the human health effects of exposure are not fully understood.
To address this gap, our group initiated a study to measure blood levels of organochlorine insecticides among men with and without prostate cancer from the Greater Accra Region of Ghana. This work is still ongoing, but our pilot results indicate that exposure to DDT in this population is ubiquitous; all samples in the pilot had detectable levels of p,p’- DDE, the primary DDT metabolite, and levels were much higher than those of men from the U.S. Overall, we hope this work will further our understanding of the relationship between pesticide exposures and prostate cancer risk, while shedding light on environmental risk factors that may disproportionately affect overburdened yet understudied populations.
This article was originally published in NIMHD Insights.
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