From 1973 to 1993 the estrogenic insecticide chlordecone (marketed as Kepone) was widely used in the French West Indies to control pests in the banana crop. Chlordecone does not degrade in the environment, and it is known to persist in water and in the soil. Humans are most commonly exposed to chlordecone through their food. This insecticide has been classified as a likely carcinogen by the U.S. Environmental Protection Agency. It has been shown to cause hepatic tumors in rats and mice, and may act as a tumor promoter through hormone-mediated effects. Its use has now been banned in many countries, including the USA (since 1975) and the French West Indies (since 1993).
Multigner et al. wanted to investigate whether the presence of environmental estrogens is associated with an increased risk of prostate cancer. Because chlordecone was used extensively in the French West Indies, contaminating the population for more than 30 years, they decided to analyze the relationship between exposure to chlordecone and the risk of prostate cancer among men on the island of Guadeloupe.
The authors investigated data from 623 men with prostate cancer and 671 controls. Exposure to chlordecone was assessed according to case-control status, using either current plasma concentration or a cumulative exposure index based on years of exposure. They also carried out genetic studies designed to identify the presence of one or both of two single-nucleotide polymorphisms or SNPs in the gene that codes for and enzyme called chlordecone reductase. These two SNPs are known as rs3829125 and rs17134592.
Multigner and his colleagues were able to show the following:
- There was a significant increase in the risk of prostate cancer in men with a higher plasma chlordecone concentration (odds ratio [OR] = 1.77) and/or a higher cumulative exposure index (OR = 1.73).
- Stronger associations were observed among Guadeloupean men with a positive family history of prostate cancer and among those who had lived in a Western country.
- The rs3829125 and rs17134592 allele variants were only found at a very low frequency (0.04 percent); their presence resulted in low production of the enzyme and reduced clearance of the insecticide from the circulation.
- Among subjects with plasma chlordecone concentrations above the limit of detection or LD, carriers of the allele variants had a much higher risk of prostate cancer (OR = 5.23), but this risk was not statistically significant.
The authors conclude that their findings “support the hypothesis that exposure to environmental estrogens increases the risk of prostate cancer.”
Additional details about this study are also available in an article on the MedPage Today web site.