The insecticide – an organochlorine marketed under the name Kepone – caused such widespread environmental damage the US maker stopped production in 1976 and the World Health Organisation later banned it.
Researchers have now found evidence its widespread use to control a banana plant pest in the French West Indies for 30 years significantly raised the incidence of prostate cancer among men there.
A suggestion the chemical (first produced in 1958) might be dangerous came in 1964 when two New Zealand agricultural scientists, H.V. Brewerton and D.A. Slade, published the first findings about Kepone’s ability to remain in edible plants.
They analysed Nelson-produced apples that had been sprayed for leaf roller as many as 13 times during growth. The apples showed heavy residues of spray on skin and in the pulp.
At present, no tolerance has been established for “Kepone”, and owing to the evident high persistence of the chemical, its use cannot at present be suggested even in the early season.
However, a 1.5 parts per million tolerance would enable “Kepone” to be used on Sturmer apples up to the end of December, and under New Zealand conditions this would make a worthwhile contribution to the control of leaf roller.
In 1975, workers at the factory making the insecticide in the US were found to be suffering a mystery illness and their town was found to be heavily contaminated.
Later research in the 70s and early 80s found the chemical in Kepone, chlordecone, caused illnesses, including cancer, and infertility.
French scientists recently published their findings in the Journal of Clinical Oncology, after testing the blood of 623 French West Indian men who suffered prostate cancer and comparing them with a random sample of 671 males:
We found a significant increase in the risk of prostate cancer with increasing plasma (blood) chlordecone concentration…
…Stronger associations were observed among those with a positive family history of prostate cancer and among those who had lived in a Western country.
…Also, a significantly higher risk existed for patients older than 60 years compared to younger than 60 years.
…These findings support the hypothesis that exposure to environmental estrogens increases the risk of prostate cancer.
Chlordecone was used between 1973 and 1993 in the French West Indies as an insecticide in banana plants.
It caused widespread contamination of soil, water, animals and vegetables.
Chlordecone does not undergo significant degradation, so polluted sources continue to contaminate foodstuffs which remain the primary means of human exposure to this chemical.
Chlordecone is a known carcinogen in laboratory models and its hormonal properties and long half-life increase the possibility of acting as a carcinogen.