R. Thomas Zoeller, chair of the biology department at the University of Massachussetts, called it "a very important paper."
"It is telling us that the pesticides most prevalent in the human population have effects on the androgen receptor," said Zoeller, who directs the university's Laboratory of Molecular, Cellular and Developmental Endocrinology.
"Considering all the evidence that human male reproduction is exhibiting troubling secular trends (sperm count and quality, hypospadias, cryptorchidism, testis cancer), this is highly troubling," he said.
Funded by the European Commission, the University of London scientists selected the pesticides to test by identifying those found most often in European fruits and vegetables. They are approved for use in many countries, including the United States.
The researchers noted “a clear disparity” between today's most widely used pesticides and the current knowledge of their risks, “with the majority of the published literature focused on pesticides that are no longer registered for use in developed countries.”
Of the tested compounds, the most potent in terms of blocking androgens was the insecticide fenitrothion, an organophosphate insecticide used on orchard fruits, grains, rice, vegetables and other crops.
Others with hormonal activity include fludioxonil, fenhexamid, dimethomorph and imazalil, which are all fungicides. Fungicides are often applied close to harvest, so they are frequently found as residue in food. Some are new compounds which have been used for only a few years.
Fungicides “are typically applied as mixtures in order to increase effectiveness and prevent development of resistant strains and therefore, human exposure to mixtures of these in vitro anti-androgens may be considerable,” wrote Kortenkamp and the other study authors, Frances Orton, Erika Rosivatz and Martin Scholze.
For six of the pesticides that showed hormonal activity for the first time, the authors said they “strongly recommend” the next round of testing, using lab animals. “Due to estimated anti-androgenic potency, current use, estimated exposure, and lack of previous data, we strongly recommend that dimethomorph, fludioxonil, fenhexamid, imazalil, ortho-phenylphenol and pirimiphos-methyl be tested for anti-androgenic effects in vivo.”
For the first four pesticides, they called it “a matter of urgency.” They are used on strawberries, lettuce, grapes and other fruits and vegetables.
Mary Emma Young of CropLife America, which represents the pesticide industry, said the group is reviewing the new study and could not yet comment on it. She added that "we continue to work with EPA and others to understand the potential for a chemical to interact with the endocrine system as well as the potential consequences of that interaction on human health and the environment."
In 2009, the EPA ordered industry to use the in-vitro assays to screen 67 pesticides for their potential effect on hormones. The deadline is this October – 15 years after Congress granted the agency the authority to screen for such effects – but an extension is likely.
Last November, the EPA added another 134 pesticides and industrial chemicals found in water supplies. The testing is the first step toward including hormone data in the regulation of pesticides and industrial chemicals.
Pesticide companies, in a January letter to the EPA, asked the agency to refrain from listing more chemicals for testing "until the agency has had an opportunity to evaluate the performance" of the techniques used to test the initial 67 pesticides.