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IARC assessed the carcinogenicity of five organophosphate pesticides

The International Agency for Research on Cancer (IARC), the specialised cancer agency of the World Health Organization (WHO), has assessed the carcinogenicity of five organophosphate pesticides: glyphosate, malathion, diazinon, tetrachlorvinphos and parathion and published their findings (Volume 112 of the IARC Monographs).

The herbicide glyphosate and the insecticides malathion and diazinon were classified as probably carcinogenic to humans (Group 2A). The insecticides tetrachlorvinphos and parathion were classified as possibly carcinogenic to humans (Group 2B).

Agrochemical industry representatives have roundly condemned a decision by the IARC. The industry body, CropLife International, says that the IARC classification system is “not aligned with current international regulations” and the decisions create “needless public concern”. The conclusions are a result of an “incomplete data review where key evidence has been omitted”. They contradict those of the world’s most robust regulatory systems in the EU and the US where crop protection products have undergone extensive reviews based on multi-year testing and active ingredients such as glyphosate and malathion have been found not to present a carcinogenic risk to humans, CropLife points out.

A summary of the IACR’s findings has been published online in the journal, The Lancet Oncology, with detailed assessments will be published as Volume 112 of the IACR Monographs. The findings were issued after a working group of 17 experts from 11 countries met at the IACR on March 3rd-10th after a nearly year-long review of “the latest available scientific evidence”. The working group considered reports that have been published or accepted for publication in openly available scientific literature and data from government reports that are publicly available.

The IACR conclusion that tetrachlorvinphos and parathion are possibly carcinogenic to humans was based on “convincing evidence that these agents cause cancer in laboratory animals“. For malathion, there is “limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma and prostate cancer“.  The evidence comes from exposure studies, mostly agricultural, in the US, Canada and Sweden published since 2001. Malathion also caused tumors in rodent studies and caused DNA and chromosomal damage and disrupted hormone pathways, the IACR notes. For diazinon, there was “limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma and lung cancer“. The evidence in humans is from studies of agricultural exposure in the US and Canada published since 2001. The classification is also based on “strong evidence” that diazinon induced DNA or chromosomal damage.

For glyphosate, there is “limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma“. The evidence in humans is from studies of exposure, mostly agricultural, in the US, Canada and Sweden published since 2001. There is also “convincing evidence that glyphosate can cause cancer in laboratory animals”. On the basis of tumors in mice, the US EPA originally classified glyphosate as a possibly carcinogenic to humans in 1985. After a re-evaluation of that study, the EPA changed its conclusion to “evidence of non-carcinogenicity in humans” in 1991. The EPA Scientific Advisory Panel noted that the re-evaluated results were still significant using two statistical tests recommended by the IARC. The IARC working group considered the significant findings from the EPA and several more recent positive results in concluding that there is “sufficient evidence of carcinogenicity in experimental animals“. Glyphosate also caused DNA and chromosomal damage in human cells, although it gave negative results in tests using bacteria, the IARC notes.

Glyphosate is undergoing re-evaluation in the EU and is among the second group of a.i.s to go through the EU approval renewal programme. Germany is the rapporteur member state. The country gave the all clear to the re-approval in January 2014 when it submitted its draft re-assessment report on health risks from the a.i to the European Food Safety Authority.

You can read a summary of the IACR’s findings at:

For more information on the regulation of plant protection products and how this may impact on your business, contact JSC on +44 (0)1423 520245,

Published 30th March 2015
Categories Agrochemicals, News
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