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Advisory Committee on Pesticides Statement on the Pesticides Literature Review published by the Ontario College of Family Physicians

In April 2004, the Ontario College of Family Physicians published a systematic review of the epidemiological literature on possible chronic health effects of pesticides.  The review, which focused on papers published during 1992-2003, concluded that “it can be clearly stated that at least some pesticides are carcinogens” and recommended that pesticide use should be reduced. 

The Advisory Committee on Pesticides (ACP) considered the report at its meeting in May 2004  when the epidemiologist on the Committee (the Chairman) presented his assessment of the review.  He proposed that, in case his views were unrepresentative of wider scientific thinking, opinions should be sought also from a number of other independent epidemiologists.  Accordingly, comments were requested from five epidemiological experts who were current or recent members of other Government advisory committees (the Committee on Toxicity, Committee on Carcinogenicity and Advisory Group on Non-Ionising Radiation).  To avoid prejudicing their evaluations, they were not shown the Chairman’s assessment of the review.

The ACP reconsidered the Ontario report at its September 2004 meeting, along with the feedback from the invited experts.  This statement summarises the conclusions of ACP’s discussions to date.

For some years, the ACP Medical and Toxicology Panel has annually scrutinised the abstracts of published papers on pesticides and human health to check for findings that might have implications for pesticide regulation in the UK.  The material covered by the Ontario review overlaps substantially with that which has already been examined by the Panel, but with some differences (the review covers a somewhat longer time period and includes a few papers written in languages other than English, but is restricted to 16 specified health outcomes).

Some of the conclusions of the report accord with those reached by the Medical and Toxicology Panel.  Thus, the Panel has previously noted an apparent consistency of epidemiological reports linking Parkinson’s disease with pesticide exposure, and this led to the commissioning of a detailed review of the topic.  (See Sept 2001 minutes.)  Similarly, we have recently asked the Committee on Mutagenicity to review the literature on biomarkers of genotoxicity in pesticide-exposed workers, in which the frequent report of positive findings seems at odds with the absence of in vivo genotoxicity for almost all pesticides when tested individually for regulatory purposes.  Other conclusions differ markedly from those of the Panel.  For example, the report concludes that “large well-designed cohort studies consistently show statistically significant positive associations” between solid tumours and pesticide exposure, an assertion with which we strongly disagree.

These discrepancies arise from serious flaws in the methods employed in the review.  Most important are:

• its failure to take account of all or even most of the relevant epidemiological evidence, and the biases inherent in the way in which material was picked out for inclusion;
• inadequate attention to exposure characteristics and relevant toxicology when interpreting reported associations; and
• its superficial synthesis of evidence, which inadequately explores the impact of the strengths and weaknesses of individual studies.

Overall, the ACP has concluded that the report does not raise any new concerns about pesticide safety that were not already being addressed, and does not indicate any need for additional regulatory action in the UK.

Advisory Committee on Pesticides:  Supplement to Previous Statement on the Pesticides Literature Review Published by the Ontario College of Family Physicians

At its meeting on 13 January 2005, the ACP agreed the following supplement to its earlier statement on the pesticides literature review published by the Ontario College of Family Physicians.

Supplementary statement
The above comments on the Ontario review and its implications for risk assessment and regulation of pesticides in the UK in no way detract from the unanimous view of the ACP that unnecessary exposure to pesticides should always be avoided.  Pesticides should be used only when the use is justified by potential benefits in pest control and better alternative methods of pest control are unavailable.  Moreover, when pesticides are used, they should always be applied in accordance with the instructions on the label, and in a way that minimises people's exposure as far as is reasonably practical.