DR. IAN SIMPSON
The Western Star
My letter last week about cosmetic use of pesticides has promoted some discussion both in The Western Star printed edition and its web edition.
I would like to reply to Tuesday’s letter from Lorne Hepworth of CropLife Canada.
He states “we can rest assured that before any pesticide is sold in Canada it undergoes comprehensive scientific review and risk assessment by Health Canada.”
Health Canada has created PMRA — the Pesticide Management and Regulatory Agency — which is the responsible body for reviewing all the studies submitted. But there are problems:
- Underfunding — in 2002, $8 million of the funding was from the pesticide industry.
- PMRA does not conduct its own in-house laboratory work. It reviews the research provided — most of it from industry sources and most of it not published in peer reviewed literature.
- The industry requests PMRA to treat the material as “proprietary.” So this science remains hidden.
- PMRA relies mainly on U.S.A. studies (80 per cent of the studies reviewed in the early part of the decade.)
- Health Canada has a track record of approving pesticides, only to later phase them out due to health and environmental concerns. Examples: DDT, Eldrin, Diazinon, Dursan, Mecoprop.
- PMRA does not evaluate other chemicals in the formulation, so- called “inerts,” or the breakdown products.
Mr. Hepworth goes on to say “As for benefits ... well maintained public and private spaces make for happier healthier communities.” Happier I will not debate, but healthier? This I will argue is nonsense. In the comments on the web page, DB from NL worries at the use of the word “linked” when commenting on the link between pesticide exposure and different diseases. DB would like hard numbers and quantification.
I have great sympathy with this position, as epidemiology studies basically compare a cohort population that is exposed — in this case say to a group of farmers exposed to a pesticide — with a cohort matched as far as possible. These studies are almost always repeated to try to correct for possible biases — age, gender, race, smoking rates, etc.
To do a controlled double blind trial, as is done with prescription pharmaceutical drugs, is not possible. It would be totally unethical to deliberately expose a population to an insecticide and give a matched population an inert substance without either group knowing what they were being given and follow them for a very long time.
Cancers have a long latent period before being manifest. Just look at tobacco and smoking.
There are good websites available that give access to valid scientific studies that document the relationship between pesticides and disease time and time again ... and science has been showing this relationship for many, many years.
The following resources will, I think, convince DB from NL.
Look them up:
- Environmental health perspectives. Asthma 10 times commoner in children exposed to pesticides before age one.
- Medpage Today — Aberdeen University. Parkinson’s disease increased with exposure to pesticides. Low exposure nine per cent. High exposure, i.e. farmers, 45 per cent increase.
- Pubmed. These next studies show that exposure to pesticides in pregnancy increases the incidence of birth defects. This study shows that women in California living within 500 yards of fields being sprayed are 75 per cent more likely to have birth defects.
- Acta Paediatrica. A study of birth defects showed an increase for women who started their pregnancies in April to July. During those months the levels of nitrates, atrazine and other pesticides in the ground water were much higher than in other months
- American Journal of Epidemiology
- Globe and Mail April 2009
But the statistical correlation between the pesticide and the disease convinces me and most of the medical profession, especially those of us who see patients with these diseases. There is a relationship.
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