Study links pesticides, Parkinson’s

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Published: April 10, 2008

Edith Daniels has no trouble recollecting when she was diagnosed with Parkinson’s disease.

“It was my 65th birthday present,” said the farmer from Clavet, Sask.

She doesn’t know for sure what triggered the debilitating illness, which causes stiffness, slowness and shakiness in her muscles, but her husband has always wondered if it had something to do with her exposure to the pesticides used on the farm where they have lived since 1964.

“We’ve often thought where it comes from and we knew chemicals was one possibility,” said Daniels, who was diagnosed six years ago.

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Researchers at Duke University and the University of Miami determined that a group of Parkinson’s patients were 1.6 times more likely to have been in direct contact with pesticides than their disease-free relatives.

“Previous studies have shown that individuals with Parkinson’s disease are over twice as likely to report being exposed to pesticides as unaffected individuals,” said lead author Dana Hancock.

“But few studies have looked at this association in people from the same family or have assessed associations between specific classes of pesticides and Parkinson’s disease.”

Researchers used telephone interviews to obtain the history of pesticide exposure of 319 patients and 296 of their relatives and other control subjects.

“Overall, individuals with Parkinson’s disease were significantly more likely to report direct pesticide application than their unaffected relatives,” according to the peer-reviewed study that appears on BioMed Central, an on-line journal that publishes biomedical research.

The strongest link was with insecticides and herbicides, specifically two insecticide classes: organochlorines and organophosphorus compounds.

However, there was no evidence that living or working on a farm was associated with an increased risk of developing Parkinson’s, which affects 100,000 Canadians.

Peter MacLeod, executive director of CropLife Canada, said the study is typical of epidemiology research.

“These types of studies in general use a lot of words like ‘associated,’ ‘linked,’ ‘may cause,’ ‘likely’ and ‘suggested,’ ” he said.

“They have to use that type of terminology because they can only suggest relationships. It’s not cause and effect.”

MacLeod said the study had a small sample size, offers confusing results and suffers from recall bias because people are asked to remember events that could have happened a long time ago.

For instance, males with the highest rate of exposure showed an association with the disease but so did females at the other end of the exposure spectrum.

“There are some results in there that don’t make logical sense,” he said, adding he knows of four other studies demonstrating no link between pesticides and Parkinson’s.

Daniels doesn’t know what to think. She noted that her husband was the one who mixed and applied the chemicals on their farm.

“If anybody should have it, as far as pesticides are concerned, it would be Rudy, not me,” she said.

Another theory is that Daniels may have been exposed to harmful chemicals in Ukraine and Germany, where she spent the Second World War diving into ditches to avoid explosions.

She vividly recalls taking shelter in a windmill outside Dresden, Germany, during the height of the Allied bombing campaign.

“We could read the newspaper at 2 a.m., that’s how bright it was because the whole city was burning.”

MacLeod said many steps have been taken to make pesticides less harmful.

The organochlorines and organophosphorus compounds that were commonplace in farm chemicals in the 1960s through the 1980s are not nearly as popular these days.

“They have been replaced by newer, more targeted products,” he said.

“All of the new insecticides you’ll see used on canola, for example, or pulse crops and sometimes cereals, they’re of a different class of products.”

He said CropLife’s member companies are continually developing new, safer molecules. The federal government rewards companies for introducing reduced risk products by providing a faster evaluation.

“That’s a very strong incentive,” MacLeod said.

Daniels doesn’t know for sure what triggered the disease but she does know how her body has to deal with it.

“My attitude is you don’t fight Parkinson’s, you make friends with it.”

Fighting creates tension, rendering her muscles even more stiff and unco-operative.

“It’s much easier to live with a friend than it is to live with an enemy,” she said.

About the author

Sean Pratt

Sean Pratt

Reporter/Analyst

Sean Pratt has been working at The Western Producer since 1993 after graduating from the University of Regina’s School of Journalism. Sean also has a Bachelor of Commerce degree from the University of Saskatchewan and worked in a bank for a few years before switching careers. Sean primarily writes markets and policy stories about the grain industry and has attended more than 100 conferences over the past three decades. He has received awards from the Canadian Farm Writers Federation, North American Agricultural Journalists and the American Agricultural Editors Association.

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