[The Well] Study re: pesticides and Parkinson's Disease?
Cliff Treyens
Kimball, Greg
From the paper Well Water Consumption and Parkinson’s Disease in Rural California
p.4 Conclusion: Our study, the first to use agricultural pesticide application records, adds evidence that consumption well water presumably contaminated with pesticides may play a role in the etiology of PD.
My first reaction is that the whole study is based on groundwater from wells that are presumably contaminated. I think it is incredulous that an entire body of work can be based on a presumption of contamination and have no data of actual detectable concentrations. Can’t the possibility of contamination be backed up with some data of ongoing contamination from monitoring wells in fields, or adjacent to fields where the pesticide was applied. The presented random detections by PDR (200 detections of 95,000 samples = 0.2%) of “possible pesticide active ingredients and breakdown products” (page 19) and no indication of the validation of the results with quality assurance duplicates, or matrix spikes, etc. is not very strong evidence on which to presume contamination.
Was there any sampling of these private wells that indicated contamination from more common agricultural contaminants like nitrates? This would have added some credence to the presumably contaminated scenario.
With regards to eliminating ambient exposure, I did not see in the paper how the pesticides were commonly applied. Were they applied to the ground, sprayed from 6 feet above ground, or sprayed from crop dusters. Depending on the application method it would be very difficult to eliminate anyone living near the field from ambient exposure. They may not have been handling the pesticide but if it was sprayed and potentially carried in the air, wouldn’t everyone be subject to ambient exposure?
From the paper Well Water Consumption and Parkinson’s Disease in Rural California
p.19 An additional limitation is that our models for water contamination did not take into account some geological factors such as soil quality, groundwater depth and direction of groundwater flow that could influence the likelihood that a pesticide reaches the water drawn from private wells.
Hydrogeologically the authors noted their omission of the controlling factors for getting the pesticide to the groundwater receptors: soil and sediment composition, depth to groundwater, and groundwater flow direction (and position of the private well with respect to the flow). It would also be important to include the actual installation depths of the wells, as opposed to a generalized statement on p.5 that many wells are shallow. All this information (except maybe flow direction) should have been available and included in the analysis. It would be interesting if there was no difference in the chance for PD between people with deep wells and shallow wells or no difference between areas with more or less permeable soils. I think it becomes very difficult to presume contamination in well water and therefore claim that well water played a role in the etiology of PD, if the primary factors for controlling contamination of the groundwater do not indicate a difference.
greg kimball
hydrogeologist, P.G.
From: blmailer-thewell=ngwa.big...@biglist.com
[mailto:blmailer-thewell=ngwa.big...@biglist.com] On Behalf Of Cliff Treyens
Sent: Friday, August 07, 2009
11:10 AM
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Subject: [The Well] Study re:
pesticides and Parkinson's Disease?
The following link takes you to an Aug. 5 article in Environmental Health News (EHN) on the new study about a possible relationship between pesticides and Parkinson's Disease. NGWA has responded by providing information to EHN about ways well owners can generally reduce risks to their water supply through proper well location and construction, regular well maintenance, regular water testing and treatment (if necessary), and ground water protection.
However, we would be interested in NGWA members' comments and reactions to this news study. http://www.environmentalhealthnews.org/ehs/news/parkinsons-and-pesticides
Kevin McCray
In a news release issued this week the Western Plant Health Association claims the study has several flaws. The Western Plant Health Association is a trade group that represents pesticide manufacturers.
The following is generally from the WPHA news release:
“According to Renee Pinel, president and CEO of WPHA, one key clarification focuses on several of the ‘significant’ links reported in the study that involve pesticide exposure conditions. ‘Perhaps the study's authors lack of familiarity with pesticides and their 'best practices' for application resulted in their failure to recognize that these exposure conditions are very unlikely to occur,’ she said. For example, it is very unlikely for any participant in this individual study to have been exposed to 10 or more water soluble compounds, or 12 or more of the original 26 chemical compounds mentioned in the study. Some of these compounds are "not" water soluble, and therefore are not likely to be present in well water, Pinel points out.
“Pinel said readers need to keep in mind that this epidemiological study is the first such study to use agricultural records to reconstruct exposures, as opposed to determining past exposures through individual subject questionnaires and personal interviews. This means the data gathered is general in content and not derived from any specific findings linked to individuals who could have been monitored, she added.
‘As is the case in many similar health studies, the exposure assessment in this UCLA study is sorely lacking,’ she said. In this case, she notes, ambient pesticide concentrations within 500 meters of the homes of those under study were estimated from 25 years of California application records using a proprietary unpublished Global Information System-based instrument. This GIS mapping model does not take into account the effects of soil quality or groundwater depth on the estimated ambient pesticide exposures. Furthermore, several of the study compounds, as already mentioned, are not water soluble, rendering them very ineffective water contaminants, Pinel points out.
“Both of these factors led the authors to conclude that "our pesticide well water exposure estimates may not completely reflect actual levels of exposure to pesticides from consuming well water," she said.
‘This admission, in the context of this most recent UCLA study, merely serves as a glaring understatement as to the veracity and reliability of its findings,’ Pinel concluded.”
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Steve Lueck
It would be more reasonable to make this a sociological study given what they had to work with and the lack of real data. If the association between 25 years of pesticide application data and Parkinson’s disease is mathematically correct, it might be that if a person used pesticides on crops they would be likely to use pesticides in the home or the barn. Personal use of pesticides in hand sprayers would be much more likely to result in significant exposures than a cropduster applying pesticides 500 meters away.
The biggest problem with any study like this is the assumption that the person contracting the disease never did anything to facilitate their own exposure to the potential environmental triggers for the disease. I personally believe that exposure to pesticides could be a trigger for various maladies. Therefore, I read the directions and take precautions to minimize my exposure if I am going to use them.
>>> Kevin McCray <kmc...@ngwa.org> 8/13/2009 10:18 AM >>>