A recent UCLA study that claims there's a link between Parkinson's disease and pesticides in well water has several flaws, according to Renee Pinel, president and CEO of the Western Plant Health Association in Sacramento, a trade group in Sacramento that represents pesticide manufacturers.

According to Pinel, 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 said.

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of the homes of those under study were estimated from 25 years of California application records using a proprietary unpublished Global Information System-based instrument.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 said.

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.

The Western Plant Health Association represents the interests of fertilizer and crop protection manufacturers, biotechnology providers, distributors and agricultural retailers in California, Arizona and Hawaii. WPHA members comprise more than 90 percent of all the companies marketing plant nutrients, soil amendments, agricultural minerals and crop protection products in California, Arizona and Hawaii.