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| Arnie: | There is a lot of evidence that exposure to pesticides is associated with | PD. | David | | | >>Rick, | >>What product did you use when you flea bombed your band house? I can | >>trace | >>my PD onset back to incidents when I flea bombed my house 2X. I believe I | >>used D-Con. David | > | >What makes you think there is a connection? PD seems like a disease that | >takes decades to develop to the point that there are symptoms. | > | >Arnie I would say that there is suggestive evidence of an association of pesticide exposure and PD, but not nearly enough for someone to conclude that his/her PD is due to a particular exposure (except maybe in extreme cases). Before proceeding, I should introduce myself since I have mostly been lurking on this list. (By the way, what ARE these codes people use on the list with their signatures?) I am 64 years old and was diagnosed with PD about two years ago. My symptoms started about five years ago. They are currently well controlled by drugs. Professionally, I am an environmental scientist specializing in health effects of chemicals (among other things) and am now semi-retired and working half-time. Back to pesticides and PD. There are several distinct lines of evidence. For certain specific pesticides, there are animal studies (i.e., in lab rats and mice or other animals) showing PD-like symptoms, generally at doses much higher than people would normally be exposed to, along with studies of the biological mechanisms involved. In particular, these effects are seen with the pesticides paraquat, rotenone, and maneb. If these are not the pesticides you were exposed to, then you can't draw a conclusion from this evidence. There are also studies of the patterns of PD occurrence in humans. Techncially known as "case-control studies", these involve identifying a group of people with the disease and an otherwise similar control group without it, then asking questions of the subjects or their family members about the factors hypothesized as related to the disease. If people with and without the disease differ statistically on some of these questions, then those factors might be related to the cause of the disease. There are two obvious problems with this type of study: (1) what people remember is notoriously inaccurate, and (2) how the control group is chosen can influence the results. There are quite a few such studies where people are asked about exposure to pesticides as well as rural living, using well water, and working in agriculture. Some of the studies show relationships of these factors with occurrence of PD, while others do not. Still, relationships are found frequently enough that they are probably not entirely due to chance. (Lists of these studies are contained in the references I show at the end of this message. Almost all of them have at least an abstract on the Web.) The question is: what do these results mean? In most cases, there is no data on which pesticides were involved, for how long, under what conditions, etc. It is reasonable to speculate that, for the most part, the exposures in these studies are of pesticides used on a large scale in agriculture. So we cannot draw any conclusions about pesticides in general or about other kinds of pesticides, such as indoor fumigants. It gets worse. The variables that were evaluated in these studies are interrelated. For example, people who use well water are more likely than people in general to live on a farm and use pesticides. So you can't tell from such studies whether the "real" cause is, say, well water or pesticides, since they both tend to occur together. But it could be something else altogether that also tends to occur together with these factors. Let's suppose, to take a silly example that illustrates the point, that the real villain is driving a tractor (or being married to someone who does). Since people who drive tractors are more likely than others to live in rural areas, work in agriculture, be exposed to pesticides, and use well water, we would see the same patterns of results as is found in these studies. So there is something about having these characteristics that produces an increased risk of PD. But there is nothing to show that it has anything to do with pesticides. There are any number of differences in lifestyle between rural residents and the rest of the population. Rural residents may eat more fresh vegetables, have more contact with animals, be more religious and politically conservative, drink more beer and less wine, have more children and fewer sex partners, have less formal education, have older housing, be more physically fit, etc. etc. Does any of this have anything to do with PD? Who knows? But the evidence is as strong as for pesticides (except for the handful of pesticides where there is laboratory evidence, mentioned above). This is not as far-fetched as it may seem. First, there are the studies showing smokers, coffee drinkers, and alcohol drinkers are less likely to get PD. I would intepret this as probably resulting from people who have a tendency to addictive behavior having differences in the dopamine system in their brains. This conclusion is strenghthened by the recent clinical reports of PD patients taking dopamine agonists who suddenly became addicted to gambling or started engaging in uncharacterstic sexual behavior (and stop when they stop the drug). In addition, there is recent evidence for a genetic difference in some people's dopamine receptors that leads to "seeking novelty" (or perhaps "thrill seeking"). Maybe rural residents with this characteristic are more likely to leave the farm and move to the more exciting big city. What are the prospects for resolving this issue? Not very good, I would say. Repeating the same sort of case-control study would not add much. In principle, it is possible to perform a much larger study, where there are distinct groups separating the variables, such as people with well water who are not involved in agriculture, etc. This would be expensive, and it may not show anything. Similarly, one could do a prospective study, where the groups are identified at an early age and are followed until old age, actually measuring exposures along the way. Obviously, it would take many decades to carry out such a study. Finally, one could figure the mechanisms that cause PD, which might make it clear how these sorts of factors affect it. Scientists are working on this. My general conclusion: Except for people with a family history of PD or who have had repeated head trauma or certain very specific and unusual exposures, you have no way of knowing what caused or contributed to your disease. Maybe someday, we will understand enough about what causes it, but until then, it "just happens". For further information on environmental risk factors and PD, including references to the primary literature, check out the following: Logroscino G., The role of early life environmental risk factors in Parkinson disease: what is the evidence? Environmental Health Perspectives, 2005 Sep;113(9):1234-8. Full text at: http://ehp.niehs.nih.gov/members/2005/7573/7573.pdf Anumeet Priyadarshi, et al., Environmental Risk Factors and Parkinson's Disease: A Metaanalysis Environmental Research, Volume 86, Issue 2, June 2001, Pages 122-127 (You have to pay for the full text on the net, but I will e-mail it to anyone who is interested.) ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn