National Clothesline

A study released in November and widely publicized in the media suggests that exposure to perchloroethylene and tetrachloroethylene increases the likelihood of Parkinson’s disease.

Parkinson’s, a disorder that causes tremors and unsteady gait, afflicts some 700,000 Americans. The study considered 99 pairs of male twins in which one brother had Parkinson’s and the other did not. The researchers examined the work history of each dating back to age 10 and estimated their life-long exposures to six common solvents, then compared the exposures of the twins with and without Parkinson’s.

“We found that the twin who was exposed to a compound called trichloroethylene, or TCE, had a more than six-fold increased risk of having Parkinson’s disease than their unexposed co-twin,” said Dr. Samuel Goldman of The Parkinson’s Institute in Sunnyvale, CA. “And there were also some other solvents that we looked at as well, including one called perc, or perchloroethylene, which is the most common drycleaning solvent, and that was also associated with a markedly increased risk of Parkinsons.”

In particular, the study found that risk of Parkinson’s disease was increased six-fold in people who worked with TCE and 10-fold in those who worked with perc. The exposure preceded the onset of Parkinson’s by 30 to 40 years.

The most common occupational exposure settings for the two solvents were among electricians and drycleaners as well as people who repaired industrial machinery and artists.

“We’ve always believed that the vast majority of Parkinson’s disease is a consequence of environmental risk factors, but it’s important to recognize that this is a single study, so replication of our results is really important at this point,” Goldman said.

The Halogenated Solvents Industry Alliance, an association that represents manufacturers, producers, distributors and commercial users of perc, TCE and other halogenated solvents, urged caution in interpreting the study.

“The study design utilized a relatively-small population of white all-male twins who had jointly entered military service during World War II and where one of the twins was subsequently diagnosed with Parkinson Disease,” HSIA said.

HSIA said conclusions were made without any actual measured chemical exposure data. Instead, exposures were inferred based on occupations and hobbies with solvent exposures then being assumed based on those activities.

Further, HSIA noted that exposure information for nearly half of the group that had Parkinson’s was provided by a “proxy respondent,” that is a spouse or sibling.

Only ten out of 99 individuals from the Parkinson’s Disease group and three of 99 from the twin control group were even classified as being exposed to TCE, HSIA said.

“Given the limitations in the study, including the absence of confirmed solvent exposures, HSIA believes that it would not be appropriate to draw conclusions from this study about a causal association between solvent exposures and Parkinson’s,” the association said.

HSIA said it believes the solvents can be handled and used safely given current technology and methods. Users should follow all applicable regulations as well as the information contained in Material Safety Data Sheets.

The study said that the fact that exposures preceded Parkinson’s disease onset by several decades suggests that understanding the toxic mechanism could make it possible to potentially intervene to prevent Parkinson’s disease.

“Currently there really is no way that we’re aware of to delay or prevent Parkinson’s disease,” Goldman said. “I think the most important thing we can do right now is to replicate this observation and if it’s found to be a consistently observed link between exposure to these compounds and Parkinson’s, I would hope that the funding agencies would really get behind this work and help us move it forward.”

Parkinson’s disease is the second most common neurodegenerative disorder after Alzheimer's. It effects about 0.3 percent of the entire population in industrialized countries, but is more common in the elderly. The incidence rises to one percent of the population over age 60 and four percent over 80.



								National Clothesline


						Study connects perc exposure with Parkinson’s



						A study released in November and widely publicized in the media suggests that exposure to perchloroethylene and tetrachloroethylene increases the likelihood of Parkinson’s disease. Parkinson’s, a disorder that causes tremors and unsteady gait, afflicts some 700,000 Americans. The study considered 99 pairs of male twins in which one brother had Parkinson’s and the other did not. The researchers examined the work history of each dating back to age 10 and estimated their life-long exposures to six common solvents, then compared the exposures of the twins with and without Parkinson’s. “We found that the twin who was exposed to a compound called trichloroethylene, or TCE, had a more than six-fold increased risk of having Parkinson’s disease than their unexposed co-twin,” said Dr. Samuel Goldman of The Parkinson’s Institute in Sunnyvale, CA. “And there were also some other solvents that we looked at as well, including one called perc, or perchloroethylene, which is the most common drycleaning solvent, and that was also associated with a markedly increased risk of Parkinsons.” In particular, the study found that risk of Parkinson’s disease was increased six-fold in people who worked with TCE and 10-fold in those who worked with perc. The exposure preceded the onset of Parkinson’s by 30 to 40 years. The most common occupational exposure settings for the two solvents were among electricians and drycleaners as well as people who repaired industrial machinery and artists. “We’ve always believed that the vast majority of Parkinson’s disease is a consequence of environmental risk factors, but it’s important to recognize that this is a single study, so replication of our results is really important at this point,” Goldman said. The Halogenated Solvents Industry Alliance, an association that represents manufacturers, producers, distributors and commercial users of perc, TCE and other halogenated solvents, urged caution in interpreting the study. “The study design utilized a relatively-small population of white all-male twins who had jointly entered military service during World War II and where one of the twins was subsequently diagnosed with Parkinson Disease,” HSIA said. HSIA said conclusions were made without any actual measured chemical exposure data. Instead, exposures were inferred based on occupations and hobbies with solvent exposures then being assumed based on those activities. Further, HSIA noted that exposure information for nearly half of the group that had Parkinson’s was provided by a “proxy respondent,” that is a spouse or sibling. Only ten out of 99 individuals from the Parkinson’s Disease group and three of 99 from the twin control group were even classified as being exposed to TCE, HSIA said. “Given the limitations in the study, including the absence of confirmed solvent exposures, HSIA believes that it would not be appropriate to draw conclusions from this study about a causal association between solvent exposures and Parkinson’s,” the association said. HSIA said it believes the solvents can be handled and used safely given current technology and methods. Users should follow all applicable regulations as well as the information contained in Material Safety Data Sheets. The study said that the fact that exposures preceded Parkinson’s disease onset by several decades suggests that understanding the toxic mechanism could make it possible to potentially intervene to prevent Parkinson’s disease. “Currently there really is no way that we’re aware of to delay or prevent Parkinson’s disease,” Goldman said. “I think the most important thing we can do right now is to replicate this observation and if it’s found to be a consistently observed link between exposure to these compounds and Parkinson’s, I would hope that the funding agencies would really get behind this work and help us move it forward.” Parkinson’s disease is the second most common neurodegenerative disorder after Alzheimer's. It effects about 0.3 percent of the entire population in industrialized countries, but is more common in the elderly. The incidence rises to one percent of the population over age 60 and four percent over 80.