{"id":1628,"date":"2011-11-22T09:19:22","date_gmt":"2011-11-22T14:19:22","guid":{"rendered":"http:\/\/blogs.edf.org\/nanotechnology\/?p=1628"},"modified":"2014-03-25T12:56:48","modified_gmt":"2014-03-25T17:56:48","slug":"twin-dangers-from-tce-widespread-exposure-and-now-a-strong-link-to-parkinson-disease","status":"publish","type":"post","link":"https:\/\/blogs.edf.org\/health\/2011\/11\/22\/twin-dangers-from-tce-widespread-exposure-and-now-a-strong-link-to-parkinson-disease\/","title":{"rendered":"Twin dangers from TCE: Widespread exposure, and now a strong link to Parkinson disease"},"content":{"rendered":"

Jennifer McPartland, Ph.D.<\/em><\/a>, is a Health Scientist. <\/em><\/p>\n

A study published online in the Annals of Neurology last week, \u201c<\/span>Solvent Exposures and Parkinson Disease Risk in Twins<\/span><\/a>,\u201d adds to scientific <\/span>evidence linking<\/span><\/a> exposure to the solvent trichloroethylene, or <\/span>TCE<\/span><\/a>, and other common solvents with onset of Parkinson disease.\u00a0 <\/span>Parkinson disease<\/span><\/a> is a debilitating condition well known for symptoms of trembling but <\/span>can also include<\/span><\/a> slowed motion, impaired posture and balance, and loss of automatic movements (e.g.<\/em> blinking, arm swaying when walking).\u00a0 Most unfortunately, it has no cure.\u00a0 <\/span><\/p>\n

According to the authors, this new twin study is the first confirmation in a population-based study of a significant association between exposure to TCE and incidence of Parkinson disease.\u00a0\u00a0\u00a0<\/span><\/p>\n

What we already know about the ill effects of TCE exposure<\/span><\/strong><\/p>\n

TCE was first commercially produced in the 1920s and has served various purposes since that time.\u00a0 <\/span>It is estimated<\/span><\/a> that 80\u221290% of global TCE production is used for degreasing metals.\u00a0 <\/span><\/p>\n

Commonly associated health effects associated with <\/span>inhalation exposure to TCE<\/span><\/a> include lung irritation, dizziness, poor coordination and difficulty concentrating.\u00a0 EPA\u2019s Integrated Risk Information System (IRIS) <\/span>toxicological review of TCE<\/span><\/a> (<\/span>finally issued<\/span><\/a> in September 2011) concludes that TCE poses \u201c<\/span>potential human health hazard for\u2026toxicity to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing fetus.\u201d\u00a0 And it further states that the scientific evidence supports the conclusion that TCE is \u201ccarcinogenic in humans by all routes of exposure.\u201d<\/p>\n

The IRIS review did include some discussion on TCE exposure and Parkinson disease, but could not give it much consideration owing to limited data.\u00a0 The review notes, \u201cIf indeed TCE can target dopamine neurons, it would be anticipated that human exposure to this agent would result in elevated rates of parkinsonism. There are no systematic studies of this potential relationship in humans\u2026.\u201d\u00a0 This new twin study would have helped EPA evaluate the weight of evidence for an association for TCE exposure and Parkinson disease.<\/p>\n

What the new study tells us<\/strong><\/p>\n

In this study, ninety-nine pairs of twin males, one of whom has Parkinson where the other does not, were assessed for their exposure to solvent chemicals that have been associated with Parkinson disease either \u201canecdotally\u201d or in other studies.\u00a0 By using twins, the investigators sought to reduce the influence of confounding factors such as differences in genetics, demographics, and lifestyle.<\/span><\/p>\n

In addition to TCE, the investigators examined associations between onset of Parkinson disease and exposure to the solvents n-hexane, xylene, toluene, carbon tetrachloride, and PERC (perchloroethylene).\u00a0 The researchers found that exposure to TCE resulted in a six-fold increase of risk for developing Parkinson disease. \u00a0In addition, they found that exposures to PERC and carbon tetrachloride, \u201ctended toward significantly increased risk\u201d of developing the disease.\u00a0 A statistically significant association was not identified for the other solvents.<\/span><\/p>\n

The methodology of the study was quite interesting:\u00a0 The investigators used detailed questionnaires to evaluate exposure of the twin subjects to the six solvent chemicals, including both occupational and hobby sources of exposure.\u00a0 For any particular occupation, having been \u201cever\u201d exposed to a solvent was defined as exposure for at least 2% of work time or 1 hour per week.\u00a0 The researchers also collected information on lifetime history of smoking and head injury, which are other factors considered to influence the onset of Parkinson disease.\u00a0 <\/span><\/p>\n

Evidence of widespread exposure to TCE<\/span><\/strong><\/p>\n

If it isn\u2019t alarming enough that exposure to a chemical increases the risk of developing Parkinson disease, the sirens really go off when we consider just how widespread exposure to the implicated chemicals are.\u00a0 For TCE:<\/span><\/p>\n