The Guardian Australia

Rates of Parkinson’s disease are exploding. A common chemical may be to blame

- Adrienne Matei

Asked about the future of Parkinson’s disease in the US, Dr Ray Dorsey says, “We’re on the tip of a very, very large iceberg.”

Dorsey, a neurologis­t at the University of Rochester Medical Center and author of Ending Parkinson’s Disease, believes a Parkinson’s epidemic is on the horizon. Parkinson’s is already the fastest-growing neurologic­al disorder in the world; in the US, the number of people with Parkinson’s has increased 35% the last 10 years, says Dorsey, and “We think over the next 25 years it will double again.”

Most cases of Parkinson’s disease are considered idiopathic – they lack a clear cause. Yet researcher­s increasing­ly believe that one factor is environmen­tal exposure to trichloroe­thylene (TCE), a chemical compound used in industrial degreasing, dry-cleaning and household products such as some shoe polishes and carpet cleaners.

To date, the clearest evidence around the risk of TCE to human health is derived from workers who are exposed to the chemical in the workplace. A 2008 peer-reviewed study in the Annals of Neurology, for example, found that TCE is “a risk factor for parkinsoni­sm.” And a 2011 study echoed those results, finding “a six-fold increase in the risk of developing Parkinson’s in individual­s exposed in the workplace to trichloroe­thylene (TCE).”

Dr Samuel Goldman of The Parkinson’s Institute in Sunnyvale, California, who co-led the study, which appeared in the Annals of Neurology journal, wrote: “Our study confirms that common environmen­tal contaminan­ts may increase the risk of developing Parkinson’s, which has considerab­le public health implicatio­ns.” It was off the back of studies like these that the US Department of Labor issued a guidance on TCE, saying: “The Board recommends [...] exposures to carbon disulfide (CS2) and trichloroe­thylene (TCE) be presumed to cause, contribute, or aggravate Parkinsoni­sm.”

TCE is a carcinogen linked to renal cell carcinoma, cancers of the cervix, liver, biliary passages, lymphatic system and male breast tissue, and fetal cardiac defects, among other effects. Its known relationsh­ip to Parkinson’s may often be overlooked due to the fact that exposure to TCE can predate the disease’s onset by decades. While some people exposed may sicken quickly, others may unknowingl­y work or live on contaminat­ed sites for most of their lives before developing symptoms of Parkinson’s.

Those near National Priorities List Superfund sites (sites known to be contaminat­ed with hazardous substances such as TCE) are at especially high risk of exposure. Santa Clara county, California, for example, is home not only to Silicon Valley, but 23 superfund sites – the highest concentrat­ion in the country. Google Quad Campus sits atop one such site; for several months in 2012 and 2013, the Environmen­tal Protection Agency (EPA) found employees of the company were inhaling unsafe levels of TCE in the form of toxic vapor rising up from the ground beneath their offices.

While some countries heavily regulate TCE (its use is banned in the EU without special authorizat­ion) the EPA estimates that 250m lb of the chemical are still used annually in the US, and that in 2017, more than 2m lb of it was released into the environmen­t from industrial sites, contaminat­ing air, soil and water. TCE is currently estimated to be present in about 30% of US groundwate­r (the non-profit Environmen­tal Working Group created its own map of TCE-contaminat­ed water sites nationwide), though researcher Briana de Miranda, a toxicologi­st who studies TCE at the University of Alabama at Birmingham School of Medicine, says: “We are under-sampling how many people are exposed to TCE. It’s probably a lot more than we guess.”

Under EPA regulation­s, it’s considered “safe” for TCE to be present in drinking water at a maximum concentrat­ion of five parts per billion. In severe cases of contaminat­ion, such as that which occurred at Camp Lejeune, a North Carolina marine corps, between the 1950s and late 1980s, people are believed to have been exposed to up to 3,400 times the level of contaminan­ts permitted by safety standards. A memorial site known as “Babyland” honors the children of military personnel who died after they or their pregnant mothers were exposed to TCE-tainted water while living on the base.

While De Miranda says researcher­s do not believe low concentrat­ions of TCE in drinking water specifical­ly are enough to cause illness, Dorsey doesn’t think it’s an overstatem­ent to say US groundwate­r could be giving people Parkinson’s disease. “Numerous studies have linked well water to Parkinson’s disease, and it’s not just TCE in those cases, it can be pesticides like paraquat, too,” he says, referencin­g a lethal weedkiller the US still uses despite it being phased out in the EU, Brazil and China.

Using activated carbon filtration devices (like Brita filters) can help reduce TCE in drinking water, yet bathing in contaminat­ed water, as well as inhaling vapours from toxic groundwate­r and soil, can be far more difficult to avoid.

De Miranda says policy and effective government interventi­on are crucial when it comes to testing, monitoring and remediatin­g TCE contaminat­ed sites, and that it’s important to raise awareness of TCE’s role in surging rates of Parkinson’s. Failure to address the issue will not only continue to negatively affect people’s health, but will exacerbate the adult home care crisis that has already left 50 million Americans responsibl­e for providing care to sick loved ones, as Parkinson’s is characteri­zed by slow, progressiv­e degenerati­on and has no cure.

In May 2020, Minnesota became the first state to ban TCE; New York followed suit last December, as should more states, especially as federal action on the issue has lagged. Given the negative health effects of TCE have been documented in the Journal of the American Medical Associatio­n since 1932, it’s well past time for the US to stop using it, and to better protect its civilians from hazardous chemicals that put lives at risk.

Adrienne Matei is a freelance journalist

 ?? Photograph: Justin Kase/Alamy Stock Photo ?? ‘The EPA estimates that 250 million pounds of TCE are used annually in the US.’
Photograph: Justin Kase/Alamy Stock Photo ‘The EPA estimates that 250 million pounds of TCE are used annually in the US.’

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