Researchers believe a factor is a chemical used in drycleaning and household products such as shoe polishes and carpet cleaners
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.
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. …