Exposure to Air Pollution Not Linked to Parkinson’s, Study Suggests

Long-term exposure to outdoor air pollution does not directly contribute to the development of Parkinson’s disease later in life, results from a Dutch study suggest.

Still, non-smoking women and people with long-term residential stability were found to be at greater risk of developing the disease, according to the study.

The study, “Parkinson’s disease and long-term exposure to outdoor air pollution: A matched case-control study in the Netherlands,” was published in the journal Environment International.

The cause of Parkinson’s disease remains largely unknown, though researchers suspect a combination of environmental and genetic factors. Despite efforts to uncover possible risk factors and contributors for Parkinson’s development and progression, the available data are still controversial. Studies have demonstrated that exposure to pesticides is a risk factor; in contrast, exposure to cigarette smoke can be protective.

Ambient air pollution has also been suggested as a potential risk factor for the development of Parkinson’s through various biological processes. However, studies performed on this topic have so far been inconsistent in their findings.

Therefore, a group of researchers from the Netherlands and Chile conducted a study to better understand the association between long-term exposure to ambient air pollution particles and the development of Parkinson’s disease.

Exposure to air pollution, which was defined as exposure to particulate matter with an aerodynamic diameter of less than 10 μm [PM₁₀], less than 2.5 μm [PM_2.5], between 2.5 μm and 10 μm [PM_coarse], black carbon, and nitrogen oxides [NO₂ and NO_x], were predicted based on a statistical model developed within the European Study for Air Pollution Effects (ESCAPE) study.

A total of 1,290 subjects, 436 of whom were Parkinson’s patients and 854 without progressive neurological disorders, were recruited from five hospitals in four cities in the Netherlands, and 16 years of air pollution exposure were estimated.

In general, the team did not find any significant relationship between exposure to ambient air pollutants and Parkinson’s disease, regardless of the type of pollutant.

The risk of developing Parkinson’s disease was found to be similar between individuals who had been more exposed to air pollutants and those who had been less exposed. In fact, the team reported a trend for a protective effect, with people more exposed having a slightly reduced risk. But these differences were not found to be statistically relevant.

“We found no clear association between 16 years of residential exposure to ambient air pollution and the development of Parkinson’s disease in The Netherlands,” researchers said.

Still, in additional analysis the team found evidence that non-smoking women and those who lived for at least 14 years at the same residence were at higher risk of developing Parkinson’s disease with increased exposure to ambient air pollution. However, given the limited number of participants, further studies are required to validate these subgroup findings.

“Additional work, considering longer exposure times, may assist in further understanding what (if any) role ambient air pollution plays in the risk of developing Parkinson’s disease,” researchers concluded.