Long-term exposure to certain types of air pollution significantly increases the risk of developing Parkinson’s disease, according to a major new review led by researchers at the University of Cambridge.
The study, published in Environment International, analysed 26 existing studies on Parkinson’s disease affecting approximately six million people worldwide. Researchers found that two specific pollutants are associated with an elevated risk.
For every 5 μg/m³ of PM2.5, an individual’s relative risk of Parkinson’s increases by 10%. With average roadside PM2.5 measurements in Central London reaching 10 μg/m³ in 2023, the implications for urban populations are significant.
Similarly, for each 15 μg/m³ increase in PM10 – larger but still inhalable particles from sources including road dust, pollen, and vehicle emissions – the relative risk rises by 18%. Central London’s average roadside PM10 measurement stood at 17 μg/m³ last year.
Sources of these harmful particulates include exhaust and non-exhaust vehicle emissions, power plants, industrial processes, wood burning stoves, and construction dust.
The researchers found no conclusive evidence linking other pollutants such as nitrogen dioxide, carbon monoxide, or ozone to Parkinson’s, though they stressed this may reflect a lack of robust studies rather than an absence of risk.
The study also examined links to multiple sclerosis and motor neurone disease but found insufficient evidence, again highlighting the need for more research.
Dr Annalan Navaratnam, Clinical Research Fellow at Cambridge, said: ‘There are still relatively few robust studies that explore the link between air pollution and Parkinson’s disease, but even so, it’s becoming clear that there is a link. We found evidence of a link with two types of pollutants in particular, but even though the evidence was inconclusive for other types, this may be down to how the studies were designed. We urgently need more research, in larger populations, to examine what is a significant public health issue.’
The researchers suggest that oxidative stress and neuroinflammation triggered by air pollution – particularly PM2.5 – may interact with genetic susceptibility, leading to the abnormal protein build-up and neuron loss characteristic of Parkinson’s.
First author Alexandra Tien-Smith added: ‘These findings add to a growing and strong body of evidence of the many adverse health impact of air pollution worldwide ranging from a wide variety of diseases across every human organ system to premature mortality.’
To support policymakers, the Cambridge team has developed an open-access interactive tool mapping over 1,000 policy interventions to reduce traffic-related emissions, including congestion charging, low emissions zones, and active travel promotion.
Dr Haneen Khreis, also from Cambridge, added: ‘The message is clear: we need to take action now to improve air quality and help reduce the global burden of disease.
‘Our open access tool is intended to help researchers, practitioners, policymakers and third sector organisations understand the impact of different interventions on everything from traffic emissions and air pollution to human exposure, health impacts and unexpected co-benefits. We hope it aids and empowers those in a position to make a difference to implement effective and meaningful policies.’
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