Environmental factors and Parkinson’s

The causes of Parkinson’s are complex and still not fully understood. For the vast majority of people with the condition, there's no way to tell what has caused them to develop Parkinson’s. 

For most people it’s likely that a combination of factors contribute to the development of the condition. These may include:

• Ageing - this is the number one risk factor for Parkinson’s
• Genetics - the genes people inherit from their parents can play a part in risk of developing Parkinson’s
• Environmental - things people are exposed to over the course of their lives which they have limited control over (eg. pollution)
• Lifestyle - things in life that people have more control over, such as diet and exercise or smoking

Researchers are still working to unravel this complex mix of factors to develop a better understanding of the causes of Parkinson’s. 

In this blog we take a look at some of the leading environmental factors that have been identified so far.

Pesticides and herbicides

Pesticides and herbicides are chemicals that are used to kill pests, such as insects and weeds. 

These chemicals work by targeting a specific function of the insect’s or plant’s biology to kill the unwanted pest. Different pesticides will come with different warnings to human health and instructions should always be followed. They're regulated in the UK, and beyond, to help protect us from harmful effects.

A variety of studies have investigated the possible link between pesticides, herbicides and Parkinson’s.

The results have been varied, but overall the current evidence suggests that unsafe exposure, for instance through contaminated water or using hazardous chemicals for a long time without appropriate protection, may increase risk of Parkinson’s. How much this risk is increased can depend on many things, and is very difficult to measure for an individual.

Key chemicals identified so far include Paraquat and Rotenone which are both already banned in the UK. Paraquat has been banned since 2007, and Rotenone since 2009. There is also some evidence that a common weedkiller, Glyphosate, may be linked to Parkinson’s, however the evidence isn’t clear cut. Glyphosate is currently still in use in the UK.

You can read more about pesticides and Parkinson’s on our research blog.

Other environmental factors associated with Parkinson’s

Trichloroethylene

Trichloroethylene (or TCE) is a chemical solvent that has been used as a degreaser in many industries, including dry-cleaning. Exposure to unsafe levels of TCE has been linked to Parkinson’s in animal studies, and in a small number of case studies in people. Lab studies suggest that TCE might damage cells in the brain that produce dopamine, but understanding how it might be having an effect in humans is more challenging.

The use of TCE in the UK is now controlled and it hasn’t been used in dry-cleaning since the 1950s.

Air pollution

Air pollution is one of the main global health risks for many health conditions and has already been linked with heart disease, stroke, lung cancer, respiratory diseases, diabetes and Alzheimer’s.

Recent research indicates that air pollution from factory emissions, cars, planes, and even wood burners might be a risk factor for Parkinson’s.

This could be because small particles of pollution can be toxic once they reach the brain, and cause inflammation. But it’s hard to know whether pollution is increasing the risk of Parkinson’s, or simply speeding it up. The UK Government has committed to improving air quality.

Heavy metals

Heavy metals such as lead, copper or mercury have been linked to Parkinson’s, with previous studies showing that people who have worked for a long time in industries that use heavy metals are more likely to develop Parkinson’s. Further research suggests that people with a particular change in one of their genes (called PARK2) were more susceptible to develop Parkinson’s symptoms after prolonged contact with heavy metals, highlighting the important link between genetic and environmental factors when considering Parkinson’s risk.

Are environmental factors causing an increase in Parkinson’s?

As we’ve said before, it’s very difficult to understand exactly what’s caused someone’s Parkinson’s. When it comes to environmental factors, it’s particularly challenging to study whether an individual factor in isolation is having a direct effect on having caused someone's Parkinson’s. 

Our research shows that the prevalence of Parkinson’s is on the rise in the UK, due to a growing and ageing population. But the incidence, or the number of new cases of Parkinson’s, isn’t increasing in the UK. 

Exposure to many of the risk factors mentioned in this blog are going down rather than up as regulations on the use of industrial and agricultural chemicals are tightened, PPE improves and efforts are made to reduce air pollution. We’ll need more research looking at all of these factors and more before we can know what impact the environment is having. 

Read more about the prevalence of Parkinson’s in the UK on our blog.

Should more be done to reduce exposure to environmental risk factors for Parkinson’s?

There is an urgent need for better quality, independent studies to be conducted into the possible links between environmental factors and their health impacts, including Parkinson’s.

Exposure to chemicals, toxins and pollution in our environment are likely to have wide-ranging impacts on health, and these need to be fully understood to enable regulatory authorities to make decisions that safeguard people and the environment.