Experts have called for stricter air pollution targets to tackle the risk of dementia after studies revealed a potential link between poor air quality and the condition.
Research now links pollution to an increased risk of dementia, even at levels below UK, US and EU air quality standards.
A team at the Harvard TH Chan School of Public Health in the US looked at 14 studies examining the link between dementia and exposure to fine particulate matter (PM2.5), an air pollutant made up of tiny pieces of solid or liquid substances, inhaled by people as they breathe.
Their findings, Tpublished in the BMJ journal indicate that for every two micrograms per cubic metre increase in average annual PM2.5 concentration, the overall risk of dementia rises by 4%.
Other studies suggest that exposure to nitrogen dioxide and nitrogen oxide gases – produced by the burning of fossil fuels – may also pose an increased risk for developing dementia.
The Harvard researchers said the results “strengthen the evidence that air pollutants are risk factors for dementia”.
Likewise experts from University College London in the UK warned that air pollution had the “potential to substantially affect dementia risk”.
They wrote: “Current estimates suggest that PM2.5 concentrations in major cities vary considerably from below 10 micrograms per cubic metre in some cities (eg Toronto, Canada) to more than 100 micrograms per cubic metre in others (eg Delhi, India), therefore, air pollution has the potential to substantially affect dementia risk globally.”
Air pollution has also been linked to an increased risk of other health conditions, with an estimated 6.5 million deaths attributable to air pollution each year.
“Although individuals can take steps to reduce their own personal exposure, for example, by remaining indoors on high air pollution days, this solution is impractical in the long term, so for many people, the risk is inescapable,” they added.
“[The] findings therefore add urgency to the need for effective policy measures to reduce air pollution globally.”
Dr Susan Mitchell, head of policy at the charity Alzheimer’s Research UK, said: “Poor air quality is a significant public health issue, and this new review helps to cement the relationship between certain types of air pollution and dementia risk.
“But as individuals there’s little we can do about the air we breathe. So it’s vital the government leads from the front in reducing air pollution and the resulting harm to our brain health.
“But what we have seen so far has fallen disappointingly short. In December, the government missed a clear opportunity for decisive action on air pollution by setting an unambitious and inadequate target of 10 micrograms a cubic metre by 2040 – far less stringent than what Alzheimer’s Research UK and the World Health Organization recommended.
“The government should now ensure brain health is central to its major conditions strategy and its wider ambitions for prevention, and invest in population-level interventions that have significant impact on air pollution.
“What remains to be uncovered is the ‘how’ – there are several biological explanations that could be behind the link between air pollution and dementia, and we echo the authors’ call for more research to better our understanding in this area.”
Syntegra’s Director of Air Quality, Mark Chapman, said: “Links between air pollution and poor health are becoming stronger all the time.
“Repeated research projects identify evidence that points to air pollution causing a range of life threatening illnesses.
“Now we have this link to dementia and it is vital that Governments act immediately to tackle the risks posed by pollution and provide the public with clean air to improve their overall health and wellbeing.
“Dementia is a terrible problem and it is unthinkable that ministers and private companies will continue to turn a blind eye to potential causes and solutions.”