Millions of people risk increasing their risk of dementia just by breathing, a new long-term study has found.
Inhaling air polluted by wildfire smoke has been found to be even worse than breathing air polluted by vehicles and factories (not that the two are always mutually exclusive).
A ten-year study of 1.2 million older adults in California between 2009 and 2019 found wildfire smoke exposure ‘greatly raises’ the risk of dementia, more than previously realised.
Lead study author Holly Elser said: ‘Air pollution produced by wildfires now accounts for more than 70% of total PM2.5 exposure on poor air quality days in California. This is a real problem.’
As the climate warms, grass and forest fires are becoming more frequent and severe around the world in hot and dry conditions.
Millions of people in the western US and Canada were placed under air quality alerts last week as fires forced thousands to evacuate their homes.
Extreme heat has also hit parts of the Mediterranean and Balkans, with temperatures forecast to go over 40°C and major fires in Greece.
The new research was presented at the Alzheimer’s Association International Conference on Monday.
None of the adults in the study had dementia when they were enrolled at the start. Researchers worked out how much pollution they had likely been exposed to, and from which sources, by studying air quality where they lived over the ten-year period.
Fine particulate matter (PM2.5) is what causes the problems. It is a microscopic mixture of solid and liquid droplets in the air that are 30 times smaller than the width of an average human hair: small enough to be inhaled into the lungs and then move to the bloodstream.
The study found that the risk from wildfire pollution was more dangerous to brain health than non-wildfire PM2.5, even if the exposure was less.
It was not clear exactly why this may be, but researchers theorised it could be because wildfire PM2.5 are produced at higher temperatures, contain a more concentrated mix of toxic chemicals and, on average, are smaller in diameter than from other sources.
Claire Sexton, Alzheimer’s Association senior director of scientific programs, said: ‘With the rising global incidence of wildfires, exposure to this type of air pollution is an increasing threat to brain health.
‘These findings underscore the importance of enacting policies to prevent wildfires and investigating better methods to address them.’
High levels of fine particulate matter have also have been shown to raise the risk of heart disease, asthma and low birth weight.
To reduce the risks, people were urged to update their home air filtration systems when possible, stay inside where possible when the air quality is unhealthy, and wear an N95 mask outside when the Air Quality Index reaches 100.
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