LONDON — People living in areas with high levels of air pollution are more likely to experience depression or take their own lives, according to an alarming study by researchers at the University College London.
The study used data from 16 countries in what authors say is the first systematic review and meta-analysis of links between fine particulate matter — small airborne particles including dust and soot — and various mental health problems. By the researchers’ calculations, if the relationship between depression, suicide, and air pollution is causal, then lessening the world-wide average exposure to fine particulate matter from 44 micrograms per meter cubed (μg/m3) to 25 μg/m3 would cause a 15% reduction in the global risk of depression.
According to the World Health Organization (WHO), fine particulate matter pollution should be under 10 μg/m3 for safety.
“We already know that air pollution is bad for people’s health, with numerous physical health risks ranging from heart and lung disease to stroke and a higher risk of dementia,” said lead author, Dr. Isobel Braithwaite, a UCL professor in Psychiatry, in a university release. “Here, we’re showing that air pollution could be causing substantial harm to our mental health as well, making the case for cleaning up the air we breathe even more urgent.”
The researchers analyzed prior studies that investigated the association between particulate matter air levels and five adverse mental health outcomes for adults. They analyzed 25 in all. They found that, on average, a 10 μg/m3 increase in the average fine particulate matter level individuals were exposed to for long periods of time was positively associated with a 10% increase in the odds of developing depression.
“We found quite consistent results across the studies we reviewed that analysed the relationship between long-term air pollution exposure and depression, even after adjustment for many other factors which could explain the association. The association seems to be similar in magnitude to those that have been found for some physical health impacts of particulate matter, such as all-cause mortality,” Dr. Braithwaite said.
The global range of urban air particulate levels studied was as high as 114 μg/m3 in Delhi, India and as low as 6 μg/m3 in Ottawa, Canada.
The research also revealed a connection between short-term high levels and changes in coarse particulate air matter exposure and suicide occurrences. The risk of suicide was higher on days when coarse particulate air matter was higher than normal over a three-day period than after less polluted time frames.
The study adjusted for other environmental factors like weather shifts and the day of the week. Researchers also controlled for neighborhood location and socioeconomic factors that contribute to depression and suicide.
The researchers aren’t ready to confirm that air pollution directly causes mental health problems, but they say there’s evidence suggesting possible causal relationships.
The study was published in the journal Environmental Health Perspectives.