Does Air Pollution Intensify Mental Disorders?

A study from Hong Kong has suggested that exposure to elevated levels of air pollution could intensify mental and behavioural disorders, leading to a higher risk of mortality. The paper, published in the journal Environmental International, analysed statistics compiled from more than 284,000 deaths over a seven year period and found a correlation between pollution and death.

Though the authors are unsure as to how exactly the poor air quality brought about the higher incidences of death and suicide, they have stressed that more research is needed. In the interim, they have also called for the government to do more to provide support to vulnerable people and to curb air pollution, which they see as the major priority in bringing down the mortality rate.

Haze days and heightened death risk

The authors of the paper analysed the number of haze days between 2007 and 2014, cross-referencing this information with the number of deaths over the same period. For the purposes of the research, a haze day is defined as a dry day with no or low wind speeds, during which air pollutants build up and block visibility.

Over the period in question, there were 11 such days when pollution levels were twice their normal amount. Given Hong Kong’s proximity to China, and the fact that Chinese power plants emit as much nitrogen oxides (NOX) as all the passenger cars in the world, it’s unsurprising that the territory regularly suffers from such poor air quality.

It was found that a haze day increased general risk of mortality by 2.9% - but among those suffering from a mental or behavioural disorder, that percentage surged to much higher. On the first day of haze, the likelihood of death rose by 16%, while if it was followed by a successive haze day it leapt up by 27%. Perhaps most concerningly of all, a haze day which coincided with high levels of ozone contamination saw the mortality risk soar by 79%.

In keeping with previous suspicions

It has been suspected for some time that air pollution can affect the brain as well as the body, and this latest Hong Kong paper only serves to strengthen that suspicion. A recent Belgian study found that there was a direct correlation between outdoor air pollution and suicide, even when contamination levels were below the recommended “safe” level by the EU.

An American investigation into suicides in Salt Lake City found a similar link between death and nitrogen dioxide (NO2), while a South Korean study came to the same conclusions regarding levels of the pollutant ozone. Meanwhile, both Japan and China have linked suicide to NO2 and sulphur dioxide (SO2), respectively. Although all of these studies do suggest that air pollution can trigger suicidal tendencies in those suffering from mental disorders, the researchers of the Hong Kong paper have called for further studies and, above all, help for those affected.

“First of all we need more support to those high-risk groups,” remarked Lin Yang, one of the authors of the paper. “Currently we have a lot of social workers to give support to people with mental disorders. But they probably need to pay attention to the fact that haze events could be a trigger for acute onset of symptoms.”