Smog may be raising anxiety levels in cities around the world

BOSTON, March 25 (UPI) -- Air pollution has long been blamed for heightened rates of heart disease. Now, two new studies suggest smog levels are linked to inflated instances of stroke and anxiety.

Previous research has shown long-term exposure to soot and smog to be associated with a higher risk of stroke, but a new study by researchers at Edinburgh University is one of the first to link especially smoggy days with an uptick in stroke hospitalizations.

Researchers looked at dozens of studies from all over the world that focused on the health effects of particle pollution -- specifically respirable suspended particles and fine particles.

Respirable suspended particles, or coarse particulates, are also known as PM 10, and consist of suspended particles with a diameter of 10 micrometers or less. Fine particles, ultra-fine particles and soot are often referred to as PM 2.5, as they consist of particles with a diameter of 2.5 micrometers or less.

Their analysis -- published this week in the British Medical Journal -- suggested that for every 10 micrograms of PM 10 and PM 2.5 per meter cubed of air, there is 1.1 percent increased chance of stroke hospitalization or death.

Perhaps the more surprising new particle pollution study is the one that suggests a link with anxiety.

Conducted by researchers at Harvard and John's Hopkins universities, the study looked at responses from mental health questionnaires and changing levels of pollution over a 15-year period.

The study -- which included response from more than 71,271 women as part of the 2004 Nurses' Health Study -- showed that respondents with a history of higher pollution exposure were more likely to report symptoms of anxiety, including fearfulness, desire for avoidance and a tendency to worry.

The research showed higher rates of anxiety for those living within roughly 150 to 650 feet of a major road. The tendency was found to be stronger for those with more recent pollution exposure.

"Since air pollution causes systemic inflammation, it is reasonable that researchers have now turned to the arena of mental health, a leading priority for research given the relative absence of known modifiable risk factors and a high and growing disease burden," Michael Brauer, a public health professor at the University of British Columbia, wrote in an editorial accompanying the two studies in the BMJ.

Previous research has located correlations between air pollution exposure during pregnancy and autism diagnoses.