Prevalence of psychiatric disorders is significantly higher among people living in urban areas, says a meta-analysis of 20 pieces of research conducted over the past 35 years. If urban life is a serious concern for our health, mental wellbeing and outlook, then it is only going to become a greater issue for more of us as time passes. That figure is expected to rise to 68% by 2050, the United Nations estimates. Right now, 55% of the world’s population lives in urban areas.

The World Health Organization (WHO) now calls urban pollution levels a “public health emergency” because 91% of us live in areas where air pollution exceeds the agency’s guidelines.

How dirty air could affecting our gut health.

So, even moving from a low-pollution area into one of the cleaner cities could still increase your risk of respiratory diseases like emphysema – which is more commonly associated with smokers.

Generally, urbanites were exposed to between 10 and 25 parts per billion of ozone, where an increase of three parts per billion equates to smoking an extra pack of cigarettes each day.

The new study monitored ground-level ozone exposure in 7,000 adults living in cities across the US. While the effect on our lungs is undoubtedly troubling, we should also be wary of what the air we breathe is doing to the rest of our bodies. A recent study has likened city air pollution to smoking a pack of cigarettes each day for 29 years.

Have that effect on people