We know that pollution kills. Carbon dioxide & nitrous oxide emissions in particular have lasting and profound consequences on our health. Depending on the time of day, the time of year and the specific city, some people involuntarily smoke the equivalent of two or three cigarettes a day just for the sake of walking outdoors. In other words, breathing the air of large cities reduces our life expectancy little by little.
So, what happens when we reduce pollution?
More life. We gain life expectancy. At least it is the conclusion we can draw from a recent study published by the University of Stockholm. In it, several researchers have used the historical series compiled by the measurement stations in three large Swedish cities (Stockholm, MalmÃ¶ and Gothenburg) to analyze how pollution has been reduced and what consequences this reduction has had on health of its inhabitants.
Answer: a year of life gained to life expectancy thanks to a cleaner air.
The numbers. Swedish cities have been trying for years to reduce the pollutant footprint of private vehicles in their streets. They have exemplary public transport services, with some limitations to the circulation of the car and with a notable penetration of the bicycle as a modal alternative. In return, nitrous oxide levelsÂ have gone from 40 micrograms per cubic meter in 1990 to 20 micrograms in 2015.
The origin of the reduction, fundamentally, is ascribed to traffic.
Health. The effect of particles and nitrous oxide on human health is well known. Some studies indicate that for every 10 micrograms of particles that we breathe, our chances of contracting respiratory or cardiovascular diseases increase by 3%. Since we breathe around 20,000 times in a single day, the exposure is high. Between 1990 and 2015, the three Swedish cities increased their life expectancy in four and five years: scientists attribute a quarter of the profit to their cleanest airs.
The calculation is based on other previous models that have already studied the relationship between pollution and health, and controls for both the size of the population and its demographic structure.
The recipe. Until now, the cities had observed, with some alarm, how pollution levels increased. And its citizens had perceived its (negative) consequences. The example of Stockholm and company advances us future trends: as the policies of prevention and improvement of air quality advance, our health will improve. In a certain sense, the study is a look towards the global future of the big cities.
In the global framework, however, pollution is still the norm. Episodes like those in New Delhi (weeks without seeing the sun because of pollution) or those in the big Chinese cities (toxic clouds that cover the sky every morning) require large-scale and global policies. All large cities, of course, are already fighting the phenomenon. What can all continue to aim for is greater life expectancy for all.