A new study has found that people who switched on re-circulation systems in their cars during their commutes in heavily polluted cities were exposed to around 80 percent less air pollution than those who drove with their car windows open.

Published in Science of The Total Environment, this global multi-city study was conducted by the Global Centre for Clean Air Research (GCARE) at the University of Surrey, and investigated air pollution exposure levels for commuters across ten cities: Chennai (India), Dhaka (Bangladesh), Guangzhou (China), Medellin (Colombia), Sao Paulo (Brazil), Cairo (Egypt), Sulaymaniyah (Iraq), Addis Ababa (Ethiopia), Blantyre (Malawi), and Dar-es-Salaam (Tanzania). The researchers measured how exposure to levels of air pollution varied during the commute, depending on whether the re-circulation systems were turned on, or fans were used, or the car windows were left open.

The results showed that irrespective of the city, or the car model used, leaving the windows rolled down exposed commuters to the highest amount of air pollution, followed, respectively, by fan-on and re-circulation. The extent of this exposure was found to be so vast that people who leave their car windows open are exposed to 80 percent more air pollution than those who turn on re-circulation. The study also found that exposure to air pollution was significantly higher during peak morning commute hours.

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“To be blunt, we need as many cars as possible off the road, or more green vehicles to reduce air pollution exposure. This is yet a distant dream in many ODA (Official Development Assistance) countries,” said Professor Prashant Kumar, Director of GCARE, who co-authored the study, adding: “Air-conditioned cars are unattainable for many poor and vulnerable commuters across the world.” And indeed, according to the WHO, above 90 percent of air pollution-related deaths do occur in low and middle income countries (LMICs) — mainly in Asia and Africa.

Air pollution kills an estimated seven million people worldwide every year, and nine out of 10 people worldwide are already breathing air that contains high levels of pollutants. In fact, the toxic air in India claimed 1.24 million lives in 2017. But, what makes the results of this study even more alarming for India is that nine out of the 10 most polluted cities in the world are right here in India. In addition, past studies have also linked air pollution to mental health problems like depression and anxiety, as well as to suicide rates.

But, this study is only one step towards understanding how people can make lifestyle changes to safeguard their health. “[It] can help commuters make decisions in their day-to-day lives to protect their health. Simple choices, like traveling during off-peak hours, can go a long way in reducing their exposure to air pollution,” Professor Abdus Salam from the University of Dhaka, who was also involved in the study, remarked.