A ‘New Era of Air Pollution’ in the Tropics Could Have a Huge Toll

A new study shows that air pollution in the tropics will lead to hundreds of thousands of preventable deaths if stronger regulations are not put in place.

The researchers at University College London found that 180,000 premature deaths in large tropical cities were caused by increased exposure to pollutants. It's alarming that nearly three-quarters of megacities, those with 10 million or more residents, are expected to be in the tropics by the end of the 21st century.

In many megacities, pollutants increased between 8 and 14 percent a year, which is three times as high as national or regional rates of increase. Most of the air pollution in tropical regions comes from industrial and residential sources.

The co-author of the study, an associate professor of geography at University College London, said the size of the trends surprised them.

The researchers used data collected by instruments on satellites from NASA and the European Space Agency to estimate concentrations of pollutants known to be harmful to humans. There are 46 tropical cities in Africa, the Middle East and Asia that are projected to have populations of 10 million or more by the year 2200.

They found yearly increases of up to 14 percent for nitrogen dioxide, up to 12 percent for ammonia, up to 11 percent for V.O.C.s and up to 8 percent for fine particulate matter. They were able to estimate how many premature deaths would be associated with the increases.

Nitrogen dioxide increased in 34 of the 46 cities from 2005 to the present. In Bangladesh, concentrations tripled, and in four other cities, concentrations more than doubled.

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Concentrations of pollutants decreased in many cities. Jakarta, Indonesia, saw a statistically significant improvement in air quality as a result of governmental policies.

Jakarta still has a severe air pollution problem, but the trends there pointed to how effective targeted policies could be at reducing pollution. The researchers noted that the city has emission standards for vehicles and saw a decrease in nitrogen dioxide. It doesn't have limits on burning land to clear it after a harvest, and it saw increased concentrations of ammonia, which is associated with such agricultural activities.

The researchers found that most of the increased pollution was driven by traffic and fuel burning, not by the burning of wood or other fuels. Other human activities cause more pollution.

The lead author of the study said in a statement that open burning has dominated air pollution in the tropics in the past.

The study doesn't answer the question of what activities are most responsible.

There is so much anthropogenic activity that takes place within a city that the driver of these trends is.

She said that it would be up to policymakers to determine the most effective and economically viable ways to reduce pollution.

Even when laws are enacted, their effects are not immediate because of the constant political challenges.

In their report, the researchers said that air pollution in tropical cities could cause disproportionate harm to health care systems in countries with weak or overburdened health care systems.

The health care systems in tropical countries are vulnerable to the looming health crisis supported by our exposure trends.