In many cities, concentrations of some pollutants have decreased while others have increased. But Jakarta, Indonesia is the only one to have seen a statistically significant improvement in overall air quality as a result of government policies.
The improvement is relative as Jakarta still has a serious air pollution problem, but trends there have shown how effective targeted policies could be in reducing pollution. The city has emission standards for vehicles, the researchers noted, and found a decrease in nitrogen dioxide, which is associated with vehicle exhaust. But there are no limits on burning biomass, such as burning land to clear it after a harvest, and he found an increase in ammonia concentrations, which is associated with such agricultural activities.
Overall, however, the researchers found that most of the increase in pollution was not due to biomass burning, but to sources such as traffic and fuel burning – a distinction which the researchers were able to do because biomass burning appears in satellite observations in intense but relatively short bursts. , usually with a seasonal pattern. Other human activities produce less intense but more sustained pollution.
“In the past, open burning of biomass for land clearing and agricultural waste disposal has overwhelmingly dominated air pollution in the tropics,” said University College researcher Karn Vohra. of London and lead author of the study, in a statement. “Our analysis suggests we are entering a new era of air pollution in these cities, with some experiencing rates of degradation in a year that other cities experience in a decade.”
The study does not answer the question of which activities, in particular, are the most responsible.
“The driver of these trends is human activity, but that’s very broad – there’s so much human activity going on in a city,” Dr Marais said, adding that more scientific research is needed to identify the main contributors.
Then, she said, it would be up to policymakers to do cost-benefit analyzes and determine the most effective and economically viable ways to reduce pollution.