I left Delhi late last week, where the particle pollution level measured early Wednesday at the US Embassy was roughly 40 times greater than that measured at a monitoring site near my home in New York City. The annual average PM2.5 levels in Delhi in recent years have been roughly 10 times the New York City average in 2015.
Delhi’s government has been responding to this latest crisis with emergency measures, such as the suspension of construction activities and temporary closure of a local power plant. Action by the national government has also been requested to control a major source of pollution—seasonal crop burning of crop waste far upwind of the city. But these are stopgap measures that alone will do little to address a serious problem associated with urbanization and economic development.
I was in Delhi attending an Indo-US workshop on air pollution research priorities. The sad irony of this air pollution emergency was not lost on me, nor on other workshop participants, though there was hopeful discussion that this crisis will help to accelerate actions to reverse and control rising pollution.
The recommendations of a steering committee convened by the Ministry of Health provide a useful road map for action. That report, and the successful US experience controlling air pollution, shows that air quality management must include cities but be coordinated at the national level—as well as be comprehensive and sustained. No single source of pollution is driving the problem, so actions in multiple sectors are needed to control emissions from fossil fuel burning power plants, vehicles (especially heavy duty diesel), industry, household solid fuel burning and crop waste and trash burning.
Pollution episodes in New York City and other American cities in the 1950s and 1960s cities likely rivaled those being felt in Delhi today. While air pollution is still a significant public health threat in New York City, the contrast between present day Delhi and New York City makes me thankful for the more than four decades of progress in the US since the passage of the Clean Air Act (CAA) in 1970. While the India context today is different than that of the US in the ‘70s, there are parallels that inform what is needed for cleaner air in Delhi’s future.
As is the case in Delhi, where seasonal upwind crop waste burning is adding pollutants to a mix of other sources like coal-fired power plants, vehicles, road dust and industry, multiple sources were involved in New York City’s historic pollution episodes. Some pollutants were local, such as trash burning, high sulfur heating fuels and vehicle emissions, but many were upwind of the city, like coal-fired power plants that continue to this day to pollute despite some emission controls.
With the CAA, a comprehensive national approach was initiated to address a problem caused by pollution that crosses state boundaries and pollution sources like motor vehicles that are sold and travel across the country. The federal system for managing air quality that was launched by the CAA had other features that contributed to its success: a rigorous, transparent process for scientific evidence review to set health-based pollution standards, standards for air pollution monitoring, enforcement of emission standards for vehicles and power plants, refineries and other large sources, and leveraging of federal control of transportation funding to ensure state compliance. With effective federal regulations, cities are left to address local sources of air pollution hot spots like high-sulfur heating oil, heavy-duty diesel vehicles and traffic congestion. Improved air quality since the passage of the CAA is today preventing hundreds of thousands of illnesses and deaths annually across the US.
Each year, more than six million people around the world die from breathing polluted air. Severe air pollution episodes, like that in Delhi or 1960s New York City, can help spur a response. But improving and maintaining air quality and preventing future crises requires comprehensive and sustained national and local action.