These days in New Delhi, white shirts stay a lot whiter after a long day outside than they did in the late 1990s. Back then, India was in the thick of rapid industrialization, and millions of cars were being introduced to the roads. The actual particles of air pollution - specifically particulate matter, the mix of airborne liquids and solids produced by industry, transportation, and household combustion - were larger, and thus more noticeable.
Fewer, too, are the days of burning eyes and noses, symptoms caused by the high sulfur content in the diesel that fueled India's urban bus fleet. By 2001, all buses were mandated to transition from diesel to compressed natural gas. Although a large proportion of India's overall vehicle fleet still runs on diesel, the sulfur content is lower.
"The air pollution has gotten much smarter," says Parthaa Bosu, Director of Clean Air Asia's India office. "It's no longer as visible and no longer stuck in your nose. Instead, it's landing directly in your lungs, getting you sick, and increasing your risks of cancer and other respiratory diseases. When you ask citizens if air pollution is a problem, you may hear that the air is clean."
Except India's air is a long way from clean. In January, a flurry of media stories suggested that New Delhi's air quality was worse than that of China's capital city, Beijing. In the 2014 Environmental Performance Index (EPI) - a biannual report released by Yale and Columbia universities - India ranked close to last alongside China on an indicator of exposure to fine particulate matter (PM2.5), which is small enough to enter the bloodstream.
India was dealt a further blow in May, when a World Health Organization (WHO) study assessing air pollution in cities ranked New Delhi below Beijing. The study said that New Delhi has "the world's worst air quality."
The Indian government initially dismissed the EPI and WHO air pollution findings. However, as it became clear to the international community that air pollution levels in New Delhi and other major cities in India far exceed thresholds deemed safe by both India's National Ambient Air Quality Standards and the WHO's Air Quality Guidelines, Indian pollution-control regulators changed their posture.
This fall, India's Central Pollution Control Board (CPCB) will publish its own air pollution index. The index will measure eight air pollutants in 16 Indian cities, ranking the cities based on their air quality.
Similar to air quality indices (AQIs) in the United States, Europe, and China, India's index is intended to convey air quality levels in a way that is accessible to the general public, clearly identifying health risks associated with the levels of any given air pollutant. The CPCB monitors and regulates the standard spectrum of air pollutants: PM2.5; its slightly larger and less dangerous counterpart PM10; nitrogen dioxide; sulphur dioxide; ozone; carbon monoxide; lead; ammonia; benzene; benzopyrene; nickel; and arsenic. Out of all of these, PM2.5, which the EPI and WHO studies both measure, is the most dangerous to human health.
"India's air quality index is a good step in informing the general public about the state of air quality, which will not only sensitize them toward this issue but will also make them think about ways to improve it," said Sumit Sharma, a fellow in the Earth Science and Climate Change Division of The Energy and Resources Institute (TERI).
"However, merely informing the public through an air quality index is not going to solve the problem. Air quality indices depend on the data collected through a network of monitoring stations. The network itself needs substantial improvement."
The index also aims to inform state governments in drafting their own air pollution policies, while providing feedback on the effectiveness of existing air pollution regulations.
CPCB confirmed that the index is under development, but declined to comment further.
Currently, India's National Ambient Air Quality Standards prescribe 40 micrograms per cubic meter (µg/m3) as an annual average for PM2.5, which is less stringent than WHO's interim targets and air quality guideline of 20 µg/m3. India's recommended levels would qualify as "unhealthy for sensitive groups" under the United States' Air Quality Index. For PM10 India's standards prescribe a 60 µg/m3 annual average. That is within range of WHO's suggested interim air quality targets, but still a long way from its air quality guideline of a 20 µg/m3 annual average.
"The health benefit you get going from 35 to 30 µg/m3 is lower than from 15 to 10 µg/m3," says Joshua Apte, a postdoctoral fellow at Lawrence Berkeley National Laboratory. Apte stresses the nonlinear relationship between air pollutant levels and health impacts - and the need for an index to reflect this.
"It's important to think about not just the short-term policies that can lead to 1 or 2 µg/m3 gains in a city but also the long-term vision for truly clean air," he says.
Slated for completion in October, India's air pollution index marks a positive move by the government to shed light on air quality in India's urban areas. By clearly communicating the health impacts of air pollution, the index could elevate the public profile of air quality and provide new momentum to improve India's air quality standards and regulations.
This post was co-authored with Daphne Yin, a Masters of Environmental Management (MEM) candidate at the Yale School of Forestry and Environmental Studies. She is also a Researcher at the Yale Center for Environmental Law & Policy.