The Indian capital of New Delhi recently passed Beijing, China, for having the world's most polluted air. Now, Indian Prime Minister Narendra Modi is launching a national air quality index to monitor pollution levels in 10 of the country's major cities.

Mr. Modi launched the air quality index at a two-day conference that included the environment and forest ministers from all Indian states. Officials at the conference are considering measures to strengthen environmental laws. Over the next two years, the index will be expanded to about 66 cities with a population of more than one million.

The new air pollution index will measure eight pollutants. The index will use color coding to describe the air's impact on human health. That will make it easy for citizens in big cities like New Delhi, Bangalore and Chennai to know their city's air quality.

Prime Minister Modi said in launching the index that the country must change the world's opinion that India does not care about the environment or about climate change.

Mr. Modi said that India has a long tradition of respecting the environment and can show the rest of the world the way in fighting climate change. He also urged Indians to reduce waste and save resources as they become more wealthy.

The high levels of air pollution in Indian cities are a major concern for residents. The World Health Organization says that 13 of the world's 20 most polluted cities are in India. The worst is Delhi, the densely populated capital territory of India. Indian officials do not agree with the WHO's findings. However, experts say that the pollutants in Delhi's air in winter months can reach up to three times the safe limits on some days.

Fumes from diesel vehicles have caused the increasingly polluted air of India's cities. Officials also blame smoke and dust from industrial and building activity.

Doctors have warned that rising levels of air pollution are leading to an increased number of citizens with asthma, chronic bronchitis and lung cancer. WHO officials call air pollution a leading cause of premature, or early, death in India. About 620,000 people die of pollution-related diseases every year.

Anumita Roychowdhury leads the air pollution program at New Delhi's Center for Science and Environment. She calls the launch of the index a good first step in fighting the severe problem. She says the next step should be for city governments to release public health warnings. She also says city officials should plan what to do on days when pollution levels are unsafe.

Ms. Roychowdhury also says the new index could make it easier for governments to demand difficult measures, such as restrictions on private vehicles.

I'm Ashley Thompson.