There’s a tendency in India to only worry about pollution when the smog gets so thick you can’t see through it. But lifelong exposure to high levels of particulate matter is slowly killing us—even when the pollution is invisible to the naked eye— and a new online tool reveals exactly how many years of our lives we stand to lose.

The Air Quality-Life Index (AQLI), created by the Energy Policy Institute at the University of Chicago, presents the effect of particulate matter on lifespans around the world, calculating how many life years could be saved if local governments met the World Health Organization’s (WHO) standards for air pollution, as well as their own national standards.

The AQLI is based on the results of a new study (pdf) of pollution and life expectancy near the Huai River in China, published this week in the Proceedings of the National Academy of Sciences. The study isolated the effect of air pollution on lifespans, revealing that an increase of 10 micrograms of PM10 (particulate matter that is 10 micrometers or less in diameter) per cubic meter of air (μg/m3) reduces life expectancy by 0.64 years.

The most dangerous particulate matter is PM2.5, which refers to fine particles with a diameter of 2.5 micrometers or less. The researchers calculated the human health impact of PM2.5 specifically, and found that a 10 μg/m3 increase leads to a 1.03 year reduction in life expectancy.

In India, that means that average life expectancy could increase by a full year if it met its own PM2.5 standard of 40 μg/m3 and four years if the government complied with WHO standards of 10 μg/m3. India’s hyper-populated cities, such as Delhi, which is often labelled as one of the most polluted places in the world, stand to benefit the most. In Delhi, people could live as much as nine years longer if India met WHO standards, and six years longer if it met its own standards. Similarly, people in Kolkata and Mumbai could live for around 3.5 years longer if India complied with WHO standards.

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