India, one of the most polluted countries in the world, does not have a standard for many harmful chemicals and gases, and thus has no way to monitor or regulate them, the report said.
The study by the Community Environmental Monitors, or CEM, an independent environmental and health agency, is India's first comprehensive national survey of ambient air. The group based its findings on a two-year survey carried out in 13 locations around the country.
The study found that millions of Indians in cities and villages were exposed to at least 45 dangerous chemicals, including 13 carcinogens, some of which were present at levels 32,000 times higher than globally accepted standards.
Last month, the World Bank said pollution was growing rapidly in India and China because of inefficient investment in energy.
India is mainly dependent on coal for its energy, but it has about 15 nuclear power plants and is under pressure to increase energy production to meet a furious pace of industrialization.