Fireworks that mark public leave the air pollutant ozone according to research conducted at the Jawaharlal Nehru University , in India. Ozone in the lower atmosphere works as a respiratory irritant, a greenhouse gas and a plant toxin. Its production from oxygen in this part of the atmosphere was previously thought to require sunlight or nitrogen oxides. But scientists have shown the ultraviolet light released by the burning of metal salts in fireworks can do the job too, resulting in surges in ozone, researchers concluded after monitoring ozone levels during the annual Diwali celebrations in Delhi ( ABC Science Online, July 10, 2001 ).