India's urban centres are experiencing a new air pollution health hazard - ozone - whose just two-hour exposure can trigger a lethal asthma attack, says a study conducted by Delhi-based Vallabhbhai Patel Chest Institute.In the last few years, ozone level has surged with increase in automobile and industrial emissions. Ozone is a complex chemical reaction of nitrogen oxide gases and volatile organic compounds, by-products of burning gasoline and coal, with oxygen when temperature hovers around 25 to 35 degrees Celsius.
"High ozone levels in Indian cities have been observed during afternoon and early evening hours," said Anumita Roy Chowdhury, executive director of Centre for Science and Environment.
"We have found the days when ozone levels are high in Delhi, we get larger number of patients with asthma attacks. The reason is that the ozone reduces lung function allowing allergens in air to cause asthma," SK Chhabra of the institute said at a seminar on Wednesday.
To link ozone with asthma attacks, the institute conducted the maiden study in the country and found that two hours of exposure was enough to trigger a lethal asthma attack. "We have photographs showing that in two hours of exposure to ozone, lungs turn pale," he said.
The study also found effect of ozone more on children than adults - a probable reason for increase in asthma incidence in children in the country.
Another interesting finding of the study was that ozone has adverse impact on human health even if it is below the government notified standard of 50 particles per million (ppm) for eight hours. "Even at 40 ppm it causes lung dysfunction," Chhabra said.
The reason for this was that the ambient air quality standard for ozone was based on studies done in west and not in India. "It shows that we should redraft our air quality standards based on domestic studies," Chowdhury said.
Sundeep Salvi, director of Pune-based foundation said lung function among Indians was poorest in the world. "The difference between us and Europeans is about 30%," he said.
They also found that inhaling the mosquito repellant was equal to about smoking 100 cigarettes and burning of two incense sticks release bad smoke equal to about 30 cigarettes.
RN Tandon, joint director with Indian Medical Association, said there is a reason to believe that pollution was causing increase in disease burden as smoking was on the fall. "More studies are needed to find the definite link," Vinod Raina of All India Institute of Medical Sciences.