U.S. Department of Agriculture researchers say a five-year study using satellites and surface monitors found ozone levels above 50 parts per billion have caused damage to soybean crops in Iowa, Illinois and Indiana.
Ozone levels in most urban areas of the United States have declined with improvements in emission controls but they are still high enough to damage soybean, peanut, cotton, rice, tomato and other crops, a USDA release said Monday.
The problem is seen as a global one, as ozone levels are expected to rise in countries like India and China, where growing populations are able to afford more cars and more power plants are under construction.
There is also concern of rising ozone levels in developing countries that can least afford losses of staple crops like soybeans, rice and wheat.
The research, part of a USDA priority of responding to climate change, was published in the journal Atmospheric Environment.