Rising surface ozone concentrations - which indicate presence of air pollution or smog - are damaging nearly $2 billion worth of U.S. soybean crops annually, according to a NASA study of satellite measurements.
The study, headed by NASA Langley Research Center in Hampton, Virginia, looked at five years of soybean yields, surface ozone and satellite measurements of troposphere ozone levels in Indiana, Illinois and Iowa.
These three states are some of the biggest soybean producers in the U.S. and had peak crop damage in the hundreds of millions - part of more than $2 billion nationwide, NASA said.
Jack Fishman, a research scientist at NASA Langley's Science Directorate, said modest increases in surface ozone result in crop growth being stunted.
Exhaust from vehicles, including farm equipment, is a known source of smog. Ground-level ozone is a pollutant made from reactions between sunlight and human-induced emissions - harmful to breathe and damaging to plants.
The severe heat of the Midwest each summer has combined with manmade emissions to create smog and increasingly higher levels of its primary component, surface ozone, over the past several decades, NASA said.
NASA said its study showed that satellite measurements can be used to study ozone across wider areas than ground-level monitors.