NEW YORK, Jun 01 (Reuters Health) -- Fumes from car exhaust combine with natural plant-released gases to produce newly-discovered air contaminants, according to researchers.
"Such an atmospheric situation usually builds up from traffic emissions when there is a high amount of sunshine during the day," explain researchers led by Dr. Karlheinz Ballschmiter of the University of Ulm, in Ulm, Germany. The findings are published in the international edition of the European journal Angewandte Chemie.
The researchers explain that all plants, but especially oak trees, release compounds called isoprenes into the atmosphere. In fact, plants release more isoprene into the air than any other compound, with total global discharge estimated at over 450 million tons each year.
In their experiments, the German team attempted to determine the interaction of isoprenes with ozone and nitrogen oxide, two of the major components of urban 'smog.'
They found trace quantities of numerous types of nitrates and hydroxy nitrates in air samples taken from an oak-lined parking lot. These compounds are thought to form at night, and are probably most common in "areas of high pressure in temperate zones such as Europe... (or in) normal weather conditions in California," according to the authors. They believe that airborne quantities of nitrates and hydroxy nitrates reach "a maximum in summer."
The health risks, if any, of inhalation of these compounds remain unclear. But experts now believe that there are more smog components waiting to be identified.
SOURCE: Angewandte Chemie International Edition 1999:38:1634-1637.
