Newly-detected chemical in smoke may have serious health implications, says study

Cigarette smoking, burning forests and even cooking fires all release a chemical — not previously known to exist in smoke in significant quantities — that may have potential health impacts, according to a new study by scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the NOAA Earth System Research Laboratories.

“The molecule has hardly been measured before — certainly not in the atmosphere,” said CIRES Fellow Joost de Gouw, coauthor of the new paper published in the journal Proceedings of the National Academy of Sciences May 16. “ So it was a complete surprise to find it in such large quantities.”

The chemical, isocyanic acid, is similar to methyl isocyanate — the gas that leaked from a pesticide plant in Bhopal, India, in 1984 killing more than 3,000 people within weeks.

De Gouw and his colleagues were first able to detect isocyanic acid when they developed a new instrument, a mass spectrometer designed to measure gaseous acids in the air. In the laboratory, they found biomass burning — burning of trees or plant material—produced levels of this molecule approaching 600 parts per billion by volume (ppbv).

“There is this molecule in smoke that we can now measure and it is there in significant quantities,” de Gouw said. “There are good reasons to believe that it can have significant health impacts.”

In the human body, isocyanic acid dissolves to form cyanate ions and the researchers found that the acid was very soluble at the pH level of human blood. This means it could potentially enter the bloodstream, de Gouw said. At exposure levels of isocyanic acid greater than 1ppbv, the cyanate ion is expected to be present at levels that can contribute to a variety of health problems such as cardiovascular disease, cataracts and rheumatoid arthritis.

Once the researchers discovered that fires produced the gas at the U.S. Forest Service Fire Sciences Laboratory in Missoula MT, they then took their instrumentation out of the lab to see whether smoke in a “real” environment also gave off this chemical. “We had a new tool to look around us and we just explored,” de Gouw said. “It was basically our chemical curiosity at work.”

Previous studies showed that burning coal produces isocyanic acid, and the researchers now discovered this chemical is also present in tobacco smoke and smoke from the combustion of other plant materials. In rural areas of developing countries where biofuels are used for cooking and heating, exposure levels of the acid could be harmful. But does a real, not a laboratory fire, give off the acid?

The team didn’t have to wait long to find out. Starting on Labor Day 2010, the Fourmile Canyon wildfire raged in the foothills above Boulder, CO, burning more than 6,000 sq. acres and destroying 169 homes. Scientists at the Boulder NOAA research facility wasted no time in learning what they could about the tragedy.

“Boulder has a world-class atmospheric chemistry building and only once in its lifetime is it going to have a full-on hit from a wild fire,” de Gouw said. “So just about everyone in that building turned on their instruments.”

The team’s spectrometer detected levels of the acid up to 200pptv in the air at the site, which was downwind from the fire. “So in Boulder we found that not only is it formed in a laboratory fire,” de Gouw said. “It also comes out of a real wild fire.”

One possibility was that the acid could be prevalent immediately in the vicinity of a fire but 20m from the flames the compound could be lost, de Gouw said. “But that didn’t happen,” he said. “We were miles away and it was still there.”

The researchers didn’t constrain their measurements to wildfires. They also used their equipment to find the levels of isocyanic acid in the urban environment of Los Angeles. “In LA we find, wait a minute, even when there are no fires there is a little of this acid,” de Gouw said. “So smoke may not be the only source of it in the atmosphere.”

More isocyanic acid was measured during the day, so sunlight could be sparking the chemical reactions that make it, de Gouw said. Another potential source in urban air could be emissions from diesel engines outfitted with the latest generation of pollution control equipment that is being introduced in California and Europe, he said.

“We know so little about isocyanic acid’s behavior in the atmosphere that we want to do a number of follow-up studies, “ de Gouw said. “We have some data in our paper but that is just the beginning and we need to do a lot more work.”

Other authors of the new paper, “Isocyanic acid in the atmosphere and its possible link to smoke related health effects,” are Jim Roberts, Patrick R. Veres, Anthony K. Cochran, Carsten Warneke, Ian R. Burling, Robert J. Yokelson, Brian Lerner, Jessica B. Gilman, William C. Kuster, and Ray Fall.

Contact: Katy Human, CIRES, 303-492-6289, kathleen.human@colorado.edu