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New tool picks out smoke-hazard in atmosphere

By Martin Leggett - 16 May 2011 19:1:0 GMT
New tool picks out smoke-hazard in atmosphere

Advances in technology for sniffing out low-levels of potentially hazardous chemicals have given scientists a new tool for probing the smoky byproducts of combustion. One compound in particular, isocyanic acid, is linked to cardiovascular disease, rheumatoid arthritis and cataracts - and has always been hard to measure.

But in this study, published in Proceedings of the National Academy of Sciences, scientists from the NOAA have successfully picked up its traces in the downwind air of wildfires and the urban pollution of Los Angeles smog, as well as in cigarette smoke.

The tool that has put HNCO (as isocyanic acid is known, from its chemical formula) onto the scientist's radar is a custom-built mass spectrometer - one that the team themselves put together. It can pick up concentrations of HNCO below the billionth per part level, which is the concentration often found outside of the laboratory in real-world situations.

HNCO is among one of suite of organic acids emitted from the burning of biomass, such as forest fires, cigarette smoke or cooking fires. The team calculated that the really harmful effects of HNCO kick in above 1 part per billion (ppbv). The eyes and lungs are especially vulnerable, as their moist membranes dissolve the acid. That can then lead onto inflammation, which may contribute towards cataract formation, or a greater risk of heart disease.

So tracking the concentrations of HNCO, and its health effects, is very important from a public health perspective. It was already known that very high levels are found in smoking cigarettes, but billions of people are also exposed to HNCO through the burning firewood for heating homes and cooking food. The team reckons that it is likely the acid's concentrations exceeds their calculated risk threshold, of 1 ppbv, for such poorly ventilated indoor fires.

The lead author of the paper, NOAA scientist Jim Roberts, said ''If these indoor fires release similar levels of isocyanic acid as the fires we studied in the laboratory, families could be exposed to high levels of the chemical.'' In contrast, the levels of HNCO found in air from the LA urban zone, as well as those downwind of a wildfire in Fourmile Canyon, near Boulder, were comparatively low.

But as the team points out, the health impacts of lower concentrations are still unknown. The fact that levels of HNCO are likely to rise - as global warming increases so will forest fires - makes this new instrument potentially useful for tracking how emissions of this pollutant evolve. It is expected that emissions will also increase from man-made sources, as equipment to strip nitrous oxides from car tailpipe fumes also produces HNCO. ''We may be facing a future of higher amounts of HNCO in the atmosphere,'' said Roberts. ''It is fortunate that now we can measure it.''