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Much ado over small particles

^{Smoke from the chimney is one example of aerosol. Burning wood for heating purposes creates particulate matter emissions that have health effects. Photo: fitaloon / Flickr (Creative Commons).}

Aerosol, the small solid particles or liquid droplets floating in air, is a two-sided phenomena, at least. At the same time as the aerosols cool down the climate, which partly counteracts the warming induced by greenhouse gases, they also cause and worsen many health problems.

These are some of the aspects that the scientists raise up during the 6-day International Aerosol Conference (IAC) at the University of Helsinki on 29 August – 3 September.

One might be a bit confused when faced with the extensive programme of the conference. Especially one that beforehand thought that aerosol equals a can of spray.

“First we were worried about the acid rain, and when we got that quite sorted, we were worried about the ozone depletion, and now that the depletion is no longer out of hand, we are mostly concerned about the climate change,” clarifies professor Hanna Vehkamäki from the University of Helsinki’s Division of Atmospheric Sciences.

“The same thing that worsen the air quality can also cool down the climate,” the divisions atmospheric physicist Ilona Riipinen continues referring to the aerosol particles scattering the solar radiation directly or indirectly when functioning as cloud nucleus. Every cloud droplet is formed around an aerosol particle.

Problems of combustion

I attended a lecture by five scientists who study the particle emmisions from combustion and their health effects. During their 15 minute talks the scientists gave interesting insights to the problems with combustion. It was interesting to hear that the traditional wood-heated sauna stoves have significant health risks (and by that I don’t mean the risks involved with the World Sauna Championships), if we look at the particles that they emit to the atmosphere.

Particulate air pollution is one of the major public health concerns worldwide. Small scale wood combustion is a problem especially in Northern countries. By 2020, 20 % of the energy in the EU most come from renewable resources. This means that different combustion methods will become more and more common ways of heating.

The emissions from combustion should be now studied carefully in order to introduce measures to reduce the emissions. Something has been already done and a new EU directive to limit to emissions has been introduced. The directive does not concern, however, the sauna stoves.

The new researches reveal that how and with what kind of appliances the combustion is done is a significant factor. According to studies presented during the lecture, the particulate matter emissions from old long wood fired stoves (not to mention sauna stoves) and boilers are manifold compered to those from modern pellet and woodchip boilers.

This is explained by the different combustion conditions. Combustion with modern appliances is more complete. Recent research suggests that particles emitted from more complete combustion are less genotoxic and cytotoxic, meaning toxic to cells and their genetic material. It has also been discovered that small particle emissions correlate with gaseous emissions, such as emissions of carbon monoxide and organic gaseous compounds.

The problem with combustion is only one aspect in aerosol research. If you are interested to learn more, visit IAC 2010 website where you can find abstracts of all the researches presented during the conference.

Elisa Lautala works as web editor for University of Helsinki's Faculty of Science. Elisa likes all kinds of cultural events, good books, warm weather, and aqua-jogging.