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Report - AS3.12 Atmospheric Chemistry and Indoor Pollution
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Topics covered by the session at the EGU included both the chemistry of indoor air and the associated health impacts. Much of the chemistry focused on the importance of the reactions of ozone and terpenes indoors, which are believed to drive much of the chemical processing therein. Ozone produced outdoors through photochemical reactions in the atmosphere can find its way inside buildings. Once indoors, the ozone can react with reactive carbon double-bonded species (e.g. terpenes) that are emitted from various indoor products, such as furnishing and building products, air fresheners, cleaning products, paints, plants, solvents and toiletries. As a result, ozone tends to be depleted on entering the indoor environment, as borne out by some of the data presented at the meeting.
It was also demonstrated at the meeting, that the reactions of ozone with some terpene species (particularly d-limonene) can lead to the formation of ultra-fine particles indoors, which themselves have been postulated to cause adverse health impacts. In addition, these particles represent a whole new range of oxygenated volatile and semi-volatile organic compounds (particularly hydroxylated, carbonyls, and acids and mixed species thereof).
Topics also covered semi-volatile organic compounds like PCBs and fungicides emitted from building materials. The focus on these substances reflects the concern that inhalation and ingestion of contaminated indoor dust may also have health implications.
A presentation of indoor measurements of HONO made in Cologne Cathedral showed that concentrations of up to 12 ppb were recorded in the dome area of the roof. Whilst it is likely that ground-level concentrations would have been much lower (as the HONO likely accumulated in the darkened, still, roof area), this observation demonstrated the impact of candle burning on a large scale indoors, with the HONO likely formed directly through candle combustion. There are believed to be health issues associated with HONO and its reaction products indoors.
One of the major issues with indoor air pollution research has been trying to relate specific chemical organic compounds to the reported health effects. The most common health and comfort effects reported in indoor environments are odour and sensory irritation in eyes and airways, components of the classic sick building syndrome. However, the adverse health effects appear not to be associated with the measurements of primary (those emitted directly) VOCs indoors, which have been the focus of many previous studies. Instead, it is becoming evident that we should be looking at a broader window of chemical species, like the secondary (those formed through subsequent chemical reactions rather than directly emitted) products of oxidation and the health impacts of these species.
As a result of the meeting, we have identified areas where we believe the European indoor air community should focus future research efforts. These recommendations are listed in a forthcoming editorial for the Indoor Air journal.
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