Many occurrences of ‘sick building syndrome’ have been firmly attributed to (e.g.) poor ventilation, airborne bacteria continuously recycled in air conditioning or tobacco smoke, but many more have remained a complete mystery. Peter Wolkoff of the Copenhagen Institute (Denmark) found another potential culprit: chemicals so short-lived that they had escaped the detection systems scientists had set up.

Peter noted that volatile organic compounds (VOCs) which may cause no distress on their own at low levels could give rise to eye and airway irritation when combining for a short period with ozone. These common VOCs come from (e.g.) a popular lemon scent, chemicals in the carpets and linoleum, tobacco smoke, wood and pine scent. Ozone can come from (e.g.) photocopiers and outside air.

When mice breathed typical levels of ozone or alpha-pinene (a common VOC) separately there was a minimal effect. When the mice breathed a mixture of ozone and alpha-pinene after it had been left for a while, there was, again, a minimal effect. But, when the mice breathed a fresh mixture, after 30 minutes their breathing rate decreased an average 30%, indicating airway irritation.