• Carcinogens
• cotinine
• environmental tobacco smoke

The first time I had any inkling that nicotine might linger in a room was when I listened to a group of nicotine chemists complaining about how hard it is to keep nicotine out of their laboratories. Their gas chromatography and mass spectroscopy machines are expensive, complex and very sensitive. In order to detect nicotine and cotinine in samples from non-smokers exposed to secondhand smoke, they must scrupulously exclude nicotine and tobacco smoke from their laboratories. One chemist told a story of how experiments in his laboratory were ruined for weeks after new data cables were installed in the ceiling of the laboratory. Probable culprit: nicotine in the ceiling tiles and the dust above them, dating back 30 years to when people still smoked in laboratories at the university.

Thirdhand smoke is a new concept in the field of tobacco control. While everyone who has ever noticed the lingering smell of stale smoke knows that something stays around after the smoke clears, exactly what that something is, how long it stays and what it means for human health has been little studied to date.

The paper by Matt et al1 in this issue of Tobacco Control advances the study of thirdhand smoke by exploring one of the situations most likely to isolate thirdhand smoke exposure from concurrent exposure to secondhand smoke: rental housing. Their findings demonstrate that nicotine persists in homes previously occupied by smokers, and that non-smokers who move into these units have elevated levels of nicotine on their skin and in their bodies. The design of this experiment was very challenging; one can imagine approaching complete strangers who were in the middle of moving house and asking them to let researchers examine their homes and bodies, and the group is …