Third-hand smoking: indoor measurements of concentration and sizes of cigarette smoke particles after resuspension

In a previous study1 of ‘secondhand’ cigarette smoke, we showed that 75% of the particles added to indoor air were of ultrafine sizes and had a half-life in air of 18 minutes at 25°C. These particles after their deposition on household surfaces could be later put back in suspension and constitute a toxic ‘thirdhand’ smoke2 which has not, as yet, been documented through quantitative data. Consequently, we undertook direct measurements of the concentration and sizes of smoke particles after their deposition and resuspension in a closed room. A smoking device …