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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 burned 10 cigarettes in 30 minutes in a non-ventilated furnished room that was then kept closed. On the next day, for particle resuspension, we mobilised the dust on furniture, clothes and surfaces by wiping and shaking and created even more turbulence with a ventilator.
An impactor (ELPI) measured the particle sizes (between 0.28 μm and 10 μm) and concentration in the air, 60 cm above the floor:
Median diameter, concentration in number and mass of particles were respectively:
This showed that after cigarette smoking:
These quantitative data support the hypothesis of a resuspension from the cigarette smoke surface contamination. However, this airborne contamination through resuspension remains much lower (100 times) than that of secondhand smoke. The rest of the aerosol mass initially produced by cigarettes could be firmly attached either to surfaces, leading to ingestion hazards and dermal transfer or to household dust and be inhaled with it.3 4
This study is the first to investigate the hypothesised resuspension of deposited particles of tobacco smoke (‘thirdhand smoke’).
Competing interests: None.
Provenance and peer review: Not commissioned; externally peer reviewed.