New Study Shows that Thirdhand Smoke is 100 Times More Dilute than Secondhand Smoke

What may be the first investigation to actually measure the ambient levels of thirdhand smoke and compare them with levels of secondhand smoke, a new study published in the current issue of Tobacco Control reports that concentrations of particulate matter in thirdhand smoke were 100 times lower than in secondhand smoke, measured in the same room (see: Becquemin M. Third-hand smoking: indoor measurements of concentration and sizes of cigarette smoke particles after resuspension. Tobacco Control 2010; 19:347-348).

Here's what the study did:

"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: on the first day before and after the cigarettes were smoked (secondhand smoke) then 4 hours later, 24 hours later, before and after resuspension manoeuvres (thirdhand smoke)."

Here's what the study found:

"after cigarette smoking: the airborne particles ... concentration was divided by 100 in the first 4 hours and again by 100 in the following 24 hours. After resuspension, the concentration was multiplied by 100, going back to that observed 4 hours after smoking."

The study concludes: "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 Story

This study confirms that thirdhand smoke is a real phenomenon. Particles that deposit on surfaces during smoking can later become re-suspended in the air. Importantly, however, even under these conditions of extreme agitation of the deposited particles (wiping, shaking, and ventilator turbulence), the particulate concentration in the thirdhand smoke was two orders of magnitude lower than in the secondhand smoke.

This study confirms what I have been asserting repeatedly since the thirdhand smoke "scare" was initiated: yes, it's true that thirdhand smoke exists, but the levels of exposure are so low that there is no substantial health risk to anyone - other than to infants or those who are extremely sensitive to tobacco smoke - and even for those groups, the risks are small compared to the secondhand smoke. Thus, thirdhand smoke becomes a theoretical, but not a practical, health concern.

These data also appear to refute the claim by Action on Smoking and Health that smokers themselves pose a hazard to nonsmoking workers by bringing in particles deposited on their clothes that will later enter the air and exposes nonsmokers. The data clearly argue against policies that deny employment to smokers based on the potential health hazards of thirdhand smoke exposure among their fellow workers.

These data also appear to refute the assertion that thirdhand smoke is a substantial health concern in general. If people live in a home with smokers who smoke in the home, the secondhand smoke exposure will be so much higher than the thirdhand smoke exposure that it renders the effect of the thirdhand smoke essentially meaningless. And if the only exposure is thirdhand smoke due to the smoker smoking outside the home but bringing back particles on his or her hair and clothing, then there seems to be no concern at all about significant health effects.

This research should put the faddish focus on thirdhand smoke where it belongs: in the circular file. Unfortunately, the state of California is devoting millions of dollars to a research program that focuses on....

... you guess it.....

...thirdhand smoke.