You don’t smoke and you stay away from people who are smoking, thereby avoiding both firsthand and secondhand smoke. You should be 100% smoke-free, right? Wrong, according to a new study by researchers at California’s Lawrence Berkeley National Laboratory, which indicates the dangers of thirdhand smoke. Thirdhand smoke actually isn’t airborne, gaseous smoke at all, but rather the residue that’s left on clothing, room surfaces and dust after the visible smoke is long gone from the room.
According to Lara Gundel, one of the lead researchers behind the new study, thirdhand smoke contains tobacco-specific nitrosamine, a compound known to cause significant damage to human DNA. Gundel says this is the first study indicating the mutagenic properties of thirdhand smoke.
Chronic vs. Acute Thirdhand Smoke Exposure
During the study, Gundel and a team of researchers placed paper strips in specially designed “smoking rooms” in a controlled laboratory environment. The researchers divided the paper strips into two study groups, with one group being placed in the smoking room for about 20 minutes with no ventilation. The researchers referred to this scenario as “acute exposure” because it replicates the effects of an object, such as a scarf, being in a room with a person smoking a cigarette.
The other group of paper strips, designed to mimic the conditions of “chronic exposure”, were subjected to an almost 200-day stay in the smoking room, albeit with ventilation.
Following this stage of the study, the researchers isolated the chemicals collected by the paper strips and put them in the presence of cells. As expected, the paper strips in the chronic exposure group had higher chemical concentrations than the paper strips in the acute exposure group. The strips in the chronic exposure group also caused more extensive levels of damage to the DNA of the cells to which the chemicals were exposed.
Avoiding Thirdhand Smoke
Unfortunately, thirdhand smoke is extremely difficult to avoid, according to the researchers. For one, it can interact on a chemical level with airborne compounds in order to create new harmful compounds in addition to tobacco-specific nitrosamine.
In addition, places that have been exposed to smoke are extremely difficult to rid completely of thirdhand smoke. The researchers cited examples of people buying used cars that smell smoke-free, only to find days later that the smoke odor returns once deodorizers and masking perfumes have worn off. The problem is so persistent that even if walls inside a home are given a fresh coat of paint, thirdhand smoke compounds will eventually make their way through the paint and pose a danger to inhabitants once again.
Still, the researchers aren’t sure to what extent thirdhand smoke is dangerous to humans. They hope future studies will use blood samples to look at how compounds found in thirdhand smoke affect humans.
The Bottom Line
While firsthand and secondhand smoke are most dangerous, there’s an additional type – thirdhand smoke – that’s dangerous as well. Thirdhand smoke is the chemical residue left on surfaces after visible smoke has dissipated, and it may cause damage to human DNA, according to a new study.
The full text of the study can be found online in the medical journal Mutagenesis.
