'Thirdhand Smoke' Especially Harmful For Asthma Sufferers

Components in cigarette smoke that linger long after the cigarette has been extinguished can pose their own health risks, especially for asthma sufferers, according to a new study.

"Thirdhand smoke" — the residue that can persist for months after a cigarette is put out — can react with pollutant ozone to form tiny, potentially harmful particles.

These "ultrafine" particles, less than 100 nanometers wide, can make their way deep into a person's lungs and could present a bigger threat to asthma sufferers than nicotine itself, said study researcher Mohamad Sleiman, a chemist at Lawrence Berkeley National Laboratory. (A nanometer is 1 billionth of a meter. The diameter of a human hair is about 80,000 nanometers.)

"Ultrafine particles have the capacity to carry and deposit potentially harmful organic chemicals deep into the lower respiratory tract," Sleiman said. "It’s been well established by others that the elderly and the very young are at greatest risk" from these types of particles.

Thirdhand smoke

The dangers of firsthand and secondhand tobacco smoke, which contain several thousand chemical toxins distributed as particles or gases, have been well documented. Then, in February, a study conducted by Sleiman and his colleagues revealed the potential health hazards of thirdhand smoke from cigarettes. It was shown to react with nitrous acid, a common indoor air pollutant, to produce dangerous carcinogens.

Until now, however, no studies have looked at the reaction of nicotine with ozone.

Released as a vapor by the burning of tobacco, nicotine is a strong and persistent adsorbent onto indoor surfaces that can be released back into the indoor air for a period of months after smoking has ceased. Ozone is a common urban pollutant that infiltrates from outdoor air through ventilation and has been linked to health problems, including asthma and respiratory ailments.

The researchers found that when nicotine reacts with ozone, some of the products place higher up on a scale of particles hazardous to asthma sufferers than nicotine itself, said study researcher Lara Gundel, also of Berkeley National Laboratory.

Backfiring purifiers

The findings suggest using air purifiers that emit ozone to clear out the smell of tobacco smoke may not be such a good idea.

The researchers caution that the levels of both ozone and nicotine in their study were at the high end of typical indoor conditions.

"In addition, we need to do further investigations to verify that the formation of ultrafine particles occurs under a range of real-world conditions," Sleiman said. "However, given the high levels of nicotine measured indoors when smoking takes place regularly and the significant yield of ultrafine particles formation in our study, our findings suggest [a] new link between asthma and exposure to secondhand and thirdhand smoke."

The study was published online in the July 29 journal Atmospheric Environment.