Thirdhand smoke poses health danger, especially to children, scientists say

Cigarette smoke residue on household surfaces such as carpeting and furniture can damage DNA and potentially increase cancer risk, a new study has concluded.

The UC-funded study, conducted by a consortium of scientists led by a researcher in Northern California, is the first of its kind exploring the effect of so-called thirdhand smoke on the structure of DNA in human liver cells. It was presented Sunday at the American Chemical Society meeting in Dallas.

The research suggests that exposure to thirdhand smoke should be an item of concern, especially in households with young children.

Smoke deposits stay on surfaces, such as carpeting and furniture, for longer than previously thought – in some cases for weeks, said lead researcher Bo Hang, with Lawrence Berkeley National Laboratory.

In Sacramento County, where a 2010 California Student Tobacco Survey established that 35 percent of children live in a household with a smoker, the thirdhand smoke issue is no small matter.

Researchers looked at what happened when human cell cultures were exposed to compounds formed when thirdhand smoke interacted with chemicals present in a home environment or even cars. “We wanted to see what would happen in realistic scenarios and whether thirdhand smoke is at a level of concern, and whether it causes any damage. And the answer here is – yes,” said Hang.

Of greatest concern, he said, are secondary compounds formed when thirdhand smoke interacts with chemicals such as nitrous acid and ozone, which are found inside homes. Unvented appliances and car engines commonly emit nitrous acid.

That interaction forms a secondary compound called nitrosamines, Hang said. In some cases, they can be highly carcinogenic.

The research, funded by the University of California’s Tobacco-Related Disease Research Program, found that tobacco-induced nitrosamine causes DNA breakage. That breakage happens when one nitrosamine, called NNA, binds onto DNA in such a way that may allow cancer development to occur.

Unlike first- and secondhand smoke, thirdhand smoke persists in the environment. Secondary compounds in thirdhand smoke – such as nitrosamines – do not degrade rapidly and are stable, said Hang.

“It can last as long as a few months,” said Hang. “It will be there for a long time, because the residual chemicals tend to stick on the wall surfaces and also dust particles.”

That longevity creates a level of concern for households where children are present, said Kent Pinkerton, director of the Center for Health and the Environment at UC Davis. “If you go into a room a few days later where someone has been smoking, it will be clear of secondhand (smoke). But you still smell things. You’re smelling the off-gassing from the surfaces in the room.”

“Children may represent a very special group of individuals who may be very susceptible,” said Pinkerton. “They’re always touching surfaces and putting things into the mouth, and putting their hands up to their mouth.”

However, Pinkerton said firsthand smoke still poses a far greater health risk for smokers.

UC Davis pulmonary specialist Mike Schivo nonetheless said thirdhand smoke creates cause for deep concern. “Some clinical studies show that thirdhand smoke products are found in humans, and that there is evidence of thirdhand smoke detected on walls of rooms where people had smoked in a while ago,” said Schivo. “And thirdhand smoke has also been found in the urine of children.”

“We knew we could see nicotine products in people exposed to thirdhand smoke, but we didn’t have any evidence that it caused any damage – and this new study showed it does,” said Schivo.