Sure, we know that all too well. In 1964, the U.S. Surgeon General issued its famous report that connected smoking with major health risks and, in the 50 years since that report, smoking rates have fallen drastically around the world. Between 1980 and 2012, smoking prevalence in the U.S. dropped by 42% for women and 25% for men. Following that drop, fewer Americans today see smoking as a serious public health problem than they did a decade ago. Now, we're more concerned with obesity, drug abuse, and mental health.
But, when the smoke clears, it doesn't just go away — and there is growing evidence that tobacco smoked long ago, even by someone else, still poses serious risks to the human body.
We already know that secondhand smoke poses serious health risks. The Surgeon General reported in 2006 that living or working in a place where smoking is permitted can increase your chances of cardiovascular illness and lung cancer by up to 30%, while the CDC estimates that up to 46,000 nonsmokers die from secondhand smoke-related heart disease each year.
As if that weren't enough, now there's thirdhand smoke, or the residual chemicals left on surfaces in a formerly smoky environment. The concept isn't entirely new. The term itself was coined around 2006, when doctors became concerned that curious babies could be exposed to nicotine by crawling and touching things — which, as babies, they are wont to do — and nicotine in smoke readily sticks to nearby surfaces.
Scientists have known for years that the residue from cigarettes is dangerous; in 1953, researchers found that smoke condensate could cause cancer when applied to mice. But, it's not just old nicotine that's the problem. A study in 2010 found that residual nicotine in a smoker's car mingled with common indoor air pollutants to form new carcinogenic compounds. While the researchers in that study concluded that third-hand smoke posed a risk, especially to children and infants, they weren't entirely certain what specific effects it had on the human body.
Just last week, however, a team of scientists at University of California, Riverside published a study suggesting that third-hand smoke is just as dangerous as first-hand smoke. "We studied, on mice, the effects of third-hand smoke on several organ systems under conditions that simulated third-hand smoke exposure of humans," said Manuela Martins-Green, a professor of cell biology who led the study, in a statement to the University. "We found significant damage occurs in the liver and lung. Wounds in these mice took longer to heal." Martins-Green noted that in addition to posing behavioral and neurological problems in children, thirdhand smoke could also play a role in the development of type-2 diabetes, even in people who are not obese.
The problem is that thirdhand smoke is everywhere — in houses, cars, apartments, and hotel rooms, as well as on clothing — and persists for a very long time. One study found that smokers' former homes, even after they had been thoroughly cleaned and vacant for two months, still contained measurable amounts of thirdhand smoke in dust, on surfaces, and even on the new nonsmoking residents' fingers.
As alarmist as it sounds, the only way to minimize the risk of exposure to thirdhand smoke is to stay away from places that currently or recently allowed smoking. (Hotels with only partial smoking bans still expose guests to thirdhand smoke, one study found.) If you smoke yourself, there's never been a better time to quit.