Thirdhand Smoke: Chemical dangers from past smoking

I bring bad news for smokers and nonsmokers alike. Smokers, you’ve been taxed to the max, banned in virtually every indoor space. You’ve been forced outdoors for your habit, into rain, cold, and heat … and now there might be more to come. Nonsmokers, you thought banning indoor smoking would protect you against tobacco’s many poisons. New research says you and millions of others thought wrong.



What is thirdhand smoke?

Breaking news: smoking outdoors can pollute the air indoors. And a habit already under fire for the health threats of firsthand and secondhand smoke is now in the hot seat for what’s called thirdhand smoke. These are the chemical byproducts of smoking that collect on clothes, furniture, walls, ceilings, and other surfaces. When inveterate smoker Uncle Jim gives you a hug, you’re touching and inhaling thirdhand smoke.

This is not visible smoke. It’s a heaping handful of the dangerous chemicals, including nicotine, that make firsthand and secondhand smoke the health threats that they are.

An empty room filled with surprises

A Drexel University research team set up shop in an empty classroom that saw its last cigarette put out some 20 to 25 years ago. They wanted to find out what happens when outdoor air particles, from car emissions or power plants, for example, find their way indoors, through ventilation systems and any other sources.

As they identified the various chemicals in the empty room, they kept finding some that didn’t originate outside. These turned out to be the chemical components of thirdhand smoke.

And they were all over the place—29 percent of the measured air volume in the room. That empty room was far from empty.

Drexel’s study leader, Peter DeCarlo, associate professor of environmental engineering and chemistry at Drexel, said “We didn’t expect this at all.”

Scientists love a surprise. It means new discoveries are there for the taking.

How the empty room became a smoke-filled room

De Carlo and his Drexel team tried to figure out how components of tobacco smoke could show up in a room no one had lit up in for 20 years. Where did they come from?

Hot on the trail of the truth, they launched a methodical sleuthing process, and learned three key facts:

  1. A balcony about 25 feet down the hall from the classroom they studied was a favorite place for smokers to sneak out and light up.
  2. Near the study classroom was office space where several smokers worked.
  3. That smoke-filled classroom room was on the same HVAC system as the studied classroom.

Voila. 1 plus 2 plus 3 equals hypothesis: that the thirdhand smoke from these nearby smokers made its way into the classroom via the HVAC system—and stuck to surfaces there.

Scientists already knew that nicotine levels in walls and furniture can persist for years, essentially lying dormant. The Drexel study showed that thirdhand smoke particles can “wake up” and travel around the room.

The thought of a million nicotine molecules swirling around my head when I’m in a room once filled with smoke is unsettling, to say the least.

The smoking gun

So it’s accepted that smoke particles can become airborne and travel through a building’s ventilation system. The thirdhand smoke compounds hijack airborne particles and fly with them wherever the HVAC system carries them.

On that journey, they come into contact with this or that chemical—ammonia from people’s breath or skin, cleaning products —and turn from a solid back into the gaseous state that lets them fly.

Is this a big deal? Aren’t we just talking molecules?

Thirdhand smoke is a relatively recent matter of concern, without much data to guide us to new hypotheses.

But we can conclude that you may be unwittingly exposed to thirdhand smoke wherever smokers are or were present, even if decades ago. “That Uber car you jump into, the hotel room you stay in, even a classroom where smoking hasn’t been allowed for decades,” says DeCarlo, “These are places where you are often exposed to a lot more than you expect.”

So we may be talking about molecules of thirdhand smoke versus lungs full of in-your-face firsthand smoke. But exposure time to that smoke is governed by the time the smoker is in the room—usually a matter of minutes.

Thirdhand smoke particles, by contrast, are there to be inhaled or touched, day and night, for a long time. Therein lies the potential health threat.

Not looking good for anyone

As I mentioned, there’s not a lot of health data on thirdhand smoke. What there is sounds pretty ominous.

One study published this year showed thirdhand smoke increased risk of lung cancer in mice. Another study published last year showed an increased risk of liver damage and diabetes in mice. A third study published this year focused on casinos and showed that six months after smoking was banned, heavy smoke residue remained on the walls and carpet.

A canary in the coalmine moment? Let’s hope not. Woe be the day when we all have to wear surgical masks and rubber gloves indoors and out. And when smokers are confined to ventilated cages, already happening in many airports around the world.

So what should you do?

This is a tough one. Given how widespread smoking has been over the years, it’s hard to imagine an indoor space that’s not crawling with thirdhand smoke.

If you can, avoid spaces where once there were smokers. That might be your Uncle Jim’s house.

If your own home was once occupied by smokers, clean your hard surfaces, fabrics, and upholstery regularly. If you have air conditioning, clean the filter regularly. There’s no other way to get rid of it—not by airing out rooms, not by opening windows, using fans or air conditioners, or allowing smoking in only parts of your home.

If you regularly frequent a place likely to have thirdhand smoke—an office, for example, a theater or a museum, make sure management is aware of the problem and will take remedial and preventive actions.

If you or anyone you know still smokes…what can I say? Quit! And urge others to do the same! Smokers already have a bad reputation for harming themselves and others. Try to make up for it by not contributing even more.

Build your defenses against thirdhand smoke by upping your antioxidant intake. Firsthand and secondhand smoke are proven to cause major free radical damage. It’s only a matter of time until research proves thirdhand smoke does the same. A good multivitamin can add another protective layer.

Finally, take advantage of the healing and preventive powers of healthy sleep, exercise, and a good diet—lots of healthy oils, fresh fruits and veggies.

Take good care.

Last Updated: August 22, 2019
Originally Published: August 28, 2018