Is Thirdhand Smoke a Hidden Health Risk?

You probably already know that smoking is bad for you, and that even secondhand smoke is extremely dangerous. But what about thirdhand smoke? The term may be new to you, but chances are you — like most everyone else on the planet — have been exposed to it many times.

Pulmonologist Peter Mazzone, MD, MPH, Director of Cleveland Clinic’s Lung Cancer Screening Program, explains what thirdhand smoke is, the potential risks it poses for your health and what to do about it.

What is thirdhand smoke?

Thirdhand smoke (THS) is the residual — or leftover — nicotine and chemicals that remain long after someone smokes in the area. THS hangs around on:

• Clothing and bedding
• Furniture, upholstery and carpets
• Surfaces, like walls, ceilings and countertops
• Your skin and hair

The toxic residue from tobacco (or in the case of vaping, a chemical mist) can hang around for weeks, months or even years after the smoke clears.

“THS resists normal cleaning methods. You can’t air it out or vacuum it up,” says Dr. Mazzone.

The possible health effects of THS exposure are concerning. But Dr. Mazzone says “the specific risks of thirdhand smoke aren’t clear yet.” That’s, in part, because the concept is pretty new. The authors of a study in the medical journal Pediatrics coined the term “thirdhand smoke” in 2009.

The following year, researchers found that when residual nicotine in your environment reacts with nitrous acid (HNO₂) in the air, it forms carcinogens — compounds that can cause cancer.

“Although this suggests a dangerous connection, it doesn’t prove that thirdhand smoke is correlated with any other conditions,” Dr. Mazzone clarifies. “And that part will be very difficult to prove because we’re all exposed to it, no matter how hard we try to avoid it.”

How exposure happens

When you smoke in a room or car, toxic chemicals like nicotine cling to walls, clothing, upholstery and other surfaces, as well as to your body.

“Children are often the most vulnerable to thirdhand smoke because they’re exposed to surfaces like the floor, other people’s clothing and all sorts of household objects,” Dr. Mazzone reports.

This is particularly true for young children, who frequently touch objects and then put their hands in their mouths. This can increase their exposure to toxic chemicals.

Dr. Mazzone adds that adults who live with someone who smokes are also at a much higher risk for THS exposure.

Where it’s most common

You’re most likely to encounter THS in enclosed, shared spaces where people are either currently smoking or have smoked in the past. After all, it used to be common practice to have “smoking sections” in public places (including airplanes, if you can believe it).

Common THS hotspots include:

• Rental properties
• Hotels
• Restaurants
• Cars
• Old office buildings

Keep in mind that all smoke is dangerous, not just tobacco smoke. More and more research is coming out that shows similarly long-term negative health effects of smoke inhalation and damage after house fires and wildfires, for example.

Health risks that may be linked to thirdhand smoke

If someone asked you to make a list of lung cancer risk factors, first- and secondhand smoke would probably sit firmly at the top. Early research increasingly suggests thirdhand smoke exposure might belong on the list, too.

“There’s been an increased interest in thirdhand smoke in recent years because we’re seeing more lung cancer cases that aren’t related directly to firsthand or secondhand smoke,” Dr. Mazzone shares. “So, we’re looking at other causes for cancer aside from direct exposure.”

Lung cancer is just one of a range of medical conditions that early-stage research has associated with THS exposure. But none of these studies have established a causal link, meaning we don’t know for sure whether THS is actually causing lung cancer. But researchers are noticing a connection.

Possible health risks include:

• Cancer
• Lung conditions, like asthma and chronic obstructive pulmonary disorder (COPD)
• Heart disease and heart attacks
• Sudden infant death syndrome (SIDS)
• Developmental disabilities
• Mental health conditions
• Liver and other gastrointestinal disorders
• Neurological disorders

This list could easily be longer. Studies in 2013 and 2020 found that THS is genotoxic, meaning thirdhand smoke may cause damage and breaks in human DNA.

“More research is needed. But it seems clear that DNA damage is a real risk and can increase your chances of disease,” Dr. Mazzone says.

How to reduce or prevent exposure

You can’t avoid THS exposure completely, but you can take steps to reduce it. But it’s not easy — and for many, it isn’t affordable either. To get your home as close to THS-free as possible, you’d have to:

• Replace the carpets.
• Repaint the walls.
• Replace clothing.
• Have your car professionally cleaned and replace the air filters.
• Clean out or replace ventilation systems in the affected building.

Clearly, it’s expensive to completely rid a room of thirdhand smoke and eliminate the risk of exposure for future tenants or owners.

Dr. Mazzone stresses that the best solution for managing the dangers of thirdhand smoke is to stop smoking. If you live with someone who smokes, try to make sure they don’t do it inside. If they decide to kick the habit, encourage and support them.

“The best way to reduce exposure risk is to have a smoke-free environment, especially where you live,” he says. “It’s not just about cutting down, but quitting altogether.”

Dr. Mazzone concludes: “If you smoke, never smoke inside your house because even if you don’t smell the smoke anymore, it’s still there. The best and healthiest possible approach is to avoid smoking completely.”