By Sandy Hemphill, Contributing Writer, BabyMed


First-hand smoke is what the smoker inhales.  Second-hand smoke is what the smoker exhales or smoke from a smoldering tobacco product.  Third-hand smoke is the dust, tar, and other gunk from the smoke that settles on floors, toys, bottles, curtains, furniture, dust, and everything else in the room.  Third-hand smoke has been getting a lot of attention lately as more study of it reveals more and more biological threats caused by it.  One recent study found it raises the risk for type 2 diabetes, another that it damages the DNA in cells that will mature to be sperm cells, and a third found that infants and toddlers are at high risk of DNA damage that can cause cancer.

Third-hand Smoke and Type 2 Diabetes

This study from the University of California, Riverside, found that mice living in a cage polluted with third-hand smoke were more likely than mice living in clean cages to develop insulin resistance, which is an early symptom of type 2 diabetes.  When the mice in the polluted cages ate a mouse version of a diet that mimics the “Western diet” typical of what most people in the US eat rather than a healthy mouse diet, the risk of diabetes was even higher.

Oxidative stress, which causes inflammation, was found to be the trigger for insulin resistance because symptoms of insulin resistance reversed when the contaminated mice were treated with antioxidants.

Third-hand Smoke and Male Reproductive Health

This study, thought to be the first to test the effect of third-hand smoke exposure on male reproductive health, found metabolic function in contaminated male germ cells was altered in ways that might reduce fertility.  Male germ cells will mature to become sperm cells; female germ cells become eggs.  Any genetic damage that occurs in germ cells may be passed on to mature sperm and egg.  Such damage might result in infertility or it could jeopardize the health of a pregnancy or offspring.

Researchers from the US and China collaborated on this study, which also involved mouse cellular tissue.  The research revealed two separate mechanisms that damage male germ cells exposed to third-hand smoke.

Third-hand Smoke and Cancer

This study from the University of California, Berkeley, found specific chemical compounds in the solid residue from tobacco smoke that attaches to DNA strands and breaks them.  Breakage of DNA strands promotes uncontrolled cell growth, a hallmark of cancer.

The research team warns that DNA breakage may be especially dangerous for infants and small children who are naturally experiencing rapid cell growth as they themselves grow.

Infants, Toddlers, the Elderly, Family Pets

Long after smoking has stopped and the air cleared, third-hand smoke lingers on all surfaces.  Third-hand smoke residue stays where it lands until it gets cleaned up.

Infants and toddlers are most vulnerable to third-hand smoke exposure because of their rapid growth rate but also because they typically spend more time on the floor than older family members do.  They also put just about everything in their mouths, including their own toys, pacifiers, and teething rings that are exposed to third-hand smoke.  Food, bottles, and sippy cups all become contaminated in a smoky room, too.

The elderly are more vulnerable to third-hand smoke exposure because they are more susceptible to any disease.  Cells damaged by environmental pollutants are less likely to be repaired and new, healthy cells are being produced at a much slower rate than when younger.  Slowed cellular repair and slowed replacement makes disease development more likely.

Family pets may be at increased risk for cancer and other diseases caused by tobacco exposure because, like kids, they spend a significant amount of time on the floor.  Their bedding can also become contaminated when they sleep in areas where smoking occurs.

New Home, New Car

Dr. Manuela Martins-Green, professor of cell biology and neuroscience who led the study on third-hand smoke and diabetes risk, said 88 million US residents age 3 and older live in homes contaminated by second-hand and third-hand smoke.  Third-hand smoke lingers long after residents move out, making exposure risk high for the next occupants of the house, apartment, hotel room, or any other dwelling, even if the dwelling was vacant for months.  She recommends stripping a home of everything -- from ventilation and ductwork to flooring, furniture, appliances, paint, and window treatments -- to rid a new residence of a previous occupant’s third-hand smoke that has collected on surfaces.  

New cars that are actually used cars once owned or driven by smokers contribute the same risk of third-hand smoke exposure.  Rental vehicles and public transportation may harbor tobacco pollutants, too.



Adhami, Neema, Shelley R. Starck, Cristina Flores, and Manuela Martins-Green. "A Health Threat to Bystanders Living in the Homes of Smokers: How Smoke Toxins Deposited on Surfaces Can Cause Insulin Resistance." PLOS | One. PLOS, n.d. Web. 3 Mar. 2016.

Xu, Bo, et al. "Metabolomics reveals metabolic changes in male reproductive cells exposed to third-hand smoke." PMC. Scientific Reports / Nature Publishing Group, Macmillan Publishers Limited, 22 Oct. 2016. US National Library of Medicine / National Institutes of Health. Web. 3 Mar. 2016.

"Third-Hand Smoke Puts Infants, Toddlers at Risk for DNA Damage, Cancer." babyMed., 2014. Web. 3 Mar. 2016.