The Long Answer

Thirdhand smoke is the chemical residue from tobacco smoke. It is also called “tobacco smoke residue” or “stale tobacco smoke.” The chemicals in thirdhand smoke are toxic to humans, especially children. It can linger for years in dust and on household surfaces. It can also become embedded in carpets, furniture, clothes, and building materials. It is difficult and expensive to remove.

Infants and young children are the most likely to be exposed to thirdhand smoke for these three reasons:

1. Time Spent Indoors

Infants and young children spend more time on average indoors than adults. Human activity surveys have shown that infants spend 90% of their time indoors at home. If their home environments are polluted with thirdhand smoke, infants are at a higher risk of exposure.

2. Child Behavior

Infants and young children explore their environment with their hands and bodies. Before they can walk, they move around by crawling along the floor, where they can touch polluted objects and pick up polluted dust and particles along the way. Their small size lets them fit into tight spaces where dust and particles might collect. Through crawling and exploring their environment, their hands, mouths, hair, clothes, and toys can collect thirdhand smoke. 

As part of exploring their environment, children and infants put many objects into their mouths: their own hands, toys, blankets, their parents’ fingers, a car seat strap, and more. Just about anything they discover goes into their mouths, including everyday objects parents may use to distract a child, such as a cell phone, car keys, or TV remote. 

If their environment contains surfaces, objects, or dust contaminated with toxic thirdhand smoke, the chemicals can enter their bodies through touching, inhaling, or swallowing them. 

3. Growth and Development

The respiratory systems of infants and young children are developing, and they breathe more times each minute than adults do. This increased respiratory rate means that in relation to their size, they can breathe in more thirdhand smoke than adults can. Their other organ systems are immature and growing too—this includes their skin. The skin of an infant or child is thinner than the skin of adults, meaning that their skin creates less of a barrier to keep thirdhand smoke chemicals from being absorbed into their bodies. Their immune systems are also developing, making them more vulnerable to the effects of tobacco pollutants than adults. A weakened immune system makes it more difficult to fend off infections.

Do you have more questions about the toxic legacy of tobacco smoke, how it affects human health, and what we can do about it? Learn more here.

Updated: March 2025

Sources:

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