Breathing isn’t the only way that chemicals in cigarette smoke can enter the body. A new study shows that nicotine, a toxic chemical, can pass through skin and into the blood from the air or from smoky clothes.
Scientists refer to the airborne particles exhaled by a smoker as “secondhand” smoke. That’s because this smoke has already exposed the smoker and is now available to pollute the room and anyone in it. Those particles can linger for hours. “The way we are exposed to secondhand smoking is not as simple as we had thought,” says Gabriel Bekö. A civil engineer at the Technical University of Denmark in Lyngby, he led the new study.
The new findings are especially important for kids and teens, Bekö’s group says. After all, nicotine can affect their brains. So, “If you’re in a room where smoking or vaping is occurring, you’re taking in the smoke through your skin as well as your lungs,” says Charles Weschler. He’s a chemist at Rutgers University in Piscataway, N.J. A co-author on the new study, Weschler has spent many years studying the chemicals that pollute indoor air and how they get there.
It’s no surprise that tobacco’s nicotine can pass through the skin. Farm workers can get sick if too much nicotine rubs onto them from tobacco leaves. And nicotine patches have been designed to deliver the chemical dermally — through the skin. There, the goal is to help people get their fix of this addictive stimulant as they attempt to quit smoking.
But keeping skin exposures to nicotine low is important. This chemical is toxic. It has been used as a pesticide. It also can sicken — even kill — people if they are exposed to too much (such as if liquid nicotine spills onto their skin).
Against this backdrop, Weschler, Bekö and their colleagues in Denmark and Germany wanted to test whether nicotine from secondhand smoke could enter skin from a room’s air. And it can, their new data show. The study was published August 24 in Indoor Air.
“What’s new here is that the researchers have now shown that a meaningful uptake of nicotine is possible from dermal exposure to secondhand smoke,” says Frederick Frasch. He’s a scientist at the National Institute for Occupational Safety and Health in Morgantown, W.V. He specializes in studying skin exposures to chemicals. He was not involved in the new study.
The dose was not trivial
For the new tests, two nonsmoking researchers spent three hours in a closed room filled with tobacco smoke. The amount to which these men were exposed was similar to what might be found in a very smoky bar or nightclub. But it was higher than what would be found in most smokers’ homes, Weschler adds.
The men wore only shorts. This kept plenty of bare skin exposed to the smoke. And throughout the test, the men breathed clean air that was pumped to their faces through enclosed hoods. Those hoods meant any nicotine that entered their body must have come from something other than breathing.
Nicotine begins to break down once it reaches the blood. The breakdown chemicals exit the body in urine. Urine from the two researchers showed a spike in markers of nicotine exposure — those breakdown chemicals.
The men who took part had absorbed about 570 micrograms of nicotine through their skin, the data showed. That’s as much nicotine as would be picked up by smoking between 0.5 and 6 cigarettes. It’s also about as much nicotine as a person could expect to inhale in a really smoky room, says Bekö.
The researchers also wanted to find out what role clothes might play in someone’s exposure. So they hung a tee shirt for five days in a room where cigarettes had been smoked. Afterward, one nonsmoking researcher wore that shirt.
Nicotine breakdown chemicals showed up in his urine too. The scientists found that he had four times more nicotine in his blood after wearing the smoke-exposed shirt than when he wore a clean shirt.
What to make of the new findings
These data show that “nicotine is a sticky molecule,” observes William Nazaroff. So even hours after any smoking has stopped, he notes, “You can still be exposed to some of the harmful products of smoking.” Nazaroff studies pollutants in indoor air at the University of California, Berkeley. He did not take part in the new research.
It’s too soon to draw any firm conclusions from one small study, he says. More research is needed to better understand how nicotine moves through the skin. It may not move at the same rate in people with different skin types or ages. This study, for instance, looked at only three men. All were between the ages of 35 and 67. Future studies should look at women and young adults too, he says.
Future studies also could test for meaningful nicotine uptake in less smoky conditions, ones that would model the air in the house of a light or moderate smoker, says Frasch.
Last year, Weschler and Bekö showed that chemicals emitted from plastics and common household products can seep from the air through our skin. Taken together, Nazaroff says, these studies are challenging the way scientists have long thought about skin exposures to chemicals.
“We always thought you needed to touch a surface for a chemical to stick to the skin. What these new studies show is that for some chemicals you don’t need that physical contact,” he says. “They can be taken up directly from the air.”
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addiction (adj. addictive) The uncontrolled use of a habit-forming drug or uncontrolled and unhealthy habit (such as video game playing or phone texting). It results from an illness triggered by brain changes that occur after using some drugs or engaging in some extremely pleasurable activities. People with an addiction will feel a compelling need to use a drug (which can be alcohol, the nicotine in tobacco, a prescription drug or an illegal chemical such as cocaine or heroin), even when the user knows that doing so risks severe health or legal consequences. (For instance, even though 35 million Americans try to quit smoking each year, fewer than 15 out of 100 succeed. Most begin smoking again within a week, according to the National Institute on Drug Abuse.)
chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.
civil engineer An engineer who creates buildings, tunnels, water systems and other large projects that improve everyday life.
marker (in biomedicine) The presence of some substance that usually can only be present because it signals some disease, pollutant or event (such as the attachment of some stain or molecular flag). As such, this substance will serve as a sign — or marker — of that related thing.
model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
nicotine A colorless, oily chemical produced in tobacco and certain other plants. It creates the ‘buzz’ effect associated with smoking. It also is highly addictive, making it hard for smokers to give us their use of cigarettes. The chemical is also a poison, sometimes used as a pesticide to kill insects and even some invasive snakes or frogs.
particle A minute amount of something.
pesticide A chemical or mix of compounds used to kill insects, rodents or other organisms harmful to cultivated plants, pet or livestock, or unwanted organisms that infest homes, offices, farm buildings and other protected structures.
plastic Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.
pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.
secondhand smoke The gas and smoke particles emitted out of the burning end of a cigarette and exhaled by smokers. This pollution can be toxic and hand into the air (where it is available to be breathed in) for hours. Government scientists report that this secondhand smoke may contain up to 7,000 different chemicals, including hundreds that may be toxic (70 of which can cause cancer). According to the U.S. Centers for Disease Control and Prevention, since 1964, some 2.5 million nonsmokers have died from exposure to secondhand smoke.
smoke Plumes of microscopic particles that float in the air. They can be comprised of anything very small. But the best known types are pollutants created by the incomplete burning of oil, wood and other carbon-based materials.
stimulant Something that triggers an action. (in medicine) Drugs that can stimulate the brain, triggering a feeling of more energy and alertness. Caffeine is a mild stimulant that for a short while enhances alertness and helps fight drowsiness. Other stimulants, including some dangerous illegal drugs — such as cocaine — have stronger or longer-lasting effects.
tobacco A plant cultivated for its leaves. Dried tobacco leaves are burned in cigars, cigarettes, and pipes. Tobacco leaves are also sometimes chewed. The main constituent of tobacco leaves is nicotine.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
vaping (v. to vape) A slang term for the use of e-cigarettes because these devices emit vapor, not smoke. People who do this are referred to as vapers.
vapors Fumes released when a liquid transforms to a gas, usually as a result of heating.