Start Holding Your Breath: Unexpected Exposure to Second-Hand Smoking

A deep dive into the dangerous health consequences of secondhand smoke.

Reading Time: 5 minutes

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By Maheen Rahman

You’re walking to school one morning, trying to calm your panicked mind before the test you have to take first period. You take deep breaths in an attempt to de-stress, but instead of being greeted by fresh air, you inhale a giant whiff of cigarette smoke. Brushing this scent off is normalized for students because of the widespread use of tobacco, but the passive effects of exposing oneself to even the scent of tobacco can lead to major health effects. 

Secondhand smoking is when one breathes in smoke produced by another human’s cigarette. However, simply breathing in smoke is not enough to be considered secondhand smoking. To meet the criteria for secondhand smoking, there must be a concentration of five to 10 nanograms of cotinine per milliliter in one’s bloodstream. Cotinine is a drug encapsulated in tobacco, so if there is cotinine detected in someone’s blood, it can be assumed that tobacco is affecting their blood. It is used as a tracker, or marker, by scientists and researchers to record the concentration of tobacco in someone’s body. Unfortunately, more than 23 million—or about 35 percent—of children in the U.S. have been exposed to secondhand smoke and are considered secondhand smokers. A survey published in 2013 shows that more than a third of the adults in New York City from all different boroughs were secondhand smokers, a figure larger than the national average. Though this is lower than the numbers reported in a 2004 data report from the New York City Health Department—in which 57 percent of non-smokers in New York City had elevated levels of cotinine—one-third of the population still suffer from secondhand smoke. An experimental study conducted in 2006 by Amanda L. Blackford and many other scientists attempted to determine the cotinine levels of different cigarettes. Their research has shown that the average cotinine level in one cigarette is 12 nanograms per milliliter, so breathing in just a fraction of a cigarette's output could result in secondhand smoking effects. 

Smoke is defined as the products of burning materials made visible by the presence of small particles of carbon, especially carbon monoxide. When smoke is released and subsequently inhaled, this carbon monoxide enters the bloodstream. The dangers of carbon monoxide lie in the fact that it attaches to hemoglobin, a protein that transports oxygen in the bloodstream. Hemoglobin does this by attaching to oxygen, moving it throughout the bloodstream, and releasing it at core muscles and vital organs. Because carbon monoxide attaches to hemoglobin, the amount of hemoglobin available for oxygen decreases. This results in less oxygen circulating throughout the body, and body parts that require oxygen to function do not get the amount they need. Certain body parts, such as the liver and heart, require oxygen to function. This is because oxygen is necessary for the body to undergo cellular respiration, which is when organisms combine oxygen with glucose to create energy for the body, as well as water and carbon dioxide. Therefore, the higher one’s carbon monoxide intake is, the more difficulties they will have with circulating oxygen, which can lead to malfunctions in certain body parts that aren’t able to properly create energy.

Hemoglobin is not the only receptor that the chemicals from smoking interfere with. Carbon monoxide also attaches to receptors like myoglobin, a protein receptor similar in function to hemoglobin. Another example of a protein that carbon monoxide binds to is cytochrome oxidase, which is located in the inner mitochondrial membrane and helps transfer electrons from cytochrome C to oxygen. Cytochrome C is an enzyme involved in the electron transport chain of mitochondria, a series of protein channels that aid the process of cellular respiration. Cytochrome C is important for the electron transport chain because it carries electrons from one side of the complex of integral membrane proteins to the other. Without this process, electrons cannot properly be transferred in cellular respiration, and oxygen cannot be used to create energy. Because of this, without cytochrome oxidase, creating energy ranges from extremely slow to nearly impossible. Since carbon monoxide attaches itself to cytochrome oxidase, the cytochrome oxidase will not be able to aid cytochrome C in transferring electrons through the electron transport chain because it will be preoccupied. 

The dangers of secondhand smoking have been confirmed by a plethora of experiments. A 2021 study published in the Environmental Health Perspectives journal by Oregon Health & Science University laboratory lead researcher Jacob Raber investigated the effects of secondhand smoking through experiments conducted on mice. The researchers examined 62 mice over a period of 10 months, exposing them to smoke using a robot that smoked a pack of cigarettes a day. They split the mice up into two groups: a control group and a human tau group, consisting of mice that had been modified to express the human tau protein. This protein is linked to dementia in humans, so the second group was the “unhealthy” group of rats. The smoke exposure harmed both the male and female mice but had a bigger impact on the male mice. In addition, exposure to secondhand smoke resulted in rapid weight loss, but once again, male mice were impacted on a larger scale. Finally, researchers found that exposure to secondhand smoking affected the brains of mice. There were changes observed in their metabolic pathways, which are chemical reactions. Importantly, the researchers also found that the control group was more affected behaviorally and cognitively by secondhand smoke than the human tau protein mice. This signifies that even if one is initially healthy, the impacts of secondhand smoking do not discriminate.

This argument is further proven by the fact that secondhand smoke causes more than 7,300 lung cancer deaths each year among U.S. adults who do not smoke. Adults who are exposed to secondhand smoke have risks of lung cancer 20 to 30 percent higher than average. 

Being aware of the dangers of secondhand smoke, Stuyvesant students should take precautions to avoid inhaling smoke whenever possible. A good way for students to avoid secondhand smoke is to always bring a mask and wear it at locations where the concentration of smoke is known to be high. N95 masks are recommended and certified by the National Institute of Occupational Safety and Health to be effective in reducing smoke inhalation. Though small amounts of smoke inhalation each day may seem harmless, it increases cotinine levels and can lead to harmful health consequences.