Tox Tuesday: Nicotine and the world of e-cigarettes

March 01, 2016

It has become a very ordinary occurrence to see people going about their daily lives while puffing on an electronic cigarette, or e-cigarette, and leaving behind clouds of near-odorless fog in their wake. When compared to traditional cigarettes, these devices do not contain tobacco and therefore have been marketed as “less addictive” or “less harmful” to human health. However, studies have been showing these claims may not necessarily be true as nicotine and other harmful chemicals are still widely abundant in these products.

A recent article explains that a typical battery-operated e-cigarette contains a cartridge of e-cig liquid, or juice, which usually contains nicotine and the chemical propylene glycol. The e-cig juices come in an array of flavors, such as cola and watermelon and when used, the battery inside the e-cig powers an atomizer that vaporizes the liquid in the cartridge for the user to inhale.

The amount of nicotine in e-cigarettes varies from flavor to flavor, from zero to about 72 milligrams per milliliter of liquid. A traditional cigarette has about 10 to 15 milligrams of nicotine, and in both types of cigarettes, is a large part of their addictive nature.

“Nicotine has short-term negative health effects, like increasing your heart rate and blood pressure, so it can aggravate heart conditions,” Marvin M. Lipman, Consumer Reports’ chief medical adviser said in the article. “It also interferes with fetal development, making it unsafe in pregnancy regardless of its source.”

Nicotine can reach the brain within seven seconds of puffing on an e-cigarette and affects the area of the brain responsible for emotions and controlling impulses, known as the prefrontal cortex. This is especially true for young people, another article explains, as this part of the brain does not finish developing until about age 25.

The article goes on to explain that nicotine acts like a key to unlock special receptor molecules on the outside of cells in the brain, including those in the prefrontal cortex. Nicotine causes these cells to release signaling molecules, such as dopamine. These chemical signals travel across a gap between nerve cells (called a synapse). When they reach the neighboring nerve cell, they release their “message” and are responsible for the users “feel-good high.” But after repeated exposure to nicotine, those brain cells can change, and their ability to release their own, natural pleasure-giving chemicals, is greatly reduced.

Meanwhile, the brains of teens who smoke or vape may create more receptors to handle the flood of nicotine they have come to expect. As the number of receptors increases, teens will need more nicotine to get the same high. That makes nicotine users seek hit after hit. In teens, this can provoke side effects including making it hard for them to stay focused. It might also trigger bouts of depression or anxiety, the article states.

Some of the negative effects of nicotine on the young brain will fade with time — if exposure ends. Others, however, may persist. For instance, brain scientists at VU University Amsterdam found that exposing adolescent rats to nicotine increased their impulsive behavior and made them more reckless than usual. It also made it harder for them to focus their attention — even later, as adults.

While no one is sure that the same thing happens in humans, it’s still a large concern, said Garry Sigman, who heads adolescent medicine at the Loyola University Chicago Stritch School of Medicine. Exposing the developing adolescent brain to nicotine “could lead to a high risk of lifelong addiction.”

This point is supported by another study that has confirmed teens who first trying vaping are more likely to end up smoking traditional cigarettes, and also suggests that vaping may encourage smoking by even those teens who would have seemed the least likely to have taken up the habit.

For this study, researchers surveyed more than 2,200 ninth and tenth grade students in Hawaii. They asked whether, and how often, a student had vaped or had smoked cigarettes. They also asked about the students' relationships with their parents and some questions probed how much the kids liked to take risks.

One year later, the scientists surveyed these students again. The researchers then compared the teens’ answers and found that those who said in the first survey that they had vaped were nearly three times as likely as the non-vapers to have begun smoking over the next year.

The article explains that some people might think that those teens who moved from vaping to smoking were likely to have done so anyway. To test this idea, the researchers looked at one big factor that predicts whether teens will start smoking: personality.

Studies have shown that rebellious teens who don’t have a close relationship with their parents are all more likely to take up cigarettes. Those same traits aren’t as strongly linked to vaping. Why? Because vaping is not seen as dangerous so even students who are not rebellious or risk takers often try vaping. And many of these teens — who would otherwise have been at low risk of smoking — later moved on to real cigarettes, the research found.

The main reason e-cigarettes are not seen as being as dangerous as traditional cigarettes is because they do not contain tobacco, and therefore, do not produce the tar that clogs the lungs, or carbon monoxide, which is linked to heart disease.

“If a patient switches from smoking two packs a day to only using e-cigs, it’s not as good as quitting, but it’s undeniably better,” Douglas Kamerow, a former assistant surgeon general and a professor of family medicine at Georgetown University, said to the Washington Post. “But if a nonsmoker starts vaping and gets hooked on nicotine, especially if it leads to tobacco smoking, that’s a problem.”

If used as a means to totally wean people off of tobacco products, then e-cigarettes might have value, said Ilona Jaspers of the University of North Carolina at Chapel Hill, agreed. However, a recent clinical trial found no real difference between e-cigs and nicotine patches in helping people stop smoking: Neither were very effective. In addition, last fall, the U.S. Preventive Services Task Force said the evidence was insufficient to recommend e-cigs as a smoking-cessation device.

Other research shows that not only does vaping fail to not eliminate risks associated with conventional smoking, it may actually be introducing new ones.

Jasper and other researchers recently performed a study in which they examined cells from the noses of non-smokers, those who smoke traditional cigarettes, and those who smoke e-cigarettes. The researchers measured the activity levels in the cells of 594 genes associated with the body’s ability to fight infections. Among smokers, the activity of 53 genes was substantially diminished, compared with people who neither smoked nor vaped. Among vapers, those same 53 genes showed significantly diminished activity, Jaspers reported, as did 305 more.

The normal role of these genes would suggest that the lung tissue as well as nasal tissue of smokers — and especially vapers — “may be more susceptible to any kind of infection,” Jaspers concluded.

To test that possibility, Jaspers’ team collected immune cells from healthy human volunteers, then exposed them to flavored liquids used in e-cigarettes. Tested cells included blood neutrophils and lung macrophages, both normally tasked with gobbling up and killing bacteria. Some of the liquids proved disturbingly effective at suppressing the ability of those immune cells to do their job.

Furthermore, scientists have also found several dangerous aspects relating to the propylene glycol and other chemical compounds found in e-cig liquid. When propylene glycol is heated, for example, it can degrade into formaldehyde, a chemical linked to nose and eye irritation, and an increased risk of asthma and cancer. The Center for Environmental Health recently tested 97 e-cig products and found formaldehyde and the chemical acetaldehyde in more than half of them.

E-cig vapor can also contain lead, cadmium, nickel, tin and other metals, which can cause nervous-system or respiratory problems. So while the problems associated with tobacco may be eliminated in e-cigarettes, those that arise from the exposure of nicotine and other chemicals are abundantly clear.

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Category: Toxicology