Are All Electronic Cigarettes the Same? What Determines the Release of Potentially Harmful Chemicals?

Earlier studies suggested electronic cigarettes (e-cigarettes) can emit harmful compounds. A newly reported study examined their source and influencing factors. Device age and type, puff count and particularly the combustion temperature of tobacco or liquid nicotine affect emission levels. The study also concerns manufacturers and regulators seeking to minimize the health harms of these increasingly popular devices.

Smoking is a leading preventable cause of death worldwide, causing over 400 thousand deaths annually in America alone. Reducing tobacco use is therefore central to healthy living. Whether alternative tobacco products are a sensible choice has become a popular debate.

Conventional e-cigarettes generally have 3 main components: a battery, a liquid-containing cartridge and an atomizer. They use e-liquid containing nicotine, various flavorings, propylene glycol, glycerin and other ingredients. It heats when users inhale.

Other e-cigarettes, called “reduced-risk tobacco products”, contain no liquid nicotine and use special electronic devices to burn ordinary tobacco at lower temperatures, replacing 750 °C with 350 °C.

According to the United States Centers for Disease Control and Prevention (CDC), %3,7 of American adults, more than 9 million, regularly use e-cigarettes. Although varying by country, their average market share is approximately %5-7.

Because e-cigarettes do not burn tobacco or burn it at lower temperatures, they appear safer and less harmful. However, because of nicotine and other potentially harmful chemicals, the health effects of exposure remain uncertain.

The study in Environmental Science & Technology found heat-related breakdown in 2 solvents in vaporized e-liquid: propylene glycol and glycerin. These lead to harmful chemicals such as acrolein and formaldehyde.

The corresponding author and team simulated smoking with 2 device types, single-coil and more expensive double-coil, and 3 e-liquids. They demonstrated a relationship between increasing temperature and emissions, examining the device from the first puff through warming to a steady state to determine vapor composition.

The simulator took a puff every 30 seconds lasting 5 seconds. Vapor temperature rose rapidly during the first 5-10 minutes and stabilized around 20 puffs.

Emissions increased as much as 10-fold between the first puff and steady state in some devices. In a single-coil e-cigarette operating at 3.8 volts, the first 5 puffs emitted 0,46 micrograms of acrolein per puff, rising to 8,7 micrograms at steady state. Double-coil devices at the same voltage emitted less.

Device-aging tests used 50 puffs, repeated 9 times without cleaning. All carcinogenic or respiratory-irritating substances, including formaldehyde, acetaldehyde and acrolein, increased with use. In these 9 cycles, aldehydes rose strikingly by %60. Residue on or near the coil may provide a secondary source of volatile aldehydes.

Researchers also increased voltage and observed e-liquid consumed per puff and vapor temperature. Harmful chemicals appeared in all devices regardless of temperature, with higher temperatures similarly producing more harmful emissions.

Examining e-liquid solvents, researchers found mixtures of propylene glycol and glycerin in varying proportions in almost all products. Both generate artificial smoke. Their ratio determines factors such as vapor volume.

A total of 31 harmful compounds were identified, including two not previously detected in e-cigarettes: propylene oxide and glycidol. Researchers propose both are carcinogenic.

The study's conclusionis that e-cigarettes differ, contain potentially harmful chemicals, and factors such as heat, device type and age determine chemical release. Developing less harmful devices matters to consumers and manufacturers alike.