Developmental toxicity of e-cigarette aerosols.

Introduction:
This article reviews the developmental toxicity of e-cigarette aerosols and the need for further studies to determine the risks versus benefits of electronic cigarette use by pregnant women. The text highlights the lack of conclusive scientific evidence supporting the health-related safety of electronic nicotine delivery systems (ENDS) and the potential adverse developmental effects of smoking during pregnancy.

Key Points:

* Smoking during pregnancy is a major public health concern, increasing the risk for low birth weight, congenital anomalies, preterm birth, fetal mortality, and morbidity.
* The health risks associated with ENDS use during pregnancy are largely unknown, and there is a need to determine the risks vs. benefits of electronic cigarette use by pregnant women.
* Nicotine, a highly addictive component of tobacco-based products, readily crosses the placenta and is concentrated in the fetal compartment, where it binds to nicotinic acetylcholine receptors that are widely expressed throughout the fetal nervous system, lungs, and other fetal tissues.
* Nicotine is a developmental toxicant that is capable of interfering with normal neurotransmitter function, resulting in apoptosis and mitotic abnormalities, inducing lung and neurodevelopmental abnormalities, and causing genotoxic effects in human fetal cells in vitro.
* The National academies of Sciences, Engineering, and Medicine (NaSEM) found no available evidence whether or not e-cigarettes affect pregnancy outcomes and insufficient evidence whether or not maternal e-cigarette use affects fetal development.
* Recent developmental studies have challenged the safety of pure nicotine inhalation by ENDS, especially during pregnancy, and in vitro studies have shown that exposure to ENDS aerosols or vapor extracts may be harmful to the developing embryo/fetus.
* ENDS usage exposes the user, including the developing conceptus, to constituents of the aerosol generated from vaporization of the base e-liquid, including known carcinogens and toxic chemicals such as nitrosamines, formaldehyde, acetaldehyde, acrolein, propylene glycol, glycerin and the heavy metals lead, chromium, manganese and nickel.
* The apparent source of many of the heavy metals is leakage from the e-cigarette heating coils into the aerosols that users inhale.
* Further studies are needed to determine whether the levels of toxic chemicals and heavy metals in e-cigarette aerosols pose a health risk across all population demographics, including during pregnancy.

Main Message:
The text emphasizes the need for further studies to determine the risks versus benefits of electronic cigarette use by pregnant women. The lack of conclusive scientific evidence supporting the health-related safety of ENDS, the potential adverse developmental effects of smoking during pregnancy, and the potential harmful effects of nicotine and other toxic chemicals in e-cigarette aerosols highlight the importance of this research. The text also highlights the need for regulation of ENDS to ensure safety and minimize potential health risks.

Greene RM, Pisano MM. Developmental toxicity of e-cigarette aerosols. Birth defects research. 2019;111(17):1294-1301. doi:10.1002/bdr2.1571