WASHINGTON — The National Academies of Sciences, Engineering and Medicine released a report on Tuesday assessing studies about the health effects of e-cigarettes. The panel of experts conducted a comprehensive review of research in the field, categorizing evidence on various issues as conclusive, substantial, limited or nonexistent. Below are some of their conclusions.

Nicotine and addiction

There is substantial evidence that e-cigarette use can be addictive. Exposure to nicotine varies a lot, depending on the device and the e-liquid it uses, as well as the individual vaper’s practices. But, the report said, there is also substantial evidence that nicotine intake from e-cigarettes, used by experienced adults, can be comparable to that of conventional cigarettes.

Moderate evidence: The risk and severity of dependence on e-cigarettes is lower than for conventional cigarettes.

Toxic substances

Traditional cigarettes pose serious risks to human health, much of it from toxic tobacco smoke. There is conclusive evidence that most e-cigarette products contain and emit numerous potentially toxic substances, and that they increase airborne particulate matter and nicotine indoors. But despite that, the evidence suggests that e-cigarette aerosol contains fewer toxic substances and lower levels of them than smoke from conventional cigarettes.