The<unk>  of the<unk>  generated from<unk><unk><unk> s are generally lower than that found in cigarette smoke. This is due to the comparatively low temperatures, the filter systems, and physical design. The<unk>  of what is<unk> d is complex. The main toxicants found in the<unk>  of cigarette smoke (i.e., tar, nicotine, carbonyl compounds, and nitrosamines) are also found in the<unk>  of these<unk> s in varying concentrations. The aerosol generated contains levels of nicotine and cancer-causing chemicals that are comparable to regular cigarettes. The<unk>  contained 84% of the nicotine found in regular cigarettes. The available research on the mainstream and exhaled aerosol generated by these<unk> s is limited, as of 2018. They do not generate side-stream<unk> . The exhaled aerosol is highly volatile because it is made up of liquid particles that evaporate quickly. The particle size of their<unk>  have a median aerodynamic diameter that is somewhat bigger than those found in cigarette smoke. There is a lack of agreement on the<unk>  of the<unk>  in the documented literature, as of 2018. These<unk> s, however, still pose health risks. Lower levels of harmful<unk>  has been shown, but lowering the risk to the smoker who transitions to using them has not been shown, as of 2018. As a result of the various types of<unk><unk><unk> s, the characteristics and effects for each type will be different. Since the 1960s<unk><unk><unk> s were in development by<unk>  companies. Safer<unk><unk><unk> s that deliver nicotine but limit<unk>  of tar or carbon monoxide (CO) is a half-century old idea, which had been unsuccessfully market-tested since 1988, first as Premier by the RJ Reynolds<unk>  Company (RJR) and later as Eclipse (RJR) and Accord Philip Morris International (PMI). Various<unk><unk> s were reintroduced to the market, as of 2018.
Composition of heated tobacco product emissions
Composition of electronic cigarette aerosol
Toxic capacity
Safety of electronic cigarettes
Measures of pollutant concentration
Instruments used in medical laboratories
Measured environmental concentration
Index of pesticide articles