30 YEARS of Environmental & Industrial Health Services


Second Hand Smoke

Second Hand Smoke


Environmental tobacco smoke (ETS), also known as secondhand smoke (SHS), is a complex mixture of thousands of gases and fine particles emitted by the burning of tobacco products and from smoke exhaled by the smoker.  Cigarette smoking is offensive to many nonsmokers and simply the smell of tobacco smoke can trigger strong adverse reactions.  


Smoking Machines measure Mainstream Smoke - MSSkalsky & Associates has trial experience in explaining the differences between the risk of smelling tobacco smoke and risk posed to a smoker that inhales main stream tobacco smoke.  We can evaluate (and where necessary measure) second hand smoke exposures and convey our findings and conclusions to jurors.

Within the emotionally charged arena of tobacco politics, it is sometimes difficult to sort out scientific fact from unsound conjecture.  This is particularly true when trying to establish causation for the adverse effects of ETS.  The vast majority of the data concerning the toxic effects of smoking have been developed around the adverse effects of mainstream smoke (MS).  The toxicology of MS has been reasonably well characterized using standard experimental protocols which often employ standardized smoking machines with set puff volumes and frequencies. 

Second Hand Smoke includes EMS - Exhaled Mainstream SmokeHowever, ETS (Environmental tobacco smoke) is made up of mainstream smoke (MS) that has been drawn into and “filtered” by the smoker’s respiratory system and then exhaled.  Backer and Proctor (1990) demonstrated that exhaled mainstream smoke (EMS) contributes little to the gas phase of ETS.  Although, some particulate matter is retained by the smoker, the particles that are exhaled contribute significantly to ETS particulate phase.  The exhaled particulate is larger in size (Sahu et al. 2013) indicating coagulation and hygroscopic growth within the smoker’s respiratory system. 


Although some similarities exists, mainstream smoke and exhaled mainstream smoke are not the same.  Unfortunately, there has not been any significant toxicological data gathered on Exhaled Mainstream Smoke.  Therefore, the toxic effects that have been described for MS would not be expected to be the same for ETS.  However, the extent of the dissimilarities is unknown.

Sidestream Smoke comes from around the tio of the smoldering cigarette.ETS is also made up of sidestream smoke (SS).  SS is generated around the smoldering tip of the cigarette.  In general, SS is generated at lower temperatures, approximately 600°C between pulls versus 800-900°C during puffs when MS is generated.  There are clear differences in the composition of SS and MS that are temperature and available oxygen related.  The rapid dilution of SS with air also results in a smaller particle size than that found in mainstream smoke.  SS is the source of nearly all of the vapor-phase constituents of ETS.  Although much of vapor phase of ETS originates from SS, the great dilution and other changes ETS undergoes make its properties significantly different.  Therefore, the toxic effects that have been described for SS would not be expected to be the same for ETS.  However, the extent of the dissimilarities is unknown.

Since ETS is a complex mixture of gases and particulate matter, it is literally impossible to measure all of the constituents to assess an individual’s exposure.  However, such a measurement is essential to study the potential health impact of ETS.  Investigators have been trying to identify an indicator (or a marker) of ETS, that can be measured and that represents the magnitude, duration and frequency of ETS exposure.  To date, no perfect marker has been found.  The most widely used markers have been vapor-phase nicotine and respirable particulate matter (PM).

The measurement of nicotine in the air has the advantage of reflecting the presence of tobacco smoke. While PM measurements are not as specific, they can be taken continuously, allowing for assessment of exposure and its variation over time.  PM is typically classified by aerodynamic diameter, for example, PM10 is comprised of particles less than 10 µm in aerodynamic diameter and PM2.5 is comprised of particles less than 2.5 µm in aerodynamic diameter.  Most particles produced through tobacco smoking are smaller than 1 µm in diameter.  For this reason, PM2.5 is more frequently used as an indirect measure of ETS.


None of the markers in use today will completely reflect the true nature of the over 4000 chemicals that have been detected in ETS.  However, the measurement of both nicotine and PM together appear to be the most accepted method of assessing ETS exposure.  In general, when nicotine and PM are measured in the same setting using a common sampling period, an increase in nicotine concentration of 1 µg/m3 corresponds to an average increase of 10 µg/m3 of PM.


Smoker vs. NonsmokerConflict can arise between smokers and non smokers.  Strong emotions can often distort the differences between the real verses the perceived risks of second smoke exposure   Skalsky & Associates has trial experience in explaining these differences to jurors.


Baker R.R. and Proctor C.J. (1990)  The Origins and Properties of Environmental Tobacco Smoke. Environment International, 16, 231-245.
Sahu SK el al. (2013)  Particle Size Distribution of Mainstream and Exhaled Cigarette Smoke and Predictive Deposition in Human Respiratory Tract.  Aerosol and Air Quality Research 13: 324-332


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