California Environmental Protection Agency

Air Resources Board

 No. 96-2

August 1996

 RESEARCH NOTES

Brief Reports to the Scientific and Technical Community

 Research Division, John R. Holmes, Ph.D., Chief

P.O. Box 2815, Sacramento CA 98512

Background:

The Air Resources Board (ARB) is required to assess the California population's exposure to toxic air contaminants in indoor environments and to identify the relative contribution of indoor concentrations to total exposure. Second-hand smoke, or environmental tobacco smoke (ETS), is one of the main indoor sources of many air pollutants, including a number of toxic air contaminants. The population's exposure to toxic air contaminants from ETS can be estimated in mathematical models using ETS emissions data, along with other inputs. A good understanding of the extent of such exposure is necessary in identifying the relative contributions of ETS and other, non-ETS sources to the overall risks posed by toxic air contaminants. Such information also can be used to develop the most effective exposure reduction approaches for those pollutants.

ETS is composed largely of sidestream smoke (the smoke that is emitted from the cigarette between puffs), with some contribution from the smoke that is exhaled by the smoker. As the smoke becomes diluted and lingers in a room, physical and chemical changes can occur. Pollutant levels in aged ETS might therefore be different from those in fresh sidestream smoke. Most of the cigarette emissions reported in the scientific literature have been measured in fresh sidestream smoke rather than in ETS, because specialized equipment (such as a large chamber) is needed to measure ETS under controlled conditions.

Prior to this study, information regarding ETS emissions for many of the toxic air pollutants of interest to the ARB was not available, was available only from fresh sidestream smoke measurements, or was available only from studies of research cigarettes and cigarette brands with unknown relevance to Californians. Also, since cigarette manufacturing processes have changed over the years, it was important to obtain emission measurements for cigarettes currently on the market.

Methods:

ETS was generated by introducing sidestream smoke into a room-sized chamber under well controlled laboratory conditions. Air samples were taken at various times as the smoke aged. Measurements of fresh sidestream smoke generated in a glass sampling apparatus were made for comparison with the chamber measurements. Six cigarette brands popular in California and a commonly used research cigarette were tested. The pollutants measured were 23 volatile organic compounds (VOCs), four N-nitrosamines, fine particles, nicotine, nitric oxide, and carbon monoxide. Eighteen of those compounds are designated by ARB as toxic air contaminants. The investigators measured the N-nitrosamines using an improved method they developed as part of this project. The new method employed a solid medium for sampling that was less cumbersome than liquid-filled bubblers.

Results:

Most of the targeted compounds were present at measurable levels. For those that were measurable, the ETS emissions ranged from 0.01 micrograms/cigarette for N-nitrosopyrrolidine to 2,200 micrograms/cigarette for acetaldehyde. For the few pollutants that had been measured in ETS in other studies, the emissions were generally in good agreement with those reported by other investigators. ETS emissions for some of the compounds are listed in Table 1.

ETS emissions were fairly consistent among the different cigarette brands, even when "regular" cigarettes were compared to mentholated and "light" cigarettes. Concentrations of all but four of the VOCs and aldehydes remained stable over the course of the ETS monitoring period: they showed no appreciable evidence of losses due to chemical reactions. Concentrations of the four VOCs with the lowest vapor pressures (m,p-cresol, o-cresol, phenol, and 3-vinylpyridine) appeared to decrease with time, probably due to deposition on the chamber surfaces. Two compounds (pyridine and pyrrole) emerged as potentially useful tracers for the more volatile components of ETS. ETS emissions values measured for most of the compounds were higher than those measured in fresh sidestream smoke; this was surmised to be due to greater surface losses and chemical reaction losses in the sidestream smoke apparatus and to different combustion conditions in the sidestream smoke apparatus. Exceptions were nicotine and particle emission values, which were higher in fresh sidestream smoke.

Significance and Application:

Related Projects:

This study provides unique information regarding the ETS emissions of a number of toxic pollutants, many of which have been designated by the ARB as toxic air contaminants. The fact that this is the only study of ETS emissions performed specifically on the most popular cigarette brands in California makes its results particularly relevant for ARB's needs. Moreover, by testing cigarettes that reflect recent changes in cigarette manufacturing processes, this study updates the very limited ETS data that were previously available. ARB will use the information obtained in this study to improve estimates of Californians' exposures to toxic air pollutants.

The ARB is funding a study to use the ETS emissions data in mathematical models to estimate Californians' recent and future exposures to selected toxic air contaminants emitted from cigarette smoke. One of the models to be used, called the California Population Indoor Exposure Model, was developed under ARB sponsorship.