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The measurement of ‘environmental tobacco smoke’ particulates
125
Toxicology Letters, 35 (1987) 125-129 Elsevier
TXL 01714
THE MEASUREMENT OF ‘ENVIRONMENTAL TOBACCO SMOKE’ PARTICULATES” (Total particulate smoke)
matter; instrumentation;
methods of measurement;
cigarette
ROGER G. RAWBONE, W. BURNS and R.A. PATRICK Research Division, Gallaher Ltd., Belfast BT15 IJE (Northern Ireland) (Received 5 September 1986) (Accepted 15 September 1986)
SUMMARY An analysis of sidestream smoke particulates in a wide range of study conditions, utilizing a variety of methods of measurement, was undertaken. The conclusion is that the term ‘total particulate matter’, as defined for mainstream smoke, has little or no meaning in the context of environmental tobacco smoke. Light-scattering instruments offer, in terms of portability and short sampling times, the best option for ambient particulate measurement. However, any quantitative interpretation of the results is dependent upon the initial calibration.
INTRODUCTION
Mainstream cigarette smoke is conventionally described in terms of particulate and vapour phases. ‘Total particulate matter ’ (TPM), in the U.K., relates to those smoke components which are retained on a Cambridge filter pad through which the smoke is drawn under standard machine smoking conditions [ 11. This term is widely used as being synonymous with that of the aerosol phase in smoke, but this is incorrect, studies having shown that the loaded Cambridge pad will partially retain
* Presented at the International Experimental Toxicology Symposium on Passive Smoking, October 23-25, 1986, Essen (F.R.G.). Any conclusion drawn in this paper is of the authors, not of the organization board of the symposium. Abbreviations:
MMAD, mass median aerodynamic diameter; TPM, ‘total particulate matter’.
0378-4274/87/$ 03.50 0 Elsevier Science Publishers B.V. (Biomedical Division)
126
vapours, particularly those of high water solubility [2]. The term ‘tar’ refers to the TPM minus its nicotine and water content. The distribution, in mainstream smoke, of specific chemicals between the vapour or ‘particulate’ phases has been assumed to apply to sidestream smoke, with respect to both bench-top analytical chemistry and to ambient air measurement. This takes no account of the definitions, nor of the fact that smoke is a dynamic aerosol system. The aerosol particles, comprising a complex mixture of compounds of differing volatility, will give rise to a vapour phase which will be moving toward an equilibrium state of stable partial pressures and particle sizes. Any disturbance of the equilibrium state which causes a decrease in vapour concentration, such as smoke dilution in a measurement system or in an ambient air, will diminish the final smoke particle size, with transfer of volatile components from the particles to the vapour phase. This will obviously be accompanied by a decrease in particulate mass. The objective of this paper is to present the results of a series of studies to illustrate the above and to discuss some of the consequences of the findings in relation to studies of ‘environmental tobacco smoke’ and the selection of appropriate instrumentation. MATERIALS AND METHODS
Sidestream smoke has been characterised, in 4 different experimental environments, with respect to TPM, nicotine, carbon monoxide and particle size distribution. In all studies a single commercial low-tar (9.5 mg) cigarette was freeburned to a fixed butt length. Experimental environments Glass chimney (BAT, U.K.) A cigarette was positioned under a glass hood into which air was drawn at 2.1 l/min. The sidestream smoke was flushed up a glass pipe (25 cm long x 2 cm diam.) at the top of which it was analysed. The total volume of the apparatus was 0.3 1. Keith apparatus [3] A single cigarette was enclosed in a vertical which had the facility of being water-cooled. by an airflow of 2.1 l/min, to the analytical upper end of the cylinder. The total volume
glass cylinder, open at the lower end, The sidestream smoke was drawn up, equipment attached to the funnelled of the apparatus was 3.0 1.
Sealed cube Cigarettes were enclosed in a sealed stainless steel box of internal volume approx. 8000 1. The air was mixed by a series of fans and sampled directly into the analytical instruments.
127
Environmental room Smoke was generated in a specially constructed room with a volume of about 48000 1. The internal walls, ceiling and floor were coated with a sealant paint and there was a single door with no windows; all other access for electric supply, air sample collection, etc., was through sealed ducting. Furniture was at a minimum. Measurement of TPM 3 different
methods of analysis have been employed.
Gravimetric determination Smoke was drawn through a pre-weighed Cambridge filter pad with the resultant increase in weight representing TPM. The filter characteristics of this pad have been clearly defined 141. Cascade impactor The cascade impactor permits the measurement of both particle size distribution and concentration. For the higher concentrations found in the glass chimney and the Keith apparatus, a standard cascade impactor (Delron, model DCIS) was used, whilst a quartz crystal impactor (California Measurements, model PC-SE) was employed in the box and environmental room. The latter instrument, for particles of mass density approximating that of tobacco smoke (1 g/cm3), will collect all particles of greater than 0.07 pm diameter, functioning over the concentration range IO ~g*mW3-f0 mg*me3. The response of this type of instrument may be affected by changes in temperature and humidity [5] or by the uptake of environmental gases [6]. No change in response has been observed, however, over our experimental range of temperature and humidity, and the device has been found to be insensitive to cigarette smoke vapour phase. MINIRAM personal monitor The MINIRAM (Miniature Real-time Aerosol Monitor, GCA Corporation, Model PDM-3) is a compact portable airborne particulate monitor whose operating principle is based on the detection of scattered electromagnetic radiation in the near infra-red. It has been designed for preferential response to the particle size range of 0.1-10 pm, but because its output is extremely sensitive to particle size distribution, the calibration becomes critical. The results are presented with the instrument calibrated in an environment of sidestream smoke where the concentration has been predicted on the basis of gravimetric delivery in the Keith apparatus. Measurement of nicotine and carbon monoxide Nicotine is trapped
completely
on the Cambridge
pad in mainstream
smoke
128 TABLE 1 SUMMARY OF RESULTS Environment
.-
Total particulate matter (mgicig.) Grav.
QCM
- Miniram
CO (mg/cig.)
Nicotine
Particle sizea
fmglcig.)
MMAD
Glass chimney 29 0.52 Keith apparatus 33 69 4.9 0.69 Stainless steel box 11 IO 69 75 0.20 Environmental room 5 30 71 1.4 0.21 _--.. a MMAD, mass median aerodynamic diameter em); ug, standard geometric deviation.
0g 1.46 1.52 1.70 1.77
analyses whilst in ambient sidestream environments it is distributed between particulate and vapour phases. The sampling techniques used in the current studies were designed to measure the total nicotine and consisted of collection into a Tenax trap and subsequent thermal desorption and gas chromatographic analysis (Perkin Elmer, ATDSO). Carbon monoxide was measured using a non-dispersive infra-red analyser (Analytical Development Co., Model RFA/ 1). RESULTS
The results are summarised in Table I, where each value represents the mean of a minimum of 3 observations. The figures are expressed in mg per cigarette to facilitate interpretation. DISCUSSION
The gravimetric 4eterminations show the reductions in TPM/cigarette as the smoke aerosol is diluted into the stainless steel box and mass is lost to the surrounding environment. The concordance of these results with the cascade impactor would indicate a final particulate mass of 5 mg/cigarette in the environmental room atmosphere from an initial 29 mg generated. The particle size results show a falling mass median aerodynamic diameter (MMAD) and rising standard geometric deviation (ag) as the smoke aerosol is increasingly diluted. Interpretation on the basis of evaporation alone would be an oversimplification, ignoring for example the coagulation of particles which occurs in situations where a higher smoke concentration persists. Thus, in a separate series of experiments not reported in detail, the particle size in the room was found to depend upon whether the smoke plume was actively dispersed as it formed or whether it was allowed to rise before being mixed into the room. The carbon monoxide levels remain constant and consistent throughout the series of studies indicating that there was no significant Ieakage in any of the experimental situations. The difference in nicotine levels between the bench-top apparatus and the environments room is a
129
reflection not only of its movement from the particulate phase but also of an apparent rapid adsorption to available surfaces. The MINIRAM is, because of its portability and short sampling time (10 s), the instrument most suited to studies of environmental smoke particulates. It is important to ensure, however, a calibration relevant to the target environment. With respect to tobacco smoke, as shown in Table I, a theoretical calibration against a bench-top yield is inappropriate, overestimating particulates in this example by a factor of 6. In a wide range of studies this relative overestimate was found to depend upon the product being smoked and on the presence or absence of exhaled mainstream smoke; it ranged in magnitude from a factor of 4 to over 7. This variability reflects the dependence of the MINIRA~ calibration on the particle size distribution, environmental studies would be further complicated by the presence of particulates from non-tobacco sources. A complete understanding of the behaviour of tobacco smoke particulate matter is necessary for both the measurement and the subsequent interpretation of results in any investigation of environmental tobacco smoke. The term ‘total particulate matter’, as defined for mainstream smoke, is not relevant in the context of environmental tobacco smoke. REFERENCES I
2 3 4 5 6
K. Rothwefl. and CA. Grant {Eds.), Stat~dard Methods for the analysis of tobacco smoke, 2nd ed. London: Tobacco Research Council, 1974. (Research paper 1I.) M.F. Dube and CR. Green, Methods of collection of smoke for analytical purposes, Recent Adv. Tob. Sci., 8 (1982) 42-102. CL. Browne, C.H. Keith and R.E. Allen, The effect of filter ventilation on the yield and composition of mainstream and sidestream smokes, Beitr. Tabakforsch. Int., 10 (1980) 81-90. International Organisation for Standardisation, International Standards IS0 3308, ISO, Geneva, 1977. P.S. Daley and D.A. Lunderen, The performance of piezoelectric crystal sensors used to determine aerosol mass concentrations, Am. ind. Hyg. Assoc. J., 36 (1975) 518-532. C.S. Kim, M.A. Eldridge and G.A. Lewars, Gaseous interference to performance of a quartz crystal aerosol mass monitor, J. Aerosol Sci., 15 f1984) 473-482.
Toxicology Letters, 35 (1987) 125-129 Elsevier
TXL 01714
THE MEASUREMENT OF ‘ENVIRONMENTAL TOBACCO SMOKE’ PARTICULATES” (Total particulate smoke)
matter; instrumentation;
methods of measurement;
cigarette
ROGER G. RAWBONE, W. BURNS and R.A. PATRICK Research Division, Gallaher Ltd., Belfast BT15 IJE (Northern Ireland) (Received 5 September 1986) (Accepted 15 September 1986)
SUMMARY An analysis of sidestream smoke particulates in a wide range of study conditions, utilizing a variety of methods of measurement, was undertaken. The conclusion is that the term ‘total particulate matter’, as defined for mainstream smoke, has little or no meaning in the context of environmental tobacco smoke. Light-scattering instruments offer, in terms of portability and short sampling times, the best option for ambient particulate measurement. However, any quantitative interpretation of the results is dependent upon the initial calibration.
INTRODUCTION
Mainstream cigarette smoke is conventionally described in terms of particulate and vapour phases. ‘Total particulate matter ’ (TPM), in the U.K., relates to those smoke components which are retained on a Cambridge filter pad through which the smoke is drawn under standard machine smoking conditions [ 11. This term is widely used as being synonymous with that of the aerosol phase in smoke, but this is incorrect, studies having shown that the loaded Cambridge pad will partially retain
* Presented at the International Experimental Toxicology Symposium on Passive Smoking, October 23-25, 1986, Essen (F.R.G.). Any conclusion drawn in this paper is of the authors, not of the organization board of the symposium. Abbreviations:
MMAD, mass median aerodynamic diameter; TPM, ‘total particulate matter’.
0378-4274/87/$ 03.50 0 Elsevier Science Publishers B.V. (Biomedical Division)
126
vapours, particularly those of high water solubility [2]. The term ‘tar’ refers to the TPM minus its nicotine and water content. The distribution, in mainstream smoke, of specific chemicals between the vapour or ‘particulate’ phases has been assumed to apply to sidestream smoke, with respect to both bench-top analytical chemistry and to ambient air measurement. This takes no account of the definitions, nor of the fact that smoke is a dynamic aerosol system. The aerosol particles, comprising a complex mixture of compounds of differing volatility, will give rise to a vapour phase which will be moving toward an equilibrium state of stable partial pressures and particle sizes. Any disturbance of the equilibrium state which causes a decrease in vapour concentration, such as smoke dilution in a measurement system or in an ambient air, will diminish the final smoke particle size, with transfer of volatile components from the particles to the vapour phase. This will obviously be accompanied by a decrease in particulate mass. The objective of this paper is to present the results of a series of studies to illustrate the above and to discuss some of the consequences of the findings in relation to studies of ‘environmental tobacco smoke’ and the selection of appropriate instrumentation. MATERIALS AND METHODS
Sidestream smoke has been characterised, in 4 different experimental environments, with respect to TPM, nicotine, carbon monoxide and particle size distribution. In all studies a single commercial low-tar (9.5 mg) cigarette was freeburned to a fixed butt length. Experimental environments Glass chimney (BAT, U.K.) A cigarette was positioned under a glass hood into which air was drawn at 2.1 l/min. The sidestream smoke was flushed up a glass pipe (25 cm long x 2 cm diam.) at the top of which it was analysed. The total volume of the apparatus was 0.3 1. Keith apparatus [3] A single cigarette was enclosed in a vertical which had the facility of being water-cooled. by an airflow of 2.1 l/min, to the analytical upper end of the cylinder. The total volume
glass cylinder, open at the lower end, The sidestream smoke was drawn up, equipment attached to the funnelled of the apparatus was 3.0 1.
Sealed cube Cigarettes were enclosed in a sealed stainless steel box of internal volume approx. 8000 1. The air was mixed by a series of fans and sampled directly into the analytical instruments.
127
Environmental room Smoke was generated in a specially constructed room with a volume of about 48000 1. The internal walls, ceiling and floor were coated with a sealant paint and there was a single door with no windows; all other access for electric supply, air sample collection, etc., was through sealed ducting. Furniture was at a minimum. Measurement of TPM 3 different
methods of analysis have been employed.
Gravimetric determination Smoke was drawn through a pre-weighed Cambridge filter pad with the resultant increase in weight representing TPM. The filter characteristics of this pad have been clearly defined 141. Cascade impactor The cascade impactor permits the measurement of both particle size distribution and concentration. For the higher concentrations found in the glass chimney and the Keith apparatus, a standard cascade impactor (Delron, model DCIS) was used, whilst a quartz crystal impactor (California Measurements, model PC-SE) was employed in the box and environmental room. The latter instrument, for particles of mass density approximating that of tobacco smoke (1 g/cm3), will collect all particles of greater than 0.07 pm diameter, functioning over the concentration range IO ~g*mW3-f0 mg*me3. The response of this type of instrument may be affected by changes in temperature and humidity [5] or by the uptake of environmental gases [6]. No change in response has been observed, however, over our experimental range of temperature and humidity, and the device has been found to be insensitive to cigarette smoke vapour phase. MINIRAM personal monitor The MINIRAM (Miniature Real-time Aerosol Monitor, GCA Corporation, Model PDM-3) is a compact portable airborne particulate monitor whose operating principle is based on the detection of scattered electromagnetic radiation in the near infra-red. It has been designed for preferential response to the particle size range of 0.1-10 pm, but because its output is extremely sensitive to particle size distribution, the calibration becomes critical. The results are presented with the instrument calibrated in an environment of sidestream smoke where the concentration has been predicted on the basis of gravimetric delivery in the Keith apparatus. Measurement of nicotine and carbon monoxide Nicotine is trapped
completely
on the Cambridge
pad in mainstream
smoke
128 TABLE 1 SUMMARY OF RESULTS Environment
.-
Total particulate matter (mgicig.) Grav.
QCM
- Miniram
CO (mg/cig.)
Nicotine
Particle sizea
fmglcig.)
MMAD
Glass chimney 29 0.52 Keith apparatus 33 69 4.9 0.69 Stainless steel box 11 IO 69 75 0.20 Environmental room 5 30 71 1.4 0.21 _--.. a MMAD, mass median aerodynamic diameter em); ug, standard geometric deviation.
0g 1.46 1.52 1.70 1.77
analyses whilst in ambient sidestream environments it is distributed between particulate and vapour phases. The sampling techniques used in the current studies were designed to measure the total nicotine and consisted of collection into a Tenax trap and subsequent thermal desorption and gas chromatographic analysis (Perkin Elmer, ATDSO). Carbon monoxide was measured using a non-dispersive infra-red analyser (Analytical Development Co., Model RFA/ 1). RESULTS
The results are summarised in Table I, where each value represents the mean of a minimum of 3 observations. The figures are expressed in mg per cigarette to facilitate interpretation. DISCUSSION
The gravimetric 4eterminations show the reductions in TPM/cigarette as the smoke aerosol is diluted into the stainless steel box and mass is lost to the surrounding environment. The concordance of these results with the cascade impactor would indicate a final particulate mass of 5 mg/cigarette in the environmental room atmosphere from an initial 29 mg generated. The particle size results show a falling mass median aerodynamic diameter (MMAD) and rising standard geometric deviation (ag) as the smoke aerosol is increasingly diluted. Interpretation on the basis of evaporation alone would be an oversimplification, ignoring for example the coagulation of particles which occurs in situations where a higher smoke concentration persists. Thus, in a separate series of experiments not reported in detail, the particle size in the room was found to depend upon whether the smoke plume was actively dispersed as it formed or whether it was allowed to rise before being mixed into the room. The carbon monoxide levels remain constant and consistent throughout the series of studies indicating that there was no significant Ieakage in any of the experimental situations. The difference in nicotine levels between the bench-top apparatus and the environments room is a
129
reflection not only of its movement from the particulate phase but also of an apparent rapid adsorption to available surfaces. The MINIRAM is, because of its portability and short sampling time (10 s), the instrument most suited to studies of environmental smoke particulates. It is important to ensure, however, a calibration relevant to the target environment. With respect to tobacco smoke, as shown in Table I, a theoretical calibration against a bench-top yield is inappropriate, overestimating particulates in this example by a factor of 6. In a wide range of studies this relative overestimate was found to depend upon the product being smoked and on the presence or absence of exhaled mainstream smoke; it ranged in magnitude from a factor of 4 to over 7. This variability reflects the dependence of the MINIRA~ calibration on the particle size distribution, environmental studies would be further complicated by the presence of particulates from non-tobacco sources. A complete understanding of the behaviour of tobacco smoke particulate matter is necessary for both the measurement and the subsequent interpretation of results in any investigation of environmental tobacco smoke. The term ‘total particulate matter’, as defined for mainstream smoke, is not relevant in the context of environmental tobacco smoke. REFERENCES I
2 3 4 5 6
K. Rothwefl. and CA. Grant {Eds.), Stat~dard Methods for the analysis of tobacco smoke, 2nd ed. London: Tobacco Research Council, 1974. (Research paper 1I.) M.F. Dube and CR. Green, Methods of collection of smoke for analytical purposes, Recent Adv. Tob. Sci., 8 (1982) 42-102. CL. Browne, C.H. Keith and R.E. Allen, The effect of filter ventilation on the yield and composition of mainstream and sidestream smokes, Beitr. Tabakforsch. Int., 10 (1980) 81-90. International Organisation for Standardisation, International Standards IS0 3308, ISO, Geneva, 1977. P.S. Daley and D.A. Lunderen, The performance of piezoelectric crystal sensors used to determine aerosol mass concentrations, Am. ind. Hyg. Assoc. J., 36 (1975) 518-532. C.S. Kim, M.A. Eldridge and G.A. Lewars, Gaseous interference to performance of a quartz crystal aerosol mass monitor, J. Aerosol Sci., 15 f1984) 473-482.