Particulate matter emissions of four types of one cigarette brand with and without additives: a laser spectrometric particulate matter analysis of secondhand smoke

Abstract

Objective

Inhaled particulate matter (PM) in secondhand smoke (SHS) is deleterious for smokers and non-smokers. Different additives in cigarettes might effect the amount of PM. This study aimed to assess the influence of additives on the PM emissions from different cigarette types in SHS.

Design

An experimental study of PM measuring in SHS of cigarettes without exposition of any person.

Method

The concentrations of PM (PM₁₀, PM_2.5 and PM₁) in SHS of four different types of cigarettes of the brand Lucky Strike, two types with additives (Original Red, Original Blue) and two types without additives (Straight Red, Straight Blue), in comparison to the reference cigarette 3R4F were analysed. An automatic environmental tobacco smoke emitter generated SHS in an enclosed space with a volume of 2.88 m³. PM was measured with a laser aerosol spectrometer (Grimm model 1.109). Afterwards, the measuring values of the four Lucky Strike brands and the reference cigarette were statistically evaluated and visualised.

Results

Lucky Strike Straight Blue, a cigarette type without additives and lower tar amount, showed 10% to 25% lower PM mean values compared with the other tested Lucky Strike products, but 21% (PM₁) respectively 27% (PM_2.5,PM₁₀) higher mean values than the reference cigarette. The PM mean of all measured smoke-free baseline values (clean air) was 1.6 µg/m³. It increased up to about 1800 µg/m³ for the reference cigarette and up to about 3070 µg/m³ for the Lucky Strike Original Blue.

Conclusions

The findings of this study show the massive increase of PM amount by smoking cigarettes in enclosed spaces and suggest that additives in tobacco products increase the PM amount in SHS. For validation, further comparative studies are necessary focusing on the comparison of the PM concentration of cigarettes with and without additives.

Implications

Due to the exposure to SHS, 890 000 people die each year worldwide. PM in SHS endangers the health of both non-smokers and smokers. This study considers the effect of additives like aromatics and humectant agents in cigarettes on PM in SHS. Do additives in tobacco products increase the amount of PM?

Strength and limitations of this study.

• Different types of tobacco products with and without additives were checked against each other regarding airborne particulate matter (PM) directly.

• The automatic environmental tobacco smoke emitter generated reproducible and reliable PM levels in accordance with a standardised smoking protocol.

• The used laser aerosol spectrometer measures the emitted particles in a size range of 0.25 µm to 32 µm in real time.

• The mechanism simulated reliable and comparable conditions without exposing test persons or the investigator.

• The applied technique was not able to imitate accurately the human smoking behaviour in every detail.

Introduction

Airborne particulate matter (PM) as a part of air pollution causes tremendous adverse health effects. Especially cardiovascular and respiratory diseases¹ and aggravates airway inflammation and hyper-responsiveness in asthmatic patients² should be mentioned in this context. The exposure to PM is also associated with increased risk of ischaemic stroke³ and breast cancer mortality.⁴ Several studies showed increase in morbidity and mortality in relation to higher PM exposure.⁵

PM is a mixture of solid and liquid particles varying in size, composition and origin.⁶ The most relevant and common option to classify PM is by size of the particles that determines how deep they penetrate the respiratory system. The US Environmental Protection Agency (EPA) differentiates between PM_10, inhalable coarse particles equal or smaller than 10 µm, and PM_2.5, fine inhalable particles equal or smaller than 2.5 µm.⁷ In addition, PM₁ is the fraction of particles equal or smaller than 1 µm. The smaller the particles the deeper they penetrate in the respiratory system and the more extensive are the health effects.^8–10

The majority of PM derives from tobacco smoke.¹¹ Worldwide approximately one billion adults smoke.¹² Each year more than 7 million people are killed due to tobacco use, and 890 000 of those are non-smokers being exposed to secondhand smoke (SHS), also called environmental tobacco smoke.¹³ SHS mainly consists of side-stream smoke emitted directly from the smouldering tobacco product and the exhaled mainstream smoke from the smoker.^{14 15} It is considered to be the major risk factor for air pollution in indoor spaces.¹⁶

Previous analyses revealed variations of PM levels within different brands and types of cigarettes.^17–19 The content of tar, nicotine and various additives (eg, aromatics and humectant agents) might affect the amount of PM.²⁰

Based on these findings, it is reasonable and necessary to compare different cigarette types of a special brand with and without additives. Therefore, the aim of this study was to investigate the influence of additives on PM emissions of cigarettes. Hence, the particle size fractions of PM₁₀, PM_2.5 and PM₁ of four different types of the popular cigarette brand Lucky Strike²¹ and of the reference cigarette 3R4F, developed by the Kentucky Tobacco Research and Development Center (University of Kentucky, USA),²² were analysed. At the time of the study, Lucky Strike offered each two cigarette types with and without additives with nearly congruent amounts of tar, nicotine and carbon monoxide. The Lucky Strike cigarette types were Original Red and Original Blue (with additives)^{23 24} and Straight Red and Straight Blue (without additives)^{25 26} were included in the analysis. They differed among others in content of tar, nicotine, carbon monoxide and additives as shown in table 1. For more detailed information, refer to the Federal Ministry of Food and Agriculture of Germany (Bundesministerium für Ernährung und Landwirtschaft).^23–26

Table 1.

List of the cigarette ingredients with reference to tar, nicotine, carbon monoxide and additives^22–26

	Reference Cigarette 3 R4F	Lucky Strike Original Red	Lucky Strike Original Blue	Lucky Strike Straight Red	Lucky Strike Straight Blue
Tar (mg)	9.4	10	7	10	7
Nicotine (mg)	0.73	0.8	0.6	0.9	0.6
Carbon monoxide (mg)	12	10	8	10	8
Glycerine (H.A.)	Yes	Yes	Yes	No	No
Sugar (A.)	Yes	Yes	Yes	No	No
Cocoa powder (A.)	n/s	Yes	Yes	No	No
Licorice extract (A.)	n/s	Yes	Yes	No	No
Flavours below 0.1% w/w (A.)	n/s	Yes	Yes	No	No

A, aromatic; HA, humectant agent.

n/s, not significant.

To minimise other influences on the amount of PM, for example dissimilar manufacture processes of different tobacco companies, test cigarettes of one cigarette brand were selected.

Methods

Nineteen cigarettes of four tobacco products from Lucky Strike, two each with and without additives, and 19 reference cigarettes were smoked using an automatic environmental tobacco smoke emitter (AETSE). The individual PM levels (PM₁₀, PM_2.5, PM₁) were recorded and evaluated. A modified smoking protocol according to the Tobacco Smoke Particles and Indoor Air Quality (ToPIQ) studies^{17 27} was applied.

The AETSE is located in a closable chamber with a volume of 2.88 m³. This smoke pump for medical research, designed and engineered by Schimpf-Ing, Trondheim, Norway,²⁸ allows the smoking of tobacco products in a reproducible way without exposing test persons and the investigator. A stepper motor moves via a linear actuator a 200 mL glass syringe that imitates the process of smoking. Puff volume (40 ml), puff flow rate (13 ml/s), puff frequency (2/min), inter-puff interval (22 s) and amount of nine puffs is adjusted by a microcontroller. The smoking protocol is divided into four different phases of each 5 min. It starts with the pre-ignition phase and measurement of the baseline values. Then, the cigarette is lighted and smoked in the combustion phase. The post-combustion phase follows, which starts with the extinguishing of the cigarette. In the last cycle phase, the indoor air is cleaned by using an industrial suction device before the next cycle starts. Each cycle lasts 20 min. The PM concentrations in the chamber is measured in a dilution of 1:10 with compressed air by a Grimm Portable Laser Aerosol Spectrometer and Dust Monitor model 1.109.^{29 30} The dilution with compressed air is necessary to protect the spectrometer against blockage of the laser measuring chamber by high particle concentrations. When evaluating the measurement results, the dilution ratio of 1:10 has to be taken into account. The spectrometer detects in real time via light scattering airborne particles with a size range from 0.25 to 32 µm. It displays the output of measurement data as particle count [l^-1] and detailed dust mass fractions in 31 channels (µg/m³). Furthermore, it is possible to present the data output as inhalable, thoracic and alveolic (µg/m³) according to European standard EN 481³¹ or as PM₁₀, PM_2.5 and PM₁ values according to the US EPA.⁷ The received data is recorded every 6 s. Subsequently, the PM values are statistically evaluated by calculating the area under the curve (AUC) and the mean concentration (C_mean). In this study, the AUC describes the area under a concentration-time curve in the 5 min lasting interval from ignition to extinction of a cigarette. Since all measured data of the cigarette samples passed the test for Gaussian normality, the Kruskal-Wallis test followed by the Dunn’s multiple comparison test (post hoc test) were done to compare the individual values of the investigated cigarette types with each other.

Patient involvement

Patients were not involved.

Results

The data of AUC-PM of all types of Lucky Strike cigarettes were 21%–71% higher than the data of the reference cigarette (figure 1). The values of C_mean-PM of all types of Lucky Strike cigarettes were 22%–71% higher than the values of C_mean-PM of the reference cigarette as well (table 2). Furthermore, the differences of AUC and C_mean of PM₁, PM_2.5 and PM₁₀ of all Lucky Strike brands except Straight Blue showed a high statistical significance compared with the AUC-PM and C_mean of the reference cigarette.

Figure 1.

Comparison of area under the curve (AUC) (PM₁₀, PM_2.5 and PM₁) for all tested tobacco products.

Table 2.

Mean concentrations (C_mean PM₁₀, PM_2.5 and PM₁) with SD of all tested tobacco products

	Reference Cigarette 3 R4F	Lucky Strike Original Red	Lucky Strike Original Blue	Lucky Strike Straight Red	Lucky Strike Straight Blue
CmeanPM10(µg/m³)	1803±320	2557±726	3076±321	2704±261	2300±340
CmeanPM2.5(µg/m³)	1801±320	2550±724	3068±319	2700±261	2294±339
CmeanPM1(µg/m³)	1762±302	2402±624	2865±282	2530±231	2145±306

PM, particulate matter.

The main part of SHS consists of the PM₁fraction with 97.7% (reference cigarette), 93.9% (Lucky Strike Original Red), 93.1% (Lucky Strike Original Blue), 93.6% (Lucky Strike Straight Red) and 93.3% (Lucky Strike Straight Blue), respectively (figure 2).

Figure 2.

Distribution pattern of PM_10–2.5, PM_2.5–1 and PM₁ of all investigated cigarettes. PM, particulate matter; SHS, secondhand smoke.

More specifically, Lucky Strike Straight Blue, a tobacco product without additives and lower tar amount (table 1), showed 10%–25% lower PM mean values compared with the other tested Lucky Strike products. The differences between Lucky Strike Straight Blue and Lucky Strike Original Blue were highly significant (p≤0.0005), and between Lucky Strike Original Red and Lucky Strike Original Blue significant too (p<0.05). Lucky Strike Straight Blue showed also less PM values than Lucky Strike Straight Red but no statistical significance (p>0.05). Details are shown in table 3. In a comparison of Lucky Strike Straight Blue with the reference cigarette, the AUC-PM₁ mean values were only 21%, the AUC-PM_2.5 and AUC-PM₁₀ mean values 27% higher, respectively. Accordingly, the C_mean values of PM₁, PM_2.5 and PM₁₀ of Lucky Strike Straight Blue were 22%, 27% and 28% higher than the values of the reference cigarette.

Table 3.

P values of the statistical Dunn’s multiple comparisons test of AUC (PM₁₀, PM_2.5 and PM₁) for the Lucky Strike brands

	Original Red vs Original Blue	Original Red vs Straight Red	Original Red vs Straight Blue	Original Blue vs Straight Red	Original Blue vs Straight Blue	Straight Red vs Straight Blue
AUC PM10	0.0424	>0.9999	>0.9999	0.6131	0.0005	0.2817
AUC PM2.5	0.0424	>0.9999	>0.9999	0.6131	0.0005	0.2775
AUC PM1	0.0465	>0.9999	>0.9999	0.6131	0.0002	0.1829

Significant results are highlighted by bold font type.

AUC, area under the curve; PM, particulate matter.

In contrast, the AUC-PM mean values as well as the C_mean values of the Lucky Strike Original Blue, a cigarette with additives, but the same tar amount as Lucky Strike Straight Blue, were substantially higher (PM_1,63%, PM_2.5,70%, PM₁₀71%) compared with the reference cigarette. The measuring data of Lucky Strike Straight Red were in between 43% (PM₁) and 50% (PM_2.5 PM₁₀) higher compared with the reference cigarette. Furthermore, the measured values of Lucky Strike Original Red were in between 36% (PM₁) and 41% (PM_2.5) respectively 42% (PM₁₀) higher than the values of the reference cigarette.

The fact that the additive-free Lucky Strike Straight Blue with a lower tar amount showed the lowest measurement values of all four Lucky Strike cigarette products suggests that additives in cigarettes in combination with a higher tar amount increase the PM emissions.

The PM mean of all measured baseline values (smoke-free air) was 1.6 µg/m³. The measured C_mean of PM₁₀ increased up to 1803 µg/m³ (±320 µg/m³) for the reference cigarette and 3076 µg/m³ (±321 µg/m³) for Lucky Strike Original Blue. In case of PM_2.5 it went up to 1801 µg/m³ (±320 µg/m³) respectively 3068 µg/m³ (±319 µg/m³). The values for PM₁increased up to 1762 µg/m³ (±302 µg/m³) respectively 2865 µg/m³ (±282 µg/m³).

Discussion

The findings of the presented study show that tobacco smoke in an enclosed space of 2.88 m³ (capacity of the measuring cabin) increased the particulate matter emissions compared with smoke-free air (baseline values) more than a 1000-fold. The measured PM_2.5 values exceeded the daily average concentration of the maximum of 25 µg/m³ according to the WHO air quality guidelines³² approximately 70-fold to 120-fold, depending on the cigarette brand. This illustrates the massiveness of PM burdens under the study conditions.

A compact car, classified by the EPA with a total passenger and cargo volume of 2.832 m³ to 3.087 m³,³³ has a indoor volume that is comparable to the measuring cabin. The modified smoking regime that was used is similar to conditions in a compact car with closed windows and no ventilation or air conditioning. This is a fundamentally important aspect of the study design, because many people smoke in cars. The passive smoke with the contained particulate matter is not only hazardous to the health of smokers but also to passengers who are often children.

Different studies show a hazardous increase of PM levels in smoking rooms and households,^34–37 but only a few studies were published with respect to an effect of additives on PM with contradictory conclusions. In 2002, Rustemeier et al ²⁰ performed a study, in which 333 commonly used ingredients were added to the reference cigarette 1R4F. The results showed an increase of 13%–28% of PM relative to the cigarettes without added additives. In 2011, Wertz et al ³⁸ analysed formerly secret documents of the tobacco industry. They found among others four peer-reviewed publications that concluded no correlation between additives and toxicity as well as total particulate matter (TPM). Regarding this, internal documents of the tobacco industry showed post hoc changes in protocols after previous statistical findings of an additive-associated increase in toxicity and TPM concentrations. Wasel et al ¹⁸ found no significant differences in the PM amount of L&M cigarettes with and without additives. Similar findings showed the studies of Gaworski et al ³⁹ and Gerharz et al.⁴⁰ They could not prove the influence of the additive menthol.

Therefore, the main focus of this study was to investigate the impact of cigarette additives on PM emissions. It seemed to be advisable to choose cigarette types of one manufacturer to minimise influences on PM emissions by, for example, production processes. Of the four tested Lucky Strike types, the cigarettes without additives in combination with lower tar amount (Lucky Strike Straight Blue) emitted less PM than those without additives but with higher tar amount (Lucky Strike Straight Red), respectively those with additives but lower tar amount (Lucky Strike Original Blue). That would justify the claim that additives have an impact on the concentration of PM in SHS, though the smoke of Lucky Strike Straight Red (without additives) and Lucky Strike Original Red (with additives) contained similar PM amounts. However, all tested cigarettes of the brand Lucky Strike emitted significant higher PM levels than the reference cigarette. In conclusion, the findings could not ascertain beyond doubt that additive-free cigarettes produced by one manufacturer emit less PM than cigarettes with additives. Therefore, further studies are necessary to prove this assumption.

In this study, by far the largest part of PM is represented by particles ≤1 µm and ≥0.25 µm. Depending on the cigarette brand, over 93% to nearly 98% of the measured PM was PM₁ (figure 2). Already in 1960, Keith and Derrick⁴¹ showed that most of the particles in tobacco smoke has a size between 0.1 µm and 1 µm and peaked between 0.2 µm and 0.25 µm. Nazaroff and Klepeis⁴² described SHS with a particle size between 0.02 µm and 2 µm in diameter. There is no common agreement on the peak size. On the one hand, side-stream smoke particles were described with geometric mean diameters of 0.1 µm.^{43 44} As opposed to that, Haustein and Groneberg⁴⁵ reported mean diameters of 0.5 µm. In this respect, it has to be mentioned that the used aerosol spectrometer Grimm model 1.109 only detects particles with a minimum size of 0.25 µm. Thus, the part of PM₁ smaller than 0.25 µm could not be measured. This led to a deviation of the PM₁ content in accordance with the EPA definition that includes particles down to 0.1 µm.

It must be mentioned that the used laser aerosol spectrometer, built for continuous measurement of PM, is also commonly used in monitoring networks.⁴⁶ An advantage of the spectrometer is the possibility to measure PM, including PM₁ and semi-volatile fractions (eg, water, ammonium nitrate, some organic compounds) via light scattering in real time.⁴⁷ This allowed to investigate the amount of PM of each single tobacco product. By contrast, the EPA Federal Reference Methods (FRMs) for measuring PM often rest on 24 hours sample collection of PM₁₀ and PM_2.5, but not of PM₁, followed by gravimetric measurement of the collected PM, or the likewise real-time measurement device tapered element oscillating microbalance (TEOM) monitor.^{47 48} The European standard EN 12341 for the determination of PM₁₀ and PM _2.5 is also a gravimetric measurement method.⁴⁹ One listed FRM is an automated equivalent method with the Grimm model EDM 180, which measures PM via light scattering.⁴⁸ Several studies showed that the measurement results of a Grimm model 1.107, 1.108 or 1.109 were very similar to the results of TEOM Monitors, Grimm model EDM 180 or gravimetric methods.^{47 50} Fromme et al concluded in 2007 that gravimetric methods generated higher results than laser aerosol spectrometer but with a high correlation of the rank order of measured values.⁵¹ Thus, the measured values of the used Grimm model 1.109 can be recognised as valid, but it is very important not to change the method of measurement during a study.

A limitation of the applied AETSE is the inability to imitate SHS and the smoking behaviour of humans exactly, because in the respiratory tract the inhaled mainstream smoke is humidified and the exhaled smoke particles are approximately 1.5-fold larger due to hygroscopic growth.^{52 53} By using the AETSE, it is not possible to differentiate between inhaled and exhaled mainstream smoke, but it should be emphasised that SHS consists only of approximately 15% mainstream smoke and approximately 85% side-stream smoke.^{54 55} However, the AETSE is able to imitate side-stream smoke as realistically as possible. Hence, the measured PM emissions were very similar to SHS.

It is worth pointing out that reproducible results had been ensured by avoiding inter-individual deviations without the exposure of a test person to any health risk. The used modified smoking regime differed from the already existing protocols like, for example, ISO/TR 17219⁵⁶ or the standard operating procedure for intense smoking of cigarettes by the WHO.⁵⁷ At this point, it must be said that no ‘gold standard’ exists for smoking regimes.^58–61 Moreover, this study as well as all previous ToPIQ studies focused on data comparison to the 3R4F reference cigarette and not on absolute numbers. Therefore, the use of the modified protocol and the application of AETSE can be considered as valid.

In conclusion, this study showed repeatedly the massive increase of PM in enclosed rooms in consequence of smoking of tobacco products. Although the reduction of PM emissions due to the absence of additives in tobacco products should be verified in further studies.