PHYSICAL AND CHEMICAL CHARACTERISTICS OF SMALL-CIGAR BRANDS DISTRIBUTED ON BULGARIAN MARKET

Introduction

Current and future regulatory activities, such as the expansion of smoke-free environment, health warnings and taxation, undoubtedly reproduce and will continue to reproduce as either an increase or decrease in the consumption of cigarettes and other smoking products. This could play a decisive role in the future shaping and structuring of Bulgarian tobacco products market. The pressure on the consumers creates certain market niches for alternative sources of physiological nicotine delivery. The review and analysis of specialized data show that the growing regulation and social pressure on cigarette consumption contribute to the increase in the demand of other smoking products – RYO or MYO tobacco, cigars, small-cigars, water pipe (hookah), pipes, e-cigarettes, etc. The WHO Framework Convention on Tobacco Control, seeking a reduction of the harmful consequences of tobacco consumption, largely focuses on cigarette regulation and related health and other effects. The Food and Drug Administration (FDA) as a rulemaking institution in charge of the regulation and control of tobacco products market in the USA, has adopted a series of measures for the achievement of similar goals. In September 2009 FDA banned some flavor additives to cigarettes, but the production, sale and distribution of flavored cigars and small-cigars is still allowed. In July 2010 the Canadian government banned the distribution of flavored small-cigars and set the requirement that non-flavored small-cigars must be sold in unit packets of less than 20 pieces. Independent researchers [1, 2, 3, 4] point out that the attractiveness of cigars and small-cigars and the resulting growth in their consumption among younger people, a tendency of great concern, could be attributed mainly to the flavor additives. Taxation policies have also a certain impact on the segmentation and development of smoking products market. Cigars and cigar-like smoking products are taxed fiscally at a slower rate than cigarettes and are legally regulated in a somewhat different pattern.

With the implementation of Directive 2014/40/EU, the member states are given the opportunity to bring into force national laws, regulations and administrative provisions necessary to comply with it by May 2016, taking as a base a high level of protection of human health, especially for young people and accounting any new development based on scientific facts. Therefore, priority targets for scientific research become smoking products other than cigarettes, which show substantial market share and consumption, but have yet not been covered by legal regulation on internationally adopted standard base in terms of maximum emission levels of tar, nicotine, carbon monoxide and other smoke components. In that line, special attention is being paid to the harmful consequences on human health caused by heavy metals and other toxic mineral elements found in tobacco smoke [5, 6].

Above observations, as well as the changed status quo of country’s consumption of smoking products, which until recently has been almost totally dominated by cigarettes, define the necessity of current study. The aim of the study is to investigate the physical and chemical characteristics of cigar and small-cigar brands officially distributed on Bulgarian market.

Materials and methods of analysis

Objects in the investigation are two brands of cigars and six brands of small-cigars commercially sold on the market, as follows: „Villiger Premium Aromatic 8” (VPA-8); „Villiger Premium Dark Chocolate Filter” (VPDCHF); „Villiger Premium Coffee Filter” (VPCF); „Villiger Premium Cherry Filter” (VPCHF); „Villiger Premium Honey Filter” (VPHF); „Villiger Premium Whisky Filter” (VPWHF); „Villiger Premium Vanilla Filter” (VPVF); „Villiger Premium Sumatra 7” (VPS-7). Selection of cigars and small-cigars as objects for the investigation has been done on the grounds of their sensory profiles, making such smoking products highly attractive to the most vulnerable population groups – young people and those choosing new smoking products in the search of “safer” or “less harmful” alternatives of conventional cigarettes. The study includes the determination of the following characteristics of cigar and small-cigar samples:

Visual assessment: appearance and structural elements.
Physical characteristics: weight (g) – by weighing of conditioned samples, on a Sartorius 1702 scale, with precision 0,001 g; length (mm) – by direct measuring, with an electronic gauge meter, precision 0,01 mm; tipping paper length (mm) – by direct measuring, with an electronic gauge meter, precision 0,01 mm; filter plug length (mm) – by direct measuring with an electronic gauge meter, precision 0,01 mm; diameter (mm) – on Filtrona Beta LaserMike, according to ISO 2971; draw resistance of cigars/small-cigars and filter plugs (mm WG) – on Borgwaldt draw resistance meter (Borgwaldt KC, Germany), according to ISO 6565; firmness (mm) – on a Borgwaldt densimeter (Borgwaldt KC, Germany), according to Bulgarian state standard (BSS) 16258; number of puffs per cigar/small-cigar – by smoking on an automated linear smoking machine Filtrona 302, according to ISO
Tobacco chemical composition: nicotine (%) – ISO 15152; reducing sugars (%) – ISO 15154; total nitrogen (%) – BSS 15836; ash (%) – ISO 2817; ammonia (%) – by continuous flow analysis, according to a method developed by the Tobacco and Tobacco Products Institute, Plovdiv; рН – BSS 13306-76; heavy metals (Zn, Cu, Pb, Cd) (mg/kg) – on an atomic absorption spectrometer „Spektra AA 220” (Varian, Australia).
Smoke emissions: nicotine (mg/cig) – ISO 10315; tar (mg/cig) – ISO 4387; carbon monoxide (CO) (mg/cig) – ISO 8454, by smoking on a linear analytical smoking machine Filtrona
Smoking evaluation: by a smoking panel, applying direct comparison and ranking methods. Individual results are statistically processed to determine the relative ranking coefficient, the rank coefficient, and Kendall’s coefficient of concordance (W) (together with F-test for testing its statistical significance).

Results and discussion

Visual inspection. Inspected and described were the exterior and structural elements of cigars and small-cigars. Cigars of VPA-8 and VPS-7 brands were individually wrapped and placed 5 pieces in a cardboard hard pack (slide box). They consisted of three layers – filler, binder and wrapper. Wrapper leaves were medium brown, thin, smooth, and thinly-veined. Binder layer was of reconstituted sheet. Both cigars were short filler type. The filler of VPA-8 sample represented mainly leaf shreds and cut stems, with only individual particles of unprocessed stems. The filler of VPS-7 cigars was predominantly of large size leaf strips with few compact tobacco stems. Both cigars were without filter tips, with cylindrical body (“parejo”) and tight head and foot. VPA-8 had two three-row longitudinal perforations (ventilated type), while VPS-7 cigars were without perforation.

The small-cigars of „Villiger Premium” family – VPDCHF, VPCF, VPCHF, VPHF, VPWHF and VPVF, were packed in hard cardboard boxes (flap-top), with 10 pieces in each consumer pack. All small-cigars were composed of three types of tobacco – filler, binder and wrapper. The wrapper leaves were with the required high quality features – even brown colored, thin, smooth and supple, with thin and fine veins. The binder was made of reconstituted tobacco sheet in all of the brand varieties. The filler was composed of cut tobacco (tobacco shreds) and cut processed tobacco stems with only a limited number of unprocessed stems. Only in VPCF brand the filler incorporated small-sized lamina strips and individual tobacco shreds. All of the studied small-cigars were with cylindrical shape, with two three-row longitudinal perforations, and a filter section. Filters were double, “sandwich” type, with two segments — cellulose acetate and carbon.

Physical characteristics of cigars and small-cigars

The results from the determination of the physical indexes of cigar and small-cigar samples are presented in table 1.

Table 1

Physical indexes of cigar and small-cigar brands

Brand	Weight	Length			Diameter	Draw resistance		Firmness
	Weight	Total	Tipping paper	Filter plug	Diameter	Total	Filter plug	Firmness
	g	mm	mm	mm	mm	mm WG	mm WG	mm
VPA—8	3.80	106.47	—	—	11.99	—	—	—
VPS—7	4.76	101.57	—	—	14.30	—	—	—
VPDCHF	1.38	89.61	30.42	20.43	8.22	102.92	35.08	7.03
VPCF	1.35	89.76	30.45	20.47	8.26	89.83	34.33	7.05
VPCHF	1.37	89.97	29.56	19.27	8.22	88.25	29.25	7.09
VPHF	1.30	89.68	29.86	19.91	8.33	89.92	30.08	6.90
VPWHF	1.29	89.52	29.43	20.05	8.26	71.75	29.17	6.56
VPVF	1.39	89.64	26.27	19.91	8.16	85.14	34.00	6.65

Comparing the two cigar brands in the study – VPA-8 and VPS-7, it is seen that they differ in physical dimensions and characteristics. VPA-8 is with smaller length and diameter, but with greater total weight than VPS-7.

The results about small-cigars reveal a lack of significant differences in their physical characteristics – weight, diameter and length (total, of the tipping paper and of the filter itself), with the exception of VPVF tipping paper, which is considerably shorter (26.27 mm, 29.30 % of the total length of the product). Wider variations are observed for the index draw resistance of small-cigars, being in the range from 71.75 mm WG for VPWHF to 102.92 mm WG for VPDCHF. The draw resistances of the remaining four brands come near to the mean of the specified range – VPVF being slightly below, while VPCF, VPCHF and VPHF being slightly above the mean value, with no significant deviations among them. Filter plug draw resistance is maximal for VPDCHF (35.08 mm WG), followed by VPCF (34.33 mm WG) and VPVF (34.00 mm WG), and lower for the remaining three brands – VPHF (30.08 mm WG), VPCHF (29.25 mm WG) and VPWHF (29.17 mm WG). The firmness of the samples shows slight variation – from 6.56 mm and 6.65 mm for VPWHF and VPVF to 7.03÷7.09 mm for the other three brands, the variations among the brands being insignificant in terms of physical stability of the individual products.

As a conclusion, these results suggest that the studied small-cigar brands show no significant differences as regards physical dimensions and firmness (with the exception of VPVF tipping paper length), while the two cigar brands are considerably different. The highest values of draw resistance are found for VPDCHF, and the lowest – for VPWHF small-cigars, with the rest of the brands showing medium values.

Chemical composition of tobaccos

Results about the basic chemical indexes of filler and binder tobaccos in the studied cigar and small-cigar brands are displayed in table 2.

Table 2

Chemical composition of filler (a) and binder (b) tobaccos

Index	Samples
	VPA—8		VPDCHF		VPCF		VPCHF		VPHF		VPWHF		VPVF		VPS—7
	a	b	а	b	а	b	а	b	а	b	а	b	а	b	а	b
Nicotine, %	2.08	1.42	2.05	1.09	1.59	0.95	1.59	0.89	1.68	1.00	1.61	0.93	2.24	1.03	1.48	0.88
Sugars, %	10.60	0.72	7.90	2.38	10.20	2.64	10.50	2.24	10.50	1.70	11.60	2.40	10.30	2.50	0.48	0.63
Nitrogen,%	2.32	—	2.48	—	2.36	—	2.28	—	2.39	—	2.31	—	2.25	—	3.72	—
Ash, %	11.01	12.87	13.22	—	12.30	—	11.90	—	11.95	—	12.00	12.11	12.90	13.15	18.20	13.91
NH₃, %	0.04	—	0.07	—	0.05	—	0.04	—	0.07	0.02	0.05	0.03	0.08	—	0.02	0.17
pH	5.20	—	5.20	—	5.23	—	5.17	—	5.20	—	5.20	—	5.30	—	6.61	—

The highest nicotine content in filler tobaccos is found for VPVF small-cigars (2.24%), and the lowest – for VPS-7 cigar (1.48%). Above the threshold of 2 % nicotine are also the filler tobaccos in VPA-8 cigars and VPDCHF small-cigars, with no significant differences between them. The rest of the brands are with medium nicotine content, varying in the range between 1.59 % and 1.68 %. As regards reducing sugars content, the variations are considerable – from 0.48 % in VPS-7 filler to 11.60% in VPWHF filler. Among the remaining brands there are no significant differences in reducing sugar content (10.20÷10.60 %), with the only exception of VPDCHF (7.90 %). Total nitrogen is maximal in the filler of VPS-7 cigar – 3.72 %, while for the rest of the samples the values are between 2.25 % and 2.48 %. Tobaccos composing the filler of VPS-7 have the highest total content of mineral substances (18.20 %), and these of VPA-8 – the lowest (11.01%). The rest of the samples show ash levels coming near to the minimum, with no significant differences observed among them. Ammonia varies among brands, but remains in a narrow range – from 0.02 % (VPS-7) to 0.08% (VPVF). With respect to ammonia, the remaining six samples can be grouped in couples, as follows: VPDCHF and VPHF with 0.07 % content; VPCF and VPWHF (0.05 %) and finally – VPA-8 and VPCHF (0.04 %). pH values show no significant differences, with the exception of VPS-7, all values being below 7.00, which is in good agreement with the findings by other researchers [7].

Considering the results obtained for the chemical composition of the binders (reconstituted tobacco sheet) of the investigated brands it is found that the highest nicotine content is in the VPA-8 brand (1.42 %), and the lowest – in VPS-7 (0.88 %) and VPCHF (0.89 %) brands, with the rest of the samples approaching 1.00 % nicotine content (0.93÷1.09 %). The content of reducing sugars in the binders varies from 0.63 % (VPS-7) to 2.64 % (VPCF). VPA-8 cigar binder is with reducing sugars content (0.72 %) coming near to the other cigar brand in the study (VPS-7). The small-cigar brands representation is characterized by generally higher reducing sugars content (2.24÷2.64 %), except for VPHF, which is placed between the two groups (1.70 %). Results in table 1 expectedly show substantial differences in nicotine and reducing sugars content between filler and binder tobaccos in all of the studied brands – considerably higher levels of both indexes are found in the filler tobacco blends. Although not individually analyzed, the presence of significant (not typical of dark tobaccos) concentrations of sugars in the filler of all flavored brands (both cigar and small-cigar) could probably be connected to specific tobacco processing (additives, casings, flavors). Mineral matter content of binder sheet varies from 12.11 % (VPWHF) to 13.91 % (VPS-7), with no significant differentiation among the brands. Ammonia level is the highest in VPS-7 binder (0.17 %), while in VPHF and VPWHF it is 0.02÷0.03 %.

The overall assessment of the chemical composition of tobaccos constituting the filler part of the studied cigars and small-cigars reveals no clear tendencies in the distribution of the registered indexes. A more specific profile of the chemical composition has been found for the tobaccos composing the filler of VPS-7 cigar, having a medium content of nicotine, minimum – of reducing sugars and ammonia, and maximum – of total nitrogen and ash, if compared to the rest of the studied brands. The filler of the other cigar brand in the study – VPA-8, shows no distinct differences from the characteristics of the studied small-cigar brands.

The chemical composition of the binders used in studied cigars and small-cigars significantly distinguishes VPS-7 cigar from the rest of the brands – representing the minimum in nicotine and reducing sugars content, and the maximum in ash and ammonia content. VPA-8 cigar is characterized with the highest level of nicotine, close to the minimal — of reducing sugars, and medium – of mineral matter. Regarding the chemical indexes of the binders in the small-cigar fragment, no significant differences have been found among the studied six brands

Wrapper leaves included in the studied brands have been analyzed only in regard to nicotine content, and the results are presented on Fig. 1.

Fig. 1. Nicotine in the wrapper of cigar and small-cigar brands

As seen from the figure, the two cigar brands occupy the extremes of the range – the highest nicotine levels are found in VPA-8 wrapper (1.40 %), and the lowest in VPS-7 wrapper (0.90 %). Very close to VPS-7 cigar come the nicotine contents of VPVF and VPCHF small-cigar wrappers, respectively 0.91 % and 0.92 %. The nicotine content in the wrapper leaves of the remaining small-cigar samples is with medium values, ranging from 1.01 % to 1.09 %.

The accumulation of heavy metals in tobacco leaves is a subject of special concern, since the exposure to these potent toxicants and carcinogens has proven negative effect on smokers’ health. The content of heavy metals in tobacco leaves is variable, depending on the growing conditions – soil composition and properties, air pollution, but also on the type and variety of tobacco [8, 9, 10]. Table 3 presents data about heavy metals content in tobacco filler of the studied brands.

Table 3

Heavy metals (mg/kg) in tobacco filler of the studied brands

Brand	Zn	Cu	Pb	Cd
VPA—8	19.05	9.38	5.50	0.13
VPDCHF	36.70	12.60	6.50	1.58
VPCF	32.50	8.00	0.75	0.28
VPCHF	25.65	6.65	1.25	0.35
VPHF	18.02	6.35	0	0.43
VPWHF	15.25	5.70	0.25	0.33
VPVF	14.19	12.80	2.75	1.08
VPS—7	52.54	18.80	1.75	1.20

Results show that Zn levels vary in a relatively broad range – from 14.19 mg/kg (VPVF) to 52.54 mg/kg (VPS-7). Two groups of brands can be formed with regard to Zn levels – the first including VPWHF, VPHF and VPA-8 (< 20 mg/kg, closer to the minimum), and the second including VPCHF, VPCF and VPDCHF (> 25 mg/kg, closer to the maximum). The content of Cu is maximal in VPS-7 (18.80 mg/kg), followed by VPVF (12.80 mg/kg) and VPDCHF (12.60 mg/kg), and minimal – in VPWHF (5.70 mg/kg). Relatively close to the minimum are Cu levels in VPHF (6.35 mg/kg) and VPCHF (6.65 mg/kg). Pb content is highest in VPDCHF small-cigars (6.50 mg/kg) and VPA-8 cigars (5.50 mg/kg). Pb distribution among the remaining brands is from 0.25 mg/kg to 2.75 mg/kg, while in VPHF small-cigar filler no Pb has been detected. Cd varied in a relatively narrower range – from 0.13 mg/kg (VPA-8) to 1.58 mg/kg (VPDCHF). Closer to the upper limit of the range are Cd levels in VPS-7 (1.20 mg/kg) and VPVF (1.08 mg/kg), while the rest of the brands are with Cd content below 0.50 mg/kg. The values observed for all elements and brands correspond to those obtained by other authors for other types of tobacco (flue-cured Virginia, air-cured Burley, oriental) [9, 10].

Summarized results about heavy metal content in the filler of the selected brands reveal that VPS-7 cigars are with the highest levels of Zn and Cu, medium – of Pb, and near to maximum level of Cd. VPA-8 filler shows lower levels of Zn and Cd, medium – of Cu, and higher – of Pb. No Pb is detected in VPHF small-cigar filler.

Smoke emissions

The results from the analysis of smoke chemical composition are presented on figure 2.

Fig. 2. Smoke emissions from cigar and small-cigar brands

Nicotine in the smoke of studied small-cigar brands is above 2.50 mg/cig, respectively – minimal in VPCF (2.66 mg/cig) and maximal in VPDCHF (3.72 mg/cig). The rest of the brands show no significant differences in smoke nicotine, with values varying from 3.26 mg/cig to 3.42 mg/cig. Tar emissions are high, and varying in a relatively wide range – from 41.39 mg/cig in VPVF to 60.71 mg/cig in VPCHF. Tar levels approaching range maximum are registered for VPWHF, VPHF and VPDCHF brands, while that of VPCF brand is closer to the minimum. CO content also varies largely – from 17.69 mg/cig (VPVF) to 46.13 mg/cig (VPDCHF). Relatively close to the lower range limit comes VPWHF (22.39 mg/cig), while all of the remaining brands have higher CO levels (33.00÷38.76 mg/cig).

The general characteristics of smoke emissions reveal that VPDCHF small-cigars are with the highest levels of nicotine and CO, and VPCHF – of tar. On the other end, VPCF brand shows minimal levels of smoke nicotine, and VPVF – of tar and CO.

Data confirm that mainstream smoke from cigar-like products is with bigger content of nicotine, tar and CO compared to cigarettes [11, 12, 13].

Results about the number of puffs per item under the specified smoking conditions are presented on figure 3.

Fig. 3. Number of puffs for small-cigar brands

Puff number value is smallest for VPVF and biggest – for VPCHF brand. VPDCHF practically approaches the maximum, while VPCF is closer to the minimum of the range. VPHF and VPWHF show no differences (puff number 16.0). Butt length for all of the studied brands is fixed to 28 mm, with the exclusion of VPVF with butt length of 30 mm.

Smoking assessment

Cigars/small-cigars have been assessed by a 5-member smoking panel in terms of general smoking quality, i.e. the sensory perception of smoke aroma, taste and strength. The individual ranks given by the panelists and the final rating of the samples are presented in tables 4 and 5, together with some statistical indexes. Samples have been grouped in two series for smoking assessment (by paired comparison and ranking), and the statistical agreement of panelists’ ranks has been verified by Kendall’s coefficient of concordance (W), tested for statistical significance by F-test to verify the degree of unanimity among the individual ranks.

Considering the results from the smoking evaluation of brands in the first scheme (table 4), it can be seen that the highest rank is attributed to VPCF, followed by VPDCHF and VPCHF, and the lowest rank – to VPHF. Statistical criteria verify the unanimity of results and the significance of final ranking (W=0.55; F_c=4.89; F_.05=3.82, at f₁=2.6; f₂=10.4). Therefore, it could be concluded that there are significantly perceptible differences between the four small-cigar brands in the series, and that VPCF turn to be superior, while VPHF – inferior, in the manifestation of smoking quality.

Table 4.

Smoking evaluation of cigar and small-cigar brands – series 1

Panelist — i	Ranks by panelist — j
Panelist — i	VPCF	VPDCHF	VPHF	VPCHF
1	2	1	3.5	3.5
2	1	2	3.5	3.5
3	1	3	4	2
4	1	4	3	2
5	1	2	3	4
∑X_ij	6	12	17	15
Relative ranking coefficient	0.12	0.24	0.34	0.30
Rank coefficient	1	0.50	0.35	0.40
Ranking	1	2	4	3

The statistical processing of the results from the smoking evaluation of the second series (table 5) verifies that the observed differences and the respective ranking of the samples are statistically significant (W=0.68; F_c=8.50; F_.05=3.82, at f₁=2.6, f₂=10.4). On these grounds, it could be accepted that ranks reflect the actual smoking quality level of the brands, rated in the following order: VPWHF, VPA-8, VPS-7 and VPVF. Therefore, the two cigar brands – VRA-8 and VPS-7, are inferior in smoking quality to VPWHF small-cigars, but are still ranked higher than VPVF small-cigars.

Table 5

Smoking evaluation of cigar and small-cigar brands – series 2

Panelist — i	Ranks by panelist — j
Panelist — i	VPS-7	VPWHF	VPA-8	VPVF
1	2	1	3	4
2	4	1	2	3
3	3	1	2	4
4	1	2	3	4
5	3	1	2	4
∑X_ij	13	6	12	19
Relative ranking coefficient	0.26	0.12	0.24	0.38
Rank coefficient	0.46	1	0.50	0.32
Ranking	3	1	2	4

Conclusions

Results from the investigation of commercial cigar and small-cigar brands on Bulgarian market give grounds for the following conclusions:

There are no considerable differences among small-cigar brands in terms of physical characteristics, with the exception of “Villiger Premium Vanilla Filter”, having the smallest length of tipping paper. „Villiger Premium Dark Chocolate Filter” has the greatest values of draw resistance, and „Villiger Premium Whisky Filter” – the smallest.
There is no one-directional correlation between the indexes of the chemical composition of the tobaccos used in the filler of the studied cigar and small-cigar brands.
More significant differences have been observed in the chemical composition of the filler and the binder of „Villiger Premium Sumatra 7” cigars, and insignificant differences – for the other brands. The highest nicotine content is found in the wrapper of „Villiger Premium Aromatic 8” cigars, and the lowest – in „Villiger Premium Sumatra 7” cigar wrapper.
„Villiger Premium Sumatra 7” cigars are with high levels of zinc and copper, medium – of lead, and near to maximum level of cadmium in the filler. „Villiger Premium Aromatic 8” are with near to the minimum levels of Zn and Cd, medium – of Cu, and higher – of Pb. No presence of Pb has been found in „Villiger Premium Honey Filter” small-cigar filler.
The general assessment of smoke emissions reveals that „Villiger Premium Dark Chocolate Filter” small-cigars are with the highest nicotine and CO. The highest tar content is found in „Villiger Premium Cherry Filter”.
It is confirmed that mainstream smoke from cigar-like products contains more nicotine, tar and CO compared to cigarettes.
There are statistically significant differences in the smoking profiles of the studied cigar and small-cigar brands. Sensory evaluation and grading reveals that „Villiger Premium Coffee Filter” and „Villiger Premium Whisky Filter” represent the best smoking quality. „Villiger Premium Aromatic 8” and „Villiger Premium Sumatra 7” cigars are inferior in smoking quality to „Villiger Premium Whisky Filter” small-cigars, but are still with better smoking profile than „Villiger Premium Vanilla Filter” small-cigars.

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Henningfield E., Fant, Radzius A., Frost S. Nicotine concentration, smoke pH and whole tobacco aqueous pH of some cigar brands and types popular in the United States. Nicotine & Tobacco Research, 1999. – vol.1 (2). – P.163-168.
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Zapryanova P., Bozhinova R. Nutrient and heavy metal content in plant organs of oriental and Virginia tobacco. Ecology & Future, 2009. – vol.1. – P.20-29.
Bryan P., Evans S. Cigars, cigarillos and Journal of Ethnicity in Substance Abuse, 2004. – vol.2 (4). – P.63-76.
O’Connor R. Non-cigarette tobacco products: what have we learnt and where are we headed? Control, 2012. – vol.21 (2). – P.181-190.
Rickert, Trivedi A., Momin R., Wagstaff W., Lauterbach J. Mutagenic, cytotoxic, and genotoxic properties of tobacco smoke produced by cigarillos available on the Canadian market. Regulatory Toxicology and Pharmacology, 2011. – vol.61 (2). – P.199-209.[schema type=»book» name=»PHYSICAL AND CHEMICAL CHARACTERISTICS OF SMALL-CIGAR BRANDS DISTRIBUTED ON BULGARIAN MARKET» description=»The aim of the study is to investigate the physical and chemical characteristics of cigar and small-cigar brands officially distributed on the national market. Basic physical and chemical indexes of cigars, tobacco and smoke have been determined, and smoking assessment tests have been carried out. » author=»Nikolova Violeta Viktorova, Popova Venelina Todorova, Nikolov Nikolay Petkov» publisher=»БАСАРАНОВИЧ ЕКАТЕРИНА» pubdate=»2017-04-14″ edition=»ЕВРАЗИЙСКИЙ СОЮЗ УЧЕНЫХ_30.04.2015_4(13)» ebook=»yes» ]

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