Environmental Chemistry Letters

, Volume 13, Issue 4, pp 465–471

Higher cytotoxicity and genotoxicity of burning incense than cigarette

  • R. Zhou
  • Q. An
  • X. W. Pan
  • B. Yang
  • J. Hu
  • Y. H. Wang
Original Paper

DOI: 10.1007/s10311-015-0521-7

Cite this article as:
Zhou, R., An, Q., Pan, X.W. et al. Environ Chem Lett (2015) 13: 465. doi:10.1007/s10311-015-0521-7

Abstract

Hazardous particulates and volatiles produced by incense burning accumulate in the indoor atmosphere, where they pose a health risk, entering the human body via the respiratory system. Yet, few studies have focused on the effects of the total particulate matter from incense burning on human health. Here, we evaluate the health risks associated with the total particulate matter generated from burning incense indoors for the first time. The total particulate matter and major chemical components of two types of incense smoke were characterized using an electrical low pressure impactor and gas chromatography coupled with mass spectrometry. Their genotoxicity and cytotoxicity were compared with mainstream tobacco smoke using in vitro assays. Our results show that both the particulate number and mass of incense smoke were dominated by ultrafine to fine particles. In addition, many aromatic, irritant, and toxic compounds were identified in the particulate fraction. In vitro assessments showed that the genotoxicity of the particulate matter from one particular incense sample was higher than the reference cigarette sample with the same dose. All particulate matter fractions from the incense investigated were found to possess greater cytotoxicity on Chinese hamster ovary cells than smoke from the reference cigarette. Collective assessment of these data will affect the evaluation of incense products and facilitate measures to reduce exposure to their smoke. Clearly, there needs to be greater awareness and management of the health risks associated with burning incense in indoor environments.

Keywords

Total particulate matterIncense smokeChemical compositionCytotoxicityGenotoxicity

Introduction

More and more attention has been placed on researching air pollution in indoor environments because people spend most of their time indoors (Ott 1985; Nardini et al. 1994; Gianluigi et al. 2014). Indoor air pollution results from specific indoor activities, such as cooking, smoking, and burning incense (Löforth et al. 1991). Although incense burning is one of the major indoor air pollution sources, it has received little attention because of its regionalism, despite evidence that shows burning incense is potentially hazardous to human health (Chen and Lee 1996; Lee and Wang 2004). Epidemiological investigations have demonstrated that the combustion of incense is correlated with lung cancer (Maclennan et al. 1977), childhood leukemia (Lowengard et al. 1987), and brain tumors (Preston-Martin et al. 1982).

Incense burning is a traditional and common practice in many families and in most temples in Asia for religious reasons and because of its pleasant smell. The raw materials used to make incenses are diverse, but two of the most common ingredients are agarwood from Aquilaria agallocha (Lour.) Roxb. ex Finl. and sandalwood tree resin from Santalum album Linn. Two incense types with these two components were selected for our study. There is a huge amount of particulate matter generated because of incomplete combustion, leading to fine particulates effectively being deposited into the lungs, eliciting an adverse inflammatory response (Bitterle et al. 2006). The characteristics of incense smoke vary with the constituents of the incense stick (Yang et al. 2006), but particulate-bound chemicals are of the greatest concern because they easily enter the alveolar region of the respiratory system, resulting in biological effects (Liou et al. 2008; Song and Mei 2013). For example, the toxicity of particulate matter induced by combustion of incense was shown to be mutagenic in Salmonella typhimurium bacterium (Rasmussen1987; Chang et al. 1997), as well as cytotoxic to various cells in vitro (Chuang et al. 2013; Bitterle et al. 2006). Yet, there are few data to compare with cigarette smoke effects.

The purpose of this study is to assess the hazards associated with two types of incense smoke in the home and to compare these to mainstream studies of cigarette smoke for the first time. To do this, we used a fishtail chimney to collect the total particulate matter from incense smoke to obtain comprehensive data on the fine and ultrafine particle fractions. We also used an electrical low pressure impactor to determine particle distributions and gravimetric measurements. We characterized the major chemical emission components in the particulate matter using gas chromatography coupled with mass spectrometry (GC–MS). Finally, we evaluated the genotoxicity and cytotoxicity responses to the total particulate matter in vitro and compared these with cigarette smoke responses.

Experimental

Particle distribution and gravimetric measurements

To determine particle distribution and gravimetric measurements, four incense sticks (samples A–D) were burned in a combustion system. All samples were kept under a conditioned atmosphere, with a temperature of 22 ± 1 °C and a relative humidity of 60 ± 2 %. The combustion system is equipped with a fishtail chimney, an air pump (V-500; BUCHI Labortechnik AG, Switzerland), a flow controller (RMA-21-SSV; Dwyer instruments Inc, IN, USA), a 20-times gas dilution system (Dl-1000; Dekati Ltd, Finland), and an electrical low pressure impactor (97 2E; Dekati Ltd), as outlined in Fig. 1. The fishtail chimney was custom-built according to our requirements. The test atmosphere was 22 ± 2 °C and 60 ± 5 % relative humidity. The electrical low pressure impactor operates at 10 L/min flow rate and measures particle sizes ranging from 7 nm to 10 µm. The charged particles in the incense smoke were collected onto the 13 collection plates of the impactor, and their aerodynamic diameters were recorded on 12 electrometer channels. These measurements were processed with the electrical low pressure impactor XLS4.05 software (Dekati Ltd). Measurements were carried out in three independent experiments. Each experiment involved 45 min of incense burning. All data are expressed as mean ± SD (n = 3).
Fig. 1

Measurement system for characterizing incense smoke total particulate matter. Total particulate matter was collected onto glass-fiber filter pads placed on the fishtail chimney, with the air tube connected to the 20-times gas dilution system shut off. ELPI electrical low pressure impactor

Total particulate matter collection

To collect total particulate matter, four incense sticks were burned inside the fishtail chimney, equipped with a glass-fiber filter pad, as shown in Fig. 1. During collection, the air tube connected to the 20-times gas dilution system was shut down, and the air pump was turned on, giving an air velocity in the fishtail chimney of 200 ± 30 mm/s. The smoke from a cigarette (3R4F reference cigarette, University of Kentucky; sample E, this study) was measured on a smoking machine, according to ISO 3308:2000.

Chemical analysis

After combustion, the contents of each filter were extracted three times with 30 mL dichloromethane under ultrasonic agitation for 30 min, and then 100 ng of 2-phenylethyl propionate (purity 99.8 %; Fluka, Buchs, Switzerland) was added as an internal standard, followed by reduction to approximately 1 mL by rotary evaporation. Quantitative analysis of the samples was conducted using gas chromatography with flame ionization detection (Agilent 6890 N; Agilent Technologies, Palo Alto, CA, USA). The gas chromatographer was equipped with an DB-5MS capillary column (5 %-phenylmethylpolysiloxane, 60 m × 0.25 μm i.d. × 0.25 μm; Agilent Technologies). Helium was the carrier gas, with a flow rate of 1.0 mL/min. One microliter of each sample was injected using the pulsed splitless mode and an inlet temperature of 280 °C. The oven was programmed to heat from 40 °C to a maximum temperature of 280 °C at a rate of 1.5 °C/min and kept at 280 °C for 20 min. The volatile compounds were identified using gas chromatography–mass spectrometry (GC: Agilent 6890N; MS: Agilent 5975; Agilent Technologies) by comparing spectral data with the National Institute of Standards and Technology chemical library (version 2011).

In vitro assay for mutagenicity

The filters were extracted with dimethyl sulfoxide, and standard procedures were followed, as described in Maron and Ames (1983) and recommended by the Organization for Economic Co-operation and Development’s guidelines for testing of chemicals (OECD 1997). Assessments were carried out with the Ames test, using Salmonella tester strains TA98, TA100 and TA102. For each sample, three doses were prepared and assayed, and each dose was plated in triplicate. Every sample was assayed with and without the metabolic activation system (S9). The results are expressed as the mean of the number of revertants/plate ± SD.

In vitro assay for cytotoxicity

To assess cytotoxicity, a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay (Ulukaya et al. 2008) was conducted on the dimethyl sulfoxide extracts from the filters. Chinese hamster ovary cells were cultivated in 50 mL of Dulbecco’s modified Eagle’s medium, supplemented with 10 % fetal bovine serum and 105 U/L gentamicin sulfate at 37 °C and 5 % CO2. This was seeded in 96-well plates (100 μL per well of 1 × 105 cells/mL) until the cells attached. The cells were then treated with culture medium (control) and a range of extraction concentrations from 0 to 300 μg/mL for 24 h. Each concentration was tested in replicates of four, and the results give the mean of the three independent experiments. After the cells were incubated with MTT for another 4 h at 37 °C, the medium was removed and the crystal formazan dye was solubilized in 150 μL dimethyl sulphoxide. Absorbance was measured at 490 nm using the Microplate Reader (imark680, Bio-Rad, Hercules, CA, USA), and the half maximal inhibitory concentrations were calculated by probit regression.

Statistical analysis

Statistical analysis was carried out using SPSS statistics 17.0 (IBM, Armonk, NY, USA). All analyses were one-factor analysis of variance. p < 0.05 was used to identify statistically significant differences.

Results and discussion

Particle size distribution

The particle size distributions for four incense samples were recorded by the electrical low pressure impactor. The aerodynamic diameters of particulates emitted by these four samples were all below 5 µm. Particles less than 2.5 µm in size contributed heavily to the total particulate mass, with their numbers accounting for more than 99 % and their mass for more than 90 % of the total particulate matter. Particles smaller than 0.1 µm are labeled ultrafine particles, and those between 0.1 and 2.5 µm are termed fine particles (Wichmann et al. 2000; Shaocai et al. 2014). Wichmann et al. (2000) concluded that both fine and ultrafine particles have independent effects on mortality at ambient concentrations. Epidemiological and toxicological studies showed that inhalation of fine and ultrafine particles causes adverse health effects, related to various factors, including mass, surface area, and number concentrations of particles (Brouwer et al. 2004). The data obtained from this study clearly showed that the particulate number and mass measured in incense smoke were dominated by ultrafine and fine particles, likely to cause adverse health effects.

Chemical composition

Sixty-four compounds were identified in the particles from the four incense smoke samples using National Institute of Standards and Technology library matches (Table 1). Only compounds with matchings of 90 % or higher were accepted. A number of compounds occurred in all four samples, including monoterpenes, methoxylated phenolics, two hexose dehydration compounds, as well as other highly volatile compounds. Monoterpenes are fragrant and common components of essential oils, while the methoxylated phenolics originate from the combustion of lignin and contribute to the typical burnt smell associated with incense (Staub et al. 2011). The highly volatile compounds common to all four samples were mostly irritants and hypotoxic. There also were some hypertoxic compounds detected in one or two samples, for example ethyl cyanoacetate in sample B and 2-butenal in sample D. However, the compounds detected in this study represent only the most abundant and most easily detectable compounds, rather than all components of the smoke.
Table 1

Volatile organic compounds identified in the smoke of the four different incense sticks

RT (min)a

Name

Matchb

Content (μg/g)c

A

B

C

D

4.847

2-Chloro-2-methylbutane

972

164.55 ± 10.60

274.81 ± 15.69

141.86 ± 15.96

306.42 ± 12.71

5.106

tert-Amyl methyl ether

931

13.10 ± 0.96

22.02 ± 0.60

10.87 ± 1.23

24.16 ± 0.64

5.321

3-Penten-2-ol

928

ND

ND

21.92 ± 0.35

28.93 ± 0.64

5.533

3-Chloro-2-methyl-1-butene

903

31.41 ± 2.70

52.49 ± 2.41

27.35 ± 2.98

55.63 ± 1.91

5.880

Propanoic acid

980

59.92 ± 5.78

18.40 ± 1.51

12.10 ± 1.40

ND

7.550

2-Methylpentanal

933

11.37 ± 0.58

ND

ND

ND

8.286

1-Chloro-2-methyl-2-butene

922

26.97 ± 1.73

43.44 ± 2.41

21.39 ± 2.10

44.50 ± 3.81

8.503

2-Nitroethyl propionate

921

92.87 ± 2.70

66.79 ± 5.13

ND

ND

9.171

Butanedial

977

ND

ND

ND

30.20 ± 1.27

9.501

1,3-Dioxolane-4,5-dione

983

8.48 ± 0.39

ND

ND

ND

11.423

Amylene dichloride

907

ND

ND

39.98 ± 1.23

83.28 ± 2.54

12.032

Furfural

963

52.79 ± 4.82

34.69 ± 1.51

21.39 ± 1.23

77.24 ± 2.54

12.553

4-Cyclopentene-1,3-dione

912

12.52 ± 0.39

16.29 ± 1.51

9.99 ± 0.70

15.58 ± 0.64

13.677

2-Furanmethanol

934

88.25 ± 7.90

71.79 ± 2.71

74.70 ± 3.33

72.79 ± 5.09

14.312

2-Methoxyfuran

929

ND

ND

ND

29.24 ± 0.64

15.605

3-Amino-1,2,4-triazine

945

ND

12.07 ± 1.21

ND

ND

17.810

2(5H)-furanone

969

187.48 ± 11.95

152.34 ± 14.48

143.26 ± 6.14

190.08 ± 5.72

19.177

1,2-Cyclopentanedione

946

129.09 ± 6.94

ND

80.13 ± 4.56

194.53 ± 6.99

20.175

2-Hydroxy-2-cyclopenten-1-one

951

ND

95.02 ± 3.02

ND

ND

22.118

3-Pentanone

948

ND

ND

ND

19.71 ± 0.95

22.323

2-Propanone, oxime

966

ND

ND

ND

12.71 ± 0.32

22.413

Ethyl cyanoacetate

966

ND

204.22 ± 7.84

ND

ND

22.477

Benzaldehyde

946

ND

ND

ND

64.21 ± 0.95

25.392

2H-pyran-2,6(3H)-dione

911

ND

ND

161.67 ± 10.17

332.17 ± 15.89

27.628

1H-pyrrole-2-carboxaldehyde

963

76.49 ± 4.62

90.80 ± 2.11

ND

ND

28.437

3-Methyl-1,2-cyclopentanedione

922

69.17 ± 5.20

66.67 ± 5.13

51.73 ± 0.53

62.30 ± 4.13

29.889

4-Methyl-5H-furan-2-one

938

42.39 ± 4.05

30.47 ± 1.21

35.60 ± 1.40

ND

31.393

2-Butenal

912

ND

ND

ND

272.09 ± 12.71

34.283

o-Hydroxyanisole

905

440.46 ± 11.95

438.91 ± 14.48

618.45 ± 29.98

319.45 ± 1.59

37.580

3-Pyridinol

938

130.64 ± 12.33

ND

ND

ND

44.250

Creosol

947

166.47 ± 9.63

104.37 ± 7.54

1852.01 ± 160.79

ND

44.384

5-(Hydroxymethyl)dihydro-2(3H)-furanone

945

ND

ND

ND

131.28 ± 5.40

44.599

(S)-(+)-2′,3′-Dideoxyribonolactone

949

89.79 ± 2.12

124.28 ± 1.51

ND

ND

45.007

5-Methyl-1H-1,2,4-triazol-3-ylamine

929

ND

93.82 ± 4.83

ND

ND

46.673

1,4:3,6-Dianhydro-α-d-glucopyranose

918

431.21 ± 9.06

708.90 ± 11.46

744.17 ± 27.70

582.01 ± 53.40

48.252

5-Hydroxymethylfurfural

930

1631.41 ± 111.56

1456.11 ± 110.71

1651.94 ± 64.00

1588.68 ± 136.36

49.301

Benzylacetone

918

ND

ND

78.38 ± 4.73

186.90 ± 16.85

55.390

2-Methoxy-4-vinylphenol

933

1106.55 ± 54.15

1095.63 ± 56.41

1217.60 ± 45.06

937.38 ± 58.17

56.662

3-Methoxy-5-methylphenol

922

112.33 ± 3.08

102.26 ± 1.21

101.35 ± 4.21

46.09 ± 3.18

58.269

Hydrocinnamic acid

953

ND

ND

348.59 ± 17.01

465.35 ± 16.21

58.698

Syringol

959

3496.34 ± 201.35

4783.11 ± 59.43

4417.15 ± 46.47

3956.13 ± 372.85

59.103

Eugenol

938

124.08 ± 8.29

155.05 ± 15.69

191.30 ± 0.35

443.42 ± 19.71

60.777

p-Hydroxybenzaldehyde

922

143.93 ± 5.39

231.67 ± 15.99

132.91 ± 9.99

ND

61.182

4-Propylphenol

912

ND

317.95 ± 15.38

ND

ND

62.806

Vanillin

952

1885.55 ± 80.35

1996.98 ± 80.54

2386.11 ± 50.50

1825.17 ± 145.58

63.155

2-Methoxy-1,4-benzenediol

901

312.72 ± 6.36

368.02 ± 22.32

171.66 ± 6.31

147.81 ± 8.26

63.498

Isoeugenol

927

ND

ND

159.04 ± 3016

96.63 ± 6.04

67.185

trans-Isoeugenol

971

1043.55 ± 51.64

1287.18 ± 15.99

1320.36 ± 17.18

750.79 ± 47.68

67.615

2-Methoxy-4-propyl-phenol

935

ND

ND

ND

477.63 ± 40.69

69.959

Apocynin

953

684.01 ± 45.66

775.26 ± 54.90

1078.91 ± 37.17

576.92 ± 59.12

73.335

Vanillyl methyl ketone

900

603.47 ± 39.50

733.03 ± 44.34

ND

432.61 ± 38.78

77.248

1-Hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-propanone

918

ND

ND

27.18 ± 1.23

ND

79.023

Methoxyeugenol

941

1275.34 ± 76.30

1717.04 ± 72.40

1121.51 ± 17.53

1217.10 ± 40.05

83.419

Syringaldehyde

928

4330.06 ± 412.72

5267.87 ± 442.84

4593.55 ± 99.42

5441.20 ± 37.83

84.930

α-Santalol

945

3089.98 ± 203.47

627.72 ± 22.93

ND

ND

85.982

α-Bisabolol

924

3121.77 ± 161.46

2017.80 ± 29.26

ND

ND

88.112

Farnesol

940

5015.80 ± 449.71

ND

ND

ND

88.585

Acetosyringone

928

ND

3088.08 ± 214.78

1850.60 ± 164.83

1305.15 ± 49.90

88.820

Coniferaldehyde

970

2175.53 ± 130.06

2575.26 ± 178.58

1788.71 ± 71.72

2334.39 ± 67.07

91.440

4-Hydroxy-3,5-dimethoxybenzohydrazide

930

ND

ND

336.49 ± 9.64

159.57 ± 9.22

105.131

n-Hexadecanoic acid

937

3508.67 ± 283.82

688.08 ± 10.86

ND

ND

105.378

3,5-Dimethoxy-4-hydroxycinnamaldehyde

910

3123.70 ± 291.91

4394.58 ± 185.52

2943.89 ± 100.30

4493.64 ± 123.33

115.088

Methyl stearate

947

555.11 ± 14.45

68.78 ± 5.73

ND

ND

117.365

Octadecanoic acid

953

3338.51 ± 280.54

244.95 ± 24.43

ND

ND

A: the incense stick produced from Santalum album from Australia; B: the incense stick produced from S. album from Indonesia; C: the incense stick produced from Aquilaria agallocha from Malaysia; D: the incense stick produced from A. agallocha from southwest China. While burning, the four incense sticks emitted aromatic compounds as well as irritant and toxic compounds. A number of compounds occurred in all four samples, including monoterpenes, methoxylated phenolics, two hexose dehydration compounds, as well as other highly volatile compounds. There also were some hypertoxic compounds detected in one or two samples

ND not detected

aRetention time in the gas chromatographer with flame ionization detection

bNational Institute of Standards and Technology library matches

cAmounts are given as mean content ± SD (n = 3) (μg compounds/g total particulate matter)

In vitro mutagenicity

In the prokaryotic genotoxicity assay, the mutagenicity of the total particulate matter from the four incense smoke samples and one cigarette were examined with S. typhimurium TA98, TA100, and TA102. Strain TA98 detects frame shift mutations, and strain TA100 detects base-pair substitution at guanine–cytosine base pairs, while strain TA102 detects certain oxidizing mutagens, cross-linking agents, and hydrazines (Zenzen et al. 2012). The numbers of revertants seen in these three strains are listed in Table 2. Samples D and E tested positive on metabolic activation system (S9)-activated TA98, with D initiating more revertants, while none of the samples tested positive on TA98 without S9 activation. For strain TA100, much weaker positive results were observed with S9 in samples A to D, but a strong positive result with a high revertant number was observed in sample D without S9 treatment. For strain TA102, samples C and D produced a positive response with S9 activation, while all samples, except samples D and E, had a weak positive response without S9 activation. The weaker response in the test with S9 activation in sample D on TA100 may have resulted from the detoxification effect of S9 (Shah et al. 1990). However, some samples showed the reverse response, which can be explained by the fact that some chemical compounds in the total particulate matter could only elicit Salmonella mutagenicity with S9 metabolic activation (Hakura et al. 2005).
Table 2

Mutagenicity of particulate matter samples with Salmonella typhimurium TA98, TA100, and TA102 strains

Sample

Dose (μg/plate)

No. of revertants/plate (with s9)

No. of revertants/plate (without s9)

TA98

TA100

TA102

TA98

TA100

TA102

A

0

36 ± 2

59 ± 9

143 ± 18

25 ± 4

57 ± 4

226 ± 10

 

150

41 ± 4

56 ± 20

131 ± 11

28 ± 6

64 ± 10

237 ± 10

 

250

39 ± 6

86 ± 21

136 ± 33

23 ± 5

77 ± 5

284 ± 10

 

500

43 ± 7

75 ± 19

152 ± 27

31 ± 6

100 ± 5*

333 ± 10*

B

0

36 ± 2

59 ± 9

143 ± 18

25 ± 4

57 ± 4

226 ± 10

 

150

44 ± 2

44 ± 11

109 ± 24

33 ± 3

44 ± 8

240 ± 6

 

250

51 ± 4

57 ± 10

173 ± 33

27 ± 3

46 ± 2

308 ± 16

 

500

52 ± 6*

75 ± 13

181 ± 25

31 ± 4

92 ± 5*

369 ± 13*

C

0

24 ± 2

59 ± 9

143 ± 18

25 ± 4

57 ± 3

200 ± 9

 

150

22 ± 3

77 ± 16

205 ± 36

29 ± 3

59 ± 5

249 ± 3

 

250

31 ± 7

102 ± 12

255 ± 44

26 ± 3

80 ± 3

251 ± 10

 

500

38 ± 8

89 ± 7

295 ± 15*

33 ± 3

175 ± 7*

284 ± 35*

D

0

24 ± 2

59 ± 9

143 ± 18

25 ± 4

57 ± 3

200 ± 9

 

150

34 ± 4

89 ± 20

213 ± 20

26 ± 3

71 ± 7

234 ± 23

 

250

261 ± 18

100 ± 5

297 ± 4

28 ± 5

267 ± 15

217 ± 42

 

500

525 ± 28*

76 ± 13

330 ± 11*

30 ± 3

378 ± 10*

263 ± 32

E

0

24 ± 2

59 ± 9

143 ± 18

25 ± 4

57 ± 3

200 ± 9

 

150

82 ± 16

121 ± 8

177 ± 36

29 ± 2

84 ± 12

201 ± 15

 

250

156 ± 26

139 ± 6

209 ± 37

27 ± 3

87 ± 11

210 ± 32

 

500

140 ± 2*

162 ± 7*

174 ± 31

32 ± 2

98 ± 8

217 ± 35

Amounts are given as mean content ± SD (n = 3). A: the incense stick produced from Santalum album from Australia; B: the incense stick produced from S. album from Indonesia; C: the incense stick produced from Aquilariaa gallocha from Malaysia; D: the incense stick produced by A. agallocha from southwest China; E: the 3R4F reference cigarette from the University of Kentucky. Samples D and E tested positive on metabolic activation system (S9)-activated TA98, with D initiating more revertants. None of the strains tested positive without S9 activation in sample E, but some positive results were observed in samples A to D. The genotoxicity of a given incense sample for some strains was higher than the reference cigarette sample with the same dose

* Difference in these four responses is statistically significant for p < 0.05

In vitro cytotoxicity

Total particulate matter from four incense sticks and one cigarette sample was applied to Chinese hamster ovary cells in concentrations within the range in which concentration-dependent responses are induced (Fig. 2). Our results showed that cytotoxicity of the total particulate matter from the incense smokes was higher than for the cigarette smoke. In addition, smoke from incense sticks with the same component (agarwood) demonstrated different levels of cytotoxicity. In particular, the half maximal inhibitory concentration of sample E was much higher than for all other samples. From these results, we cannot simply conclude that cigarette smoke is less cytotoxic than incense smoke, firstly because of the small sample size analyzed in this study and secondly because of huge variability in the consumption of incense sticks and cigarettes.
Fig. 2

Half maximal inhibitory concentration of Chinese hamster ovary cells exposed to the total particulate matter from five different smoke samples. This figure shows that less smoke from incense than cigarette is needed to reach the same level of cytotoxicity. The reported results are the means of three independent experiments. A The incense stick produced from Santalum album from Australia; B the incense stick produced from S. album from Indonesia; C the incense stick produced from Aquilaria agallocha from Malaysia; D the incense stick produced from A. agallocha from southwest China; E the 3R4F reference cigarette from the University of Kentucky. The smoke from incense sticks with the same component (C and D) demonstrated different levels of cytotoxicity. Sample D demonstrated the highest level of cytotoxicity. The half maximal concentration of sample E was much higher than all other samples

Conclusion

We showed that the particulate number and mass of four different incense smokes were dominated by ultrafine and fine particles, which may cause adverse health effects in indoor environments. Incense smoke particulate matter comprised many aromatic, irritant, and toxic compounds. The total particulate matter from four incense smoke samples was shown to be mutagenic in Ames tests. Genotoxicity to different strains of certain incense samples was higher than for the reference cigarette sample with the same dose. The half maximal inhibitory concentration of this cigarette was much higher than for the four incense samples, indicating that incense smoke was more cytotoxic against Chinese hamster ovary cells. However, we cannot simply conclude that incense smoke is more toxic than cigarette smoke because of differences in consumption styles of these products. Collective assessment of our novel data will affect the evaluation of incense products and facilitate measures to reduce exposure to their smoke.

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • R. Zhou
    • 1
    • 2
  • Q. An
    • 3
  • X. W. Pan
    • 2
  • B. Yang
    • 3
  • J. Hu
    • 2
  • Y. H. Wang
    • 1
  1. 1.College of Light Industry and Food SciencesSouth China University of TechnologyGuangzhouChina
  2. 2.Technology CenterChina Tobacco Guangdong Industrial Co., LtdGuangzhouChina
  3. 3.School of Bioscience and BioengineeringSouth China University of TechnologyGuangzhouChina