NS  Vol.12 No.5 , May 2020
Do We Ignore Tobacco’s Positive Ecological Role Too Long?
Abstract: Definitely, tobacco is one of the most troubling plants in this planet because of its harmful effects on humans. Therefore, tobacco plantation declines continuously in the world. For such a plant, do we need to eliminate tobacco entirely from the surface of the earth? Perhaps, humans might have ignored the tobacco’s positive role in environment and ecology, especially in the heavily industrialized environments, for too long. Because the human activity generates more and more nitrogen oxides (NOx) in atmosphere, which not only cause imbalance in the global nitrogen cycle but also lead to haze, smog, acid rain, PM2.5, and eventually impact on environment and human health. Unfortunately the current technologies do not provide an efficient way to remove NOx from atmosphere. However, it is only tobacco can remove NOx from atmosphere. Perhaps, we should blame us, humans who use tobacco unwisely, rather than blame tobacco in nature. Anyways, the ability of tobacco to remove NO2 from atmosphere should not be ignored.


Nitrogen is one of the most abundant elements in the earth, and accounts for 78.1% of the atmosphere. Being an inert gas, nitrogen can be used by organisms only when it is converted into reactive nitrogen [1], although it is essential for all the living species. There are various forms of reactive nitrogen (Nr) in the atmosphere: ammonia (NH3), nitrous oxide (N2O), nitric acid (HNO3), nitrous acid (HONO), nitrogen oxide (NOx) including nitric oxide (NO) and nitrogen dioxide (NO2). Thus, the nitrogen cycle, which undergoes its long-term evolution, maintains the balance of nitrogen.

It is estimated that the global nitrogen fixation generates 413 Tg N every year whereas about a half, 210 Tg N, comes from human activities. Furthermore, there are 100 Tg N into the atmosphere every year from the emissions of the NH3 from land and the NOx from combustion [2]. Without human activity, the biological nitrogen fixation and the production of NOx by lightning are the only sources for new Nr going into the environment [2]. Also, the estimated production of NOx by lighting is about 5 Tg N ranging from 2 to 10 Tg N every year [3 - 8].

Due to this variability, NOx produced by lighting would accounts for 20% - 80% of NOx in the world [5 - 8]. However, the NOx produced by lighting is located in rather remote regions of the troposphere [2]. Still, other estimates indicate that the global NOx is about 40 Tg N in 2000, of which the combustions of fossil fuel and biomass contribute to 87.5% while the emissions of soil NO account for 12.5% [9], i.e. each year soil microorganisms produce 9.7 - 21 Tg N NO [10,11]. In such a case, NOx produced by lighting is not particularly relevant to this estimation.

Nowadays, NO2 usually serves as the indicator for NOx because of human activity. Indeed, NO2 into the atmosphere comes primarily from the burning of fuel, including the emissions from cars, trucks and buses, power plants, and off-road equipment, although NO2 contributes about 10% of NOx and the remaining 90% NOx is NO [11].

To some degree, the harmful effects of NOx to humans are mainly related to NO2. High concentrations of NO2 irritate airways in the human respiratory system. For short exposures, NO2 can aggravate respiratory diseases, especially asthma, and result in the respiratory symptoms, such as coughing, wheezing or difficulty breathing. For long exposures, NO2 may affect immune functions of respiratory system leading to potential of infections as well as asthma. Furthermore, the respiratory system can be damaged by particulate matter and ozone, which are formed during the reactions among NO, NO2 and other chemicals [13]. Some studies estimated that the health damage caused by NOx emission accounted for 39% - 47% of the relevant health damage in China [14].

Following NOx interaction with water, oxygen and other chemicals in the atmosphere, acid rain can be formed, which harms sensitive ecosystems such as lakes and forests. NOx also can form the nitrate particles, which comprise the air hazy and photochemical smog leading to low visibility, ozone and other harmful substances [15]. In the atmosphere active particles are closely related to the oxidizing capacity [16]. Still, coastal waters become nutrient enrichment due to the augmentation of air NOx. The reaction of NOx with volatile organic compounds becomes an important precursor to increase the concentration of atmospheric PM2.5 [17], which also contains nitrated polycyclic aromatic hydrocarbons (NPAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) [18].


The two common methods to reduce NOx emissions are the selective catalytic reduction (SCR) and the selective non-catalytic reduction (SNCR), and SCR is considered the most widely-used method. Generally, SCR can remove around 90% NOx from emissions whereas SNCR can remove about 30% - 70% NOx from emissions. In fact, the NOx removed by SCR and SNCR are the NOx that has yet to enter into the atmosphere, because both SCR and SNCR are implemented in power plans, combustion engines, etc. So there is still a certain amount of NOx passing into the atmosphere even after SCR and SNCR treatment. For example, the total emission of Nr in China has been doubled and the emission of Nr in heavily polluted areas is about 10 times of that in other areas over the last 30 years [12]. This amount of NOx actually raises the health and environmental concerns. Currently, projected regulations for NOx control in the US, EU and Asia define the limit of NOx around 30 to 200 mg/NM3.

It is generally considered that NO could be very slowly removed from the atmosphere through wet and dry deposition [2]. However, we would like to indicate that an important natural source to remove NOx from the atmosphere has been so far ignored. This is tobacco (Nicotiana tabacum L.), which, to the best of our knowledge, is probably the only natural source to remove NOx from the atmosphere although smoking is harmful to human health.

The top part in Figure 1 shows the overall scenario for NOx in the atmosphere, where the left-hand and right-hand sides represent the fresh air with its composition and the polluted air, respectively. The polluted air can form PM2.5 whereas the fresh air comes from removal of NOx from the atmosphere. In the

Figure 1. Tobacco’s double roles in environment and human health. Yellow dashed circle indicates the nitrosation among chemical reactions in tobacco; Green dashed polygon shows tobacco effect in NOx removal from the atmosphere; Red dashed polygon demonstrates tobacco effect in health problems.

middle of Figure 1 shows how tobacco removes NOx from the atmosphere through nitrosition. There are two pathways for nitrosition, 1) nicotine can directly be nitrosated into the nicotine-derived nitrosamine ketone (NNK) [19], or 2) nicotine can be demethylated into nornicotine by P450 enzymes and then nornicotine can furthermore be nitrosated into N-nitrosonornicotine (NNN) [19]. The nitrosation for both nicotine and nornicotine requires a NO 2 from environments [20] (yellow dashed circle in Figure 1). Thus, tobacco helps to remove NOx from the atmosphere as indicated by green dashed polygon in the left part in Figure 1. This nitrosition occurs during tobacco leaves change from green to yellow (lower left-hand part of Figure 1) rather than during smoking (lower right-hand part of Figure 1), so tobacco plantation is helpful to remove NOx from the atomosphere. On the other hand, NNN, NNK and NNAL are carcinogenic to humans [21] as indicated by red dashed polygon in the right part of Figure 1.

The nicotine content is about 19.63 mg/g tobacco [22] because the molar weight of nicotine is 162.23 g/mol, so 1 ton tobacco would have 19.63 kg nicotine (121 mol). If all of the nicotine would be converted to NNN/NNK, then this reaction requires 5.57 kg NO2 (molar weight 46 g/mol), i.e. one-ton tobacco can absorb 5.57 kg NO2 because the reaction consumes NO 2 [20]. Usually, about 5% - 20% nicotine goes to NNN/NNK [19], then one-ton tobacco can absorb 0.28 - 1.10 kg NO2. It is estimated that all smoked cigarettes produce 12,000 - 47,000 tons of nicotine annually yearly [23]. Accordingly, these amounts of nicotine could neutralize 171.17 - 670.40 tons of NO2 in terms of 5% - 20% nicotine goes to NNN/NNK yearly.


Because of tobacco’s harmful effects on humans, its plantation is actually decreasing year by year. For example, the tobacco plantation decreased from 1553 k hectares in 2014 to 1314 k hectares in 2015, and then further decreased to 1273 k hectares in 2016 in China. Accordingly, the tobacco production decreased from 2,994,471 tons in 2014 to 2,832,385 tons in 2015, and then further decreased to 2,725,685 tons in 2016 [24]. In fact, the tobacco production in China was 2,839,947 tons in 2008, and was peaked in 2012 with 3,408,142 tons. Since 2012, the tobacco production in China has been continuously decreasing and reached to 2,392,090 tons in 2017. Consequently, the removal of NOx from the atmosphere also decreased, and the un-removal of NOx should be progressively accumulated in the atmosphere because the lifetime of reactive nitrogen can range from a few weeks to few decades, even to 102 - 103 years in peatlands [15].

Figure 2 displays the accumulation of NOx with reference to the reduction of tobacco production in China and the world since 2008. As can be seen, the tobacco production has begun to decrease in China since 2012 (red bars in lower panel), while the removal of NOx also has begun to drop in the atmosphere since 2012 (red and black lines in upper panel). In the rest of world, the tobacco plantation decreases from 3564 k hectares in 2016 to 3529 k hectares in 2017 whereas the tobacco production increases from 6,399,092 tons in 2016 to 6,501,646 tons in 2017 [25]. So the accumulated NOx in the atmosphere does not change significantly in contrast to China.

Due to the reduction of tobacco plantation, several hundred tons of NO2 per year are accumulating in atmosphere each year. Naturally, this amount is not big, but the accumulated amount of NOx over years would be significant. Indeed, it is not clear how many hectares of tobacco plantation have been terminated due to the harmful effects of tobacco since the industrial revolution. So arguably the accumulated NOx would be a lot. Because of the harmful effect to humans, the tobacco production would be expected to continuously reduce year by year. If the tobacco production in China will reduce 5% each year, then the accumulated NOx will reach 12,805.42 tons in 2030 (Figure 3).

Undeniably, the tobacco creates many healthy problems such as seven million people per year dying globally from tobacco use and exposure [26 - 28]. Also, tobacco industry creates environmental problems, i.e. deforestation [29,30], cigarette butt waste [31 - 33]. However, these problems are created by humans rather than tobacco itself.

At this present, it is unknown how to remove NOx from the atmosphere without tobacco, and then NOx would be accumulated in the atmosphere. A point of view is that humans have no need to remove NOx from the atmosphere because NOx is useful to agriculture and fishery, and the elimination of NOx emission using the current technologies generates too much CO2 further leading to global warming [12] as the elimination of NOx consumes equal molar ammonia, whose production generates CO2 [34,35].

Figure 2. Tobacco production (lower panel) and related NO2 elimination from atmosphere (upper panel) in China and the rest countries from 2008 to 2017.

Figure 3. Predicted decrease in tobacco plantation and related accumulation of NO2 in China from 2017 to 2036.

However, it seems not acceptable to conduct the approach not to remove NOx from atmosphere for the sake of agriculture and fishery because NOx do have well-known unhealthy effects on humans and unwanted pollution effects on environment and ecology.


Apparently, this is a dilemma: humans need to eliminate smoking for health reason through reduction of tobacco plantation, but humans also need to remove NOx from the atmosphere also for health reason. At this point, we feel tobacco innocent when humans consider it as a killer. Ecology is such a delicate system, where nature evolves various items to balance each other. In fact, tobacco plays an important role in the balance of nitrogen cycle by removing NOx, which generated by lighting, natural fire of biomass, and soil, from the atmosphere. Perhaps, we should blame ourselves, humans who use tobacco unwisely, rather than blame tobacco in nature. We are not in favor tobacco smoking, but its unique ability to remove NO2 from atmosphere should not be ignored.


This article does not contain any studies with human or animal participants.


This study was supported by National Natural Science Foundation of China (31560315), and Key Project of Guangxi Scientific Research and Technology Development Plan (AB17190534).

Cite this paper: Yan, S. and Wu, G. (2020) Do We Ignore Tobacco’s Positive Ecological Role Too Long?. Natural Science, 12, 273-280. doi: 10.4236/ns.2020.125023.

[1]   Stevens, C.J. (2019) Nitrogen in the Environment. Science, 363, 578-580.

[2]   Fowler, D., Coyle, M., Skiba, U., Sutton, M.A., Cape, J.N., Reis, S., Sheppard, L.J., Jenkins, A., Grizzetti, B., Galloway, J.N., Vitousek, P., Leach, A., Bouwman, A.F., Butterbach-Bahl, K., Dentener, F., Stevenson, D., Amann, M. and Voss, M. (2013) The Global Nitrogen Cycle in the Twenty-First Century. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 368, 20130164.

[3]   Levy, H., Moxim, W.J. and Kasibhatla, P.S. (1996) A Global Three-Dimensional Time-Dependent Lightning Source of Tropospheric NOx. Journal of Geophysical Research: Atmospheres, 101, 22911-22922.

[4]   Tie, X.X., Zhang, R.Y., Brasseur, G. and Lei, W.F. (2002) Global NOx Production by Lightning. Journal of Atmospheric Chemistry, 43, 61-74.

[5]   David, A. (2005) Bridging Ocean Color Observations of the 1980s and 2000s in Search of Long-Term Trends. Journal of Geophysical Research, 110, 1-12.

[6]   Watson, W.G., Margarita, E.C., Paul, G., O'Reilly, J.E. and Nancy, W.C. (2003) Ocean Primary Production and Climate: Global Decadal Changes. Geophysical Research Letters, 30, 1809.

[7]   Watson, W.G. and Margarita, E.C. (2002) Decadal Changes in Global Ocean Chlorophyll. Geophysical Research Letters, 29, 20-24.

[8]   Dionysios, E.R. (2005) Extending the Sea WiFS Chlorophyll Data Set Back 50 Years in the Northeast Atlantic. Geophysical Research Letters, 32, L06603.

[9]   van Vuuren, D.P., Bouwman, L.F., Smith, S.J. and Dentener, F. (2011) Global Projections for Anthropogenic Reactive Nitrogen Emissions to the Atmosphere: An Assessment of Scenarios in the Scientific Literature. Current Opinion in Environmental Sustainability, 3, 359-369.

[10]   Potter, C.S., Matson, P.A., Vitousek, P.M. and Davidson, E. (1996) Process Modeling of Controls on Nitrogen Trace Gas Emissions from Soils Worldwide. Journal of Geophysical Research, 101, 1361-1377.

[11]   Davidson, E.A. and Kingerlee, W. (1997) A Global Inventory of Nitric Oxide Emissions from Soils. Nutrient Cycling in Agroecosystems, 48, 37-50.

[12]   Ozaki, S. (2017) NOx Is Best Compound to Reduce CO2. European Journal of Experimental Biology, 7, 12.

[13]   US EPA (US Environmental Protection Agency) (2019)

[14]   Gu, B., Ge, Y., Ren, Y., Xu, B., Luo, W., Jiang, H., Gu, B. and Chang, J. (2012) Atmospheric Reactive Nitrogen in China: Sources, Recent Trends, and Damage Costs. Environmental Science & Technology, 46, 9420-9427.

[15]   Wayne, R.P. (1991) Chemistry of Atmospheres. 2nd Edition, Clarendon Press, Oxford, UK.

[16]   Isaksen, I.S.A., Granier, C., Myhre, G., Berntsen, T.K., Dalsøren, S.B., Gauss, M., Klimont, Z., Benestad, R., Bousquet, P., Collins, W., Cox, T., Eyring, V., Fowler, D., Fuzzi, S., Jöckel, P., Laj, P., Lohmann, U., Maione, M., Monks, P., Prevot, A.S.H., Raes, F., Richter, A., Rognerud, B., Schulz, M., Shindell, D., Stevenson, D.S., Storelvmo, T. Wang, W.C., van Weele, M., Wild, M. and Wuebbles, D. (2009) Atmospheric Composition Change: Climate-Chemistry Interactions. Atmospheric Environment, 43, 5138-5192.

[17]   Yan, S. and Wu, G. (2016) Network Analysis of Fine Particulate Matter (PM2.5) Emissions in China. Scientific Reports, 6, 33227.

[18]   Li, J., Yang, L., Gao, Y., Jiang, P., Li, Y., Zhao, T., Zhang, J. and Wang, W. (2019) Seasonal Variations of NPAHs and OPAHs in PM2.5 at Heavily Polluted Urban and Suburban Sites in North China: Concentrations, Molecular Compositions, Cancer Risk Assessments and Sources. Ecotoxicology and Environmental Safety, 178, 58-65.

[19]   Siminszky, B., Gavilano, L., Bowen, S.W. and Dewey, R.E. (2005) Conversion of Nicotine to Nornicotine in Nicotiana tabacum Is Mediated by CYP82E4, a Cytochrome P450 Monooxygenase. Proceedings of the National Academy of Sciences of the United States of America, 102, 14919-14924.

[20]   Lusso, M., Gunduz, I., Kondylis, A., Jaccard, G., Ruffieux, L., Gadani, F., Lion, K., Adams, A., Morris, W., Danielson, T., Warek, U. and Strickland, J. (2017) Novel Approach for Selective Reduction of NNN in Cigarette Tobacco Filler and Mainstream Smoke. Regulatory Toxicology and Pharmacology, 89, 101-111.

[21]   IARC (2007) Smokeless Tobacco and Some Tobacco-Specific N-Nitrosamines. In: International Agency for Research on Cancer (Ed.), IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. World Health Organization, Lyon, France.

[22]   O’Connor, R.J., Schneller, L.M., Caruso, R.V., Stephens, W.E., Li, Q., Yuan, J. and Fong, G.T. (2015) Toxic Metal and Nicotine Content of Cigarettes Sold in China, 2009 and 2012. Tobacco Control, 24, iv55-iv59.

[23]   Novotny, T.E., Bialous, S.A., Burt, L., Curtis, C., da Costa, V.L., Iqtidar, S.U., Liu, Y., Pujari, S. and Tursan d'Espaignet E. (2015) The Environmental and Health Impacts of Tobacco Agriculture, Cigarette Manufacture and Consumption. Bulletin of the World Health Organization, 93, 877-880.

[24]   (2019) Statistics from Ministry of Agriculture and Rural Affairs of the People’s Republic of China.

[25]   Food and Agriculture Organization of the United Nations. (2019)

[26]   Ng, M., Freeman, M.K., Fleming, T.D., Robinson, M., Dwyer-Lindgren, L., Thomson, B., Wollum, A., Sanman, E., Wulf, S., Lopez, A.D., Murray, C.J. and Gakidou, E. (2014) Smoking Prevalence and Cigarette Consumption in 187 Countries, 1980-2012. JAMA, 311, 183-192.

[27]   GBD 2015 Tobacco Collaborators (2017) Smoking Prevalence and Attributable Disease Burden in 195 Countries and Territories, 1990-2015: A Systematic Analysis from the Global Burden of Disease Study 2015. Lancet, 389, 1885-1906.

[28]   World Health Organization (2017) WHO Report on the Global Tobacco Epidemic, 2017: Monitoring Tobacco Use and Prevention Policies. WHO, Geneva.

[29]   Otanez, M.G., Mamudu, H.M. and Glantz, S.A. (2009) Tobacco Companies’ Use of Developing Countrie’ Economic Reliance on Tobacco to Lobby against Global Tobacco Control: the Case of Malawi. The American Journal of Public Health, 99, 1759-1771.

[30]   Otanez, M. and Glantz, S.A. (2011) Social Responsibility in Tobacco Production? Tobacco Companies’ Use of Green Supply Chains to Obscure the Real Costs of Tobacco Farming. Tobacco Control, 20, 403-411.

[31]   Novotny, T.E., Lum, K., Smith, E., Wang, V. and Barnes, R. (2009) Cigarettes Butts and the Case for an Environmental Policy on Hazardous Cigarette Waste. International Journal of Environmental Research and Public Health, 6, 1691-1705.

[32]   Healton, C.G., Cummings, K.M., O'Connor, R.J. and Novotny, T.E. (2011) Butt Really? The Environmental Impact of Cigarettes. Tobacco Control, 20, i1.

[33]   Curtis, C., Collins, S., Cunningham, S., Stigler, P. and Novotny, T.E. (2014) Extended Producer Responsibility and Product Stewardship for Tobacco Product Waste. International Journal of Waste Resources, 4, 157.

[34]   Chambers, J.Q., Higuchi. N., Tribuzy, E.S. and Trumbore, S.E. (2001) Carbon Sink for a Century. Nature, 410, 429.

[35]   Fourqurean, J.W., Duarte, C.M., Kennedy, H., Marba, N. and Holmer, M. (2012) Seagrass Ecosystems as a Globally Significant Carbon Stock. Nature Geoscience, 5, 505-509.