The rapid urbanization and industrialization has brought about remarkable changes in ourworld but on the other hand this has drastically affected human health. The incidence ofnumerousdiseases, including cancers have grown manifold in the last few decades itself, andthe occurrences of aero digestive cancers have also shown a surge. This can be linked directly tothe deteriorating air quality. The petroleum refining industry and the combustion ofpetrochemical fuels is the largest contributor to this increasing urban ambient air pollution and is now knownto be carcinogenic. Chronic exposures to the various carcinogenic pollutants, from outdoorand indoor air pollution have diverse effects on the delicate epithelium of aero digestive tractand havebeenstronglylinkedtoaero digestivetractcancers.Withtherevelationofthesefacts,more emphasis must be paid to curbing the problem of air pollution while also promoting the useof renewable energy and clean energysources.
Keywords:Aero digestive Cancers; Carcinogens; Petroleum; Pollution
Humans, like every other species, are an integral part of the ecosystem. It is awell- known fact that we have been responsible for drastic changes in the climate andenvironment, and that these changes have had far reaching effects on our health[1,2].Human health has paida heavy price for growing industrialization and urbanization. It was in the 1950s that sawa massive increase in the production and consumption of many petroleum based fuel productslike gasoline and diesel fuel .This was also the same time when an ongoing epidemic of lungcancer in Western Europe and United States was observed which led to the researchers to draw adirect link between outdoor air pollution and cancers of the aero digestive tracts. Althoughultimately, cigarette smoking was identified as a culprit in this surge the incidence of lung cancers, a lotof research was directed to the possible carcinogenic role of petroleum products and outdoorair pollution on humans[4,5]. This concern, that air pollution can cause lung cancer has persisted till date and isonly fortified by the growing levels of pollution from industrial sources and motorvehicles, particulate matter in the urban ambient air and also the growing knowledge indicating thevariouscarcinogenic and mutagenic effects of these pollutants. It was much later in 2013, that the World Health Organization (WHO), for the first time announced that outdoor air pollution is carcinogenic to humans. Aero digestive cancers include the cancers of lip, tongue, major salivary glands, gums and adjacent oral cavity tissues, floorofthemouth,tonsils,oropharynx,nasopharynx,hypopharynxandotheroralregions,nasalcavity,accessorysinuses,middleear,andlarynxand they constitute about 4% of all reported malignancies .
Although, aero-digestive tract cancer is a multidimensional problem, a number of risk factors have been attributed to the global increase in aero digestive cancers. These include exposure to tobacco and alcohol, inadequate nutrition, human papilloma virus, chronic trauma to oral mucosa, poor oral hygiene and even chronic exposure to carcinogenic chemicals in the ambient urban air . In fact, outdoor air pollution and Particulate Matter (PM), was officially classified as IARC Group 1 carcinogens by the International Agency for Research on Cancer (IARC) . With this revelation, more policies should be directed towards reducing air pollution by petroleum derivatives while also paying more attention to occupational hazards.
Petroleum and Air Pollution
- The Global Urban Ambient Air Pollution Database released by WHO revealed that air pollution levels in cities across the globe rose by 8 per cent, even with small improvements in certain developed regions. The troubling fact being that over 80 per cent of city dwellers are exposed to air quality that fails to meet the minimum safety levels with the high-risk groups being low- and middle-income cities across the globe. It also exposed that major Asian cities such as Delhi, Beijing, Mumbai, Dhaka and Kolkata are heavily polluted and that this urban air pollution which continues to rise at an alarming rate is wreaking havoc on human health .
- The rapid urbanization and industrialization is definitely to blame for this deterioration of urban ambient air quality. The process of converting petroleum into petrochemical products is known as petroleum refining and this industry is a major contributor to environmental pollution worldwide . These industries release a wide variety of chemicals like benzene, ethyl benzene, xylenes, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, carbon tetrachloride, chloroform which are toxic and carcinogenic to humans [12,13].
- The second biggest source of environmental pollution from petroleum is from products released from vehicular exhausts. These exhaust gases are well known to contain a variety of carcinogenic and mutagenic pollutants like Polycyclic Aromatic Hydrocarbons (PAHs), alkylated PAHs, alkylbenzenes and alkanoic acids Benzene, butadiene, toluene, ethylbenzene, Xylene, trimethyl pentane, Methyl Tert-Butyl Ether (MTBE) and many other chemicals are found in gasoline . These chemicals have shown evidence of increased risk of leukemia and cancers of kidney, liver, brain, pancreas, aero digestive tract and even prostate cancers . Kurt Straif, head of International Agency for Research on Cancer (IARC)’s department that ranks carcinogens expressed in 2013 that, depending on the level of exposure to pollution in different parts of the world, the risk of cancers was found to be similar to that of breathing in second-hand tobacco smoke .
Indoor Air Pollution
- Along with the rise in outdoor pollution there is component of indoor air pollution which tends to be overlooked by the developed countries but is a major health hazard in the developing cities and comparatively poorer towns. With the increase in fuel requirements, there has been a significant increase in the use of indoor fuels such as coal and wood. Even today, it is estimated that half of the global population and almost 90%of rural population in developing countries rely on coal and biomass in the form of wood, dung and crop residues to meet their domestic energy requirements. Other petroleum based fuels like kerosene are also sometimes utilized to meet household energy requirements.
- What actually worsens the situation is that these fuels are typically burnt in simple stoves and often result in incomplete combustion. This leads to people in developing countries being exposed to very high levels of pollution for an average of 3-7 hours daily over many years and this tends to increase to almost 24-hour periods in the cold and mountainous regions of the world [17,18]. Tobacco and cigarette smoke also attributes to indoor air pollution and is extremely detrimental not only to the smoker’s health, but also to all those around him. Today although, the connection of tobacco smoke to aero digestive cancers is well established, there is also definitive evidence to support that indoor air pollution increases the risk of chronic obstructive pulmonary disease and of acute respiratory infections in childhood, which happen to be some of the most important cause of death among children under 5 years of age in developing countries [17,19,20].
- The inhaled pollutants also have an association with low birth weight, increased infant and perinatal mortality, pulmonary tuberculosis, cataract etc. They are also closely linked to increased incidence of various aero digestive cancers like nasopharyngeal and laryngeal cancer especially hypo pharyngeal cancer and lung cancer .
- Tobacco smoke is known to be packed with a number of carcinogens like benzo[a] pyrene, formaldehyde, acetaldehyde, croton aldehyde and Tobacco-specific nitrosamines .Thus, it is estimated that exposure to indoor air pollutants may be responsible for nearly 2 million excess deaths in developing countries
Aero digestive Cancers
- The aero digestive tract consists of the combined organs and tissues of the respiratory tract and the upper part of the digestive tract (including the lips, mouth, tongue, nose, throat, vocal cords, and part of the esophagus and windpipe) . Oral cancer accounts for the highest incidence, among the various aero digestive cancers although the incidence is high worldwide; Asia has a particularly high incidence of oral cancers which has a direct link to the widespread use of smoked and smokeless tobacco .
- Petroleum contains a number of chemicals detrimental to human health like benzene, butadiene, toluene, ethylbenzene, Xylene, trimethyl pentane, Methyl Tert Butyl Ether (MTBE) etc. of which, benzene is a known human carcinogen . Chronic exposure of the delicate Squamous epithelium of the aero digestive to various carcinogenic chemicals, whether derived from ambient air pollution, occupational expose to petroleum or tobacco smoke has farfetched effects . The actual mechanism of action of these carcinogens is varied and difficult to decipher. However, the possible mechanism is that, on inhalation the pollutants get deposited on the mucosal lining of the aero digestive tract. The delicate balance of the mucous membranes and special sensory organs of these passages and the mucociliary activity makes the mucosa susceptible to local and recruited immune responses, rapid uptake of chemicals increasing the carcinogenic potential of pollutants to these delicate barrier epitheliums .
- On longstanding and chronic exposure, these carcinogenic chemicals may evoke a cellular response resulting in pulmonary oxidative stress. This can ultimately result in a pro-inflammatory response from the tissue and concluding into genotoxicity. A number of studies have proven this relationship between pollution and cancer. In a multi-center, urban study that consisted of 8111 subjects showed, that fine particulates including sulfates that cause air pollution, were positively associated with lung cancer mortality . Another study that consisted of a 15-year follow-up consisting of 6,338 non-smoking adults in California showed that increased risk of developing lung cancer was associated with air pollution, especially with the levels of Sulphur dioxide, ozone, and Particulate Matter 10 (PM10) . A few animal studies conducted on laboratory mice have also shown conclusive evidence to support the opinion that exposure to polluted air leads to DNA mutations [28,29]. DNA and protein damage has been linked to higher risks of developing aero digestive cancers . A study carried out recently presented that environmental and occupational exposures to carcinogenic PAHs and benzopyrene was associated with higher plasma levels of p53 and p21 proteins, which were different from the controls .
According to the data presented by the International Agency for Research on Cancer (IARC) in 2010, air pollution contributed significantly to over 223,000 deaths from lung cancer worldwide and is also known to increase the risk of bladder cancer. Although the exact mechanism in which the exposure of the aero digestive tract causes malignant transformation is not understood, the presence of a definitive link between the two is well established. It is established that urban ambient air contains a number of carcinogenic chemicals, more research should be directed towards eliminating these carcinogens from the environment and to come up with alternative industrial processes and promoting the use of clean energy. Finally, stakeholders and policy makers must establish ameliorative policies to regulate release of polluted air into the atmosphere and implement preventive strategies.
- Pope III CA (2000) Review epidemiological basis for particulate air pollution health standards. Aerosol Science & Technology 32: 4-14.
- Khanna SS, Gharpure AS (2012) Correlation of increased sinusitis and urban air pollution. Ind J Sci Res Tech 1: 14-17.
- Chen NY (1999) ChemEng Gas (Shi you Yu TianranqiHuagong) 28:167-173.
- Doll R, Hill AB (1952) A study of the a etiology of carcinoma of the lung. Br Med J 13: 1271-1286.
- White C (1990) Research on smoking and lung cancer: a landmark in the history of chronic disease epidemiology. Yale J Bio Med 63: 29-46.
- Cohen AJ (2000) Outdoor air pollution and lung cancer. Environmental Health Perspectives 108: 743-750.
- Muir C, Weil L (1995) Upper aero digestive tract cancers. Cancer 75: 147-153.
- Gupta B, Johnson NW (2014) Emerging and established global life-style risk factors for cancer of the upper aero-digestive tract. Asian Pac J Cancer Prev15: 5983-5991.
- International Agency for Research on Cancer (2013) IARC: Outdoor air pollution a leading environmental cause of cancer deaths. International Agency for Research on Cancer: 1-4.
- World Health Organization (2016) World Health Statistics 2016: Monitoring Health for the SDGs Sustainable Development Goals. World Health Organization.
- Sabirova ZF (1998) The effect of atmospheric pollution in petroleum refining, petrochemical and chemical regions on population mortality. Gig Sanit 5: 15-17.
- International Agency for Research on Cancer (1982) Some industrial chemicals and dyestuffs. IARC Monographs on the evaluation of carcinogenic risks to humans 29: 1-398.
- Porada E, Kousha TE (2016) Factorization methods applied to characterize the sources of volatile organic compounds in Montreal Quebec. Int J Occup Med Environ Health 29: 15-39.
- Liang F, Lu M, Keener TC, Liu Z, Khang SJ (2005) The organic composition of diesel particulate matter diesel fuel and engine oil of a non-road diesel generator. J Environ Monit 7: 983-988.
- Mehlman MA (1990) Dangerous properties of petroleum‐refining products: Carcinogenicity of motor fuels Gasoline. TeratogCarcinog Mutagen 10: 399-408.
- Albalak R (1997) Cultural practices and exposure to particulate pollution from indoor biomass cooking: Effects on respiratory health and nutritional status among the Aymara Indians of the Bolivian highlands (Doctoral dissertation).
- Norboo T, Yahya M, Bruce NG, Heady JA, Ball KP (1991) Domestic pollution and respiratory illness in a Himalayan village. Int J Epidemiol 20: 749-757.
- Engle P, Hurtado E, Ruel M (1997) Smoke exposure of women and young children in highland Guatemala prediction and recall accuracy. Human organization 56: 408- 417.
- Collings DA, Sithole SD, Martin KS (1990) Indoor wood smoke pollution causing lower respiratory disease in children. Tropical Doctor 20: 151-155.
- Behera D, Dash S, Malik SK (1988) Blood carboxyl hemoglobin levels following acute exposure to smoke of biomass fuel. Indian J Med Res 88: 522-524.
- Sapkota A, Gajalakshmi V, Jetly DH, Roy chowdhury S, Dikshit RP, et al. (2008) Indoor air pollution from solid fuels and risk of hypo pharyngeal/laryngeal and lung cancers a multi centric case-control study from India. International J Epidemiol 37: 321-328.
- Hecht SS, Hoffmann D (1988) Tobacco-specific nitrosamines, an important group of carcinogens in tobacco and tobacco smoke. Carcinogenesis 9: 875-884.
- NCI Dictionary of Cancer Terms U.S. Department of Health and Human Services National Institutes of Health, National Cancer Institute, USA.
- D’ cruz A, Lin T, Anand AK, Atmakusuma D, Calaguas MJ, et al. (2013). Consensus recommendations for management of head and neck cancer in Asian countries a review of international guidelines. Oral oncology 49: 872-877.
- Holt GR (1996) Effects of air pollution on the upper aero digestive tract. Otolaryngology-Head Neck Surg 114: 201-204.
- Dockery DW, Pope CA, Xu X, Spengler JD, Ware JH, et al. (1993) An association between air pollution and mortality in six US cities. New England journal of medicine 329: 1753-1759.
- Beeson WL, Abbey DE, Knutsen SF (1998) Long-term concentrations of ambient air pollutants and incident lung cancer in California adults results from the AHSMOG study Adventist Health Study on Smog. Environmental health perspectives 106: 813-822.
- Somers CM, Mc Carry BE, Malek F, Quinn JS (2004) Reduction of particulate air pollution lowers the risk of heritable mutations in mice. Science 304: 1008-1010.
- Somers CM, Yauk CL, White PA, Parfett CL, Quinn JS (2002) Air pollution induces heritable DNA mutations. Proceedings of the National Academy of Sciences 99: 15904-15907.
- VineisP,Husgafvel-Pursiainen K (2005) Air pollution and cancer: biomarker studies in human populations. Carcinogenesis 26: 1846-1855.
- Rossner P, Binkova B, Milcova A, Solansky I, Zidzik J, et al. (2007) Air pollution by carcinogenic PAHs and plasma levels of p53 and p21 WAF1 proteins. Mutation Research 620: 34-40.
Citation: Khanna SS, Dhaimade P (2017) Carcinogenicity of Petroleum to the Aero Digestive Tract. Arch Petro Environ Biotechnol 2017: APEB-111.