Introduction
Lung cancer has remained the leading cause of cancer deaths in both men and women in United States. According to International Agency for Research on Cancer (IARC), approximately 1.35 million new cases of lung cancer are diagnosed across the world each year. There are a wide number of risk factors associated with lung cancer. These are smoking, exposure to asbestos, silica exposure, and diesel exhaust. The most common cause is the exposure to tobacco smoke through either active or passive smoking. Males are at a higher risk of lung cancer than females, a ratio of 7.8 to 5.8 respectively. There are five lung cancer types. These are small cell, squamous cell, adenocarcinoma, large-cell and carcinoid types (2012).
Epidemiology of lung cancer
The main risk factors for lung cancer
Direct or indirect smoking contributes to almost 90% of lung cancer cases reported today. Cigarettes and tobacco smoke has over 70 cancer-causing chemicals referred to carcinogens. Moreover, cigarette smoke damages and kills hair-like projections called cilia found on the airway. The function of cilia is to sweep away toxins, viruses, carcinogens, and bacteria contained in the inhaled air. Destruction of cilia by cigarette smoke allows accumulation of all these materials in the lungs causing infections and eventually lung cancer. Currently, smoking prevalence has shifted to developing countries a suggestion that there could be a higher morbidity and mortality rates of lung cancer in these areas in future. Reduction in smoking prevalence among cigarette smokers is the only solution to the reductions of cancer cases (Lubin & Caporaso 2006).
Another risk factor causing cancer is the exposure to asbestos. People working in construction and shipyards have a high risk of exposure to asbestos. Asbestos contributed to 1,900 cases of lung cancer in Britain in 2005. Exposure of asbestos increases risks of lung cancer death by 77 per cent and causes almost 8 per cent of lung cancer deaths in the United Kingdom (UK) (Frost, Darnton, & Harding 2011). In addition, people with high exposure to asbestos and at the same time smoke cigarette have greater risks of acquiring lung cancer compared to non-smokers (IARC 2013).
Exposure to silica dust also causes lung cancer. As shown on AIRC statistics, around 790 lung cancer cases reported in U.S. in 2005 were caused by silica exposure. Silica is commercially bused in manufacture of glass; hence, people working in glass manufacturing industries are at higher risks of lung cancer diagnosis. Silica induces lung cancer by indirectly by causing silicosis. People diagnosed with silicosis have double the risk of lung cancer. Silica exposure in absence of silicosis does not lead to lung cancer risks, but there is no enough evidence to conclude this (Pelucchi et al 2006, pp. 40-41).
According to IARC, exposure to diesel exhaust causes lung cancer. The high numbers of workers exposed to diesel exhaust in manufacturing industries are at higher risks of lung cancer. In addition, miners with a higher exposure to diesel exhaust are more likely to acquire lung cancer compared to people working in open-air. Moreover, professional drivers with approximately 10 years of experience have more than 20% increased lung cancer risks because of diesel exhaust exposure while in their career (International Agency for Research on Cancer, 2012).
Susceptibility
People differ to their susceptibility to diseases depending on the concept of heritable traits and environmental exposure. The genetic differences found among individual in terms of susceptibility to lung cancer on people smoking cigarette has been greatly investigated. A number of genetic polymorphisms are the main contributors to high cancer susceptibility among cigarette smokers. Even with many risk factors that cause cancer, more than 80 per cent of lung cancers are caused by tobacco. According to AIRC research, men are more susceptible to lung cancer compared to women because men are more exposed to cancer risk factors (2012).
Incidences of lung cancer and mortality rates increase between the ages of 45 and 54 years and progresses until the age of 75 years. As seen from figure 1, the median age at diagnosis is 70.07 and the median age at death is 71.07.
Figure 1: Death and age-specific mortality rates for lung cancer victims in UK, 2006.
Figure 2: Lung Cancer incidence rates by ethnicity (National Cancer Institute, 2012)
In terms of ethnicity, black men have a higher probability of developing lung cancer than white men, 76.6 per cent (See figure 2). On the other hand, the geographical location of a place determines the susceptibility of lung cancer. Areas with high prevalence of cigarette smoking record higher lung cancer mortality rates. In U.S. rates are highest in Kentucky and lowest in Utah. More lung cancer cases are also reported in California than in Alaska. In addition, most lung cancer cases are found in North America, Western Europe, and Australia (National Cancer Institute 2012).
Conclusion
Lung cancer has affected a number of people and caused many deaths. As seen from the above discussion, there are many risk factors associated with lung cancer, but the most common one is smoking. People who smoke directly or indirectly should go for a cancer test because when detected earlier, it becomes easier to treat. On the other hand, experts have developed new technologies, like genetic profiling that are helpful in detecting new genetic variants involved in lung cancer risk. It has also been found out that lung cancer susceptibility depends on the level of exposure to risk factors, age, gender, and ethnicity.
References list
FROST, G., DARNTON, A., & HARDONG, AH. (2011). The effect of smoking on the risk of Lung Cancer Mortality for Asbestos workers in Great Britain (1971-2005). Ann Occup Hyg, 55(3), 39-47.
INTERNATIONAL AGENCY FOR RESEARCH ON CANCER (IARC). (2012). IARC Monographs on the Evaluation of Carcinogenic Risk to Humans, Diesel and gasoline engine exhausts and some nitroarenes. France: IARC
LUBIN, J. H. & CAPORASO, N. E. (2006). Cigarette Smoking and Lung Cancer: Modeling Total Exposure and Intensity. Cancer Epidem Biomar, 15 (3), 17-23.
NATIONAL CANCER INSTITUTE. (2012). NCI international portfolio addressing the global challenge of cancer. Bethesda, Md.: U.S Dept. of Health and Human Services, National Institutes of Health, National Cancer Institute.
PELUCCHI, C., PIRA, E., PIOLATTO, G. et al. (2006). Occupational silica exposure and lung cancer risks: A review of epidemiological studies 1996-2005. Ann Oncol 17(70), 39-50.
