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4. According to a World Health Organization report, another cause for concern is air pollution. About seven million people worldwide died in 2012 because of it and air pollution-related deaths (heart disease, stroke, lung cancer, chronic obstructive pulmonary disease). Air pollution has a huge impact on global health today and we need to clean up the air we all breathe.


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Contents
1. What is lung cancer?
2. Types of lung cancer
3. Causes of lung cancer
4. Air pollution problem

1. Lung cancer is the main cause of cancer death in the U.S. in both men and women, which is associated mostly with cigarette smoking. In 2014 about 224,000 people in the U.S. were diagnosed with lung cancer. It is the second most common cancer killing almost 160,000 people each year. A prognosis of each patient depends on the type of lung cancer, the person's overall health, and the stage of the cancer at the time of initial diagnosis.

30% of lung cancer sufferers, mostly men and smokers, have squamous cell carcinoma. It is usually easy to detect early, it spreads relatively slowly and often affects only lungs. The most common type of lung cancer (40% of all cases) is adenocarcinoma which can affect lymph nodes and distant organs and may cause no symptoms initially. Usually current or former smokers have it, mostly women. Also it is the most common type of lung cancer among non-smokers. The least common of the non-small cell lung cancers (10%-15% of all cases) are large-cell carcinomas which are usually characterized by large abnormal cells on the outer edges of the lungs. This type of cancer affects nearby lymph nodes and distant sites.Researchers distinguish several main causes of lung cancer: smoking (85%), secondhand tobacco smoking, cancer-causing substances, scarred lung tissue and person's genetics. If a person smokes one pack of cigarettes daily, he is 20 times more likely than a nonsmoker to develop lung cancer. Giving up smoking reduces risk significantly, but still former smokers are more susceptible than nonsmokers. Secondhand tobacco smoke is also dangerous especially for nonsmokers who live or work with smokers.