Other causes include radon, exposure to secondhand smoke, exposure to substances such as asbestos, chromium, nickel, beryllium, soot, or tar, family history of lung cancer, and air pollution.Genetics can also play a role as a family history of lung cancer can contribute to an increased risk of developing the disease. Furthermore, research has revealed specific chromosome regions associated with increased risks of developing lung cancer. In general, DNA damage appears to be the primary underlying cause of cancer. Though most DNA damages are repairable, leftover unrepaired DNA damages from cigarette smoke are the likely cause of NSCLC. DNA replication past an unrepaired damage can give rise to a mutation because of inaccurate translesion synthesis. In addition, during repair of DNA double-strand breaks, or repair of other DNA damages, incompletely cleared sites of repair can lead to epigenetic gene silencing. DNA repair deficiency in NSCLC
Deficiencies in DNA repair underlie many forms of cancer. If DNA repair is deficient, the frequency of unrepaired DNA damages increases, and these tend to cause inaccurate translesion synthesis leading to mutation. Furthermore, increased damages can elevate incomplete repair, leading to epigenetic alterations.As indicated as in the article Carcinogenesis, mutations in DNA repair genes occasionally occur in cancer, but deficiencies of DNA repair due to epigenetic alterations that reduce or silence DNA repair-gene expression occur much more frequently in cancer.Epigenetic gene silencing of DNA repair genes occurs frequently in NSCLC. At least nine DNA repair genes that normally function in relatively accurate DNA repair pathways are often repressed by promoter hypermethylation in NSCLC.
Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia) and respiratory acidosis. Hypoventilation is not synonymous with respiratory arrest, in which breathing ceases entirely and death occurs within minutes due to hypoxia and leads rapidly into complete anoxia, although both are medical emergencies. Hypoventilation can be considered a precursor to hypoxia and its lethality is attributed to hypoxia with carbon dioxide toxicity. Causes
Hypoventilation may be caused by:

A medical condition such as stroke affecting the brainstem
Voluntary breath-holding or underbreathing, for example, hypoventilation training or the Buteyko method. Medication or drugs, typically when taken in accidental or intentional overdose. Opioids and benzodiazepines in particular are known to cause respiratory depression. Examples of opioids include pharmaceuticals such as oxycodone and hydromorphone and examples of benzodiazepines include lorazepam and alprazolam. Hypocapnia, which stimulates hypoventilation
Obesity; see Obesity hypoventilation syndrome
Chronic mountain sickness, a mechanism to conserve energy. Medications
As a side effect of medicines or recreational drugs, hypoventilation may become potentially life-threatening. Many different central nervous system (CNS) depressant drugs such as ethanol, benzodiazepines, barbiturates, GHB, sedatives, and opioids produce respiratory depression when taken in large or excessive doses, or mixed with other depressants. Strong opiates (namely fentanyl, heroin, and morphine), barbiturates, and certain benzodiazepines (such as alprazolam) are known for depressing respiration. In an overdose, an individual may cease breathing entirely (go into respiratory arrest) which is rapidly fatal without treatment.