The new research initially set out to explore the relationship between air pollution and lung cancer. Plenty of epidemiological studies have reported higher rates of lung cancer in non-smokers who live in areas with greater air pollution. But this correlation never exactly gelled with current theories on how cancer develops. The general idea in modern science is that most tumors begin from a healthy cell that undergoes mutational damage to its DNA which then leads to cancerous growth. This is how tobacco smoke, for example, is thought to lead to lung cancer by damaging the DNA in lung cells.