The increased combustion of
fossil fuels is one of the main reasons for the hazardous changes in the atmospheric composition. The sources of air pollution in urban areas include diesel motor vehicles, residential wood burning, and certain industrial processes. The types of air pollution include
gases(eg,
carbon monoxide,
sulfur dioxide,
nitrogen oxides,
ozone)and suspended
particulate matter(PM)such as PM2.5 and PM10 in
diesel exhaust particles. PM2.5 refers to particles less than 2.5 micrometers in diameter. Long-term exposure to PM2.5 can increase the
cardiovascular disease risk and
lung cancer mortality. Although the role of PM2.5 in the etiology of
lung cancer is not very clear, some researchers have shown evidence of increases in
lung cancer mortality associated with exposure to PM2.5.
Asbestos is also an important cause of
cancer of the respiratory tract, particularly
lung cancer and
mesothelioma. The oncogenic hazards of
asbestos fiber have been noted in cases of lowdose environmental exposure, as well in cases of high-dose occupational exposure. The use of
asbestos has been strictly prohibited in Japan since 2006. However, large-scale natural disasters such as earthquakes, tsunamis, and typhoons can destroy many buildings and houses that were constructed before the ban on
asbestos was initiated, thus resulting in the exposure of human beings to
asbestos fibers. In the Cappadocian villages of Tuzkoy, Karain, and Sarihidir in Turkey, 50% of all deaths among villagers are caused by
mesothelioma. This condition has been attributed to exposure to
erionite, which is a type of fibrous
zeolite mineral commonly found in this area of Turkey. However, pedigree studies of these villages showed that
mesothelioma was prevalent in certain families but not in others, and that
erionite exposure typically causes
mesothelioma in those with a
genetic predisposition to this disease. Recently, the germline BAP1 mutation was demonstrated in 2 different familial clusters of
mesothelioma in the US.