Many epidemiologic studies have found an association between ambient air pollution and lung cancer. This evidence lead the International Agency for Research on Cancer (IARC) to report air pollution as a category 1 or definite cause of cancer. The IARC reviewed over 1000 studies from five continents and covering many different scientific fields. They concluded that air pollution is linked to increased cancer incidence, with lung cancer being the most prevalent (Pope, 2013).
Air pollution occurs when the air is contaminated by foreign substances. These substances can be liquid or solid and they are small enough that they remain suspended in the air. Some of the substances can be toxic chemicals which can include sulphur dioxide (SO2), oxides of nitrogen (NOx), ozone (O3), volatile organic compounds and suspended particulate matter (PM).
When talking about air pollution we categorize the particles with the term particulate matter (PM). Suspended particulate matter (PM) is divided into three groups based on the diameter of the particle. PM2.5 refers to particles with a diameter less that 2.5 micrometers (µm), PM10 classifies particles with a diameter between 2.5 and 10 µm, and >PM10 defines particles with a diameter greater than 10 µm. The relative risk of developing cancer as a result of exposure to air pollution is generally small, but the attributable risk (relative risk multiplied by the number of exposed people) is high. Because exposure is so high ambient air pollution