Health is affected by all sources of pollution all at once, this is particularly true for the health of sensitive and overburdened people. In a day we do not get to exposed to one pollutant at a time, but rather many at one time. This is referred to as cumulative or additive pollution exposure.
Where you live, work or spend time changes the type and level of pollution you are exposed to in a day and over a lifetime. Areas that have higher exposure are usually near industrial activities, highways, ports, and train tracks.
Some populations may also be at higher risk from air toxics, including environmental justice communities. Health conditions such as asthma and heart disease change how your body reacts to pollution.
The level and source of pollution in an area changes the possibility of someone getting cancer or other diseases. We call this risk.