Question: why is pollution a problem in the us

title: Air pollution in the United States
text: A study conducted in 2000 used geographic census data and outdoor nitrogen dioxide ( NO2 ) concentration data to examine the disparities of NO2 air pollution across the United States . The study found that there is disproportional disparities in terms of both race and socioeconomic groups . The people of color were exposed to 4.6 ppb more than average NO2 concentrations than white people . Those who live in below poverty level are exposed to 1.2 ppb more . Lower - income Caucasians are exposed to 3.4 ppb higher NO2 concentrations than the higher - income Caucasians . The study also reports disproportional disparities of NO2 concentration exposure by education level ; those who without high school education are more likely to be exposed to higher concentrations . Association between NO2 exposure and cancer development has been found in many studies .