Anything introduced into the environment that harms people or living things is a form of pollution.  The most pervasive form of pollution in the region is air pollution which affects the health of everyone in Los Angeles County.  The primary source of the air pollution comes from all the vehicles on the road today that use gasoline and diesel combustion engines.  Pollutants exit the tailpipe of cars and become trapped in the atmosphere. The 2015 American Lung Association’s report places the Los Angeles Basin and California’s Central Valley as areas with the nation’s highest levels of ozone and fine particle pollution.1  These air pollutants are leading causes for asthma attacks and other chronic illnesses.  Air pollution is made worse by a lack of trees and green space because plants naturally filter the air and keep temperatures cooler.  The built-up concrete environment of the urban landscape traps heat and makes air quality worse because high temperatures increase the severity of air pollution.  In addition to air pollution the water that flows overland is polluted by contaminated rainwater runoff whose sources range from oil and metals from roadways to disease causing bacteria.  Today the Los Angeles River has been designated as impaired due to multiple sources of contamination.2

The map shown here combines sources of pollution into an intensity map, which shows where pollution is affecting communities most severely.  “Pollution Burden scores for each census tract are derived from the average percentiles of the six Exposure Indicators (ozone and PM2.5 concentrations, diesel PM emissions, pesticide use, toxic releases from facilities, and traffic density) and the five Environmental Effects indicators (cleanup sites, impaired water bodies, groundwater threats, hazardous waste facilities and generators, and solid waste sites and facilities)” (California Office of Environmental Health Hazard Assessment).

1 American Lung Association, State of the Air, http://www.stateoftheair.org/2015/states/california/los-angeles.html
2 UCLA Institute of the Environment and Sustainability, Environmental Report Card Los Angeles County, http://www.environment.ucla.edu/perch/resources/report-card-2015-water.pdf (2015)