According to the National Academy of Sciences, oil equivalent of an Exxon Valdez oil spill is released into the environment from cars every eight months. This equals 10.9 million gallons of petroleum entering sensitive ecosystems and this number only includes discharges in the United States! So, that rainbow sheen you see running from underneath your car or in the parking lot of your local shopping center is responsible for polluting local streams and rivers.
Oil entering the environment as runoff from streets, driveways and parking is extremely detrimental to local watersheds. It comes in the form of car exhaust, tire wear, metals, oil leaking from engines, and improper disposal of oils and lubricants. The amount of pollutants has grown due to the rising demand for cars, and the increased stormwater produced in urban and suburban places. This is bad news for vulnerable ecosystems, such as rivers, lakes and coastal habitats, where much water pollution often ends up. In addition to cars, oil pollution is common from boating activity. This petroleum hydrocarbon pollution from motor vehicles is expected to continue growing in the upcoming years with global urbanization.
Impervious surfaces are partly to blame. When stormwater is unable to infiltrate, it collects pollutants on the surface of streets and parking areas, which are carried into storm drain systems. Storm drains release this polluted runoff into local waters and wreak havoc on the plants and animals. Oil spills are well-known to have detrimental effects on birds, plants, and fish. It is also increasingly important to ensure cars and engines do not leak and stormwater runoff is reduced to avoid damages to fragile ecosystems.