Caltrans Spotlights Top Six Pollutants Degrading California's Water Quality

May 18, 2022

3 Min Read
Caltrans Spotlights Top Six Pollutants Degrading California's Water Quality

SACRAMENTO, Calif. -- As part of its "Let's Change This to That" public education campaign, Caltrans today is sharing the top sources of stormwater pollution and ways to prevent them from contaminating California's waterways. As stormwater travels into storm drains, it captures pollutants from highways, streets, sidewalks and yards that flow into waterways. The top six pollutants have an outsized impact on the water quality of lakes, rivers, streams and the ocean, and many are preventable through small actions Californians can take.

The following lists the top six pollutants and actions to stop them at the source:

  • Trash and litter: Properly secure items in truck beds and put trash and recycling in the correct bin.

  • Sediments: Prevent soil erosion by using mulch in the garden, planting trees and shrubs, and sweeping driveways instead of hosing them off.

  • Nutrients: Avoid overfertilizing lawns and plants and limit vegetation waste by keeping fallen leaves out of storm drains.

  • Bacteria: Limit pet and RV waste by picking up after your pet and using appropriate RV dumping stations.

  • Metals: Regularly check tire pressure, change oil and fluids, and use commercial car washes to prevent metals generated from vehicle, tire, and brake wear from ending up on highways.

  • Pesticides: Use organic pesticides and properly dispose of unused portions.

Caltrans is tasked with managing stormwater runoff and mitigating pollution within its 350,000 acres of right of way, which includes more than 15,000 centerline miles of highways. This effort involves picking up roadside litter and clearing out storm drains to preserve roadway safety and drivability during all types of weather conditions.

Unlike water that goes down the sink or toilet in a home, stormwater is untreated and flows directly into lakes, rivers and other waterways. Stopping pollutants at the source is critical Caltrans' efforts to keep stormwater runoff clean.

"Preventing stormwater pollution requires the help and support of every Californian, and it starts with keeping highways and roadways clean," said Steven Keck, Acting Director of Caltrans. "Californians must work together to take necessary steps to prevent pollution at the source and keep our waterways clean."

Summer is the peak season for recreation in and around local waterways. This year, as hot, dry weather is expected to intensify drought conditions throughout the state, Caltrans is amplifying water quality as a top priority.  

During a drought, the state's lakes, rivers, and streams have lower water levels, which leads to a higher concentration of pollutants. By preventing a buildup of metals, trash and other pollutants on highways and roadways in dry conditions, Californians can help keep pollutants from traveling into local waterways during rainstorms.

The "Let's Change This to That" stormwater public education campaign is calling on Californians to pledge to do their part to keep stormwater clean. Visit to take the pledge and learn more about the sources and pathways of stormwater pollution.

About the Campaign
"Let's Change This to That" is a three-year public education campaign led by Caltrans to raise awareness and increase understanding of the sources and pathways of stormwater pollution throughout California. The campaign provides resources for people who live, work, and play in California's unique communities to spur behavior change in a way that leads to improved water quality. The campaign complements Clean California, a three-year, statewide litter reduction and beautification program. For more information, visit

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