Protecting Blue Skies by Reducing Air Pollution

Reducing ship speeds significantly reduces one of the top sources of criteria air pollutants (notably NOx) impacting many coastal communities.

See The Impact

Photo: Matteo Paganelli

On this page

The Facts

How It Works

Measuring Progress

Verifification Partners

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Photo: Herson Rodriguez

The Facts

Silhouette of California with two cargo ships on water inside a blue circle.

In 2024, the program reduced air emissions by about 1,400 tons of nitrogen oxides (NOx) and 50,000 metric tons of regional greenhouse gases off California.

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The annual NOx reductions are equivalent to taking 900,000 cars off the road for a year.

A significant portion of ship emissions spreads into coastal communities. By reducing speed, ships help protect not only our blue skies but also the health of everyone who lives near the busy shipping lanes.

Illustration of a cargo ship with containers on the ocean, under clouds, in a blue circle.

Ships burn less fuel when they reduce speed, which not only saves on fuel costs but also produces fewer smog-forming pollutants.

Peak Ozone & Peak Migratory Season

In California, peak ozone season happens to also coincide with peak migratory seasons for endangered whales. When ships reduce speeds to help protect whales, they also reduce air pollution, creating a win-win for marine wildlife protection and air quality for people living in coastal communities.

Air Districts Have Been Involved Since the Beginning

The 2014 trial year included the Santa Barbara County Air Pollution Control District, Ventura County Air Pollution Control District, Channel Islands National Marine Sanctuary and the Environmental Defense Center. Both air districts faced challenges meeting the state standards for ground-level ozone, or smog. If cargo ships traveling along the coasts voluntarily slowed down fewer pollutants would be emitted and blown onshore.

And because a lower speed also benefits whales by reducing ship strikes and ocean noise, a successful coalition was born.

Four people smiling at an event; two hold whale tail trophies, one holds a framed whale photo.

Photo: Katie Abbott Photography

When ships reduce their speed to 10 knots, it decreases air pollution and emissions by about 27%.

Since the program’s inception, participating vessels’ slower speeds have resulted in a reduction of more than 200,000 metric tons of regional greenhouse gases.

The program has reduced NOx emissions by more than 5,900 tons since 2014.

How This Impacts Local Air Quality

This program has given us a very effective incentive to motivate cargo ships to voluntarily decrease their emissions.

2024 Methods & Results Report

Do air districts regulate emissions from ships?

When is ozone season?

The BWBS program runs during the period that coincides with peak ozone levels as well as the presence of blue, humpback, and fin whales near the California coast. This is typically late spring to through autumn. Ozone is more likely to form during this time due to the presence of heat and sunlight, which react with pollutants to form ozone, otherwise known as smog, which impacts the air we breathe.

What air pollutants does this program address?

What are some benefits of this program to coastal communities?

California Air District Partners

Coastal California air districts in the program protect our blue skies and promote healthy communities in many ways. To learn more about their mission and regional programs, click on the logos below.

Take Action to Reduce Air Pollution and Greenhouse Gas Emissions

Enroll your Fleet

Any company who operates container, car carrier, bulk cargo, or tanker vessels that pass through the Vessel Speed Reduction (VSR) Zones is eligible.

Click Here to Enroll

Photo: Ralph Clevenger Wildlife

A large MSC container ship sails across calm blue water under a hazy sky near distant mountains.

Become An Ambassador

Any company that ships goods with, or works with one or more participating shipping line is eligible to join.

Learn More

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Get Involved

Supply chain practices matter for biodiversity and air quality. Support responsible shipping practices for cleaner coastal air, safer whales, and a quieter ocean.

Ways To Get Involved

Photo: Robert Schwemmer