What if the technology designed to reduce air pollution was secretly polluting the ocean instead?
This is exactly the concern surrounding exhaust gas cleaning systems (EGCS), or scrubber systems used on many commercial vessels today. While these systems are designed to help ships meet air pollution regulations, they discharge the contaminants into surrounding waters, creating a new area of concern. States such as California and federal regulators should require more stringent monitoring and reporting of ship scrubber washwater discharges, as these discharges can harm marine ecosystems if public oversight is limited. As concerns about ocean pollution continue to grow, policymakers must ensure that efforts to improve air quality do not come at the expense of water quality.
The debate over ship scrubber systems highlights a larger question in environmental policy: should a technology be considered a solution if it shifts pollution rather than eliminates it? According to an article by Clear Seas, to comply with the IMO regulations on sulfur emissions in 2020, shipping companies had two options: first, switching to more expensive low-sulfur fuel; or second, switching to alternative fuels such as liquefied natural gas. Second, installing scrubber systems and continuing to use cheaper high-sulfur fuel. As a result, many companies chose the lower-cost alternative and equipped their ships with these systems, with proponents viewing them as a cost-effective way to comply with international regulations while meeting sulfur-emission requirements. However, critics argue these systems transfer pollution from the atmosphere into the ocean through wastewater discharge. Although scrubbers help reduce sulfur emissions from ships, their effects on ocean health deserve just as much attention. As more research emerges about the effects of scrubber wastewater, regulators should scrutinize whether these systems are truly the long-term solution they were intended to be.
Scientific evidence suggests that scrubbers can negatively affect water quality in many ways. A peer-reviewed article published in Environmental Sciences Europe states that the use of scrubbers may increase pollutant concentrations in estuaries and ports. The contaminated washwater contains polycyclic aromatic hydrocarbons (PAHs), which are chemicals found in coal, oil, and gasoline, as well as heavy metals such as vanadium, nickel, and zinc. In addition, the wastewater is also highly acidic, having a pH ranging from 2.5-3.5 compared to the surrounding seawater having a pH of around 8. Ships fitted with scrubbers also release approximately 10 gigatonnes (10 billion metric tons) of scrubber washwater into the ocean each year, with about 80 percent of these discharges occurring within 200 nautical miles of shore. These findings raise questions about whether scrubbers solve one environmental problem while creating another potentially even more serious one.
Furthermore, these pollutants do not biodegrade naturally and can enter marine food chains, accumulating over time. A study published in Marine Pollution Bulletin found that scrubber discharge reduces algal growth and impairs the survival, reproduction, and development of copepods and mussel larvae. Because algae and plankton-like organisms form the foundation of marine food webs, disruptions to these populations can ripple throughout the ecosystem and affect larger species that depend on them. This evidence suggests that the impacts of scrubber wastewater may extend far beyond the organisms directly exposed to it.
The ramifications of this issue extend beyond water quality, as California's economy and coastal communities depend on healthy marine ecosystems. Industries such as tourism, commercial fishing, and shipping contribute approximately $44 billion annually to California’s GDP and approximately $143 billion annually to the U.S. economy. If these pollutants continue to accumulate in marine environments, it could affect the long-term health of California’s coastline and impact the millions of people who rely on a clean bay every year.
Community members can support organizations such as the California State Coastal Conservancy, which are working to protect California's coastline, and encourage policymakers at the city, county, state, and federal levels to strengthen oversight of ship scrubber wastewater. If we fail to address this issue now, we risk overlooking a source of pollution that could have lasting consequences for marine life and coastal communities. Cleaner air should not come at the cost of a dirtier ocean.
The views expressed in this op-ed are those of the author and do not necessarily reflect the official position of the Saving the Sea Organization. This piece was written as part of the Emergent Fellows Program, our summer fellowship in environmental policy and advocacy.