In DepthPollution

Shipping rule cleans the air but dirties the water

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Science  14 May 2021:
Vol. 372, Issue 6543, pp. 672-673
DOI: 10.1126/science.372.6543.672

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Summary

In an unwelcome twist, a global effort to curb pollution from the heavy fuel oil burned in many ships appears to be encouraging water pollution instead. A 2020 regulation aimed at cutting sulfur emissions from ship exhaust is prompting many owners to install scrubbing systems that capture pollutants in water and then dump some or all of the waste into the sea. Some 4300 scrubber-equipped ships are already releasing at least 10 gigatons of such wastewater each year, often in ports and sometimes near sensitive coral reefs, researchers reported last month in the first effort to quantify and map the releases worldwide. The shipping industry says pollutants in the waste don't exceed national and international limits, and that there's no evidence of harm to marine ecosystems. But some researchers fear scrubber water, which includes toxic metals such as copper and carcinogenic compounds called polycyclic aromatic hydrocarbons, poses a rapidly growing threat. So far, few researchers have tested scrubber water on marine life. One laboratory study, published last month in Environmental Science & Technology, found that samples of scrubber wastewater from three North Sea ships harmed the development of a tiny crustacean that is a key part of Atlantic Ocean food webs.

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