New research reveals alarmingly high levels of mercury in Danish fish and shellfish near a former chemical factory site in Denmark, raising serious concerns among scientists—despite the area being reopened to recreational fishing.
Polluted Waters Reopened for Fishing Despite High Mercury Levels
Recent studies conducted by Aarhus University and Danish broadcaster TV 2 have detected dangerous concentrations of mercury in oysters, mussels, and Danish fish caught near the former Cheminova chemical factory in western Denmark. This factory, located on Harboøre Tange, was responsible for producing pesticides from the 1950s until it ceased operations, leaving behind some of the country’s worst cases of long-term environmental contamination. The tests show that old pollution is still a problem.
For over 40 years, fishing in the surrounding waters of Nissum Bredning, near the towns of Thyborøn and Harboøre, was prohibited due to pollution concerns. However, as of July 1, 2025, Denmark’s Ministry of Food, Agriculture, and Fisheries lifted the ban, allowing private individuals to fish for personal use—even though new tests show pollutant levels remain dangerously high. Many are unsure if it is safe to fish there.
Concentrations Far Above Environmental Limits
Shellfish samples analyzed between 2023 and 2025 show that mercury levels in oysters ranged from 100 to 245 micrograms per kilogram, significantly surpassing the European environmental threshold of 20 micrograms per kilogram for Danish fish. Mussels contained between 85 and 139 micrograms per kilogram, and even small Danish fish species like the gudgeon showed mercury concentrations of 97 micrograms per kilogram.
To emphasize the scope of the issue: these measurements are up to 12 times higher than environmental safety limits—and the second-highest ever recorded nationwide since 1998. The only location with higher levels was Copenhagen Harbor.
Although these values are below the human food safety limit of 500 micrograms per kilogram, scientists warn against consuming the seafood due to long-term health concerns and the risk of compounded exposure, often referred to as “cocktail effects” from multiple contaminants.
Legacy of Chemical Waste and Environmental Damage
The Cheminova factory dumped hazardous chemical waste in the 1950s and 1960s, much of it legally under state permits. One major site, known as Høfde 42, remains a chemical hotspot. In 2006, authorities installed a 600-meter-long steel barrier to prevent further leakage into the North Sea. Nonetheless, the site is still estimated to contain more than 100 tons of toxic substances, including at least 7 tons of mercury.
Besides the Høfde 42 waste depot, two other locations tied to Cheminova—the original and current factory grounds—are also classified among Denmark’s ten most critical pollution sites.
Health Concerns for Humans and Wildlife
Experts are particularly concerned about the biological impact on local ecosystems. Elevated mercury levels are known to interfere with reproductive health in marine animals, which could ultimately affect entire fish populations. Moreover, even though the current levels detected don’t pose an immediate danger to humans, they are uncomfortably close to thresholds where consumption would officially be deemed unsafe.
Scientists highlight that children and pregnant women are especially vulnerable, as mercury can cross the placenta and impair fetal development. Despite this risk, the government has allowed fishing to resume, although the commercial sale of the seafood remains prohibited.
Lack of Clear Government Oversight
Authorities have come under fire for lifting fishing restrictions without what critics consider adequate scientific review. While the Danish Environmental Protection Agency acknowledged mercury is a widespread problem, it did not address how it plans to respond to the latest findings. Meanwhile, the Food Administration stated that it believes continued bans aren’t necessary as long as contaminated seafood isn’t sold commercially.
Local government leaders from the Central Denmark Region, responsible for environmental oversight in the area, expressed frustration that national authorities lifted restrictions without conducting thorough updated sampling beforehand. A full containment of polluted areas is not expected before 2026.
Call for Urgent Action
Environmental scientists insist that a comprehensive action plan is needed immediately. Contamination control efforts must not only prevent worsening conditions but actively reduce the existing threat. Only then, they argue, can both marine life and human health be safeguarded from continued exposure to one of the world’s most toxic substances.
