EDITOR'S NOTE: From August 2003 to March 2006, Dr. Bethune worked as a senior scientist in the department of seafood safety for the Norwegian government at the National Institute of Nutrition and Seafood Research (NIFES).
The quality of Norwegian farmed salmon has recently come into question with the Russian ban, illegal nitrate use, and a building body of evidence that consumers should limit their consumption.1-3
Norway farms about 570,000 tons of Atlantic salmon a year out of a world total of 1.25 million tons. In December of 2005, when Russians faced tons of cadmium coming down the Beijiang River from a zinc smelting plant in China, Russia's food safety officers announced they would be banning all fresh Norwegian salmon.1,4 The reasons cited were the findings of dangerously high levels of lead (18 mg/kg) and cadmium (0.7 mg/kg) in samples of imported farmed fish (salmon and trout) and, according to the chief food safety officer Sergei Dankvert, because Norway's monitoring system is not adequate.1,5
Norway refuted the findings for heavy metal levels described by the Russians by declaring them unbelievable.5 The levels cited exceeded all federal standards or guidance levels, and they had never been seen in Norwegian surveillance programs or in international assessments.6 Farmed salmon is considered a fatty fish, and the contaminants of primary concern are the fat-soluble persistent organic pollutants (POPs) such as dioxins, PCBs, brominated flame retardants, and pesticides, but not heavy metals. Was an analytical error responsible for the Russian results? For farmed rainbow trout, which is produced at a much smaller volume than salmon, the Norwegian authorities said they had located the same batch said to have the high levels of lead and cadmium. Independent laboratories in Sweden and Denmark showed in February that levels of lead and cadmium in the selected farmed rainbow trout were not elevated above the European Union maximum limit in farmed fish for lead (0.2 mg/kg) or cadmium (0.05 mg/kg). However, it is important to note that Norway could not locate any of the identified salmon, and none of the representative samples of the farmed salmon were subject to an independent analysis.
To examine this source, we need to return to the zinc smeltering plant in China. In the autumn of 2004, both France and Norway imported contaminated batches of zinc sulphate from China which was subsequently used as a pre-mixture ingredient in animal and fish feeds for many months.7,8 This was the third time since 2000 that cadmium contaminated feed ingredients imported from China had been reported to the European Union (EU). Zinc is an essential nutrient in both animals and fish, however, some of the by-products of zinc mining are lead and cadmium. The Norwegian Food Safety Authority (NFSA) reported that a 20 ton shipment of zinc sulphate for use in feeds was delivered to Norway containing 7-8% cadmium, about 1.5 tons, and that it was highly uncertain how much had been distributed to animals, fish, or the environment.8
The NFSA estimated that 3-5% of Norway's annual feed production, or 75,000 to 125,000 tons, was contaminated with cadmium.8 In January of 2005, surveillance samples of fish feed were taken and analysis in mid March showed cadmium contamination at 11-17 mg/kg feed. From these results and knowledge that the feed ingredients had entered the food chain, the NFSA is said to have considered a total ban on farmed salmon exports, but surprisingly did not follow through. New feed analyses on the 4th of April showed lower levels, and the next week the Norwegian Scientific Committee for Food Safety issued an opinion that indicated that there was no risk to food safety from these levels if the exposure was less than 4 months.9,10 After contaminated fish feed had been sent to Scotland, Canada, and the Faeroe Islands, the World Trade Organization (WTO) was notified and the feed scandal seemed to be over by the end of April 2005.11
Unfortunately, it was not over. In the first week of October 2005, Norway sent another WTO emergency notification for elevated cadmium levels in beef and sheep products.12 This notice again linked the source of contamination to the import of cadmium contaminated zinc sulphate that was used in animal and fish feed earlier in the year, and gave the unsettling conclusion "However, much is still unclear as to where and how the contaminated feeding stuffs is distributed." 12 The Russians identified the fish they found contaminated, after analysis by the Central Veterinary Laboratory in Moscow, were processed November 7th at their customs point in Izhorskij.13 The first week of December, when Russia notified Norway of contaminated fish, the district veterinarians normally responsible for such an incident were called off the investigation and details on the Norwegian companies involved were made secret by the central administration of NFSA.14 The handful of scientists that publicly questioned the safety of farmed salmon during this time were reprimanded by their state employers, subject to special comment by NFSA together with the state feed company EWOS, and even called national traitors by the Norwegian Export Council for Fish.15
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Claudette Bethune, Ph.D.. Norwegian farmed salmon production raises global concern. EnvironmentalChemistry.com. May 31, 2006. Accessed on-line: 5/5/2016