Dietary Mercury Exposure in selected Norwegian Municipalities : The Norwegian Fish and Game Study, part C.

Abstract: Improved and detailed knowledge regarding dietary mercury exposure in the Norwegian population is considered important as part of a national monitoring of exposure to hazardous environmental contaminants. Mercury is still regarded an important pollutant in Norway, reflected in the priority list for the Norwegian Pollution Control Authority (Norwegian: Statens forurensningstilsyn, SFT) from 1996. This priority list, defined politically by the Norwegian Parliament, includes about 30 different chemical pollutants and is aimed at ending, or substantially decreasing, emissions of the chemicals listed. Mercury is also found on the “obs-list”, which is the environmental authorities` list of health and environment threatening chemicals that may represent a particular problem on a national level. The proclaimed goal by the Norwegian environmental authorities concerning mercury is that emissions should be “substantially decreased, at latest by the year 2010” (SFT 2004). Mercury is a metal that may be released from both natural and anthropogenic sources. It is estimated that less than half of the mercury pollution in Norway is released from national sources, the rest being depositions from atmospheric transportation from abroad (Berg et al. 2003). As mercury is able to circulate in the atmosphere probably as long as one year, it may be transported very long distances and is thus an issue of international concern. Even though many western countries (Norway included) have decreased their mercury releases during the last decade, countries in both Asia and Africa have had a substantial increase in their emissions (Fjeld & Rognerud 2003). This means that international agreements are necessary for an effective handling of the problem, and the United Nations are currently working on efforts to reach international agreements regarding the use of mercury (UNEP 2002). This does not negate, however, that local industrial emissions have been of great importance for local contamination in some parts of Norway. In the year 2000 it was estimated that about 290 kg of mercury were released from national sources in Norway, and about 50 % of this was discharged directly into sea and lakes (Berg et al. 2003). The most important sources in Norway is offshore industry (about 42 % of national releases in 2000), garbage disposals and renovation systems (21 %) and metal production (12 %) (Berg et al. 2003). One important implication of the long-distance atmospheric mercury transportation is that increased levels of mercury have been found in many lakes in the Scandinavian countries (Fjeld & Rognerud 2003). Studies have shown a north-south gradient of mercury levels in Norway, with higher levels in lake sediments and soils in the southern parts (Berg et al 2003). Internationally, the major concern regarding mercury in the environment is dietary exposure through the consumption of freshwater and marine fish (WHO 1996). Also in Norway, several studies have shown that mercury concentrations in pike, perch and trout in somelocations may be above the maximum level permitted on the commercial market (defined by the Norwegian Food Control Authority: 0.5 mg/kg generally and 1.0 mg/kg for pike) (Fjeld et al. 2001). However, although it is evident that especially freshwater fish may contain higher concentrations than what is considered safe for human consumption, no detailed monitoring of mercury concentrations exist for Norwegian lakes. Thus fish consumption restrictions for freshwater fish have been given on a general basis, and include avoiding consumption of pike, of perch above 25 cm, and trout and charr weighing more than 1 kg. These advises are primarily directed against pregnant and breast-feeding women, although the gener population is recommended not to eat these fishes more than once a month on a yearly basis (Matportalen 2004a) Some fjords have also been affected by local industrial pollution, and currently the Norwegian Food Safety Authority (Norwegian: Mattilsynet) recommend avoiding consumption of fish from Sørfjorden due to the high levels of mercury found in fish from this fjord (last evaluated in 2003) (Matportalen 2004b).