Dietary composition in Greenland 2000, plasma fatty acids and persistent organic pollutants

Abstract

Human exposure to pollution in the Arctic presents a potential future health risk for the local populations. Epidemiological studies in Greenland have shown that human blood levels of several organic contaminants are very high, especially in the North where people depend on local food. In East Greenland (Ittoqqortoormiit (Scoresbysund)) the population shows the highest blood levels of several persistent organic pollutants found in Arctic countries, especially PCB, the levels of which exceed Canadian guideline levels. As in other Arctic countries, the direct source of these contaminants is the diet, and it is, therefore important to monitor the composition of the diet along with other factors which may influence the metabolism and thereby the accumulation of toxic substances. This project is part of the human health program of the ongoing circumpolar ‘Arctic Monitoring and Assessment Programme’. Dietary survey results (Semiquantitative Food Frequency questionnaire from 192 men and women from East Greenland and 48 men from Uummannaq West Greenland) were analysed along with other factors (lifestyle and anthropometric factors), blood lipids, fatty acid profiles, and concentrations of persistent organic pollutants (POPs). The dietary survey showed that the contributions of traditional food provided 25–30% of the total energy intake. However, the relative monthly meal intake of seal, whale, polar bear, fish and game, and the composition of imported food, varied between districts. The blood fatty acids (FA), e.g. the n-3/n-6 ratio (Uummannaq 0.70, Ittoqqortoormiit 0.37 Tassiilaq 0.45) showed moderate associations with the overall reported food composition. The n-3 fatty acids were associated with the well-known lowering effect on serum-triglyceride levels. The strongest associations between diet and plasma fatty acids were found for docosapentaenoic acid, C: 22.5.3 which strongly correlated with reported seal, and polar bear intake (P=0.01** and 0.04*, respectively), consistent with the fact that seal and polar bear blubber contain much higher concentrations of C: 22.5.3 than other sea mammals and fish. Seal and polar bear intake, and in particular all the plasma n-3 fatty acids, were significantly correlated with organic contaminant concentrations, (betaHCH, chlordanes, DDTs, Hexachlorobenzene, Mirex, PCBs, and toxaphenes) P<0.01**. Conclusions: The strongest correlations between POPs and fatty acids were found with C: 22.5.3, strongly indicating seal and polar bear blubber as the main contributors of POPs to the local population.

Introduction

Epidemiological studies in Greenland have shown that human blood levels of various anthropogenic contaminants are very high (AMAP, 1998). In East Greenland (Ittoqqortoormiit (Scoresbysund)) the population shows the highest blood levels of several persistent organic pollutants found in Arctic countries especially PCB (Deutch and Hansen, 2000). As in other Arctic countries the direct source of these contaminants is the diet, and it is, therefore important to monitor the diet and other factors, which may influence metabolism.

The diets of Arctic Indigenous Peoples consist of both traditional food and imported (market) foods. Although it varies by country, locality, sex and age group the traditional food yields 10–40% of the total energy intake and this percentage has decreased over the last 30–40 years (Deutch, 2002).

In Greenland, recent dietary surveys have shown that the relative intake of traditional food is 25–30% by weight (Pars, 2000, Deutch, 2002, Deutch, 2003). The traditional foods are the main contributors of protein, fat, and most minerals (Fe, Zn, Se, I), vitamin D, and especially of the essential long chain n-3 fatty acids, which in several ways can be considered as health promoting.

The high relative content of n-3 fatty acids in the traditional/country foods presumably provides some protection against cardiovascular diseases, and various other diseases of an affluent industrialized society (Jul et al., 1994). However, human blood levels of marine n-3 fatty acids are strongly associated with blood levels of persistent organic pollutants (POPs), because the main sources of POPs are fats (blubber) from marine animals. Thus the traditional food is the main contributor of persistent organic pollutants, particularly if the content of marine fish and mammals is high (Bjerregaard et al., 2001).

The correlation between the intake of traditional food items as determined by dietary surveys, and blood levels of anthropogenic substances, have been demonstrated on both a group and a population basis for heavy metals (Hansen, 1990) and for organochlorines (Van Oostdam et al., 1999). Chemical analyses of food items of animal origin have provided ample proof that traditional food is a major source of heavy metals (Hg, Cd and some times Pb) and persistent organic substances (Johansen et al., 2000, Johansen et al., 2002). Furthermore, since the POPs are biomagnified through the food chain, the animals at higher trophic levels have, in general, higher blood levels of organic contaminants, although size and age also have an influence. Exposure estimates for heavy metals calculated from dietary intake data show good correlations with human tissue concentrations (Hansen and Pedersen, 1986, Hansen, 1990). Dietary exposure estimates of persistent organic pollutants (POP) have, so far, only been compared with human body burdens of POPs on a population basis, and no correlations between estimates of individual dietary intakes and individual blood levels of organic xenobiotics have previously been available. However, several studies have shown very significant positive associations between n-3 fatty acids in human lipid fractions and blood levels of both Hg (Hansen and Pedersen, 1986, Dewailly et al., 2001) and POPs (Deutch and Hansen, 2000) which makes the connection between intake of marine mammal fat (e.g. blubber) and organic pollutants highly probable.

The present study will assess the associations between self reported dietary food frequencies for indigenous peoples in East Greenland (n=192) and Uummannaq, West Greenland (n=48) and the levels of plasma phospholipid fatty acids (FA), and a number of lipophilic persistent organic pollutants, including 10 pesticides, 14 PCB congeners, five Toxaphenes. In particular it will focus on the long chain n-3 fatty acids, namely the eicosapentaenoic acid, EPA (C20.5.3), docosapentaenoic acid, DPA (C22.5.3) and docosahexaenoic acid DHA, (C22.6.3) both individually and using their mutual ratios as markers of subsistence marine animals.