Mercury, selenium, PCBs and fatty acids in fresh and canned fish available on the Slovenian market

doi:10.1016/j.foodchem.2010.06.040

Food Chemistry

Volume 124, Issue 3, 1 February 2011, Pages 711-720

https://doi.org/10.1016/j.foodchem.2010.06.040 Get rights and content

Abstract

In order to contribute to the general understanding of the risks and benefits of consuming fish and fish products, total mercury (THg), monomethylmercury (MeHg), polychlorinated biphenyls (PCBs), selenium (Se), n-3 and n-6 fatty acids were determined in fresh and canned fish on the Slovenian market. Furthermore, the mercury exposure of pregnant women in Slovenia was assessed by determining total mercury (THg) in hair, and through fresh and canned fish consumption obtained by a food frequency questionnaire. Based on the frequency of fish consumption and levels of MeHg, THg and PCBs determined in the present study, it can be concluded that fish available on the Slovenian market do not represent a health risk. It was also confirmed that fish are important sources of selenium and n-3 fatty acids.

Introduction

Fish are beneficial to human health because of their high nutritional value. They are rich in protein with essential amino acids, macroelements (calcium, phosphorus, fluorine and iodine in marine fish), microelements (selenium, zinc), fat-soluble vitamins and unsaturated fatty acids. The fundamental difference between fish and other animals is in their high levels of n-3 fatty acids such as docosahexaenoic acid (22:6, n-3, DHA), eicosapentaenoic acid (20:5, n-3, EPA) and docosapentaenoic acid (22:5, n-3, DPA). They play an important role in the prevention of development of some diseases, especially in the development of cardiac and circulatory disorders and they reduce mortality in patients with coronary diseases (Kris-Etherton, Harris, & Appel, 2002). On the other hand, fish can also contain chemical contaminants such as toxic metals (mercury, arsenic, lead and cadmium), polychlorinated biphenyls (PCBs), organochlorine pesticides, aromatic hydrocarbons, dioxin-like polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, dibenzofurans, polychlorinated diphenyl ethers, polybrominated diphenyl ethers and polychlorinated naphthalenes.

Due to their contents of n-3 fatty acids, fish are considered especially important to prenatal development of the human nervous system. DHA accumulates rapidly in the central nervous system during the last trimester of pregnancy and the first 18 months of human postnatal life. Infants can receive DHA from their mother or can synthesise DHA from essential fatty acid precursors. Fish are also a significant source of the monomethylmercury cation CH₃Hg⁺ (termed as MeHg in this manuscript) and the foetal brain is more sensitive than the mature organ to MeHg. The threshold level for neurological effects in adults was estimated at about 50 mg/kg of mercury in hair (Swedish Expert Group, 1971). This level may be compared with an estimated threshold as low as 10 mg/kg for prenatal effects (Cox et al., 1989). Furthermore, MeHg consumed in diet might represent a risk of prenatal damage (Clarkson, 2002).

Fish are also an important source of selenium (Se). Humans and animals require selenium for the functioning of a number of selenium-dependent enzymes. It is a trace element that is essential in small amounts, but can be toxic in larger amounts. It is also well known that mercury and selenium bind to form mercury selenides with extremely low solubility, which are thought to be metabolically inert. Numerous studies have shown selenium supplementation counteracts the negative impacts of exposure to mercury in all investigated species of mammals, birds and fish (Beijer and Jernelov, 1987, Culvin-Aralar and Furness, 1991). However, little is known about the potential protective effects of dietary selenium against MeHg neurotoxicity in humans (National Research Council, 2000).

Davidson et al. (2008) tested the hypothesis that the intake of selected nutrients in fish or measures of maternal nutritional status may represent important confounders when estimating the effect of prenatal MeHg exposure on child development. The study took place in the Republic of Seychelles, where fish consumption is high. The primary analysis examined the associations between MeHg, maternal nutritional measures and the scores of children on the BSID-II (Bayley Scales of Infant Development-II) and showed an adverse association between MeHg and the mean Psychomotor Developmental Index (PDI) scores at 30 months. However, their results contrast with those found in studies carried out in the Faroe Islands (Grandjean et al., 1998, Grandjean et al., 1997). There were several differences between these studies and the populations in general but the most important reason for different results seems to be the diet consumed by Faroe Islanders that included whale, while the Seychelles Islanders diet did not. The whale is known to contain higher levels of PCBs, MeHg and possibly other toxins compared to fish (Raymond & Ralston, 2004).

In order to ascertain the safety of fish consumption in Slovenia and to contribute to the general understanding of the risks and benefits of consuming fish and fish products, the aim of the current study was to determine the levels of total mercury (THg), MeHg and the levels of PCBs, as well as the quantity of some components that are essential for a balanced human diet (Se, n-3 and n-6 fatty acids) in fresh and canned fish available on the Slovenian market. Since it is believed that human exposure to MeHg occurs mainly from eating fish, the mercury exposure of Slovenian pregnant women was assessed from determination of THg in hair and from the frequency of fish consumption.

Section snippets

Collection and storage of samples

Various species of fresh and canned fish of different geographical origin available on the Slovenian market were collected randomly in the capital city of Ljubljana. Fresh fish were bought from the fish market, while canned fish were bought in various supermarkets. The samples were collected in March, April and May of 2005. The edible part of fresh fish was homogenised with the food mixer (Kenwood). A sample was obtained from at least two fish from the same species. The content of fish in tins

Mercury in fish

The results for THg and MeHg levels in fresh and canned fish are shown in Table 1, Table 2. According to the European Commission Regulation (EC) No. 78/2005 of January 19, 2005 the maximum allowed level of mercury in the species anglerfish, swordfish and tuna is 1 mg/kg. For other fishery products and fish muscle the maximum allowed level of mercury is 0.5 mg/kg. In none of the tested canned fish samples did the concentration of mercury exceed the permissible limits. Only in four samples of fresh

Conclusions

Based on the present study and the current JECFA PTWIs for MeHg, it can be concluded that the levels of MeHg in fish available on the Slovenian market consumed by Slovenian pregnant women do not represent a health risk for pregnant woman and for susceptible developing fetuses and that fish represent an important source of selenium and n-3 fatty acids. Furthermore, the frequency of fish consumption of Slovenian pregnant women is relatively low. Considering the PCB tolerance limit recommended by

Acknowledgements

This work was supported by the EU through its Sixth Framework Programme for RTD (contract no FOOD-CT-2006- 016253). It reflects only the author’s views. The Community is not liable for any use that may be made of the information contained therein.

The authors are grateful to Saša Volk, Viktor Kure and Antonija Zajc who performed the analyses of THg, Se and fatty acids in fish. The authors are also grateful to all pregnant women who participated in this study and to the personnel of the “Jožef

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Mercury, selenium, PCBs and fatty acids in fresh and canned fish available on the Slovenian market

Abstract

Introduction

Section snippets

Collection and storage of samples

Mercury in fish

Conclusions

Acknowledgements

Journal of Chromatography A

Analytica Chimica Acta

Environment Research

Neurotoxicology

Environmental research

Neurotoxicology and Teratology

Talanta

Environmental Toxicology and Pharmacology

Marine Pollution Bulletin

Environmental Research

Food Chemistry

Food Control

Food Chemistry

Nutrition Research

Chemospehere

Total mercury and methyl mercury concentrations in fish from the Persian Gulf and the Caspian Sea

Water Air Soil Pollution

Prenatal low-level mercury exposure and child development in an Italian coastal area

Seychelles Medical and Dental Journal

Ecological aspects of mercury–selenium interactions in the marine environment

Environmental Health Perspectives

Methyl mercury and inorganic mercury in Swedish pregnant women and in cord blood: Influence of Fish Consumption

Environmental Health Perspective