The Presence of Mercury in the Tissues of Mallards (Anas platyrhynchos L.) from Włocławek Reservoir in Poland

Biol Trace Elem Res The Presence of Mercury in the Tissues of Mallards (Anas platyrhynchos L.) from Włocławek Reservoir in Poland Jerzy F. Żarski 0 1 2 Michał Skibniewski 0 1 2 Ewa Skibniewska 0 1 2 Tadeusz P. Żarski 0 1 2 Teresa Majdecka 0 1 2 0 Department of Morphological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences - SGGW , Nowoursynowska 159 C, 02-776 Warsaw , Poland 1 Department of Animals Environment Biology, Faculty of Animal Science, Warsaw University of Life Sciences - SGGW , Ciszewskiego 8, 02-786 Warsaw , Poland 2 Halina Konopacka Higher School of Physical Culture and Tourism , Andrzeja 1, 05-800 Pruszków , Poland The study aimed at determining the degree of mercury contamination of mallards, game waterbirds migrating from the regions of the unknown degree of contamination and establishing whether the consumption of their meat comprises a hazard to human health in view of the binding norms concerning the mercury content in food products. The investigations were carried out on 30 mallards shot during the duck shooting season in which mercury concentrations in the muscles, liver, and kidneys were determined using the cold vapor atomic absorption spectrometry (CV-AAS) method. The mean Hg concentration in the investigated tissues in all birds studied amounted to 0.110, 0.154, and 0.122 mg kg−1 for the muscles, kidneys, and liver, respectively. The study indicated statistically significant (p ≤ 0.01) positive correlation between all of the organs examined. Animals were divided into two groups differing in both absolute values of Hg concentrations and those measured in individual tissues. In particular organs of birds representing the first group, the presence of highly significant correlation (p ≤ 0.01) was observed in all organs examined. In the second group, highly significant positive correlation between Hg concentrations in the liver and kidneys and highly significant negative dependence between the liver and muscles was noted. The examinations revealed that some birds must have come from regions of a high degree of mercury contamination. Mercury; Mallard; Liver; Kidneys; Muscles - Mercury is a metal that may enter the environment both by natural processes of the earth’s crust and as a result of human activity. Released to the biosphere, mercury undergoes complex transformations, circulating between the atmosphere, terrestrial systems, and the aquatic environment. Plants, animals, and humans are subject to exposure to its toxicity, as long as mercury remains in its biogeochemical cycle [1–4]. Three basic forms of mercury occur in the environment: metallic mercury (Hg0), inorganic mercury (mercurous, Hg22+, and mercuric cations, Hg2+), and organic mercury compounds [2]. Metallic or elemental mercury prevails in the atmosphere [5]. Inorganic mercuric compounds include mercury salts used in numerous technological processes. They are also found in electrical cells, fungicides, and disinfectants [6]. Organic forms of mercury are compounds in which the element binds with at least one carbon atom through a covalent bond. Methylmercury is one of the most common forms of organic mercury. This compound has the ability to accumulate and biomagnify at each step of the trophic chain of the aquatic ecosystems [7–10]. The toxic effects of mercury observed in homoiotermic vertebrates affect mainly the nervous, urinary, and reproductive systems [10, 11]. The inorganic mercuric compounds tend to accumulate in the kidneys and liver, whereas methylmercury penetrates into all the tissues of the body, including the skeletal muscles, nervous system, as well as the structures of the common integument [3, 10]. Numerous species of aquatic birds have been used for decades as bioindicators of the pollution of their habitats. The mallard (Anas platyrhynchos) is one of the most commonly studied species within the group of bioindicators. Among the reasons, underlying its common use in environmental studies is the wide distribution of the wild duck, since it occurs in the nearly entire Palaearctic ecozone [10]. In addition, the mallard is an excellent object of studies due to large populations, apparent sexual dimorphism, and longevity, which enables observations of long-term exposures to selected pollutants [12]. Not without significance is the fact that the mallard is a game species, the muscle tissue of which is consumed by humans. Therefore, knowing the content of toxic metals in mallard’s body is important in terms of food safety. Despite a large number of reports on the studies of heavy metals in the tissues of mallards, the data on mercury levels in the organs of the mallards inhabiting the area of Poland and other European countries are relatively scarce [9, 10]. In terrestrial animals, mercury enters the body through the respiratory system, gastrointestinal tract, and through the skin [9, 13]. It should be stressed, however, that there are considerable differences in mercury abso (...truncated)