# Mercury Contents in the Liver, Kidneys and Hair of Domestic Cats from the Warsaw Metropolitan Area
###### Abstract  
Mercury is a highly toxic element subject to bioaccumulation, increasing its harmful effects on living organisms over time. In the present study, total mercury contents were determined in the liver, kidneys and hair of cats from Warsaw and its suburban areas. The study took into account the influence of the age, sex and living conditions of the animals. Samples were obtained between 2014 and 2016, and mercury contents were determined by atomic absorption spectrometry (AAS). The average mercury concentrations in the tissues studied were 0.025, 0.026 and 0.030 mg\(\cdot\)kg\({}^{-1}\) in the hair, kidneys and livers of the individuals tested, respectively. Higher values were recorded in animals from the city area, and an increase in this metal with the age of the cats was also found. The average contents of mercury in the tissues studied were within the range of the recommended reference values, which in this case indicates low environmental exposure of animals to mercury. mercury; domestic cat; liver; kidney; hair; environment +
Footnote †: journal: Medical  
(less than 20% of the ingested dose), whereas methyl derivatives are absorbed at a rate of approximately 90% [4; 5]. The problem of environmental monitoring in the context of mercury pollution is still current because incidents related to its uncontrolled release from industrial sources continue to happen, and the element remains a threat, not only to aquatic systems. The rapid emission of mercury into the environment took place in the 1920s and was linked to its broader scope of industrial use and release, particularly during the combustion of energy raw materials. In the industrialized countries, the peak of mercury emission was between the 1960s and 1970s. Emissions of this metal started to fall rapidly in the 1980s only thanks to efficient corrective and preventive actions [17]. However, quantities circulating in the environment were released many years ago, and currently it is highly difficult to assess how much mercury comes from re-emission [2; 3; 18; 19]. For decades, many actions were undertaken that aimed at reducing the release of mercury compounds of anthropogenic origin into the environment. The Minamata Convention definitely had a most important role, as it set out the legal framework for the protection of the health of people and the environment against the toxic effect of mercury [3; 20]. It has been estimated that Poland is one of the major emitters of mercury in Europe. Data from 2016 indicate that the country is responsible for approximately 18% of the total emissions of this metal into the atmosphere on the European continent [21]. Despite the many actions aiming at the reduction of pollution emissions, it is estimated that the biosphere in Central Europe is more exposed to mercury than the other regions of the continent [2; 19; 22; 23]. Thus far, research on tissue contents of mercury has been conducted mainly in humans and free-living animals, whereas data concerning its levels in domestic animals are scarce. The domestic cat is a species that remains in a close relationship with humans, and its longevity enables the observation of long-term effects of certain environmental factors, including the bioaccumulation of toxic elements in tissues. For this reason, it has been assumed that it is a good indicator species which should be used in analyses of the quality of the environments of people living in urban agglomerations [24; 25; 26; 27; 28]. Initially, the research concerning contents of mercury in animal and human organisms was conducted mainly on the basis of liver and kidney sample analyses. In recent decades, analysis of contents in common integument derivatives, such as hair, was also introduced. Toxic elements undergo accumulation in different organs and structures of organisms, as well as biotransformation, including methylation and demethylation, and processes of excretion, and occur in all excretions and secretions.