In the list of environmental pollutants, mercury is one of the first places. It is mercury, its inorganic and especially organic compounds belong to extremely toxic substances of the first class of danger.Mercury has been known since ancient times, it is mentioned in the writings of Aristotle, Theophrastus, Pliny the Elder, Vitruvius and other ancient scholars. The Latin name for this metal is “Hydrargium”, given to mercury by Greek physician Dioscorides (1st century B.C.), means in translation “silver water”. The most important and ancient in Ukraine is the Mykytiv mercury deposit, which was opened in 1879. and operated since 1885. Production of mercury until 1914 was 300–400 t/year (most of it was exported). After the revolution and the war it was slowly recovered (127 tons in 1926), in 1935–1940 it is annually brought to about 300 tons. After the Second World War, the Mykytiv deposit was built. Discovered in it reserves (up to a depth of 300 m) were evaluated in 6.000 tons in 1927, after deep drilling was introduced in the 1960s. they have increased slightly. In the world economy, mercury is widely used in the electrical engineering and instrument industry, laboratory and medical practice, in the production of chlorine/alkali, in agriculture (included in fertilizers), in small-scale mining of gold and silver and other fields. No other chemical element belonging to the first class of danger has such wide use in production processes, products, substances and such multivariate penetration into the organism (with air, food, water, through the skin) as mercury and its compounds. The main source of mercury poisoning is mercury vapor and dust of mercury compounds. The toxicity of metallic mercury is due to the fact that while inhaling its vapors more than 80 % of the mercury is absorbed by the brain, kidneys and other internal organs, leading to he devastating consequences primarily on the central nervous system and kidneys. Mercury semi withdrawal period from humans is from 35 to 96 days. The average semi withdrawal period from the blood is 65 days, from hair 72 days, in total from the organism - 76 days. A longer semi withdrawal period of mercury from the brain than from other organs has been recorded in experimental animal searches. In humans, high levels of mercury in brain tissue were detected 10 years after it ceased contact with a toxic substance. Mercury poisoning can be acute or chronic. In everyday life, most often find the second option.

People lose hearing more often than we can imagine. Loss of hearing or deafness today is one of the most common occupational diseases not only in Ukraine but also in the world. Every day we are accompanied by a whole range of the most diverse sources of noise - household appliances at home and in the office, neighbors repairs, televisions, the road to work - metro, people in public transport or loud headphones music. And this can not be avoided, because each of us lives in a society, co-exists with other its representatives. All our life – a global communication. Many experiments found that noise is a general biologic stimulus and under certain conditions can affect all human life systems. The influence of noise on the human auditory organ is most fully studied. Intense noise, especially at high frequencies – 4000 Hz or more, with daily exposure leads to a professional illness – hearing loss, the symptom of which is the slow loss of hearing on both ears. According to official statistics of the World Health Organization, more than 5% of the Earth's population suffers from a disabling hearing loss. That is, such loss results not only in the deterioration of hearing quality, but also has certain social consequences, namely: more than 360 million people around the world have hearing problems (about 328 million adults and 32 million children); 1.1 billion teenagers and young people are at risk of hearing loss mainly due to listening to high-volume music as well as excessive noise levels; more than a third of people lose hearing as a result of excessive noise levels in the workplace. The rest is congenital deafness, loss of hearing due to various diseases and injuries; an average of almost ten years is passed before hearing impaired people turn to a doctor; studies have shown that about 1/3 of people over 65 years have hearing problems.