Introduction Mercury is a heavy metal found naturally in the environment. Mercury poisoning of occupational origin is widely identified as occupational disease. The industries where cases have been described are those dedicated to the manufacture of thermometers, barometers, as well as in gold mines and metal refineries such as zinc.

Methodology The case of a 30-year-old male, a boilermaker (welder assembler) who is part of one of the teams responsible for replacing the carbon steel tubes of the exchanger through which sulphurous gases circulate with mercury remains is described. The initial symptoms were diarrhoea with mucus and blood and gum inflammation, initially presenting a blood mercury concentration of 475.9mcg/L (NV=<10 mcg/L) and urine mercury concentration 939mcg/L (NV=<30 Mcg/L) (BAL INSHT <5 mcg/g creatinine), not receiving treatment until after 6 months with DMPS twice seeing a reduction in urinary values from 1830.47 to 7.38 mcg/L. As a clinical result of mercury poisoning he had severe mercurial erethism with dysthymia and aggressive behaviour, as well as a secondary complex visual disorder and a diarrheal syndrome due to secondary autonomic neuropathy.

Conclusion This paper aims to warn about the consequences of prolonged exposure to mercury especially for the central nervous system, as well as early diagnosis and timely treatment. On the other hand, note the importance of adopting an adequate and effective preventive system to protect the health of workers exposed to mercury.