Mercury is a metal found in the environment. When breathed or absorbed through the digestive tract or the skin, it can cause damage to the nervous system. Mercury poisoning is reported not only from industrial environments but also from the consumption of large quantities of predatory fish (pike, bass, walleye), marine mammals and game. Three forms of mercury can be found in the blood (elemental, inorganic and organic). It is the organic form (methylmercury), found in food, that is most toxic. Some people are also hypersensitive to the mercury found in dental fillings. Results are expressed in nanomoles of total mercury per litre of blood (nmol/L). This result is divided by 5 to compare it with data expressed in µg/L (micrograms per litre) or ng/mL (nanograms per millilitre). (Example: 50 nmol/L ÷ 5 = 10 ng/mL or 10 µg/L.)
The higher the blood mercury, the greater the exposure to mercury. However, the toxicity is about 5 times greater if it involves methylmercury rather than elemental or inorganic mercury. Blood levels greater than or equal to 60 nmol/L or urine levels greater than or equal to 100 nmol/L are subject to mandatory reporting to the public health department.