What is Mercury?
According to the World Health Organization (WHO), "Mercury is a naturally occurring element that is found in air, water, and soil. Mercury exists in various forms: elemental (or metallic) and inorganic (to which people may be exposed through their occupation); and organic (e.g., methyl mercury, to which people may be exposed through their diet). These forms of Mercury differ in their degree of toxicity and their effects on the nervous, digestive, and immune systems, and lungs, kidneys, skin, and eyes." Mercury is a shiny, toxic, and silver-white metal that is liquid at room temperature. It occurs in the earth's crust naturally. "It is released into the environment from volcanic activity, weathering of rocks and as a result of human activity," as mentioned by WHO.
Health Effects of Mercury in Drinking Water
Mercury (especially Methylmercury) is a neurotoxin in nature, a chemical substance known or suspected of poisoning nerve tissues. According to the U.S. Environmental Protection Agency (EPA), the health effects of mercury depend on several factors, including the form of mercury, the amount of mercury in the exposure, the exposure time, the age and health of the individual, and more.
In a study by WHO for developing WHO Guidelines for Drinking-water Quality, the mercury level has been observed in the range of 5–100 ng/liter. Less than 0.5 μg/liter level of mercury has been found in the groundwater and surface water due to the natural occurrence. “A small number of groundwaters and shallow wells surveyed in the USA were shown to have mercury levels that exceeded the maximum contaminant level of 2 μg/liter set by the US Environmental Protection Agency for drinking water (Ware, 1989),” as mentioned in that study by WHO. Mercury absorption from water is around 15% or less, so if drinking water mercury is 0.5 μg/liter, then an average daily intake of inorganic mercury from drinking water would be around 1 μg.
The two major effects of mercury on humans are neurological and renal disturbance. Ingestion of acute doses of mercury of any form shows terminal symptoms, as given here;
- Shock
- Acute renal failure
- Cardiovascular collapse
- Gastrointestinal damage
Testing for Mercury in Water
The presence of mercury in various drinking water sources is a concern to public health. Usually, the concentration of mercury in drinking water sources is less than 0.5 μg/liter. However, it could be higher on some occasions, especially in the groundwater. The testing of mercury in water has Cold Vapor Atomic Absorption Spectrometry and Mercury Visual Detection Kit For Ground Water (MVDK). These methods are effective to measure total mercury (organic + inorganic) in drinking-water sources, groundwater, sea, brackish waters, surface, industrial and domestic wastewater, and more.
- Cold Vapor Atomic Absorption Spectrometry mercury testing method
This method has the range to determine mercury between 0.2-10 μg Hg/L. As per the US Environmental Protection Agency (EPA), “a known portion of a water sample is taken into a BOD bottle, an equivalent ground glass stoppered flask or other suitable closed container. It is digested in diluted potassium permanganate-potassium persulfate solutions and oxidized for two hours at 95°C. Mercury in the digested water sample is reduced with stannous chloride to elemental mercury and measured by the conventional cold vapor atomic absorption technique.”
- Mercury Visual Detection Kit For Ground Water (MVDK) mercury testing method
It is a simple, cost-effective, and sensitive visual colorimetric mercury testing method that instantly determines the portion of mercury in groundwater. This method uses the formation of a mercury complex to measure concentration based on coloration. It is highly suitable for periodic monitoring of mercury contamination in domestic water in mercury-affected areas.
Best Water Filters for Removing Mercury
Conventional chemical coagulation and mechanical filtration can help to remove up to 80% of inorganic mercury from water. However, these methods are effective only 20–40% for organic mercury removal. The activated carbon in a powdered and granular form is effective in the removal of inorganic and organic mercury. A reverse osmosis (RO) water filter that uses a sediment filter, activated carbon filter, and reverse osmosis membrane with multi-stage filtration provides important additional redundancies. Thus installing and using reverse osmosis systems for safe and pure drinking water is advised in residential applications with a private well where the source water contains mercury, or for additional peace of mind on a treated municipal water supply. Home Master RO systems can be expected to remove 95 – 98 % of mercury with input concentrations of 500 – 2,000 ppm.
Conclusion
Mercury (Hg) is a naturally found element in water, air, and soil in different forms, including organic, inorganic, and elemental. It is a highly toxic neurotoxin that affects the nerve tissues. Ingestion of mercury in any form may cause serious health issues for humans, especially pregnant women, and their children in utero. Reverse Osmosis (RO) systems are designed to remove harmful contaminations and dispense pure drinking water. Home Master RO systems with sediment filtration, activated carbon, and membrane filters are effective in removing impurities including mercury (Hg) from otherwise potable municipal or well water.