(NaturalNews) Mercury is a naturally occurring element, but it is also a danger to human anatomy -- a neurotoxin to the brain. According to the Agency for Toxic Substances and Disease Registry, overexposure to mercury can spur irritability, social anxiety, shyness and even eating disorders like anorexia.

Today's precarious human activities facilitate mercury further into the air, soil and water. The burning of fossil fuels lets off elemental mercury that can take on many forms in the environment.

Fish readily take up these forms of mercury and pass it into humans. Today, the average mercury level in tuna measures 250 ppb, as documented by the Natural News Forensic Food Lab.

A handy online calculator created by the National Resources Defense Council can help you monitor your mercury intake from a variety of seafood sources. The results warn if you have exceeded EPA safety limits.

For example, a 160-pound female who eats three cans of chunk light tuna per week exceeds the chart's safety zone. This is equivalent to consuming about 0.12 micrograms of mercury per kilogram of body weight per day, an amount exceeding EPA safety standards.

To better understand this element, here are the three classes of mercury including the top ways people are being poisoned by it.

Metallic mercury and fossil fuel combustion

At room temperature, metallic mercury is shiny and in liquid form. It's also called elemental mercury, because this is its purest form and is not combined with any other elements. This form is used in thermometers. Metallic mercury lets off vapors, especially as the temperature rises. If breathed in, these vapors can go unfiltered by the gastrointestinal tract and can damage the nervous system.

Humans are responsible for the release of elemental mercury into the atmosphere (80 percent) primarily through fossil fuel combustion, mining and smelting, and from solid waste incineration. Once it's released into the air, it can change into other forms and get into the soil and waterways. Additionally, metallic mercury is in dental amalgams -- a bizarre practice that the dental industry has yet to address.

Inorganic mercury and vaccine preservatives

Mercury becomes inorganic mercury when it combines with other elements. It commonly combines with oxygen, sulfur and chlorine to form mercury salts. Most of these mercury salts look like white powders or crystals. Inorganic forms of mercury, like ammoniated mercuric chloride and mercuric iodide, are used in skin-lightening creams, which is a crude and questionable method of skin care.

Other forms, such as thimerosal and phenylmercuric nitrate, are used as preservatives in some vaccines and medicines, raising serious questions of medical ethics. (Flu shots like this one contain 51,000 ppb of mercury!) Additionally, mercury injections of this form are sent straight into the blood, bypassing the gastrointestinal filters of the body.

Organic mercury and fish consumption

When mercury combines with carbon specifically, it is classified as organic mercury. Organic mercury can also combine with other elements to form organic mercury salts. The most common form found in the environment is methylmercury. This is the form of mercury passed into fish and marine mammals. Methylmercury is changed by bacteria and fungi in the environment and is multiplied and made more pervasive in this way. Through these natural changes, the level of mercury is expounded upon and passed into marine mammals and, ultimately, humans who consume the fish.

The mercury levels in the fish ultimately measure higher than concentrations in the surrounding water! Sharks and swordfish live a long time and can bioaccumulate tremendous amounts of mercury in their tissues.

To learn more about your mercury intake from seafood, do a personal checkup using the handy online calculator provided by the National Resources Defense Council.

For more information and breaking news on heavy metals like mercury, visit HeavyMetals.NaturalNews.com.

Sources for this article include:

http://www.nrdc.org

http://science.naturalnews.com

http://www.atsdr.cdc.gov

http://www.naturalnews.com

http://www.atsdr.cdc.gov [PDF]