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The Big Four of Heavy Metal Poisoning

Updated on March 26, 2013

Even long before the advent of the industrial revolution, man has been exposed to toxins from the environment, while eating their foods and even in their homes and work places. Sometimes the symptoms are masked and can be difficult to identify. Other times the exposure to these toxins are so acute, there are immediate signs. Even trace amounts can be devastating to the human body. The amounts can seem insignificant. In fact, the danger can be so significant, that the USFDA enforces USP 232 and USP 233 regulations which govern the limits of exposure within the pharmaceutical industry called Permitted Daily Exposure Limits (PDE).


Understanding how these heavy metals can affect your health and and how to identify signs of any poisoning can be the difference between leading a long, healthy life and exposing your body to toxins unknowingly. The “Big Four” are considered the most toxic of all the heavy metals.

The Big Four

Atomic Symbol
PDE Limit
15 µg/ day
5 µg/ day
15 µg/ day
10 µg/ day


Arsenic generally comes in three colors - metallic black, yellow, and gray. It vaporizes when heated and forms poisonous compounds. Arsenic can exist in inorganic and organic forms with the latter being considered the most toxic.

Sources: Arsenic can be found naturally in the crust of the earth in abundance with small amounts in the air, soil and water. Mining, smelting and other industrial process has contributed roughly two-thirds

of the atmospheric arsenic present today. Other sources include sea food, deep well water, pesticides, herbicides, and automobile exhaust.

Symptoms: Symptoms may be as simple as headaches, muscle weakness, drowsiness, dizziness, constipation, or it can get as severe as abdominal pains, hair loss and nerve pain in the extremities of the hands and feet.


Cadmium is a soft, bluish-white metal with similar chemical properties to mercury and zinc. It releases toxic gasses when it is burned in a powder form. It has no known biological function among advanced organisms.

Sources: Cadmium is most often found as an impurity in zinc ores. Cadmium is currently used primarily in nickel-cadmium batteries and for electroplating where exposure is typically minimized. However, it was once used in paints, such as some of the paints Vincent Van Gogh used, and still has other industrial applications. It was used significantly as corrosion protection for iron and steel. Other sources include cigarette smoke, fertilizers, fungicides, metal pipes, shipyards, and gasoline.

Symptoms: Most people are not exposed to toxic levels of cadmium without being in highly contaminated areas, but those that are exposed often feel headaches and hypertension which also leads to heart problems. Anemia has also been associated with cadmium.


Mercury, also known as quicksilver, is a naturally occurring metal that is a silver-colored liquid in its pure form. Its forms include elemental mercury, inorganic compounds and organic compounds.

Sources: Mercury is released as a byproduct of burning coal. In fact, coal-burning is responsible for over half of the mercury emissions within the United States. Broken thermometers, chlorine production, and improper waste disposal all contribute to soil and water contamination. Mercury is known to build up to toxic levels in fish and shellfish. Other sources include batteries, paint, pesticides and fungicides.

Symptoms: Mercury poisoning has a large range of symptoms from a metallic taste within the mouth, muscle weakness and high blood pressure to irregular heartbeats, numbness, tingling in the hands and feet on the less sever end. Acute exposure can also cause tremors, speech disorders, chronic headaches and even death.


Lead has a bluish-white color shortly after being cut, but turns into a dull gray color after being exposed to air. It is soft and malleable with only one common isotope. It will burn in a powdered with toxic fumes resulting as a byproduct.

Sources: Lead poisoning is the leading environmentally induced poisoning in children and is the most common heavy metal exposure in industrial workplaces. Lead based paints and gasoline are two common products that once used lead as an ingredient. Mining ans smelting have been a huge source of soil and water contamination throughout the years. Other sources include plumbing, car batteries, insecticides and automobile exhaust.

Symptoms: Lead exposure has been associated with aching muscles and bones, headaches, high blood pressure, loss of appetite, and insomnia. Chronic exposure often leaves the gum and teeth looking a blackish-blue color. Emotional instability and confusion can also be a sign of lead poisoning.

Limiting Exposure

Regardless, of the source or the symptoms associated with heavy metal poisoning, the “Big Four” heavy metals are easily the most toxic and can lead to serious health issues if they are left untreated. The USFDA is doing its part with regulations throughout various industries, including USP 232 and USP 233. Now, its time to do yours, and minimize your exposure to these highly toxic heavy metals.


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