Health effects of exposure to heavy metals

Published by the University of Michigan

By Maile Pouls Ph.D.

The Heavy Metal Hazard

Some metals are naturally found in the body and are essential to human health. Iron for example prevents anemia and zinc is a cofactor in over 100 enzyme reactions. They normally occur at low concentrations and are known as trace metals. In high doses they may be toxic to the body or produce deficiencies in other trace metals; for example high levels of zinc can result in a deficiency of copper another metal required by the body.

Heavy or toxic metals are trace metals with a density at least five times that of water. As such they are stable elements (meaning they cannot be metabolized by the body) and bio-accumulative (passed up the food chain to humans). These include: mercury, nickel, lead, arsenic, cadmium, aluminum, platinum, and copper (the metallic form versus the ionic form required by the body). Heavy metals have no function in the body and can be highly toxic.

Once liberated into the environment through the air, drinking water, food, or countless human-made chemicals and products, heavy metals are taken into the body (via inhalation ingestion and skin absorption). If heavy metals enter and accumulate in body tissues faster than the body's detoxification pathways can dispose of them a gradual buildup of these toxins will occur. High-concentration exposure is not necessary to produce a state of toxicity in the body as heavy metals accumulate in body tissues and over time can reach toxic concentration levels.

Heavy metal exposure is not an entirely modern phenomenon. Historians have cited the contamination of wine and grape drinks by lead-lined jugs and cooking pots as a contributing factor in the "decline and fall" of the Roman Empire, and the Mad Hatter character in Alice in Wonderland was likely modeled after nineteenth-century hat makers who used mercury to stiffen hat material and frequently became psychotic from mercury toxicity.

Human exposure to heavy metals has risen dramatically in the last 50 years as a result of an exponential increase in the use of heavy metals in industrial processes and products. Today, chronic exposure comes from mercury-amalgam dental fillings, lead in paint and tap water, chemical residues in processed foods, and "personal care" products (cosmetics shampoo and other hair products mouthwash toothpaste soap). In today's industrial society there is no escaping exposure to toxic chemicals and metals.

In addition to the hazards at home and outdoors, many occupations involve daily heavy metal exposure. Over 50 professions entail exposure to mercury alone. These include physicians, pharmaceutical workers, any dental occupation, laboratory workers, hairdressers, painters, printers, welders, metalworkers, cosmetic workers, battery makers, engravers, photographers, visual artists, and potters.

The Effects of Heavy Metal Toxicity

Studies confirm that heavy metals can directly influence behavior by impairing mental and neurological function, influencing neurotransmitter production and utilization, and altering numerous metabolic body processes. Systems in which toxic metal elements can induce impairment and dysfunction include; the blood and cardiovascular, detoxification pathways (colon liver kidneys skin), endocrine (hormonal), energy production pathways, enzymatic, gastrointestinal, immune, nervous (central and peripheral), reproductive and urinary.

Breathing heavy metal particles, even at levels well below those considered nontoxic, can have serious health effects. Virtually all aspects of animal and human immune system function are compromised by the inhalation of heavy metal particulates. In addition toxic metals can increase allergic reactions, cause genetic mutation, compete with "good" trace metals for biochemical bond sites, and act as antibiotics killing both harmful and beneficial bacteria.

Much of the damage produced by toxic metals stems from the proliferation of oxidative free radicals they cause. A free radical is an energetically unbalanced molecule composed of an unpaired electron that "steals" an electron from another molecule to restore its balance. Free radicals result naturally when cell molecules react with oxygen (oxidation) but with a heavy toxic load or existing antioxidant deficiencies uncontrolled free-radical production occurs. Unchecked free radicals can cause tissue damage throughout the body. Free-radical damage underlies all degenerative diseases. Antioxidants such as vitamins A C and E curtail free-radical activity.

Heavy metals can also increase the acidity of the blood. The body draws calcium from the bones to help restore the proper blood pH. Further, toxic metals set up conditions that lead to inflammation in arteries and tissues causing more calcium to be drawn to the area as a buffer. The calcium coats the inflamed areas in the blood vessels like a bandage patching up one problem but creating another, namely the hardening of the artery walls and progressive blockage of the arteries. Without replenishment of calcium the constant removal of this important mineral from the bones will result in osteoporosis (loss of bone density leading to brittle bones).

Current studies indicate that even minute levels of toxic elements have negative health consequences, however, these vary from person to person. Nutritional status, metabolic rate, the integrity of detoxification pathways (ability to detoxify toxic substances), and the mode and degree of heavy metal exposure all affect how an individual responds. Children and the elderly whose immune systems are either underdeveloped or age-compromised are more vulnerable to toxicity.

Common Heavy Metals: Sources and Specific Effects

Aluminum, arsenic, cadmium, lead, mercury, and nickel are the most prevalent heavy metals. The specific sources of exposure body tissues in which the metal tends to be deposited and health effects of each metal are identified below.

Aluminum

Sources of exposure: Aluminum cookware, aluminum foil, antacids, antiperspirants, baking powder (aluminum containing), buffered aspirin, canned acidic foods, food additives, lipstick, medications and drugs (anti-diarrheal agents, hemorrhoid medications, vaginal douches), processed cheese, "softened" water, and tap water.

Target tissues: Bones, brain, kidneys, and stomach.

Signs and Symptoms: Colic, dementia, esophagitis, gastroenteritis, kidney damage, liver dysfunction, loss of appetite, loss of balance, muscle pain, psychosis, shortness of breath and weakness.

Among the patients I see in my practice the highest aluminum exposure is most frequently due to the chronic consumption of aluminum-containing antacid products. Research shows that aluminum builds up in the body over time; thus the health hazard to older people is greater.

D.R. McLaughlin M.D. F.R.C.P. (C) professor of physiology and medicine and director of the Centre for Research in Neurodegenerative Diseases at the University of Toronto states "Concentrations of aluminum that are toxic to many biochemical processes are found in at least ten human neurological conditions."

Ten recent studies suggest that aluminum contributes to neurological disorders such as Alzheimer's disease, Parkinson's disease, senile and presenile dementia, clumsiness of movements, staggering when walking, and inability to pronounce words properly. Behavioral difficulties among schoolchildren have also been correlated with elevated levels of aluminum.

Arsenic

Sources of exposure: Air pollution, antibiotics given to commercial livestock, certain marine plants, chemical processing, coal-fired power plants, defoliants, drinking water, drying agents for cotton, fish, herbicides, insecticides, meats (from commercially raised poultry and cattle), metal ore, smelting, pesticides, seafood (fish mussels oysters), specialty glass, and wood preservatives.

Target tissues: Most organs of the body, especially the gastrointestinal system, lungs, and skin.

Signs and Symptoms: Abdominal pain, burning of the mouth and throat, cancer (especially lung and skin), coma, diarrhea, nausea, neuritis, peripheral vascular problems, skin lesions and vascular collapse.

The greatest dangers from chronic arsenic exposure are lung and skin cancers, and gradual poisoning most frequently from living near metal smelting plants or arsenic factories.

Cadmium

Sources of exposure: Air pollution, art supplies, bone meal, cigarette smoke, food (coffee fruits, grains, and vegetables grown in cadmium-laden soil), meats (kidneys, liver, poultry), refined foods, freshwater fish, fungicides, highway dusts, incinerators, mining, nickel-cadmium batteries, oxide dusts, paints, phosphate fertilizers, power plants, seafood (crab flounder mussels oysters scallops), sewage sludge, "softened" water, smelting plants, tobacco and tobacco smoke, and welding fumes.

Target tissues: Appetite and pain centers (in brain), brain, heart and blood vessels, kidneys and lungs.

Signs and Symptoms: Anemia, dry and scaly skin, emphysema, fatigue, hair loss, heart disease, depressed immune system response, hypertension, joint pain, kidney stones or damage, liver dysfunction or damage, loss of appetite, loss of sense of smell, lung cancer, pain in the back and legs, and yellow teeth.

Current studies are attempting to determine if cadmium-induced bone and kidney damage can be prevented (or made less likely) by adequate calcium, protein (amino acids) vitamin D and zinc in the diet.

Lead

Sources of exposure: Air pollution, ammunition (shot and bullets), bathtubs (cast iron, porcelain, steel), batteries, canned foods, ceramics, chemical fertilizers, cosmetics, dolomite dust, foods grown around industrial areas, gasoline, hair dyes and rinses, leaded glass, newsprint and colored advertisements, paints, pesticides, pewter, pottery, rubber toys, soft coal, soil, solder, tap water, tobacco smoke and vinyl 'mini-blinds'.

Target tissues: Bones, brain, heart, kidneys, liver, nervous system and pancreas.

Signs and Symptoms: Abdominal pain, anemia, anorexia, anxiety, bone pain, brain damage, confusion, constipation, convulsions, dizziness, drowsiness, fatigue, headaches, hypertension, inability to concentrate, indigestion, irritability, loss of appetite, loss of muscle coordination, memory difficulties, miscarriage, muscle pain, pallor, tremors, vomiting and weakness.

The toxicity of lead is widely acknowledged. The greatest risk for harm even with only minute or short-term exposure is to infants, young children, and pregnant women. A federal study conducted by the Centers for Disease Control and Prevention (CDCP) in 1984 estimated that three to four million American children have an unacceptably high level of lead in their blood. Dr. Suzanne Binder a CDCP official stated "Many people believed that when lead paint was banned from housing [in 1978] and lead was cut from gasoline [in the late 1970s] lead-poisoning problems disappeared but they're wrong. We know that throughout the country children of all races and ethnicities and income levels are being affected by lead [already in the environment]."

In their book “Toxic Metal Syndrome” Dr.'s R. Casdorph and M. Walker report that over 4 million tons of lead is mined each year and existing environmental lead levels are at least 500 times greater than pre-historic levels.

In 1989 the U.S. Environmental Protection Agency (EPA) reported that more than one million elementary schools, high schools and colleges are still using lead-lined water storage tanks or lead-containing components in their drinking fountains. The EPA estimates that drinking water accounts for approximately 20% of young children's lead exposure. Other common sources are lead paint residue in older buildings (as in inner cities) and living in proximity to industrial areas or other sources of toxic chemical exposure such as commercial agricultural land. All children born in the U.S. today have measurable traces of pesticides, a source of heavy metals and chlorine-based chemicals in their tissues.

Lead is a known neurotoxin (kills brain cells) and excessive blood lead levels in children have been linked to learning disabilities, attention deficit disorder (ADD) hyperactivity syndromes, and reduced intelligence and school achievement scores.

Mercury

Sources of exposure: Air pollution, batteries, cosmetics, dental amalgams, diuretics, (mercurial) electrical devices and relays, explosives, foods (grains), fungicides, fluorescent lights, freshwater fish (especially large bass pike and trout), insecticides, mining, paints, pesticides, petroleum products, saltwater fish (especially large halibut shrimp snapper and swordfish), shellfish, and tap water.

Target tissues: Appetite and pain centers in the brain, cell membranes, kidneys and nervous system (central and peripheral).

Signs and Symptoms: Abnormal nervous and physical development (fetal and childhood), anemia, anorexia, anxiety, blood changes, blindness, blue line on gums, colitis, depression, dermatitis, difficulty chewing and swallowing, dizziness, drowsiness, emotional instability, fatigue, fever, hallucinations, headache, hearing loss, hypertension, inflamed gums, insomnia, kidney damage or failure, loss of appetite and sense of smell, loss of muscle coordination, memory loss, metallic taste in mouth, nerve damage, numbness, psychosis, salivation, stomatitis, tremors, vision impairment, vomiting, weakness and weight loss.

The primary source of exposure to mercury is "silver" dental fillings (approximately 50% mercury when placed); over 225 million Americans have these fillings in their teeth. Mercury fillings release microscopic particles and vapors of mercury every time a person chews. Vapors are inhaled, while particles are absorbed by tooth roots, mucous membranes of the mouth and gums, and the stomach lining.

In people with mercury amalgam fillings, measurements of the mercury level in the mouth ranges between 20 and 400 mcg/m3. Keep in mind that this is continuous exposure. The National Institute of Occupation Safety and Health places the safe limit of environmental exposure to mercury at 20 mcg/m3 but that is assuming a weekly exposure of 40 hours (the work week) and the mercury involved is outside the body. The Environmental Protection Agency's allowable limit for continuous mercury exposure is 1 mcg/m3 but again that is based on mercury sources outside the body. Neither figure addresses 24-hour-a-day exposure from mercury in one's mouth.

Hal Huggins D.D.S. a specialist in the effect of mercury amalgams on health, reports that 90% of the 7000 patients he tested showed immune system reactivity from exposure to low levels of mercury. In 1984 the American Dental Association (ADA), without providing scientific evidence, claimed that only 5% of the U.S. population is reactive to mercury exposure and that this figure is insignificant. Meanwhile the ADA mandates that dentists alert all dental personnel to the potential hazards of inhaling mercury vapors. The Environmental Protection Agency (EPA) goes further, instructing dentists to treat mercury amalgam as a toxic material while handling before insertion, and as toxic waste after removal.

Mark S. Hulet D.D.S. who conducts research on amalgam fillings wrote a pamphlet for his patients in which he cites five categories of pathological reaction to mercury fillings as identified by dentists, doctors and toxicologists. The categories are:

Neurological: emotional manifestations (depression, suicidal impulses, irritability, inability to cope) and motor symptoms (muscle spasms, tremors, facial tics, seizures, multiple sclerosis)
Cardiovascular problems: nonspecific chest pain, accelerated heart beat
Collagen diseases: arthritis, bursitis, scleroderma, systemic lupus erythematosis
Immune system diseases: compromised immunity
Allergies: Airborne allergies, food allergies, and "universal" reactors.

One of the keys to mercury's effects on health may be its ability to block the functioning of manganese a key mineral required for physiological reactions in all five categories notes Dr. Hulet.

Nickel

Sources of exposure: Appliances, buttons, ceramics, cocoa, cold-wave hair permanent, cooking utensils, cosmetics, coins, dental materials, food (chocolate, hydrogenated oils, nuts, food grown near industrial areas), hair spray, industrial waste, jewelry, medical implants, metal refineries, metal tools, nickel-cadmium batteries, orthodontic appliances, shampoo, solid-waste incinerators, stainless steel kitchen utensils, tap water, tobacco and tobacco smoke, water faucets and pipes, and zippers.

Target tissues: Areas of skin exposure, larynx (voice box), lungs and nasal passages.

Signs and Symptoms: Apathy, blue-colored lips, cancer (especially lung, nasal and larynx), contact dermatitis, diarrhea, fever, headaches, dizziness, gingivitis, insomnia, nausea, rapid heart rate, skin rashes (redness, itching, blisters), shortness of breath, stomatitis and vomiting.

Casdorph H. M.D. and Walker M. D.P.M. Toxic Metal Syndrome (Garden City Park NY) Avery Publishing 1995) 95. Kellas B. Ph.D. and Dworkin A. N.D. Surviving the Vomiting.

The greatest danger from chronic nickel exposure is lung, nasal or larynx cancers, and gradual poisoning from accidental or chronic low-level exposure, the risk of which is greatest for those living near metal smelting plants, solid waste incinerators or old nickel refineries.

How Can We Protect Ourselves from Heavy Metals?

Logic dictates that once the potential harm from heavy metals is understood, their production and use should be phased out and toxic storage heavily regulated. As is obvious from the list of exposure sources above, logic is not the guiding principle here except in the case of lead, the use of which has been curtailed.

Even if all heavy metal production were to stop today, however, enough heavy metals have been released into our environment to cause chronic poisoning and numerous neurological diseases for generations to come. There are presently 600,000 toxic waste contamination sites in the United States alone, according to the U.S. Congressional Office of Technology Assessment. Of these less than 900 have been proposed by the EPA for Superfund cleanup, and approximately 19,000 others are under review. While some of these toxic messes were likely caused by accidents or ignorance, the majority came from illegal dumping by hazardous product or waste distributors, manufacturers, transportation companies, or waste management companies. Such practices have not ceased as focus on profit continues to override concerns about health, the environment, and a more promising future for all of our children.

With the government doing little or moving very slowly to protect the public from the hazards of heavy metals it is up to individuals to take measures to protect themselves. According to conventional medicine there is nothing a person can do to address aluminum, arsenic, cadmium, lead, mercury or nickel exposure, aside from avoiding known sources. Given the prevalence of these toxins in our lives this is impossible.

Fortunately there is a way to get these harmful substances out of the body. Intravenous and oral chelation detoxification protocols and specific nutritional therapies can remove heavy metals and chemical toxins, and reduce the toxic load our bodies endure on a daily basis.

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