Toxic Metals

Heavy metals

A metal that has a high atomic weight with a specific gravity that exceeds the specific gravity of water by 5 or more times. Examples are arsenic, lead, and mercury.

"Itai-itai byo"

A condition caused by cadmium exposure that began occurring in Japan. It was called "itai-itai byo" by locals because "itai" is the Japanese term for when people are inflicted with pain and "byo" is the literal term for disease.

Minamata disease

A neurologic condition associated with ingestion of mercury; characterized by numbness of the extremities, deafness, poor vision, and drowsiness.

Trace metals

Metals (e.g., copper, zinc, manganese, and iron) necessary for human nutrition in trace amounts, but can be toxic if ingested in excessive amounts; also known as essential metals.

Compare the three categories of metals shown in Table 6.1. Give an example of a metal from each category.

Major Toxic Metal with Multiple Effects: Beryllium (Be); not necessary to sustain life.
Essential Metals with Potential for Toxicity: Iron (Fe); necessary for life in trace amounts but are toxic in excess.
Metals Related to Medical Therapy: Platinum (Pt); can be used to treat medical conditions in small doses; like lithium therapy can help depression.

Why is lead contamination a concern for environmental health experts?

Lead is a cumulative toxin that affects multiple body systems and is particularly harmful to young children. Lead in the body is distributed to the brain, liver, kidney and bones. It is stored in the teeth and bones, where it accumulates over time. Lead in bone is released into blood during pregnancy and becomes a source of exposure to the developing fetus. There is no level of exposure to lead that is known to be without harmful effects.

Name some of the portals of entry into the human body for toxic metals. Describe the methods by which these toxic metals may access specific portals of entry.

Lungs (through inhalation of dusts, metal fumes, and vapors)
Skin (through contact with dusts)
Mouth (by ingestion)

Give some examples of environmental sources of exposure of populations to heavy metals.

Contact with high concentrations of toxic metals is most likely to occur in occupational settings. Low-level exposure may result from contact with the ambient environment (children ingesting lead from paint on old playgrounds, for example). There are four major types of media that have potential for exposure.
Air: occupational exposure
Soil/Dust: Mining and toddler ingestion
Water: Natural presence, methylation, rust and piping
Biota/Food: biomagnification in fish, pesticides, glazes and glass in wheat processing

Exposure to heavy metals presents a serious hazard to children.
a. Give an example of a heavy metal to which children commonly are exposed in our environment.
b. List the symptoms of exposure to this heavy metal among children.
c. List the long-term effects of this heavy metal on children.

a. Lead
b. Nervous system damage presenting as memory impairment, difficulty learning, behavioral issues such as hyperactivity syndrome and overt aggressiveness
c. High level exposure in children can lead to comas, convulsions or even death. Children who survive severe lead poisoning may be left with mental retardation and behavioral disorders. At lower levels of exposure that cause no obvious symptoms lead is now known to produce a spectrum of injury across multiple body systems. In particular lead can affect children's brain development resulting in reduced intelligence quotient (IQ), behavioral changes such as reduced attention span and increased antisocial behavior, and reduced educational attainment. Lead exposure also causes anaemia, hypertension, renal impairment, immunotoxicity and toxicity to the reproductive organs. The neurological and behavioral effects of lead are believed to be irreversible.

State two incidents of mass poisonings of humans that involved arsenic.

Arsenic-contaminated beer killed 6,000 people in England in the year 1900.
Several thousand people were poisoned in Japan in the mid-20th century due to arsenic-contaminated dry milk and soy sauce.

Provide the following information regarding cadmium:
a. Possible sources of exposure
b. Modes of entry into the body
c. Two major health effects
d. Name of an associated disease

a. Cigarette smoke, dietary cadmium, surface waters, and occupation; can bioaccumulate in shellfish and some mushrooms; can be in vegetables grown in Cd-contaminated soil
b. Dietary - ingestion of contaminated shellfish, mushrooms and/or vegetables; Occupational - inhalation and the absorption through gastrointestinal tract
c. "itai-itai byo" - caused by chronic Cd poisoning due to presence in the Jinzu River from discharge of Kamioka Mining Company, located upstream; inflicted persons would yell "itai itai!" as they tried to move with excruciating pain; most severe cases suffered broken bones if they tried to move on their own.

Provide the following information regarding chromium:
a. Where it occurs in the environment
b. Its effects on human health
c. Who is Erin Brockovich?

a. Found naturally occurring in the earth's crust (rocks, soils and volcanic material) and occurs in many forms. The most common forms are Cr(0), Cr(III), and Cr(VI). Cr(III) is an essential nutrient for sugar, protein and fat use in the body. Cr(0) and Cr(VI) are a result of human industry and are environmental pollutants.
b. Is classified as a human carcinogen (lungs cancer, occupational); Can leach into drinking water and cause digestive problems and damage to organs like the kidneys and liver; Can cause skin ulcers and respiratory problems if inhaled (nose bleeds, perforation of nasal septum, runny nose)
c. Erin Brockovich was the employee at a Hinkley-area law firm that uncovered PG&E's Cr(VI) dumping. She launched a personal investigation into their activities and helped the plaintiffs win a $333 million settlement.

What are some of the medical uses of mercury?

Mercury has been used to treat syphilis, as an agricultural fungicide and in dental amalgams for filling cavities.

Provide the following information regarding lead:
a. Sources of exposure in the environment
b. Adverse health effects of exposure to lead

a. Sources of environmental Pb include leaded gasoline, tap water from soldered pipes, and painted surfaces in older buildings.
b. Pb exposure is associated with serious central nervous system effects and other adverse health consequences, even when ingested at low levels. Acutely elevated blood Pb levels (70 ug/dL) are associated with severe neurologic effects, including comas, convulsions and death.

Provide the following information regarding nickel:
a. Two uses of nickel
b. Two adverse effects of exposure to nickel

a. Can be machined and polished readily and resists corrosion from non-oxidizing acids and alkalis; Employed in the production of many common, everyday appliances and tools like nickel cadmium batteries.
b. Nickel allergy (presents as contact dermatitis); Fibrosis of the lungs

Name the metals that are essential for human nutrition.

Copper, zinc, and iron

How can you reduce your exposure to copper in tap water?

By running the water for around half a minute in the morning before use can reduce the concentration of copper in the tap water.

Describe the importance of iron to human health. Describe the side effects of ingesting excessive amounts of iron.

Vital to human health, iron is important to the growth of cells and the transport of oxygen within the circulatory system. About 66% of the iron in the body is used in hemoglobin. Iron has the capacity to accumulate in the body because little is excreted during metabolic processes. Excessive amounts of iron can have toxic effects, such as vomiting, diarrhea, and damage to intestines. Iron toxicity can also produce low blood pressure, lethargy, neurologic effects like seizures and liver injury. Hemachromatosis is the disease associated with iron toxicity from excessive build up.

List at least three sources of exposure to aluminum. Describe the hypothesized associated of aluminum and Alzheimer's disease.

Aluminum is widely used in food and beverage containers, in pots and pans, and in construction sites. Aluminum is an ingredient in various medicines and cosmetics. Aluminum has been studied as a factor that may be linked to Alzheimer's disease. Al is known to be a powerful neurotoxicant. The role of Al as a factor in the pathogenesis of Alzheimer's disease remains unconfirmed. One study reported an association between Al concentration in drinking water and Alzheimer's disease. The author suggested that the amount of residual Al in public drinking water should be limited. The ATSDR states, "Some studies show that people exposed to high levels of Al may develop Alzheimer's disease but other studies have not found this to be true. We do not know for certain that Al causes Alzheimer's disease. Some people with kidney disease store a lot of Al in their bodies... Sometimes these people develop bone or brain diseases that doctors think were caused by the excess Al."