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This course will take you through the basics of heavy metals, their benefits, their dangers to humans and the environment, and ways to prevent exposure while at work. Take this course to also know more about the most common heavy metals on Earth and what makes them toxic.
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Heavy Metals: Benefits and Dangers
**What are Heavy Metals? ** They refer to any metallic chemical element that has a relatively high specific density above 5 g/cm3. They are found naturally in the Earth's crust. They are mainly found in carbonate, sulfate, oxide, or silicate rocks or in their metallic, elemental form.1 Weathering and erosion resulted in their leaching and mitigation into soil, rivers, and groundwater. Some heavy metals are essential nutrients for various physiological and biochemical functions in the body, but in large doses, they may cause acute or chronic complications.
What are some of the important roles of heavy metals in our environment and everyday life?
At permissible limits, heavy metals found in food play a vital role in our physiological and biological functions, such as the transport of electrons and oxygen, antioxidation, and hormone biosynthesis.
Trace elements of some heavy metals, and other metalloids which play important roles in functioning of other living organisms, such as microbioma. They help in functions, including the formation the structure of proteins and pigment, redox processes, and regulation of the osmotic pressure.
Heavy metals are also vital in the manufacturing of various products we use at home. Flat panel displays incorporate a thin film of electrically conducting indium tin oxide. Fluorescent lighting relies on mercury vapor for its operation. Home electronics are wired with copper wire for its conduction properties.
Because of their high density, heavy metals are also used in ballasts of airplanes, boats, and motor vehicles.
Learn about the most common heavy metals in our environment and their uses in the next slide.
What can happen when there is a bioaccumulation of heavy metals?
At higher concentrations, heavy metals can produce common toxic effects on plants, such as low biomass accumulation, inhibition of growth and photosynthesis, and senescence, which ultimately cause plant death.3
For humans and animals, the toxicity of heavy metals can disrupt or damage our mental and central nervous systems, change blood composition, damage lungs, kidneys, livers, and other important organs.
Because of their high degree of toxicity, the following rank among the priority heavy metals that are of public health significance: Arsenic Lead Mercury Learn about each of these top heavy metal pollutants in the next lessons.
Inorganic arsenic is less abundant and is considered to be less toxic than organic arsenic.
What are the sources of arsenic contamination?
Industrial sources such as smelting and microelectronic products
Coal-fired power plants
Microbes acting on arsenic in soils
Wind transporting weathered rock and soil containing arsenic
**Working Safely with Arsenic **
** Medical Surveillance Program ** The program actively monitors employee health over time and allows for full access to health history and can be used to determine if any changes have occurred to the employee’s health.
Consistent practice of hygiene and sanitation protocols at work Regular hand washing and showers at shift completion ensure that dust and solutions are removed from the skin surface before leaving the work area. Ensure hair is tied back while handling these compounds.
**Observing proper storage of materials ** Keep work areas and food preparation areas physically separated to prevent contamination of food and utensils/facilities with these compounds.
Work in a dedicated and functionally certified fume hood whenever possible.
Wearing of complete PPE Workers should wear protective gear, such as lab coat, apron, gloves, face shield, safety glasses, respirators, or front-or back-mounted gas masks equipped with HEPA filters and acid gas canisters. Always refer to your respective occupational safety authority's prescribed requirements on PPE.
Occupational Exposure Limits on Arsenic 5 NIOSH Recommended Exposure Limit (REL) Ca C 0.002 mg/m3 [15-minute] OSHA Permissible Exposure Limit (PEL) [1910.1018] TWA 0.010 mg/m3
Fun Fact #1: Mercury is the only metal that is a liquid at standard temperature and pressure.
Fun Fact #2: Mercury is a very rare element in the Earth's crust. It accounts for only about 0.08 parts per million (ppm).
Fun Fact #3: Mercury generally is not allowed on aircraft because it combines so readily with aluminum, a metal that is common on aircraft.
Mercury exposure to pregnant women can affect the fetus and offspring may suffer from mental retardation, cerebellar symptoms, retention of primitive reflexes, malformation and other abnormalities
Mercury can also affect a child’s early development. Children with mercury poisoning may show symptoms such as impaired motor skills, problem-solving, and issues with hand-eye coordination. 3
Working Safely with Mercury
Air monitoring to measure the amount of mercury present in the air. Air monitoring should be conducted as necessary to ensure that workers are not being exposed to hazardous levels of mercury.
Store in an area that is: cool, dry, temperature-controlled, out of direct sunlight and away from heat and ignition sources, separate from incompatible materials, l such as strong oxidizing agents, ammonia, azides, and copper.
PPE: Always wear chemical safety goggles, gloves, aprons, boots, and respirators. In some operations, it may also be necessary to wear a chemical protective, full-body encapsulating suit and self-contained breathing apparatus (SCBA). For specific recommendations on respirators based on Immediately Dangerous To Life or Health (IDLH) values, you may visit https://www.cdc.gov/niosh/npg/npgd0383.html. 4
NEVER use mercury thermometers in laboratory ovens. If the thermometer breaks, the heat will lead to dangerous concentrations of mercury in the air.
Do not wear gold or silver jewelry when working with mercury.
As always, read the material safety data sheet (MSDS) for mercury before using it.
Occupational Exposure Limits for Mercury NIOSH REL: Hg Vapor: TWA 0.05 mg/m3 [skin] Other: C 0.1 mg/m3 [skin] OSHA PEL TWA 0.1 mg/m3
**Fun Fact #1: ** In 16th and 17th century Europe, lead was used in cosmetics as a way to obtain the fresh "white-faced" look that was so popular at the time, particularly among the aristocracy.
**Fun Fact #2: ** Pencils do not — and never did — contain lead. The "lead" in pencils is actually graphite.
**Fun Fact #3: ** In Ancient Rome, lead was added to wine in order to increase the perception of the wine's sweetness, which resulted in large-scale poisonings well into the late 18th century.
Which of these statements are false?
Working Safely with Lead
Always practice a high standard of personal hygiene, such as the proper washing of hands, face, and nails before eating, drinking or smoking. You should also wash and/or shower and change if necessary before going home.
Follow your site's waste disposal rules and always clear up and dispose of lead waste at end of day.
Wear the correct PPE, such as coveralls or similar full-body work clothing, gloves, hats, and shoes or disposable shoe coverlets; face shields, vented goggles, and other appropriate protective equipment.
Make sure you have the correct training and information in order to work safely.
Report any damaged or defective ventilation plant or protective equipment to your supervisor or safety representative.
Always read the Safety Data Sheet for any material that may have lead compounds.
**Occupational Exposure Limits for Lead **2 NIOSH Recommended Exposure Limit (REL) TWA 50 µg/m3 over 8-hours OSHA Permissible Exposure Limit (PEL) No greater than 50 µg/m3 averaged over an 8-hour period. The PEL is reduced for shifts longer than 8 hours by the equation PEL = 400/hours worked
NIOSH Pocket Guide to Chemical Hazards https://www.cdc.gov/niosh/npg/default.html Occupational Health Guidelines for Chemical Hazards https://www.cdc.gov/niosh/docs/81-123/ OSHA Occupational Chemical Database https://www.osha.gov/chemicaldata/index.html