Lead

Lead is a chemical element in the carbon group with symbol Pb and atomic number 82. Lead is a soft and malleable metal, which is regarded as a heavy metal. Metallic lead has a bluish-white colour after being freshly cut, but it soon tarnishes to a dull greyish colour when exposed to air. Lead has a shiny chrome-silver lustre when it is melted into a liquid. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1] Lead is found in the earth’s crust. However, it is rarely found naturally as a metal. It is usually found combined with two or more other elements to form lead compounds. Metallic lead is resistant to corrosion (i.e., not easily attacked by air or water). When exposed to air or water, thin films of lead compounds are formed that protect the metal from further attack. Lead is easily moulded and shaped. Lead can be combined with other metals to form alloys. [2]

 

Uses [2]

 

Lead and lead alloys are commonly found in pipes, storage batteries, weights, shot and ammunition, cable covers, and sheets used to shield us from radiation. The largest use for lead is in storage batteries in cars and other vehicles. Lead compounds are used as a pigment in paints, dyes, and ceramic glazes and in caulk. The amount of lead used in these products has been reduced in recent years to minimise lead’s harmful effect on people and animals. Tetraethyl lead and tetramethyl lead were once used in the United States as gasoline additives to increase octane rating. However, their use was phased out in the United States in the 1980s, and lead was banned for use in gasoline for motor vehicles beginning January 1, 1996. Tetraethyl lead may still be used in gasoline for off-road vehicles and airplanes. It is also still used in a number of developing countries. Lead used in ammunition, which is the largest non-battery end-use, has remained fairly constant in recent years. However, even the use of lead in bullets and shot as well as in fishing sinkers is being reduced because of its harm to the environment.

 

Sources of Emission & Exposure

 

Sources of Emission [3]

 

  • Industry sources: Mining and metal manufacturing are the largest sources of lead emissions in Australia. Water supply, sewerage and draining surfaces, oil and gas extraction and electricity supply can also emit lead. Lead is also emitted as a result of coal mining, cement, lime, plaster and concrete product manufacture, ceramic product manufacturing, transport equipment manufacturing, iron and steel manufacturing, petroleum and coal product manufacturing. Other manufacturing industries where lead may be used include: beverages and malt, paper and paper products, glass and glass products, fabricated and structural metal products, motor vehicles and parts, wood products, ceramic products, food and beverage products, textile, yarn and woven fabrics.
  • Diffuse sources: Paved roads, windblown dust, burning fuels or wildfires, solid and liquid fuel combustion, lawn mowing and barbeques (from burning fuel) are all capable of causing emissions of lead.
  • Natural sources: Lead and compounds occurs naturally in the earth’s crust in rocks and soil.
  • Transport sources: Lead emissions may be present from the vehicle exhaust of cars, aeroplanes, railway operations and from recreational and commercial shipping or boating.
  • Consumer products: Lead and compounds are used in a range of applications. Lead is used in the production of batteries, ammunition, metal products (solder and pipes) and devices to shield X-rays. Lead was present in petroleum, paints and ceramic products, caulking and pipe solder, however due to health concerns, it is now prohibited to include lead in these products.

 

Sources of Exposure [4]

 

  • Eating food or drinking water that contains lead;
  • Water pipes in some older homes may contain lead solder;
  • Lead can leach out into the water;
  • Spending time in areas where lead-based paints have been used and are deteriorating;
  • Deteriorating lead paint can contribute to lead dust;
  • Working in a job where lead is used or engaging in certain hobbies in which lead is used, such as making stained glass;
  • Using health-care products or folk remedies that contain lead

 

Routes of Exposure [5]

 

  • Ingestion: Lead exposure in the general population occurs primarily through ingestion.
  • Inhalation may be the major contributor for workers in lead-related occupations. Almost all inhaled lead is absorbed into the body, whereas from 20% to 70% of ingested lead is absorbed. Since leaded gasoline additives were phased out beginning in the 1970s, and control measures were implemented in industries, which have reduced air emissions, inhalation is no longer the major exposure pathway for the general population.
  • Dermal: Dermal exposure plays a role for exposure to organic lead among workers, but is not considered a significant pathway for the general population. Organic lead may be absorbed directly through the skin. Dermal exposure is most likely among people who work with lead.
  • Endogenous Exposure: Endogenous exposure to lead may contribute significantly to an individual’s current blood lead level, and of particular risk to the developing foetus. Once absorbed into the body, lead may be stored for long periods in mineralising tissue (i.e., teeth and bones). The stored lead may be released again into the bloodstream, especially in times of calcium stress (e.g., pregnancy, lactation, osteoporosis), or calcium deficiency.

 

Health Effects [6]

 

Noncancer Effects

 

  • Studies of humans as well as laboratory animal studies have reported effects on the blood, kidneys, and nervous, immune, and cardiovascular systems.
  • Ingestion of large amounts of lead can produce gastrointestinal symptoms, including colic, constipation, abdominal pain, anorexia and vomiting.
  • Severe brain and kidney damage can occur in children after exposures resulting in blood lead levels between 70 and 100 µg/dL and in adults at blood lead levels between 100 and 120 µg/dL
  • Anaemia has been reported after exposure resulting in blood lead levels of 40 to 70 µg/dL in children and blood lead levels of 50 to 80 µg/dL in adults.
  • Other effects from chronic lead exposure in humans include effects on blood pressure and kidney function, immune system effects and interference with vitamin D metabolism.
  • Lead also affects the nervous system in occupational-exposed adults. Neurological symptoms have been reported in workers with blood lead levels of 40 to 60 µg/dL, and slowed nerve conduction in peripheral nerves in adults occurs at blood lead levels of 30 to 40 µg/dL.
  • Children are particularly vulnerable to the neurotoxic effects of lead. Exposure to low levels of lead early in life have been linked to effects on IQ, learning, memory, and behaviour.
  • Exposure to lead during pregnancy has been associated with toxic effects on the human foetus, including increased risk of preterm delivery, low birthweight, and impaired mental development, including decreased IQ scores. These effects on mental development have been noted at maternal blood lead levels of 10 to 15 µg/dL and somewhat lower.
  • Studies on male lead workers have reported severe depression of sperm count and decreased function of the prostate and/or seminal vesicles and suggests an impact on male fertility at blood lead levels of above 40-45 µg/dL.
  • Human studies are inconclusive regarding the association between lead exposure and other birth defects, while animal studies have shown a relationship between high lead exposure and birth defects.

 

Cancer Risk

 

  • Human studies are inconclusive regarding lead exposure and an increased cancer risk. Animal studies have reported kidney tumours in rats and mice exposed to lead via the oral route.
  • EPA has considered lead to be a probable human carcinogen, and, under more recent assessment guidelines, it would likely be classified as likely to be carcinogenic to humans.

 

Safety [7]

 

First Aid Measures

 

  • Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Get medical attention if irritation occurs.
  • Skin Contact: Wash with soap and water. Cover the irritated skin with an emollient. Get medical attention if irritation develops.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
  • Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.

 

Exposure Controls & Personal Protection

 

Engineering Controls

 

Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

 

Personal Protective Equipment

 

The following personal protective equipment is recommended when handling lead:

  • Safety glasses;
  • Lab coat;
  • Dust respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves

 

Personal Protection in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Dust respirator;
  • Boots;
  • Gloves;
  • A self-contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

 

Regulation [3,8]

 

United States

 

Exposure Limit Limit Values HE Codes Health Factors and Target Organs
OSHA Permissible Exposure Limit (PEL) – General Industry
See 29 CFR 1910.1025

Note: OSHA considers “lead” to mean elemental lead, all inorganic lead compounds, and a class of organic lead compounds called lead soaps. This standard does not apply to other organic lead compounds.

Note: Large nonferrous foundries (20+ employees) are required to achieve the PEL of 0.05 mg/m3 by means of engineering and work practice controls. Small nonferrous foundries (<20 employees) are required to achieve an 8-hour TWA of 0.075 mg/m3 by such controls.

0.05 mg/m3
TWA

0.03 mg/m3
Action Level

 

HE3 Nephrotoxicity
HE5 Reproductive hazards
HE7 Cumulative neurologic effects
HE12 Cumulative blood effects
OSHA PEL – Construction Industry
See 29 CFR 1926.62
0.05 mg/m3
TWA

0.03 mg/m3
Action Level

HE3 Constipation, nausea, pallor
HE5 Reproductive risks
HE7 Nervous irritability, hyperactivity, anxiety, insomnia, headache, weakness, numbness, dizziness
OSHA PEL – Shipyard Employment
See29 CFR 1915.1025
0.05 mg/m3
TWA

0.03 mg/m3
Action Level

HE3 Nephropathy, loss of kidney function, increased blood pressure
HE5 Reduced sperm count and male sterility
HE7 Subclinical and clinical peripheral neuropathy (muscle weakness, pain, and paralysis of extremities)
HE12 Disruption of hemesynthesis, anaemia
National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL)
See Appendix C

Note: NIOSH considers “lead” to mean metallic lead, lead oxides, and lead salts (including organic salts such as lead soaps but excluding lead arsenate).

0.05 mg/m3
TWA

Air concentrations should be maintained so that worker blood lead remains less than 0.06 mg Pb/100 g of whole blood

HE5 Reproductive toxicity, nephrotoxicity, cardiovascular toxicity, gastrointestinal toxicity
HE7 Neurotoxicity
HE12 Hematologic toxicity
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) (2001) 0.05 mg/m3
TWA

A3; BEI

HE3 Cardiovascular toxicity, hypertension, cerebrovascular disease, nephrotoxicity
HE5 Reproductive toxicity
HE7 Neurologic and neurobehavioral toxicity
HE12 Blood dyscrasias
CAL/OSHA PELs
(See also Section 5198)
0.05 mg/m3 Lead (metallic and inorganic compounds), dust and fume, (as Pb) HE3 Cardiovascular toxicity, hypertension, cerebrovascular disease, nephrotoxicity
HE5 Reproductive toxicity
HE7 Neurologic and neurobehavioral toxicity

 

Australia

Safe Work Australia: Currently, the eight-hour time weighted average (TWA) exposure limits are 0.15 milligrams tetramethyl lead per cubic metre of air, 0.1 milligram tetraethyl lead per cubic metre of air, 0.15 milligrams lead arsenate per cubic metre of air, 0.15 milligrams of lead (inorganic dusts and fumes) per cubic metre of air and 0.05 milligrams of lead chromate per cubic metre of air. Consult your state or territory occupational health and safety agency for current sources of information.

 

Australian drinking water guidelines:

In 2004, the National Health and Medical Research Council (NHMRC) and the National Resource Management Ministerial Council (NRMMC) established the following guideline for acceptable water quality: Based on health considerations, the concentration should not exceed 0.01 milligrams of lead per litre of drinking water.

 

References

  1. http://en.wikipedia.org/wiki/Lead
  2. http://www.atsdr.cdc.gov/phs/phs.asp?id=92&tid=22
  3. http://www.npi.gov.au/substances/lead/source.html
  4. http://www.atsdr.cdc.gov/tfacts13.pdf
  5. http://www.atsdr.cdc.gov/csem/csem.asp?csem=7&po=6
  6. http://www.epa.gov/ttn/atw/hlthef/lead.html
  7. http://www.sciencelab.com/msds.php?msdsId=9927204
  8. https://www.osha.gov/dts/chemicalsampling/data/CH_249110.html

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