Lead
Environmental Sources
Lead is a naturally occurring bluish-gray metal found in small amounts
in the earth’s crust. Lead can be found in all parts of our environment.
Much of it comes from human activities including burning fossil fuels,
mining, and manufacturing.
Lead has many different uses. It is used in the production of batteries,
ammunition, metal products (solder and pipes), and devices to shield X-rays.
Because of health concerns, lead from petrol, paints and ceramic products,
and pipe solder has been dramatically reduced in recent years. Unleaded
fuel has been required in several countries for year. However, in South
Africa, leaded fuel is still used and is a leading source of environmental
exposure to lead. Exposure to lead-contaminated dust is the most common
way to get lead poisoning. Lead is highly toxic and exposure to it can
be dangerous, especially for children who are 6 or younger.
Lead itself does not break down, but lead compounds are changed by sunlight,
air, and water. When lead is released to the air, it may travel long distances
before settling to the ground. Once lead falls onto soil, it usually sticks
to soil particles. Movement of lead from soil into groundwater will depend
on the type of lead compound and the characteristics of the soil.
Human Health Effects
Lead can affect almost every organ and system in your body. The most
sensitive is the central nervous system, particularly in children. Lead
also damages kidneys and the reproductive system. The effects are the
same whether it is breathed or swallowed.
Even at very low doses lead is bad for children, as it is associated
with IQ deficiencies, reading and learning disabilities, impaired hearing,
reduced attention spans, hyperactivity, and antisocial behaviour. Almost
all symptoms of Attention Deficit Disorder (ADD) are the same as the symptoms
of lead poisoning.
It stays in our bodies, in blood, bones, and soft tissues, and can damage
kidneys, liver and the nervous system. Excessive exposure can cause seizures,
mental retardation, and behavioural problems. At high levels, lead may
decrease reaction time, cause weakness in fingers, wrists, or ankles,
and possibly affect the memory. Lead may cause anaemia, a disorder of
the blood. It can also damage the male reproductive system. The connection
between these effects and exposure to low levels of lead is uncertain.
Lead acetate and lead phosphate may reasonably be anticipated to be
carcinogens based on studies in animals. There is inadequate evidence
to clearly determine lead’s carcinogenicity in people.
Exposure limits
- The US Centres for Disease Control and Prevention (CDC) recommends
that children ages 1 and 2 be screened for lead poisoning. Children who
are 3 to 6 years old should be tested for lead if they have never been
tested for lead before and if they receive services from public assistance
programs; if they live in or regularly visit a building built before 1950;
if they live in or visit a home built before 1978 that is being remodelled;
or if they have a brother, sister, or playmate who has had lead poisoning.
CDC considers children to have an elevated level of lead if the amount
in the blood is 10µg/dL.
- The US EPA requires lead in air not to exceed 1.5 micrograms per cubic
meter (1.5 µg/m3) averaged over 3 months. EPA limits lead in
drinking water to 15 µg per litre.
- The US Occupational Health and Safety Administration (OSHA) develop
regulations for workers exposed to lead. The US Clean Air Act Amendments
of 1990 banned the sale of leaded gasoline. The US Federal Hazardous Substance
Act bans children's products that contain hazardous amounts of lead.
- The South African Department of Environmental Affairs and Tourism’s
(DEA&T) guideline values stipulate a maximum monthly average lead
concentration of 2.5 micrograms per cubic meter (ug/m3) and a maximum annual average of 0.5 ug/m3.
- WHO has an annual limit of 0.5 ug/m3
- The Lead Regulations of 1991, under section 35 of the Machinery and
Occupational Safety Act of 1983, states that males who work in an area
where exposure to lead is identifiable shall not have a Blood Lead Concentration
greater than 80 ug/100ml and may only return to work when this level is
brought down to less than 70 ug/100 ml. His Urinary Lead Concentration
should not exceed 150 ug/l and he should only return to work when this
level is less than 130 ug/l. Females working in such an environment shall
not continue working if her Blood Lead Concentration is greater than 40
ug/100 ml or if becomes pregnant, and may only return to work when this
level is brought down to less than 35 ug/100 ml. She shall not work if
her Urinary Lead Concentration exceeds 75 ug/l or when she becomes pregnant
and should only return to work when this level is less than 65 ug/l.
- The Lead Regulations (1991) also state that immediate measurements
of urinary lead concentration are required for employees exposed to tetra-alkyl
Lead and where it is found that the blood Lead concentration of any employee
is equal or greater than 80 ug/100ml or where the urinary concentration
is equal to or greater than 150 ug/l, the employer shall investigate the
incident.
Sources & Links:
www.atsdr.cdc.gov/tfacts13.html
www.turnertoys.com/pvc9printable.htm
www.epa.gov/children/air.htm
www.epa.gov/oar/aqtrnd97/brochure/pb.html
www.aeclp.org
www.cdc.gov/nceh/programs/lead/
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