Lead is not required for any normal bodily function. This metal has been used extensively by many industries in the past but as our knowledge of its toxic health effects expanded, the use of lead has been regulated and reduced.
Lead is a naturally occurring heavy, bluish-grey metal with a relatively low melting point (327°C). It is found naturally in the earth’s crust with an average concentration of 10 parts per million (ppm). The concentration of lead in soil is higher in mineralised areas. It rarely occurs naturally as a metal, and is most commonly associated with other elements to form lead compounds. Galena is a typical compound, mined in Broken Hill and Mount Isa.
Metallic lead is corrosion-resistant, easily shaped and mixed with other metals to form alloys. Lead is commonly used in:
paint (domestic paint pre-1970, although lead concentrations up to 0.5% could be found in paint up to 1991)
shot and ammunition
shielding to protect from radiation (x-rays)
It has also previously been used in water pipes and food storage cans. The most widespread use of lead today is in vehicle batteries.
Lead in the environment
Prior to being phased out in 2000, leaded petrol was the most prominent source of environ-mental lead. Today, the main sources of lead are from mining, smelting and refining. Lead particles can be removed from the air by rain and by physical fallout into the surrounding environment. Once lead falls onto soil or water, it sticks strongly to soil and sediment particles, where it can remain for many years. The movement of lead into groundwater is highly unlikely unless rainfall is acidic.
Who can be exposed to lead
Living near smelters, mines or transport routes
People living near smelters, mines or transport routes can be exposed to lead by:
breathing contaminated air
swallowing dust, soil or drinking rainwater contaminated with lead.
Living in older houses or using older painted furniture or toys
People living in older houses or using older painted furniture or toys may be exposed to lead by:
drinking water from old lead piping
swallowing lead paint chips directly or fragmented in dust and soil.
People may be exposed to lead when they work in jobs such as radiator repair or car battery manufacture and recycling.
ceramic cookware where lead can be released from poorly fired clay or glazing during cooking or storage of alcoholic, acidic or hot food.
Babies and small children
Babies and small children can breathe and swallow lead while they play on the ground or floor.
How lead enters the body
Lead can enter your body by breathing air containing very small particles or by swallowing lead-bearing dust, soil or paint chips. Only very small amounts of lead on your skin can pass into your bloodstream, but if it is not washed off, it can be accidentally swallowed.
Once particles are swallowed or breathed in, the amount of lead that actually gets into your blood will depend on how old you are, when you last ate and how well the lead particles dissolve in the stomach or lung.
Lead absorbed by the mother can also pass through the placenta to the baby. If exposure is ongoing, greater amounts of lead will accumulate in the body, especially in bone.
How lead leaves the body
Shortly after lead is absorbed into your body it travels in your blood to soft tissues and organs, such as liver, kidneys, brain, muscles and heart. The lead can be either stored or excreted into your urine and faeces. The time it takes for most of the lead to be excreted depends on how long you have been exposed for.
If the lead is not excreted by the kidney or gut within a few weeks the remaining lead moves to your bones and teeth. Some lead can be stored for up to 30 years in bone. This can move back into the blood during pregnancy, breast feeding, after breaking a bone, and due to osteoporosis.
The effects of lead are the same whether it enters the body by breathing or swallowing. The central nervous system is the main target for lead toxicity in both adults and children.
In adults, long-term exposure to low levels of lead may be associated with:
weakness in fingers, wrists and ankles
small increases in blood pressure
anaemia (low iron in the blood)
damaged nerve and renal function.
At very high levels, lead can severely damage brain and kidney function and ultimately cause death. Those with diabetes have a higher risk of adverse effects associated with the kidney.
In pregnant women, high levels of exposure may cause decreased birth weight or miscarriage and in men it can damage the organs responsible for sperm production.
There is no conclusive evidence at this time that lead is carcinogenic (cancer causing).
How it affects children
Children can be exposed during pregnancy and tend to spend much of their awake time in areas that can easily be contaminated such as floors and soil.
If adults and children swallow the same amount of lead, about five times more is absorbed into the body by children.
Children are more susceptible to the effects of lead than adults because:
their brains, which are the main targets, are still growing and developing
they swallow, absorb and retain more lead in their body.
Long-term exposure to low levels of lead may be associated with:
reduced IQ in young children
It can cause hearing difficulties and affect the nervous system outside the brain. These effects are most likely not reversible. Exposure to lead very early in life can re-program genes which may make it harder for these children to weather stresses later in life.
At high blood lead levels effects may include:
lack of appetite
brain damage with seizures.
In some cases lead levels may need to be lowered by treating with drugs that can bind to lead to help the body eliminate it.
No safe level of lead exposure
Humans do not need lead for their bodies to work.
The National Health and Medical Research Council (NHMRC) advised that:
lead can be harmful to people of all ages, but the risk of health effects is highest for unborn babies, infants and children
blood lead levels greater than 10 micrograms per decilitre can have harmful effects on many organs and bodily functions
if a person has a blood lead level greater than 5 micrograms per decilitre, the source of exposure should be investigated and reduced, particularly if the person is a child or pregnant woman.
Reducing your exposure
There are simple precautions you can take to reduce or prevent your exposure to lead. See the following pages for useful tips:
If you think you have been exposed to lead, or may have lead poisoning contact your local doctor.
Your doctor may recommend to have a blood test as it is the best indicator of lead exposure. This test will determine if further steps are necessary.
Preventing take-home lead from your workplace or hobby
Working in a lead-related industry or hobby can also put your family at risk of lead exposure. Lead-contaminated dust from your workplace or hobby space can attach to your clothes, shoes, hair, skin, work gear and other personal items and readily transfer into your vehicle and onto surfaces in your home. This transfer is known as take-home lead. It is important that you take precautions to protect yourself and your family from the dangers of take-home lead (PDF 197KB).
Preventing lead exposure at shooting ranges
Using firearms, casting bullets or visiting shooting ranges can put you and your family at risk of lead exposure. Lead is vaporised when guns are fired and fumes are released into the air. Lead dust is also generated when ammunition makes impact with a solid object. People can breathe in or swallow lead fumes and lead dust at shooting ranges directly from the air or from touching contaminated surfaces or when handling ammunition and cleaning and reloading firearms. Lead dust can stick to your hands, hair, skin, clothing and shoes and readily transfer into your vehicle and onto surfaces in your home. It is important that you take precautions to protect
yourself and your family from the dangers of lead exposure at shooting ranges. Avoid taking young children to shooting ranges and if you are pregnant.
For further information on lead, including ways to reduce your exposure, contact SA Health's Scientific Services on (08) 8226 7100.
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