Lead

What is lead?

Lead (or Pb in the periodic table) is a naturally occurring heavy metal that is found in the Earth’s crust. Lead can be released into soil, air and water through soil erosion, volcanic eruptions, sea spray and bushfires. The natural concentration of lead in the air is less than 0.1 microgram per cubic metre.

Humans have used lead in various applications for thousands of years, with some of the past uses having left behind serious environmental and human health problems.

Mining and metal manufacturing are the largest sources of lead emissions in Australia. However, there are many other sources, including: waste incinerators; battery recycling; the production of lead fishing sinkers; cement, plaster and concrete manufacturing; ceramic products such as garden pots; iron and steel; petroleum and coal products; paper, glass and metal products; motor vehicles and their parts; wood products; and yarn and fabric for making clothes and curtains.

Lead has had many uses in modern society:

• in cars – most cars require a lead battery
• in older televisions and personal computers (i.e. not plasma or LED) – leaded glass in the cathode ray tube (CRT) and screen protects the user from potentially harmful radiation.
• Other everyday applications include cable sheathing, bearings, low-melting alloys such as solders, and as protective shields against x-rays.

Australia is a major producer and exporter of lead. The Australian lead industry, along with other sectors such as the petroleum and motor trade industries, are supporting strategies to reduce lead exposure.

Leaded petrol used to be a source of high levels of lead in the air of major cities. Significant reductions in the levels of air-borne lead were achieved over recent years as the result of national legislation introduced to remove lead from petrol.

How does lead affect human health?

Lead is a health hazard. It is stored in your bones and teeth, and may damage parts of your body, including your liver, kidneys and brain.

Exposure to lead can affect the health of children, unborn babies and adults.

Once in the body, lead circulates in the blood. The amount of lead in a person's blood gives an indication of how much lead has recently been breathed in or swallowed. These measurements are called blood lead levels. The results of a blood lead level test will usually be put in terms of how many micrograms of lead there are in each decilitre of blood (i.e. micrograms per decilitre).

The national recommendation for all Australians is to have a blood lead level below 10µg/dL (micrograms per decilitre) as determined by the National Health and Medical Research Council (NHMRC).

A single exposure, like eating a leaded-paint flake the size of a five cent piece, can increase blood-lead levels for several weeks. Some of this lead will remain in the body for life.

A small exposure to lead however, does not always result in symptoms of lead poisoning in either adults or children. However, lead can gradually build up in the body to cause health problems if exposure continues.

Pregnant women (unborn babies)

Exposure to lead can be harmful to the unborn baby because lead in the mother’s blood passes through the placenta. Complications from high levels of exposure include premature birth, low birth weight, or even miscarriage or stillbirth.

Breastfeeding mothers can also pass lead on to their infants via their breastmilk.

The effects of lead exposure continue after birth and can result in impaired learning and mental ability.

Children

Lead exposure can permanently damage the brain and impair intellectual development. Children under five years of age are particularly vulnerable to lead exposure because:

• They frequently put their hands and toys to their mouths.
• They absorb and retain more lead from the gut and airways than adults do.
• Their developing brains are more sensitive to the effects of lead.

Note: Children with pica—a behaviour that leads them to eat non-food substances such as old peeling paint flakes, soil or stones—are also at an increased risk of lead exposure.

Children's nervous systems are undergoing rapid change and are particularly susceptible to permanent damage. A child breathes and consumes more food and air in relation to their size than an adult does. Because of this, the amount of lead that a child breathes in or swallows is proportionally greater than for an adult.

In addition to that, up to 60% of lead swallowed by children moves directly into circulating blood and thus from organ to organ. Adults retain only around 10%. Lead also stays in red blood cells much longer in children than in adults.

There is growing evidence of intellectual impairment in young children with blood lead levels previously thought to be safe. Studies in Australia and overseas show a decrease in IQ in children aged 0-4 years with sustained blood lead levels greater than 10 micrograms per decilitre.

Symptoms of acute lead poisoning

The symptoms of acute lead poisoning (a high level at one time) include:

• Muscle pains
• Fatigue
• Abdominal pains
• Headache
• Nausea and vomiting
• Seizures
• Coma.

Symptoms of chronic lead poisoning

Chronic (long-term or ongoing) exposure to lower levels of lead may produce symptoms such as:

• Irritability and shortened attention span
• Lack of energy
• Loss of appetite
• Learning disabilities
• Behavioural problems
• Poor coordination
• Impaired growth
• Anaemia
• Increased blood pressure
• Heart rate variability
• Fertility issues.

Be sure to be safe

Please note that many of these symptoms could be caused by other conditions, so it is important to see a doctor if you are worried.

Some children or adults may not have any symptoms at all.

Ask your doctor for a blood test if you think you or your family have been exposed to lead.

• Lead paint and human health - video on the physiological effects of lead paint

How much of a problem is air-borne lead in Australia?

The amount of lead in Australia's air has decreased significantly since the introduction of unleaded petrol in 1986. Before the phase-out of leaded petrol, which began in 1993, the national air quality standard for lead was regularly exceeded in urban environments. Levels are now less than 10 per cent of the national annual standard of 0.5 micrograms per cubic metre of air.

Lead levels remain high in some regional towns with large industrial point sources (such as lead smelters), and levels may exceed the national standards in these areas.

Find out more

Lead exposure can occur in a variety of different ways.

• Lead in auto paints
• Lead in house paint
• Lead in marine paints
• Lead in ceramic crockery and pottery making
• Lead in recreational activities
• Lead in stained glass