Atmosphere

Air toxics and indoor air quality in Australia

State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4

Part C: Factsheets (continued)

Lead and compounds

Substance name: Lead (and compounds)
CASR number: 7439-92-1
Molecular formula: Pb
Synonyms: Lead metal, pigment metal The Latin word for lead is 'plumbum', which is the source for the chemical symbol for lead, Pb. There are 129 lead compounds listed in the National (United States) Library of Medicine's Hazardous Substances Data Bank. Some of the more significant compounds (based on volume used and hazard) are:
lead acetate (CASR 301-04-2)
lead chloride (CASR 7758-95-4)
lead chromate (CASR 7758-97-6)
lead fluoroborate (CASR 13814-96-5)
lead iodide (CASR 10101-63-0)
lead nitrate (CASR 10099-74-8)
lead phosphate (CASR 7446-27-7)
lead oxide (CASR 1317-36-8)
lead sulfide (CASR 1314-87-0)
tetraethyl lead (CASR 78-00-2)

Physical and chemical properties

Physical properties

Lead

Lead is a dense, soft, bluish-grey metallic solid. It has no special taste or smell, but when burned it imparts a metallic, sweetish taste. It is malleable and deflects radiation.

Melting point: 327.43°C
Boiling point: 1740°C
Specific gravity: 11.3

Lead compounds

The physical and chemical properties of lead compounds are varied and will not be listed here. Specific properties may be found in the references listed at the end of this article.

Chemical properties:

Lead

Lead will not dissolve in pure water; however, it may react with impurities in water to produce soluble lead compounds. Lead is soluble in nitric acid and slightly soluble in sulfuric acid.

Lead compounds

The physical and chemical properties of lead compounds are varied and will not be listed here.

Common uses

Metallic lead is used in the production of batteries, products used to shield X-rays and various metal products (pipes, solder, flashing, ammunition/bullets, fishing weights, electronics and alloys with other metals). A survey of lead compounds shows some of their uses are as follows. Tetraethyl lead is used to make other leaded compounds (tetra-alkyl leads) used in leaded fuels (petrol). Lead compounds are used in the manufacture of plastics, rubbers, metals, matches, ammunition, fireworks and explosives. They are also used in pigments, dyes, paints and coatings, rodenticides, insecticides, pottery glazes, brake shoes, flame retardants for plastics, lead lighting, catalysts for industrial production and epoxy curing agents.

Sources of emissions

Point sources

Lead and its compounds may be released to the land, water and air from mining activities because they occur in the earth's crust. They may also be released to the land, water and air from manufacturing industries, transport and smelting operations, and lead-containing paint. They may be released to air from the burning of fossil fuels (coal, oil, gas).

Diffuse sources, and point sources included in aggregated emissions data

Lead and its compounds may be released from contaminated soil near lead refineries and waste sites and from lead-containing paint. They may be released to air from petrol stations dispensing leaded fuel. They may be released to land and water from lead-containing rodenticides and insecticides and from lead pellets from spent ammunition.

Natural sources

There are small amounts in the earth's crust, usually present as lead sulfide, lead oxide or lead carbonate. Lead is also emitted from volcanoes and forest fires.

Mobile sources

Lead may be emitted by vehicles using leaded fuels, including lawnmowers.

Consumer products that may contain lead (and compounds)

Consumer products containing lead include batteries, ammunition, metal products (solder and pipes), roofing, old paint products, leaded petrol, artists' pigment, some ceramics, some plastics, crystal, pewter, jewellery, and lead core wick candles (see also 'Common uses').

Health effects

How might I be exposed to lead (and compounds)?

You can be exposed to lead and lead compounds from breathing air, drinking water and eating soil, dust, paint or foods that contain lead or lead compounds. Lead and lead compounds can enter the air you breathe from the burning of leaded fuels (petrol), emissions from iron and steel production, lead smelting operations, lead battery manufacturing, the burning of lead-painted surfaces, and windblown dust from areas of lead enrichment (eg areas of heavy automotive traffic or areas near the industries listed above). Lead and lead compounds can enter the water you drink, from lead plumbing in homes, schools and other buildings; lead-containing dust carried into the water by wind and rain; emissions from industries that use lead and/or lead compounds; and automobile exhaust. Lead and lead compounds may be ingested when lead-containing dust gets onto food and crops while they are growing or during processing; plants can take up lead from the soil in areas of heavy exposure (eg areas of heavy automobile traffic). Children may swallow paint chips, eat soil, or put items in their mouths that have contaminated dirt or dust on them.

By what pathways might lead (and compounds) enter my body?

Lead or lead compounds that are breathed into the lungs or swallowed enter the blood and move to other parts of the body. Lead can be absorbed by a foetus in the womb. Lead will be stored in bones and teeth. Some lead compounds can also be absorbed through skin contact. During normal use of metallic lead products, very little lead passes through the skin. The burning of tetra-alkyl lead compounds in leaded fuel (petrol) releases lead oxide, which is very water-soluble (hence readily ingested with contaminated water) and poisonous.

Health guidelines

National Occupational Health and Safety Commission (NOHSC):

Lead is listed as a substance under review for chronic intoxication by NOHSC.

Australian Drinking Water Guidelines (NHMRC and ARMCANZ 1996):

National Ambient Air Quality Standards and Goals:

What effect might lead (and compounds) have on my health?

Lead is poisonous in all forms; the poison is cumulative and the toxic effects are many and severe. Ingestion of a large amount of any soluble lead salt or organo-lead compound (eg lead nitrate, lead oxide, lead sulfate, tetraethyl lead) may cause (in increasingly higher doses) poor appetite, nausea, pain, leg cramps, muscle weakness, damage to the brain, kidneys and reproductive organs, and death. Behaviour effects can include mood changes, disturbed sleep, memory loss, and poor attention span. Lead and lead-containing compounds are especially dangerous to the health of children and the unborn child. Young children exposed to lead and lead compounds can experience a decrease in intelligence scores, learning difficulties, slow growth and defective hearing. Lead exposure during pregnancy can contribute to premature birth, low birthweight and abortion. Lead chromate is classified by the NOHSC as a category 2 carcinogen (substance that should be regarded as if it is carcinogenic to humans).

Environmental effects

Environmental fate

Lead is a naturally occurring element that does not break down in either soil or water, but lead compounds are changed by sunlight, air and water. If released to the air from industry, the burning of fossil fuels, or waste, lead may remain airborne for about 10 days, depending on weather conditions. Lead will stay in soil, dust and sediments for many years.

Environmental transport

Lead in the air can be carried long distances and will attach to dust. This lead-containing dust is removed from the air by rain, and heavy rain can wash it into rivers, drains, etc.

Environmental guidelines

Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC 1992):

What effect might lead (and compounds) have on the environment?

The immediate effects of exposure to lead can mean the death of animals, birds or fish and death or low growth rate in plants. Especially in soft water, lead is highly poisonous to plants, birds or land animals. Long-term effects on animal life are shortened lifespan, reproductive problems, lower fertility and changes in appearance or behaviour. Lead does not break down and is highly persistent in water, so the tissues of aquatic organisms will probably contain lead from polluted waters.

Key

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