What is asbestos?
Asbestos is a naturally occurring mineral made up of many small fibres. These fibres are very strong and are highly resistant to heat, fire, chemicals and wear.
Past uses of asbestos
In the past, the special properties of asbestos made it popular for:
- asbestos-cement sheet cladding, roofing and drainage pipes
- backing material for floor tiles and vinyl sheets
- insulation board for thermal protection (eg, around fire places)
- textured ceilings and sprayed-on wall surfaces
- lagging for insulation around pipes, heaters and hot water cylinders
- vehicle brakes and clutches
- spouting and guttering components.
Asbestos was also used in household items, such as:
- oven gloves
- ironing board pads
- simmer mats for stoves
- fire blankets.
Asbestos was mainly imported and used before the 1980s. Once the health risks of asbestos were known, its use was gradually stopped, and other materials replaced it. However, products and appliances with asbestos content may still be around, particularly in homes built before 1984.
Kinds of asbestos
The most common types of asbestos fibre you are likely to find are:
- chrysotile (white)
- amosite (brown)
- crocidolite (blue).
The colour differences are very slight and laboratory analysis is needed to identify different types of asbestos fibre.
It is now illegal to import these three types of asbestos in their raw fibrous states, as well as any manufactured items that contain asbestos.
How asbestos can harm health
Asbestos is a proven human carcinogen, and all forms of asbestos can cause cancer.
The main way people are exposed to asbestos is by breathing in air that contains asbestos fibres.
Exposure to asbestos
Asbestos causes cancer in a dose-dependent manner. The greater the exposure, and the longer the time of exposure, the greater the risk of developing an asbestos-related disease.
No ‘safe’ lower limit of exposure has been identified with certainty - all exposure is thought to add to the overall risk of disease development - but the risk from a single, low-level exposure is considered to be extremely low.
Keep exposure to asbestos as low as possible.
Intact asbestos-containing material is not a risk merely by its presence. Potential health problems occur if asbestos fibres become airborne.
Diseases related to asbestos
Inhaling significant quantities of airborne asbestos causes:
- asbestosis (scarring of lung tissue)
- mesothelioma (malignant tumours, cancers that develop around the lungs or intestine)
- pleural plaques (thickening of membranes around the lungs)
- cancer of the lung, larynx and ovary.
Symptoms of asbestos-related diseases include breathing difficulties and ‘scarring’ of the lung that can be detected by x-ray.
Harmful effects following ingestion of asbestos have not been clearly documented. However it has been shown that few fibres are able to penetrate the gastrointestinal tract. Therefore the non-gastrointestinal effects from oral exposure to asbestos are unlikely. There is no consistent evidence that ingested asbestos is hazardous to health.
Smoking can increase the risk of developing lung cancer following exposure to asbestos.
The main way people are exposed to asbestos is by breathing in air that contains asbestos fibres. Small levels of asbestos fibres occur naturally in air, including as a result of weathering breaking down asbestos-containing materials, windblown soil from hazardous waste sites or deterioration of motor vehicle clutches and brakes.
The levels of asbestos in dust and windblown soil may be higher close to degrading asbestos cement clad buildings, or former sites of such buildings, or a waste site where asbestos is disturbed or not properly covered.
Research into risks from asbestos exposure
- Asbestos Exposure in New Zealand: Review of the Scientific Evidence of Non-occupational Risks – a 2015 report from the Royal Society of New Zealand and Sir Peter Gluckman
If you think you might have asbestos in your home your local public health service can advise you on how to deal with it.
What to do if you find asbestos in your home
Find out more about managing and working with asbestos.