Asbestos advice for householders

Ministry of Health responses to questions about asbestos in Canterbury.

News article

29 July 2014


The workplace health and safety regulator, WorkSafe NZ, has been investigating the testing and management of asbestos during repair work carried out in homes in Canterbury following the earthquakes in 2010 and 2011.

Below are answers to some common questions about potential health risks for homeowners.

Questions and answers

Q1  What is asbestos and what are the different types?

Asbestos is a common term describing a variety of naturally occurring silicate minerals. It was a popular building material up until the 1990s because of its exceptional insulating, fire-resistant and reinforcing properties.

Left undisturbed, asbestos is safe – but if it is exposed or damaged, it can be harmful.

The most commonly mined forms of asbestos are chrysotile (white asbestos), crocidolite (blue asbestos) and amosite (brown asbestos).

Chrysotile asbestos is the type usually present in asbestos-containing materials in New Zealand houses.

Chrysotile fibres tend to break across the fibre, so become shorter and remain thicker than the crocidolite and amosite fibres.

The fibres of health significance are those that can be inhaled. Longer, thinner fibres are a greater risk to health as they are less easily removed by the body’s defences.

Q2  What is the health risk from exposure to asbestos?

Health risks from asbestos depend on a number of factors:

  • the amount of asbestos fibres in the air
  • how long your exposure lasts
  • how often you were exposed
  • the size of the asbestos fibres (they must be small enough to be breathed in)
  • the amount of time since your first exposure
  • the type of asbestos fibre.

People are more likely to experience asbestos-related diseases when they are exposed to higher concentrations of asbestos, are exposed frequently and over long periods of time.

The risk of developing asbestos-related diseases is very low for low-level short-term exposure in the home. This is because the risk of disease is directly related to the amount of asbestos and length of exposure. Short-term low-level exposure in the home is likely to pose negligible risk of disease.

Asbestos-related diseases generally occur in workers who have had heavy exposure over extended periods of time, such as people engaged in the manufacture of asbestos-containing material.

Q3  What happens when I am exposed to asbestos?

The main exposure to asbestos is from breathing in airborne asbestos fibres, some of which may get trapped in your lungs. Most fibres are removed from your lungs by the body’s defences. Levels of fibres in lung tissue build up over time, but some fibres, particularly chrysotile (white asbestos), can be removed with time.

If you swallow asbestos, nearly all of the fibres are excreted in the faeces. There is some evidence that ongoing exposure may increase the risk of gastrointestinal tumours and that short-term high levels of ingestion may lead to precursor lesions of bowel cancer. However these effects may be caused by something other than asbestos.

Asbestos fibres can penetrate into the skin but do not appear to pass through the skin into the blood.

Q4  Are children more susceptible to asbestos than adults?    

There is no conclusive evidence that children are at greater risk of developing asbestos-related disease than adults.

Q5 What do I do if I have asbestos in my home?

The risk of developing asbestos-related diseases is extremely low for low-level short-term exposure in the home. This is because the risk of disease is directly related to the amount of asbestos and length of exposure. Short-term low-level exposure in the home is likely to pose negligible risk of disease.

 Asbestos poses a risk if it is no longer adequately contained in the material it came in (such as due to damage, being cut or drilled into during building work, home maintenance or wear and tear). For this reason, the Ministry of Health advises homeowners not to undertake home maintenance on materials that may contain asbestos, or dispose of such materials themselves.

If you are worried about asbestos in your home talk to a health protection officer about what to do. You can find one at your local public health unit. 

You can arrange to have your house tested for the presence of asbestos fibres. For a list of accredited laboratories, search on the keyword “asbestos” on the IANZ website.

Asbestos-related diseases generally occur in workers who have had heavy exposure over extended periods of time, such as people engaged in the manufacture of asbestos-containing material.

The highest risk of exposure to asbestos in the home is through home renovating, by cutting or drilling through asbestos-cement sheeting or sanding down asbestos-backed linoleum or tiles. Left undisturbed, these materials pose a negligible risk as long as they are in good condition and it is recommended that asbestos-containing material in good condition be left alone.

There is an ongoing, although low, risk of exposure to asbestos fibres in a home where there are damaged or deteriorating asbestos-containing insulation, walls, ceiling or floor tiles. The longer you are exposed to asbestos fibres in the air, and the higher the concentration of the exposure, the greater the risk of developing asbestos-related diseases later on in life.

Q6  How long is it before any health effect from asbestos exposure would occur?

Asbestos-related diseases take many years, usually decades, to develop. Symptoms developing within months of exposure are unlikely to be related to asbestos.

Q7 What factors affect the risk of developing an asbestos-related disease?

Generally, asbestos-related diseases occur in workers, such as miners and factory workers, often from historical and heavy exposures (before modern laws and controls were introduced). Those asbestos workers who smoke are about 90 times more likely to develop lung cancer than people who neither smoke nor have been exposed to asbestos. The general population is exposed to small amounts of asbestos fibres in air arising from natural sources and wearing down of manufactured asbestos-containing materials.

Friable asbestos (which would crumble easily if handled) is more likely to generate airborne fibre, hence increasing the risk of exposure to asbestos. The risk of generating airborne asbestos fibres can be reduced by appropriate management measures (eg removing the friable material or sealing the surface).

Q8  How much asbestos is safe, if any?

The risk of disease depends on how much exposure occurred and over what time period. No specific dose can be determined because everyone will have different susceptibility, and different risk factors. For example, people who are frequently exposed to asbestos, and who smoke, are at a much greater risk of lung cancer.

Most people who develop asbestos-related disease have had occupational exposure to asbestos. Examples are people who often routinely encountered asbestos in their daily work, such as electricians and plumbers. People who have developed asbestos-related disease (usually mesothelioma) but who do not appear to have been exposed at work, nearly all seem to have either been regularly exposed to asbestos brought home on the work clothing of someone else or to have undertaken maintenance or renovation on asbestos-containing materials.

In developed countries like New Zealand, most concerns about asbestos are for people who were heavily exposed to asbestos in their workplaces, prior to the 1980s.

Exposure to all forms of asbestos at sufficiently high concentrations of airborne fibres over long periods increases the risk of asbestos-related diseases. The risk from exposure to asbestos in the non-occupational setting is generally considered to be low because the concentrations of airborne asbestos fibres are low and people are not exposed very often, compared with asbestos workers who may be exposed to significant amounts of asbestos on a daily basis (which is why asbestos workers now use personal protective clothing and follow rigorous workplace practices).

Q9  What are the health effects of asbestos?

The health effects of exposure to fibres from asbestos-containing materials can take many years (in some cases up to 50 years) to develop. Diseases and or conditions that are caused by exposure to asbestos fibres include:

  • Asbestosis
  • Pleural plaques
  • Lung cancer
  • Mesothelioma.

Asbestosis: Asbestosis is scarring in the lungs from breathing in asbestos fibres. It occurs in people who have been exposed to high concentrations of asbestos over a long time. The risk of asbestosis is insignificant for those who have not worked with asbestos.

Symptoms do not usually appear until about 20 to 30 years after the first exposure to asbestos. The person develops shortness of breath and dull chest pains, and sometimes scarring and fibrosis (thickening). The extent of lung damage is related to the amount of asbestos retained in the lungs, the fibre type and length, and individual susceptibility. Cigarette smoking increases the risk.

Asbestosis can be diagnosed by a chest x-ray or lung function test.

Non-malignant pleural conditions: Pleural plaques occur when there are large amounts of asbestos fibres in the lungs. They do not usually cause symptoms. Plaques tend to develop more than 20 years after exposure, and are related to length of exposure and possibly to peaks of exposure.

Lung cancer: There is an association between asbestos exposure and lung cancer, and those with higher exposures are more likely to get lung cancer than those with lower exposures. The symptoms do not usually appear until 10 to 20 years after the first exposures to asbestos.

Mesothelioma: Mesothelioma is a rare cancer that develops in the layer around the lungs (pleura) or intestine (peritoneum). It is the classic tumour associated with asbestos exposure, and is unrelated to smoking. It develops 35 to 40 years or more after the time of first exposure, although shorter periods have been recorded. Most cases are in workers or people in regular contact with contaminated clothing of asbestos workers.

About 5% of mesothelioma cases (87 out of 1,631 cases) in Western Australia from 1960 to 1988 were attributed to home renovation/maintenance or exposure as a bystander during these activities. Australia has the highest reported rate of mesothelioma in the world. Among developed countries Australia had the highest per capita use of asbestos cement products. Crocidolite (blue asbestos) was mined in Australia and used in asbestos cement products. The risk from crocidolite (blue asbestos) is higher than from chrysotile (white asbestos), the type usually present in asbestos-containing materials in New Zealand houses.

Q10  What are the symptoms of asbestos-related disease?

Asbestos-related diseases affect the lungs, so symptoms include shortness of breath, tiredness, pain on breathing, and persistent cough. These symptoms are general and may indicate other health conditions. These symptoms appear many years (usually decades) after sufficient exposure to asbestos occurred.

Q11  Can I be tested for exposure, and if so, how?

There is no test that can measure asbestos in the body.

Exposure can only be estimated by:

  • personal air sampling (a monitor worn in the breathing zone)
  • air and environmental sampling
  • questionnaires, interviews, inspections, historical records.

For all measures of exposure there are limitations, and expert advice is generally needed.

Q12 Isn’t it possible to have a chest x-ray to see if I have asbestos in my lungs?

A chest x-ray is recommended for detecting exposure to asbestos only in persons who have had prolonged and high exposure. A chest x-ray is of no value for detecting evidence of asbestos exposure in a person whose exposure to asbestos has been brief. The x-ray cannot detect the asbestos fibres, but it can detect early signs of lung disease caused by asbestos. This does not occur until many years after the first exposure occurred.

Q13  Should any specific health monitoring be considered for people exposed to asbestos?


Q14  What should I do if I, or a member of my home is sick?

If you or someone in your home is sick, you should contact your local GP, Healthline on 0800 611 116, or call 111 if it’s an emergency. Sickness will not be asbestos-related because diseases caused by asbestos take many years (usually decades) to develop.

Q15  Is there new evidence around asbestos and cancer?

There is no new evidence, but there are ongoing studies into differences in the risk of lung cancer and mesothelioma (a rare form of cancer) from different types of asbestos. The results of research are being published every now and then, and add to the body of information about the health effects from asbestos exposure.

We have known for many years that the risk of lung cancer following exposure to any form of asbestos is much higher among smokers. If you are a smoker, quitting smoking considerably reduces your risk of developing lung cancer, especially if you have been exposed to asbestos. However, exposure to asbestos carries a risk of lung cancer on its own, even in non-smokers.

Historically, studies into asbestos have looked at mesothelioma more than lung cancer because almost all mesothelioma is caused by asbestos, while most lung cancer is not caused by asbestos. So there continues to be some uncertainty about how great the risk of lung cancer from asbestos is.

Most studies on asbestos are about workers, as workers have much greater exposures than anyone else. However, the same safety measures that apply to workers also apply to people exposed to asbestos at home, regardless of the type of asbestos. Information on how to apply those protective measures is available on the WorkSafe website.

For more information

WorkSafe: asbestos information and guidance

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

Further information available on the Ministry of Health website:

Asbestos - Your health guide

A more technical guideline on the Management of Asbestos in the Non-Occupational Environment.

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