Is Your Land Asbestos-Contaminated?
Asbestos is a very common building material in New Zealand homes, particularly those built between 1940 and 1990. Homes built earlier may have asbestos-containing materials (ACMs) in renovations or extensions. Homes built later may still have asbestos contamination on the property from previous demolitions.
How does soil become contaminated?
Soil may become contaminated in the following ways:
- Dumping of asbestos or using asbestos waste for landfill
- Degradation of ACMs over time
- Fire damage to ACMs
- Poor quality asbestos removals or work done on ACMs (for example, water-blasting an asbestos roof)
Dumping of ACMs
From the 1930s to the 1970s, ACM waste products were used as imported fill for use in farm tracks or swamp infilling. Uncontrolled dumping (fly-tipping) of ACMs can also contaminate the soil.
In houses that have ACM cladding, soffits or roofing, you will often find off-cuts and scraps of ACM discarded under the house.
Degradation of ACMs
A common source of asbestos contamination in soil is from asbestos roofing materials. In New Zealand, the two most common asbestos roof materials are Super Six (corrugated asbestos cement sheeting) and Decramastic (bitumen/aggregate coated metal tiles). Super Six is more common in industrial roofing and may also be used for cladding and fencing. Decramastic roofing is more common in residential buildings. Other asbestos roof materials include Galbestos (asbestos-lined metal roofing) and asbestos cement tiles.
Super Six roofing is very likely to result in widespread contamination of the surrounding area and water courses. With Decramastic roofing, asbestos fibres will likely be present wherever you can see roofing debris (gutters and run-off areas).
Another common source of contamination is from asbestos cement pipes. These are sometimes used as downpipes in residential homes.
Cement sheeting used in cladding or soffits is less likely to cause soil contamination as these materials tend to remain bound together. They are also less likely to be subject to erosion from rain and water run-off.
Contamination from Fire Damage
During a house fire, asbestos cement soffits will often explode. This will leave bits of asbestos cement all over the surface of the ground. Smaller bits of asbestos may be carried up by the plume of the smoke and can contaminate land blocks away from the house fire.
If removed quickly, the contamination will usually only affect the top layer of soil and can be effectively removed.
Poorly-Controlled Asbestos Removals or Maintenance
Asbestos removals were not always as regulated as they are now. Soil may have become contaminated through poorly-controlled asbestos removals or demolitions.
Poorly-controlled maintenance can also contaminate land. For example, water-blasting asbestos roofs can spread asbestos bundles all over a property.
Is Asbestos-Contaminated Soil a Health Hazard?
There’s no doubt that asbestos is a serious hazard. It is known to cause cancers, including lung cancer and mesothelioma, and can cause scarring of the lungs (asbestosis) in high doses.
However, in most cases, the risk to health from asbestos-contaminated soil is relatively low. The risk is through the soil’s potential to release airborne asbestos fibres.
Several studies have been conducted for the potential of asbestos-contaminated soil to release airborne fibres. These studies suggest that significant visible quantities of bound ACMs would need to be present to result in high risk. If loose asbestos is present in the soil (e.g. where ACMs have degraded), the risk is higher.
The type of soil (sandy, silty or clay), the acidity, and the moisture content also have a significant effect on the risk of contaminated soil. For example, adding just 5% moisture to soil reduces airborne asbestos by 80-95%.
What Should I Do About Asbestos-Contaminated Soil?
If you suspect your soil may be contaminated, give us a call today to discuss or send a message to info@k2.co.nz.
We can provide advice on ways to manage or remediate the soil. We are also able to conduct preliminary site investigations (PSIs) and can test for the presence and concentration of asbestos in soil at our Christchurch laboratory.
In the next blog post, I’ll be looking at how we test for asbestos in soil!