What Should I Do If My Land Is Asbestos-Contaminated?
The last blog post showed some common ways that asbestos contaminates soil. If you suspect your land may be asbestos-contaminated, what should you do about it?
Is There a Risk to Health From Asbestos in Soil?
The first step in a risk assessment is hazard identification. Is there actually asbestos in the soil? At K2 Environmental, we have qualified asbestos assessors and surveyors who can help with identifying potential contamination.
It is possible asbestos is present, but at such a low level the risk to health is low. If asbestos fibres become airborne, this is where the risk occurs.
To identify where contamination is present, soil samples can be taken. Initially, a presence/absence test can be done. This analysis can be done relatively quickly. Soil samples are ashed to remove organic matter then analysed.
If this test identifies areas of contamination, the next step is to determine the risk to health.
Determining the Risk to Health From Asbestos in Soil
If asbestos has been identified being present in the soil, the next step is “how much is there”? Presence/absence testing is quick and K2 asbestos lab technicians can provide some indication of the amount of asbestos present.
To estimate exposure to people, the asbestos concentration in the soil should be tested. This analysis takes longer as the soil needs to be dried first and any asbestos found must be weighed.
Asbestos soil concentration analysis will give you a percentage of asbestos in the soil. Concentrations are given for three distinct forms of asbestos which guidelines apply to.
- ACM. Asbestos-containing material. These are any materials that contain asbestos in a bonded matrix (e.g., cement sheet debris). Bonded material is often referred to as non-friable material. It does not easily give rise to airborne asbestos fibres. The size is greater than 10mm.
- FA. Fibrous asbestos. This material is likely to give rise to asbestos fibres. It is often referred to as friable (e.g., insulation). Material that has become severely degraded, or ACM smaller than 10mm.
- AF. Asbestos fines. This refers to loose asbestos fibres. These are expected to be a greater risk to health as they more easily become airborne.
From the percent concentrations (weight for weight), you can estimate the risk the contamination poses to people. The weight per weight value is the weight of asbestos compared to the total dry weight of the sample.
What Can Soil Concentration Tell Us?
For asbestos to be a hazard, the asbestos fibres must become airborne. Asbestos is not a health risk if its just sitting in the dirt.
Field tests and simulated tests using worst-case conditions have been conducted to estimate how much asbestos fibre will become airborne for various concentrations in soil. Soil types affect the risk. Dry sandy soil is more likely to release fibres than wet clay soil. These tests found that:
- Soil containing less than 1% of bonded, non-friable ACM produces little to no airborne fibres. That is material like cement board in a reasonably stable, bonded condition.
- For friable asbestos, higher soil concentrations generate higher airborne fibre concentrations. With soil concentrations of 1% asbestos, airborne asbestos was measured at 0.05 f/mL (fibres per millilitre). This would be a risk to health.
Soil Guideline Values
Soil guideline values have been provided that give a conservative level where asbestos contamination is considered to be acceptable. These values are dependent on the land use and the type of asbestos.
Form of Asbestos | Soil Guideline Values | |||
---|---|---|---|---|
Residential | High-Density Residential | Recreational | Commercial and Industrial | |
ACM (bonded, non-friable) | 0.01% | 0.04% | 0.02% | 0.05% |
FA and/or AF (friable asbestos or asbestos fines) | 0.001% |
Other Factors
Asbestos concentration in soil is not the only factor that should be considered when making a risk assessment. You should also take into account:
- Who is going to be exposed? Is the contamination in an area likely to be disturbed regularly?
- How dry is the soil? Adding just 5% moisture reduces airborne asbestos by 80-95%.
- What type of soil is it? Loose, sandy soils will pose a higher risk than dense clay.
- What type of ground cover is there? Is there any grass or vegetation?
- How exposed is the soil? Will it be subject to high wind conditions?
Regulations and Guidelines
- For workplaces there are a number of intersecting laws that regulate what action is required. For DIY homeowners, the Ministry of Health has provided guidance on how to manage asbestos contamination. This can be found at https://www.health.govt.nz/publication/management-asbestos-non-occupational-environment.
- If you are concerned about asbestos in your soil, a risk assessment should be made first. This will identify what the risks are, who will be affected, and to what extent.
Case Study: My House
I have a small section of fencing at my house that has been patched up with corrugated asbestos sheets. The sheets are Super Six and are quite damaged. I expected the soil around the sheeting to be asbestos contaminated, so I thought I’d take a sample and test.
I wasn’t too worried about the health risk from this soil generally as it is away from the house and not in an area that is walked on. I was a bit concerned about health risks when the area needed weeding though.
I took a composite sample from the top layer of soil alongside the asbestos sheeting.
Some small bundles of chrysotile asbestos were identified in the soil, but this was not above the laboratory detection limit of 0.001% weight for weight. The asbestos detected was about 1/7th of the quite conservative guideline values. The sample was taken on quite a dry day and the soil appeared dry, but the moisture in the soil was still at 13%.
This gives me reassurance that the asbestos will not pose a great risk to health. I’ll still be sure to be cautious when working around that area though.
How Can We Help?
If you are concerned about asbestos contamination in your land, call K2 Environmental today or send us an enquiry.
We can help with asbestos analysis, asbestos sampling and risk assessments through a preliminary site investigation (PSI).