360 Dust Analysis

GardenSafe: Understanding your results

What's in my soil?

After EPA scientists have assesed your garden soil, you will be emailed a report containing the screening results from your garden soil samples.

The sections below walk through how to interpret your screening results and how you can reduce harm from contaminated soil.

Garden soil quality indicators

Garden soil quality indicators provide a snapshot of the condition of your soil. These results are unlikely to impact human health but can influence how well your plants grow.

If your soil quality indicators are outside of the optimum range desired, you can change your soil composition by adding organic matter (compost, leaves etc.) or commercial products (fertiliser, lime etc.). More information is available on our soil quality indicators page.

Interpreting your trace element results

The simplest way to interpret your trace element results is to ask: “Are the concentrations in my soil above or below the guideline provided?”.

If your soil is:

Above the guideline - Further investigation and risk assessment may be required. Reasonably practicable measures to remove or reduce the presence of, or your exposure to, that contaminant should be considered to reduce risk of adverse human or environmental health effects.

Approaching the guideline - Measures to reduce the presence of, or your exposure to, that contaminant should be considered.

Below the guideline - Carry on gardening. Keep in mind that good gardening practices like thoroughly washing hands and veggies, and mulching areas of exposed soil go a long way in reducing your exposure to soil and contaminants.

Trace elements

Your report includes the trace element screening results from your garden and the Australian Health Investigation Level guideline for residential gardens with accessible soil (HIL A).

This establishes the concentration above which further health investigation and evaluation should be considered, or alternative approaches to how you grow your veggies be implemented, such as using pots or raised beds with clean soil.

For most garden soil samples, the HIL A guideline is the appropriate value to compare your results against (Table 1). Guidelines for other land use categories are provided in the National Environment Protection (Assessment of Site Contamination) Measure.

Table 1. Health Investigation Levels for trace elements in Australian soil (mg/kg)* 

As - arsenic; Cd - cadmium; Cr – chromium**; Cu - copper; Mn - manganese; Ni - nickel; Pb - lead; Zn - zinc. 

*From Table 1A(1) of the National Environment Protection (Assessment of Site Contamination) Measure; Schedule B (1), Guideline on Investigation Levels for Soil and Groundwater, 2013.

**Guideline is for hexavalent chromium (CrVI) but pXRF measures total Cr. See detail below.

Where:
HIL A = residential garden with accessible soil, including day care centres, preschools, and primary schools. Home grown produce equals less than 10% of fruit and vegetable intake, no poultry.

Chromium testing

Chromium can occur in different chemical states. This includes the metal state (Cr0) that is used for making steel, trivalent chromium (CrIII) that has low toxicity and is not easily absorbed into the body, and hexavalent chromium (CrVI) that has high toxicity and is a known carcinogen. 

Your report contains the screening results for total chromium in your sample, meaning the concentration of all chromium states combined. However, the HIL A guideline value is for hexavalent chromium (CrVI) only.

It is unlikely that your sample contains all of one type of chromium. If the total chromium concentration in your sample exceeds the guideline for CrVI, you may consider further chromium testing (speciation) through an environmental consultant to determine if a risk is present. Or, you may implement alternative approaches to how you grow your veggies, such as using pots and raised beds filled with new soil from a reputable provider.

Map My Environment

Trace element screening data collected by GardenSafe is displayed on the interactive platform: Map My Environment. The online tool combines work from other citizen science projects to improve environmental data accessibility and empower community to make informed decisions about their local environment.

You can use this online tool to explore our data and compare your screening results to other locations in the area.

To protect your privacy, technical controls, including a double jitter, are applied to the data, preventing personal information being used to spatially identify individuals or sample locations. View EPA's privacy policy for more information.

Jump to Map My Environment's global map, change the sample type to ‘soil’, and zoom to your suburb to get started.

Victoria Unearthed 

Victoria Unearthed is an online mapping tool that captures information on land and groundwater contamination. Sites that have received an EPA clean-up notice or pollution abatement notice, sites with restricted groundwater use, and locations of current and historic landfills are captured on the map.

Data collected from GardenSafe will not be shared with Victoria Unearthed, however you can use this tool to learn more about pollution sources in your area. For more guidance from EPA Victoria, visit Contaminated land and your health.

Reducing harm from contaminated soil

Identifying contamination is important because it can cause harm to human and environmental health.

There are three components to contamination that may cause harm:

  • The source of contamination (e.g., lead paint)

  • The pathway through which it could spread (e.g., ingestion of contaminated soil particles or uptake of contaminants into home grown veggies)

  • The receptor the contamination could impact (e.g., people consuming home grown veggies).

Guidelines to reduce harm to human health from contamination consider each of these pathways and provide a concentration above which harm to the receptor (people) may occur for a given contaminant.

Actions taken to remove or reduce risk from contaminated soil should address the source and the pathway, so that harm to the receptor is reduced.

In the example above, by safely removing the lead paint and old oil drums (source), and replacing the topsoil in and around the veggie patch (pathway), the risk to the family and their chickens (receptor) from eating home-grown veggies and working in the garden is reduced.

If your GardenSafe screening results exceed the guideline provided, then further investigation may be required. Reasonably practicable measures to remove or reduce the presence of, or exposure to, that contaminant should be considered to reduce potential risk of adverse human or environmental health effects. This may include growing veggies in pots or raised beds with new soil from a reputable provider.

Only a qualified medical professional can advise how a contaminant could impact an individual’s health. Please see your doctor if you have health concerns about soil contamination.

Reasonably practicable measures to reduce soil contamination

The actions taken to remove or reduce soil contamination should be proportional to the level of contamination identified, if any.

Examples of remediation strategies include:

  • Excavate the contaminated soil - For higher contaminant concentrations, consider removing the top 30 cm of soil and for disposal at an appropriately licenced landfill. Place an impervious fabric to stop the mixing of old and new soil. Add a thick layer of clean, purchased soil from a reputable provider on the top. 

  • Grow veggies in a raised bed - Construct a raised bed using safe materials. Fill the bed with layers of organic matter, compost, cardboard, and clean purchased soil from a reputable provider. Do not use treated timber, old painted timber, or tyres to build your raised garden bed.

  • Mulching and covering - Cover the contaminated soil with a layer of clean soil then mulch or pave the area. This reduces the generation of contaminated dust and restricts contact between people and the soil. Only grow ornamental plants in these areas, rather than edible produce.

  • Build a designated play space for children - Like the raised bed, build a garden bed using safe materials and fill with clean, purchased soil from a reputable provider. Use this as a play and learning space for children to get their hands dirty and try growing their own veggies. Remember to wash your hands after playing in the soil.

Removing or reducing soil contamination may require a combination of strategies. Seek advice from an experienced environmental professional and consider further testing before commencing remediation. Always dispose of waste, including contaminated soil, at an appropriately licenced landfill.

Keep in mind that good gardening practices like thoroughly your washing hands and veggies, and leaving dirty shoes at the door, go a long way in reducing your exposure to soil and contaminants. Even when working with clean soil, these practices should be followed. 

View Sustainability Victoria’s do’s and dont's list for more suggestions. 

Limitations and further testing

GardenSafe provides screening level data for common contaminants in garden soil. While we endeavour to provide reliable results using innovative techniques, soil testing from a NATA accredited facility will return higher data accuracy.

There may be other contaminants in your garden soil that are not assessed by this program, including asbestos and pesticides. An environmental consultant can conduct a site investigation to assess other contaminants in your soil and advise suitable remediation strategies. If high contaminant concentrations are identified in your soil by GardenSafe then further testing is recommended.

Macquarie University
Northumbria University
Olympus
Environmental Protection Authority (Victoria)
ABOUT US

The 360 Dust Analysis program is a global research initiative to collect and analyse data on contaminants of concern that may be harmful to human health in homes and gardens.

CONTACT US

dustsafe@mq.edu.au

gardensafe@epa.vic.gov.au

ee.dustsafe@northumbria.ac.uk

LOCATIONS

Environment Protection Authority, VIC, Australia.

Macquarie University, NSW, Australia.

Northumbria University, Newcastle, United Kingdom.

IUPUI, Indianapolis, United States.

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