Gardening in Urban Soils
Across Australia, wherever development has occurred, landscapes and natural
environments have been altered. Some of the products historically used to build and paint
houses and even the fuel once used in cars have found their way into soils and are now
known to pose risks to people and the environment. This page provides gardeners with
information about common contaminants that can be found in urban soil, particularly
properties that were:
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developed before 1980 (when lead paint was phased out)
located adjacent to heavily trafficked roads prior to 2002 (when lead in petrol was
phased out)
developed on or near previous industrial activities.
Not all urban soils will be affected, however, where contamination has occurred, the
following information will assist you to safely grow and enjoy your own produce.
How can I be exposed?
People can be exposed to contaminants in two main ways:
Soil-to-human pathway: The greatest risk of exposure when gardening is from
contaminated soil getting into your mouth or by breathing in contaminated dust. Children
playing in the garden may directly eat soil or people may eat plants without first washing
them to remove soil and dust. Skin contact with some contaminants can also pose health
risks.
Soil-to-plant-to-human pathway: Some edible plants can take up and accumulate
contaminants. A plant’s uptake depends on many factors including the type of plant, the
pH and the organic content of the soil. Root vegetables have a higher potential for
accumulating contaminants as they are grown in direct contact with the soil.
Reducing exposure to contaminants can be achieved through a combination of
preventative strategies, hazard reduction and good hygiene practices.
Wise gardening guide
Being cautious does not mean that you cannot enjoy gardens or grow your own food. In
general, the benefits of urban gardening greatly outweigh the risks. By following the
recommendations and best practices listed below, you will decrease your likelihood of
exposure to contaminants that are commonly found in urban soils.
Gardening tips
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Do not dig into or disturb existing soils.
Build raised garden beds. Line the inside with heavy-duty, semi-permeable,
landscape cloth over the ground to create a barrier between your garden beds and
the ground, and fill them with clean soil from a reliable source.
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Garden in containers to separate plants from the contaminated soil.
Improve the nutrient content of your veggie beds by applying compost and mulch.
Some contaminants bind to these organic compounds which may make them less
able to be taken up by the plant.
Maintain a pH of around 6.5. Lead and other heavy metals are less bio-available at
this level or higher. Add lime to soil to increase pH if needed.
Cover walkways and other areas of exposed soil with mulch, grass, paving or
other groundcover to reduce dust migration onto plants.
Reduce dust by wetting the soil and equipment before working in the garden.
Locate food gardens away from painted buildings that were constructed prior to
the 1980s.
Planting choices
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Fruiting plants such as tomatoes, capsicums, cucumbers, beans, okra, peas,
melons, corn, cauliflower, asparagus, celery, berries, pumpkin, apple and pear
trees are safer options as most metals tend not to concentrate in fruits.
Root crops such as carrots, potatoes and onions are least appropriate to be grown
directly into urban soils as their edible portions are in direct contact with the soil
(only grow in raised beds).
Leafy vegetables and herbs are more easily contaminated by dust and soil
splashback and can absorb more contaminants from the soil, but if grown and
prepared correctly can be safe to eat.
Poultry
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Ensure chooks don’t have access to bare soil. Restrict their free ranging to areas
where they can’t access affected soils.
All poultry require access to a dust bath - a large shallow pan (such as kitty litter
tray or children’s pool) filled with loose uncontaminated soil, sand, hardwood
ashes or a combination of these within the pen can provide an alternative to
scratching the ground.
Another method is to lay pavers or cover the soil within the pen with geo-fabric or
shade cloth before adding a deep litter layer of either straw, woodchips or another
type of mulch substance for the chickens to scratch, play and live in.
Food preparation
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Thoroughly wash all excess dust and dirt from produce prior to storage and eating.
Remove outer leaves of greens, especially from the bottom of plants.
Peel all root vegetables which are in direct contact with soil.
Hygiene practices
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Supervise young children to ensure they do not eat dirt or unwashed vegetables.
Wash hands immediately after gardening or wear gloves.
Wash hands before eating and preparing food.
By taking these simple steps, you will be able to safely and confidently garden and enjoy
the produce you grown.