Gardening and Soil Contaminants

Are soils in my community suitable for gardening?

Soil in some communities or neighbourhoods in urban areas can contain contaminants. Contaminants may be present in the soil naturally. However, most are present because of industrial activities, traffic or products used around the home in the past (such as lead paint).

Lead, arsenic, cadmium and polycyclic aromatic hydrocarbons (PAHs) are some of the more common soil contaminants. Other contaminants can be found near commercial or industrial sites. However, garden soils tend to have lower levels of contaminants, as homeowners add new soil to improve the health of the garden.

What are the health risks of exposure to contaminants?

Growing food at home or in your community is a great way to save money, improve nutrition, and practice environmental stewardship. The health risks associated with back-yard gardening, even with contaminated soil, are low to very low unless soil contamination levels are extremely elevated.

Metals and other contaminants can affect a person’s health depending on the amount of exposure and the length of time of exposure. In particular, exposure to low levels of lead can be harmful, especially to children.

For more information on the common soil contaminants and your health, please see the following fact sheets:

How can I be exposed to contaminants in soil from my garden?

Directly consuming the soil is the greatest risk.  For example, children may directly eat soil, or people may eat garden produce without first washing it to remove soil and dust.

Research has shown there is a very small risk of exposure to contaminants from eating vegetables grown in contaminated soil, if precautions are followed.

For garden produce, most of the risk from contaminated soil is due to the dust deposits on the surface of leafy vegetables or on the surface of tuber vegetables (such as carrots and potatoes), rather than from plant uptake of contaminants from the soil.

However, it is possible for plants to take up some amount of the contaminants if present in the soil. Certain soil conditions make this more likely. Uptake by plants is more likely if the soil is acidic and low in organic matter, where concentrations of lead, arsenic and cadmium are high. Certain types of plants may take up more contaminants than other types. Studies have shown that lead does not readily accumulate in the fruiting parts of vegetable and fruit crops (such as corn, beans, squash, tomatoes, strawberries, apples). Higher concentrations are more likely to be found in leafy vegetables (such as lettuce) and on the surface of root crops (such as carrots) because they grow underground.

What can I do to reduce my risk of exposure to contaminants in my home grown produce?

If contaminants are (or may be) present in your soil, there are many options to reduce your exposure. Most importantly, you need to wash all of your produce before eating it. You can also consider creating a new garden with fresh soil, or you can add various things to your current soil to reduce the likelihood of uptake of metals by the plant.

Tips for All Gardeners

  • Wear gloves and wash your hands after working in the garden.
  • Avoid having young children playing in the garden and in bare soil areas if you live near a major roadway or an industrial / commercial area. If your home was built before 1978 when lead paint was used, the paint may have flaked off and be lead may be present in the soil. The older the home, the greater the risk.
  • If your home was built before 1978, be careful when you do outside renovations. Cover the ground where you are working to prevent lead paint from getting into the soil. Use water to keep the paint you are disturbing wet, and do not use power tools to remove paint. This will prevent lead paint dust from getting into the air and soil.
  • Keep soil outdoors by removing shoes and using doormats. Do not bring the shoes you wear while gardening inside your home.
  • Wash the clothes you wear while gardening separate from other laundry.

Should I test my garden soil?

You cannot know for sure if there are contaminants in your soil without having it tested by a laboratory. Determining if there are contaminants in soils is expensive and not recommended on a routine basis. However, if you suspect high levels in the soil that you plan to use for gardening, it may be helpful to have the soil tested. In some cases, it may be prudent to avoid growing edible plants in soils with high contaminant concentrations.

For more information on soil assessments, please see the Vancouver Coastal Health fact sheet:
http://vancouver.ca/files/cov/guide-to-reduce-health-risks-urban-farming.pdf

For information on where your soil can be tested is available at:
http://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-testing-in-manitoba.html.

 

Public Health | Environmental Health
Manitoba Health, Seniors and Active Living

4th Floor - 300 Carlton St.
Winnipeg MB  R3B 3M9
CANADA
Phone: 204-788-6735
Fax: 204-948-2040