Lead in soil and home gardening

Lead occurs naturally in the environment and has many industrial uses. Everyone is exposed to trace amounts of lead through air, soil, household dust, food, drinking water, and various consumer products.

Lead is a highly toxic metal that was used for many years in products found in and around our homes. Exposure to lead has decreased significantly since the early 1970s with the phasing out of lead-based paint, leaded gasoline, and lead solder in food cans.

If you have individual concerns about lead and your health, please contact your health care provider.

While lead occurs naturally in the environment, high lead levels in garden soil is usually the result of some human source of contamination. Home gardening can still be enjoyed in areas possibly affected by lead if the garden is properly planned to avoid potential sources of lead contamination.

Lead contamination usually originates from one or more of the following sources: past and current industrial fallout, old external paint, past use of leaded gasoline and pesticides that contain lead, street dust, and industrial waste disposal.

In garden planning, proximity to possible lead sources should be considered:

• Industrial fallout from metal mining, smelting and refining operations, battery plants, and other heavy industries.
• Lead-based paint may be a source of soil contamination. Lead-based paint was widely used in the 1940s. Lead in paint was reduced to very low levels by the 1960s and was severely limited by 1976. Soil can be contaminated by flaking or scraped exterior paint and lead dust particles from sanded paint.
• Leaded gasoline is a historical source of soil contamination. Lead in gasoline was available until the mid-1980s and was banned in Canada in 1990. Combustion of leaded gasoline produced lead-rich exhaust particles. Contamination is typically highest adjacent to roads, parking areas and driveways.

Choosing an appropriate site

Garden sites should be chosen to avoid potential sources of lead contamination. Potential indicators of concern include:

• within 5 metres of older buildings that were once painted with lead-based paints
• within 30 metres of major roads and parking areas that are more than 30 years old
• within 2 kilometres of existing or former industries known to emit or that have emitted lead

It may be important to have soil tested if lead contamination is suspected. Other protective measures are described below.

Developing garden plots

The risk of exposure to contaminated soil can be reduced in a number of ways. Effective measures depend on the type of garden being planned. For example, perennial or ground cover plants will require different solutions than vegetable gardens. Here are some general guidelines:

• Place a barrier, such as plastic sheeting, between contaminated and clean soil; provide for bed drainage.
• Build containers or raised beds and fill with uncontaminated soil. Avoid pressure-treated wood to prevent leaching of preservation chemicals.
• Cover the soil of ornamental flowerbeds with mulch to minimize exposure to contamination.
• Increase soil organic matter by adding compost, manure, and other organic soil amendments. This will help reduce plant uptake of soil lead as other nutrients are more readily available.
• Add high calcium lime or dolomite to soil to neutralize pH levels and reduce lead uptake into plants.
• Lightly moisten contaminated soil while handling to minimize dust.
• Replace contaminated soil with clean fill, always ensuring proper handling and protection.

Choosing plants for the garden

Soil exposure can be reduced by carefully selecting garden plants. For example, perennials and ground covers require less regular soil preparation than most annual plants. Some vegetables are less suited for contaminated soil than others. Soil lead testing can provide valuable information on the safety of consuming homegrown produce. Some general guidelines on vegetable selection follow:

• Seeds and fruit typically have lower lead concentrations than leaves, stems, or roots.
• Roots and tubers usually have the highest lead concentrations (the skins having higher lead concentrations than the inner flesh).
• Fruit crops such as tomatoes, berries, apples, and cucumbers present a lower risk because they take up and store very little lead.
• Leafy greens can be prone to higher external contamination uptake and storage.

Clean fruit and vegetables to minimize exposure

Clean vegetables thoroughly before eating in order to minimize exposure to contaminated soil. Keep in mind the following basic guidelines:

• Wash garden crops with water before bringing them into the house.
• Thoroughly wash fruit and vegetables with drinking water before serving or preparing. Keep in mind that rough surface crops like broccoli and lettuce can trap dust.
• Use a scrub brush if possible.
• Peeling root crops to remove skins may reduce lead exposure.

Other guidelines for healthy gardening

Gardening can be a wonderful and safe activity when the proper precautions are taken:

• Designate certain clothing, including footwear, for gardening use and store outside. Remove gardening footwear before entering the house.
• Don’t drink, eat, or smoke when gardening.
• Wash soil from gardening tools and supplies outside after each use, and store tools outside.
• Wash hands and all other exposed body surfaces after gardening.
• Keep young children away from soil contaminated with lead.
• Be aware that pets, particularly dogs, are often exposed to soil dust — brush them regularly and brush them outside.

Children are more susceptible than adults to the health effects of lead exposure. Take the following precautions:

• Wash children’s hands often, especially before they eat, before nap time, and bedtime and after they come in from outside.
• Ensure that children wash their feet after playing barefoot outdoors.
• Keep play areas clean. Wash bottles, pacifiers, toys, and stuffed animals regularly.
• Keep teething children from chewing on windowsills, toys, or other painted surfaces.
• Make sure children eat the right amount and type of food recommended (Government of Canada).