MSU Extension Gardening in Michigan

Lead naturally occurs in small quantities in the soil. Additional factors such as pollutants and lead-contaminated products can increase the concentration of this highly toxic metal to levels that can be hazardous. In Flint, Michigan, irrigation with lead-contaminated water did not show a significant increase in soil lead levels. Still, the lead already present in soils can persist for long periods. It is important to consider previous land use in your gardening plans.

If you are not sure what was on or near your garden site previously, Michigan State University Extension recommends getting your soil tested. Residential areas with historic lead paint use, industrial areas and high traffic roadsides potentially have increased soil lead levels. In undisturbed soils, concentrations are generally highest in the top 3 inches of the soil surface. This risk is not only present with vegetable gardening in high-lead soils but is also a concern to gardeners with landscape beds.

The concern with lead-contaminated gardens is primarily about contact and inhalation of the soils. The risk is more significant in areas with higher lead concentrations, so it is important to get your soil tested to understand the lead levels in your garden better. Children have a much higher risk of being affected by lead, and the neurological effects can sometimes be severe. Whether growing a food garden, an ornamental garden, planting trees, or working on the soil, precautions should be taken to reduce your risk of exposure.

If you are a gardener and lead contamination is a concern in your area, you can minimize the risk of exposure to yourself and others by taking the following precautions.

General precautions

• Get your soil tested. If you purchase MSU Extension’s convenient soil test kit through the MSU Extension Bookstore, be sure to speak with MSU Soil and Plant Nutrient Laboratory if you need a lead test for your soil, as this is not included in the basic test.
• While not always possible, maintaining a soil pH between 6.5 and 7.5 can minimize the availability of lead to plants.
• Organic matter is particularly good at holding on to lead, so as you increase soil organic matter, you decrease the amount of “available” lead in your soil. This also reduces the likelihood of fine soil particles carrying lead that can easily be trapped on clothing, skin, or inhaled.
• Mulch any bare soil to prevent lead-contaminated soil dust from drifting onto other plants and garden surfaces.
• Wear gloves when gardening.
• If lead inhalation from soils is a concern, wear a mask to protect yourself while gardening.

For a food garden

• Depending on your results, choose suitable items to grow.
• Avoid growing root crops such as carrot, beet, rhubarb, low-growing leafy greens, and parsnips in lead-contaminated soils.
• Remove soil particles and dust from vegetables. Peel your root vegetables, remove the outer layers of leafy vegetables and wash any fruit and vegetables thoroughly in clean, filtered water.
• Do not grow edible produce if soil lead levels exceed the recommended guidelines. Cover the existing soil with a barrier and build a raised bed for produce, especially root vegetables and leafy greens.
• Plants grown in high-lead soils have the potential to accumulate lead in their roots. Avoid composting root crops that have been grown in high lead conditions with poor soil quality. This can contaminate your compost pile.

For an ornamental garden or yard

• If lead levels in your soil are above the Environmental Protection Agency’s (EPA) recommended 400 parts per million (ppm), prevent children from playing or gardening in that soil, and do not leave bare soil accessible.
• Allocate a specific play area for children with a sandbox or covered substrate to minimize exposure to soil. Keep this area away from old painted buildings.
• Use a dense layer of sod in your yard and keep kid’s play areas away from bare soil.
• Avoid tracking soil into your home.

Unless you dilute your soil or amend it, there is very little you can do to reduce the concentration of lead in your soil. Therefore, it is important to take the appropriate measures to protect yourself and your children from the risks associated with lead exposure.