Garden Soil Contaminants

Is the soil in my neighborhood safe for gardening?

Los Angeles has a long history of industrial activity, traffic pollution, and urban development, all of which can contribute to soil contamination. Some contaminants occur naturally, but many are due to past industrial operations, vehicle emissions, or older building materials such as lead-based paint.

Soil contaminants can be managed effectively, and gardening can still be a safe and rewarding activity. This guide provides advice on assessing your garden site for potential contaminants, managing soil quality, and following best practices for safe urban gardening.

 

What are the health risks of soil contamination?

Growing food at home or in a community garden is a great way to save money, improve nutrition, and promote environmental sustainability. However, soil contaminants such as heavy metals can pose health risks depending on the level and duration of exposure.

The good news is that, even in areas with some contamination, the risk of exposure from gardening is low if proper precautions are taken.

• Lead is a common contaminant in urban soil, particularly in older neighborhoods. While lead levels in the environment have declined over the years, even low levels can affect brain development in children and unborn babies.

• Arsenic, cadmium, and polycyclic aromatic hydrocarbons (PAHs) are also found in some urban soils and can pose long-term health risks with prolonged exposure.

• Garden soils tend to have lower contamination levels than the surrounding yard soil because gardeners frequently add fresh soil, compost, and organic matter, which help dilute contaminants.

 

How can I be exposed to contaminants from my garden?

The primary way people are exposed to soil contaminants is by directly ingesting soil—either through unwashed produce or by accidentally consuming soil particles. Children are especially at risk since they are more likely to play in the dirt and put their hands in their mouths.

Research shows that the risk from eating vegetables grown in contaminated soil is low if simple precautions are followed. The highest risk comes from soil dust on leafy greens or root crops, rather than the plants absorbing contaminants from the soil.

• Leafy vegetables (e.g., lettuce, kale) and root crops (e.g., carrots, potatoes) are more likely to have surface contamination.

• Fruiting plants (e.g., tomatoes, squash, strawberries, apples) tend to accumulate fewer contaminants.

 

How do I know if my garden soil is at risk?

The following factors increase the likelihood of soil contamination in Los Angeles:

• Homes built before 1990 may have lead in the soil from deteriorating lead-based paint.

• Properties near high-traffic roads may have residual lead from past use of leaded gasoline.

• Former industrial or commercial sites may have contaminated soil.

• Land with a history of rail lines, auto body shops, or printing businesses may contain heavy metals or chemicals.

• Soil that appears discolored, has an unusual odor, or shows signs of dumping may be contaminated.

 

How can I reduce exposure to soil contaminants?

If you suspect your soil may contain contaminants, consider these precautions:

• Grow produce in raised beds with clean soil and a protective barrier over the existing ground. The U.S. Environmental Protection Agency (EPA) provides guidelines on urban gardening best practices.

• Choose fruiting plants (e.g., tomatoes, beans, corn, squash) instead of leafy greens or root crops.

• Keep gardens away from old fences, houses, and roadways, where lead contamination is more likely.

• If renovating an older home, take precautions to prevent lead dust from spreading into your soil. Wet-sand surfaces and avoid power tools when removing lead paint.

• Consider soil testing if you are concerned about high contamination levels.

• Adjust your soil’s pH by adding limestone, as acidic soil increases the uptake of metals by plants.

 

Best Practices for Safe Gardening in Los Angeles

• Wash all produce thoroughly before eating.

• Peel root vegetables and remove outer leaves of leafy greens.

• Wear gloves when gardening and wash hands afterward.

• Change and wash gardening clothes separately to avoid bringing soil indoors.

• Use clean compost, soil, or mulch to improve soil quality.

• Avoid treated wood or railroad ties in garden beds, as they may contain toxic chemicals.

• Test new soil before adding it to ensure it is safe for gardening.

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Should I test my garden soil?

Soil testing is the only way to confirm contamination levels, but it can be costly. If you suspect high levels of contamination, testing may be worthwhile—especially if you plan to grow edible plants. However, for many urban gardeners, building raised beds with fresh, clean soil is often the simplest and safest solution.

For more information on soil testing and urban gardening safety, visit:

• Los Angeles County Department of Public Health (Environmental Health)

• California Department of Toxic Substances Control (Brownfields and Environmental Restoration Program)

• U.S. Environmental Protection Agency (Urban Gardening and Soil Contaminants)

By taking these precautions, you can enjoy gardening while minimizing risks and ensuring safe, healthy food production in Los Angeles.