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Garden Safe

Interpreting Your Soil Test Results

If you have submitted soil samples for Indiana University to test, the following information will help you interpret your results to minimize your exposure to lead.

What Is Lead?

Lead is a naturally occurring heavy metal. Because it is abundant and cheap, lead has been used in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding (for example, when the dentist takes x-rays, you must wear a lead shield). Lead was phased out of automobile gasoline in 1996 and removed from paint in 1978.

Background levels of lead in soil range from 10 to 79 parts per million (ppm). In Indiana, the average is around 30 ppm.
(Source: https://www.epa.gov/superfund/usgs-background-soil-lead-survey-state-data#IN)

Urban soils are often higher.

Exposure to Lead

People often associate lead exposure with contaminated water; however, for most people around the world, the dominant exposure pathway for lead is through dust. Lead found in house dust comes from various sources, inside and outside the home. Lead occurs naturally in the environment in small amounts. However, leaded gasoline, lead-based paint, agricultural pesticides, and industrial pollution have all artificially increased lead levels in soil, especially near urban centers.

Not all urban homes will have high lead in their soil/dust, but if you live in a city, being aware of the risks and getting your soil/dust tested are essential first steps. Rural homes may have lead-contaminated soil and dust as well. For example, if your home was built before 1978, it may contain interior and exterior lead-based paint. Furthermore, rural and suburban homes constructed on land formerly used for agriculture, especially fruit orchards, may have soil contaminated by lead-based pesticides.

Lead is equally toxic when inhaled as dust or ingested in water. It accumulates in bones and is distributed throughout the blood to most organ systems, including the brain, where it acts as a neurotoxin. The U.S. Agency for Toxic Substances and Disease Registry (ATSDR) considers lead so toxic that they list no acceptable Minimal Risk Level (MRL) for oral (water) or particulate inhalation (dust).

Why Is Lead Hazardous to Humans?

According to the Centers for Disease Control, no level of lead is safe in humans, especially children.

Lead-based paint is especially hazardous to young children because of its sweet taste. As older lead-based paint ages and flakes, children may be tempted to eat the flakes because of this sweetness. Even low levels of lead exposure during early childhood can result in lifelong reduced IQ, decreased attention span, decreased impulse control, and increased antisocial behavior. People who experience childhood lead poisoning make less money over their lifetime and are more likely to be incarcerated than their peers.

Find additional information about lead as an environmental contaminant at:
ATSDR Toxic Substance Report for Lead (https://bit.ly/cdc-lead-toxic-substances)

Contextualizing Your Soil Lead Levels

If you have elevated levels of lead in your soil, determining how you want to interact with your soil will guide your next steps. Click on the heat arrow below to download a PDF of actions you can take to protect yourself and your family when interacting with your soil. Then read on for tips on reducing your exposure to lead in soil and dust. 

Soil Lead Heat Arrow

How to Reduce Your Exposure to Lead in Soil

By testing your soil, you have taken the first step toward living safely with lead pollution. Follow these recommendations to minimize exposure to lead in your home. Even if you cannot follow every guideline below, each change you make will reduce your lead exposure.
  • Wash your hands after working or playing outside and teach children to do the same.
  • Plant and maintain grass: Your lawn does not need to look like a green carpet or be weed-free. The goal is to keep the soil underneath the grass from being exposed enough that it creates dust. Grass creates a barrier between people or pets and the underlying soil, helps keep soil damp, and holds soil in place, reducing the overall risk of soil contamination.
  • Cover loose soil: Add layers of mulch to otherwise bare soil. Mulch, cardboard, gravel, and plants are all good at maintaining soil moisture and reducing soil-generated dust.
  • Irrigate and mulch: Mulch and water grass during dry spells to reduce dust.
  • Build raised beds: If you are a gardener and your soil lead concentrations are higher than 80 parts per million (ppm), we recommend that you build raised beds and fill them with clean topsoil and compost for growing vegetables, fruits, and herbs.
  • Elevate play areas for children: Build playsets on raised areas filled with wood chips if your soil lead concentrations exceed 80 ppm.
  • Install flagstone paths: To minimize dust transport in high-traffic areas, build stone paths.
  • Wipe those paws: We all love our pets, but your dog or indoor/outdoor cat can bring significant amounts of outdoor dust inside. If you have pets that go outside, be aware of the extra dirt and dust carried on those furry little paws. Please do your best to keep them as clean as possible to reduce contamination in your house.

How to Reduce Your Exposure to Lead in Dust

Because soil is easily tracked into your home, consider following these tips to minimize exposure to lead-tainted dust in your home.

  • Remove your shoes: Take your shoes off at the door when you enter your home.
  • Wash your hands: After working or playing outside, wash your hands and teach children to do the same.
  • Clean with a damp cloth: Dry methods of cleaning and dusting, using feather dusters, for example, can kick up dust. Instead, use a damp cloth. Moreover, using a damp dust mop on hard floor surfaces is preferable to sweeping with a dry broom.
  • Vacuum with a HEPA filter: If possible, vacuum carpets and rugs with a vacuum cleaner equipped with a high-efficiency particulate air (HEPA) filter. It will trap more fine particulate matter than a standard vacuum cleaner.
  • Isolate contaminated clothing: If you have high lead concentrations in your soil, change and wash clothes when you come in from working or playing outside. If you are exposed to lead in your occupation, change and wash clothes when you come home from work.
  • Clean at a child’s level: Children have a different perspective on the world from adults, literally and figuratively! You may not frequently touch the windowsills in your home or spend time playing on the floor, but do your children? When cleaning, if you have young children, pay special attention to those surfaces at lower levels that they touch frequently.

Additional Resources

In addition to the lead safety tips outlined above, the following resources may be helpful.