By far, the most common type of contaminant in an urban soil is lead. Elevated lead in urban soil comes from the historic use of leaded gasoline and lead paint.
Is your soil contaminated with lead?
Your soil is most likely to be contaminated with lead if you live next to a very busy, high traffic road that has existed for more than 40 years. Lead in exhaust from cars when leaded gasoline was still in use will have contaminated the soil.
Your soil is also more likely to be contaminated if you live in an older home (50+ years) that is painted. Lead paint may have chipped off your home and landed in the soil directly next to the house.
In other words, if you live in a brick house or in a newer house on a quiet street it’s highly unlikely that you have elevated lead in your soil. But if you live in an older home or near a busy street, your soil may have high lead.
Why is lead a concern?
Lead is primarily dangerous for kids. Because they are growing, little kids are much more efficient at absorbing lead than adults. Excessive exposure to lead can cause developmental delays, reduce brain function, and result in damage to motor skills.
Kids and adults are not exposed to lead just by touching lead-contaminated soils. However, they can be exposed to lead by breathing in high-lead dust or eating lead-contaminated soil.
Barren, lead-contaminated soil poses a much greater risk than lead-contaminated soil that covered by vegetation.
That’s because soil covered by plants will be much harder for kids to get on their fingers. Soil covered by plants is also much less likely to be taken up by the wind and end up as dust in your house.
Kids are at greater risk both because they absorb lead much more efficiently than adults and because they are much more likely to eat soil than adults.
Some kids will eat soil on purpose; this is called Pica behavior. Almost all kids will eat soil by accident. Licking ice cream off dirty hands is a classic way that kids ingest soil.
Can plants grown in lead-contaminated soil hurt you?
It’s hard to be exposed to lead by eating vegetables or fruits. Plants do not take up lead on purpose, because lead is not a plant nutrient. Plants may contain measurable amounts of lead, but this isn’t because plants are actively taking up lead from soil, but because we’re able to measure very low concentrations of lead in environmental samples.
Plant concentrations of lead are generally very low—in the range of parts per billion.
- 1 part per million is the same as one penny in $10,000
- 1 part per billion is the same as one penny in $10,000,000
Not only do plants take up minimal amounts of lead, but it’s much harder for the body to absorb lead—even from food that contains it—on a full stomach in comparison to an empty stomach.
This is because an empty stomach is very acidic, which makes the lead in soil or food more soluble and more easily absorbed. A full stomach, in contrast, is not acidic and so the lead will be much less soluble. In addition, there are many other elements that the body needs, including iron, zinc, and calcium, that will be absorbed instead of the lead.
- CDC: ToxFAQs for Lead
- U.S. Environmental Protection Agency (EPA): Fact sheet on the leaded gas phaseout
- TIME magazine: Leaded gasoline, one of TIME’s 50 worst inventions
- U.S. EPA: Information on lead