Are There Dangerous Levels of Lead in Local Soil?

Objective

The purpose of this project is to determine whether local soil contains dangerous levels of lead. This is significant because the results will indicate where the soil is hazardous to the health of humans, especially young children.

Introduction

Lead is an element that has been used for centuries in many objects found in and around the home. Lead is also highly toxic to human health. In the 1980's federal, state, and local governments moved to ban the use of lead in common household materials. However, there are products that were created before the 1980's still in use today. Many areas also have soil contaminated from previous use of these products. Are there areas around you where residual products have caused the soil to be hazardous to the health of humans, especially young children?

Terms, Concepts and Questions to Start Background Research

In order to properly conduct this experiment you should become an expert on lead. You should understand:

What are the health effects of lead?
What levels of lead are hazardous?
When does lead become hazardous to humans?
How does lead get into soil?

Bibliography

General information on lead, its history, and its health hazards, and areas around your community that you might want to check for lead contamination can be found at the following websites:
http://www.epa.gov/lead/
http://www.epa.gov/lead/leadpbed.htm#Brochures
http://www.epa.gov/history/topics/perspect/lead.htm
http://www.niehs.nih.gov/external/faq/alpha-l.htm#lead

A good list of additional offline sources from Environmental Science Archive of Ask A Scientist:
http://www.newton.dep.anl.gov/newton/askasci/1995/environ/ENV134.HTM

Guidelines for soil sampling for residential property:
http://www.ecy.wa.gov/pubs/0309044.pdf
http://www.ext.colostate.edu/pubs/crops/00500.html

Materials and Equipment

Resealable plastic bags to hold samples
Shovel
Stainless steel spoon
Permanent marker
Large bowl or bucket
Paper towels

Experimental Procedure

Determine your sampling locations and where, within that location, you are going to collect sub-samples. Lead concentrations can vary from one spot to another, so it is important to use a composite of sub-samples to evaluate an area rather than relying on a single sample. The exception to the composite technique would be if you are trying to get a specific measurement for a small area (for example, around a play structure).
Collecting a composite sample (adapted from the Washington State Department of Ecology Arsenic and Lead Soil Sampling Guidance Brochure):
- Sketch out a map of the location that you will be testing and note where you will be collecting each of your samples. You should collect at least 4 samples from smaller areas (for example, a small yard that is less 800 sq. ft.) and at least 15 samples from larger areas (for example, a small neighborhood park).
- Remove material on the soil surface (grass, leaves, etc.), exposing the soil.
- Dig a hole with your shovel. The depth will depend on the test you are using to analyze the soil—check the instructions on the home kit or with the analyzing lab to get a specific soil depth recommendation for your samples. (Typically you should not dig deeper than 6 inches).
- Using your spoon, scrape some soil from the hole and place it in a clean plastic bag. Make sure to collect only soil—do not include rocks, grass, or wandering insects.
- Clean the spoon with a paper towel to remove any visible traces of soil.
- Repeat steps 2–5 for each of the sub-samples for this location.
- Once you have collected all of the sub-samples for a location, put equal amounts of each sub-sample into your bowl and mix them together.
- Take a sample from this composite soil mixture and put it in a new plastic bag. This is the sample that is tested.
- Mark the plastic bag with the location name and date of collection.
- Repeat steps 1–9 for each of your sample locations.
Testing the samples: There are a number of do-it-yourself kits that test for lead available on the market. Unfortunately, according to the EPA, these kits simply test for the presence of lead, and do not provide enough distinction between high and low levels of lead (http://www.epa.gov/lead/qa4.pdf). To accurately draw conclusions from your samples, we recommend that you do the following:
- Use a home test kit to get a positive or negative reading on the lead content of your samples. These results will give you enough information to claim that lead is present.
- For those samples that show positive indicators for lead, do a follow up check with a soil testing laboratory. There are laboratories associated with universities (for example, University of Massachusetts [http://www.umass.edu/plsoils/soiltest/lead1.htm]) as well as commercial laboratories (see http://www.ext.colostate.edu/PUBS/crops/00520.html for a list of some).