Lead Levels in Residential Soil in Proximity to a Superhighway
My home is located in a quiet, wooded town in Suffolk County, Long Island. My parents chose the location, nestled in the woods, to enjoy the land's rustic beauty, as well as for convenient commuting. While growing up, my friends and I spent countless hours outside exploring the woods, digging in the dirt, and playing sports in the backyard. In early autumn, the area is particularly lovely as the leaves turn colors and fall from the trees. However, during this time of the year, as the leaves thin and the natural sound barrier is gone, I begin to hear the din of the LIE in the distance, heightening my awareness that we live close to a major expressway. Unfortunately, being near to the expressway, I also experience the constant strong scent of burning gasoline.
One day, upon returning home after a scooter ride, my mother told me that my siblings and I would be going to the pediatrician for our annual appointments. My brothers and I didn't require any immunizations. However, my adorable toddler sister needed to have her blood drawn to test for lead.
Apparently, the risk of lead toxicity is greatest in young children my sister's age, who are crawling on the floor and placing objects into their mouths. In children, lead poisoning occurs most often from exposure to old lead-based paint. Residential use of lead-based paint has been banned in the state of New York since 1978, but older homes may contain lead in chipping or peeling paint even after the house has been repainted. This is problematic because when a window is opened or closed, the friction may result in lead dust settling on and near the window. In fact, my sister loves to peer out the upstairs bedroom window as she waits for my brothers and me to get home from school. Sometimes she mindlessly places her mouth on the sill as she waits. Thankfully, I don't need to worry about my sister swallowing lead particles because lead use was being phased out at the time that our home was built (Primi, 1999).
Still, my thoughts turn to the lead in gasoline. Pollutants like lead have been emitted into the air, settled on the ground, and accumulated over the years. There are homes in my neighborhood whose backyards are adjacent to the service road of the Long Island Expressway. I begin to consider the environment of my own home, 0.3 miles from the LIE. I wonder if our soil is contaminated with lead.
A "Leaded" History
Lead is a naturally occurring element, a heavy, soft, blue-gray metal. One of the earliest metals discovered by ancient civilizations, lead was first found in a Turkish statue that dates back to 6500 BCE (HMA, 2006). The first use of lead was for plumbing in ancient Rome (plumbum is Latin for lead). Sections of drainage pipe with the insignia of Roman emperors are still in use and in perfect condition. Furthermore, in ancient Rome, lead was a component of face powders, rouge, mascara, paint pigment, dishes, pots, and kettles. Lead was sprinkled on foods as a condiment and used as a preservative for wine (Lewis, 1985).
The Romans were aware that lead could cause severe health problems, including madness and death. They believed, however, that that these adverse effects occurred only with the high levels of exposure of miners or smelters. These workers were typically slaves, whose health was not of concern. Lead mining was prohibited in Rome, and eventually all mining and smelting was relegated to the provinces. Historians, however, hypothesize that lead toxicity affected the nobility as well. Epidemics of gout, sterility, and the mental incompetence of the Roman elite are thought to have been a result of chronic exposure to low levels of lead from ingesting contaminated food and wine (Lewis, 1985).
Recent literature reveals that very low levels of lead exposure result in brain injury in children, perhaps resulting in decreased intelligence and learning disabilities (Canfield, 2003; ATSDR, 2005). Nonetheless, lead continued to be used in ammunition, paints, dyes, glazes, pipes, caulking, batteries, pesticides and cosmetics. Additionally, in the 1920's tetraethyl lead (TEL) was added to gasoline to reduce engine knock (Lewis, 1985). TEL was heavily promoted for its benefits of "increased speed, more power, and increased acceleration." Advertisements featuring "Ethyl" as an attractive woman read "Fill your tank with Ethyl today. You'll find a real difference in driving satisfaction" and "Take me with you and you will get a kick out driving instead of a knock" (Detwyler).
By 1980, the U.S. was consuming about 1.3 million tons of lead per year, about 40% of the world's supply (Lewis, 1985). However, the health damage caused by lead could not be ignored forever. In 1973, the Environmental Protection Agency mandated the reduction of TEL in gasoline (EPA, 1973). By 1986, the maximum lead level in gasoline was reduced from an industry average of 2.4 grams of TEL per gallon of gasoline to 0.1 gram per gallon. By then, 7 million metric tons of lead were present in gasoline in the U.S. Finally, effective January 1, 1996, the Clean Air Act banned on-road use of leaded gasoline, although off-road use in aviation and farm equipment continued (Detwyler; EPA, 1996).
Before the use of lead in gasoline was banned, most of the lead in the environment was from vehicle exhaust (EPA, 1973). Once lead particles get into the atmosphere, they may travel long distances. When lead finally falls onto soil, it sticks strongly and remains in the upper layer of soil for many years. Neighborhoods in close proximity to major roadways may contain high amounts of lead in the soil that potentially pose a risk to residents.
The Long Island Expressway
The Long Island Expressway is a 70.8-mile-long, six-plus-lane interstate highway (Route 495) extending from the Queens Midtown Tunnel (in the borough of Queens) to Riverhead (in Eastern Suffolk County, Long Island). Construction of the LIE began in 1939 in Queens. Over a couple of decades, the LIE was extended across Nassau County. By the middle of 1962, it crossed the Nassau-Suffolk border. Over the next decade, as the LIE expanded, Suffolk County was transformed from a rural region of potato farms into sprawling suburban homes, shopping centers, and industrial parks. In 1972, the final segment of the LIE was completed, extending to Riverhead, now a major industrial hub (Anderson, 2006).
With the LIE came heavy traffic. The LIE handles approximately 210,000 vehicles per day through the borough of Queens, 190,000 per day through Nassau County, and 150,000 vehicles per day through Western Suffolk County, largely because Long Island has become one of the most densely populated areas in the U.S. (Anderson, 2006). Since the LIE deliberately slices through the central lateral core of Long Island to provide easy commuting access to all residents, there are numerous homes, like mine, that are in close proximity to the Long Island Expressway. The soil of homes near the LIE may have elevated lead levels and pose a health threat, a fact that few Long Island residents presently realize.
My hypothesis is that lead levels in the soil of residential property located in close proximity to the LIE will be elevated when compared to similar properties that are located further from the LIE.
To test my hypothesis, I collected soil samples from designated sites along the LIE. The sites I used were at the following distances from the LIE: along the LIE, 0.1 mile, 0.3 mile, 0.5 mile and 1.0 mile. Three sets of samples were taken for each site. Digging for soil samples along the LIE was an unnerving experience. As cars sped by, I could smell the fumes from the car exhaust and feel the ground rattling beneath my feet. I felt personally endangered standing so close to the LIE and was reminded of the potentially severe effects of car exhaust on the environment as well as the relevance of my particular project.
Before testing, the soil was dried overnight, debris and stones were removed, and clumps of soil were broken up. I performed initial testing at home with the Sensafe Soil Check™ kit. (The testing procedure is included in Appendix A (below).) This kit was utilized as a qualitative test. Results would be either positive (pink) or negative (gray), with a detection limit of 100 parts per million (ppm). Soil samples collected from the LIE and at distances of 0.1, 0.3, and 0.5 miles from the LIE were all positive. However, many of the samples were a mixed color, i.e. light pink/gray, and I initially had difficulty determining the dominant color. I felt as though I was guessing at the result. This made me see the limitations of a test using a colorimetric indicator. Test strips of soil samples in closer proximity to the LIE were a deeper pink than samples further from the LIE. Higher concentrations of lead showed a more intense pink coloration, even though the Sensafe Soil Check™ kit is not designed to give a quantitative lead analysis. Two of the three samples collected one mile from the LIE were negative; the third was positive but very light pink/gray in color. These preliminary results conducted with a home testing kit led me to believe that my hypothesis might be correct: that the closer a residence is to the LIE, the higher the lead levels in the soil.
However, to further test my hypothesis, quantitative testing would be necessary. I contacted the U.S. Environmental Protection Agency to locate an accredited laboratory near my home. I was referred to EMSL Analytical, a national laboratory with a testing facility in Carle Place, Long Island. At the laboratory, I met with professionals who provided tremendous encouragement for my research and patiently demonstrated and explained each step of the analysis. The lab scientists gave me an in-depth tour of the laboratory, glad to see a high school student take an early interest in environmental science. The process began with a chain of custody, that is, an information form recording the owner of the sample, where the samples originated, and the numbers given to samples for accurate identification. After completion of the appropriate paperwork, lead analysis of each sample was conducted by use of atomic absorption spectroscopy. The atomic absorption unit consists of a lamp that emits light with an element-specific wavelength (set for lead in my analysis), a sample aspirator, an acetylene flame for volatizing the sample, and a photon detector.
Following appropriate dissolution of the soil samples, a representative aliquot was aspirated into the acetylene flame. Ions of lead present in the flame absorbed light produced by the lamp. The amount of light absorbed depends on the amount of lead in the sample. The resulting absorption of hollow cathode radiation indicated a measure of lead concentration that was then recorded (EMSL, 2006; McGowan and Benoit, 2006).
Final results revealed a correlation between proximity to the LIE and elevated lead levels. Average lead levels obtained from soil on the shoulder of the LIE were 350 mg/kg and rapidly diminished at 0.1 mile to 63 mg/kg. By 0.3 mile the concentration was 31 mg/kg, and at 0.5 mile the level was 18 mg/kg. The levels did not diminish further at 1.0 mile from the LIE, with a lead concentration in the soil of 19 mg/kg. The correlation was greatest within one half mile from the LIE, with a correlation coefficient of -0.68. However, soil samples in residential areas, even those closest in proximity to the LIE, did not exceed 400 ppm, which is the hazard level for play areas as set by the EPA ( Federal Register , 2001). This is likely a result of the removal of lead from gasoline over the past few decades.
After analyzing the samples, I found a clear inverse correlation between distance from the LIE and lead concentration in soil.
This project made me a lot more sensitive to environmental concerns. We are indeed privileged to reside in a relatively healthy environment. This project clearly alerts us to the fact that our aggressive technologies stand to degrade the quality of the environment, ultimately affecting our personal health. This project underscores the importance of responsible behavior toward preservation of our environment now, so that future generations may enjoy life in a safe and healthy environment.
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Atomic Absorption Methods, Method 7000A. EMSL Analytical Inc., Policy and Procedure Manual, April 2006.
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Carlyle, Benoit. Interviewed by Max Schneck. April 2006.
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More About This Resource...
This winning entry in the Museum's Young Naturalist Awards 2006 is from a New York 9th grader. Max tested lead levels near the Long Island Expressway. His essay includes:
- an overview of lead and how this naturally occurring element has been used since ancient times and the risks it poses;
- details of the materials and methods he used to test his hypothesis that lead levels will be higher in the soil of residential properties close to the Long Island Expressway; and
- the results of his experiment, which proved a correlation between distance from the LIE and lead concentration in soil.
Supplement a study of earth science with an activity drawn from this winning student essay.
- Ask students what they know about lead. Have they had younger siblings tested for lead levels?
- Send students to this online article, or print copies of the essay for them to read.
- Working individually or in small groups, have students research and report on the hazards exposure to lead can have on humans, particularly children.
OriginYoung Naturalist Awards
SubtopicMinerals and Resources