Measuring Lead in New York City Soils

By Benjamin Bostick

Lead poisoning has been in the news often over the last few years. In Flint, Michigan, and East Chicago, Indiana, water and soil contamination have exposed tens of thousands of people, including children, to worrisome levels of lead. These cities are not alone. More than 1 million children go to school in New York City public schools, and a significant number of those children have elevated and unsafe blood lead levels, defined as exceeding 5 micrograms per deciliter of blood. Soil and water contamination could be important sources of lead in New York and other environments.

Over the last several months, a group of five high school students from charter schools in Brooklyn, New York, have been working with me to understand the extent to which soil contributes to lead exposure in New York City. This opportunity is made possible through a research experience program through Uncommon Schools in collaboration with the Lamont-Doherty Earth Observatory at Columbia University. The program takes place during the fall and spring semesters.

Below are two parallel discussions about the students’ experiences, written by the students themselves. One focuses on their evolution in understanding lead pollution and its impacts on large populations. The other examines how the experience of working on authentic research has given them insight into what it means to be a scientist, and how they can contribute to science.

For more information about the program, please contact Cassie Xu (cassie@ldeo.columbia.edu).

What Have We Learned About Lead Contamination in Soil?

By Yarleny Andeliz (Uncommon Charter High School), Kizmat Alabi (Uncommon Collegiate Charter High School), and Cyprene Caines (Uncommon Preparatory Charter High School)

On our first day, we had to learn more about our project and lead and why New York City has a lead problem in the first place. We learned that the reason there is such a high concentration of lead in the soil is because New York City has had a history with burning garbage. Up until 1940, the amount of garbage people burned each year kept increasing at an alarming rate. However, in 1940, people began to realize that this practice was a hazard to the environment. With that, the city began to make laws banning the burning of trash.

The reason that burning trash was so unsafe was because some people burned garbage that contained batteries. When a battery burns, it releases certain chemicals, including lead, which linger in the environment and trickle down into our soil. This is especially problematic for New York City, because a lot of the buildings here are old and the soil isn’t being replaced very often. For example, places like Greenwich Village and SoHo have some of the highest levels of lead concentrations in New York City because they have some of the oldest buildings in New York. As a result, the lead and toxic chemicals that have come into the soil are still there and now affect thousands of people. Out of the 8.5 million people that live in New York City, about 400 thousand have severe lead contamination in their blood.

Soil Sampling

Our first field experience was in Riverside Park, which stretches for four miles and runs along the Hudson River. We chose this location because it’s a very public area where lots of kids go to play. There are six major playgrounds for children in Riverside Park. Since young children are very susceptible to lead poisoning, it’s possible that they could receive lead poisoning from public parks. Out of the 1.1 million children that currently attend NYC schools, more than 100,000 children are affected.

Before we went out to the field, Dr. Bostick had us thinking about all of the different aspects we have to consider before picking out a soil sample. One important thing we considered was the location—not only longitude and latitude coordinates, but also what was the sample near (i.e. whether it was near water or on a hill, etc.). We also took into consideration the depth of the soil and whether or not the color of the soil changed based on its depth.

We collected 29 samples in total from Riverside Park using a core. After collecting the soil samples, we went back to the lab to test what chemicals were in the soil using an XRF [x-ray fluorescence] machine. After doing this, we noted that soil samples even within a meter apart in distance have different concentrations of lead. Also, we found that the deeper the soil, the lower the lead concentration was, meaning soil with lead in it doesn’t really mix in, leaving most of lead on the surface of the soil. However, because we took data from a public park, we considered the animals within the park and how they can impact the lead concentration. We concluded that a lot of the animals, like squirrels and worms, can actually help to mix the soils with both low and high concentrations of lead.

Working with Data at the Lamont Doherty Earth Observatory

As part of this research, we have had extensive discussions about the different factors that increased the levels of lead concentration over time. We then tried to create a cohesive graph that explained these different variables that we came up with, such as the neighborhood, the layout of the land, and the specific area that the soil was coming from (for example, a garden with a fresh bed of soil or an area near the water where erosion could occur).

Testing for Lead Bioavailability at Barnard College

Not all of the lead in soil is equally toxic. We learned how to use chemical extractions to measure how much lead dissolves from soil under acidic conditions like those in our stomachs. The point of this research is to determine how much of the lead in soil can dissolve and end up in your blood and then your bones and other places in the body where it can stay for years to come. We learned that in some cases, most will dissolve, whereas in other cases, very little will dissolve. The reason for these differences is that lead is found in different compounds in soil, and some are much more soluble than others.

Next Steps

We are assisting on the development of a mobile phone application to allow us to collect data about lead contamination levels quickly, and to confirm information about the location of that soil sample quickly and accurately. We saw how this application works, practiced using this application to collect soil data, are learning how to see that data as it is collected, and hope to teach our classmates at school to do so soon.

What Have We Learned About Science?

By Sokona Mangane (Uncommon Collegiate Charter High School) and Curtis Paige (Uncommon Preparatory Charter High School)

When we first came to Columbia University and Lamont-Doherty Earth Observatory, we were discussing why lead in the soil was a problem and what factors made lead contamination happen. We had to ask ourselves questions to help find what was wrong, and although it seemed simple, it became complicated as there were many other factors that could change your answer.

This really changed how we thought about science and data, and how much other scientists must interpret data. For example, why were we studying lead in the soil in the first place? Until we came here, we didn’t fully know lead was dangerous and that it affects our bodies. We looked at the context of the situation and then asked ourselves questions like what does it mean to be safe? To have no lead in our bodies would be perfect—however, even in a non-contaminated environment, there’s some lead, and we are exposed to it. Then we started asking things like what does it mean to be safe enough? We needed the concentration of blood in our bodies to be less than a certain number to be healthy, but what that safe number is depends on who is looking. We had to measure soil concentrations of lead, since more lead in soil we live around could mean more lead in our bodies. However, looking at data suggests that the concentration depends on the different locations we analyze and that there is not a definitive answer about how much lead is in the city.

We couldn’t just jump straight into doing the sampling, as we had to think about what are the variables that affect lead concentrations in soil, and what are we looking for. We could not have done the experiment without thinking about the context first. We learned how to interpret data on graphs and what that meant in terms of our experiment.

Based on initial investigations, we identified the independent variables that affected lead levels, such as the location, the soil depth, the type of soil. This taught us what to measure and to record specific things such as location, depth and the time of the collection. That way we had everything we needed to know that can help us understand our results. Working with data in spreadsheets taught us how important it is to enter data correctly, and how to use categories of samples to make groups that are similar and easier to compare. For example, we needed to analyze surface soils differently than soils collected deeper in the soil at the same location, because they had very different concentrations. Every specific unit had to be calculated so there would be no errors in the graphing. This showed us the importance of categorizing in science. Through our results, we’ve also discovered that the soil samples contained potassium, nickel, zinc, barium, and many other elements, but we do not know much about them. We do know that they also have a story.

We are trying to do much more than make a map of lead concentrations in the city’s soil. Most importantly, we needed to make certain predictions and set measurements for what level of lead concentrations were dangerous and what were less threatening, and to think about how we can solve problems in places with too much lead. To do so, we had to think of what could’ve caused the lead buildup. Things we have considered so far: the buildings’ ages, amount of garbage burning, numbers of unclean water pipes, and numerous other factors. Blood lead levels over two micrograms of lead per deciliter of blood is considered dangerous to the human body, and a soil concentration over 400 parts per million of lead is considered by the EPA to be dangerous in children’s play areas. Unfortunately, lead concentrations are often higher, and are limitless and random when analyzed.

We are beginning to think of solutions for the problem of lead in soils. We could place new soil over the contaminated soil, give medication to people with lead poisoning, or dig out those soils with high lead concentrations to prevent future exposure. To do so, we need to know where soils are most contaminated. And now that we know that even something as simple as a map is very hard to make because concentrations change so much from place to place, we have also learned we will need a lot of help to make these changes happen.