The Geological Column

Sarah Ehlinger

At first glance, it seems like there are no fields more disparate than geology and public health. Images of dusty rocks sitting on shelves in dark museums don’t exactly bring to mind images of stethoscopes or Band-Aids. But if everything ultimately comes from the Earth, isn’t everything that harms or helps us related to geology? There are the obvious examples like catastrophic earthquakes, volcanoes and landslides that make people fear for their lives, but what about mercury in fish, PCBs in river sediments or lead in our front yards? The amount to which certain contaminants react with our Earth dictates how available they are to us humans.

If any of you have taken an intro environmental studies course, you are likely familiar with the issue of lead contamination in Appleton soils. Appleton struggles with what we call “legacy pollution,” or pollution caused by remnants of toxins in our environment from a few decades ago when humanity was so young and naïve. One main source of lead is an additive in paint, PbCO3. This is a dangerous or “bioavailable” form of lead because the molecule is easily broken apart by acid. Even rain is naturally acidic and can thus release both carbonate, which is not dangerous, and lead, which is a neurotoxin. Many Appleton houses were built before 1977, when leaded paint was outlawed in the U.S. It is important for geochemists — and their students — to study the soil in local yards to determine what types of soil are most contaminated and which areas around a house are most dangerous.

Another cause of legacy pollution was the use of leaded gasoline. After decades of leaded emissions reaching air and soil, many urban areas in the U.S. are now highly contaminated. Unfortunately, some countries still use leaded gasoline today. For example, Sierra Leone uses leaded gasoline and has issues with dense traffic. Over winter break, I analyzed the soil differences between Appleton and Sierra Leone. Soils in Sierra Leone do not have the types of minerals that bind to lead. Lead is trapped in Appleton soils and as such presents a risk to children playing on contaminated ground. Lead in Sierra Leone is likely washed away in heavy rainfalls.

So, next time you see a rock, a garden or a pile of dirt, think, ‘What is in there that makes my body work? What might we use that for in our daily lives?’ It might have more to do with your health than you think.