A new study released in the September issue of the Journal of Contaminant Hydrology suggests that fuel droplets spilled at gas stations — which occur frequently with fill-ups — could cumulatively be causing long-term environmental damage to soil and groundwater in residential areas in close proximity to the stations.

Most studies have focused on large-scale leaks, such as those from underground storage tanks, rather than the environmental effects of routine gasoline leaks. However, Johns Hopkins Bloomberg School of Public Health researchers developed a mathematical model and conducted experiments suggesting these small spills may be a larger issue than previously thought.

According to lead researcher Markus Hilpert, over the lifespan of a gas station concrete pads underneath the pumps can accumulate significant amounts of gasoline, which can eventually penetrate the concrete and escape into underlying soil and groundwater, potentially affecting the health of those who use wells as a water source. Conservatively, the researchers estimate, roughly 1,500 L (nearly 400 gal) of gasoline are spilled at a typical gas station each decade. Researchers emphasize the importance of preventing runoff from washing gasoline off the concrete pads underneath the pumps.

Research suggests that even small gasoline spills can have a lasting effect. Stormwater runoff that picks up gasoline can contain harmful chemicals including the known human carcinogen benzene. That stormwater can then infiltrate adjacent soil or flow into local waterbodies through drainage systems.