There are more than 100,000 gas stations in the United States which fill cars up with 365 million gallons of gasoline per day. With all the back and forth of the gas nozzle between cars and pumps, some gasoline inevitably ends up on the pavement.
A new study by scientists from Johns Hopkins Bloomberg School of Public Health found that these small spills add up and may cause public health risks in communities living near gas stations. Most studies on oil spills focus on major events like Deepwater Horizon. This is the first study to really look at smaller spills.
"Gasoline mixtures typically contain harmful or potentially harmful chemicals," said Dr. Markus Hilpert, one of the lead authors of the study. "Currently, a gasoline mixture contains about 0.6 volume percent of benzene, a chemical, which is known to be carcinogenic to humans. There are also other chemicals that are toxic or suspected to be carcinogenic. The problem is that relatively small concentrations of these chemicals can cause adverse health effects."
Though some spilled gasoline evaporates, Hilpert's study shows that a significant amount seeps into the concrete and can contaminate soil and groundwater nearby. He and his colleague calculated that every year, spills at a single gas station can amount to 1,500 gallons - and that's a conservative estimate.
The gasoline that doesn't evaporate or get sucked into the ground can be washed into waterways by rain. This is a major concern - and not just in gas stations.
"Urban runoff is that black strip down the middle of the highway. When it rains, it runs off to find its way to a waterway," said Christopher Reddy from the Woods Hole Oceanographic Institution who has studied spills like Deepwater Horizon. "Urban runoff is the largest source of oil pollution to the coastal environment."
The good news is that leaks at gas stations can be easily fixed. If gas stations keep their pavement well maintained - without cracks - the amount of gasoline that gets through the pavement could be diminished. Nozzles that catch drips could also be developed.
There are free solutions too - like careful filling that doesn't drip or overfill the tank.
"One of the things about studying environmental chemistry is that things are not easily solved and that's often frustrating," added Reddy. "In this case, a little awareness could probably reduce the load very quickly and very significantly at a low cost."