According to the new research, up to 16% of the oil and gas wells that use hydraulic fracturing, or fracking, spill oil every year.
The study found that over the 10-year period between 2005 and 2014, there had been 6,600 spills that occurred in four US states of New Mexico, Colorado, North Dakota and Pennsylvania. The worst case was reported in North Dakota, where 67% of the spills were recorded, totalling 4,453 reported incidents.
The number of spills recorded is partially a reflection of the reporting requirements set by each state, for example in North Dakota reporting of smaller spills (42 gallons or more) is required, while Colorado and New Mexico the volume of the reportable spill is much larger (210 gallons or more).
The largest spill involved 100,000 litres of fluid released in a single leak. Most spills occurred within the first year of operation, with half of the incidents reported relating to storage and movement of fluids via pipelines. Dr Lauren Patterson from Duke University said: "Equipment failure was the greatest factor, the loading and unloading of trucks with material had a lot more human error than other places."
One of the authors of the paper, Kate Konschnik, said: "Analyses like this one are so important, to define and mitigate risk to water supplies and human health."
