Up to 16% of hydraulically fractured oil and gas wells spill liquids every year, according to new research from US scientists.
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They found that there had been 6,600 releases from these fracked wells over a ten-year period in four states.
The biggest problems were reported in oil-rich North Dakota where 67% of the spills were recorded.
The largest spill recorded involved 100,000 litres of fluid with most related to storing and moving liquids.