For more than a half-century, there has been a widespread and largely unmonitored practice of spreading wastewater from oil and conventional gas drilling, by the millions of gallons, onto dirt and gravel roads in rural Pennsylvania.

The practice has found itself awash in controversy in recent years as a number of scientific studies have found that the wastewater brine contains unhealthy levels of radiation from naturally occurring radium as well as toxic chemicals such as benzene, iron, manganese, strontium, barium, aluminum, zinc, lithium, copper and lead.

In addition to being a hazard to human health, runoff of the wastewater can harm nearby streams, killing aquatic life and over time making streams too salty for trout, the studies found.

A recent study by Penn State found the brine is no more effective than plain water for dust control and in some cases can damage roads.

The oil and gas industry has fought back, saying the brine is a free and effective tool for municipalities and does not cause any harm to people or the environment when spread in the right places and the right times.