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BOULDER, Colo. – In an effort to save the trees in western Boulder County from a scourge of hungry mountain pine beetles in the mid-1970s, foresters doused tens of thousands of trees with a potent, cancer-causing pesticide.

They thought it was safe.

“We would literally drench trees until it ran off the branches,” John Oppenlander, who worked for Roosevelt National Forest, told the Camera in 1984, a year after the pesticide – called ethylene dibromide, or EDB – was banned by the Environmental Protection Agency.

“If we had known then what we know now, we would have been the first to abandon it,” added Colorado state forester John Laut.

In recent years, the pine beetles have struck again, and thousands of trees are being sprayed in Boulder County again – this time with a pesticide called carbaryl – causing concern among some mountain residents that today’s foresters will also realize too late that a beetle-killing pesticide may be hurting people.

Using carbaryl is relatively expensive, and it has to be applied to each tree individually, making it impractical to spray entire forests. So ski resorts, the Forest Service, the park service and private landowners have all started spraying their “high-value” trees – the ones surrounding buildings, lining ski slopes, and shading campsites and yards. For the treatments to work, the same trees will have to be sprayed every summer until the pine beetle epidemic ends, which could take as long as 10 years.

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