PITTSBURGH (AP) - A new scientific study on natural gas drilling and Pennsylvania waterways has found that old-fashioned erosion, not toxic chemical spills, appears to be more of a cause for concern.

The peer-reviewed study published Monday took a statewide look at surface water impacts from the drilling boom. It found some good news and some reasons for concern.

Lead author Sheila Olmstead says the research didn't find evidence of significant chemical spills from drill sites, but did note a five percent increase in suspended solids in downstream waterways. It also found a 10 percent increase in chloride levels downstream from plants that handle drilling wastewater.

Olmstead is with Resources for the Future, a Washington D.C. non-profit.

The study was published in the Proceedings of the National Academies of Sciences.