America is getting the lead out.
That's the word from the U.S. Geological Survey, which reports that the amount of lead in the nation's rivers and streams declined over a decade.The general reduction in lead levels is likely a result of reduced use of leaded gasoline, the recently published study said.
Survey scientists checked the water at some 300 locations across the country and found declines in lead at two-thirds of the stations - including significant drops at 30 percent of them, between 1974 and 1985.
"Although we have not completed intensive trend analyses on data collected since 1985, preliminary results indicate that the overall decline in lead concentrations has continued," said Richard B. Alexander in a statement.
Alexander and Richard A. Smith, hydrologists at the Survey's National Center in Reston, Va., compiled the report, which was published in the most recent edition of Water Resources Bulletin.
"This decline is certainly good news as far as the water environment is concerned," Alexander observed.
Lead is considered a hazard because, if ingested, it can cause brain damage and eventually even death.
The survey said increases in lead in stream water were found in a few locations, principally along the Texas gulf and Lower Mississippi Valley regions. None was in water that was used for drinking, however.
The increases were thought to be largely due to declines in the volume of water flowing in those areas in the last few years of the study. Declining water volumes tend to concentrate pollutants.
Assessing the effectiveness of pollution abatement efforts is often hard to do because of the lack of widespread, long-term measurements. The survey's water-quality measurements, which have been conducted since the early 1970s, are at least one way to do this, said Alexander.