Dec 2, 2010 11:17 GMT  ·  By
PAH compounds derived from coal-tar sealants contaminate US lakes, threatening humans and marine species alike
   PAH compounds derived from coal-tar sealants contaminate US lakes, threatening humans and marine species alike

Experts with the United States Geological Survey (USGS) announce that they were able to discover the main source of polycyclic aromatic hydrocarbons (PAH) in the nation's lakes. Some of these compounds are believed to be carcinogens when in the human body.

The team analyzed samples collected from about 40 urban lakes throughout the country, and determined that the largest PAH source out there is a pavement sealant commonly used when constructing roads and highways.

The coal-tar-based chemical can apparently degrade to form PAH, which then seep through the ground into the water below, and eventually gets carried away with the flow.

Past studies have designated the aromatic hydrocarbons as a major source of environmental health concern, after scientists drew attention to the fact that some compounds in this group can cause cancer in people exposed to them.

The situation is made even worse by the fact that PAH concentrations in US urban lakes has been increasing steadily for the past decades, due to an increase in the number of construction projects being done, that need the sealant.

Fish and other aquatic species are also adversely affected by these chemicals, and so people can suffer their effects by either direct exposure or by consuming tainted fish products.

The new report, which is published in the latest issue of the journal Science of the Total Environment, shows that the USGS experts looked at several sources of PAH, in lakes located from Alaska to Florida.

The group says that the coal-tar-based pavement sealant came in first in this top. The shiny substance is used to cover common structures such as driveways, playgrounds and parking lots, to name but a few.

“These findings represent a significant advance in our understanding of the sources of these contaminants in streams and lakes,” explains Peter Van Metre, a USGS scientist that was a part of the research team.

“Identifying where contaminants are coming from is the first step in designing effective management strategies,” he goes on to say,

Chemical analysis of coal-tar has also revealed that the substance is made up of up to 50 percent PAH, whereas vehicle emissions, used motor oil, and tire particle – the other potential sources – only contain small amounts of compounds.