The U.S. Senate has approved legislation that included an amendment by Sen. Tom Carper (D-Del) directing the U.S. Environmental Protection Agency to study the environmental impact of black carbon, and to find the most cost-effective ways to reduce its emissions to improve public health and reduce global warming.

Carper’s amendment, similar to his original bipartisan bill S. 849, was included in the Senate Interior Appropriations Bill (H.R. 2996), which passed the Senate by a vote of 77-21 late last week.

The amendment directs the EPA to do a four-phase study that identifies global and domestic black carbon sources and cost-effective reduction technologies; the public health, economic and climate impacts of black carbon; opportunities for current and possible international funding for mitigation and opportunities for future research and development.

"We must act to reduce black carbon - a dangerous pollutant emitted by old, dirty diesel engines like those in some school buses and thought to be the second largest contributor to global warming after carbon dioxide," Carper said in a prepared statement.

While black carbon in the United States comes mainly from old, dirty diesel engines, internationally, black carbon comes from old cook stoves, inefficient industrial process and from dirty diesel engines.

The black carbon study will be due to the Congress one year after this legislation is enacted into law later this year. A final version of the Interior appropriations bill will be sent to President Obama later this year, once it has been reconciled with a House version of the bill.