Thirteen states sue EPA over soot

Thirteen states filed in the U.S. Court of Appeals for the District of Columbia Circuit, asserting that the EPA ignored the advice of its own scientists. They recommended that it should lower the acceptable level for airborne soot -- known as fine particulate matter -- to 13 or 14 micrograms per cubic meter of air from the 15-microgram level that took effect on Monday.

Soot from diesel engines has been discussed in the recent past.