State experts have given their backing to US federal rules aimed at bringing down the level of emissions, after the latest round of figures showed some counties are continuing to emit high levels of pollution.

The US Environmental Protection Agency (EPA) announced yesterday that a number of counties in states across the US had failed to meet new standards for air pollution - 243 in total.

The states could face penalties if they fail to tackle the issue, but state experts insist that wider federal rules are perfectly adequate, and argue that individual state performance is irrelevant in the face of national legislation.

Ron Gore, air director for the Alabama Department of Environmental Management, pointed to the EPA rules governing automotive emissions - noting that 2004 cars have tailpipe emissions 10 times cleaner than 2003 models.

"You don't need to look in your two- or three-county area for pollution reduction," he told the Birmingham News.

Kay Prince, chief of the air planning branch for the EPA in Atlanta, agreed, noting that the federal rules and state initiatives "work together to bring clean air".

Indeed, the number of states that failed the emission test was actually held up as an encouraging sign - down about one-third from initial projections. In 28 states, every county met the rules.