A number of counties across the US are being considered for an air-pollution zone that could subject them to strict auto-emission controls.

Areas lying just outside urban locations that are already bound by legislation are being considered for further controls according to state departments.

In St Louis, for example, the counties of St. Francois, Ste. Genevieve, Warren, Lincoln, and Washington are all being considered for inclusion in a wider St. Louis metropolitan air pollution district.

The Missouri Department of Natural Resources met with representatives of the counties yesterday (April 28th) to determine the outcome, with a number of state agencies across the country following a similar pattern.

A tougher round of national air pollution standards, due as early as 2007, would include widening the geographical reach of urban air pollution controls on vehicles and industry.