Officials in Louisville have decided not to issue mandatory clean air regulations that would have threatened the area's bourbon makers.

Bourbon produces ethanol as it matures in charred oak casks. The Environmental Protection Agency (EPA) has classified these fumes as volatile organic compounds or VOC nad, as such, fall under the Clean Air Act.

Environmentalists had urged the Louisville Metro Air Pollution Control District to require local industries to cut emissions by 3 per cent this summer to coincide with peak smog season.

Bourbon makers complained that they could not regulate the production of gases during the ageing process, which takes place in warehouses. Some bourbon distillers even complained that strict enforcement of EPA rules would force them to leave the state.

Environmental officials said industries, including the bourbon makers, would have had other options including "emissions trading" or making donations to a clean air trust fund. Louisville officials sided with industry groups by choosing to endorse voluntary emissions reductions for this summer.