Environmental advocates will try to persuade the Utah Supreme Court Wednesday that the state's approval of an oil refinery expansion would add to air quality woes in northern Utah, parts of which suffer from some of the nation's worst air in winter.

The legal battle marks the latest illustration of the intense scrutiny air quality issues receive in the greater Salt Lake region.

The air problems in Utah's urban corridor during the winter result from weather and geography with cold, stagnant air often settling in the bowl-shaped mountain basins, trapping tailpipe and other emissions that have no way of escaping.

Doctors warn that breathing the polluted air can cause lung problems and other health concerns. State officials ban wood burning on many days, and they constantly plead with residents to carpool and take other measures to cut down on pollution.

At issue in this case is the expanded scope of work at the Tesoro oil refinery just north of Salt Lake City.

State officials gave approval in 2012 for Tesoro to increase operations at the facility, but a coalition of environmental groups sued.

State regulators stand behind the decision, arguing in court documents that Tesoro met all state and federal requirements. But the coalition — which includes Western Resource Advocates, Utah Physicians for a Healthy Environment and the Sierra Club in Utah — argue that the state should require stricter emissions controls.

The particles emitted from refineries and other pollution penetrate people's bodies, making it difficult to for the lungs to work and causing a host of health problems, said Joro Walker, senior attorney for Western Resource Advocates in Utah.