The New Haven Environmental Justice Network is trying to stop the Elm City’s second-largest hospital from continuing the use of No. 6 fuel, a heating oil that yields three times as much pollution as the fuel used by other hospitals in the area.

After filing an intervention in December to halt the approval of St. Raphael’s application to use No. 6 fuel for a recently installed boiler, group members — along with affiliate Connecticut Coalition for Environmental Justice — met with St. Raphael officials at a pretrial hearing Tuesday in Hartford. A public hearing date has been set for May 3 in New Haven.

Lynne Bonnett, chair of the New Haven Environmental Justice Network, said St. Raphael’s use of the oil is particularly problematic because the hospital is located in the middle of a residential neighborhood. Whenever air is stagnant in the vicinity of St. Raphael’s, the pollutants coming out of the smokestack infiltrate the Dwight neighborhood, Bonnett said. Pollutants from No. 6 fuel oil are also more harmful than those of No. 2 fuel, Connecticut Coalition for Environmental Justice President Mark Mitchell said.

“No. 6 fuel oil is what’s left over after they take every useful component out of the oil,” Mitchell said. “When they burn the oil, [the impurities] can get into the air and cause high particulate matter, which is associated with asthma and respiratory.”

St. Raphael’s spokesman Bill Brucker said the hospital has already reduced its pollutant output by 37 percent after switching to a grade of No. 6 fuel that has a lower sulfur content. Although other hospitals in the area use No. 2 fuel — including Yale-New Haven and Hartford — switching to No. 2 fuel would be fiscally problematic because St. Raphael’s financial resources are limited, Brucker said.

“The challenge is to balance being environmentally conscious and fiscally responsible,” Brucker said. “No. 2 fuel would require … retrofitting the boilers, but at this point we don’t have the financial resources to absorb that cost.”

But Mitchell said although St. Raphael’s fiscal solvency has varied from year to year, the corporation that manages the hospital consistently turns a profit of $5-8 million, enough to absorb the cost of switching over to No. 2 fuel.

Bonnett said St. Raphael’s situation is not unique and that the hospital should consider its effect on the local community more carefully.

“They are struggling, but other hospitals are struggling too, and they don’t pollute the neighborhood,” she said. “It’s a matter of priorities and what we can expect in the future.”

Bonnett said her environmental group would be willing to settle the case prior to the public hearing if ongoing private negotiations should result in a satisfactory agreement between the two parties.