A review by the U.S. Environmental Protection Agency (EPA) has found that flares at refineries and chemical plants emit about four times more pollutants than previously reported.

The review was prompted by a 2013 lawsuit brought by the Environmental Integrity Project on behalf of Air Alliance Houston, Community In-Power and Development, the Louisiana Bucket Brigade, and Texas Environmental Justice Advocacy Services.

Under the terms of a consent decree, the EPA evaluated the emission factors for volatile organic compounds (VOCs) for flares, liquid storage tanks, and wastewater collection, treatment and storage systems.

As a result, the agency has drawn up a new formula for calculating the amount of pollutants released by flares. This is expected to provide more accurate estimates of carbon monoxide, nitrogen oxides and VOCs released by the flaring or burning of waste gases at those facilities, the Pittsburgh Post-Gazette reported.

However, the new formula does not apply to oil and gas wells and compressor stations that occasionally flare gases, or gas processing facilities that regularly flare, the newspaper noted.

The EPA also concluded that no revision is necessary to the VOC emission factors for tanks and wastewater treatment systems.

Commenting on the revised formula for flaring, Eric Schaeffer, executive director of the Environmental Integrity Project, said it shows that flares "deserve more attention from state and local regulators."

The previous EPA guidelines were based on data from nearly 30 years ago.

For industry, the good news is that reducing emissions from flares is cost-effective and fairly straightforward, said Sparsh Khandeshi, attorney for the Environmental Integrity Project. One option is to upgrade facilities so that they recycle more gas instead of burning it. "That saves the industry money, while also reducing air pollution that threatens people living downwind," Khandeshi said.