April 18 (Reuters) - A Michigan regulator said this week

it is seeking public comment on a proposed permit that would

allow Marathon Petroleum ( MPC ) to boost crude throughput at

its Detroit refinery.

Marathon filed an application with the state in March to run

its 140,000 barrel per day refinery continuously at full

capacity by removing monthly and annual throughput limits. The

plan is opposed by local environmental groups because increasing

throughput increases refinery pollution.

The refinery's current permit caps the facility's capacity

at 140,000 barrels per day (bpd) on an annual average.

Marathon currently relies on periods of shutdown or reduced

production to meet the annual average limit, a spokesperson for

the Michigan Department of Environment, Great Lakes, and Energy

said.

Marathon declined to comment on whether it plans to

boost throughput beyond 140,000 bpd.

The Detroit refinery emits less pollutants than its current

permit allows, according to Marathon and regulators.

The facility is located in Wayne County, Michigan, an area

with significant industry presence that is out of compliance

with national standards for sulfur dioxide emissions.

To offset pollution increases, Marathon has proposed several

projects including upgrading process heaters to phase out the

crude flare.

Marathon has violated air quality rules and regulations

in the past, but that cannot prevent Marathon from seeking this

permit, regulators said.

The company lost an appeal in 2022 to be exempt from a rule

requiring it to enclose petroleum coke at the Detroit refinery

in order to prevent dust from being released.

A public hearing on the proposed permit is scheduled for May

22.