Hawaii’s Department of Health has been ordered by the federal government to consider whether plastic is polluting the state’s water.

DOH failed to evaluate data and information related to plastics when compiling its list of impaired waters in 2018, according to a U.S. Environmental Protection Agency letter sent to DOH director Bruce Anderson on Monday.

Under the Clean Water Act, states must consider all relevant data and compile a list of waters that fail to meet water quality standards every two years. In 2015 the Center for Biological Diversity submitted studies to DOH finding that 17 bodies of water in the state were negatively impacted by plastic pollution.

Maxx Phillips, Hawaii director for the Center for Biological Diversity, said DOH didn’t consider that research when compiling the state’s 2018 list, and sued the EPA in February for approving the list.

The EPA has now said DOH did not consider data on plastic pollution when submitting its 2018 list, and is giving the agency two months to resubmit its list.

“What’s really exciting about the EPA letter to DOH is that it makes clear that states have to consider plastic pollution when evaluating water quality,” said Phillips, whose lawsuit is now on hold.

Keith Kawaoka, state deputy director of environmental health, said in an email that DOH was prioritizing EPA’s request amid the department’s response to the COVID-19 pandemic.

“Maintaining water quality standards is important to the Department of Health and Hawaii residents, and we will review and re-evaluate existing data and information relating specifically to plastics in Hawaii’s waterway,” he said.

Hundreds of tons of plastic wash up on Hawaii’s beaches every year, and the amount of microplastic — plastic shards smaller than a pencil eraser — is expected to double by 2030.

“Once something is officially deemed as a pollutant the state has to take steps to remedy the pollution,” said Phillips. But it’s unclear how the state could evaluate the water’s cleanliness.

Unlike lead or bacteria, there’s no federal regulation on the amount of microplastics allowed in the water, and testing for microplastics is more time intensive and expensive than testing for most other contaminants.

Phillips sees the EPA’s decision as a step toward remedying the information gap.

“This is not just for Hawaii but for all our water in the country,” she said.