The Department of Water and Environmental Regulation (DWER) began investigating complaints of red, black and pink dust from residents and businesses around Geraldton earlier this year, with complaints concentrated near the port.
Iron ore is the port's main export. Chinese-owned Karara Mining ships magnetite concentrate, while WA-based Fenix Resources exports hematite.
In a statement released today, DWER said its investigation of the black dust complaints found magnetite dust emitted from "certain industrial activities" was a contributor to overall dust pollution around the city.
"As a result of this investigation, the department is engaging with Karara Mining Limited and the Mid West Ports Authority in relation to potential licence amendments to deliver improved dust management outcomes," a DWER spokesperson said.
DWER did not disclose the specific changes it would ask the port and miner to make.
Residents and community leaders have consistently called for Karara's iron ore wagons to be fully covered. In a region known for strong southerly winds, the train route passes schools, hospitals and homes. Residents have previously told the ABC that black dust coats their homes and businesses, costing thousands of dollars to clean.
DWER said its investigation into separate complaints about pink and red dust was ongoing but nearing completion, with further technical analysis needed before conclusions could be reached.