An uncovered, loaded 80-wagon train is estimated to emit an average 685.6 grams of dust per kilometre. That means an estimated 37 tonnes of coal dust would be emitted per kilometre in Newcastle every year along some sections of track by 2022.

“The potential for a doubling of the coal freight task travelling through the Hunter Valley spells disaster for the health of residents,” Faehrmann said.

“This issue has been going on for more than 20 years and it is time the minister took control of the situation.

"Covering the railway wagons that carry coal from the Hunter Valley to the Port of Newcastle is a simple, obvious measure to protect people's health. I am writing to the minister to ask her to move on this issue without delay.

"The minister claims she is undertaking an investigation into this. What investigation is needed to know that coal train movements are increasing, that they generate an enormous amount of coal dust and that the fine particles in coal dust have been shown to cause serious health impacts?”

Faehrmann said it was unacceptable the Environmental Protection Agency had been sitting back and waiting for industry to develop a work plan for coal dust.

“The EPA needs to issue a simple directive for coal wagons to be covered and that should happen immediately," she said.

"Claims by some that a move to force coal companies to cover wagons would impact on their profitability smacks of disregard for the thousands of people whose health is being put at risk.”

NSW Minerals Council chief executive Stephen Galilee reportedly said the council continued to work with the Upper Hunter community on the issue of coal-train dust.

‘‘Coal operators are working closely with them to understand the nature of the issue in NSW, so that the most appropriate actions can be taken,’’ he told the Newcastle Herald.