Pollution controls for major coal-fired power stations in NSW are so weak that they are comparable to "fairly under-developed third world countries", a US energy expert says.

Dr Ron Sahu, a California-based air quality consultant, said the environment protection licences (EPLs) at the Mt Piper, Eraring and Vales Point plants were "very weak".

“It is inexplicable," said Dr Sahu, who has worked in Kenya, India, the US and China. "Your neighbouring drycleaner [in the US] would have a stronger licence, and I’m only half exaggerating.”

Pollution controls on Mt Piper and two other coal-fired power stations in NSW were akin to those you would find in a lesser developing nation, a US expert finds. Credit:Nick Moir

Dr Sahu was commissioned by Environmental Justice Australia to examine the three power plants, all of which will have the EPLs reviewed by the Environment Protection Authority by January 2019.