With mud crab prices soaring to $100 per kilogram over Christmas, and still sitting on nearly $40 per kilogram, his regular crabbing sessions are "like an easy luxury" for the common man and woman, he said.

But he might move from his favourite crabbing spot to somewhere beyond Lake Macquarie after a report on Monday revealed a government agency risk assessment recommended people not eat mud crabs on a weekly basis.

"It's definitely put me off," said Mr Miller, 47.

A NSW Office of Environment and Heritage risk assessment of Lake Macquarie pollution levels recommended against weekly mud crab eating because any level of consumption could result in exposure to cadmium, a heavy metal linked to kidney and liver failure.

The consumption of most seafood from the lake should also be restricted, particularly for children, because of high levels of a second heavy metal, selenium, the OEH risk assessment concluded.

Selenium is linked to liver, kidney and heart problems.

While a health risk assessment of Lake Macquarie in 2003 resulted in a warning to recreational fishers to restrict consumption of seafood caught in the lake system - a warning that remains in place today - the focus of environmental concern has shifted from the lake's north to the south, Hunter Community Environment Centre said.

The centre commissioned a report, Out of the Ashes, released on Monday, which revealed the Office of Environment and Heritage's updated warnings about mud crab consumption because of cadmium levels, and recommended much stronger regulation of more than 60 million tonnes of coal ash in unlined storage areas on the lake shore.

The coal ash is waste from ageing Vales Point and Eraring power stations, containing heavy metals the centre argues are making their way into the lake system and into the food chain.

The Out of the Ashes report used laboratory analysis of water samples from key lake locations and reviewed environmental licences to conclude both power stations were discharging aluminium, iron and manganese above recommended concentrations for recreational marine waters, as well as arsenic, lead, copper, nickel and zinc above Australia and New Zealand Environment Conservation Council guidelines.

"What we found is that environment protection licences for the power stations do not set limits for heavy metals at three of the four discharge points where our water sampling found elevated concentrations of metals," the report found.

"Indeed, neither power station is required to monitor or limit the concentrations of all the heavy metals we found being discharged."

It found sediment in the creek receiving the Eraring ash dam overflow was found to have a selenium concentration of 110 parts per million, or more than 55 times the level recommended to protective sensitive fish and birds.

The Vales Point cooling water outfall was found to have selenium concentrations 2.5 times the level recommended to protect sensitive fish and aquatic birds.

The report noted that both the NSW Environment Protection Authority and power station operators would consider the concentrations of heavy metals in water sampled for the report was "manageable".

But the report and Hunter Environment Centre expressed concern at the high volumes of water discharged from power stations into the lake and the specific characteristics of the system.

Eraring's cooling water outfall is licensed to discharge 11,000 megalitres of water a day, and Vales Point 6500 megalitres per day, with no limits on the amount of selenium discharges.

The report described the estimated 160 kilograms of selenium entering the lake system each year from the power station outfalls were "very high loads into a lake with a 1 per cent tidal exchange, and an area around Vales Point power station that is only flushed by tides every 500 days".

The report called for an urgent focus on the environmental impacts of coal ash which was excluded from a number of hazardous waste and pollution laws in the past to encourage its re-use in the construction industry.

Ash from coal-fired power stations makes up 20 per cent of Australia's total waste stream, but less than 20 per cent is being beneficially re-used in mine site rehabilitation or fixed in concrete. Coal ash is instead being used in agricultural soil, fertilisers and potting mixes which pose risks of contaminating groundwater or entering the food chain, the Hunter Environment Centre report said.

"Regulatory amendments are required that put the financial burden for safe disposal of coal ash back onto the power station operators," Out of the Ashes report author Paul Winn said.

"Incentives are required that encourage environmentally responsible coal ash re-use to remove a key source of heavy metal contamination from the shores of Lake Macquarie, reduce a key source of greenhouse gas pollution, and encourage new on-site enterprises that will provide new jobs for displaced workers when these aging facilities are finally decommissioned.”

While concerns about the health of Lake Macquarie had historically been on the north because of discharges from the former Pasminco smelter, the focus had now shifted to the impacts of power stations and their coal ash disposal areas in the south, Hunter Environment Centre said.

Mr Miller criticised the EPA for failing to release detail of testing across the lake in 2018 which found cadmium levels in crabs in the north and south-west parts of the lake system were high, and the OEH risk assessment recommendation that no mud crabs be eaten on a weekly basis.

The EPA said in January that dietary advice for cadmium "remains consistent and people can safely consume six servings per month of crab meat".

"They should be putting out much more information to make it quite clear to people what's safe and what's not," Mr Miller said.

In a statement on Monday the EPA said its advice for the consumption of "crab meat" released in January was based on using recommendations for blue swimmer crab rather than mud crab.

NSW Health and NSW Food Authority, in consultation with the Department of Primary Industry Fisheries, agreed on the advice because of limited numbers of mud crab caught during the testing program which indicated their low abundance in Lake Macquarie, the EPA said.

Mud crabs represent 1 per cent of the total catch by anglers, while blue swimmer crab is about 12 per cent of the total catch.

"NSW Health and the NSW Food Authority advised that children could safely consume up to 3.3 serves of blue swimmer crab per month and an adult could safely consume up to 6.2 serves per month," the EPA said.

"These calculations by NSW Health and the NSW Food Authority were based on weekly raw data provided by the Office of Environment and Heritage."

The EPA would not comment on the Out of the Ashes report because it had not yet reviewed it.