The fate of thousands of Queensland coal miners and their communities is in limbo after mining giant Anglo American rejected a $74 billion takeover bid by BHP.

The offer was BHP's third attempt to acquire the rival global mining company, whose board granted it a one-week extension to come back with a better offer.

"The board considered BHP's latest proposal carefully, concluded it does not meet expectations of value delivered to Anglo American's shareholders, and has unanimously rejected it," a statement from Anglo American said.

Anglo American owns five coal mines in Queensland's Bowen Basin — Moranbah North, Capcoal, Dawson, Aquila and Grosvenor.

The mines employ more than 5,000 workers, the Mining and Energy Union said.

Anglo American provides almost 850 houses and unit complexes in the Isaac Region.

In the town of Middlemount, the company subsidises businesses in the local shopping centre and gives those tenants free housing.

It also provides the town's water, local doctor, childcare, and before and after school care.

The ABC contacted multiple business operators in Middlemount about the takeover bid, but they all declined to comment.

A community 'unnerved'

Isaac mayor Kelly Vea Vea said Middlemount locals would be feeling "unnerved" by the lack of certainty.

"Their town was built to service these mining assets that are currently up for grabs," Cr Vea Vea said.

"The liveability of their community has been widely supported by Anglo American to this date, and in this current landscape, it's hard to imagine that another company will swoop in and continue business as usual in that regard."

Earlier this month, Anglo American announced it would sell off its five Queensland coal mines after rejecting BHP's second takeover bid.

Cr Vea Vea said Anglo American had promised to work with the council to provide a "responsible transition" of assets back to the community over the next 18 months to two years.

"This is a really big process, it's an expensive process, and it takes a lot of capacity," she said.

'You're not just buying a mine'

BHP has until May 29 to submit its final takeover proposal to Anglo American.

Mr Smyth said the union had concerns about the company's safety record.

"I'll be perfectly blunt, BHP isn't the preferred employer of choice – they have a chequered history," he said.

Mr Smyth said he hoped any sale of the Queensland mines would safeguard the employment of the thousands of mine workers.

"Our concern would be, depending on the buyer, if they come in, they suddenly make a decision to offload or restructure … which will then be disastrous for workers, communities and certainly Queensland," he said.