According to the organisation, coal from the Powder River Basin burns in 235 power plants in 35 states - and the ramifications of pollution from that coal are not considered when leases are granted.

The basin, in Wyoming’s northeast, contains the largest coal reserves in the US suitable for mining.

The country has depended on coal for electricity for decades, but coal demand declined in recent years.

The report, titled Dirty Fuels, Clean Futures, called for a time out for coal leasing on federal public lands.

It made the case that existing leases can more than meet energy demand for the next decade.

Arch Coal also received a dishonourable mention in the report, labelled as one of the largest polluting culprits in the US.

Despite the push to send Wyoming coal overseas to keep production strong while domestic demand wains, plans have not been realised because of local objections to more rail traffic and to building new ports in Oregon and Washington.

There's no doubt Wyoming is dependent on coal for its livelihood, which will have to be considered as the US’s environmental economy changes.