Diversified miner BHP says poor air quality as a result of bushfires in Australia have weighed on coal output in its half-year to end-December, though it has kept its full-year guidance unchanged.

Production at New South Wales Energy Coal fell 11% during the period, with the company saying if air quality continued to deteriorate its operations could be constrained further.

The company has kept its guidance for its financial year unchanged at 15-million to 17-million tons.

Iron-ore production increased 2% during the period, with the company keeping its guidance unchanged, while copper production increased 7% year on year.

BHP CEO Mike Henry, who assumed his position at the beginning of 2020, said the company remained on track to deliver slightly higher production in its 2020 year compared to the prior period.

“We delivered solid operational performances across the portfolio in the first half of the 2020 financial year, offsetting the expected impacts of planned maintenance and natural field decline,” said Henry.