By BLOOMBERG

BEIJING • Beijing’s air quality was the worst in 18 months yesterday, a possible result of more flexible emissions curbs for winter.

The economic slowdown may have been behind the decision to move away from the hard targets of last year, with the government trying to keep factories churning, according to some economists.

The concentration of PM2.5 particles — the most-hazardous, tiny particulate matter — soared to 328, according to data published by the US Embassy. The measure’s five-day average was 149, compared to 26 last year when the government’s environmental cleanup was in full swing.

The Environment Ministry said earlier this year that northern China’s industrial hub would adopt a more flexible programme for its output curbs this winter, eschewing blanket cuts and taking a differentiated approach to industries, including steel.

Worsening trade tensions and a slumping stock market have hurt confidence in the economic outlook, putting pressure on officials to do more to shore up growth.

“The downward pressure on the economy is rising,” said Yao Shaohua, an economist at ABCI Securities Co Ltd in Hong Kong. “Curbs on industrial production to crack down on pollution could have eased marginally compared to last year.”

Residents in Beijing wore masks to protect themselves from the toxic air yesterday, though authorities signalled the air would improve by today.