BEIJING — One of Beijing's worst rounds of air pollution kept schoolchildren indoors and sent coughing residents to hospitals, but this time something was different about the murky haze: the government's transparency in talking about it.

While welcomed by residents and environmentalists, Beijing's new openness about smog also put more pressure on the government to address underlying causes, including a lag in efforts to expand Western-style emissions limits to all of the vehicles in Beijing's notoriously thick traffic.

"Really awful. Extremely awful," Beijing office worker Cindy Lu said of Monday's haze as she walked along a downtown sidewalk. But she added: "Now that we have better information, we know how bad things really are and can protect ourselves and decide whether we want to go out."

"Before, you just saw the air was bad but didn't know how bad it really was," she said.

Even state-run media gave the smog remarkably critical and prominent play. "More suffocating than the haze is the weakness in response," read the headline of a front-page commentary by the Communist Party-run China Youth Daily.