The Bay Area Air Quality Management District has withdrawn its Title V operating permit renewal for the Lehigh Southwest Cement Company.

The air district won’t submit a new permit to the U.S. Environmental Protection Agency until stricter EPA rules governing mercury and other toxic emissions take effect in the spring. However, the plant can continue to operate under its current permit indefinitely.

Opponents of the long-running cement plant and quarry, formerly Kaiser Permanente, have cited problems with the plant’s residual toxic emissions blowing into Los Altos Hills. Los Altos Hills resident Bill Almon, who founded the opposition group QuarryNo (quarryno.com), said his group recently conducted dust tests that measured arsenic levels 20 to 50 times higher than established state health levels. Arsenic is a poisonous element found naturally in minerals.

“The arsenic is in the limestone mined and is a common waste from mining,” Almon said. “It is toxic, particularly in the air when it swirls around the cars and trucks and becomes airborne.”

Lehigh’s Nick Rangel provided the company’s written response: “Arsenic levels at our site are consistent with naturally occurring levels in Santa Clara County” and are not harmful to humans.

In addition, air district officials see no health dangers from plant and quarry operations.