A county board in central California approved the expansion of the largest toxic-waste dump in the West, despite concerns about an increase in birth defects in a nearby farming town.

The Kings County Board of Supervisors on Tuesday upheld an earlier decision to allow Chemical Waste Management to expand its 1,600-acre facility near Kettleman City in the San Joaquin Valley.

The proposal still needs state and federal approval.

Community members in the largely Spanish-speaking town about three hours north of Los Angeles urged the board to reject the expansion after discovering an alarming increase in birth defects and infant deaths.

The dump's owners say there's no evidence linking the facility to the birth defects.

"I think the board vote today shows that they feel like the facility is safe and has been thoroughly reviewed throughout this long process," said Katherine Cole, spokeswoman for Chemical Waste Management.

Environmental activists and residents in the town of 1,500 called the vote disappointing.

The board said the county and state have the authority to revoke the permits if a link is shown between the birth defects and the waste site. The board previously asked the state to conduct a health investigation,

"That's ridiculous," said Maricela Mares-Alatorre, who heads the group People for Clean Air and Water. "That's like that expression closing the barn door after the horse has been let out. The investigation could take six months to two years."

About 400 truckloads of waste are hauled to the dump each day. In 2007, the last year for which complete statistics were available, that totaled more than 3 million pounds of lead compounds, nearly 2 million pounds of asbestos and more than 118,000 pounds of arsenic, according to the Environmental Protection Agency. It's the state's only facility that accepts cancer-causing PCBs.

Most of the waste comes from California, with smaller amounts from other states and even Mexico.

Of 20 children known to have been born in Kettleman City between September 2007 and November 2008, five had a cleft in their palate or lips, according to a health survey by activists. Three of those children have since died.

Statewide, clefts of the lip or palate routinely occur in fewer than one in 800 births, according to California health statistics.

Along with those health problems, activists point to the high asthma and cancer rates in the community.