LOS ANGELES (AP) — California cannot account for 174,000 tons of lead and other hazardous materials shipped for disposal in the last five years, but state regulators say public health is not threatened, a newspaper reported Sunday.

The Los Angeles Times reported (http://lat.ms/HTqQES) that a state database shows the toxic chemicals and cancer-causing metals were shipped but gives no indication that they arrived at their intended destinations — many of which are out of state.

California officials told the newspaper they are confident that the missing shipments found their way to disposal sites but acknowledge they can’t be sure.

“We don’t know,” said Debbie Raphael, director of the state Department of Toxic Substances Control, which has a $189 million budget and about 900 employees. “It’s a question mark.”

Raphael and other officials told the Times they are concerned by gaps in the tracking system. However, they insisted they would know through public complaints or reports from local officials if a significant amount of toxic waste had been dumped illegally.

“I do not believe that Californians are at risk,” Raphael said.

The Times said the lost loads include more than 20,000 tons of lead, 520 tons of the carcinogen benzene and 355 tons of methyl ethyl ketone, a flammable solvent.

In most cases, no one investigates what happened to the missing waste.

California’s rules on handling hazardous waste are among the strictest in the nation. From dry cleaners to heavy manufacturers, businesses that generate waste must report every load they ship. Disposal and treatment facilities must record the waste’s safe arrival. And the state agency is required to track every ton to make sure it isn’t dumped illegally along the way.

But the newspaper reported there are holes in the department’s database and they lose track of large quantities of toxic chemicals and cancer-causing metals. Regulators make only limited use of what information is available, and the system does not automatically flag potential problems, the Times found.

It can be difficult to link illnesses to hazardous waste because those who have been exposed might not know it. Also, symptoms can take years to develop and can be ascribed to other causes.

But even a small amount of errant waste can create “a very big public health impact,” said W. Bowman Cutter, an associate professor in the environmental analysis program at Pomona College who has studied the state’s hazardous-waste system.

The Times said California’s hazardous-waste regulators rely on pen, paper and the mail to receive reports of waste shipments from businesses, a system that can be prone to errors and information gaps.