Baby food and packaged fruit contain lead levels that warrant a toxic warning label, an investigation by the Oakland-based Environmental Law Foundation found.

The foundation tested 1,500 samples of baby food, packaged fruit and juice, and found that many contain lead levels above the limit that requires warning labels under California Proposition 65, which mandates disclosure of toxic substances. Three quarters of baby foods tested contained lead, it discovered.

Its analysis, based on tests by UC Santa Cruz, a private laboratory, and records from the companies themselves, examined 146 brands of grape juice, packaged pears, peaches and fruit cocktail, and baby food containing carrots, peaches, pears and sweet potatoes.

The tests on those samples detected lead in amounts between 2 and 29 micrograms per serving – far above the .5 micrograms per serving limit that triggers the warning requirement, said James Wheaton, executive director of the foundation.

The organization filed suit in state Superior Court in Alameda, demanding that 16 companies post Prop. 65 warnings on the lead-tainted food. And they are releasing the list on their website as a print-at-home shopping guide for consumers.

Lead exposure at even low doses can cause brain damage, learning disabilities, lowered IQ and behavioral problems in children, along with health problems in pregnant women and adults.

While the levels identified in the study wouldn’t cause lead poisoning in a single serving, they could contribute to long-term accumulation of the toxic metal. Last year, the Centers for Disease Control and Prevention reduced by half the benchmark used to identify high levels of lead in the bloodstream, but scientists said there’s no known safe level.

Statistics from the San Diego County Lead Prevention Program show that more than three percent of children tested for lead had elevated lead levels in 2010. In previous years, more than four percent tested positive for lead.

“At that low level, we’re seeing real, significant damage to their brain, their IQ,” said Leticia Ayala, associate director for programs for the San Diego Environmental Health Coalition.

“What we really want is information in mom’s hands, so that they can make choices,” he said. “We don’t allow lead in paint. We don’t allow it in gasoline. Why are we allowing it in baby food?”