SAN FRANCISCO — The nation’s largest baby food makers face a lawsuit by an environmental group aimed at forcing them to alert consumers that some products contains low amounts of lead.

The case scheduled for trial today will determine whether they should put warning labels on such products sold in California.

Gerber Products, Del Monte Foods, Beech-Nut Nutrition and many other makers of baby foods and juices are selling products containing lead at levels that require warning labels under California Proposition 65, the Environmental Law Foundation asserts in the suit filed in Alameda County Superior Court in Oakland.

Lawyers for the food companies say the U.S. Food and Drug Administration tested products targeted in the lawsuit, and decided levels were below the standards that require a warning.

But both sides in the case agree on one fact: baby foods containing carrots, peaches, pears and sweet potatoes have some lead. Also covered by the suit are grape juice and fruit cocktail.

Lead exposure can damage a child’s developing brain and lead to a lower IQ. Overall, lead poisoning in the U.S. has declined significantly as it was removed from paints and gasoline formulas.

Still, more than 500,000 U.S. children are believed to have lead poisoning, according to the Centers for Disease Control and Prevention.

Old paint, contaminated drinking water and soil tainted by old leaded gasoline are primary sources of lead exposure to children in the U.S., the CDC reported. Some specialists describe children as having lead poisoning only when at very high levels are present, but others use the term more broadly to describe any child with levels that can impact intelligence or cause other harm.

FDA tests on products named in the lawsuit found lead levels “below FDA’s current tolerable intake levels for lead.”

The companies argue the lead in fruit and vegetables used in the products is naturally occurring, which if the judge finds is true could exempt the companies from having to warn consumers.