Maria de Los Angeles Prieto started noticing the changes in her son, Alfredo, in 2011, when he was 7 years old.

Alfredo has autism, which sometimes causes him to behave erratically. But the abrupt mood swings and sudden tantrums he began having that year were unlike anything Prieto had seen before.

“It turned out he was eating lead paint at our house and at his school,” said the mother of three, who has lived for 12 years in a rundown apartment building in Oakland’s Fruitvale district — a working-class, heavily Latino area where many homes date to the early 20th century.

When Prieto had her son tested at Kaiser Hospital, his lead levels were 21 micrograms per deciliter — roughly four times the threshold for lead poisoning set by the U.S. Centers for Disease Control and Prevention.

“It made his behavior change very radically,” Prieto said. In the months before he was tested, Alfredo started having epileptic seizures, she said. He became uncharacteristically combative. He vomited every time he drank milk.

Prieto is among many mothers in Fruitvale who are struggling to protect their children from potentially brain-damaging lead, which abounds in structures built before 1978 — the year the U.S. Consumer Product Safety Division banned lead paint on residential buildings. About 85 percent of the housing stock in Fruitvale was built before 1980, according to a new report by the Alameda County Healthy Homes Department, an agency that monitors safety conditions in residential buildings. Much of that stock appears to be contaminated, the report said.

On Tuesday, staff from the Healthy Homes Department presented their findings to the Oakland City Council’s Economic Development Committee, whose members — Larry Reid, Lynette Gibson McElhaney, Rebecca Kaplan and Annie Campbell Washington — expressed shock over the extent of the danger. Healthy Homes Director of Operations Larry Brooks urged the city to create a proactive rental inspection program to snuff out hazardous building conditions, rather than relying on vulnerable residents to complain about them.

“One of the things that troubles me about this issue is, why are we using the children in our community to be ... lead poisoning detectives?” Brooks asked. “Why aren’t we getting ahead of the ... curve?”

Concerns over lead contamination in Fruitvale have been building since December, when Reuters published results of an investigation showing that the area has a higher concentration of lead poisoning than Flint, Mich., did during its 2014-15 water crisis.

Using data provided by state health departments and the CDC, Reuters placed Fruitvale among the most contaminated neighborhoods in the U.S.: Of 500 children tested for lead in the area in 2012, nearly 8 percent had dangerously high levels of lead in their blood — significantly more than in Flint, where 1,000 children were tested at the peak of the water crisis, and 5 percent had elevated blood levels.

Old, crumbling paint isn’t the only cause for concern. Fruitvale also has a dearth of grocery stores, which means that many of the low-income children who live there have diets that are deficient in iron and calcium, increasing their risk of lead absorption.

The consequences can be brutal, Brooks said, citing cases in which protracted exposure to lead stunted children’s intellectual development.

“We’ve had children who wind up with learning disabilities, mostly because they’ve been exposed to high levels of lead for long periods of time — and the effects are not reversible,” he said. “We’ve had some children who wound up in special education classes.”

Prieto sought help from the Healthy Homes Department, whose staff provided her with a nurse and a plan to flush the lead out of Alfredo’s system. She began feeding him lots of nutritious food, constantly washing his hands and closely supervising him whenever he played outdoors. A specialist from the Healthy Homes Department asked her landlord to repaint the apartment building and place covers on the ground outside. Prieto repainted the walls and ceilings of her apartment.

Little by little, Alfredo got better, she said, but his most recent blood test showed that his blood levels are still high — 9 micrograms per deciliter. As lead-poisoned children get older, the toxin leaches from their bones into their bodies, and it can take years to reverse the damage.

In recent years, several new families have moved into Prieto’s apartment building, and some have young children who could also be susceptible to poisoning. Some families have lifted the yard covers to plant flower gardens, and two young Guatemalan girls are always playing outside, Prieto said.

She worries about them.

“I recently told them my story,” Prieto said. “I don’t want them to have to go through what I went through.”

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan