A new study provides the strongest evidence yet of a link between elevated blood-lead levels in children living in Flint, Michigan, and the struggling city's water system, a pediatrician who first raised alarms about the matter said Monday.
Dr. Mona Hanna-Attisha, director of pediatric residency at Hurley Children's Hospital, and other experts compiled the report using a more refined analysis. It showed that areas in Flint with the highest levels of lead in tap water corresponded with where young children with the highest blood-lead levels lived.
The study also confirmed her earlier assessment that the percentage of children with abnormally high blood-lead levels had at least doubled after the city stopped tapping Detroit's water system to save money in 2014, and began using water from the nearby Flint River.
The findings "strongly implicate the water source change as the probable cause for the dramatic increase," according to the report published in the American Journal of Public Health. The report said the results probably understate the danger because testing is not conducted before birth and during infancy, when numbers likely would be higher. Screenings usually are performed between ages 1 and 2.
"Everybody who drank this water or cooked with this water was exposed to lead," said Hanna-Attisha, the report's lead writer and an assistant professor at Michigan State University.
Flint and Genesee County have declared public health emergencies amid public outrage over the tainted water. Lead is a powerful toxin that can damage human nervous systems and is particularly harmful for young children, causing lower intelligence, developmental delays and behavior problems.
"Lead at any level can be associated with decreases in IQ, behavioral disorders, even an association with certain juvenile delinquency as these children get older," Dr. Eden Wells, Chief Medical Executive for the Michigan Department of Health and Human Services, told CBS News.
The city of about 99,000 residents started using the Flint River as an interim water source until it could hook up to a new system drawing water from Lake Huron that is scheduled for completion next year. The cost-cutting move was made while the city was under state emergency financial management.
But the river water drew complaints about its taste, smell and appearance.
Hanna-Attisha announced in September that data from blood tests routinely administered to young children showed that lead levels had jumped since the water systems were changed. State officials initially challenged, but later acknowledged, the findings, and Flint resumed using Detroit water. The state has approved millions of dollars in aid to address the crisis.
For their updated study, Hanna-Attisha and her colleagues refined their data, focusing specifically on children under age 5 within the city limits and excluding those who live outside the city but within Flint ZIP codes, where no significant changes in blood-lead levels were found.
The researchers found that the proportion of children with at least five milligrams of lead per deciliter - the point considered elevated - had risen from 2.4 percent in the nine months before the water switch to 4.9 percent in the nine months afterward.
In neighborhoods with the highest water lead levels, the increase was even bigger: to 6.6 percent. And in one section of town, the percentage of children with elevated levels went from 4.9 percent to 15.7 percent.
No reason for the higher blood-lead levels except the water was found, the study said.
Health problems from lead can be hard to spot in young children, said Dr. Marcie Billings of the Mayo Clinic Children's Center in Rochester, Minnesota, who did not participate in the study. But parents should watch for future red flags such as anemia, low academic achievement and unusual behavioral changes, she said.
Although lead exposure is irreversible and no level is safe, not every affected child will suffer the worst results, Hanna-Attisha said. Good nutrition can help the body excrete toxins instead of absorbing them. Effective early-childhood education and relief from stresses such as poverty and violence are important.
"We have an opportunity to build a model public health program so we don't see these consequences," she said.
Concerned families can visit their pediatrician's office or go to their local health department for free blood level testing. Medicaid pays for lead tests.
"We really worry about pregnant women and infants. We know that long-standing lead exposure can lead to some long-term effects," said Dr. Carlos Lerner, medical director of the Children's Health Center at the Mattel Children's Hospital UCLA,