Researchers are looking into the possible ripple effects of lead exposure. Even low levels of lead can cause children to lose IQ points and develop behavior problems.
After Flint, Michigan switched to the Flint River for its drinking water in 2014, experts found the number of children with elevated levels of lead in their blood doubled. Although the city switched back to Detroit water last fall, lead continues to be a concern, due to the corrosive effects of Flint River water on the city’s pipes.
The city has begun handing out filters to residents, but for kids, that won’t reverse the damage done.
A recent study suggests lead exposure can cause changes to DNA that might affect several generations.
Doug Ruden is the Director of Epigenomics at the Institute of Environmental Health Sciences at Wayne State University. He tested blood samples from 35 Detroit mothers and their babies.
“We recruited young mothers who were born after 1984 and got permission to measure their blood lead levels,” Ruden says.
Ruden’s team observed a correlation between elevated blood lead levels in the mothers and changes in DNA.
“If the mothers had high blood lead levels when they were born, then their grandchildren have changes in their DNA,” he says. “And the changes in the DNA we were looking at weren’t mutations — they weren’t permanent changes — but they’re what we call epigenetic mutations. They’re changes in DNA methylation.”
DNA methylation is a process that changes the expression of genes as cells divide and differentiate during fetal development.
“It’s thought that’s how lead causes neurobehavioral defects — or loss of IQ in children,” he says. “It’s not by directly mutating the DNA, but altering their DNA methylation.”
Ruden says more studies will have to be done to determine if these changes are good, band or neutral.
“Mothers who are exposed to lead in the water, for instance, can not only affect their children’s IQ but can also affect, potentially, the IQ of their grandchildren,” Ruden says. “We know the DNA is affected, but we don’t know right now whether these changes in the DNA in the grandchildren can also affect their IQ.”
Ruden says he’s studying how exposures in pregnancy can affect not just the baby a mom is carrying, but also her grandbabies.
“The way you think about it is: if a mother is pregnant with a baby, she’s also carrying the baby’s children too,” he says. “Because it’s like a Russian doll.”
He says a fetus develops fetal germ cells while still inside its mother.
“So all of the eggs that a person has in life are actually developed in the fetus, during the fetal period, and all the sperm progenitor cells in the boy babies are also present in the fetus,” he says. “So when a mother drinks leaded water, like what happened in Flint, she’s exposing her fetus, so that’s going to directly affect brain development of her baby.”
But he says, there could be effects on the next generation too.
“What most people don’t realize is that you’re also expressing the germ line cells, and that can affect the grandchildren, and even potentially beyond that,” he says.
One important caveat here: this study is small. Ruden says it will need to be repeated on larger scales and in different populations.
“It is well established in animal models, though — like in mice and rats — that environmental exposures to compounds such as lead can have effects for many generations,” he says. “So this isn’t entirely surprising.”