The long-term effects of lead exposure at young ages could increase the risk of obesity later in life, a University of Michigan School of Public Health study found. The study — which researchers noted shows a possible life-long impact in the state for Flint residents in particular, due to the cities water crisis — was a controlled experiment performed on young mice from 2012 to 2014 that considered the impacts of lead on the mice’s weight.
The study was performed by Dana Dolinoy, associate professor of environmental health sciences, along with Chuanwu Xi, associate professor of environmental health science.
The mice used in the study were the offspring of female mice who were exposed to lead before breeding, Dolinoy said in an interview. The female mice were exposed to lead for a three-week period of gestation and another three-week period of lactation after birth. Then for nine months, the newborn mice matured without further lead exposure, while their weight and gut microbiome compositions were measured.
Unlike other similar studies about the effects of lead, Xi said this study focuses on the long-term effects of short-term lead exposure.
“It is not immediate,” he said. “We are particularly interested in the long-life effects.”
Xi added that the team was able to show that lead exposure changes the composition of bacteria in the gut microbiome. Though both female and male microbiota changed, only male mice were found to have body-weight gain.
“The composition of the gut microbiome is quite complex,” Xi said. “So what we found is, we don’t really see a dramatic change in terms of complexity of the gut microbiome. But what we see is that the abundance of specific microbe populations change. That’s clearly demonstrating you have a changing gut microbiome.”
The study used a range of lead levels on mice, including a level higher than the current levels to simulate historic levels from the 1960s and 1970s, Dolinoy said. Xi added that this is because the concentration of lead from the past can still be found today in paint and old lead pipes, such as those used to carry water in Flint.
“Lead is a historical problem,” Xi said citing severasl ways humans can be exposed to lead. “The other route (to lead exposure) is lead-contaminated pipes for drinking water, like Flint.”
Though a 10-percent average increase in body weight in adult male mice was recorded, when predicting human weight effects, Dolinoy said it gets more difficult since the mice experiment was controlled, whereas many factors can impact human health.
“Along with this mouse model we have different human cohorts where we study similar things,” Dolinoy said. “But as you can imagine, waiting for a human baby to grow up takes decades when we can answer similar questions in mice over just a few years.”
Xi emphasized that this study, though revealing new information, should be seen only as a risk, not a concrete outcomes.
Speaking to ways to avoid weight gain, Xi said the weight gained from lead exposure can be controlled or reversed. Referencing the heightened levels of lead found in Flint water in 2015, Xi suggested those exposed to lead adopt a lifestyle of eating healthy and exercising. Dolinoy added that a having a strong social network of family and friends helps too.
“They (the children of Flint) have the long-lasting effects,” Xi said. “You need to pay more attention to your own lifestyle to mitigate the potential risk. This is more like an alert to the individuals.”
Kinesiology freshman Devlin Francis, a volunteer in Flint, said he thought Dolinoy and Xi’s research shows there is still a lot of work to do in Flint.
“This was already a crisis to begin with, so now it’s only worse,” Francis said. “I just think it gives an even larger reason as to why we all need to do something to help out. And, like, we’re not going to achieve anything by pointing fingers at the governor or the city officials or anyone, like a lot of people have. You can do that later when the problem’s been solved, but right now there isn’t really time for that because people actually need help.”
Engineering freshman Charlie Velis, philanthropy chair of Delta Tau Delta, said he thinks it is unethical to ignore the water crisis in Flint, especially in light of the new research and the help residents require to rebuild their infrastructure.
“We live in a bubble as college students, and I think that one of the hardest things for me is when I see peers try hard to remain in that bubble and refrain from understanding the really important issues around them,” Velis said.
Xi said it will be difficult to know until further studies are done, despite the changing microenvironment of the gut microbiome, what other types of health impacts lead exposure could have.
In the future, he said he hopes to take a retrospective look at past human populations to find causal effects of disease and health on current populations. Xi noted this could be helpful for helping the children of Flint, noting action should still be taken to help them in the meantime.
Dolinoy added that Flint is a public health issue, and work should be done to ensure that residents have the knowledge to combat the risks of lead to the best of their abilities.
“This really tells us that we need to invest in our public health infrastructure,” Dolinoy said.
While studies on mice are the start, Dolinoy said they have five cohorts of human populations being studied, which will be the next indicator in this process. This additional work being done to work will be completed when the human cohorts reach adulthood.
“Now we know the kids are already exposed to the lead, so they need to take a mitigation approach,” Xi said. “We know this information is really good for the kids. It is unethical (to not take action). If we know a certain population is exposed to lead, we know there is an increased risk.”