Associations between prenatal metal mixture exposure and negative infant outcomes


Francheska M. Merced-Nieves, PhD, Assistant professor, Departments of Pediatrics and the Institute for Exposomic Research of Environmental Medicine & Public Health, Icahn School of Medicine at Mount Sinai, explains the associations prenatal exposure to a metal mixture and the potential negative effects for the infant.

Transcript (edited for clarity):

Contemporary Pediatrics®:

Thank you so much for joining us. I'm Joshua Fitch, editor of Contemporary Pediatrics.

Francheska M. Merced-Nieves, PhD

Hi, I'm Francheska M. Merced-Nieves, PhD. I'm an assistant professor at Mount Sinai and the Institute for Exposomic Research and the Department of Pediatrics.

Contemporary Pediatrics:

Thank you so much for taking the time to speak with us today, we're discussing associations between a metal mixture and negative infant effect. First of all, can explain what these associations are, and can you break down the difference between an essential and non-essential metals and how these mothers are kind of generally exposed?


So first, let's define what are heavy metals are non-essential metals. So non-essential metals are those metals that have no biological function in our body, and in turn can have toxic effects by interrupting cellular and molecular mechanisms. So, in this case, I was interested in how they affect the brain, the nervous system, specifically behavior. In terms of and central metals, of course, these are those that do have a positive or a function in our body. So, manganese is a metal that has positive and it's necessary for healthy brain development. How are we exposed? There are multiple pathways we could be exposed. So, inhalation, thermally, or ingestion are 3 of the most common pathways. Just to give you an example, lead is a very commonly known heavy metal, that's definitely not essential and we are mostly exposed through ingestion. While these aren't naturally occurring metals, they've also been added to different products. So, lead used to be in paint, gasoline, pipes, some electronics, and while it has largely been phased out, we're still pretty consistently exposed to it. How? If we take New York City, for example, where I'm at, older buildings prior to the 1960s, have dust and old paint that they'll have lead, so we're inhaling it in terms of pipes, we can be exposed through drinking water, and that's everywhere in the United States, we can also be exposed food. Just in general, these heavy metals have been associated with a wider range of health effects in children from fetal growth, lung function, and brain development. In this specific study, we looked at behavioral effects.

Contemporary Pediatrics:

Now that we know the separation of those, how were those incorporated into your study, and can you explain the development of your study? How was it organized, and some of the results you noticed.


As I mentioned at the beginning, I'm part of the Institute for Exposomic Research, meaning most of the scientists in this Institute are interested in the exposome, we can define the exposome as everything in our environment, so that includes social stressors, chemical exposures, nutrition, or genetics. In this specific case, we were interested in looking at both chemical and social stressors. So with that, the chemical stressors were heavy metals, non-essential, specifically, so we looked at 7. In this case, they were arsenic, barium, cadmium, chromium, cesium, lead, and antimony. Looking at social stressors, we were interested in stress, and we looked at cortisol. Why cortisol? We all know it's a stress hormone, but it's the best measure of the biological embedding of chronic stress that these pregnant persons were living in in the day to day. We focus on the prenatal environment. So, we looked at the exposures during the third trimester, and then how those associated with behavior when the infants were 6 months of age, we were also interested in knowing whether girls and boys were differentially affected, so we also looked into that. Talking a bit more about the results, overall, generally, what we found was that increased exposure to both the metals and stress in this case cortisol, was associated with greater impact on brain development in this specific case, behavioral development, and that those problems were related to behaviors such as fear and sadness, and that girls seem to be more strongly impacted than boys. These domains have been linked to later psychopathology such as anxiety. However, this is not deterministic. These factors are definitely starting to operate during the prenatal period, but also that we can see early signs early on in development, and we can intervene and put these kids on a healthier track. That was the main purpose and of course, we want to prevent potentially lifelong psychological problems.

Contemporary Pediatrics:

What can general OBs tell these pregnant persons about in this general setting, if you can speak to it, and how can they kind of make parents or parents to be aware of this? What are the downstream effects during the pregnancy if anything can be done?


I think at this stage, one of the main purposes of my study and other studies in general is the need to be more aware of conscious and further stored and studied these complex interactions, since they reflect our true life environment, we're not exposed to a single chemical at a time, we're not exposed to only stress where have a lot of things happening at a time. This is especially true when you're a pregnant person, and even a little kid just starting in the world. In terms of prenatally, I think clinicians should be definitely counseling women on better nutrition. This does protect the brain development, and we know that, but it also counteracts the toxicity of stress and some of these metals. For example, better intake of anti-oxidants, and other nutritional factors. In terms of stress, provide better resources and support that can reduce stress strain, in the prenatal and postnatal period. In terms of the infants and postnatally, in addition to healthy nutrition, because that is key to a lot of our health, also having a high-quality social environment. So as I just mentioned, having reduced stress in parents would definitely help but in addition, providing parents with parenting strategies have been shown to foster resiliency, and this of course, is very important in kids and their development.

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