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Issues Of The Environment: New Study Links Common Herbicide To Risk Of Premature Birth

John Meeker
University of Michigan School of Public Health

Glyphosate, which is usually found in stores as the product Roundup, is the most frequently used herbicide in the world. While it is effective in killing weeds, it is also harmful to health. A recent study out of the University of Michigan links exposure to pre-term births. WEMU's David Fair spoke with the study's senior author, Dr. John Meeker, about the findings and where the research goes from here. 


  • The herbicide has been linked to dozens of health problems, including cancer, liver and kidney damage, and reproductive and developmental issues. Children, who are thought to be most vulnerable to the effects, tend to have the highest levels of the chemical. In the wake of mounting lawsuits, Bayer (who currently produces Roundup following the departure from Monsanto) announced in July 2021 that they plan to phase out glyphosate from their products. (Source: https://uspirg.org/news/usp/bayer-plans-phase-out-use-harmful-chemical-roundup)

  • A recent UM of study found that, in addition to the known health risk, glyphosate is significantly correlated with an increase in preterm births. Preterm deliveries (babies born before 37 weeks of gestation) are associated with a host of short and long term negative health outcomes. The UM study looked at births in Puerto Rico, and a recent study in Indiana also saw preterm births increase with increased levels of exposure. 


David Fair: [00:00:00] This is Eighty-Nine, one WEMU, and welcome to another edition of Issues of the Environment. At one point or another, you have likely been exposed to glyphosate. It was developed for commercial agricultural use to protect crops. And as it became available in the residential realm. You probably know it better as Roundup. So many use it to keep weeds out of home gardens. That is just about ever present now. Huber glyphosate is low and toxicity, but products like Roundup usually contain other ingredients that help keep the glyphosate in plants. The other ingredients can make it more toxic. In fact, a study launched in 2015 found that 93 percent of those tested had glyphosate in their urine. What might that do to a pregnant woman and her unborn child? Well, that's a question to which our guest wanted an answer. Dr. John Meeker is senior author of the study exploring that question. Dr. Meeker is professor of Environmental Health Sciences and Global Public Health at the University of Michigan. Thank you for taking time today. Much appreciated.

Dr. John Meeker: [00:01:00] No problem. Thank you for having me.

David Fair: [00:01:02] What exactly...was there a specific incident that led you down this particular research path?

Dr. John Meeker: [00:01:09] Well, we've been studying pregnant women for about 10 or 12 years, trying to think about what environmental factors might impact their pregnancy health. And when we talk about environment, we're thinking, you know, broadly, chemicals, also maternal stress, neighborhood factors, things like that.

David Fair: [00:01:28] We know Roundup and other herbicides containing glyphosate are ubiquitous throughout the agricultural industry. And most of the studies done prior to yours had been measuring its impact on animals. What did your study find when it comes to the impact on human pregnancy and birth?

Dr. John Meeker: [00:01:46] What we found was we measured the glyphosate active ingredient, as well as an environmental degradate called AMPA in the mother's urine at two time points in pregnancy. We found that the first time we didn't see an association or for its outcome. But for that other time point later in pregnancy, we did see the increased risk of preterm birth and associated with increased levels of both the glyphosate and the AMPA metabolite.

David Fair: [00:02:13] And beyond chemical exposure, premature babies potentially face a whole long list of impacts just from arriving early, right?

Dr. John Meeker: [00:02:21] That's correct. And it can, you know, anything from infant death to serious disability throughout life. So, it is a very serious condition that had been has been increasing in recent years throughout the U.S. and especially in certain areas. This study took place in Puerto Rico, where when our study began 10 years ago, there were very high levels of preterm rate, almost 20 percent. Luckily, that's gone down since then, but it's still very high, well over 10 percent. So very common and very serious health condition for sure.

David Fair: [00:02:53] We're talking with Dr. John Meeker from the University of Michigan on Eighty-Nine one WEMU's Issues of the Environment. He is senior author of a recently published study on impacts herbicides can have on preterm birth. The good news, Dr. Meeker, is that Bayer, which manufactures and distributes Roundup, now that it was spun off from Monsanto, announced in July it would phase out the use of glyphosate in Roundup in the year 2023. And yet, 2023 is a ways off, and it seems to me a lot of damage can still be done in the interim. Fair assessment?

Dr. John Meeker: [00:03:26] Yeah, yeah. We have to look at a lot of things with that type of statement. What is it going to be replaced with for one? And, two, there are many other companies that are now using the same chemical in their herbicide. So, you know, just because the company that invented it is taking away, that doesn't mean other companies who are producing and distributing it are going to do the same thing.

David Fair: [00:03:47] And because the agricultural industry has determined that it is effective for its stated purpose, then they are likely to continue using it if it's available. Do you have any idea what could possibly be used to replace it?

Dr. John Meeker: [00:04:02] Not specifically, no. There are many ways to grow crops, and hopefully it'll involve something that uses less chemical. Obviously, herbicides and other chemicals, insecticides, et cetera, have made food production much more efficient, which is extremely important as our world population grows. But we need to look at other types of techniques that might help us to get that yield, but also reduce the amount of chemicals that we have to use.

David Fair: [00:04:31] And replacing one chemical with another isn't necessarily always better. So, what will you be looking for as we start to see phase out of glyphosate in Roundup?

Dr. John Meeker: [00:04:44] We'll be looking at a couple of things. Again, you know, with one example being that measuring it in biological fluids. We can look at whether those levels decline over time moving forward and then look at what the active ingredient, the replacement equipment, can we start measuring that in our study participants.

David Fair: [00:05:03] Once again, this is Issues of the Environment on Eighty-Nine one WEMU, and we're talking with Dr. John Meeker from the U of M, where he serves as professor in Environmental Health Sciences and Global Public Health. Dr. Meeker, we can take active measures to prevent exposure around our homes by not using products that have glyphosate and the like. But, as we've pointed out, it appears in most foods. Are there certain foods that we should avoid to protect ourselves and, in particular, for women who are pregnant?

Dr. John Meeker: [00:05:37] The data for glyphosate, specifically, is a little hit or miss. There's certain cereal grains that have been measured to have...

David Fair: [00:05:46] Oats, in particular, seem to have high levels right?

Dr. John Meeker: [00:05:49] Right. Right. But, you know, depending on who you ask and what level you're using a quote unquote safe level, those assessments can differ. So, you know, you get the chemical manufacturers are saying, "Oh, the levels are so low, it's not a concern." Whereas if you use more sensitive toxicology studies more recently in the literature, you might come up with a much lower level that might be considered safer.

David Fair: [00:06:14] And, as part of the study that you are doing, are you monitoring what women are eating while they're pregnant and what is being fed to the babies once born preterm?

Dr. John Meeker: [00:06:25] Yes, part of our study is to ask them what foods they're eating and what they're feeding their children. We haven't gotten to that level of detail in the data analysis yet, but that is something we would like to do in the future to look at. What are they eating and does that correlate with increased levels of glyphosate in their urine?

David Fair: [00:06:43] I think that, among many, there is an assumption that if we eat organic foods, then we will be safe from these kinds of things. And the fact of the matter is there are organics that have these kinds of chemicals in them as well, right?

Dr. John Meeker: [00:06:57] That's correct. There are studies that have found, you know, not as common in organic foods. So, overall, when you're talking about all pesticides, buying and eating organic, will reduce the overall level of exposure. However, given the widespread usage, you know, hundreds of millions of pounds of glyphosate are being used on crops. There are many ways in which, you know, through drift or through manufacturing practices, whatever it is, packaging, you might get some contamination. So, it is true that there have been some organic products measuring low levels of glyphosate.

David Fair: [00:07:31] You mentioned that you've been doing this research for a decade plus now and you're doing more analysis. What are the next steps in this particular research effort?

Dr. John Meeker: [00:07:43] So, our study in Puerto Rico was what we call a nested case control study. So, based on the resources we have, that time is fairly small. We're going to expand and increase our sample size and get more what we call statistical power. And we're also going to look at what might be the biological pathways through which glyphosate may be impacting pregnancy. So, we're looking at things like endocrine disruption, oxidative stress, and others to see if we can form that link from exposure to that intermediate to the adverse pregnancy outcomes.

David Fair: [00:08:15] I know that it is completely against the ethos of any scientist to come to any predetermined outcome or to even make any kind of assumption, but, as you look forward, is it possible that we're going to come to the conclusion that no exposure to any chemical is going to be harmless to women and to their unborn and newly-born children?

Dr. John Meeker: [00:08:42] Yeah, that's a very complex question, because, you know, we're exposed to so many things every day throughout our lives. That it is tough to tease it apart. We use a lot of different tools to try and do that through, you know, lab based studies of cells, to animal studies, to the type of human study I'm describing here. Yeah, I mean, every chemical compound has its, you know, toxicity level, and we're finding, you know, through more sophisticated scientific methods that those levels may be lower than had been thought safe, you know, decades ago.

David Fair: [00:09:16] When you do this kind of research and you get into the analysis of it and come to some scientific conclusions, is there a personal reward in it for you beyond the science and into the impact on human health?

Dr. John Meeker: [00:09:30] Oh, certainly. And working with human populations even more so, I think. We, you know, back to your original question on motivation for this particular study, we were driving around visiting our various collaborators and clinics in Puerto Rico. And, you know, they're very appreciative of us trying to figure out what might be harmful to them, how to be healthier during their pregnancies, and, during one of those visits, I actually saw a sign on the roadside for a glyphosate product. At the time, we hadn't even considered looking at glyphosate. But I'm, like, thinking to myself, "This is something. You know, if they're selling it just down the street from this clinic, it might be widespread down here." So, that's just one example of really, you know, talking with the participants, talking with our collaborators, getting to know the area to try and investigate things that might help improve their health.

David Fair: [00:10:21] And in the end, it is about the environment, but, more importantly, people. Professor Meeker, thank you so much for the time today. I really appreciate it.

Dr. John Meeker: [00:10:28] My pleasure. Thank you.

David Fair: [00:10:30] That is Dr. John Meeker, professor of Environmental Health Sciences and Global Public Health at the University of Michigan. For more information on the study we've been talking about, visit our website at WEMU dot org, and we'll get you linked up everywhere you need to go. Issues of the Environment is produced in partnership with the office of the Washtenaw County Resources Commissioner. And you hear it every Wednesday. I'm David Fair, and this is your community NPR Station, Eighty-Nine one WEMU FM and WEMU HD, one Ypsilanti.

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— David Fair is the WEMU News Director and host of Morning Edition on WEMU.  You can contact David at734.487.3363, on twitter @DavidFairWEMU, or email him at dfair@emich.edu

Contact David: dfair@emich.edu
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