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New research into the world’s most widely-used pesticide raises concerns for fetal health, according to researchers from the Children’s Environmental Health Network (CEHN). Glyphosate, which is used to kill broadleaf plants and grasses, is found in more than 750 products including Monsanto’s Roundup. The study discovered a correlation between glyphosate exposure during pregnancy and lower birth weights, as well as shorter pregnancies.

The research is part of the Herbicide Use and Birth Outcomes in the Midwest CEHN Healthy Kids Project. Sixty-nine pregnant women in the Midwest, where pesticide use is extensive, were followed and the amount of glyphosate in their urine tracked from 2015-2016. Women living in rural areas had higher glyphosate levels than women living in urban and suburban areas, and 91 percent of participants tested positive for the pesticide.

For high-exposure pregnancies studied, the average gestation period was nearly four days shorter. Low-exposure gestational-adjusted birth weights were in the 58th percentile while high-exposure dropped to the 43rd percentile. Low birth weight can lead to health problems, including respiratory distress as a baby and heart disease later in life.

“This is a huge issue. Everyone should be concerned about this,” said Paul Winchester, medical director of the Neonatal Intensive Care Unit at the Franciscan St. Francis Health System, Professor of Clinical Pediatrics at Riley Hospital for Children in Indianapolis, Indiana, and lead author of the recent CEHN pregnancy research.

Although the CEHN study was small and preliminary, it adds to a growing body of research raising concerns over the use of glyphosate. The U.S. Federal Regulations for glyphosate exposure were last updated in October 1980. Since then, improved techniques and technologies, including genetic analysis, have been used to reevaluate the original toxicology conclusions.

Several important discoveries have been made about glyphosate over the past decade. Glyphosate exposure in fish is both genotoxic (damages DNA) and causes oxidative stress (damages cells and DNA). Zebrafish are often used to study early development. Results published in the journal Chemosphere reveal neurological damage and developmental delays in zebrafish exposed to glyphosate as embryos. A review in the Journal of Cardiovascular Toxicology by French and Italian researchers outlines cardiovascular changes, including arrhythmias, observed in rabbits and rats on exposure. A rat study using chronic but low doses of Roundup found liver and kidney damage, reported in the Journal of Environmental Health. A group at Massachusetts Institute of Technology makes a case for glyphosate as the cause of Celiac disease based on similar symptoms observed in fish exposed to the pesticide.

However, published human research is divided as to whether glyphosate is harmless or a health concern. CEHN’s pregnancy study reflects this, with a limited epidemiological review in 2016 and literature review conducted by a consulting firm concluding glyphosate does not have developmental or reproductive effects on humans. A report in 2011, “found no evidence of a consistent pattern of positive associations indicating a causal relationship between any disease and exposure to glyphosate.” Meanwhile, a review in 2015 found, “a coherent body of evidence indicating that [glyphosate] could be toxic below the regulatory lowest observed adverse effect level for chronic toxic effects.”

In a letter to the Journal of Epidemiology and Community Health published in March 2017, a group of researchers concludes, “We have identified factors that heighten concerns over the adequacy of safety assessments, and by extension, permitted levels of exposure to glyphosate. Considering what is now known about glyphosate from studies published over the last three decades, as well as the knowledge gaps that continue to raise concerns, we conclude that current safety standards for [glyphosate] are outdated and may fail to protect public health and the environment.”

Classifying glyphosate as a carcinogen is particularly controversial. The International Agency for Research on Cancer (IARC), a subdivision of the World Health Organization (WHO), concluded in March of 2015 that glyphosate does probably cause cancer. The following year, a United Nations Joint Meeting on Pesticide Residues between the Food and Agriculture Organization of the United Nations (FAO) and WHO concluded that glyphosate is probably not a carcinogen. However, several of the meeting’s organizers, including the chair, had financial connections to glyphosate companies including Monsanto.

When the European Union (EU) began reevaluating the use of glyphosate in 2016, the Glyphosate Task Force (GTF), “a consortium of companies joining resources and efforts in order to renew the European glyphosate registration,” was formed to promote a favorable outcome. Published reviews written by consultants hired by GTF and research funded by GTF conclude there is no connection between glyphosate and cancer. However, a meta-analysis conducted in 2014 found a positive association between glyphosate exposure and B-cell lymphoma, a form of non-Hodgkin’s lymphoma. The EU ultimately determined that the pesticide was not a carcinogen in March of 2017.

The U.S. Environmental Protection Agency (EPA) is currently reevaluating the carcinogenesis of glyphosate with a final report expected by the end of 2017, but an independent Scientific Advisory Panel is split in its assessment of the EPA’s work. When the state of California considered independently listing glyphosate as a carcinogen, Monsanto sued. California moved forward and added the pesticide to Proposition 65 list of chemicals known to cause cancer in March of 2017. Documents released as a result of legal action in California reveal possible manipulation of the EPA by Monsanto. The U. S. Department of Agriculture dropped plans to test foods for glyphosate and the Food and Drug Administration stopped its limited testing program, despite pressure from the United States Government Accountability Office to conduct routine testing.

Glyphosate works by inhibiting an enzyme that allows plants to make several amino acids they need to live. Use of the pesticide has increaseddramatically with the introduction of genetically modified crops resistant to glyphosate. Residual amounts of glyphosate are found in numerous food items, including Cheerios cereal, Oreos, Ritz crackers, and even Annie’s Gluten-Free Cocoa and Vanilla Bunny Cookies. In 2013, Researchers at the University of California San Francisco tested urine from 131 people across the United States and found detectable levels of glyphosate in 93 percent of individuals.

“Is this level of exposure safe or not? We’ve been told it is, but exposures haven’t been measured,” says Dr. Winchester, lead author of the recent CEHN pregnancy research. “It’s mind-boggling.”