Exposure During Pregnancy to Glyphosate, the World’s Most Widely Used Herbicide, and the Risk of Preterm Birth

Glyphosate is the most commonly used herbicide worldwide and various studies have associated its use with an increased risk of cancer. Now, a new study has found that exposure to glyphosate during pregnancy is associated with an increased risk of preterm birth, i.e. the baby being born before the 37^th week of pregnancy. Preterm birth poses a significant health risk because it can be associated with both short- and long-term health effects for the child.

Although the use of glyphosate has been restricted in some European Union countries, the global glyphosate market is projected to expand at an annual growth rate of 6.3% from 2016 to 2022, reaching an estimated US$9.91 billion by 2022. Genetically modified herbicide-tolerant crops now account for approximately 56% of global glyphosate use.

Glyphosate is the most commonly used herbicide worldwide and various studies have associated its use with an increased risk of cancer. Now, a new study has found that exposure to glyphosate during pregnancy is associated with an increased risk of preterm birth.

The new study, conducted in Puerto Rico, found that prenatal exposure to glyphosate and its environmental degradate—aminomethylphosphonic acid (AMPA)—around the 28^th week of pregnancy was associated with a 30%-70% higher risk of preterm birth. This is not trivial. Exposures earlier than 28 weeks were not associated with an increased risk of preterm birth.

The authors evaluated preterm birth for two reasons. First, experimental evidence and animal studies indicate that this is an adverse health outcome that could be related to glyphosate exposure. Second, preterm birth is a major, but poorly understood, public health issue that can have negative health effects.

Glyphosate concentrations in urine were slightly lower in this study population compared with those of other general population studies investigating exposure to this herbicide. But even relatively low concentrations posed risks.

This study is interesting because it was prospective (i.e. designed to assess risk) and used a valid measure to examine exposure: glyphosate levels in the mother’s urine. However, the study was relatively small, with around 250 births included in the analysis.

The key message from this study is that, for the world’s most widely used herbicide, the most conclusive epidemiological study on a major health outcome—preterm birth—is based on a population of only 250 people.

For the world’s most widely used herbicide, the most conclusive epidemiological study on a major health outcome—preterm birth—is based on a population of only 250 people

Research on the potential health effects of glyphosate—best known by the brand name Roundup^®—is especially complicated. Regulatory and legal aspects specific to glyphosate have been a severe impediment for primary and postmarket research and control of exposure to this herbicide.

The controversy following the designation by the International Agency for Research on Cancer (IARC) of glyphosate as a probable human carcinogen was mainly, albeit not solely, orchestrated by corporate interests. The controversy was also generated by the lack of scientific evidence from large prospective studies on herbicide exposure in either farmers and professional applicators or the general public.

There is a need for additional large, diversified epidemiologic cohort studies, particularly in medium-income countries with the infrastructure to conduct such studies and where exposures are likely to be higher than those in high-income countries.

There is a need for additional large, diversified epidemiologic cohort, particularly in medium-income countries with the infrastructure to conduct such studies and where exposures are likely to be higher than those in high-income countries

Even if such major research initiatives are eventually launched, they would cover only part of the problem regarding the effects of herbicides. The extensive use of these products worldwide is a major problem for the planet, giving rise to chemical pollution and ecosystem degradation. In the case of glyphosate, widespread use has resulted in the presence of residues in house dust, soil, water and foods, according to the US Environmental Protection Agency.

Apart from classic epidemiological cohort studies, we now also need transdisciplinary research and action applying planetary health approaches to capture and eventually prevent the broader health effects of pesticides.

More information

Full study in Environmental Health Perspectives

Editorial (by Manolis Kogevinas) in Environmental Health Perspectives