Claire Hutkins Seda, Migrant Clinicians Network, Managing Editor, Streamline
[Editor’s Note: The following is a summary of an article in Environmental Health. Read the complete Scientific Statement of Concern at http://goo.gl/DeUlSA.1]
In February, a group of 14 health scientists published a Statement of Concern on glyphosate, the ubiquitous herbicide marketed under brand names like Roundup.1 The scientific review, printed in the journal Environmental Health, tracks the herbicide’s “100-fold” increase in use to become the most heavily applied herbicide in the world, the resultant growth in glyphosate-resistant weeds and other “unanticipated effects” of its increased use, and the more recent animal and epidemiology studies that challenge the level of glyphosate considered safe for humans. To illustrate these concerns, the health scientists detailed a number of “consensus points” on the agreed-upon impacts of glyphosate, followed by a lengthy list of recommendations.
Increased and varied usage
The article couches its concern in the dramatic increase in use in the past decade, along with growing resistance and the impact of exposure to glyphosate chemical mixtures. The use of glyphosate-based herbicides (GBHs) skyrocketed in the mid-1990s, upon the introduction of “Roundup Ready” crops on which glyphosate could be directly applied onto food crops. Currently, corn, soybeans, cotton, canola, alfalfa, and sugar beets have been genetically modified to be “Roundup Ready” and approved in some nations for planting.
Usage has also changed; authors note that GBHs are now being used later in the crop cycle, and, with some crops like wheat and barley, GBHs are used in nontraditionally to “accelerate crop death, drying, and harvest operations.” As a result, residue levels on some crops are “substantially higher” than they were ten years ago, resulting in increased human dietary exposure.
Increased usage has resulted in the widespread growth and unprecedented spread of glyphosate-resistant weeds, authors argue, and can significantly affect agricultural practices: “The consequences triggered by the spread of glyphosate-resistant weeds, in contrast to the emergence in the past of other herbicide-resistant weeds, are unparalleled, and include the need for major changes in tillage and cropping patterns, and large increases in farmer costs and the diversity and volume of herbicides applied.”
The authors are also concerned about glyphosate in combination with other chemicals in GBHs. Data confirm that chemicals in combination may change the risks posed; surfactants, for example, a common addition to GBHs, are known to increase the toxicity of glyphosate. As regulators test toxicity of chemicals singly, current regulations may fail to accurately predict the toxicity of glyphosate in combination with other chemicals.
Newer health studies change the landscape
Concurrent with the increased usage in agricultural has been an increase in epidemiological studies and research on the effects of glyphosate. Initial studies when glyphosate was first introduced concluded that vertebrates were likely unaffected by the herbicide because it targeted a plant enzyme not present in vertebrates. But recent research suggests a “wide range of adverse outcomes” for human health including endocrine disruption, birth defects, hepatorenal damage, and gastrointestinal health issues. The authors cover additional studies that have suggested other health risks have a causal links to GBH exposures, but need further research, like the increase in non-Hodgkin’s Lymphoma and the epidemic of chronic kidney disease of nontraditional etiology in Sri Lanka and Central America.
The health of the environment is also greatly affected by the increased usage of GBHs. The authors note that increased usage contaminates rainwater, groundwater, and drinking water. Newer studies have determined that the half-life of glyphosate in water and soil is “longer than previously recognized,” and dependent on soil types, thereby limiting the ability of researchers to accurately predict how long soil will be contaminated.
Detection of glyphosate in foods
The health implications, say the authors, are not limited to those within the agricultural sector. The statement lists multiple studies detecting glyphosate residues in food for human consumption, but also notes that adequate surveys of GBH contamination in food have not been conducted.
Daily intake and regulatory limits
Early risk assessments to the human population were based on initial research that indicated limited effects on vertebrates; newer research debunks these assumptions, but acceptable daily intake as determined by government agencies. Another key early assumption, that glyphosate would not be persistent in the environment, has also been proven incorrect. Meanwhile, huge increases in prevalence of glyphosate worldwide have not been followed up with monitoring to determine the level of exposure in the human population. The authors conclude that tolerable daily intakes for glyphosate are based upon outdated science, in the US as well as in Germany.
“These conclusions all indicate that a fresh and independent examination of GBH toxicity should be undertaken, and that this re-examination be accompanied by systematic efforts by relevant agencies to monitor GBH levels in people and in the food supply, none of which are occurring today,” the authors state. “The US National Toxicology Program should prioritize a thorough toxicological assessment of the multiple pathways now identified as potentially vulnerable to GBHs.”
1 Myers JP, Antoniou MN, Blumberg B, et al. Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environ Health. 2016;15(1):19.