Abstract
The broad-spectrum herbicide glyphosate (common trade name “Roundup”) was first sold to farmers in 1974. Since the late 1970s, the volume of glyphosate-based herbicides (GBHs) applied has increased approximately 100-fold. Further increases in the volume applied are likely due to more and higher rates of application in response to the widespread emergence of glyphosate-resistant weeds and new, pre-harvest, dessicant use patterns. GBHs were developed to replace or reduce reliance on herbicides causing well-documented problems associated with drift and crop damage, slipping efficacy, and human health risks. Initial industry toxicity testing suggested that GBHs posed relatively low risks to non-target species, including mammals, leading regulatory authorities worldwide to set high acceptable exposure limits. To accommodate changes in GBH use patterns associated with genetically engineered, herbicide-tolerant crops, regulators have dramatically increased tolerance levels in maize, oilseed (soybeans and canola), and alfalfa crops and related livestock feeds. Animal and epidemiology studies published in the last decade, however, point to the need for a fresh look at glyphosate toxicity. Furthermore, the World Health Organization’s International Agency for Research on Cancer recently concluded that glyphosate is “probably carcinogenic to humans.” In response to changing GBH use patterns and advances in scientific understanding of their potential hazards, we have produced a Statement of Concern drawing on emerging science relevant to the safety of GBHs. Our Statement of Concern considers current published literature describing GBH uses, mechanisms of action, toxicity in laboratory animals, and epidemiological studies. It also examines the derivation of current human safety standards. We conclude that: (1) GBHs are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science. We offer a series of recommendations related to the need for new investments in epidemiological studies, biomonitoring, and toxicology studies that draw on the principles of endocrinology to determine whether the effects of GBHs are due to endocrine disrupting activities. We suggest that common commercial formulations of GBHs should be prioritized for inclusion in government-led toxicology testing programs such as the U.S. National Toxicology Program, as well as for biomonitoring as conducted by the U.S. Centers for Disease Control and Prevention.
Highlights
This Statement of Concern is directed to scientists, physicians, and regulatory officials around the world
The objectives of this statement are to: 1) demonstrate the need for better monitoring of glyphosate-based herbicides (GBHs) residues in water, food, and humans; (2) identify limitations or weaknesses in the way the Environmental Protection Agency (EPA), the German Federal Institute for Risk Assessment, and others have previously assessed the potential risks to humans from exposure to GBHs; and (3) provide recommendations on data needs and ways to structure future studies addressing potential health risks arising from GBH exposures
We highlight a number of issues that influence our concern about GBHs including: 1) increased use of GBHs over the past decade, including new uses for these herbicides just prior to harvest that can lead to high dietary exposures; 2) detection of glyphosate and its metabolites in foods; 3) recent studies that reveal possible endocrine system-mediated and developmental impacts of GBH exposures; and 4) additional complications for farmers, most acutely the emergence and spread of weeds resistant to glyphosate and the concomitant use of multiple herbicides in mixtures, both of which increase the risk of human and environmental harm
Summary
This Statement of Concern is directed to scientists, physicians, and regulatory officials around the world. In light of the increased numbers, levels and extent of herbicide use elicited by weed resistance, it is reasonable to predict that there will be a marked increase in the diversity of biological pathways affected, the number and duration of high-exposure periods, and the magnitude of potential risks facing non-target organisms, including humans Such impacts could be limited, or even largely prevented, if there are substantial changes in weedmanagement systems and regulatory policy, including enforceable limits on herbicide-use patterns known to cause relatively high and potentially unsafe residue levels in food, water, and the air. The emergence and spread of glyphosate-resistant weeds requires farmers to spray additional herbicides, including older herbicides posing documented environmental and public health risks and/or newer, more costly herbicides to avoid crop yield losses and slow the spread of these weeds [37] This is problematic in grain and row-crop fields planted for several years with Roundup Ready GE crops. In the U.S, contending with resistant weeds has already increased total herbicide use per acre by approximately 70 % in soybeans, and 50 % in the case of cotton compared to herbicide rates on these crops in the mid-1990s when GE varieties were first introduced [10]
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