There has been intense attention focused on the safety of agricultural chemicals over the past year, following two successful lawsuits against the Monsanto Company (which merged with Bayer in 2018) that claimed the herbicide glyphosate (Roundup®) caused the plaintiffs' cancers. But jury verdicts are not the same as scientific conclusions, and the data and the judgements of experts worldwide lead to different conclusions from those of the jurors.
In January 2019, Health Canada was the most recent regulatory entity to weigh in on the safety of glyphosate, observing, "[n]o pesticide regulatory authority in the world currently considers glyphosate to be a cancer risk to humans at the levels at which humans are currently exposed."
The recent lawsuits claiming injuries from glyphosate have led to increased calls by activists for a ban on the chemical. But such a ban would impose enormous costs on food production and consumers, and also on the environment, as older, more toxic chemicals would reappear.
Regulation of Chemicals
Herbicides and other agricultural chemicals are heavily regulated. Prior to their approval for use, scientific risk-assessments are performed by national regulatory bodies, using all available data. From such assessments, an acceptable safe residue level on or in food products is established which is often six orders of magnitude—one-millionth—of levels that could be harmful. The U.S. EPA has established tolerances for glyphosate on a wide range of crops, including corn, soybean, oilseeds, grains, and some fruits and vegetables, ranging from 0.1 to 310 parts per million. In practice, these levels are seldom exceeded.
According to the Extension Toxicology Network, operated by several prestigious universities, the single-consumption lethal acute dose of glyphosate necessary to kill 50% of tested rats (LD 50 ) is 5,600 mg/kg (5600 ppm) . Translated to a 100 kg (220 pound) man, the LD 50 would be massive – about a pound and a quarter of the chemical, or 167 percent greater than the amount usually applied to an acre of farmland.
What, then, has prompted the concern and disagreement over glyphosate? In short, a single anomalous outlier: In 2015, glyphosate was classified as a "probable carcinogen" by the United Nations' International Agency for Research on Cancer (IARC). Their hazard assessment failed to take into consideration dose or exposures and has also been criticized for the corruption of the process. Using this failed paradigm—performing assessments of hazard, rather than risk—IARC placed glyphosate in the same hazard category as red meat and hot beverages, things most of us consume frequently.
Health Canada's statement that not a single chemical regulatory agency in the world considers glyphosate to be a human health risk echos the excellent infographic just published by the Genetic Literacy Project. Although science can never prove a negative—such as that something is 100 percent safe—this consensus is about as definitive a health safety statement as can possibly be made by government entities.
The Importance of Farm Chemicals
As any farmer or home gardener knows, weeds are obstinate. They germinate earlier, grow faster, and produce far more seeds than seeded crops, making weed control essential for successful farming. Evolution has ensured that weeds know how to thrive and to ensure a successful next generation. For example, palmer amaranth, a particularly noxious weed in the southern U.S., produces one million seeds per plant. Kochia, a common weed in Western Canada is capable of producing 25,000 seeds per plant.
By comparison, a good yielding variety of wheat typically produces 25-30 kernels per plant, with 40 kernels being exceptional. With weeds producing 1,000 to 25,000 times more seeds than a crop plant, it doesn't take long for poor weed control practices to become a big problem for farmers.
Inadequate weed control lowers crop yields in all production situations. African studies show the devastating effects on crop yields of uncontrolled or sub-optimally controlled weeds (Joubert 2000; Kwiligwa et al. 1994; Atera 2012). Poor weed control is the single biggest contributor to low corn yields for African smallholder farmers. Female hand-weeding is a common practice in developing nations, and the number of times it is necessary to weed following planting has been identified as the principal limiting factor to the size of African farms. Yield losses of 20-80 percent are common in parts of sub-Saharan Africa when proper weed control practices are not followed.
Unlike modern agriculture in developed nations, much of the agriculture of developing countries lacks the technologies and access to practices necessary for weed control. Fortunately, herbicide-tolerant, genetically engineered (GE) crops are slowly being introduced, offering producers access to effective and efficient means to control weeds. Research on three seasons of small-landholder adopters of GE crops in South Africa found that female farmers growing herbicide-tolerant GE corn spent 10-12 fewer days per season in the field doing arduous weed-pulling and hoeing than counterparts who planted conventional corn. With two crop seasons per year, these female farmers saved three weeks of field labor, a benefit which they reported allowed them to have larger vegetable gardens and to spend more time with their children.
The Costs of Prohibiting Farm Chemicals
Calls from various environmental organizations to ban the use of chemicals in food production are naïve. One study has estimated that the costs associated with a global ban on glyphosate, the most commonly used herbicide, would be $6.76 billion annually. This would result from lower production of the primary glyphosate-resistant, GE crops like soybeans, corn and canola, which would put upward pressure on food prices. In addition, the loss of availability of glyphosate would force farmers to use large amounts of other, less effective chemicals, resulting in increased chemical use by 1.7 percent, or 8.2 million kilograms, of chemical active ingredient. This would cause a 12.4 percent greater environmental impact, the study found.
The additional chemical applications would reduce carbon sequestration, due to the rise of tillage to control weeds, and increase greenhouse gas emissions. That would be the equivalent of putting 11.8 million more cars on the roads. Moreover, banning one chemical would simply result in the increased use of others that have greater environmental impacts, set back efforts to mitigate climate change, and increase food insecurity and food prices.
One study that has calculated the environmental costs of not adopting herbicide-tolerant crops found that they were significant. The assessment, of Australia's moratorium on genetically engineered canola, estimated that the environmental impacts during 2004-2014 included:
- Additional use of 6.5 million kilograms of chemicals;
- Seven million additional field passes, requiring 8.7 million liters of diesel;
- the release of 24 million kilograms of greenhouse gases (equivalent to 5,000 cars being driven for one year); and
- 14 percent higher negative environmental impacts, due to the additional chemicals applied.
The Future of Chemical Use
Exploiting advances in technology, weed control is evolving in much the same way that air-dropped munitions have gone from carpet-bombing in the last century to "smart bombs" today. Blue River Technology has developed a technology that promises to revolutionize chemical applications. This company has developed a program for a sprayer's computer to identify weeds and to turn on the appropriate nozzle, providing a small, short blast of chemical spray on an individual weed. Currently, sprayers used in bulk commodity fields spray the entire field to control weeds. If this precise technology were widely adapted to sprayers applying herbicides to bulk commodity fields, it could reduce the use of chemicals by 80 to 90 percent.
In an ideal world, farmers would not need to use chemicals to produce our food and fiber, but the reality is that without the ability to apply herbicides to control weeds, yields would decrease and farmers would be less profitable. The lower yields would result in higher food prices, an increased environmental footprint, and in cases of extreme environmental stresses, famine. Those are costs we can't afford.
Stuart J. Smyth is a professor in the Department of Agricultural and Resource Economics and holds the Industry Funded Research Chair in Agri-Food Innovation at the University of Saskatchewan. Henry I. Miller, a physician and molecular biologist, is a Senior Fellow at the Pacific Research Institute. He was the founding director of the Office of Biotechnology at the U.S. Food & Drug Administration.