Viewpoint: Mexico’s ‘cut-off-your-nose-to-spite-your-face’ glyphosate ban — Why prohibiting one of the safest herbicides in the world will dramatically increase the use of a demonstrably more harmful alternative

Print Friendly, PDF & Email
Protest sign reading
Protest sign reading "Monsanto kills. If it's Bayer, it's not good." Credit: Alexa Gallardo/Flickr
It appears that the proposed Mexican government plan to ban all genetically engineered corn and the widely used herbicide glyphosate (Roundup) will go into effect by 2024 as originally ordered.

Mexican federal judge ruled on May 24 against a request by the National Farm Council to freeze the planned government ban. Judge Martin Adolfo Santos Perez’s ruling allows the executive ban order issued by President Andres Manuel Lopez Obrador late last year to proceed.

What are the science and trade policy implications of this ruling?

The National Farm Council (CNA), which represents many larger agriculture interests, warned that if the bans go into effect, food prices will jump and farmers will become less productive. It pays to be skeptical of the complaints of trade groups in response to regulation, but the CNA is probably correct. While some trade groups were warning that yields could plunge as much as 40%, a more realistic projection is probably in the ballpark of a 10-20% increase in food costs as more expensive weed control methods replace glyphosate.

Corn farmers in Mexico already face tremendous headwinds since NAFTA put them directly in competition with heavily subsidized, more productive farmers in America’s corn belt. During the first decade of the agreement, U.S. corn exports to Mexico quadrupled, while the price of domestically grown corn in Mexico crashed by nearly 70 percent. No longer able to support their families by selling their excess corn, an estimated two million farmworkers abandoned the Mexican countryside for the big cities, looking for work. When Monsanto’s patent on glyphosate expired in 2000, the cost plummeted. That put some farmers on a more equal footing. That’s now in jeopardy of reversal.

The recent mania to ban glyphosate tells us more about politics than science. Anti-biotechnology activists decided years ago to shift the focus of their campaigns away from genetically engineered crops, which are considered safe by the science community and even by skeptical environmentalists. They tactically shifted their target away from the technology itself to what they claim are the ‘negative externalities’ of intensive agriculture (which depends in part on the use of genetically engineered seeds): the use of herbicides.

Their primary target in recent years: the world’s most popular herbicide, glyphosate, long marketed under the Roundup name by Monsanto, now owned by Bayer. There is considerable irony to this tactic shift. Mexican activists, mimicking the strategies of activists globally, targeted one of the world’s most environmentally benign herbicides—which, in Mexico, will leave farmers with access to paraquat, 2,4-D, picloram + 2,4-D, and atrazine, with dicamba approved but not in wide use yet, while the far less toxic glyphosate is poised to be banned.

Does this make scientific sense?

A little back of the envelope math. In a 2017 paper, University of Wyoming weed scientist Andrew Kniss showed that while glyphosate accounted for 26% of herbicide applications on corn in the United States, it accounted for just 0.1% of the chronic toxicity hazard, while the other 76% of herbicides on corn accounted for the other 99.9% of chronic toxicity hazard. This makes the average non-glyphosate herbicide about 350 times more toxic than glyphosate, using that general metric.

Glyphosate accounts for about 45% of the Mexican herbicide market. One of the reasons it’s so popular is that it is so cheap. While Mexico has no centralized pesticide database, we can deduce that glyphosate is applied to more than half of the 13.5 million acres of corn in Mexico. If glyphosate is replaced with herbicides that are hundreds of times more toxic, it’s not clear why environmental groups would see that as progress. The Mexican government says that they will have a plan in place to by 2024 to replace glyphosate in a way that improves the situation. They currently do not have a plan.

Glyphosate ban in Mexico: potential impacts on agriculture and weed management (2021)

Toxic alternatives

While there is no evidence of any serious deleterious health impacts from glyphosate residues in our food or to applicators when used as instructed (17 independent global agencies have assessed the alleged health dangers of the herbicide), paraquat is an acutely toxic chemical requiring very careful handling by pesticide applicators and a fairly well-established connection to Parkinson’s disease, with regular exposure accounting for a two-fold increase in risk, according to a 2013 meta-analysis. Paraquat is so lethal that it is commonly used in farmer suicides. The EPA warns that a single sip can be lethal.

LD50 is a common measure of acute toxicity—the dose it takes to kill 50 out of 100 rats. The higher the number, the lower the toxicity. The LD50 of glyphosate is 5,000 mg/kg. The LD50 of paraquat is 125 mg/kg. Paraquat is 40 times more poisonous via overdose than glyphosate. Reference dose (RfD) is a measure of chronic toxicity, an estimate of the daily exposure to humans that is likely to be without appreciable risk of harmful effects throughout the entire lifetime. The RfD of glyphosate is 1.75 mg/kg. The RfD of paraquat is 0.0045 mg/kg. That’s nearly 400 times more hazardous than glyphosate.

Paraquat is still legal in the US, but is a restricted pesticide, requiring special training above and beyond basic pesticide applicator training in order to use it. Its use has gone up in recent years in response to glyphosate-resistant weeds but it still very a very small portion in the overall scheme of things. In 2017, the last year data are available, some 10 million pounds were applied in the U.S. with less than a million on corn. Meanwhile, 280 million pounds of glyphosate were applied in the U.S. with about 90 million on corn. As you can see from the chart above, paraquat is not applied in such a judicious way in Mexico. It is not restricted in Mexico despite the fact that the Mexican government classifies it as extremely toxic (red label) because it is one of the most acutely toxic herbicides available, while glyphosate is labeled slightly toxic (green label).

In an analysis published in the journal Pest Science Management in March 2021 in response to the government decree, weed researcher Ricardo Alcántara-de la Cruz and his co-authors argue that the ban goes too far and will likely have negative economic and environmental effects.

Regulatory agencies and researchers have called for global cooperation to develop strategies to regulate the incorrect use of glyphosate in order to avoid excess environmental pollution, because the benefit–risk ratio for this herbicide is one of the highest among all the available herbicides. We argue that, from the scientific and technical point of view, a glyphosate ban in Mexico will increase the use of other herbicides that will potentially increase the toxic load on the environment and the risks to health, since less toxic and inexpensive herbicides to replace glyphosate are unavailable. In addition, there is little or no government action towards development of viable alternative technologies that reduce the adverse impacts of weed management while maintaining current production levels.

… Mexico has set an example by banning glyphosate to reduce environmental impacts and health risks; however, it is striking that it does not have the same rigid stance in relation to other pesticides. There is a long list (more than 150) of active ingredients of pesticides used in Mexico with environmental impacts and health risks similar or more severe than those of glyphosate.

The authors were frankly baffled at what they considered the Mexican government’s naive rationale: the bans supporters expect random city-dwellers to suddenly abandon their lives and livelihoods in urban areas to move to distant farms in order to do the hand weeding that this ban would make necessary. Here are the skeptical comments in full:

The Mexican government, in the decree that bans glyphosate, also seeks to make weed control more mechanical and less dependent on herbicides. It unrealistically suggests that citizens who have migrated to urban centers return to their rural communities and carry out agricultural tasks. Given that manual weed control can cost up to MNX $4000 per hectare (USD $200), while with glyphosate it is around MNX $160 per hectare (USD $8) plus application costs ranging between MXN $250 to 500 (USD $12–25), weed control costs may be at least ten times higher in relation to current expenses.

Obviously, very few citizens will be willing to leave their non-seasonal and/or better paid jobs in the cities to make up part of the temporary and poorly paid workforce required for weed control. Further, manual weed control is labor intense, requiring skills that are developed over time, and which not everybody can efficiently carry out. Performing hand weeding on time at the proper stage of weed growth is more difficult. In addition, the simultaneous weed control in thousands of hectares is logistically unfeasible because it will be difficult to have sufficient workforce available in short periods of time.

It should be noted that the team writing this paper included three agricultural scientists and one employee of the Mexican agrochemical company FMC. Yet, their paper clearly does not reflect the perspective of the ag industry in general, which is apoplectic about the onerousness of this anti-glyphosate/anti-GMO policy. If anything, the proposal they lay out to regulate glyphosate use, while not as radical as the ‘ban biotechnology’ activists proposal, is very restrictive and precautionary—enough to give any booster of agrochemicals serious heartburn.

Related article:  IARC cancer agency mounts PR effort as probe of possible corruption grows

The political case against glyphosate

What’s driving this extremist embrace of a glyphosate ban? It’s not as if President Obrador has been known for his environmental bonafides. And perhaps that’s part of the problem. This move came after his powerful chief of staff resigned last December. Alfonso Romo had been the administration’s main liaison to business interests and was disliked by environmentalists who saw him as blocking initiatives they supported. The administration has been blocking the development of the private renewable industry in order to prop up the state-owned oil sector — a strategy simultaneously unpopular with business and environmental interests.

So, the environment hasn’t been a major concern of the president’s — there are pro-business and pro-environment players jockeying in various corners of the administration — but he did make a splashy, if shallow, campaign promise to ban glyphosate outright. This move was seen largely as a political response to the 2015 statement by the International Agency for Research on Cancer (IARC), an affiliate agency of the World Health Organization, that glyphosate is a probable carcinogen (using IARC’s definition of the term) to longterm applicators (though it concluded there was not conclusive evidence to conclude trace residues in food or casual home applications of the herbicide posed health threats).

Follow the latest news and policy debates on agricultural biotech and biomedicine? Subscribe to our newsletter.

The suspicion cast by the IARC’s statement on the safety of glyphosate was buttressed by a decades-old wariness of glyphosate’s connection to transgenic corn, seen as a threat to the cultivation of traditional landrace corn (a local cultivar or that has been improved by traditional breeding and production methods) by smallholder farms. Sadly, neither provides a solid basis for justifying a total ban. Let’s take them each in turn.

There has been controversy over how the IARC came to its conclusion, but that’s a minor issue. More problematic, it later came to light that an early draft of the IARC report which contained serious caveats, concluding that glyphosate is non-carcinogenic, were inexplicably left out of the final report. That’s a problem.

The larger issue, however, is that the technical meaning of what constitutes a ‘probable carcinogen’ was misconstrued—actively and purposely—by interest groups opposed to technologically-progressive agriculture. IARC undertook what is known as a hazard study, which measures the possibility that a substance could be harmful (under that rubric, such benign products as coffee and experiences as going to the barbershop were characterized as more likely than not to cause cancer by IARC).

In contrast, the 17 national and international agencies that have extensively evaluated and ultimately cleared glyphosate’s safety performed a risk analysis that shows little to no evidence that glyphosate is carcinogenic at real-world exposure levels. The gap between what was been said and what was being disseminated through less-than-judicious mainstream reports buttressed by social media campaigns orchestrated by cynical, anti-technology actors was huge. The disinformation message— The World Health Organization says that glyphosate causes cancer”—spread like wildfire. Years later, scientists, science journalists, and well-intention policymakers are still scrambling to set the record straight. To little avail.

glyphosateinfographic glp

Invasion of GMO corn?

The Mexican part of this sorry saga is even more distressing. In 2001, David Quist and Ignacio Chapela published the paper Transgenic DNA introgressed into traditional maize landraces in Oaxaca, Mexico in the journal Nature. The pair found that genes from Monsanto’s Bt and Roundup Ready corn had cross-pollinated into landrace corn. The genes had likely come from bootlegged biotech corn seed grown illegally nearby. But the findings were characterized by GMO opponents as a threat to the genetic diversity of traditional cultivars, which have tremendous cultural import in Mexico and are a crucial repository of a wide range of traits that could at some point become useful, even necessary for commercial corn breeding in the future.

Maize ears and seed of the Mexican landrace “Bolita”, collected in the state of Oaxaca. It is richly variable, showing white, yellow, red and black colorations. Credit: CIMMYT

Since then, the science has bounced around a bit as to whether cross-pollination actually happens. I don’t see why it wouldn’t. Regardless, the concern about specifically transgenic cross-pollination seems misplaced. The vast majority of Mexicans, if not their ruling class, are protective of small farmers and the role of landrace corn in the culture. The average corn farm in Mexico is about nine acres. The impulse to protect the genetic diversity of Mexico’s landrace corn is admirable and understandable. But it’s not at all clear why transgenes from commercial commodity corn — corn developed to maximize yield for animal feed, biofuels, high fructose syrup, etc. — is any greater threat to genetic diversity than the genes related to any other trait that confers fitness on a commodity corn variety. If you want to protect landraces from modernity, you need to protect them from cross-pollination from any and all commercial varieties of corn. But that is impractical and doesn’t carry the emotional impact of protecting them from transgenes.

Real threats

The threat to the purity of the traditional landraces isn’t from transgenic corn in particular, it’s from the proximity to commodity corn in general. Either it’s a confused misapprehension about genetic diversity or it’s a submerged concern about purity masquerading as something else. Either way, it’s a poor foundation for policy-making.

Mexico’s herbicide market is dominated by two pesticides with profiles very differently from a health and safety perspective: Glyphosate, the safest herbicide on the market; and the most dangerous herbicide in use globally—paraquat. It appears that politics, and cynical campaigns orchestrated by ‘environmentalists’ have prompted the government to foolishly chose to ban the safe herbicide and hope against hope that leaving the market open to dangerous paraquat, to dominate won’t blow up in everyone’s face. Mexico’s farmers, farmworkers, consumers … their citizens … deserve better.

Marc Brazeau is the GLP’s senior contributing writer focusing on agricultural biotechnology. He also is the editor of Food and Farm Discussion Lab. Follow him on Twitter @eatcookwrite

Outbreak Daily Digest
Biotech Facts & Fallacies
GLP Podcasts
Infographic: Trending green and going great — Every state in the US seeing decreased cases of COVID

Infographic: Trending green and going great — Every state in the US seeing decreased cases of COVID

The U.S. averaged fewer than 40,000 new cases per day over the past week. That’s a 21% improvement over the ...
News on human & agricultural genetics and biotechnology delivered to your inbox.
glp menu logo outlined

Newsletter Subscription

* indicates required
Email Lists