Enlist Duo: Dow Walks Into Monsanto’s Footsteps

In October of 2014, the U.S. Environmental Protection agency announced that they would register Dow Chemical’s Enlist Duo, a herbicide treatment system consisting of 2,4-D and glyphosate along with seeds of crops that were genetically modified to resist the pair of herbicides. It was a controversial decision which prompted a lawsuit. Slipping under the radar is that a year earlier, Health Canada also gave the product its approval without any of EPA’s restrictions. Adding more nuance to the issue is that since the EPA decision, of one of Enlist’s ingredients has been reclassified by the International Organization for Research on Cancer.

1. What is Glyphosate?


Roundup’s use soared after introduction of foods genetically modified to resist glyphosate

Although it had been made 20 years earlier, glyphosate was rediscovered by Monsanto in 1970.




The compound kills plants because it interferes with a plant enzyme and prevents the synthesis of certain amino acids. Its use skyrocketed after Monsanto, the manufacturer of Roundup (commercial name of glyphosate), also genetically engineered corn to be resistant to the herbicide. In fact, mostly due to its application in corn and soy fields, its use went up by more than a factor of 10 in about 2 decades (see graph).

In a current example of natural selection, by the mid 2000s, morning glory, amaranthus species, lambs quarters, giant and common ragweeds, horseweed, and velvet leaf all developed resistance against glyphosate. The natural variants or perhaps mutants that were not killed by Roundup went on to reproduce, and eventually their genes became those of the majority. The resistant ” superweeds” are now spread over 70 million acres in the US alone. To combat the resistance, Dow Agrosciences used genetic modification to protect crops against both glyphosate and 2, 4-D, which they include in their new Enlist Duo weed-killing mix.

2. What is 2,4-D and How Has Glyphosate Been Classified?

2,4-D, short for 2,4-Dichlorophenoxyacetic acid, is a synthetic auxin, a plant hormone which overstimulates and especially kills broadleaf plants. Critics of Dow point out that 2,4-D was an ingredient in the health hazard known as Agent Orange, a notorious defoliant used in the Vietnam War. Dow defends itself by pointing out that Agent Orange also had 2, 4, 5-T, which at the time was contaminated with dioxins. Certain dioxins are in the same class as tobacco smoke and benzene; they are proven human carcinogens. However, 2,4-D is not in that category of compounds. It is a possible carcinogen, classified as 2B, safer than class 2A, which includes probable carcinogens. But  as reported  in the Lancet in March, 2015, the problem is that Enlist‘s other ingredient, glyphosate, has just been placed in class 2A by WHO’s cancer research division.


3. EPA’s Restrictions and is the Duo Approach Ecological?

The EPA correctly points out that the variety of 2,4-D is an ester of lower volatility (it’s a quaternary ammonium salt called 2,4-D choline),

Choline quaternary ammonium salt  of 2,4-D, formed easily by mixing choline  hydroxide with 2,4-D in water

Choline quaternary ammonium salt of 2,4-D, formed easily by mixing choline hydroxide with 2,4-D in water

lowering the amount that will end up in groundwater. They ordered  a 30-foot in-field “no spray” buffer zone around application areas. It has also banned use when wind speeds are over 15 miles per hour.  EPA will also apparently monitor the herbicide for resistance and reevaluate the product after 6 years, instead of granting the usual 15-year time frame. But since their decision was made before the WHO’s reclassification of glyphosate, they have given Dow the authority to toss more of a questionable compound into an already stressed ecological stew. The whole idea of having the same company market a package of herbicide and GMO-compatible seeds seems to be more about short-term economic gains and less about using science to feed the world in an ecological manner.


In 2017, EPA amended the registration to allow use of Enlist Duo on genetically engineered cotton in those 15 states and extend the use of the herbicide on GE corn, soybean and cotton to an additional 19 states. They also stipulate that Enlist Duo cannot be applied when wind speed is over 15 mph. One cannot help wonder how often that recommendation is violated, given that 15 mph is not much of a wind, just 4 on the Beaufort scale, just enough to move small branches on a tree.


My Favorite Nobel Prize and Why a Flower Beats Any Perfume

Capable of detecting faint traces of smoke, the nose can be a life saver.  Sensitive to esters of fruits and flowers, it can be a source of pleasure. Through its associations with the hippocampus, it can serve as a unique gateway to episodic memories. When the brain gathers information through the nose, it does not rely on the electromagnetic spectrum. Like touch and taste, smell is a sense that’s in direct contact with matter.

Decades ago, some chemists imagined that through its shape and functional groups, a particular odiferous molecule was interacting with a single type of receptor. But the simplistic speculation had its shortcomings. The mechanism’s truth turns out to be far more intricate.

Richard Axel and Linda B. Buck won the 2004 Nobel Prize in Physiology for their discoveries of odorant receptors and the organization of the olfactory system. Independent of each other’s work, they experimentally found evidence for the following bouquet of ideas:

(1) For every olfactory receptor cell, there is an odor-receptor, coded by a single gene. The related genes(about 400) that code for olfactory receptors probably make up of the largest gene families.odorants

(2) One receptor can respond to a variety of similar odorous substances, For example, receptor 2 in the diagram can interact with both hexanol(B) and heptanol(D). But the coupling-reaction from one molecule will not necessarily be identical in intensity to that of the other.

(3) There could be a main component of a particular smell, but more often than not, the smell will often be triggered by two or more compounds. For example a rose contains three major constituents: two different ketones and cis-rose oxide. But there are hundreds of more compounds, all of which contribute to its its fragrance. (In 5 decades, the number of odorous compounds discovered in the rose increased by a factor of 20.)

Now here comes my favorite part:

(4) A specific combination of receptor-interactions is needed for a stimulus, so a given receptor can play a role in various smells. Thus not surprisingly, for about 400 receptors, there are about  10 000 or so different odors that we recognize. For example, in the diagram, hexanol’s interactions with receptors 2 and 6 leads to a sweet, herbal smell.  The same receptors along with receptor 5, when interacting with heptanol, lead to a smell that’s sweet and violet-like. Returning to the rose, each of three main fragrant compounds is responsible for a key combination. Our perception is based on a mosaic of at least those three receptor-combinations along with a bouquet of all the other fragrant components of the rose.


A rose and especially a citrus blossom are far more interesting than the most expensive perfumes. Flowers do not spray compounds into a mist; often the molecules are secreted from the surface of petals and other parts; at times they start as liquid and evaporate when air collides with them.  It takes thousands of flowers to yield a few hundred grams of the essential oils used in commercial products. In cheaper perfumes only a few of the fragrant compounds are synthesized. Instead, a single flower is sufficient to excite our senses. It synthesizes its perfume on location and does not have to deal with preservation issues.

Cheese_limburger_editThere is more odor science to to be revealed on the matter, to be sure. The year after the prize was awarded, after using vaporized odorants delivered either through the nose(orthonasal) or the mouth(retronasal), investigators measured brain responses with fMRI. They were not the same. This explains the Jekyll and Hyde signatures of the durian fruit and Limberger cheese. Both smell bad when they are not in your mouth; durian smells like rotten onions and Limberger is produced from the same bacteria that make sweaty socks reek. But while these foods are being ingested, the unpleasant smells are not perceived and replaced by a pleasant blend of taste and alternate aromas.

Gluten-free Diet Exposes People to More Arsenic

Fear rarely leads to rational discussions. If not driven by fear, we often adopt unusual diets, perhaps out of an attempt to control our lives in a confusing world. Regardless of the root cause, our world has people who take advantage of either case. Consumer Reports’ January 2015 article The Truth About Gluten does a good job exposing those who profit from some unfounded suspicions about gluten.

Gluten is a protein composite found in wheat, barley and rye. It’s what makes dough elastic; it can trap carbon dioxide and make dough rise; when absorbing the right amount of hot water, a gluten network also traps swelling starch granules, creating the al dente texture of perfectly cooked pasta.

But to the 1% of the population who suffer from caeliac disease, gluten must genuinely be avoided at all costs. An enzyme modifies gluten components or similar molecules found in foods and then the immune system attacks the villi of the small intestine, interfering with nutrient absorption.CeliacMechanism

It’s unlikely that gluten is fully tolerated by the other 99% of the population, but because gluten-free diets have become a fad and ripe for commercial exploitation, it’s extremely likely that many non-caeliacs avoiding gluten are being deceived. For example, even beauty products carry non-gluten labels, and just as 7up fed on a caffeine-fear decades ago—promoting itself as caffeine-free when it never contained the compound—sales of potato-chips disingenuously glutenFreelabelled as “gluten-free” (they have always been naturally free of gluten) have soared by 456% between 2012 and 2014. Compared to new cereals for people, twice as many gluten-free pet foods were launched in 2014.

Here are more Consumer Reports findings:

(1) Gluten does add pleasant texture and taste to foods. To compensate, manufacturers add more sugar and even fat to gluten-free foods.

(2) Gluten-free foods are more expensive than their counterparts.

(3) According to an EPA 2009-10 study, on average 17% of a person’s dietary exposure to inorganic arsenic, a carcinogen, comes from rice (brown rice from Texas being the most contaminated). Gluten-free foods often use rice as a substitute for wheat. As a result gluten-free diets unnecessarily expose many people to more arsenic. How much? Well, most rice is in the 2 to 9 micrograms per 45 g serving ( 2 to 9ug/0.045 kg = 44 to 200 ppb or parts per billion) which is a much higher concentration than the legal limit of arsenic in drinking water at 10 ppb). The rice industry of course plays the “safe-level” card, acting as if arsenic is the only carcinogen in the environment.

There are other environmental sources of arsenic aside from water and rice. Garden vegetables can contain elevated levels of arsenic if they’re grown next to CCA-treated wood, which was sold before 2004. A key study leading to the ban of such wood treatment was conducted by David Stillwell. What I find interesting from a chemical point of view is that it seemed initially that CCA would not leach out when the product was first introduced into the market. The wood had originally been tested with tap water. But in the field, the treated wood was exposed to acidic precipitation, and at a lower pH, the arsenic compounds were more soluble. As I revealed in a University of Waterloo publication,  I used a modified Gutzeit test to convince myself that this is indeed true. How much arsenic was found in food also depended on the part of the plant. Roots and tubers concentrated the most, so carrots generally contained more than tomatoes, all other variables being equal. Of course, other soil components also played a role along with how much stain was applied to the treated wood. Quality stains helped prevent leaching of arsenic.