If you ask around the watercooler, you’ll probably hear that the epidemic of children born with severely underdeveloped brains, known as microcephaly, is not caused by the mosquito-borne Zika virus, but by a Monsanto pesticide in the drinking water. Of course, this is complete nonsense.
The news spread like wildfire. Millions of gullible people, including celebrities like Star Trek veteran George Takei, accepted the claim that a recent spate of microcephaly in newborns in South America is not caused by the mosquito-borne Zika virus, as medical experts have hypothesised. Instead, it is to be blamed on Monsanto, the infamous maker of genetically modified seeds and herbicides. The internet gobbled this up. We have a bogeyman, and we have the torches and pitchforks ready!
The claim linking microcephaly to Monsanto was published by an Argentinian pressure group which calls itself Physicians in Crop-Sprayed Towns (PCST). The name appeals to the authority of medical doctors and betrays the group’s single-minded focus. It was quickly picked up by various news outlets, particularly left-leaning and environmental sites where they believe the silly notion that there is a difference between synthetic chemicals and natural substances, and have never heard of the dose-response relationship, or the certain safety factor.
According to PCST, “pyroproxyfen”, a larvacide used to control mosquitos, was added to the drinking water by the Brazilian government. This much is true, but that’s where it ends.
This larvacide is made, PCST says, by “Sumimoto Chemical, a Japanese subsidiary of Monsanto”. It goes on to claim that this substance, among several other mosquito-control chemicals, could be responsible for the outbreak of microcephaly.
“It is not a coincidence,” they wrote, that cases of microcephaly are being reported in areas where the larvacide is used. Moreover, since the World Health Organisation recommends these measures, it is all a conspiracy to “[generate] a business within a problem”, “that only benefit the chemical poisons companies”.
Predictably, the broken-telephone headlines on blogs and Facebook posts were quick to blame Monsanto and its weed-killer, RoundUp.
From the outset, it is clear that this claim is bogus. The chemical in question is actually called “pyriproxyfen”, a term deriving from “pyridine”. One would expect physicians to know this, and be able to distinguish it from the “pyro-” prefix, which refers to fire. It certainly has nothing to do with glyphosate, which is the active ingredient in the herbicide RoundUp.
As a matter of verifiable fact, Sumitomo, the supplier of the larvacide in question, is not a subsidiary of Monsanto, contrary to the claim by PCST. Although the two companies do work together on herbicides, the product under discussion here is a larvacide, which Monsanto neither makes nor sells.
Pyriproxyfen, first introduced 20 years ago, has been widely used for flea and tick control on pets, as aerosols, in bait, carpet powders, shampoos, and pet collars. Nowhere has it caused microcephaly. Ever.
After trumpeting the fact that the coincidence of pyriproxyfen and microcephaly cases is not a coincidence, the PCST report fails to point to any evidence other than coincidence. That’s like blaming autism on fluoridated water, or iodated salt, or on the growth of the internet, or the rise of organic food. One expects doctors to know that correlation does not imply causation. Muddying the waters even further, the report points to a number of different pesticides, including clorpyriphos and pyrethroids, as potential culprits, again without linking them substantively to birth defects.
Frankly, if scientists are correct in believing microcephaly to be a complication of the Zika virus, which is carried by the Aedes aegypti mosquito, you’d expect mosquito-control chemicals to be applied in regions where microcephaly occurs. The causation would work the other way around: mosquitos cause Zika virus, which causes microcephaly, and mosquitos also cause anti-mosquito chemicals to be used. As a result, you get pyriproxyfen and microcephaly together (which is the exact meaning of “coincidence”).
The PCST report approvingly quotes the Brazilian Association for Collective Health (Abrasco), which they allege demanded urgent epidemiological studies “taking into account this causal link [between pyriproxyfen and microcephaly]”. The awkward thing is that Abrasco denies ever having suggested such a link. In a statement to BBC Brazil, it said it “at no time said that pesticides, larvicides or other chemicals are responsible for the increasing number of cases of microcephaly in Brazil,” adding: “It is known that an uncertain scenario like this causes insecurity in the population and is fertile ground for the spread of untruths and content without any (or enough) scientific basis. The Abrasco repudiates such behaviour that disrespects the anguish and suffering of the people more vulnerable, and requests caution to researchers and the press in this grave moment, as all assumptions should be investigated before denying or confirming them.” Oops.
The PCST objects to chemical pesticides broadly, but flatly ignores scientific evidence and expert opinion that pyriproxyfen is highly specific to insects, and has no effect on mammals at normal doses. It is recommended by the WHO, in particular to be added to drinking water tanks and reservoirs to combat mosquito-borne illnesses such as Dengue fever, Zika fever and malaria.
The intake as a result of Brazil’s water treatment programme amounts to one 300th of the recommended maximum daily dose over a lifetime and animal studies have shown no adverse effects of any kind at levels 60 times higher than this maximum dose. If you drank enough water for pyriproxyfen to have any plausible effect, the water would kill you first.
They also ignore the potential benefits of mosquito-eradication programmes. In fact, the Aedes aegypti species that is spreading the Zika virus, which invaded South America from Africa, had been pushed back to the far northern reaches of South America by 1970, thanks to decades-long eradication programmes that included the application of DDT. After such pesticides fell out of favour in the 1970s, those programmes were weakened or discontinued worldwide. This led to the spread of the mosquito throughout much of Central and South America, which established a distribution much broader than before the eradication programmes began.
Even Rachel Carson, whose 1962 book Silent Spring is said to have launched the modern environmental movement and its obessession with pesticides, did not recommend discontinuing the use of DDT. She merely advised spraying as little as possible, instead of to the limit of our capacity. This sensible proposal has been twisted by groups such as PCST in their misguided and deadly war against using pesticides of any kind.
The PCST report is little more than hysterical conspiracy-theorising. It is no different from the predictable claims that vaccines somehow cause microcephaly (they don’t). Some people even claim that Zika is a “BIOWEAPON!” (note the strategic capitalisation and tactical exclamation mark), foisted on an unsuspecting world by British scientists who genetically engineered Aedes aegypti to die before being able to reproduce. According to The Ecologist magazine, the DNA from the modified mosquitos could have jumped to the Zika virus. This, as anybody with school-level biology will know, is impossible, since viruses do not have DNA. They have only single-strand RNA. Oops. (For a full debunking of the GM mosquito conspiracy, read this post by Christie Wilcox for Discover Magazine.)
If the Zika virus does cause microcephaly, which is the best working hypothesis on the recent outbreak, it poses a threat. To combat this threat, both from a policy perspective and in terms of how people behave in response, we need facts, not hippie-dippy hysteria about Monsanto and genetically modified mosquitos.
Issue-driven lobby groups who start out by lying about easily verified facts do not have a great track record of being right. It might be fun to spread internet rumours without checking them, or applying some elementary critical thinking, but jumping on that bandwagon can cause real harm – and not only to a perfectly innocent Monsanto. DM