The alarming number of babies with microcephaly in Brazil and other countries is definitely a cause for concern. While each day more and more evidence grows that it is related to infection with the Zika virus, definitive studies are still lacking. This sadly leaves room for conspiracy theories and the one currently making the rounds is that a larvicide (a pesticide to kill mosquito larvae) called pyriproxyfen is causing the microcephaly. I’ve seen posts about the supposed link shared several times this weekend on Facebook and several news sites have irresponsibly elevated this to almost truth status.
Guess what I found when I clicked the links from the medical group making these claims? The same group that made the outrageous and incorrect claims about tampons being Monsanto-fueled vaginal cancer sticks.
The idea that pyriproxyfen could cause these birth defects is not biologically sound. First of all, pyriproxyfen works by interfering with the hormonal regulation of insect hatching from larvae, a cycle obviously absent in humans.
Secondly, it has been well studied and is poorly absorbed from the gastrointestinal tract/ The minute amount that is absorbed is rapidly excreted (eliminated). Scimex interviewed real toxicologists who study these chemicals and how they prevent mosquito borne diseases and if you want to know more it is an informative and concise read. Here is the best quote from Professor Andrew Batholomaeus, a consultant toxicologist from the School of Pharmacy, University of Canberra and the Therapeutic Research Unit, School of Medicine, University of Queensland:
Studies in rats and rabbits have shown pyriproxyfen to have no reproductive or developmental effects at doses up to at least 100 mg per kg of body-weight every day. This intake would be equivalent to an average human female consuming 6 grams of the compound per day. The acceptable daily intake of pyriproxyfen set by the WHO is 100 micrograms per kg of body-weight per day for a lifetime.
This equates to approximately 6 mg per person per day. By contrast the WHO recommended addition of pyriproxyfen to drinking water storage is a maximum of 10 micrograms per litre which would deliver a daily dose of 20 micrograms. A microgram is one millionth of a gram. Thus, the intake of pyriproxifen in Brazil from treated drinking water is of the order of 300 times lower than the safe limit set by the WHO.
All of this information is readily available to any genuine scientist looking dispassionately at the potential causes of the Zika virus outbreak or the rise in malformations in Brazil. Also readily available is the knowledge that the use of pyriproxifen is driven by WHO recommendations and not the marketing activity of any multinational or other corporation.
This last bit is VERY important, this kind of fear mongering could reduce the use of larvicides – the very thing that can help reduce the problem. Apparently the Brazilian State of Rio Grande Do Sul has suspended use of the larvicide.
The claims from the “Physicians in the Crop Sprayed Town” is either A) an attention grab to promote another agenda or B) a gross misunderstanding of biology. Any news site that promotes this link as worth “looking into” is contributing to the harm of those who live in areas rife with mosquito born illnesses.
A great follower on Twitter pointed out that Monsanto doesn’t even make the pesticide in question