Monday 15 February 2016

Debugging the recent claim that Pyriproxyfen is the cause of microcephaly in Brazil...

I've copied the text below, in it's entirety, from the Science Media Exchange (Scimex; [4]) site run by the Australian Science Media Centre (AusSMC). I asked A/Prof Batholomaeus if he would be okay with this and he was.

The AusSMC had asked for local expert opinion on the recent claims by some physicians from Argentina that a pesticide, Pyripyroxyfen, could be causing microcephaly rather than Zika virus (ZIKV).

As those who read me know, I'm also not convinced that Zika virus is causally linked. For what that's worth. But should better data appear, I will certainly support them here.

This pesticide issue is the latest outcry generated by people seeing two events occurring at the same time - microcephaly and Zika virus epidemic/genetically modified mosquitoes/Tdap vaccine use - as linked events rather than just as events that have co-occurred in time and space. Just coincidence. The only way to rule out coincidence is to do a lot of hard work - which takes time and patience. And is hopefully being done. As ever though, it would be great for more of that progress to be communicated publicly.


Is a pesticide, not Zika virus, causing microcephaly?

Read some other comments from

Adjunct Professor Andrew Batholomaeus is a consultant toxicologist from the School of Pharmacy, University of Canberra and the Therapeutic Research Unit, School of Medicine, University of Queensland

"Pyriproxyfen is an insect growth regulator with a mechanism of action that is highly specific to insects. Pyriproxyfen is used on a wide variety of crops and is recommended by the WHO for addition to drinking water storage vessels to prevent the spread of deadly diseases such as malaria.

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.

The potential human health consequences of discouraging the use of pyriproxyfen in drinking water storage and other mosquito-reduction programs is catastrophic with potential deaths and serious disease from otherwise avoidable malaria, dengue and other mosquito-borne diseases numbered in at least the hundreds of thousands. If these reports and suggestions are motivated by anything other than ignorance and poor scholarship they are deserving of the most strident condemnation.

Journalists covering this story would do well to research the background of those making and reporting the claims as the underlying story and potential public health consequences may be far more newsworthy than the current headlines"


Further reading...
  1. Pyriproxyfen in Drinking-water
    World Health Organization
  3. Pyripyroxyfen general fact sheet
    National Pesticide Info
    rmation Center , USA
  4. The science media exchange (Scimex) 
  5. Australian Science Media Centre (AusSMC)

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