What did Brazilian public health researchers really say about Zika, pesticides, and birth defects?

Claire Robinson looks at a Brazilian public health organization’s reported denial of a link between pesticides and microcephaly

Recently all hell broke loose after I published articles on GMWatch and in The Ecologist which flagged up the possible role of pesticides in the apparent surge in Brazilian babies born with abnormally small heads (microcephaly).



The articles were based primarily on a report by a group of Argentine doctors, Physicians in the Crop-Sprayed Towns, but it also took in a report by Abrasco – a group of Brazilian public health researchers who had condemned the strategy of chemical control of Zika-carrying mosquitoes. The researchers said this was contaminating the environment as well as people. And both reports seemed to point to a possible link between a mosquito insecticide (pyriproxifen) and the birth defects being attributed to the Zika virus.



The editor of The Ecologist received a torrent of invective after he turned down a demand that my article be retracted. The grounds for complaint was an apparent denial by Abrasco of a link between pesticides and microcephaly. According to the Wall Street Journal, Abrasco had “denounced the assertion of any link” and cautioned against “spreading untruths”.



A Brazilian press article quoted Abrasco’s coordinator Marcelo Firpo as stating: "We did not say that the larvicide [pyriproxifen] is associated with microcephaly.” He added that any suggestion that Abrasco had ever asserted such a link was a “misunderstanding”.



In contrast, the coordinator of the Argentine physicians’ group, Dr Medardo Avila Vazquez, stood by his group’s doubts about pyriproxifen’s safety. In fact, in his statement to the Wall Street Journal, he went further than anything in the group’s original report, saying, “We think it is likely that Pyriproxyfen is the problem.”

What does Abrasco’s report really say?

Whatever Marcelo Firpo may have told the press, Abrasco’s original report is a shocking and damning indictment, not just of pyriproxyfen, but of pesticidal approaches to mosquito-borne diseases like Zika.



Abrasco’s report says that the emergence in 2014 of the microcephaly increase occurred within certain “contexts and contingencies”, and that these must be assessed in any attempt to understand the phenomenon. It goes on to list them. Chief among them are the environmental degradation and poor sanitation that are the main focus of the Abrasco report.



The next is “The continued use of larvicidal chemicals in the drinking water of families for more than 40 years” – a strategy which the report says has failed, in that it has not resulted in a decrease in mosquito-borne diseases.



The report continues, “In 2014 a new larvicide, pyriproxyfen, was introduced into the drinking water”. Abrasco notes that the government’s own technical guidance document states that pyriproxyfen is “a juvenile hormone analogue or juvenoid, with the mechanism of action of inhibiting the development of insect adult characteristics (e.g., wings, maturation of the reproductive organs and external genitalia), maintaining an ‘immature’ form (nymph or larva), that acts as an endocrine disruptor and is teratogenic, inhibiting the formation of the adult insect.”



Of course, this does not prove that pyriproxyfen is an endocrine disruptor in humans. The Science Media Centre’s ‘expert’ brought in to discredit the larvicide hypothesis, Dr Ian Musgrave, is keen to suggest that it is not. But are things really that clear cut? That’s a subject I’ll return to in a subsequent article.



Abrasco goes on to demand “the suspension of the use of chemicals” (not just pyriproxyfen) and “the adoption of mechanical cleaning methods and environmental sanitation” to drive down mosquito populations.

Pyriproxyfen the tip of the iceberg

Abrasco’s report makes clear that in the regions where microcephaly is a problem, pyriproxyfen is just the tip of the iceberg. The people, particularly the poor, are being poisoned via multiple sources, with multiple chemical agents.



The report says that the widespread application of toxic insecticides and larvicides – sometimes in drinking water – has compromised people’s immune system by increasing their toxic load.



For example, Abrasco points out that an organophosphate insecticide, temephos (commercially known as ABATE®) was introduced in Brazil in 1968 as a larvicide in drinking water, especially in North and Northeast Brazil. Impacts on people's health have not been studied, according to Abrasco. The authorities continued to use it in spite of the fact that the mosquitoes have developed resistance.



Abrasco warns: “The damage to human health arising from the use of chemicals in mosquito control has not been properly studied in vulnerable populations, including public health workers. Its harmful effects are totally disregarded, such as the increased virulence of viruses, and the emergence of other diseases such as allergies, immunotoxicity, cancer, hormonal disorders, and neurotoxicity, among others.”



Abrasco denounces the use of mosquito "fogging" with known toxic chemicals such as Malathion. It calls this practice “a veritable health nonsense”, since “This product is an organophosphate pesticide considered by the International Agency for Research on Cancer (IARC) as potentially carcinogenic for humans”.



Abrasco dismisses as “absurd” the official assurances that, "The doses of larvicides are so low and of such low toxicity that we can put them in the drinking water without danger”. It also says that official advice on the amount of larvicide to be applied to drinking water is misleadingly based on the size of the container, regardless of how little water it contains, leading to potential dangers from unsafe concentrations being ingested.



Abrasco criticises the Pan American Health Organization (PAHO) and the World Health Organization (WHO) for supporting programmes of applications of pesticides “produced by a very lucrative business cartel”, even though “A simple consultation of the chemical safety data sheets of these products delivered by companies to public health authorities shows that these products, such as Malathion, are neurotoxic to the central and peripheral nervous system, and cause nausea, vomiting, diarrhea, difficulty breathing and symptoms of muscle weakness – including at the concentrations used in vector control.”



Anyone feeling reassured about the safety of pesticides yet?



As for biotechnological fixes like Oxitec’s sterile GM mosquitoes, Abrasco condemns them as inaccurate, unreliable and dangerous to ecosystems, as they focus “only on the mosquito, without taking into account the effects on non-target organisms”.



So any would-be pesticide defenders who take comfort from what Abrasco’s coordinator told the Wall Street Journal need to ‘man up’ and read Abrasco’s actual report – all of it. It doesn’t make for easy reading. But then the poisoning of people isn’t an easy topic.



Finally, one of the world’s leading virologists recently told The Guardian that there was “a strong possibility pesticides could be involved [in the microcephaly cases in Brazil] and this needed to be studied”. And Dr David Morens of the National Institute of Allergy and Infectious Diseases at the US National Institutes of Health called the pesticide hypothesis “plausible”, though he added, quite rightly, “We haven't heard enough scientific information to weigh in on whether it's real”.



What’s urgently needed is more science and more data – not a bar on legitimate study, imposed by those determined to prevent investigation of pesticides.