By Kaley Beins
Over the past few months the mosquito-borne Zika virus has been dominating global health headlines, especially as researchers began linking it to microcephaly, a birth defect where babies are born with abnormally small heads and potential brain damage. Though Zika virus itself has fairly mild symptoms and is sometimes even asymptomatic, its connection to microcephaly created pandemonium. As the Center for Disease Control and Prevention (CDC) began issuing travel warnings and El Salvador recommended that women not get pregnant until the virus is controlled (estimated to take 2+ years), panic began to set in. The World Health Organization (WHO) declared a “Public Health Emergency of International Concern” scientists began developing a Zika vaccine and the world prepared for the next Ebola crisis.
Yet this past week some news outlets summarized a new Argentine report claiming that an insecticide, not Zika virus, is to blame for the increase in cases of microcephaly in Brazil. This report, written by doctors from the Argentine group Physicians in the Crop-Sprayed Villages, claims widespread exposure to the insecticide pyriproxyfen is the cause of these birth defects. Beginning in 2014, Brazil added pyriproxyfen to its water supply to prevent mosquito development. The report states that this insecticide is dangerous and is distributed by “a subsidiary of Monsanto.” (Note: the company that produces pyriproxyfen is Sumitomo Chemical, a Japanese company that is actually not a subsidiary of Monsanto, but has partnered with them in the past.)
The story told by Physicians in the Crop-Sprayed Villages has the makings of the next Erin Brockovich case, fueling the ongoing fights against Monsanto and validating the outrage leveled at chemical companies. There’s just one problem: it doesn’t appear to be true.
Unlike WHO and that majority of the scientific community that are continuing to do research on the potential link between Zika virus and microcephaly before saying anything definitive, Physicians in the Crop-Sprayed Villages published their report based on a correlation and only 12 sources (many of which were articles about dengue).
Although a definitive link between Zika virus and microcephaly still has not been found, a growing body of research appears to support the connection. Most significantly, a Brazilian study released this week found Zika virus in the amniotic fluid of babies with microcephaly, while previous studies have detected the virus in newborn saliva and urine. The CDC reported on a study that found the presence of Zika virus in the brains and placenta of babies that had died of microcephaly. Even when Zika virus was first explained in 1952 by G.W.A. Dick, he described how it affected the brain and the nervous system. The research has provided a mechanism, or process of causation, for Zika inducing microcephaly.
Conversely, the only mechanism the Argentine report provides is claiming that the insecticide pyriproxyfen is an endocrine disruptor (affects hormones and development) and therefore would affect pregnancy. However, pyriproxyfen affects the development from hatching to pupation, stages humans (and all animals with backbones) do not go through. Therefore, pyriproxyfen is highly unlikely to affect people.
Furthermore, even if we disregard the lack of science in the Argentine report, we can address their allegations. The main claim in the report is that the increased instance of microcephaly is found only in Brazil, where pyriproxyfen was used. While it is strange that Colombia does not yet appear to have increased rates of microcephaly, George Dimech, director of Disease Control and Diseases of the Health Department in Pernambuco, Brazil, stated that Recife, Brazil has had many cases of microcephaly, despite the fact that pyriproxyfen is not used there. Additionally, the 2013-2014 outbreak of Zika virus in French Polynesia has also been associated with central nervous system problems including Guillain-Barré Syndrome and microcephaly.
Various prominent scientists worldwide have disputed the allegations raised by Physicians in the Crop-Sprayed Villages. Dr. Ian Musgrave, a toxicologist at Australia’s University of Adelaide called their argument “not plausible,” while NIH Director, Dr. Francis Collins, referred to the report as “sketchy.” Environmental activist Mark Lynas called it a “conspiracy theory.”
Science is difficult and public health risks add to the confusion that further compounds the difficulty of scientific testing. There are still unknowns regarding Zika virus and its connection to microcephaly, and looking for alternative explanations and environmental factors is necessary in order to address the risks. However, publishing claims with little scientific support does nothing for environmental health. Unsubstantiated research is not only academically unethical; it allows the crucial field of environmental health to descend into pseudo science and conspiracy theory.
The Physicians in the Crop-Sprayed Villages report does make an important point that mosquito-borne viruses are much more prevalent in low-income communities because of fewer sanitation initiatives and less readily available potable water (a claim further substantiated by the Zika case in Texas). They connect the Zika outbreak to environmental justice. Environmental justice issues are significant and must be addressed, but jumping to conclusions without solid scientific backing hurts the movement. Without science to support our positions, industry and government can easily brush off our (very valid) concerns from pesticide use to landfill leaching. The Physicians in the Crop-Sprayed Villages report is an unforced error; it makes us look like we have an agenda other than protecting human health.
Science is our strongest weapon. Why are we shooting ourselves in the foot with it?