Posted: October 31, 2019
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Article SummaryOn October 16, 2019, I received an email from Michael Schulson, “a journalist for Undark Magazine, which covers science and society for a national audience from its headquarters at MIT.” He wanted to interview me by phone on a controversy in southwestern Michigan about aerial mosquito spraying against Eastern Equine Encephalitis (EEE). Instead of arranging a call, I sent him a brief email outlining my view: that both aerial spraying and EEE are small risks; that for understandable reasons spraying tends to arouse more public outrage than mosquito-borne diseases like EEE; and that in their effort to counter anti-spraying outrage public health officials tend to hype the (small) risk of mosquito-borne diseases while playing down the (also small) risk of spraying. Michael used portions of my email at the end of his article, which quite rightly focused on the particulars of the Michigan controversy.

Mosquito Spraying versus Eastern Equine Encephalitis: Two Small Risks Compete for Public Outrage

(Michael Schulson’s October 25 article in Undark Magazine,
based in part on this email, is available online.)

I’m currently in Shanghai, 12 hours ahead of the U.S. east coast. And it sounds like you’re on a tight deadline.

In lieu of a phone call that might be difficult to schedule, let me make a few off-the-cuff comments that you’re welcome to quote in your story if you find them useful.

number 1
I’m a risk communication expert, not a risk assessment expert, so I don’t have an expert opinion on the relative risk of EEE and mosquito spraying. But my very strong impression is that they are both small risks compared to many others that we all routinely face. I realize that there’s a current increase in EEE in the U.S., and a resulting increase in EEE newsworthiness. I suppose it’s possible that this increase is the tip of an iceberg, that EEE in the U.S. is on the verge of becoming much more widespread or much more severe or both. But absent real evidence that this is true, or even a consensus expert hunch that it might be true, EEE is way down on the list of U.S. disease threats. Similarly, it’s always possible that mosquito spraying is about to become a serious health hazard – because of a new insecticide, the cumulative effect of old insecticides, a synergistic effect with another substance, or some other about-to-be-recognized problem. But that seems pretty unlikely too.
number 2
Of course some people are getting very sick from EEE, and a few are dying. Some people (mostly applicators) also get very sick from insecticide exposures, and perhaps a few die. When I say these are both small risks, I don’t mean that they’re small in the lives of their victims. I mean that as far as we know so far they don’t have very many U.S. victims. So from a public health perspective, they’re small risks.
number 3
Mosquito spraying upsets more people than EEE. That may not remain true forever; it certainly won’t if EEE explodes into a public health crisis. But even when U.S. Zika fears were at their highest, fear of spraying was more salient to many people. That was true in Puerto Rico, which was way more affected by Zika than any U.S. state; it was true as well in South Florida. (I haven’t seen data on South Texas, the only other place in the continental U.S. with known autochthonous Zika transmission.) The same seems to be true now vis-à-vis dengue in South Florida: I see more concern in news about spraying than in news about dengue.
number 4
In my jargon, mosquito spraying arouses more outrage than EEE. Among the key differences in outrage terms is the natural-versus-industrial distinction. Natural risks provoke less outrage (concern, fear, anger) than industrial risks. EEE is natural; insecticides and the technology used to deploy insecticides are industrial. It’s also worth noting that a risky action tends to arouse more outrage than a risky inaction. Spraying is “doing something”; the alternative is to do nothing and hope you’re not infected with a mosquito-borne disease. The risks of doing something are way more salient than the risks of doing nothing. Also important: Spraying is highly memorable. You read the spraying schedules in the paper; you hear the planes; maybe you smell the insecticide. EEE, by contrast, is undetectable until you start experiencing symptoms. So it’s easier to put EEE risks out of your mind than insecticide spraying risks.
number 5
Perhaps in an effort to counter the superior outrage-arousing capacity of insecticide spraying compared to EEE, public health agencies have worked hard to insist that spraying is harmless while EEE is a serious imminent threat. I think in many cases public health agencies are overstating the risk of EEE and understating the risk of spraying. They tell stories about EEE victims without stressing how few such victims there are; they stress the rarity of insecticide poisoning without telling comparable stories about how horrible it can be. Often public health officials are helped in this comparative risk distortion task by the media. Journalists tend to defer to their public health sources, and tend to see EEE warnings and insecticide reassurances as a public service. (Quite often the media narrative is nerdy experts who know that EEE is dangerous and spraying isn’t, versus hysterical local activists who have been misinformed by anti-science websites.) It is at least possible that many people may sense this distortion on the part of public health agencies and the media, and the distortion may boomerang as a result.
number 5-1/2
I feel a need to say again that I think both risks are small. Nothing in this response should be interpreted as suggesting that I am urging people to worry about insecticides instead of EEE. I’m pretty confident all your readers routinely face more serious risks than either. My point is twofold: (1) At present, more people worry about the small insecticide risk than the small EEE risk. (2) Public health agencies are doing their best to reverse that priority, in part by overstating the (small) EEE risk and understating the (small) insecticide risk.
number 6
It’s also worth noting that public health agencies have a long history of frustrated efforts to convince the public to tolerate mosquito spraying. They are therefore inclined to seize on any newsworthy mosquito-borne disease as a teachable moment … even if what they choose to teach isn’t exactly the truth. The Zika epidemic, for example, affected mostly tropical places. New York City saw no autochthonous cases, and expected none; its only Zika cases were travelers from Puerto Rico and Latin American countries, who returned to NYC already infected and failed to pass the disease via a local mosquito to anyone else. Nonetheless, the New York City Department of Health and Mental Hygiene was very anxious to spray – not because of Zika but because of West Nile Virus. But Zika was a more salable rationale for mosquito spraying, and so DOHMH actively promoted New York’s nonexistent Zika risk as the excuse-du-jour for spraying. I have no idea if EEE is being similarly used in Michigan or elsewhere, but it wouldn’t surprise me.

That’s all that comes to mind offhand. Feel free to use what you wish (if anything).

Copyright © 2019 by Peter M. Sandman

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