Naled Not Working in Miami Beach, FIU Analysis Shows

Naled Not Working in Miami Beach, FIU Analysis Shows
Photo by Karli Evans

Dr. Philip Stoddard, a Florida International University biologist and the mayor of South Miami, has released a study that shows that Miami-Dade County's aerial spraying of naled, a controversial neurotoxic pesticide, is not working to combat the Zika virus in Miami Beach.

Provided Stoddard's analysis is correct, the study shows that the county and the U.S. Centers for Disease Control and Prevention dumped a chemical that many scientists say is poisonous to humans and wildlife on a dense city, and received no positive benefit from the spraying. Stoddard's study is the first and only scientific analysis of Miami-Dade County Mosquito Control's efforts to combat Zika so far.

"Naled, a potent organophosphate adulticide applied aerially, produced a transitory suppression in Wynwood but lost efficacy after two or three applications," Stoddard wrote. "In Miami Beach, aerial application of naled produced no significant reduction of the Aedes aegypti population."

Reached via phone, Stoddard laid out the results of his study in no uncertain terms.

"I can tell you there is no evidence from the data that naled worked in Miami Beach," Stoddard said. "If I say 'worked,' I mean 'worked adequately.' I’m sure it killed some mosquitoes," but it had no effect on the overall population of Aedes aegypti.

In fact, he said, mosquito counts in Miami Beach actually increased after Miami Beach's last two rounds of naled spraying.

Naled is a controversial pesticide and known neurotoxin. It was banned in the European Union in 2012 after officials there said it posed an "unacceptable risk" to human and environmental health. Other neurotoxins include lead, botulinum toxin (also known by the brand name Botox), tetanus toxin, and drinking alcohol. The county's decision to spray naled has led to a series of protests across town and a growing national debate about insecticide use.

The Miami Herald reported yesterday that concerns over the Zika virus have taken a gigantic bite out of Miami's tourism economy. Public officials who are not worried about naled's environmental effects should still take Stoddard's study seriously, because the results show the county's highest-profile mosquito defense is doing next to nothing.

Stoddard said he has discussed his results with Miami-Dade Mosquito Control, county Mayor Carlos Gimenez's office, the entire Miami Beach City Commission, Gov. Rick Scott's office, and the CDC.

In the study, Stoddard measured how mosquito populations in both Wynwood and Miami Beach reacted after each spraying of naled, the organic bacterial larvicide Bti, and permetherin — a third insecticide. He used data obtained from both public-records requests and a Miami Herald Freedom of Information Act lawsuit.

Stoddard analyzed trap data in Wynwood from July 27 to September 9. His Miami Beach data stretched from August 21 to September 15.

In Wynwood, he wrote, naled killed numerous mosquitoes on its first and second sprayings. But the third and fourth sprayings appeared to have virtually no effect. Stoddard said he was unsure why this happened, but speculated that the mosquitoes might have quickly developed some kind of immunity to the insecticide.

Naled’s reduction of Aedes aegypti counts in Wynwood was transitory. Within three days the female Aedes aegypti populations were virtually identical to pre-spray levels (Table 1). Following some of the treatments, the mosquito populations three days later were higher than before the treatment.  


When active Zika transmission was first found in Miami Beach, CDC Director Tom Frieden said spraying aerially over Miami Beach was not possible. He then reversed his decision. Miami-Dade then began spraying naled from planes over the ocean, in the hope that the sea breeze would carry the pesticide onto the land.

In hindsight, Stoddard wrote, Frieden was right the first time:

When Zika was first identified in Miami Beach, mosquito control experts stated that aerial naled application was unfeasible in that neighborhood because buildings would interfere with even dispersal of the spray. “These tiny droplets are very much impacted by wind currents…. In cities with tall buildings, you’ve got wind currents that won’t keep the pesticide on the ground where it will do any good.” (J. Conlon, Technical Advisor to the American Mosquito Control Assoc., Miami Herald, 23 Aug 2016). Subsequently, the CDC and County decided to carry out aerial sprays on Miami Beach anyway. “The announcement [to spray naled] represented a reversal by state officials and the Centers for Disease Control and Prevention, who previously said Miami Beach’s dense urban environment and high-rise buildings made aerial spraying infeasible” (Miami Herald, 6 Sep 2016). The mosquito catch data from Miami Beach indicate that the experts’ skepticism was well-founded; aerial spray on Miami Beach had no positive effect and apparently missed most of the mosquitoes on the ground, though non-target effects were reported.


In a video interview Sunday, Harvard Medical School's Dr. Michael Callahan, one of the world's foremost Zika virus experts, also said unequivocally that spraying aerially for Aedes aegpyti mosquitoes does not work.

Though there was some early evidence that Bti — a live bacteria that attacks mosquito eggs — worked best to lower mosquito counts, Stoddard said it was too early to tell how well Bti worked because there was not an adequate control group to compare the Bti usage to other insecticides. But he said it was clear that the naled sprayed over Miami Beach is doing next to nothing to kill any mosquitoes.

"It's not getting to them," he said via phone. "I'm sure if you put a mosquito in a cage and sprayed it with naled, it would die," but the spraying isn't hitting them.

Instead, multiple residents have reported feeling ill from the effects of the naled spraying. On social media, residents have posted photographs of rashes and swollen eyes they say stem from the toxin. People have also published photos of dead bees, fish, and birds they say were killed by naled.

The CDC, U.S. Environmental Protection Agency, and Florida Department of Health say the amount of naled that Miami-Dade is spraying into the air is not harmful to humans. 

But on Wednesday, Dr. Claudia Miller, a professor emeritus at the University of Texas Health Science Center at San Antonio and a visiting senior scientist at Harvard's T.H. Chan School of Public Health, published a lengthy op-ed in the Miami Herald demanding the county stop spraying naled.

In the op-ed, she refuted the idea that small amounts of naled are "safe."

"The CDC says on its website that the use of Naled is safe because the amount used is small and because it has been used extensively in the United States since the 1950s," she wrote. "Having seen what chlorpyrifos, another organophosphate, did to human health, I take little comfort from the latter assertion."

Michael Capponi, a Miami Beach businessman and anti-naled activist, said in an interview that if Stoddard's study doesn't persuade the county to stop using naled, he's not sure what else will.

"This is the nail in the coffin," he said. "This is a public document that clearly states what happened to the mosquito count. Even if you take out all the rashes, all the complaints, and say it's all psychosomatic and everybody is crazy, you still can't win the argument to keep spraying."

Stoddard, meanwhile, says he was able to compile the data only after a lengthy fight with public officials to obtain any information about the mosquito traps. He said his initial public-records requests to the county and state were initially met with a stone wall.

"I know how to ask," he said. As mayor, "I get a lot of records requests myself."

He said the county initially told him that much of the mosquito trap information was not available. A CDC official then told him that she knew the information existed, which led him to file a second request with the county.

"I said, 'Either you guys didn't collect this data, or you're withholding it from me,'" Stoddard says.

His request was then approved.

Here's a copy of Stoddard's study, in full:

Update 9/24: The CDC said yesterday that a "one-two punch" of naled and Bti was essential to combatting the Zika virus in Wynwood. CDC Director Tom Frieden lauded a report released yesterday that showed both pesticides worked well in Wynwood, but cautioned that the same approach may not work in other areas. FIU's Stoddard says he is less optimistic about the CDC's spraying regimen.

Update 9/30: Here is Miami-Dade Mosquito Control's response to Stoddard's study.

FIU scientist Philip Stoddard released his independent analysis of the Wynwood mosquito trap data and the impacts of the aerial adulticiding and larviciding treatments in that area. Dr. Stoddard, who is also Mayor of the City of South Miami, has a long history of opposition to aerial and ground mosquito treatments using adulticides. He has not met with County officials to understand the totality of our mosquito control efforts in the face of the Zika challenge. While he is a PhD, he is not a research or medical entomologist who specializes in vector control or vector-borne diseases. Dr. Stoddard’s independent review and analysis of the data from the mosquito traps in Miami-Dade at this time is premature.


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