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Everything you need to know about the zika virus in South Florida.

A Cure Worse Than The Disease? Despite Questions On Pesticide's Safety, Naled Spraying Continues

Kyle Holsten
County, state and federal officials tried to reassure concerned parents at an emergency meeting on aerial Naled spraying in Miami Beach in September 2016.

When he had a landscaping business, Bob Hartmann grew 200,000 orchids and thousands of other plants on his three acres in Southwest Ranches, about 15 miles southwest of Fort Lauderdale.


Credit Bob Hartmann
Bob Hartmann grew over 200,000 orchids and other plants in a shade house on his property. When he quit landscaping, he planted many of those plants around his house.

But then Hartmann quit landscaping to focus on his career in information technology. And about 10,000 of his plants — cypress trees, hibiscus, pineapple, fire brush and royal palms descended from the ones lining Biscayne Boulevard in downtown Miami — went into the ground around Hartmann’s house. 

“Most of these trees are grown from seed, so what you see is an extension of my family,” Hartmann says. “We spend a lot of time in the yard.”

But earlier this summer it was impossible to enjoy Hartmann’s homegrown subtropical paradise. Heavy rains had blown black salt marsh mosquitoes from the Everglades onto his property, and more than a few seconds outside was unthinkable. Hartmann says when he’d step outside he’d have 20 mosquitoes on his arms within seconds.

“They’re on your arms, you hear them on your back, your neck, buzzing in your ears,” he says. “You just want to swat at your face, swat at your head, swat at your ears and run like heck into the house.”

“It was horrible. Until they sprayed.”

On June 29, Broward County mosquito control officials conducted aerial mosquito spraying over Southwest Ranches. They used a pesticide called Naled, and Hartmann says that’s helped end the mosquito “horror story” he and his family have lived in recent weeks. “When they’ve done aerial spraying, it makes a significant difference.”

Credit Bob Hartmann
Bob Hartmann and his family enjoy spending time on their patio. But since the property is about a mile from the Everglades -- where most salt marsh mosquito breeding takes place -- Hartmann says being on the patio is unbearable if Broward officials don't spray for mosquitoes.

In fact, Hartmann says, he and other Southwest Ranches residents at a recent community meeting told mosquito control officials they were concerned that the county wasn’t doing enough aerial spraying in their area.

Elsewhere in South Florida, it’s a different story.

Mia Carlson comes to the door of her South Miami home with her almost-3-month-old daughter, Penelope, in her arms, and her dog, a corgi-chihuahua mix named Woody, barking at her heels.

She settles Penelope in an automatic baby rocker and lists her unanswered questions about Naled:  For how long and how often has it been used in populated areas? Why hasn’t it been studied more? And especially, could it hurt Penelope?

Credit Courtesy of Mia Carlson
Mia Carlson and her daughter Penelope, shortly after Penelope's birth. Carlson discovered she was pregnant during the 2016 Zika outbreak and went to Ohio for much of her pregnancy -- to avoid both the virus and the pesticides being used on Zika-carrying mosquitoes.

“It makes me concerned for children who are mobile, outside, touching things, putting things in their mouth,” Carlson says. “I would like them [officials] to maybe pump on the brakes and maybe wait a little bit and be a little less aggressive in the chemicals they’re using.”

In very large doses — massively larger than the quantities to which people are potentially exposed through aerial spraying — Naled can cause muscle spasms, seizures and severe neurological and respiratory problems.

Carlson says the risk she sees from using Naled outweighs the reward of mosquito control. That’s a common concern in South Florida: two Miami Beach residents recently filed a request in federal court to stop Miami-Dade County from spraying the pesticide.

“They [county officials] are receiving all of these complaints about mosquitoes being a nuisance, and their answer to that is to go ahead and use what is probably the strongest chemical available,” Carlson says. “I think that’s a very aggressive move.”

A risk to children?

The controversy over Naled erupted in South Florida in September 2016, when residents concerned about pesticide exposure protested Miami-Dade County officials’ decision to use the pesticide against the mosquitoes that were transmitting the Zika virus in Miami Beach.

Naled isn’t the most effective way to control the main species of mosquito that carries Zika in South Florida, the Aedes aegypti. But it was a public health emergency: Zika can cause severe, permanent brain damage in infants infected before birth. So, local officials say, they worked with the U.S. Centers for Disease Control and Prevention, the Florida Department of Agriculture and Consumer Services, and the Florida Department of Health to attack the mosquitoes with every weapon in their arsenal.

"Based on guidance from our federal and state partners, we employed alternating... larvicide applications [to kill mosquito eggs] and adulticide treatments using Naled," Gayle Love, a spokeswoman for Miami-Dade mosquito control, wrote in an email. "This treatment was very effective at decreasing the Aedes aegypti population in the [Zika] transmission zones."

So far this year, there’s no local transmission of Zika taking place in Florida, according to the Florida Department of Health and Gov. Rick Scott. Officials say they’ve stopped using Naled against Aedes aegypti mosquitoes. 

Credit Kate Stein / WLRN
Dozens of people protested officials' decision to use Naled against mosquitoes carrying the Zika virus in Miami Beach in September 2016.

But they’re continuing to use it on the salt marsh mosquitoes, which don’t transmit diseases in humans. Broward, Miami-Dade and Palm Beach counties and the Florida Keys Mosquito Control District have each aerially sprayed Naled at least twice this year.

That’s despite a recent study linking the pesticide to possible developmental delays in infants.

The study by researchers at the University of Michigan and two Chinese universities looked at the effects of Naled and 23 other insecticides on 199 infants in China. Researchers tested umbilical cord blood for traces of the pesticides and tested the infants’ motor skills at six weeks and nine months. They found that at nine months, infants with high Naled exposure had slightly lower visual-motor skills and fine motor skills than infants who had low exposure.

The possible link between Naled and developmental delays is particularly concerning because through aerial spraying there’s potential for widespread exposure, said Monica Silver, a pediatric environmental epidemiologist and one of the study’s authors.

“Early life exposure has the potential for long-term effects in children,” more so than adults, Silver said. “Their brains are rapidly developing, all their organs are rapidly developing. So you just want to take that into account.”

But, Silver added, a lot more research needs to be done before a definite link can be made between Naled and developmental delays. The study was relatively small: It looked at only 199 infants. Silver said researchers also don’t know the quantity of Naled to which the infants were exposed, whether it was a one-time exposure or multiple doses, or how exposure occurred. (They hypothesize it was through food, not mosquito control.)

And, since babies develop at different rates, it’s possible the “deficits” captured in the study don’t even exist. That’s according to Robin Dole, chair of the Pediatric Specialty Council for the American Physical Therapy Association.

Dole said the method researchers used to evaluate the babies’ development — the Peabody Developmental Motor Scales, Second Edition — gives a range of what’s “normal” for an infant of a given age. For a 9-month-old, she said, a low visual-motor score is 4 and a high score is 81. An average infant would have a visual-motor score of between 40 and 45.

“So up to a five-point change might just be typically variability,” she said.

But the study found just half a point average difference in visual-motor skills between infants exposed to Naled and the standards for their ages.

Meaning, “this ‘difference’ is potentially not a difference,” Dole said.

The Peabody scales also evaluate infants on several types of motor skills beyond visual-motor. The infants exposed to Naled showed possible deficits in two other skill areas: fine motor skills and a measure called the fine motor quotient. 

But again, those “deficits” are differences of about a point on scales where a one-point difference could be normal.

“Just because we can pick up a difference in score — does it have meaning?” Dole asked.

Regulatory gaps

A lot more research needs to be done to confirm a possible link between Naled and motor skills deficits. But researchers say the study is still important, for several reasons. First, if the infants in the study are re-tested when they’re older and show possible motor skills deficits again, that would be a major red flag.

Credit Kyle Holsten / WLRN
A Miami-Dade County truck transporting an insecticide to be used in aerial spraying over Miami Beach in September 2016. Miami-Dade officials say they worked closely with state and federal officials on a mosquito control strategy during the Zika outbreak. They alternated spraying with an organic larvicide to kill mosquito eggs and aerial spraying with Naled to target adult mosquitoes.

And evidence is mounting that pesticides with similar chemical compounds to Naled’s — other pesticides of the type known as “organophosphates” — can cause neurological damage. That’s according to Kim Harley, who studies the effects of pesticides on pregnant women and their children at the Center for Environmental Research and Children’s Health at the University of California, Berkeley.

“One study can’t prove something,” Harley said. “But the fact is, in this class of organophosphate pesticides we now have quite a few studies that are using slightly different methodologies, that are using slightly different ways of measuring pesticide exposure, different ways of measuring brain development in children, and a lot of these studies are starting to show similar results.”

Harley says there just isn’t that much research on Naled, so much of what researchers and regulators know about Naled is actually based on studies of other organophosphate pesticides, not on studies of Naled itself.

“We’re trying to do regulation and risk reduction with a lot of holes,” Harley said. A lot of what researchers know about Naled, she says, comes from research on another pesticide called chlorpyrifos, which was slated to be banned by the Obama-era EPA after studies linking it to developmental delays, including motor skills problems.*

In an email, a spokesman for the Environmental Protection Agency said the EPA uses Naled-specific data to regulate Naled. When asked to specify which data, he did not elaborate.

A nationwide protocol

EPA guidance on Naled has a trickle-down effect: State and local officials rely on that guidance to decide how and when to use the pesticide.

Alina Hudak is the Miami-Dade deputy mayor who oversees county mosquito control. When asked why the county has continued to use Naled despite a possibility — however remote — of a link to developmental delays, she said local officials are following advice from state and federal officials.

“We obviously continue to monitor anything coming out of the EPA,” Hudak said. “We work very closely with the Florida Department of Agriculture. They have reviewed the studies that are being referenced and they have found no reason to be concerned.”

Credit Logan Riely / Miami Herald
Miami Herald
A contractor for Miami-Dade County conducted mosquito control aerial spraying over Wynwood and the surrounding areas on Aug. 4, 2016.

  Spokespeople for Florida’s Department of Agriculture and Department of Health say they get their guidance from the EPA, too. So unless EPA guidance on Naled changes, or an equally effective alternative becomes available, it’s likely Naled will continue to be used to control salt marsh mosquitoes.

“Please understand that this is a very small quantity. This is a protocol and a program that is used through the entire country,” Hudak said.

The EPA periodically reviews its guidance on pesticides, and Naled is up for that routine review this year. The EPA spokesman wrote that the agency is evaluating the study of Chinese babies to decide if it should be taken into consideration.

A draft reassessment of Naled’s risks is scheduled for release before the end of 2017. After that, the public will have 60 days to comment.

Meanwhile, about a month after the initial spraying, Hartmann says Southwest Ranches has begun to see a resurgence in the mosquito population.

*On March 29, the EPA’s new administrator, Scott Pruitt, denied a petition to ban chlorpyrifos. In an EPA press release, he said: “By reversing the previous administration’s steps to ban one of the most widely used pesticides in the world, we are returning to using sound science in decision-making – rather than predetermined results.”

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