A vocal array of critics is demanding state health officials verify that aerial spraying of pesticide is an effective means of wiping out mosquitoes infected with the Eastern equine encephalitis virus.
The virus has infected seven people in the state this year and killed two. On Monday, a 7-year-old Marshfield boy with a bug bite was diagnosed with the disease.
The state Department of Public Health has blanketed 21 communities south of Boston with pesticide to prevent mosquitoes from spreading EEE, which kills more than 30 percent of humans who contract the disease and is at its highest level in three decades in Massachusetts.
“Aerial spraying is an unusual event and one we only recommend when the risk to human beings warrants it,” said Kevin Cranston, director of the state health department’s Bureau of Infectious Disease.
Environmentalists, organic farmers, and wildlife specialists say they are as sensitive as others to the public health threat posed by mosquitoes carrying the EEE or West Nile viruses. But state health officials should find a smarter solution than spraying pesticide from planes, they say.
From the epicenter of the EEE outbreak, Easton resident Kyla Bennett, director of the New England chapter of Public Employees for Environmental Responsibility, wants to know if the state made real headway by dumping pesticide on 478,308 acres in Southeastern Massachusetts, including her home and garden. Some communities, including Bridgewater, Easton, Norton, Raynham, Taunton, and West Bridgewater, were sprayed twice.
“I understand we are facing an extremely serious problem with mosquitoes causing illness and death, and that is an absolute tragedy,” she said in an interview.
“People see relatives or friends getting West Nile or EEE and dying. But what they don’t see is the long-term impact in 20 years of spraying these toxins that are getting in our water and on our vegetables,” she said.
Officials have repeatedly said the state’s chosen product, Anvil 10 + 10, a combination of sumithrin and piperonylbutoxide, has very low toxicity to humans and animals and breaks down rapidly in sunlight. It has proven itself a useful tool, they say.
“Following aerial spraying, we have seen a significant reduction in the volume of mosquitoes,” Public Health Commissioner John Auerbach said in a press release about a week after the July 20-22 operation. He said it wiped out approximately 60 percent of the mosquitoes in the areas hit.
But Bennett, a biologist and attorney formerly with the US Environmental Protection Agency, said the application of logic — not plane-delivered pesticide — is a necessary first step in dealing with a health scare. Aerial spraying may not be the smartest approach, said Bennett, who has a doctorate in ecology and evolutionary biology. She said pesticide droplets dispensed from a plane do not land on mosquitoes accurately, citing several studies that show mortality rates of 34 percent or below — even as low as zero — for mosquito populations in vegetated areas.
Aerial spraying targets only flying adults, not the eggs, larvae, or pupae, which means mosquito control lasts a week at most, she said.
“We should be working our butts off to find an alternative solution. I think the mosquito problem is only going to get worse. There has to be a better way than spraying,” she said.
According to Cranston, the Department of Public Health found high EEE infection rates among mosquitoes in southeastern Massachusetts appearing much earlier than in previous years. Since most mammal-biting mosquitoes live from spring until late summer, and can fly from 2 to 9 miles in search of nightly blood meals — typically from birds, horses, or humans — health officials anticipated a high risk of virus transmission to humans, he said.
Aerial spraying only has a transient impact on the mosquito population, but health officials use it to interrupt the life cycle, he said, adding the approach was a proactive response to signals of looming trouble. “This year turned out to be very bad. It is one of the worst years in the decade,” he said, adding state data show “you can reasonably say the spray helped drop the infection rate.”
A minimal-risk pesticide is effective when sprayed, as it was, with a low-volume, ultra-fine mist at night to hit mosquitoes and not “non-target” insects, such as honey bees. The state compared mosquito trapping data from before and after the aerial spray, he said, calculating the kill rate at about 60 percent.
Vegetation poses a challenge, but the operation takes place at peak wind and weather conditions so the spray makes contact with the highest possible number of mosquitoes. GPS-guided planes avoid water supplies and organic farms, he said.
Anthony Texeira, superintendent of the Plymouth County Mosquito Control Project, said “extremists” against aerial spaying misunderstand the necessity of it, not to mention the science behind it. While the control project focuses on spraying from trucks, Texeria said aerial application is far superior because it covers areas inaccessible by any vehicle.
Easton’s Hockomock Swamp, a prime breeding ground for EEE-infected mosquitoes, is about 16,000 acres, and spraying from trucks penetrates only 5 percent of it, he said. Or take the town of Middleborough, which is filled with wetlands. If a spray truck hits every street, only about 15 percent of the town is covered, he said. “We could do it by hand, we could do it by truck, or we could do it by plane. Which do you think is better? It’s obvious,” he said.
However, Jack Kittredge, policy director of the Massachusetts chapter of the Northeast Organic Farming Association, said it is foolhardy to spray chemicals over large areas without providing more information about the impact on humans and the environment. “What is the downside of this?” he said, wondering out loud what impact the pesticides will have on exposed fruits and vegetables.
“In the past, aerial spraying was a one-time kind of thing, but now it looks like it might happen more regularly because of the mosquitoes getting worse and we are concerned,” he said.
Since 1990, aerial spraying has occurred during five summers in Massachusetts — involving a single aerial spraying three of those times and two sprays set a few weeks apart the other times.
A recurring broad application of toxins is bound to affect the natural world, according to Kathleen Frisbie, founder of the Place for Wild Birds Inc.
“Aerial spraying is a knee-jerk reaction that is going to have consequences in the future,” said Frisbie, a federally licensed wildlife rehabilitator who has worked with birds in the Taunton area for 20 years.
“I see a kind of hysteria around this issue without enough reflection about the long-term consequences of spraying,” said Frisbie, who recently wrote to the governor to request he disallow it.
Back in Easton, Bennett said that on Aug. 8, she filed a public records request to secure proof that aerial spraying works. The state health department responded in a letter she received Friday. It offered Bennett access to 850 pages of documents for $1,050. The response was hardly the succinct, data-driven explanation the public deserves, said Bennett.Meg Murphy can be reached at email@example.com.