Spraying to Stop West Nile - Is It Safe?
Not trying to be obnoxious. This is not I-told-you-so. But I did told you so.
In a column published December 29, I did point out that North Texas was taking all kinds of wild chances with its water supply by refusing to adopt the type of strict safety measures in effect in the Great Lakes region and in Southern California to protect lakes and rivers from invasive zebra mussels.
When I told Jeff Alexander, a Michigan journalist with an award-winning book on the topic, what was going on here, he said, "To me that just seems like Russian roulette at the highest levels."
After that? Radio silence. Who cares? Not a peep from City Hall.
So we played Russian roulette. And we lost. A couple weeks ago a story in The Dallas Morning News reported that "Zebra mussels have invaded Lake Ray Roberts and are expected to wreak havoc on drinking water systems in Dallas, Denton — and eventually cities along the entire Trinity River system."
Havoc. That's a bad word when applied to massive public drinking water systems.
So I come back to you now on another topic — West Nile mosquito pesticide spraying. I am not here with a big screaming prediction of doom but with the suggestion that maybe we might want to think a little bit about what we're doing, instead of ignoring possible perils the way we did with zebra mussels.
I asked city of Dallas spokesperson Frank Librio what research the city has done on possible biohazards associated with the chemical compound it is now spraying throughout our neighborhoods at night to combat West Nile. I asked because I was aware that both the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation have just come out with much tougher restrictions.
Librio told me he would check with the city staff people involved. After several days, he emailed me back: "The product is considered safe when used according to manufacturer's label."
They read the label. Their research consisted of going into the chemical store like some dude off the street, picking up a bottle of the stuff and saying, "Yup, looks pretty good."
There's a big problem with that. Dallas sprays a compound called Aqualuer 20-20, whose active ingredient is a chemical called permethrin, a member of the pyrethroid family of compounds. If permethrin were being sprayed by anybody but a public health authority, extremely strict controls on its application would apply. No one else would be allowed to drive down a street and spray this stuff indiscriminately into the air.
Public health authorities, however, are exempt from those restrictions. I spoke to Lea Brooks at the California Department of Pesticide Regulation, because their new restrictions on Aqualuer 20-20, put in effect just a week ago, are even tougher than the new EPA standards.
But Brooks told me that in California, as here, public health authorities get a pass from those restrictions. "This product is allowed under an exemption as a public safety issue," she said. "I know in California and probably in other states the health authorities here have a lot of authority when it comes to protecting the public health."
I asked if in their review her agency had come up with any evidence that spraying permethrin into the air in the way it's done as mosquito control actually does any good at cutting back West Nile infections in human beings. She said pesticide manufacturers supply the state with their own "efficacy data."
That was really what I wanted to find out from Librio. It's two questions. Do you know what the biohazards are? Do you have proof that it's worth our while to run those risks?
The reason to ask those questions is a growing body of negative opinion on both points.
Sheldon Krimsky, a professor of urban and environmental policy planning at Tufts University in Massachusetts and author of several books dealing with public policy and environmental risk, was one of a panel of experts, including people at Harvard and MIT, convened to study pyrethroids after the city of Cambridge, Massachusetts, began spraying them in 2000. Cambridge has not sprayed since that panel issued its report, even though West Nile has been found there.
Krimsky says a principal reason the panel recommended against spraying pyrethroids was that the known risks were not outweighed by any evidence that spraying did any good. "There was no evidence that the aerial spraying really reduced the mosquito population," he told me.
In 2008, a student at Yale working on a combined master's degree in public health and business authored a study, later reported in the Yale School of Public Health newsletter, which found that pyrethroid spraying in Sacramento County, California, in 2005 had reduced the incidence of West Nile virus found in humans. The author claimed that his study had been "peer-reviewed" by experts in the field.
But that same year the Pesticide Watch Education Fund published its own knock-down of the Yale student's study, reporting that they had made open-records demands for underlying data and for the claimed peer reviews of the study and had received nothing in response. In the meantime, they showed in their own article that the Yale grad student had started measuring the incidence of West Nile in California after that year's West Nile season had begun its natural seasonal decline. He then gave credit for the seasonal decline to the spraying.
The threat here from West Nile disease is real. In one recent week, the number of confirmed human cases of West Nile disease in North Texas nearly doubled, from 68 to 123, while county health officials predict by year's end we will exceed the previous record annual death toll of four set in 2006.
The city of Dallas, in addition to its spray program, is attacking the problem in many ways accepted as effective and without human risk by just about everybody — introducing larvae-eating fish into bodies of standing water, draining standing water where feasible and encouraging homeowners to do the same and urging the public to use personal mosquito repellents outdoors.
But Dallas also does the spraying, justified as safe by Librio because of product labels. You have to wonder which label he's reading.
The label on the outside of the product itself just tells how to spray it. But if anybody bothered to read all of the new EPA labeling requirements for pyrethroids, I have to think they'd be a lot less cavalier.
Permethrin is a neurotoxin. Mainly what the EPA says about it is that the EPA doesn't know a whole lot about its effect on humans. The current EPA "Red Sheet" on Permethrin, which is the full statement of the terms under which a chemical can be registered for sale, is not reassuring:
"EPA is not currently following a cumulative risk approach based on a common mechanism of toxicity for the pyrethroids," the sheet says.
"Nor do we have a clear understanding of effects on key downstream neuronal function e.g., nerve excitability, nor do we understand how these key events interact to produce their compound specific patterns of neurotoxicity."
For a while pyrethroids were popular with manufacturers of flea collars for cats and dogs, but the EPA took a harder look when animals started showing up with tremors and some even keeled over dead.
Those reactions were part of the impetus for a closer look and new labeling requirements, which now include the following language: "DO NOT USE ON CATS. May be toxic or potentially fatal if applied to or ingested by cats. Accidental application to cats and/or grooming a recently treated dog may result in tremors and/or uncoordinated muscle movements. If this occurs, immediate veterinary care should be provided."
Other warnings required by the EPA are: "This pesticide is extremely toxic to aquatic organisms, including fish and invertebrates. ... This pesticide is highly toxic to bees ..."
I spoke to a number of critics of pyrethroids and asked why, if the stuff is that toxic, spraying would not at least kill mosquitoes. Maybe we have to break a few eggs.
The critics have arguments — theories, really — about why the spraying may not kill the right mosquitoes. They say to get the right ones, the ones that are full of bird blood, you would need to spray during the day when those mosquitoes are flying, not at night when the big fat belly-full mosquitoes are safe under their leaves of grass.
It's pretty tough stuff for a layman to sort through. But when I ask the agencies authorizing the spraying what research they have done or seen to prove it works, I get zip.
I said at the top that this was not going to be me hauling on the rope of the big church bell in the town square at midnight screaming, "The British are coming!" But I do want to go back to my opening point about zebra mussels.
The city never raised a hand, never raised an objection, never demanded a ban on pumping of water from Lake Texoma when it became known there were zebra mussels there, never demanded an absolute ban on moving boats from lake to lake the way California did years ago.
Now the entire drinking water system of this city and every municipality in North Texas is severely threatened. There can be cost for an absolute lack of caution or will in environmental matters. A big cost.
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