Jasmine Walker, driving the truck tonight, has been working for the city of Dallas for the last two and a half years. When mosquito traps test positive for West Nile virus in any neighborhood within city limits, one of these trucks is dispatched to drive around and spray a mosquito-killing fog in the form of the chemical compound Aqualuer 20-20.
Each neighborhood takes about an hour and a half to spray, though sometimes the crews can be out all night depending on how many they have to hit and how many trucks are available from other cities, she says.
The night starts at the Southwest Division police station, where the Aqualuer is kept in a “secure location.” They fill up the trucks as if they’re putting gas in the tank, then head out to whichever area has been identified for spraying.
Walker hops into the bed of the truck and hooks up the spraying apparatus. She doesn’t wear a mask or any protective gear. She isn’t required to by the city. “It’s safe,” she says when asked.
The fog is clearly visible as soon as the truck starts moving, swelling up over the tree-line, reflecting the truck's flashing lights as an orange-tinged cloud.
The truck ambles along at its 10 mph pace. It passes a cross street where there’s a young man taking his dog out. Though the city doesn’t require its own employees to wear any protective gear while turning on the fog outside (though they do remain in the trucks for the entirety of the spraying), it urges its citizens to stay inside, according to a city press release:
“While the insecticide is approved by the Environmental Protection Agency for treatment, residents … should avoid contact with the spray by staying indoors. Persons inside a vehicle while trucks are actively spraying should remain in their vehicles with the windows up and the air conditioner on until the trucks pass and the spray is no longer visible. Persons out during the scheduled spraying time should be alert for trucks and should not follow them. Residents who come in contact with the spray are advised to wash the affected area thoroughly with soap and water. The spray breaks down quickly in the presence of sunlight and has no residual effect.”
This is the city’s response to the growing number of West Nile Virus reported in Dallas County, which reached 31 on Thursday. There have been 31 cases of Zika as of Aug. 18, but the city spraying only targets mosquitoes that may carry West Nile Virus. Those mosquitoes are most active in the evening and night, whereas Zika-carrying mosquitoes are daytime creatures.
There is a lack of evidence showing the effectiveness of both ground spraying and aerial spraying in lowering mosquito populations beyond a short period of time, and the long-term effects of blanketing neighborhoods with such chemicals are largely unknown. The product is toxic for fish and other aquatic organisms, as well as bees, according to its label.
Permethrin, one of two active ingredients in Aqualuer 20-20, is a synthetic pyrethroid, a type of chemical that environmental health scientists are becoming increasingly concerned about. These types of ingredients have been linked to endocrine disruption and neurodevelopmental disorders, says Jennifer Sass, senior scientist with the Natural Resources Defense Council.
The other active ingredient is piperonyl butoxide, a chemical that enhances the effect of active ingredients without increasing the dosage. It is used in many household products.
“EPA’s safety evaluations consider an extensive battery of exposure and toxicity data on each pesticide active and inert ingredient, as well as the formulated product and exposure assessments assume the greatest potential exposure,” writes an EPA spokesman in an email to the Observer. “The risk assessment process ensures that when a pesticide is used according to the label, people and the environment are adequately protected.”
Nathan Donley, a scientist with the Center for Biological Diversity, doesn’t agree.
“The EPA almost always disregards data that come from formulated products (the process in which different chemical substances, including the active ingredient, are combined to produce a final product),” Donley writes in an email. “So while it is true that they ‘consider’ toxicity data on the formulated product, it is rarely, if ever, used in the risk assessment process.” The problem is that the EPA only registers single active ingredients for use as pesticides, and not the way they interact with other chemicals.
Justin Williams, chairman-elect of the North Texas GLBT Chamber of Commerce and a resident of the neighborhood, wasn’t aware there was mosquito spraying scheduled tonight. The city only posts alerts on its website or sends emails to subscribers on a city mailing list.
“Our neighbor has been here forever and she said there used to be a lot of geckos and lizards around, but now there aren’t,” says Derek Selders, Williams’ partner, who came outside when he saw the pickup’s lights. “She thinks it’s because they started spraying.”
Selders and Williams were going to invest in a bat box as a natural way to eliminate mosquitoes, but they’re not sure if it’ll work with the chemicals in the air.
“Though I haven’t been bitten by a mosquito since the truck passed,” Selders says jokingly. The truck is supposed to turn off the spray if it encounters people outside, says Walker, which is counterintuitive since the fog is meant to travel beyond just the street in which the truck drives in order to cover the nooks and crannies of the spray area.