The last time Dallas used aerial spraying to curb the mosquito population, Texas' Lyndon Johnson was in the White House, Mission Control in Houston was launching Gemini missions and encephalitis was blamed for more than a dozen deaths.
But for the first time in more than 45 years, the city and county planned Thursday to resume dropping insecticide from the air to combat the nation's worst outbreak of West Nile virus, which has killed 10 people and caused at least 200 others to fall ill.
"I cannot have any more deaths on my conscience because we did not take action," Dallas Mayor Mike Rawlings said.
Although commonplace in other major cities, the efforts are provoking a debate in the Dallas area between health officials trying to quell disease risk and people concerned about insecticidal mist drifting down from above.
Nearly half of all West Nile cases in the United States so far this year are in Texas, according to the Centers for Disease Control and Prevention. If the trend continues, 2012 will be the worst West Nile year in state history.
The hot, dry weather across the nation's midsection has created ideal conditions for mosquitoes. The heat speeds up their life cycle, which accelerates the virus replication process, and any standing water in drought-plagued places is turned stagnant â€" their preferred breeding ground.
Both the mayor and Dallas County Judge Clay Jenkins have declared a state of emergency and voiced their support for an aerial defense. Yet even with the threat of infection, the spraying has sparked widespread opposition from people who fear the chemicals could be harmful.
"It's something new there that has not been used in quite a number of years," said Dr. Roger Nasci of the CDC, explaining the public's worries. "Anything novel comes with that unknown factor."
Because of the severity of the outbreak, the Texas Health Department is stepping in to oversee the effort and to pay for it.
"This year is totally different from the experience Texas has had in the past," state Health Commissioner Dr. David Lakey said. "If it's nuisance mosquitoes, we ask the city or county to pay part of that. But in the midst of this disease outbreak, it's easier for us to go ahead and do it."
A national spraying company called Clarke was set to deploy two to five Beechcraft King Air twin-engine planes late Thursday night for three hours of spraying. One county-wide application costs about $1 million. A second application is possible if the first attempt does not kill enough mosquitoes.
Critics have also questioned whether the approach is scientifically proven to reduce West Nile cases. But at least one study in California concluded that the odds of infection are about six times lower in treated areas than those that are untreated.
Still, some residents fear the chemicals could harm their children, pets and useful insects such as honeybees and ladybugs.
The chemical released from the planes, synthetic pyrethroid, mimics a naturally occurring substance found in chrysanthemums. The Environmental Protection Agency has said that pyrethroids do not pose a significant risk to wildlife or the environment, though no pesticide is 100 percent safe.
About eight-tenths of an ounce of chemical is applied per acre, said Laura McGowan, a Clarke spokeswoman.
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