Concerned about an increase in the number of insects and birds testing positive for West Nile virus this summer, the local mosquito abatement district is once again using planes to spray pesticides over parts of the Sacramento region.
The spraying by the Sacramento-Yolo Mosquito and Vector Control District has drawn criticism over possible health risks, with one scientist contending the pesticides pose a potential health concern for pregnant women, while others say the risks are negligible.
Aerial spraying of pesticides was conducted on Wednesday and Thursday evening last week in Citrus Heights, Fair Oaks and Orangevale. That followed aerial spraying in south Sacramento earlier this month and backpack spraying in Arroyo Park and Mace Ranch Park in Davis.
The spray used to kill adult mosquitoes often contains pyrethroids and organophosphates. Both kinds of chemicals have produced health effects on laboratory animals, and studies have implicated the chemicals in lower IQ scores when babies are exposed to them in the womb.
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Sacramento’s mosquito district used the pesticide Trumpet EC, which includes an organophosphate called Naled.
That chemical makes up 78 percent of Trumpet EC. It is registered for use in mosquito control by the U.S. Environmental Protection Agency and the California EPA.
The California Department of Public Health does not see any cause for concern. “There is no need for anyone to take special precautions in regards to aerial spraying of Naled,” said Vicki Kramer, chief of the department’s Vector-Borne Disease Section. “There are no known human health risks associated with aerial spraying of Naled for mosquito control.”
The Environmental Protection Agency has ruled that Naled is not toxic to humans. At the same time, though, the agency lists Naled as a possible carcinogen.
One UC Davis scientist says greater precautions should be taken when such chemicals are used, despite the department’s safety declaration.
“The big concern is the long-term effects that might happen from low level non-acute toxic doses,” said Irva Hertz-Picciotto, environmental epidemiologist with UC Davis. “My concern is for young children and pregnant mothers.”
Hertz-Picciotto’s concern arises from a study she co-authored that found a link between a pregnant mother’s geographic proximity to where pesticides are applied and higher rates of children born with autism.
In that study, the residences of women who bore children with autism were compared to residences of women whose children developed normally. It turned out mothers who bore autistic children were more likely to have lived close to where pesticides like organophosphates were applied to farm fields. Most of the women in the study lived in or near the Sacramento region.
The study found that children of mothers residing near areas where pyrethroid insecticide was applied just prior to conception or during the third trimester were at greater risk for both autism spectral disorder or developmental problems.
That study did not include Naled in the pesticides measured. It was criticized as making a weak link between pesticide location and pregnant mothers giving birth to autistic children.
Pyrethroids are not currently being used in aerial spraying in Sacramento because insects have developed a resistance to prior spraying. However, the chemicals are still being used elsewhere in California.
Hertz-Picciotto said more research needs to be done on the long-term effects of aerial spraying.
“My concern is that very young children, and pregnant mothers, should be taking precautions,” Hertz-Picciotto said. “It seems to make sense that they would do so.”
One such precaution would be staying indoors during aerial spraying.
A 1999 Department of Pesticide Regulation study found that urine levels in individuals that were outdoors during spraying had higher levels of the Naled pesticide than those that who were indoors during spraying.
There are other scientists who believe that the Naled is safe for aerial spraying.
“The odds of anyone getting a toxic dose are just not there,” said Bruce Hammock, professor in the Entomology & Comprehensive Cancer Center at UC Davis.
He said he believes the biggest issue with spraying is the emotional reaction people have to the idea of chemicals being sprayed on them.
“It’s a common societal problem – that we want benefit without risk,” said Hammock.
But he also said the issue of aerial spraying of pesticides is a not a simple one. “I’m immune-suppressed, so if I get West Nile, I’m dead,” Hammock said. “On the other hand, I have a grandson with autism.”
Although he said Naled is safe, he agrees that all pesticides carry some form of risk.
“Organophosphates are designed to kill insects,” he said. “Not all insects are pests. Both organophosphates and pyrethroids will kill butterflies.”
On Wednesday and Thursday the pesticide spraying targeted 19,000 acres – from the Sacramento County line on the north, down to Lincoln Avenue to the south, and from Interstate 80 and Garfield Avenue on the west to Hazel Avenue to the east, said Luz Rodriguez, spokesperson for the Sacramento-Yolo Mosquito and Vector Control District.
“We spray less than an ounce per acre,” Rodriguez said. “It’s a very small quantity and only targets mosquitoes or insects that are smaller.”
The areas sprayed were chosen because evidence of West Nile was found in insects and birds tested in the areas, said Rodriguez.
To date, this year, 154 mosquito samples have tested positive for West Nile Virus in Sacramento and 56 in Yolo County.
Once a first mosquito is found testing positive for West Nile, the vector control district traps mosquitoes in a 1 mile radius in order to establish where virus hotspots are, she said.
Vector control districts see aerial spraying as a crucial tool for vector districts to stop the spread of the virus among mosquitoes. In 2005, areas that were not sprayed saw 18 new cases of humans testing positive for the West Nile Virus. Those that were sprayed saw none.
In humans, the effects of West Nile Virus range from a mild fever to permanent disability and, in some rare cases, death. Many who have the virus show no discernible health effects.
The virus made its first appearance in the Sacramento region in 2003. Aerial spraying began 2005. That year 880 humans tested positive for the virus in California, and there were 19 West Nile-related deaths.
Last year there were 379 confirmed cases of humans with the virus, and 15 deaths statewide. Sacramento tallied 10 confirmed human cases of West Nile.
There were no deaths last year in Yolo or Sacramento counties due to the West Nile virus.
Across the state, 11 humans in California have tested positive for West Nile this year. No humans have tested positive for the disease in the Sacramento region.
Some critics say not enough is known about the long-term effects of the pesticides – regardless of the low volume being sprayed in Sacramento.
“The thing that is most concerning about the particular steps taken by vector control districts in that the last two or three years they seem to be stepping up the pesticide ladder,” said Mike Somers, director of Pesticide Watch, an advocacy group that seeks to prevent pesticide exposure while promoting local farming.
Somers was referring to the Sacramento-Yolo Mosquito and Vector Control District using Naled instead of pyrethroids.
For Somers the concerns are as much personal as they are professional. He lives in south Sacramento, where the vector control district sprayed on June 30 and July 1.
“I have a 6-month-old kid, and his brain is developing,” said Somers. “So, to expose him to even low levels of pesticides that can impact his neurodevelopment? That really seems tragic.”