Public health

Mosquito fog has residents squirming

There’s a truck—more than one, in fact—that drives slowly through our neighborhoods, leaving a fog in its wake. The fog doesn’t last long, five minutes when the air is still, but it’s lethal by design. For mosquitoes, that is.

All in all, the insecticide that fogged up neighborhoods all over the county this summer is fairly safe. Not safe—fairly safe. And the neighbors don’t know when to expect those trucks because the only notification method the Butte County Mosquito Abatement and Vector Control District has for alerting people is an e-mail list. There are only 30 to 40 people on it, acknowledged Jim Camy, manager of the district. (Call 533-6038 or 342-7350 to be added.)

“I went and told everyone on my street that it would be happening,” Karen Laslo, who lives on East Sacramento Avenue in Chico, said about the fogging. “Most people didn’t know anything about it. I got home just in time, and I was looking out the window. A truck came by and was spraying out this cloud. And a young man [on a bicycle] rode right through it. I thought, ‘What’s going to happen to him?’ He probably didn’t even know what was going on.”

Anyone can check online at to find up-to-date route maps for the trucks—they always spray at dusk. But that’s an awful lot of work considering the district doesn’t decide where to spray until that day.

“People have asked that we try to give them a regular schedule,” said Camy—but the trucks are dispatched to various locations based on mosquito activity. Traps are used to calculate populations and activity levels. They are checked once a week.

“We can only fog when mosquitoes are actively flying,” he said. “It’s paid off because so far we’ve had 16 cases [of West Nile], whereas last year we ended up with more than 30.”

Weather also must be taken into account. If it’s raining or particularly windy, fogging won’t be effective.

“This cooling off has helped us a lot,” Camy said. “We haven’t needed to do any fogging. If the mosquitoes aren’t out there actively biting, then there’s no reason to be fogging.”

Camy touts the safety of the insecticide the district uses. It’s true, the compound is fairly harmless to human beings … unless, that is, you suffer from asthma or are susceptible to skin allergies.

The insecticide released into the air during fogging is a mixture of pyrethrum, piperonyl butoxide and oil. Pyrethrum is derived from the chrysanthemum flower. It acts to immobilize mosquitoes—and a host of other insects that it could come in contact with, including flies and crickets. Piperonyl butoxide (PBO for short) speeds up the pyrethrum, but isn’t an insecticide in its own right.

“Inhaling high levels of pyrethrum may bring about asthmatic breathing, sneezing, nasal stuffiness, headache, nausea … and burning and itching sensations,” reads the Pesticide Information Project listed on, a Web resource for information in toxicology and pesticides.

The concentration of pyrethrum in the fog solution is so small that the possible side effects are unlikely at best. Still, the Centers for Disease Control and Prevention suggest people with asthma stay indoors while pesticides are being sprayed. Small children, too, whose immune systems are not yet up to par, should be kept inside.

The CDC says educating the public on how to minimize the risk of contracting West Nile and how to rid their homes of mosquito habitats is a necessary component. Some argue that Butte County’s Web alerts and infrequent media coverage is not enough in that regard.

“It’s about education and personal empowerment,” said Luisa Garza, a longtime Chicoan and horticulturalist who moved to Forest Ranch five years ago. “Not just mass poisoning us because they might think we’re ignorant or they don’t want to frighten us.”

People like Garza and Laslo just want to be involved instead of kept in the dark. Both women question what pyrethrum does to other insects in the fogged areas. If bigger bugs are being paralyzed by this insecticide, then it could throw off the whole food chain.

“I don’t have any crickets anymore,” Laslo said. “I love them, but I haven’t heard any. I just wonder—what are we doing? Do we know what we’re doing to ourselves?”

Laslo feels so strongly that not enough is being done to educate people about the threat of mosquitoes and the fogging technique that she wrote a letter to the Chico City Council. In it, she poses the question, “Is the threat of West Nile so severe and our fear of it so high that we inadvertently cause another ‘Silent Spring'?”