It’s not what we know that has scared so many Californians in the areas slated to be sprayed with microencapsulated moth pheromones.

It’s what we don’t know.

At the May 5 Light Brown Apple Moth Environmental Task Force Advisory Committee meeting in Monterey, Susan Monheit – a UC Davis environmental analyst contracted by the state – pointed out the major data gaps in the only working environmental document prepared in advance of last fall’s pheromone sprayings over Monterey and Santa Cruz counties.

Armed with an emergency waiver from the U.S. Environmental Protection Agency, the California Department of Food and Agriculture aerially sprayed the two counties with synthetic pheromone products meant to overwhelm the male moths so they can’t find mates. The waiver allowed the spraying to go forward without an environmental impact review required by the California Environmental Quality Act. Instead, the U.S. Department of Agriculture prepared a less-detailed environmental assessment.

Assailed by a public that demanded more information, the CDFA hired UC Davis researchers to analyze its spray plans. Monheit’s task was to review the September 2007 environmental assessment for accuracy.

Six months after the last spraying, Monheit presented her findings. The environmental assessment correctly concluded that the pheromone treatment has a low potential for adverse effects, she told the task force. But the assessment, which uses data on pheromones structurally similar to the LBAM-specific product used last fall, lacks several important components.

It doesn’t calculate the product’s concentration in the air after treatment, Monheit says, which makes it impossible to estimate people’s expected exposure by inhalation. It doesn’t cite a chronic mammalian inhalation toxicity study – which would be appropriate given the state’s plan to spray the product regularly for years, she says – and it lacks a discussion of potential inhalation impacts on sensitive populations, such as children.

The assessment also fails to address the pheromone’s non-lethal effects, though some rats breathed heavily and had runny noses after being exposed to it. “There might be sub-lethal effects that could include respiratory distress or nasal discharge,” Monheit says. “Those are not reported in the environmental assessment and there’s almost nothing about that in the literature.”

CDFA spokesman Jay Van Rein says that some of the missing data, such as toxicology tests on marine invertebrates, have been provided since the assessment was released. USDA spokesman Larry Hawkins says his agency agrees with Monheit’s conclusions and is working to fill in the gaps she identified.

The USDA is now doing toxicology tests on four synthetic LBAM pheromone products, according to CDFA spokesman Steve Lyle. “These are not tests that are required by law,” he adds. “These are tests that the USDA decided to pursue to show a greater degree of due diligence.”

The state planned to spray Monterey and Santa Cruz counties and the San Francisco Bay area beginning in June. But last month, Gov. Arnold Schwarzenegger directed the CDFA to postpone spraying until the toxicology tests are completed, likely in August.

Meanwhile, judges in two court cases – one filed in Santa Cruz County and one filed by the nonprofit Helping Our Peninsula’s Environment in Monterey – have ruled that the state must complete an environmental impact report under CEQA before resuming aerial pheromone applications. The decisions could delay spraying by another year.