About a dozen residents Monday protested work underway to convert a Sebastopol apple orchard into a vineyard, saying dust from the uprooted trees contained toxic pesticides that could harm children at neighboring schools.

Work began last week on the property, owned by Sebastopol winemaker Paul Hobbs. Parents of children who attend several schools in the area say they want a buffer zone between the property and the adjacent Apple Blossom and Orchard View schools.

Parent groups raised the issue of soil contamination when Hobbs applied for a vineyard development permit in March. The winemaker bought the 48-acre property on Watertrough Road in 2012.

"This is so close to a school, you can't ignore it," said Thomas Cooper, whose son attends nearby SunRidge School. "We're here to raise the alarm."

Twin Hills School District is working with Paul Hobbs Winery to limit the dust during the conversion project, said Barbara Bickford, the district's superintendent. The winery is planning to build a fence to limit the dust and will spray chemicals outside of school hours, Bickford said.

"We certainly have taken great strides to address the concerns," she said. "We have worked with the grower to ensure the safety of the children, the teachers and the staff."

The school district will monitor dust levels in the air, and has met with an environmental engineer who said "the risk for dust migration appears to be minimal," Bickford said.

Maben Rainwater, school board president, said that he will feel better about the project if Paul Hobbs Winery complies with its permit and its agreement with the district. Hobbs is required to water the fields during tree removal to keep the dust down, he said.

"I think we, as a district, are going to need to keep Hobbs' feet to the fire," he said. "Any issue that comes along regarding the health of our kids is a legitimate concern. As long as Hobbs follows what has been mandated, we will be well served."

Tony Linegar, the county's agricultural commissioner, said the winery has followed requirements. The chemicals that will be used in the vineyard are not as toxic as those used in the apple orchard, he said.

"By converting from an apple orchard to a vineyard, the pesticide exposure is drastically reduced," he said.

Chemicals used on the orchard include Lorsban and Imidan. The vineyard will use Roundup and wet sulfur, Linegar said.

The dustup with neighbors is not the first for Hobbs, who has aggressively expanded vineyards in western Sonoma County. In 2011, he required that a Christmas tree farm on Highway 116 near Graton be cleared as a condition of his purchase and also angered residents by cutting down redwoods nearby. He also acknowledged cutting down trees without proper county permits at a site near Pocket Canyon east of Guerneville.

Tara Sharp, spokeswoman for Paul Hobbs Winery, said the company is working with local officials and neighbors to ease concerns.

"We're doing everything within the regulations," she said. "We're being extremely thoughtful throughout this whole process and trying to be good neighbors."

Parents are particularly concerned by the Watertrough Road site's proximity to four schools with a total enrollment of about 700 students.

"I feel the emotion and a huge sadness for the loss of these trees and the safety of the children," said Lori Gatmaitan, a massage therapist who protested on Monday. "There has been 50-plus years of chemical use on this land and there hasn't been the proper soil testing to alleviate my concerns."