Four-year-old Roberto Diaz is a round little fellow who strides confidently out into the yard. It's early, before most daycares would open. However this one in Courtland — 35 kilometres north of Sacramento in California's agricultural heartland — is for the children of the mostly poor, mostly Latino, farm workers, whose shifts in the fields often start before dawn.

But those who care for these kids believe they may not be safe here.

According to Rosalva Beas, a caregiver at the daycare, there's danger in the wind. Beas looks through the fence, past the playing kids, towards the distant pear orchards.

Wind blows pesticides toward the daycare

"When they spray pesticides, the wind blows this way and it contaminates this area," she says.

It's known as pesticide drift: Chemicals applied to fields and orchards can sometimes disperse further than industry experts claim they're supposed to travel. According to California's Department of Health, 500,000 California kids go to school within 400 metres of fields that are sprayed with pesticides.

Need for stricter rules around pesticides

When it comes to spraying near California schools, there are no federal or state laws. Rules vary from county to county. Now, some daycares and schools claim their students are getting sick. Residents of farm country are lobbying for tightening of rules over where and when pesticide can be sprayed.

"Before, we didn't see so many illnesses," Beas says. "Now we're seeing more and more illnesses, these kids who are just starting out in life."

And it's not just the kids getting sick.

"I'm sick now, I got asthma," says Bianca Sanchez, a caregiver at the childcare centre.

"Because when they're doing the pear, everything comes over here," she says.

The pesticides can stay in the air for days, according to Emily Marquez, a staff scientist at the Pesticide Action Network (PAN).

She's demonstrating a metre-high device that looks like a half-finished science experiment; all tubes and glass, it is a low-cost airborne particulate matter detector.

She lends it to homeowners, schools and childcare facilities so they can test their own air, to give them independent data confirming whether there's been pesticide drift. If it is happening, it's especially serious for children, she says.