BELLE GLADE, Fla. — Dozens of farmworkers looked up at the little yellow plane buzzing over the Florida radish field, a mist of pesticide falling from its wings.

Farmworkers are supposed to be protected by government rules regulating exposure to toxic farm chemicals. But in this case, the breeze pushed the pesticide over the crew in a neighboring field, where it fell mostly on women, including at least one who was pregnant.

“I smelled a strong odor and started feeling bad,” worker Maria Garcia later told a state investigator. “I had a headache, itchy eyes and threw up.”

The health investigator assigned to the case said more than a dozen workers showed symptoms of pesticide poisoning, and also found evidence that the farm and crop-dusting contractor may have violated federal farmworker safety laws.

An Associated Press review of federal and state enforcement data and other records revealed that the pesticide-safety system is riddled with problems: Investigations often take years to complete and result in few penalties. Written warnings are common, fines rare. Compliance is sometimes voluntary, not required. And worker anonymity can be compromised, making employees reluctant to report violations.

The agriculture industry defends the system, saying the low numbers are a sign that farms are doing a good job of protecting workers.

President Barack Obama’s administration recently adopted tougher farmworker protections after 20 years of debate and fierce resistance from the chemical and agricultural lobbies. The more stringent regulations adopt annual training requirements, safeguards to keep children workers out of the fields and stronger penalties for companies that retaliate against workers who report violations. However, when they take effect in 2017, all of the new rules will still rely on the existing enforcement system.

Adding to the troubles are the regulators themselves. In all states except California, enforcement of federal pesticide-safety laws is managed by the same agencies that promote agricultural industries.

The Florida workers fell ill on Oct. 14, 2014, in Belle Glade, a farm town near Lake Okeechobee where the motto is “Her soil is her fortune.” They had been moved at the last minute to a celery field owned by Duda Farms. Rains the previous night had made the fields they were supposed to plant too soggy.

That was not communicated to the crop-duster pilot, who should have waited to spray a “restricted-use” pesticide called Bathyroid XL, records show.

Bathyroid XL is listed as a probable human carcinogen, according to the U.S. Environmental Protection Agency. Studies on rats showed some neurological effects, but the results of long-term exposure on people are not known. As a restricted-use agent, it is considered one of the more toxic pesticides available to American farmers.