They told investigators they felt dizzy and weak, had stomach pain and headaches, and complained of sore throats, eye irritation and blurred vision.
Some of them vomited from the exposure.
"I began crying because I couldn't breathe and my vision was blurred," one unidentified worker said.
"I had a severe headache, nausea, sore throat and numb feet," another employee said.
The workers were all employed by Tanimura and Antle, a produce grower that also owns the contractor that sprayed nine different pesticides on adjacent celery and lettuce fields about six hours before workers started complaining of symptoms.
The company took some workers to Salinas Valley Memorial Hospital in Salinas, but didn't have enough vehicles to transport all of the sickened employees. Several fieldworkers had to get themselves to the hospital.
The failure to get prompt medical attention for all of the affected workers is the subject of the one violation the agricultural commissioner's office plans to issue against Tanimura and Antle.
"A hazard was created when those who were experiencing illness symptoms, including dizziness and nausea, were allowed to drive themselves, and others, to (Silicon Valley Memorial Hospital), creating an unsafe condition," wrote Ronnie Capili, a Monterey County agricultural inspector.
The maximum fine the commissioner's office can levy against the company for that violation is $5,000.
Local farmworker advocates say the company should face stronger punishment for allowing so many of its workers to get sick.
"I was absolutely shocked," Weller, with Californians for Pesticide Reform, said in an interview after reading the commissioner's findings.
The county agricultural commissioner plans to issue the fine in August or September, according to Ken Allen, a deputy agricultural commissioner.
Despite the extreme nature of the farmworkers' symptoms and the large number of employees who became sick, the commissioner's office said it did not find any other violations tied to the case.
"There were no issues during the applications, therefore no non-compliances were noted," wrote Capili.
Investigators believe the dense fog the morning of the incident contributed to the chemicals drifting over into the field were the celery employees were working.
Anne Katten, director of the California Rural Legal Assistance Foundation's Pesticide and Worker Safety Project, said that finding shows that pesticides sprayed in foggy conditions can present a heightened danger.
"Fieldwork should not be allowed so close to fields just treated with pesticides," Katten, who also reviewed the findings, said in an email. "This is a problem that needs to be remedied before more workers are placed in harm's way."
Nine Pesticides Were Sprayed
Tanimura and Antle sprayed six different insecticides, two fungicides and a product used to enhance the effects of the other chemicals on a celery field and lettuce field at Moresco Farms at 10 p.m. on June 21, 2017.
A field crew began showing up at 3:30 a.m. the next day to plant celery starts nearby. Several of the workers told investigators they saw a warning sign at one of the fields where the pesticide application took place, but there was little specific information on what chemicals were used.
"How can one part of the company know that they've applied extremely hazardous pesticide at 10 o'clock one night and then not inform the next morning's crew?" Weller asked. "That's asking for this kind of awful accident."
By 4:15 a.m. the workers started getting sick.
After they were taken to the hospital, the agricultural commissioner's office sent clothing from the farmworkers to a California Department of Food and Agricultural lab to test for pesticides.
The tests found high levels of permethrin and methomyl as well as traces of two other chemicals, chlorantraniliprole and spirotetramat.
Permethrin is the active ingredient in Pounce, an insecticide sprayed on close to 19 acres of celery on the farm's Block 6, a field next to where the farmworkers parked their vehicles. The chemical is classified by the Environmental Protection Agency as a weak or likely carcinogen.
Methomyl is an active ingredient in the insecticide Lannate SP. That pesticide was also sprayed on Block 6, as well as on 11 acres of head lettuce on another field in the area, Block 10.
The EPA says methomyl is extremely toxic if ingested or "moderately toxic" if inhaled. In high enough doses the chemical can "overstimulate the nervous system", leading to nausea, dizziness and confusion, according to the agency. Federal officials say at very high exposures, methomyl can result in respiratory paralysis and death.
Farmworker advocates believe it was the exposure to methomyl that got the workers sick.
Company Cites Changes in Safety Procedures
Representatives and employees of Tanimura and Antle did not respond to requests for comment.
But in an incident report obtained by Monterey County officials, the firm defended its employees' actions and noted that all but one of the sickened workers returned to work "without issue" the next day.
"We cannot find a direct link to any chemical exposure which was the contributing factor to the symptoms felt by our employees," Javier Medina, a human resources employee with the company, said in the report.
The company has, however, made some changes prompted by the incident, Medina wrote.
"As a result of this incident, the decision has been made to avoid working near any posted fields whenever possible," Medina added.
The Monterey County agricultural commissioner's report is the last of four investigations into pesticide drift incidents that sickened a total of 150 agricultural workers in Central California last year. Those included two episodes in Kern County and another in Santa Cruz County.
In June, the Santa Cruz County Agricultural Commissioner's Office issued $56,000 in fines against several companies it found responsible for a chemical drift that sickened 15 raspberry workers in Watsonville last year.
Last, December the Kern County agricultural commissioner imposed nearly $50,000 in fines against five companies tied to a pesticide incident that sickened 92 farmworkers harvesting garlic near Bakersfield.