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A person familiar with the incident said that before the training at the San Francisco County Jail on Moreland Drive in San Bruno, officers from UC Berkeley and UCSF were invited to bring any chemical agents in the campus police forces' inventory so they could be disposed of during the exercise. Police with at least one of these departments brought crates of chemical canisters that dated back as far as the 1960s, said the source, who spoke on condition of anonymity because they were not authorized to discuss the matter. The Chronicle granted anonymity under its confidential sources policy. Advertisement Article continues below this ad On Wednesday, after the initial publication of this story, officials with the San Francisco Sheriff's Office said UC Berkeley officers had brought over the canisters used in the May 21 exercise, and that they were believed to have been pulled from storage. Tara Moriarty, a spokesperson for the sheriff's office, said a preliminary investigation showed that there "were no expiration tabs on the canisters brought over by UC Berkeley." Moriarty said she could not estimate the age of the canisters and directed questions to UC Berkeley. A spokesperson for UC Berkeley said its campus police force had no comment, and referred all questions to the San Francisco Sheriff's Office, which oversaw the exercise. Tear gas canisters typically expire about five years after their manufacture date. Sheriff's officials said the exercise involved testing chemical agents including CS gas (2-chlorobenzylidene malononitrile) and OC gas (oleoresin capsicum), otherwise known as pepper spray. Advertisement Article continues below this ad The exercise was designed to test gas masks and effects of chemical agents like pepper spray and tear gas, the source said. The munitions were to be deployed inside a structure on the San Bruno jail property, simulating a potential barricade or hostage situation. The source said it was not routine to deploy such a large amount of munitions in an area so close to civilian populations. One adult and 20 children at Portola Elementary School on Amador Avenue experienced irritated eyes, throats and noses after the chemicals wafted approximately a half-mile, officials said. An ambulance and fire crew responded to the scene, but none of the victims were hospitalized. San Francisco Sheriff Paul Miyamoto's office confirmed that the sickening of the children was due to the training exercise, and halted all further exercises pending an investigation. In later interviews prior to the initial publication of this story, sheriff's officials did not directly address whether outside or expired chemicals were used during the exercise. Advertisement Article continues below this ad "Obviously we are always concerned that there's something expired or out of commission, to how we dispose of that," Miyamoto told the Chronicle's editorial board when asked whether the incident included chemicals that were decades old. "It's a part of what we're going to look into as part of our review, making sure that it doesn't happen again." Moriarty said Wednesday that it was common for law-enforcement agencies to use stored chemicals for training exercises, and that "there appears to be no greater health risk than using the same product that has been recently manufactured." Some experts, however, said it was nearly impossible to know whether expired tear gas canisters are more or less hazardous, because manufacturers aren't transparent about what specific chemicals are inside of them. Both the Bay Area Air Quality Management District and San Mateo County Environmental Health Services said they were investigating the incident. "While there are no indications of any lingering environmental hazards at the site or in the surrounding area, the investigation will determine if all reporting requirements to the appropriate agencies were followed subsequent to the incident and whether appropriate contingency plans were in place to mitigate any release," said Preston Merchant, a spokesperson for San Mateo County Health. He said the department would not comment further until the investigation was complete. Advertisement Article continues below this ad Both substances cited by the sheriff's office can be referred to as tear gas, which is the general term for aerosol-dispersed chemicals that "produce eye, nose, mouth, skin and respiratory tract irritation," according to the National Institutes of Health. Tear gases are banned for military use, but law enforcement agencies are allowed to use them for domestic circumstances, like riot control. Bay Area agencies have used tear gas on numerous occasions in recent years. But the amount of chemicals detonated inside the structure was so voluminous that the building couldn't contain all the smoke and gases, the source said. Sheriff's officials called the sickening of the school children an "unprecedented situation," adding that the site had been used for training exercises for more than 20 years. Advertisement Article continues below this ad Chemical experts said that while chemical agents typically lose potency over time, no one really knows what happens to them after they sit on a shelf for decades. Only the manufacturers know precisely what was in those canisters, and production changes over time, said Emanuel Waddell, a professor and chair of nanoengineering at North Carolina Agricultural and Technical State University in Greensboro. He said the chemical makeup of the substances used during the training exercise could vary depending on how they were stored. "They could become less toxic, and there's a chance they could become more toxic," Waddell said. The symptoms of riot-control agents are painful but typically temporary, unless a person has experienced repeated exposure. Waddell added that there are few studies about long-term effects of tear gases and pepper sprays on humans, and most studies are limited to young, healthy men. David Canepa, vice president of the San Mateo County Board of Supervisors, said he was not told by the San Francisco Sheriff's Office about the potential use of decades-old chemicals, but was informed that the office had released all of the agents at once. Canepa said he is calling for a full accounting of the incident from the sheriff's office. "There has to be transparency," Canepa said. "We have to know, from the sheriff's department, what exactly was released." Reach Megan Cassidy: megan.cassidy@sfchronicle.com May 29, 2024|Updated May 29, 2024 12:17 p.m. Megan Cassidy Crime Reporter Megan Cassidy is a crime reporter with The Chronicle, also covering cops, criminal justice issues and mayhem. Previously, Cassidy worked for the Arizona Republic covering Phoenix police, Sheriff Joe Arpaio and desert-area crime and mayhem. She is a two-time graduate of the University of Missouri, and has additionally worked at the Casper Star-Tribune, National Geographic and an online publication in Buenos Aires. Cassidy can be reached on twitter at @meganrcassidy, and will talk about true crime as long as you'll let her. Top of the News San Francisco S.F. removes controversial 'Appeal to Heaven' flag from Civic Center Plaza, saying it has been co-opted San Francisco officials recently removed the controversial "Appeal to Heaven" flag from Civic Center Plaza. It had flown there for decades. 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