Jonathan Velasquez Sr., 29, was arrested around 11 a.m. today at his workplace in Dixon, Sgt. Charlie Spruill said.
The infant was treated Oct. 11 at the UC Davis Medical Center for being under the influence of marijuana, Spruill said. The infant and his 2-year-old brother, who was not exposed to marijuana, were taken into protective custody.
A subsequent investigation by the Police Department's Family Investigative Response Services Team and Solano Child Welfare Services determined the infant either inhaled or ingested enough marijuana to require immediate medical attention, Spruill said.
Spruill said the infant was exposed to the marijuana while he was with Velasquez either at a south Vacaville residence or at a park where the infant's birthday was to be held on Oct. 11.
Velasquez left the child at the Vacaville residence to return to the park and prepare for the birthday party, Spruill said.
The infant's adult relatives, including the boy's mother, who were at the residence then noticed the boy was lethargic and unresponsive and took him to the hospital because they feared he had the flu, Spruill said.
Hospital personnel determined that the child had been exposed to marijuana, Spruill said.
"We don't know whether he ingested or inhaled it. It happened within minutes," Spruill said. Hospital personnel called Solano Child Protective Services and the agency then called police, Spruill said.
Velasquez was booked into the Solano County jail for felony child endangerment, Spruill said.
Police would not disclose Velasquez's relationship to the child to protect the infant's identity, Spruill said.