Evacuation orders remained in place for about 50,000 people in Garden Grove, California, located south of Los Angeles.
Authorities issued an all-clear after they said a natural gas pipeline rupture in Hillcrest Village led several homes to evacuate on Wednesday.
The North Loop eastbound was briefly shut down at the North Freeway due to the chemical leak involving an 18-wheeler on Wednesday.
According to the vice president of operating engineers, of the four exposures, one of the workers remains in the hospital. The company is still working to investigate what happened.
The Targa Resources dock on the Houston Ship Channel has reopened after a chemical leak was reported on Tuesday due to a valve malfunction.
Initially, authorities said they were responding to a possible leak at Mangum-Howell Community Center, but further investigation and readings determined everything was normal.