DEER PARK,Texas–In March 2019, a large chemical fire caused toxic smoke to spread over a Houston suburb. A week after the fire was put out, Mario Ochoa held his 4-year-old son, Castiel, and prayed that the child’s cough would ease so that they could both sleep.

However, Castiel kept waking up with frightening snoring that sounded like he was struggling to breathe. Ochoa described the experience as watching his son “drown right in front of” him.