Officials in Houston are just beginning to grapple with the health and environmental risks that lurk in the waters dumped by Hurricane Harvey, a stew of toxic chemicals, sewage, debris and waste that still floods much of the city.

Officials in Houston are just beginning to grapple with the health and environmental risks that lurk in the waters dumped by Hurricane Harvey, a stew of toxic chemicals, sewage, debris and waste that still floods much of the city.