Texas Water Code - WATER § 7.252. Defenses to Endangerment Offenses

(1) the conduct charged was freely consented to by the person endangered and that the danger and conduct charged were reasonably foreseeable hazards of the person's occupation, business, or profession or a medical treatment or medical or scientific experimentation conducted by professionally approved methods and the person endangered had been made aware of the risks involved before giving consent; or

(2) the person charged was an employee who was carrying out the person's normal activities and was acting under orders from the person's employer, unless the person charged engaged in knowing and wilful violations.