Chlorine alone as Cl2 is highly toxic, and it is often used as a disinfectant. In combination with a metal such as sodium it becomes essential for life. Small amounts of chlorides are required for normal cell functions in plant and animal life. Chlorides can corrode metals and affect the taste of food products. Therefore, water that is used in industry or processed for any use has a recommended maximum chloride level.
Chlorides can contaminate freshwater streams and lakes.
Fish and aquatic communities cannot survive in high levels of chlorides.