Aquatics Chlorine and Chloramine Toxicity – NAVLE Study Guide

Overview and Clinical Importance

Chlorine and chloramine toxicity represents one of the most common yet preventable causes of acute mortality in aquatic animals. Municipal water supplies routinely use chlorine (Cl2) or chloramine (NH2Cl) to eliminate pathogenic microorganisms. While safe for human consumption, these disinfectants are extremely toxic to fish, amphibians, and aquatic invertebrates even at concentrations as low as 0.02 mg/L.

Both chlorine and chloramine act as potent oxidizing agents that cause severe chemical burns to the delicate gill epithelium, leading to respiratory compromise, osmoregulatory dysfunction, and rapid death. Understanding the pathophysiology, clinical recognition, and appropriate emergency management of chlorine toxicity is essential for any veterinarian working with aquatic species.

Etiology and Pathophysiology

Chemical Properties and Sources

Chlorine (Cl2) is a yellow-green gas that dissolves in water to form hypochlorous acid (HOCl) and hypochlorite ion (OCl-). The relative proportion of these species depends on water pH, with hypochlorous acid predominating at lower pH values. Municipal water systems typically maintain chlorine levels between 0.5 and 2.0 ppm for human safety.