Chloride is found naturally in seawater and certain minerals. However, the major source in which it enters the environment is through its use to deice roads during the winter, fertilizers, and sewage. Because they are extremely cheap and effective, Cl – compounds are used heavily during the winter to deice roads, ending up in surface waters everywhere.
Chloride is very soluble and mobile, compounding its effects as a pollutant. Additionally, once chloride has entered an ecosystem, it can take years to exit it, as there is no natural way it is metabolized or flushed from the organisms and water. It increases the salinity of these habitats, which can ruin the balance of osmosis and diffusion in cells, killing many organisms.