Ozone has a disinfecting effect and is used, for example, to disinfect drinking water. Ozone is also used to disinfect spring water, swimming pool water and surfaces that come into contact with food, to remove traces of yeasts from air (important when food is packed), to clean and bleach substances, to deodorize interiors and materials after a fire and to remove unwanted harmful substances (e.g. herbicides) from water. In intensive fish farming and aquatic logistics, ozone is used as a disinfectant and for decomposition of fish waste products. It is also applied as an oxidizer in soil remediation (C-sparge) of organic pollutants (e.g. BTEX or trichloroethylene). Ozone is still used for medical purposes, especially in Cuba it is used in the fight against cancer.