Sodium hydroxide (NaOH) has the potential to be a dangerous chemical in aquatic environments due to it raising the
pH level of the water. At low concentrations, NaOH will be neutralized by other chemicals in the water, such as acids and dissolved
carbon dioxide (). Also, NaOH does not bioaccumulate in the aquatic organisms as it is dissolved in the water and has a negative
octanol-water partition coefficient. The
median lethal dose (LC) concentrations for aquatic organisms for NaOH range between 33 and 189 mg/L. The pH scale is a measure of the concentration of free hydrogen ions in the water. Extremely high pH will harm fish, specifically juveniles, by removing their slimy coats and drying out their skin, eyes and gills. Consequently, raising the pH of an aquatic environment can directly increase the toxicity of other chemicals, such as
ammonia (). This is because in basic solutions (), becomes more prevalent than
ammonium (), and it is dangerous to aquatic life. When pH exceeds 9, concentrations are over 100 times higher than below pH of 9. Ultimately, high pH can lead to death of organisms in aquatic environments and directly reduce biodiversity in these environments. If not caused by man-made industries or accidents, high pH surges can occur naturally and may be observed when algal blooms occur, otherwise they are virtually impossible to observe without directly measuring the pH of the water. ==See also==