When the algae died and rotted, their decomposition would rob the lake of its oxygen, leading to fish kills. Aside from this, the algae blooms are very unsightly. Today, the use of phosphates in detergents is regulated by legislation, in addition to which, many communities treat their sewage so as to remove any phosphate before the water is finally discharged to the environment. This yields the white form of phosphorus which is extremely poisonous. About a tenth of a grain is a lethal dose for a person.
White phosphorus has the property of spontaneously catching fire in air.
For this reason, it is used in incendiary bombs. When the bomb splits open and the phosphorus inside meets the air, it immediately catches fire. This has quite different properties. Red phosphorus does not inflame in air, and it is much less poisonous. When heated with sulfur, red phosphorus gives phosphorus sulfide, a pale yellow substance.