Agricultural runoff, sewage, surface runoff, chemical spills and hazardous waste spills can all potentially lead to water toxicity and fish kill. Some algae species also produce toxins. In Florida, these include "Aphanizomenon", "Anabaena" and "Microcystis". Some notable fish kills in Louisiana in the 1950s were due to a pesticide called endrin. Natural instances of toxic conditions can occur, especially in poorly buffered water. Aluminium compounds can cause complete fish kills, sometimes associated with autumn turn-over of lakes leading to complex chemical interactions between pH, calcium ions and complex polymeric salts of aluminium.