Dr. Jenny Deakin:

Phosphates are a slightly different story. The risky areas in the landscape for phosphates are poorly draining soils and the phosphate runs off over land often bound with sediment and gets into our streams, rivers and lakes. When our phosphorus is in that environment and the levels are too high, and it only takes a very low amount of phosphorus to cause a biological response, but when we get that biological response, it can lead to algal blooms, which have impacts on swimmers. There have been some reports of illnesses in dogs and the like from toxic algae that they can develop.