Four Mile Run has elevated levels of fecal coliform bacteria:
- Fecal coliform has historically been used as an indicator for E. Coli reflecting the potential risk of gastrointestinal illness for humans in contact with the water.
- The higher the bacteria levels the more likely one will be to get sick from contact with the water.
- There is much debate surrounding the use of fecal coliform as an indicator and the EPA has encouraged states to switch to an E. coli standard which more closely correlates higher bacteria levels with risk of human illness.