Depending on the desired definition of the word "contaminant"
Alkyl Benzene Sulfonate is more likely the answer. Linear Alkyl
Sulfonates are far more readily biodegraded than Alkyl Benzene
Sulfonate due to their relative chemical structures. Alkyl Benzene
Sulfonate can cause issues in waterways such as eutrophication,
which in turn can lead to algal blooms.