The exact mechanisms of synergy are unknown. In a recent experiment with yeast, the synergistic effects of a variety of contaminants suggested that scientists barely understand how the modern cocktail of chemicals present in water affects the human body, a potentially alarming prospect for water engineers. For now, all contaminants are regulated individually, as that is the way scientists traditionally calculate public health threats. In the real world, each of us is exposed not just to one contaminant, but to tens of thousands. See environmental estrogens .
Triazines are currently present in both ground and surface waters.
These and other triazines are a cheap way for farmers to kill a wide range of weeds. Chloroform is the best known example. THMs cause 10,000 cases of colon and bladder cancer annually. The chlorine industry strenuously opposes closer regulation of THMs. Turbidity in water can be harmless, or it may indicate to water engineers that extra filtration, flocculation, and sedimentation is needed.