Pharmaceuticals
"The huge quantities of medicines ending up as waste or in aquatic systems are a major environmental health issue. The increasing documentation of low dose effects makes pharmaceuticals a priority area from an environmental health perspective." — Health Care Without Harm: Preventing Environmental Damage from Pharmaceuticals
The manufacturing process is responsible for some of the drugs that end up in the environment, but probably the majority come from consumers on medication whose urine is flushed down the toilet.
Unfortunately, most standard water treatment facilities don't (or can't) remove medications before releasing wastewater into rivers. From there, they find their way into the water table and drinking water supplies.
Probably the only reliable way to avoid these compounds is to use a good water filter (such as the Alexapure or Berkey filters) for your drinking water.