PPCPs are being detected in groundwater, streams, rivers, lakes, and reservoirs in the United
States at very low concentrations, and have commonly been detected in combinations of
chemicals. Most often, contaminants that we traditionally have looked for in water have only
been analyzed for at concentrations above micrograms per liter (parts per billion) or milligrams
per liter (parts per million). Research projects focusing on PPCPs have employed more advanced
analytical techniques in order to detect PPCPs at nanograms per liter which is approximately
equivalent to one part per trillion. To put one part per trillion in perspective, the Water
Environment Research Foundation has explained that a part per trillion is about one second in
32,000 years or one inch in 33 round-trips to the moon or 1 penny in $10 billion. On average,
pharmaceuticals detected in U.S. drinking water are below 10 parts per trillion, except for
caffeine which averages 25 parts per trillion. At that concentration, a person would have to drink
more than five million bottles (20 ounces each) of water to have the same amount of caffeine in
one cup of coffee (about 75 milligrams). Many experts correctly make the point that just because
a substance can be detected does not mean it is harmful to humans.