So what exactly is in our lakes, rivers and streams? A full breakdown of all the chemicals in waterways would be too extensive to list here, and since each ecosystem is unique, the chemical signature in every lake, river and stream is slightly different. That said, it’s apparent that contamination of waterways is widespread. Here is a look at some of the more common problems.
Chemical contamination in rivers, lakes & streams
Almost half of all rivers and lakes in the U.S. (including the Great Lakes) are under a water contamination advisory at any given time, most of them due to mercury contamination. (Denworth, 2013) A U.S. Geological survey that studied the nation’s waterways between 1992 and 2001 found that more than 80% of urban streams and 50% of agricultural streams had pesticides, usually many combinations of them. The USGS has found that 75% of water in streams and rivers and 40% of groundwater samples in agricultural areas contained atrazine.
Medicine & pharmaceuticals in rivers & streams
As a result of recycled waste, rivers and streams contain trace amounts of contraceptives, antidepressants, blood pressure medicine, and antibiotics given to livestock. The concentration is generally low, in the parts per trillion, so it’s more of a problem for fish than humans at this point. But concentrations are steadily rising, and nobody knows for certain how this low-level cocktail of drugs is affecting us.
Fish caught downstream from sewage treatment plants in five U.S. cities contained traces of pharmaceuticals and toiletries, according to a study by Baylor University researchers. Although you’d have to eat a lot of fish for such small concentrations to have any impact on human health, it could be having an impact on marine life. Here is a sampling of the relative amount of chemicals found in fish pulled from Chicago’s North Shore Channel, along with the concentrations per gram:
- Carbamazepine: 33% (antiseizure; 2.3 manograms per gram)
- Diphenhydramine: 20% (antihistamine; 1.4 nanograms per gram)
- Norfluoxetine: 2% (antidepressant byproduct; 3.2 nanograms per gram)
- Diltiazem: 2% (antihypertensive; 0.13 nanograms per gram)
(National Geographic, April 2010, pp. 152-53)
Antibiotics in waterways
A U.S. Geological Survey found antimicrobial residues in 48% of 139 streams that were tested nationwide from 1999 to 2000. (Sayre, 2009) While this may seem harmless (antimicrobials, after all, kill pathogens), it has a very problematic side effect: Such low-level, widespread contamination of waterways allow potentially harmful pathogens to develop resistance or tolerance to antibiotics, which provides a breeding ground for superbugs that pose a threat to human health.