Study: Antibacterial hand soaps are changing the makeup of life in urban streams

The Chicago river

Photo by flickr user yuan2003

Triclosan, the chemical that gives many antibacterial soaps their germ-killing abilities, is collecting in streams and altering the balance of naturally occurring bacteria, according to a study of Chicago-area waterways. The chemical kills off weaker bacteria and encourages the growth of more resistant strains. The study authors warn that this process could “diminish the usefulness of important antibiotics.”

As Miles O’Brien recently reported, water that goes down your drain gets treated and cleaned at waste water treatment plants, except when it doesn’t. Many urban sewer systems are allowed to overflow into the rain sewers when they’re overloaded, meaning that soapy water can flow from your sink, right into a nearby stream. Tests on Chicago streams showed high concentrations of triclosan downstream from sewer overflows.

Artificial stream experiments conducted at Loyola University confirmed field findings that triclosan exposure triggers an increase in triclosan-resistant bacteria. In addition to the creation of these resistant bacteria, researchers also found a decrease in the diversity of benthic bacteria and a shift in the composition of bacterial communities. Most notable were a 6-fold increase in cyanobacteria and a dramatic die-off of algae.

Watch Miles wade through sewers beneath the streets of Detroit in his January report: