MARCH 22, 2015
Chlorine, a disinfectant commonly used in most wastewater
treatment plants, may be failing to completely eliminate pharmaceuticals from
wastes. As a result, trace levels of these substances get discharged from the
plants to the nation's waterways. And now, scientists are reporting preliminary
studies that show chlorine treatment may encourage the formation of new,
unknown antibiotics that could also enter the environment, potentially
contributing to the growing problem of antibiotic resistance.
The research, which will be presented today at the 249th
National Meeting & Exposition of the American Chemical Society (ACS),
suggests that a re-evaluation of wastewater treatment and disinfection practices
is needed.
"Pharmaceuticals that get out into the environment can
harm aquatic life, making them react slowly in the wild and disrupting their
hormone systems," notes Olya Keen, Ph.D. She adds that increased
antibiotic exposure, even at low levels in the environment, can lead to
development of antibiotic-resistant microbes and a general weakening of
antibiotics' abilities to fight bacterial infections in humans.
"Treated wastewater is one of the major sources of
pharmaceuticals and antibiotics in the environment," says Keen.
"Wastewater treatment facilities were not designed to remove these drugs.
The molecules are typically very stable and do not easily get biodegraded.
Instead, most just pass through the treatment facility and into the aquatic
environment."
But besides failing to remove all drugs from wastewater,
sewage treatment facilities using chlorine may have the unintended consequences
of encouraging the formation of other antibiotics in the discharged water.
Keen, graduate student Nicole Kennedy and others in her team at the University
of North Carolina at Charlotte ran several lab experiments and found that
exposing doxycycline, a common antibiotic, to chlorine in wastewater increased
the antibiotic properties of their samples.
"Surprisingly, we found that the products formed in the
lab sample were even stronger antibiotics than doxycycline, the parent and
starting compound," she adds. Keen has not yet identified all the
properties of these "transformation products," and that research is
now underway. She notes that these compounds could turn out to be previously
unidentified antibiotics.
Keen explains that the best solution may be to decrease the
amount of these drugs that reach a treatment plant in the first place.
Currently, disposal of pharmaceuticals is not regulated, however. So she urges
a greater emphasis on collecting and incinerating old pharmaceuticals, rather
than dumping them down the drain or placing them in the trash, which can lead
to harmful environmental exposures.
In addition, this research has applications to drinking
water treatment systems, most of which also use chlorine as a disinfectant, she
says. To purify drinking water, chlorine must remain in the distribution piping
system for hours, which blocks microbes from growing. But this also provides
ample time for chlorine to interact with pharmaceuticals that may be in the
water, encouraging development of new antibiotic compounds.
Source: www.sciencedaily.com
and acs.org