[Pharmwaste] Acetominophen forms toxics during wastewater chlorination

[Tenace, Laurie]

http://pubs.acs.org/subscribe/journals/esthag-w/2005/nov/science/as_acetamino
phen.html

Acetaminophen forms toxics during wastewater chlorination
Disinfection of wastewater can lead to the formation of unwelcome byproducts
from pharmaceuticals.
Acetaminophen, the most widely used painkiller in the world and the active
ingredient in over-the-counter drugs like Tylenol, may be transformed into
toxic compounds during chlorination in wastewater treatment plants, according
to research posted today on ES&T's Research ASAP website (10.1021/es0509073).
The research suggests that the scientists need to look more carefully at what
happens when the pharmaceuticals being found in waterbodies throughout the
world are subjected to wastewater treatment.

 
Photodisc
Oxidation of pharmaceuticals during wastewater chlorination can lead to
worrisome byproducts.The occurrence of pharmaceuticals in the environment has
received a lot of interest following a study by the U.S. Geological Survey
(USGS) (Environ. Sci. Technol. 2002, 36, 1202-1211), but little is known
about their potential transformation during wastewater and drinking-water
treatment. According to the USGS study, acetaminophen, which is also known as
paracetamol, is one of the most frequently detected anthropogenic compounds
in streams in the U.S.

Chlorination is the most common chemical method for wastewater and
drinking-water disinfection in the U.S. Under conditions simulating
wastewater disinfection, acetaminophen reacted with hypochlorite to form a
variety of products, two of which were identified as toxic
compounds-1,4-benzoquinone and N-acetyl-p-benzoquinone imine (NAPQI)-by
authors Mary Bedner and William MacCrehan of the U.S. National Institute of
Standards and Technology. After a 1-hour treatment with 4 milligrams per
liter (mg/L) of chlorine, these byproducts comprised 25% and 1.5% of the
initial acetaminophen concentration, respectively. Typical chlorine
concentrations used in wastewater chlorination range from 2 to 10 mg/L, with
a usual contact time of 5 minutes to 1 hour.

"This is one of the first papers that details the products of chlorine
reaction of a pharmaceutical," says David Sedlak of the civil and
environmental engineering department at the University of California,
Berkeley. He stresses the importance of studying the reaction products of
pharmaceuticals more closely, because they can be more toxic or more stable
than the parent compounds. "Otherwise, when looking at pharmaceuticals in the
environment, we may simply not be looking at the right compounds," Sedlak
says. He predicts that this type of reaction will also play a role in other
disinfection techniques, such as ozonation or reaction with chloramines.

It would be interesting to see whether 1,4-benzoquinone and NAPQI can be
measured in real wastewater treatment plants, says Bedner, who acknowledges
that these compounds are not very stable and, therefore, are unlikely to
persist in the environment. They could nonetheless have an ecological impact
downstream of the treatment area in effluent-dominated environments, Sedlak
says. In addition, changes in the dose of chlorine (which can be caused by
variations in the volume of the wastewater influent) may lead to a buildup of
these compounds in the treatment plant, he says.

NAPQI is a known liver toxin. It is also generated in the human body during
acetaminophen metabolism and can be responsible for lethality in overdoses of
the drug. 1,4-Benzoquinone, a hydrolysis product of NAPQI, is a benzene
metabolite suspected of causing genotoxic and mutagenic effects. In fact,
acetominophen's potential transformation to toxic products triggered Bedner's
interest in the drug's behavior during wastewater treatment. "Acetaminophen
is so common these days, since it is added to all sorts of sinus and cold
medicines," she says, "but it also has this dark side to its oxidation
chemistry that we don't usually acknowledge."

"This paper provides a good example of why we should consider disinfection
chemistry when we evaluate pollutant fate during municipal wastewater
treatment," says environmental chemist Michael Dodd, who is with the Swiss
Federal Institute of Aquatic Science and Technology (Eawag) and has
investigated the reactions of chlorine and ozone with a number of
antibacterial agents. "Municipal wastewater oxidation will only lead to small
changes in most reactive pollutant molecules," says Dodd, "but even minor
structural modifications can dramatically alter some compounds' biochemical
or physicochemical properties."

We are just beginning the second phase in the study of pharmaceuticals, says
Sedlak, who draws parallels to the history of pesticide research. Now that
researchers have determined the occurrence of the parent compounds, they can
begin to investigate potential reaction products, especially those that could
be more toxic or stable than the parent compounds. Dodd agrees, adding that
parent compounds should be prioritized by some basic considerations such as
modes of action, reported concentrations, or expected reactivities with the
active compounds used for different wastewater treatment technologies. "Many
different pharmaceuticals have been detected in wastewaters," he says, "so
it's important to keep the focus on the compounds likely to be most
significant." 

Laurie J. Tenace
Environmental Specialist
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us
 
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