Acetaminophen forms toxics during wastewater chlorination

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November 30, 2005

Acetaminophen forms toxics during wastewater chlorination

Disinfection of wastewater can lead to the formation of unwelcome

byproducts from pharmaceuticals.

http://pubs.acs.org/subscribe/journals/esthag-w/2005/nov/science/as_acetamin

ophen.html

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 & Ts 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.

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, 12021211), 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

compounds1,4-benzoquinone and N-acetyl-p-benzoquinone imine (NAPQI)by

authors Bedner and 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 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,

acetominophens potential transformation to toxic products triggered

Bedners interest in the drugs 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 dont 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 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 its important to keep the

focus on the compounds likely to be most significant. ANKE SCHAEFER

Copyright © 2005 American Chemical Society

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Sheri Nakken, R.N., MA, Classical Homeopath

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