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Event

 
      Byproduct of water disinfection process found to be highly toxic

15 Sep 2004  
http://www.medicalnewstoday.com/medicalnews.php?newsid=13413

A recently discovered disinfection byproduct (DBP) found in U.S. 
drinking water treated with chloramines is the most toxic ever found, 
says a scientist at the University of Illinois at Urbana-Champaign who 
tested samples on mammalian cells.

The discovery raises health-related questions regarding an Environmental 
Protection Agency plan to encourage all U.S. water-treatment facilities 
to adopt chlorine alternatives, said Michael J. Plewa [PLEV-uh], a 
genetic toxicologist in the department of crop sciences. "This research 
says that when you go to alternatives, you may be opening a Pandora's 
box of new DBPs, and these unregulated DBPs may be much more toxic, by 
orders of magnitude, than the regulated ones we are trying to avoid."

Plewa and colleagues, three of them with the EPA, report on the 
structure and toxicity of five iodoacids [EYE O-doe-acids] found in 
chloramines-treated water in Corpus Christi, Texas, in this month's 
issue of the journal Environmental Science & Technology. The findings, 
which appeared online in advance, already have prompted a call from the 
National Rural Water Association for a delay of EPA's Stage 2 rule aimed 
at reducing the amount of previously identified toxic DBPs occurring in 
chlorine-treated water.

"The iodoacids may be the most toxic family of DBPs to date," Plewa said 
in an interview. One of the five detailed in the study, iodoacetic acid, 
is the most toxic and DNA-damaging to mammalian cells in tests of known 
DBPs, he said.

"These iodoacetic acids raise new levels of concerns," he said. "Not 
only do they represent a potential danger because of all the water 
consumed on a daily basis, water is recycled back into the environment. 
What are the consequences? The goal of Stage 2 is to reduce DBPs, 
particularly the ones that fall under EPA regulations, and especially 
the ones that have been structurally identified and found to be toxic."

The use of chloramines, a combination of chlorine and ammonia, is one of 
three alternatives to chlorine disinfectant, which has been used for 
more than 100 years. Other alternatives are chlorine-dioxide and ozone. 
All treatments react to compounds present in a drinking water source, 
resulting in a variety of chemical disinfectant byproducts.

Some 600 DBPs have been identified since 1974, Plewa said. Scientists 
believe they've identified maybe 50 percent of all DBPs that occur in 
chlorine-treated water, but only 17 percent of those occurring in 
chloramines-treated water, 28 percent in water treated with 
chlorine-dioxide, and just 8 percent in ozone-treated water. Of the 
structurally identified DBPs, he said, the quantitative toxicity is 
known for maybe 30 percent.

Some DBPs in chlorine-treated water have been found to raise the risks 
of various cancers, as well as birth and developmental defects.

Corpus Christi's water supply has high levels of bromide and iodide 
because of the chemical makeup of the ancient seabed under the water 
source. Local water sources lead to different DBPs. Whether the types of 
iodoacids found in Corpus Christi's treated water might be simply a 
reflection of local conditions, and thus a rare occurrence, is not known.

The DBPs in Corpus Christi's water were found as part of an EPA national 
occurrence survey of selected public water-treatment plants done in 
2002. The survey reported on the presence of 50 high-priority DBPs based 
on their carcinogenic potential. The report, published in April, also 
identified 28 new DBPs.

Because so many new DBPs are being found in drinking water, Plewa said, 
two basic questions should be asked: How many are out there? And how 
many new ones will be formed as chlorine treatments are replaced with 
alternative methods?

Co-authors with Plewa on the EPA-funded study were Elizabeth D. Wagner, 
a scientist in the department of crop sciences at Illinois; Susan D. 
Richardson and Alfred D. Thruston Jr. of the EPA's National Exposure 
Research Laboratory; Yin-Tak Woo of the EPA's Risk Assessment Division, 
Office of Pollution Prevention and Toxics; and A. Bruce McKague of the 
CanSyn Chemical Corp. of Toronto.

Contact: Jim Barlow, Life Sciences Editor
jebarlow@uiuc.edu
217-333-5802
University of Illinois at Urbana-Champaign  http://www.uiuc.edu 
For updates and info, contact scott at planttrees dot org.