Please find below some important considerations for members in the United
States regarding drinking water as a potential source of lead if your child
is lead poisoned. Who knows what happens in the rest of the world? Maybe
it's time to send questions to your local water authority...
Regards
Elizabeth O'Brien

----- Original Message -----
From: <Fitzdon@...>
To: <leadnet@...>
Sent: Monday, August 07, 2006 2:06 AM
Subject: [Leadnet] Lead in water linked to coagulant


Science News - August 2, 2006

Lead in water linked to coagulant

It's not just chloramines. Coagulants used in drinking-water facilities can
create lead problems too.
High levels of lead in drinking water that poisoned a child in Durham, N.C.,
probably resulted from a change in the coagulant used to remove organic
matter, says a corrosion scientist who tested the Durham water. The incident
raises
the specter of similar undetected problems in other parts of the U.S., says
Marc Edwards, a corrosion engineer at Virginia Polytechnic Institute and
State
University. This case is especially vexing because Durham's routine
water-quality monitoring, which is required by the U.S. EPA's Lead and
Copper
Rule,
failed to detect the problem in 2004.



Jupiterimages

Routine monitoring missed Durham, N.C.'s lead problem.

Since the 2004 Washington, D.C., lead crisis [316KB PDF]drew attention to
lead in drinking water, a few cities that were once meeting the EPA action
limit
have developed problems. Durham joins Greenville, N.C., and Stafford, Va.,
on
the list of cities where water-treatment changes enacted to reduce
disinfection byproducts have unexpectedly raised lead levels. Until now, the
prime
suspect for these cases was a switch from free chlorine to chloramines for
secondary
disinfection-the established cause of D.C.'s problem.

Besides switching to chloramines, all three cities changed from alum or
another nonchloride coagulant to ferric chloride to better remove organic
matter
and further reduce disinfection byproducts. This change increased the ratio
of
chloride to sulfate in the drinking water. When this ratio is >~0.58,
galvanic
corrosion occurs and erodes particles of solder, according to Edwards. This
process takes place even when other aspects of the water chemistry-such as
pH,
alkalinity, and the use of a phosphate-based corrosion inhibitor-should
prevent
lead contamination of water, he says.

The chloride-to-sulfate ratio was first reported as an important factor in
water corrosion in 1983 by scientists in the U.K. Edwards cited their work
in
a
1999 publication that indicated the ratio could be important at U.S.
utilities. A 2005 American Water Works Association report [1.3MB PDF] made
passing
mention of the ratio. Even so, most corrosion scientists and utilities
managers
contacted by ES&T were unaware of the issue.

In Durham, a doctor spotted the child's elevated blood lead level, >20
µg/dL,
during a routine examination this spring. Public-health officials linked the
boy's poisoning to drinking water after they found >800 ppb of lead in tap
water and no other source of lead in his mother's apartment, according to
Durham
County health officer Marc Meyer.

Paint, dust, or soil-not water-are generally considered major sources of
lead
exposure. Lead solder, banned in the mid-1980s, could potentially be a
significant source of lead in drinking water, according to Mary Jean Brown,
head of
the U.S. Centers for Disease Control and Prevention's lead poisoning
prevention branch. However, aging processes are thought to deposit various
films or
scales on top of the solder that protect it from corrosion. "If the aging
process
does not protect against this, then it would be new," she says.

Plant managers say that the problem is new. After the switch to ferric
chloride, Stafford plant manager Harry Critzer watched lead levels climb.
After
coagulants were changed, the lead levels quickly dropped below the action
limit.

Greenville had a similar experience. "We switched to ferric chloride at
about
the same time as we switched to chloramines," says Greenville plant manager
Barrett Lasater. "At first, we thought it was a dissolved-lead problem, so
we
changed our corrosion inhibitor, but this didn't have much of an effect.
EPA,
the state regulators, and other consultants didn't know what it was. There
is
no literature. There are no guidelines."

Most corrosion controls focus on soluble-lead leaching, but this is
different. It's about physical processes. "Because these are particles, it
means that
flow rate is important; the aerator is important," Lasater adds.

Aerators on or off, a seemingly minor detail, could explain why the Durham
health department found a problem that the water company missed. The health
department sampled with the aerators on. The water company took them off.
Although
the aerator on/off issue was highlighted in a previous ES&T article about
sampling in Washington, D.C., schools, where EPA Region 3 agreed to an
"aerators
off" sampling protocol, disagreement about how to sample still exists. "We
want to get a real-world sample that reflects what people are drinking,"
says
Meyer, who advocates leaving the aerators on.

A Region 4 EPA spokesperson tells ES&T that the water utility sampled
correctly and that the health department's procedure "differed from what's
required
by regulation," but the spokesperson declined to explain the results. EPA's
proposed revisions to the Lead and Copper Rule, released on July 6, are
silent
on
specific sampling issues. The proposals would require utilities to consult
with state regulators when contemplating a treatment change that might lead
to
corrosion.

But on July 26, EPA Office of Water assistant administrator Benjamin
Grumbles, in a letter to a Durham, N.C., newspaper, wrote, "The U.S.
Environmental
Protection Agency does not have stated guidelines concerning the removal of
faucet aerators before testing for lead in drinking water. We were unaware
that
water-treatment facilities may be making such a recommendation. Since this
matter
came to our attention, we have begun looking into it to determine whether we
need to provide supplemental guidance on the issue. We hope to make that
determination soon."

Lasater, who switched coagulant a few months ago, is waiting to see whether
the change solves Greenville's lead problem, and Durham's water company is
also
expected to stop using ferric chloride. North Carolina's experiences have
raised awareness of water as a source of elevated blood lead, says Meyer. In
Greenville, it took a year to determine that water was responsible for high
lead
levels in children. In Durham, it took a month. "Prior to Greenville, we
didn't
sample water when we investigated a home. Now, it's routine," he says.
-REBECCA RENNER

http://pubs.acs.org/subscribe/journals/esthag-w/2006/aug/science/rr_lead.html

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