What's That Floating in Your Water?
May 11, 2001 -- Before you turn on the tap or twist open that
fancy bottled water, there are a few things you should know. Even well
regulated and tested drinking water can harbor potentially dangerous
contaminants, say members of the CDC's elite force of Disease Detectives.
The CDC researchers presented findings from two investigations
of drinking water safety at the 50th Annual Epidemic Intelligence Service
Conference held this week in Atlanta.
In the first study, Melinda J. Wilkins, DVM, MPH, and
colleagues examined infants whose mothers had consumed water containing low
levels of arsenic during pregnancy.
"It's well established that very high levels of arsenic are
associated with cancer. But very few reproductive studies done have looked at
arsenic at low levels. We needed to make sure," says Wilkins, a CDC officer
with the Michigan Department of Community Health.
The team analyzed birth records from nearly 320,000 babies born
between 1989 and 1998 in nine Michigan counties, looking specifically for low
birth weight, preterm birth, and small size for gestational age.
Wilkins says that they chose the area because the water there
has some of the highest arsenic levels in the country.
"This is a naturally occurring situation," she tells
WebMD. "The arsenic leaches out of the sandstone in the earth." It is
not caused by dumping, or any other foreign source. Those relatively high
levels still fall well within the EPA's current safety limit of 50 parts per
The team found no evidence that the higher-than-usual arsenic
levels in the drinking water had any ill effects whatsoever on the babies. For
each of the three variables, "the percentages were close to Michigan as a
whole, and not far from national averages," says Wilkins.
"At this point, mothers-to-be don't need to be overly
concerned about arsenic," says Wilkins. "Traditional risk factors like
smoking and drinking rank much much higher on the list of things to be
concerned about when they're pregnant," says Wilkins.
Still, she says, it can't hurt to be cautious, especially when
your baby's health is at stake.
For those whose water source is a private well, "we
recommend having the water tested. If levels are above 50 parts per billion,
you might consider using bottled water or changing the depth to be deeper or
shallower." And though it will clear your water of many other contaminants,
says Wilkins, "filtering will not remove arsenic."
In the second study, Valerie Garrett, MD, and colleagues with
the CDC's Foodborne and Diarrheal Disease Branch were called in to track down
the cause of a salmonella outbreak among infants in the southern Appalachian
region, in the southeastern U.S.
The team eventually tracked the problem to a batch of bottled
water processed at a large plant in North Georgia and marketed specifically for
infant use. While the source of the contamination has not been proved beyond a
doubt, Garrett says that local cave-dwelling salamanders are the likely
culprits. These animals shed bacteria into local springs, and the plant in
question had stored the processed water for bottling in the same tanks that had
held spring water.