Katrina Floodwaters
Not as Toxic to Humans as Previously Thought, Study Says
October 14, 2005
The floodwaters that inundated New Orleans
immediately following Hurricane Katrina were similar in content
to the city’s normal storm water and were not as toxic as
previously thought, according to a study by researchers at
Louisiana State University. Their study, the first peer-reviewed
scientific assessment of the water quality of the Katrina
floodwaters, is good news for those who’ve been exposed directly
to the floodwaters, the scientists said.
But the LSU researchers caution that the same
floodwaters that were pumped back into Lake Pontchartrain
contain high levels of some toxic metals, especially copper and
zinc, and could pose a long-term danger to the area’s aquatic
life, which are more sensitive to the metals than humans. Their
findings appeared in the Oct. 11 online issue of the American
Chemical Society’s journal Environmental Science & Technology.
"What we had in New Orleans was basically a
year’s worth of storm water flowing through the city in only a
few days," said study leader John Pardue, Ph.D., an
environmental engineer and director of the Louisiana Water
Resources Research Institute at LSU in Baton Rouge. "We still
don’t think the floodwaters were safe, but it could have been a
lot worse. It was not the chemical catastrophe some had
expected."
Some experts had predicted that the
floodwaters from Katrina could potentially destroy chemical
plants and refineries in the area, releasing a deadly brew
containing toxic levels of benzene, hydrochloric acid and
chlorine. Instead, high levels of bacteria and viruses were the
biggest human threat, not exposure to chemicals, Pardue and his
associates said.
The researchers obtained 38 floodwater samples
from widespread sections of New Orleans, primarily in the area
of the city known as the "East Bank," where the main human
contact with the floodwaters occurred. The samples, which
included both surface waters and bottom samples, were taken
within five to nine days after flooding occurred. Additional
samples were also obtained from the 17th Street drainage canal,
after pumping of the floodwater began, to evaluate the flood’s
impact on Lake Pontchartrain, the receiving body for the pumped
floodwaters.
The researchers found high levels of bacteria,
most likely from fecal contamination resulting from sewage.
Levels were within the range of typical storm water runoff in
the city, the scientists said. They also detected high levels of
lead, arsenic and chromium and noted that levels of these toxic
metals were also similar to those typically found in the area’s
storm water. In general, these particular findings were similar
to those obtained by the Environmental Protection Agency in
their initial assessment of the floodwaters, the researchers
said.
Gasoline was also a significant component of
the floodwaters, as measured by elevated levels of three of its
components: benzene, toluene and ethylbenzene. These compounds
were somewhat elevated in comparison to typical storm water
runoff, the researchers said. The chemicals most likely came
from cars and storage tanks submerged in the floodwaters, they
added.
Compounds found in common household chemicals
were also detected in the floodwaters, Pardue said. The waters
contained chemical compounds from aerosol paints, insecticides,
caulking compounds, rubber adhesives and other common
substances, but at levels that typically do not create concern
for human health.
If the floodwaters had occurred in another
location near more industrial sites in the city and if the wind
damage or water surge had been more severe, then the resultant
floodwaters could have been a more serious toxic threat, Pardue
said. "Instead, the city filled slowly, like a bathtub, and the
water velocities and forces on the buildings, including chemical
storage facilities, were relatively benign." The large volume of
floodwater also diluted the potency of many of the chemicals, he
added.
While serious toxicity to human life was
largely avoided, the floodwater may pose a chemical risk to
aquatic life in the area, Pardue said. He believes that low
oxygen levels in the water that is being pumped back into Lake
Pontchartrain could result in fish kills. He also said that
heavy metals being discharged into the lake, particularly copper
and zinc, can be toxic to fish and other marine life and may
bioaccumulate and contaminate seafood collected from the region.
More studies are needed to assess the long-term impact of the
flood on aquatic life, Pardue said.
Funding for this study was provided by the
Louisiana Water Resources Research Institute and the LSU Center
for the Study of Public Health Impacts of Hurricanes.
Source: The American Chemical Society
October 14, 2005 |