More than forty research papers highlight the effects of emerging
contaminants on human health and the environment in the December 2006 issue
of the journal Environmental Science & Technology, among their
number are reports on nanoparticles, pharmaceuticals, disinfectant
by-products, and fluorochemicals.
“It might be tempting to define emerging contaminants as one thing or
following certain criteria but it’s not that simple,” says the journal’s
guest editor Jennifer Field of Oregon State University. The following
Spotlight editorial reveals some of the issues and diversity of materials
studied as well as highlighting a significant technology that might allow
decontamination for certain materials to be carried out. An audio summary
from the journal’s editors is available as an mp3 download:
http://pubs.acs.org/journals/esthag/audio/2006/vol40issue23.mp3
Aggregating buckyballs
Fullerenes, the all-carbon molecules with the soccer ball shape better known
as buckyballs can form nanoscopic aggregates in water. Volodymyr Tarabara
and his colleagues at Michigan State University and India’s Industrial
Toxicology Research Centre have found that these aggregates can damage DNA
in human lymphocytes. This is the first study to raise serious concerns
about the potential risk these nanoparticles pose to human health and the
environment, the researchers claim, having taken earlier research a step
further.
The team found “a strong correlation between the presence of [fullerene
aggregates] and DNA damage.” Water is a likely pathway for future human
exposure to buckyballs and other nanoparticles, Tarabara says. Any inherent
risk has to be weighed against the potential benefits the fullerenes might
offer medicine and energy transmission technologies, however. Quantities,
likely exposure, and environmental persistence must also be considered in a
long-term risk assessment.
Links
Volodymyr Tarabara paper
Volodymyr Tarabara website
Accumulating PBDEs
The flame retardant compounds known as PBDEs (polybrominated diphenyl
ethers) are accumulating at an unprecedented rate in the top predator fish
of the North American Great Lakes. According to Deborah Swackhamer and
colleagues at the University of Minnesota, the PBDEs pose a similar
environmental hazard as the now banned polychlorinated biphenyls (PCBs).
She and her colleagues have carried out the first study to measure six
PBDEs in water and their reach into the aquatic food chain. They
demonstrated that the levels of some PBDEs in lake trout were ten million
times higher than the surrounding water. Which is not quite as surprising as
it seems given that they are looking at accumulation in this fish because
they suspected that it would be high. For comparison, the PBDE is present at
incredibly low concentrations in the water, 0.2 to 10 picograms per litre (a
picogram is a millionth of a millionth).
Moreover, Swackhamer estimates that a person eating one lake trout fillet
would consume more PBDEs than from a lifetime of drinking Lake Michigan
water. Again, that is not quite as astounding or worrying a thought as the
researchers would have readers believe given the low concentration of these
chemicals in the water itself.
That said, the finding could help explain why human PBDE levels in North
American are higher than elsewhere in the world. Definitive toxicology
testing of PBDEs has not yet labelled these compounds as carrying the same
risk to health as PCBs.
Links
Deborah Swackhamer paper
Deborah Swackhamer website
Decontaminating NDMA
Two new approaches to ground water remediation could help eliminate the
cancer-causing material NDMA (N-nitrosodimethylamine) from
contaminated ground and drinking water, according to Martin Reinhard and
colleagues at Stanford University and the University of Illinois,
Urbana-Champaign.
NDMA has been classified as a likely human carcinogen by the US
Environmental Protection Agency. It often forms in water that is disinfected
with chlorine-containing compounds, and in particular chloramine. Removal is
difficult, but now Reinhard and his colleagues have shown that noble metal
catalysts, such as palladium, can destroy NDMA under ambient conditions.
They are now working to fine tune the chemistry and suggest that it should
be possible to reduce NDMA concentrations with this technology to a few
parts per trillion. The researchers also suggest that the same approach
might be able to decontaminate water affected by other compounds.
NDMA also can be formed by the oxidation of another material UDMH
(1,1-dimethylhydrazine), which is used in rocket fuel production. As a
result, NDMA and a co-contaminant, perchlorate, which also is used in rocket
fuel and munitions, often infiltrate ground water near aerospace facilities.
Perchlorate disrupts normal thyroid gland function.
Valentine Nzengung and colleagues at the University of Georgia have found
that pre-rooted trees, such as willows and poplars, which soak up tremendous
amounts of water, can remove almost 94 percent of the NDMA from such land
within 50 days and 100 percent of the perchlorate in 70 days. The trees are
effective in bioremediation at the concentration ranges most commonly found
in contaminated ground water near such facilities.
This is the first research that offers a cost-effective way of using plants
and trees to manage the spread of ground water contaminated with NDMA or NDMA
and perchlorate, Nzengung says.
Links
Martin Reinhard paper
Martin Reinhard website
Valentine Nzengung paper
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