Because iron is well known for its ability to bind arsenic,
Colvin's group repeated the experiments in arsenic-contaminated
water and found that the particles would reduce the amount of arsenic
in contaminated water to levels well below the EPA's threshold for
U.S. drinking water.
Colvin's group has been collaborating with researchers from Rice
Professor Mason Tomson's group in civil and environmental engineering
to further develop the technology for arsenic remediation. Colvin
said Tomson's preliminary calculations indicate the method could
be practical for settings where traditional water treatment technologies
are not possible. Because the starting materials for generating
the nanorust are inexpensive, she said the cost of the materials
could be quite low if manufacturing methods are scaled up. In addition,
Colvin's graduate student, Cafer Yuvez, has been working for several
months to refine a method that villagers in the developing world
could use to prepare the iron oxide nanoparticles. The primary raw
materials are rust and fatty acids, which can be obtained from olive
oil or coconut oil, Colvin said.
###
Additional co-authors include research scientist Amy Kan, postdoctoral
research associate William Yu and graduate students John Mayo, Arjun
Prakash, Joshua Falkner, Sujin Yean, Lili Cong and Heather Shipley.
The research is sponsored by the National Science Foundation.
Contact: Jade Boyd
Rice University
Low Doses Of Arsenic Have Broad Impact On Hormone Activity
Main Category: Endocrinology News
Article Date: 07 Dec 2006 - 18:00 PST
Dartmouth Medical School investigators are learning more about how
low doses of arsenic, such as the levels found in drinking water
in many areas of the United States, affect human physiology. In
a paper published online in the journal Chemical Research in Toxicology,
the researchers report that three different steroid hormones all
show similar responses to arsenic, suggesting a broader effect and
a common mechanism of arsenic on how these hormones function.
"Since most of the health consequences of exposure to arsenic
- various cancers, diabetes, heart and vascular disease, reproductive
and developmental effects, etc. - involve these same steroid receptors,
we think that disruption of their normal function could explain,
in large part, how arsenic can influence so many disease risks,"
says Joshua Hamilton, one of the authors on this study and the director
of the Center for Environmental Health Sciences at Dartmouth and
Dartmouth's Superfund Basic Research Program on Toxic Metals.
Hamilton's laboratory had earlier found that arsenic disrupts the
activity of the glucocorticoid receptor, and this follow up study
considered the progesterone and mineralocorticoid receptors, which
regulate a wide range of biological processes. This current work
was done in collaboration with Jack Bodwell, the lead author on
this paper and a research associate professor of physiology at Dartmouth
Medical School.
Hamilton, Bodwell, and their team found that arsenic appears to
suppress the ability of all three of these critical receptors to
respond to their normal hormone signals. Chemicals that disrupt
steroid hormone receptor signaling are called endocrine disruptors,
and this study provides further evidence that arsenic, a metal,
does not behave like other endocrine disruptors such as pesticides.
"Arsenic does not activate these receptors, as some endocrine
disruptors do, by mimicking the natural hormone, nor does it block
the ability of the normal hormones to activate their specific receptor,
as most other endocrine disruptors do," says Hamilton, who
is also a professor of pharmacology and toxicology at Dartmouth
Medical School. "Nor does it affect the ability of the hormone-activated
receptor to move to the nucleus of the cell or to bind to DNA to
initiate gene expression. Yet, somehow arsenic still strongly affects
the ability of these hormone-activated receptors to regulate gene
expression. There's still a lot more to learn."
The study also looked into the effects of different levels of arsenic
on these receptors. At very low doses (comparable to what is found
in drinking water at the current and previous U.S. regulatory limits,
in the range of 5-50 ppb) arsenic enhances hormone-stimulated gene
expression, by two- to three-fold. At slightly higher doses (in
the range of 50-200 ppb, commonly found in drinking water from contaminated
wells in New Hampshire and elsewhere in the U.S.) arsenic has the
exact opposite effect, strongly and almost completely inhibiting
hormone-stimulated gene expression by these receptors. This non-conventional
dose-response suggests that arsenic might have very different biological
effects at the lower and higher doses.
"Elucidating these complex biological effects of arsenic on
hormone signaling at different doses will be critical to our overall
understanding of how arsenic influences human health, and should
be considered as an important component of determining the overall
disease risk of people who are exposed to arsenic in their drinking
water, " says Hamilton.
###
The work is funded by grants to Dartmouth collaborators Hamilton
and Bodwell from the National Institute of Environmental Health
Sciences, a component of the National Institutes of Health. Both
researchers are members of the NIEHS-funded Superfund Basic Research
Program at Dartmouth and Dartmouth's Center for Environmental Health
Sciences. Co-authors on the study include Julie A. Gosse, and Athena
P. Nomikos, both of Dartmouth and both recipients of training fellowships
from Dartmouth's Superfund Basic Research Program.
Contact: Sue Knapp
Dartmouth College
Arsenic Inhibits DNA Repair
Main Category: Water - Air Quality / Agriculture News
Article Date: 29 May 2006 - 1:00 PST
Dartmouth researchers, working with scientists at the University
of Arizona and at the Department of Natural Resources in Sonora,
Mexico, have published a study on the impact of arsenic exposure
on DNA damage. They have determined that arsenic in drinking water
is associated with a decrease in the body's ability to repair its
DNA.
"This work supports the idea that arsenic in drinking water
can promote the carcinogenic effects of other chemicals," says
Angeline Andrew, the lead author and a research assistant professor
of community and family medicine at Dartmouth Medical School. "This
is evidence that it's more important than ever to keep arsenic out
of drinking water."
The study, which was published online on May 10, 2006, in the journal
Environmental Health Perspectives, examined the drinking water and
measured the arsenic levels in samples of urine and toenails of
people who were enrolled in epidemiologic studies in New Hampshire,
and in Sonora, Mexico.
Andrew and her colleagues examined the data in conjunction with
tissue samples from the study participants to determine the effect
of arsenic on DNA repair. To further corroborate their findings,
the researchers conducted laboratory studies to examine the effects
of arsenic on DNA repair in cultured human cell models.
"The DNA repair machinery normally protects us from DNA-damaging
agents, such as those found in cigarette smoke," says Andrew.
"The concern is that exposure to drinking water arsenic may
exacerbate the harmful effects of smoking or other exposures."
Andrew explains that in regions of the United States where the
rock contains higher levels of arsenic, the greater the likelihood
that drinking water sources contain some potential adverse levels
of the toxin. While the levels of arsenic in municipal water systems
are regularly monitored, there is no mandated testing of arsenic
levels in private wells. This is of particular concern since the
regions where arsenic levels are high are in rural regions, such
as New Hampshire, Maine, Michigan and some regions of the Southwest
and Rockies. Private wells are common in these areas as primary
sources of drinking water.
(More information on drinking water testing and remediation options
can be found from the NH Department of Environmental Services: des.state.nh.us/ws.htm
or the US Environmental Protection Agency: epa.gov/region1/eco/drinkwater/private_well_owners.html)
Andrew's co-authors on this paper are: Jefferey Burgess, Maria
Meza, Eugene Demidenko, Mary Waugh, Joshua Hamilton, and Margaret
Karagas, all from Dartmouth Medical School, the Department of Environmental
and Community Health at the University of Arizona, or the Department
of Natural Resources at the Technological Institute of Sonora, Mexico.
The research was supported by funding from the National Institutes
of Health, the National Institute of Environmental Health Sciences,
the National Cancer Institute, the Dartmouth and Arizona Superfund
Programs, and the American Society of Preventive Oncology.
Sue Knapp
Sue.Knapp@Dartmouth.edu Dartmouth College
http://www.dartmouth.edu
UC Berkeley Study Finds In Utero Arsenic Exposure From Drinking
Water Is Tied To Lung Disease And Cancer In Adults
Main Category: Water - Air Quality / Agriculture News
Article Date: 30 Mar 2006 - 1:00 PST
Children who are exposed to high levels of arsenic in their drinking
water are seven to 12 times more likely to die of lung cancer and
other lung diseases in young adulthood, a new study by University
of California, Berkeley, and Chilean researchers suggests.
The risk of dying due to bronchiectasis, usually a rare lung disease,
is 46 times higher than normal if the child's mother also drank
the arsenic-contaminated water while pregnant, according to the
study. These findings provide some of the first human evidence that
fetal or early childhood exposure to any toxic substance can result
in markedly increased disease rates in adults.
"The extraordinary risk we found for in utero and early childhood
exposure is a new scientific finding," says the study's lead
author, Allan Smith, professor of epidemiology at UC Berkeley's
School of Public Health. "I sometimes ponder the improbability
that drinking water with concentrations of arsenic less than one-thousandth
of a gram per liter could do this, and think that I've got to be
wrong. But our years of working with arsenic exposure in India and
Chile tie in with this study perfectly."
The paper will appear in the July print issue of Environmental
Health Perspectives and is already posted on its Web site.
Classified as a semi-metal, the element arsenic is one of the most
potent cancer-causing agents known. Skin, bladder and lung cancer
rates are substantially higher in regions where the tasteless, colorless
substance occurs in drinking water. A recent study by Smith showed
that adults exposed to arsenic can also develop decreased lung function
similar to that experienced by cigarette smokers. And, in a paper
to be published on April 1 in the American Journal of Epidemiology,
Smith and his colleagues provide evidence that women exposed to
high concentrations of arsenic during pregnancy experience six-fold
increases in stillbirths and other adverse effects.
Arsenic is particularly prevalent in Region II, a province in the
north of Chile and one of the driest places on earth. In 1958, the
cities there of Antofagasta and neighboring Mejillones tapped into
arsenic-laden rivers to supply their growing populations with water.
For the next 13 years, until an expensive arsenic removal plant
was installed, the water supply for all residents in the cities
was laced with an average of 860 micrograms per liter of arsenic.
In contrast, the standard for arsenic in drinking water in the United
States was recently dropped from 50 micrograms per liter to 10 micrograms
per liter, with compliance required in 2006. (A microgram is a millionth
of a gram.)
With such clear-cut exposure to arsenic, the unfortunate Chilean
cities became a tragic natural experiment for studying the effects
of arsenic on humans.
From earlier work he and others conducted in India, Smith knew
that arsenic is associated with bronchiectasis, a rare lung disease
that causes distortion and dilation of the bronchi, eventually leading
to chronic infections. A study involving death certificates for
young adults in Antofagasta and Mejillones, Smith realized, would
reveal whether lung cancer and bronchiectasis could also occur as
a result of childhood exposure to arsenic. Working with colleagues
Guillermo Marshall and Catterina Ferreccio from the Pontificia Universidad
Católica de Chile in Santiago, Smith compared the death rates
from 1989 to 2000 of young adults in the two cities with the rates
in the rest of Chile, outside of Region II. The team focused on
two groups: those born between 1951 and 1958, when the water supply
to the cities had relatively low arsenic concentrations, and those
born during the high-exposure period of 1958 to 1971.
Both groups, they reasoned, would have been exposed to high levels
of arsenic throughout some or most of their childhoods, but the
second group would also have been exposed in utero, that is, while
in the womb. Exposure for both groups would have abruptly declined
at the same time, in 1971, when the arsenic removal plant went online.
The researchers' findings were dramatic. For people exposed to arsenic
only as children, the death rate from lung cancer was seven times
greater than in the rest of Chile, while the death rate from bronchiectasis
was 12 times greater. For those with both early childhood and in
utero exposure, the death rate from lung cancer was six times greater
than that in the rest of Chile, and the death rate from bronchiectasis
was an astonishing 46 times greater.
In absolute numbers, there were nine deaths from bronchiectasis,
16 from lung cancer and seven from other lung diseases in adults
aged 30 to 49 who were born during the period of high exposure.
In the year 2000, there were about 300,000 people living in the
two cities where the study was conducted.
"In all my career, these are the most amazing findings I've
confronted so far," Smith says. "Their magnitude is unparalleled.
Not only are these the highest death rates for lung cancer and bronchiectasis
ever discovered among young adults, but they are also the strongest
evidence I know of to date that implicates not just arsenic, but
any environmental exposure in utero or in early childhood to any
adverse health effect in adults."
Putting these results in perspective, studies have found that the
rates of early-adult lung cancer among survivors of the atomic bombings
at Hiroshima and Nagasaki who were exposed to high levels of radiation
before birth or as children are many times lower than those in Antofagasta
and Mejillones, as are the rates among young adults exposed to secondhand
tobacco smoke as children. Only active smoking itself results in
lung cancer rates higher than the seven-fold increase found in his
study, Smith says.
###
The work was conducted by the Arsenic Health Effects Research Program
at UC Berkeley's School of Public Health and funded by the National
Institute of Environmental Health Sciences, one of the National
Institutes of Health. Other researchers who worked on the study
are Yan Yuan, Jane Liaw, Ondine von Ehrenstein and Craig Steinmaus,
all with the Arsenic Health Effects Research Program.
The paper, "Increased Mortality from Lung Cancer and Bronchiectasis
in Young Adults Following Exposure to Arsenic In Utero and Early
Childhood," is available online at: http://www.ehponline.org/docs/2006/8832/abstract.html
More information about the Arsenic Health Effects Research Program
can be found at: http://ist-socrates.berkeley.edu/~asrg/research.html
Contact: Liese Greensfelder
lieseg@berkeley.edu
University of California - Berkeley
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