News
When It Rains, It Pours: Arctic Rivers Affect Global Water Cycle
According to researchers from the United Kingdom's Hadley Centre for Climate Prediction and Research, intensified precipitation from global warming is causing far northern rivers to discharge increasing amounts of freshwater into the Arctic Ocean.
Water exchange between the ocean, atmosphere, and land is called the global hydrological cycle. As Earth's climate warms, the rate of this exchange is expected to increase. As part of this process, high-latitude precipitation and, consequently, river runoffs are also expected to increase. This could change the distribution of water on Earth's surface, with important social and economic consequences.
It could also alter the balance of the climate system itself, such as the Atlantic thermohaline circulation, a kind of conveyor belt. Cold water flows southward in the Atlantic at great depths to the tropics, where it warms, rises, and returns northward near the surface. This flow helps keep northern Europe at a temperate climate, whereas the same latitudes in North America are sparsely settled tundra or taiga.
Writing in the journal Geophysical Research Letters (January 21, 2005), Hadley Centre researchers Peili Wu, Richard Wood, and Peter Stott noted that increased human-caused greenhouse gas emissions are expected to intensify the Arctic hydrologic cycle, that is, the cycle of water as it rains onto land and sea, runs off into rivers, and evaporates to continue the cycle. The increased Arctic precipitation is balanced by decreased precipitation in the tropics, they say.
Wu and his colleagues tested the model with four simulations that took into account both human inputs and natural factors, including solar variability and volcanic eruptions. The results showed a steady increase in Arctic river discharges, especially since the 1960s. The annual rate of increase since 1965 was 8.73 cubic kilometers (2.31 million gallons) per year, far greater than the long-term trend.
Seeking to determine the source of the upward trend of recent decades, the researchers asked first whether it could be the early part of the predicted increase in the global hydrological cycle, caused by global warming. Their simulations excluded human impacts in one instance and natural impacts in another, and included all factors in a third. They concluded that had there been no human inputs, the hydrological cycle would have shown no trend at all in the 20th century.
Had there been only human inputs and no natural ones, the long-term trend would be 50 percent higher than when all factors were considered, said the researchers. They conclude that over the past four decades, human activity played the major role in increased river flows into the Arctic. The observed data conform well to the predictions of the Hadley climate model regarding human inputs, and it is likely that the upward trend in river flow changes is part of the early stages of an intensified hydrologic cycle.
For more information, visit www.met-office.gov.uk/research/hadleycentre.
Arsenic-laced Well Water Associated With Increased Lung Cancer Risk
Residents of Taiwan who consumed drinking water with high levels of arsenic have a higher risk of lung cancer, with cigarette smokers from this group having an even greater risk, according to a study in the December 22/29, 2004 issue of the Journal of the American Medical Association (JAMA).
Arsenic is a naturally occurring element in soil and can contaminate drinking water, according to background information in the article. Residents of the southwestern and northeastern coasts of Taiwan had been drinking well water contaminated with a high concentration of arsenic before the establishment of the public drinking water system.
Chi-Ling Chen, PhD, of the College of Public Health, National Taiwan University, Taipei, Taiwan, and colleagues conducted a study to determine the dose-response relationship between ingested arsenic and lung cancer risk and the added effect of cigarette smoking on this risk.
The study included 2,503 residents in southwestern and 8,088 in northeastern arsenic-endemic areas in Taiwan who were followed up with for an average period of 8 years. Information on arsenic exposure, cigarette smoking, and other risk factors was collected at enrollment through a standardized questionnaire interview.
During the study follow-up period, there were 139 newly diagnosed cases of lung cancer. Residents with the highest level of arsenic exposure had a 3.29 times increased risk for lung cancer, after adjusting for various factors including age, sex, and cigarette smoking status at recruitment. Among nonsmokers, those who were exposed to the highest arsenic level had about twice the risk for lung cancer when compared with those with the lowest level of exposure. Among participants with the lowest arsenic level, those who had the highest cumulative cigarette smoking exposure had a 4-fold risk of lung cancer compared with nonsmokers. When compared with nonsmokers with the lowest levels of arsenic exposure, those who consumed well water with the highest arsenic levels and smoked for more than 25 pack-years had a more than 11-fold risk of lung cancer.
"Approximately 32 percent to 55 percent of lung cancer cases were estimated to be attributable to the combined effect of cigarette smoking and ingested arsenic, depending on the levels of both exposures," the authors wrote. "The synergy indices ranged from 1.62 to 2.52, indicating a synergistic effect of ingested arsenic and cigarette smoking on lung cancer."
"The reductions in cigarette smoking would likely reduce the lung cancer risk accompanied by exposure to arsenic, and similarly, reductions in arsenic exposure would reduce the lung cancer risk among cigarette smokers. Appropriate public health interventions, such as cigarette smoking cessation programs and reduction in arsenic concentration of drinking water, are warranted. Furthermore, it is essential to take cigarette smoking into consideration in the risk assessment and the determination of the maximal contamination level of arsenic in drinking water," the authors concluded.
The studies are available for free at www.jama.com.
Study Shows Warming Trend In Alaskan Streams
Water temperatures in Alaska's Lower Kenai Peninsula salmon streams have been teetering above the 55-degree Fahrenheit temperature limit, posing a substantial health risk to salmon habitat, according to a new report published by Alaska's Homer Soil and Water Conservation District.
According to the report, underwater temperature loggers placed in four area watersheds show that water temperatures rose above the upper limit on 54 days in 2002, 60 days in 2003, and 86 days in 2004.
The Homer district, in partnership with Cook Inlet Keeper, a watershed-based, non-profit organization, has been collecting water quality data on the region's economically important salmon streams since 1998.
"We monitored the streams to gain a better understanding of the frequency and extent of the elevated temperatures," said Sue Mauger, a stream ecologist for Cook Inlet Keeper. "To see these types of temperature increases in the streams is definitely a concern, especially when you consider that many of the communities here depend on commercial and recreational fishing and tourism."
Water temperature plays a critical role in the salmon incubation process, and warmer temperatures have been linked to a higher susceptibility to disease and a depletion of available oxygen and nutrients.
According to Paul Gannett, a spokesman for Onset Computer Corp., a Massachusetts-based manufacturer of dataloggers, stream temperature monitoring is key to understanding the impact local and global environmental changes have on stream ecosystems. "By looking at temperature profiles over time, researchers are better able to correlate specific environmental events with their impact on streams."
Mauger added, "It's easy to blame climate change, but we also need to look closely at other things we're doing in the watersheds. For example, in recent years we've lost over a million acres of white spruce forests from a bark beetle infestation. There has also been a dramatic increase in logging, road building, and real estate development. We don't know what effect this shift from a forested landscape to a more grassland-dominated ecosystem might have on stream temperatures."
To view a copy of the report, please visit www.inletkeeper.org/monitoring.htm.
Gently Down the Antibacterialized Stream?
Many rivers and streams in the United States are believed to contain a toxic antimicrobial chemical whose environmental fate was never thoroughly scrutinized despite large-scale production and usage for almost half a century, according to an analysis conducted by researchers at the Johns Hopkins Bloomberg School of Public Health. The chemical, triclocarban, has been widely used for decades in hand soaps and other cleaning products, but rarely was monitored for or detected in the environment. The new findings suggest that triclocarban contamination is greatly underreported. The study is published in the online edition of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society.
"We've been using triclocarban for almost half a century at rates approaching 1 million pounds per year, but we have essentially no idea of what exactly happens to the compound after we flush it down the drain," said the study's lead author, Rolf U. Halden, PhD, PE, assistant professor in the School's Department of Environmental Health Sciences and founding member of its Center for Water and Health.
The nationwide assessment of triclocarban contamination is based in part on an analysis of water samples collected from rivers in and around Baltimore, as well as from local water filtration and wastewater treatment plants. From the samples, Dr. Halden and his summer research intern, Daniel H. Paull, now a graduate student in the Chemistry department at Johns Hopkins University, observed the occurrence of triclocarban in the environment correlated strongly with that of triclosan, another commonly used antimicrobial chemical that has been studied in much greater detail because it is more easily detectable. Using an empirical model and published data on the environmental occurrence of triclosan, the researchers predicted triclocarban concentrations for 85 U.S. streams. The study results suggest that the antimicrobial contaminant is present in 60 percent of the U.S. water resources investigated, thereby making it the fifth most frequently detected contaminant among 96 pharmaceuticals, personal care products, and organic wastewater contaminants evaluated.
To determine the validity of the analysis, the researchers compared their predicted nationwide levels of contamination to experimentally measured concentrations in the Greater Baltimore region and found no statistically significant differences. The results also show that the levels of triclocarban in water resources nationwide are much higher than previously thought.
In surface water from the Baltimore region, the researchers detected triclocarban at concentrations of up to 6.75 micrograms per liter (parts per billion). This maximum concentration was 28-fold higher than previously reported levels, which are currently used by the U.S. Environmental Protection Agency (EPA) for evaluation of the ecological and human health risks of triclocarban.
"Along with its chemical cousin triclosan, the antimicrobial compound triclocarban should be added to the list of polychlorinated organic compounds that deserve our attention due to unfavorable environmental characteristics, which include long-term persistence and potential bioaccumulation. Triclocarban, for example, has an estimated half-life of 1.5 years in aquatic sediments. Do the potential benefits of antimicrobial products outweigh their known environmental and human health risks? This is a scientifically complex question consumers, knowingly or unknowingly, answer to everyday in the checkout line of the grocery store," said Dr. Halden.
"Co-Occurrence of Triclocarban and Triclosan in U.S. Water Resources" is available at pubs.acs.org/journals/esthag/index_news.html.
EPA Announces New Aircraft Drinking Water Quality Data
A second round of EPA testing shows that 17.2 percent of 169 randomly selected passenger aircraft carried water contaminated with total coliform bacteria. The latest round of tests were performed on domestic and international passenger aircraft at airports nationwide in November and December of last year. The results confirm the presence of bacteria at levels warranting continued EPA scrutiny.
The information is intended to help the public make informed decisions while traveling on aircraft. Passengers with compromised immune systems or other concerned passengers may want to request canned or bottled beverages and refrain from drinking tea or coffee unless made with bottled water.
Total coliform and E. coli are indicators that other disease-causing organisms (pathogens) may be present in the water and could potentially affect public health. When sampling identified total coliform in the water of a domestic aircraft, that aircraft was disinfected and retested to ensure that the disinfection was effective. In instances where foreign flag aircraft tested positive for total coliform, those airline companies were notified of the positive test results and advised to disinfect and retest the aircraft.
As part of the first round of sampling, EPA, during August and September 2004, randomly tested the water supplies on 158 aircraft nationwide. Aircraft tank water is used in the galleys and lavatory sinks. Initial testing of onboard water supplies revealed 20 aircraft (12.7 percent) with positive results for total coliform bacteria, with two of these aircraft also testing positive for E. coli. Following those tests, EPA announced that further testing would take place, and efforts were undertaken to reach agreements with airlines to more closely monitor water quality on planes.
In EPA's second round of water quality sampling, 169 aircraft were tested. The sampling included water from galley water taps as well as lavatory faucets. Testing found that 29 of these aircraft (17.2 percent) were total-coliform-positive. E. coli was not found in the 169 aircraft included in the second round. Adding together the results of the first and second rounds of testing, EPA tested 327 aircraft in 2004, with approximately 15 percent found to be total coliform positive.
Following the first round of airline water testing in November 2004, EPA announced that agreements had been signed with the following airlines to increase monitoring of water quality testing and disinfecting processes: Alaska Airlines, Aloha Airlines, American Airlines, America West, ATA Airlines, Continental Airlines, Hawaiian Airlines, JetBlue, Midwest Airlines, Northwest Airlines, United Airlines, and US Airways. Two additional airlines, Delta Airlines and Southwest Airlines, are currently negotiating separate agreements with EPA. Collectively, these 14 carriers represent the majority of U.S. flag carrying aircraft transporting the flying public. The agency will continue to work with smaller, regional, and charter aircraft carriers to address drinking water quality with agreements similar to those reached with Air Transport Association (ATA) members. These agreements will govern airline drinking water safety until additional regulations are completed.
EPA began a review of existing safe drinking water guidance to airlines in 2002. In response to the aircraft test results, EPA is conducting a priority review of existing regulations and guidance. The agency is placing specific emphasis on preventive measures, adequate monitoring, and sound maintenance practices such as flushing and disinfection of aircraft water systems.
For more information on the regulation of water supplies aboard passenger aircraft and to view publicly available testing data, visit www.epa.gov/airlinewater.
This news item originally appeared in the March/April 2005 issue Water and Wastewater Products, Vol. 5, No. 2.
This article originally appeared in the 03/01/2005 issue of Environmental Protection.