• EPA Air Model Underestimates Cancer Risk
  
• NRC Eyes Possible Restart of Davis-Besse Reactor
  
• Court Upholds New Los Angeles Stormwater Controls
  
• Ecologists Urge Study of Transgenic Organisms' Impact
  
• Jetting Toward Climate Change
  
• Saharan Groundwater More Than a Million Years Old
  
• Climate Change Could Release Old Arctic Carbon
  
• A New View of New Jersey's Ice Sheets
  

EPA Air Model Underestimates Cancer Risk

The researchers found that cancer risk figures based on actual measured exposure for communities in Baltimore, Maryland were as much as three times greater than estimates given by models.

The study is the first of its kind to directly compare the U.S. Environmental Protection Agency's (EPA) Assessment System for Population Exposure Nationwide (ASPEN) model results to indoor, outdoor and personal exposure measurements.

ASPEN is being used nationally to assess the public health impact of ambient air toxins.

"The public health implications of our findings loom large," said Dr. Timothy Buckley, the senior author of the study and an associate professor in the School's Department of Environmental Health Sciences. "ASPEN has already shown that for many U.S. census tracts, risk from ambient air toxins exceeds acceptable levels. Now our data indicates that because of significant indoor source contributions, these risks are much worse."

The study, "Personal Exposure Meets Risk Assessment: A Comparison of Measured and Modeled Exposures and Risks in an Urban Community" is published in the April 2004 issue of the journal "Environmental Health Perspectives."

The researchers used passive air sampling badges to compare personal, outdoor and indoor residential concentrations of VOCs for 33 nonsmoking, adult study participants to ASPEN ambient estimates.

For VOCs that have significant indoor sources, such as chloroform, the researchers found that ASPEN far underestimated the measured personal exposures.

In contrast, VOCs from vehicles, such as benzene, or VOCs such as carbon tetrachloride that occur at global background levels, the ambient estimate given by ASPEN was in agreement with the measured personal exposures.

When the researchers combined all the VOCs into an assessment of risk, they found that ASPEN underestimated risk based on actual measured exposure by a factor of three.

"Our results indicated that South Baltimore residents were routinely exposed to a number of VOCs that are considered to be toxic air pollutants by the EPA and at levels above public health benchmarks," said Dr. Devon Payne-Sturges, the study's lead author. "Benzene, carbon tetrachloride and chloroform accounted for most of the risk."

The indoor environment continues to represent an important source of personal exposures to VOCs, Payne-Sturges said.

"The good news is that indoor sources can be controlled," she said. "Environmental tobacco smoke is the greatest culprit but other more subtle contributors, such as cleaning solvents and air fresheners, add up to represent a sizeable fraction of the risk. We need to do a better job of getting the word out about the importance of indoor sources and the means for their control."

But some populations might have more difficulty in changing these aspects of their life, Payne-Sturges acknowledged, in particular people who depend on jobs where limits on smoking indoors are not enforced or people who have limited access to "green product alternatives" for home use.

Buckley added that the findings "demonstrate the significance of indoor exposure sources and the importance of indoor and personal monitoring for the accurate assessment of a community's risk."

"The EPA is clearly on the right track in its development of models that will take into account indoor sources providing a true representation of the health risk from VOCs air toxin exposure," he said.

NRC Eyes Possible Restart of Davis-Besse Reactor

Court Upholds New Los Angeles Stormwater Controls

The County of Los Angeles, along with a coalition of cities and building groups, filed the lawsuits against the State Water Resources Control Board in an attempt to invalidate new requirements to control urban runoff, which is Southern California's top source of beach pollution.

Superior Court Judge Victoria Gerrard Chaney dismissed all claims against the State Water Resources Control Board and rejected plaintiffs' attempts to introduce irrelevant evidence and allegations that the water board lacked authority to issue the permit.

The motions granted by the judge were filed by the Natural Resources Defense Council (NRDC), BayKeeper, and Heal the Bay.

"Developers and their allies in local government have launched a full scale attack on reasonable efforts to reduce the number one source of water pollution in California," said NRDC senior attorney David Beckman, lead counsel for the environmental groups. "The ruling is a step toward clean water."

The stormwater permit, issued in 2001 under the federal Clean Water Act, requires measures such as drain filters, silt removal basins and inspections, as well as traditional measures such as public education and street sweeping.

The Los Angeles permit is one of the first in California to require actual results measured by reductions in pollution.

One of the most critical aspects of the permit is that it prohibits urban runoff from "causing or contributing to violations of water quality standards," which essentially means it is illegal for runoff to cause beach closures or discharges that are toxic to aquatic life.

A similar permit in San Diego was upheld last year and is now being appealed by the Building Industry Association.

Ecologists Urge Intensive Study of Biotech Organisms

While the ESA position paper recognizes the possible benefits GEOs may offer, it addresses several areas of concern.

The organization notes that future applications of genetic engineering extend far beyond traditional breeding, to encompass transgenic viruses, bacteria, algae, fungi, grasses, trees, insects, fish, shellfish and many other species.

"Several environmental risks associated with gene flow, the evolution of resistance, and certain non-target effects could be irreversible," said Allison Snow, lead author of the position paper and a professor at Ohio State University. "Additional research is needed to evaluate circumstances under which this could happen."

One worry involves the unintended escape of transgenic salmon into wild populations. Current findings show contradictory results of transgenic salmon's faster development and eating habits. The engineered fish might out compete the natural populations, or their traits "could increase their susceptibility to predation and stressful environments," according to the paper.

"Understanding how genetic engineering will affect organisms living and dispersing outdoors is a major challenge," said ESA President William Schlesinger. "This position paper provides insight into the ecological questions that should be considered before genetically engineered organisms are released, as well as important recommendations for monitoring and evaluating GEOs once they are in the field."

The major recommendations in the paper include:

• Rigorous, interdisciplinary scientific studies are needed to evaluate environmental benefits and risks posed by GEOs;

• Designing GEOs to reduce environmental risks by incorporating specific genetic features, such as traits that limit unwanted gene flow between GE organisms and non-GE organisms;

• Large scale or commercial release of GEOs should be prevented if scientific knowledge about possible risks is inadequate or suggests the potential for serious negative effects on ecosystems;

• Well designed monitoring will be crucial to identify, manage, and mitigate environmental risks when there are reasons to suspect possible problems;

• Science based regulation should subject all transgenic organisms to a similar risk-assessment framework, recognize that many environmental risks are specific to the GEO and location, and incorporate a cautious approach to environmental risk analysis;

• Ecologists, agricultural scientists, molecular biologists and others need broader training and integrated communication to better address these issues.

"Another concern is that GEOs will interbreed with native populations once released," Snow said. "It is important to understand how an influx of transgenes can affect local populations, such as weedy relatives of crop plants. Also, new types of engineered microbes, insects, fish and horticultural plants are likely to require more ecological study than most domesticated food crops."

Jetting Toward Climate Change

The study by Dr. Katta Murty cautions that major increases in commercial flights and expansions of airports would not only add to greenhouse gas emissions, but could further harm the protective ozone layer that surrounds the Earth.

Current industry projections predict the world's air transportation industry could triple within two decades.

"It is an important problem to analyze at what altitudes additional releases of greenhouse gases will have maximum impact on global warming," according to Murty.

"This study also points out that the much more rapid melting of polar ice near the North Pole compared to that at the South Pole," she said, "may have been caused by the very large fraction of jet air flights in the world occurring over the northern polar region."

Murty says jet aircraft atmospheric damage is unique in that exhaust emissions from such aircraft are deposited not only in the lower atmosphere but also in the cloud forming troposphere and higher, where resulting contrails are formed and other chemicals remain to interact for decades.

According to Dr. David Travis, professor and chair, Department of Geography and Geology, University of Wisconsin-Whitewater, research "has demonstrated that jet contrails have caused substantial increases in the high cloud coverage over the most heavily trafficked regions of the United States and Europe."

Travis says these increases in high clouds have led to suppression of the temperature range causing both daytime cooling and nighttime warming in areas where contrails are most abundant.

"During the three days following September 11th - when no commercial aircraft were flying - the skies across the United States were remarkably clear with a much wider range in temperature between day and night, giving an indication of how the U.S. climate used to be prior to the days of aviation," Travis said.

The findings of these researchers - along with the recently publicized study by consultants to the U.S. military warning of the environmental, social and political impacts of climate change - are more evidence the United States needs to rethink its transportation system, says Jack Saporito of the Alliance of Alliance of Residents Concerning O'Hare (AReCO).

"Now, more than ever, there is support and urgency to demand a U.S. moratorium on all airport expansion projects currently in the works," Saporito said. "Furthermore, there is a real need for environmental impact reviews to be taken seriously and results stringently enforced."

Saharan Groundwater More Than a Million Years Old

Evidence of the Sahara's green past lies hidden beneath the sands of Egypt and Libya, in the form of a huge aquifer of fresh groundwater, and researchers have discovered that this groundwater has been flowing slowly northward for the past million years.

This revelation by an international team of geologists and physicists has been accepted for March publication in "Geophysical Research Letters," published by the American Geophysical Union.

The discovery rests on analysis of an extremely rare radioactive isotope, which is produced by cosmic rays in the atmosphere.

The isotope, krypton-81, has been noted as an ideal groundwater chronometer on the million year time scale, but it has been nearly impossible to measure because of its low abundance.

There is only one atom of krypton-81 in a trillion atoms of atmospheric krypton, a rare gas to begin with, and krypton is absorbed only slightly by water.

But recently, scientists at Argonne National Laboratory have developed a method to count individual atoms of krypton-81 and measure its abundance accurately with the use of laser technology.

Known as ATTA, for Atom-Trap Trace Analysis, this new, ultrasensitive method could revolutionize the scientific study of such topics as continental groundwater flow, long term glacier motion, and seawater circulation through the ocean floor, say the researchers.

The research team applied this method to a groundwater investigation in the Western Desert of Egypt, where they sampled krypton from the Nubian Aquifer groundwater, which was reputedly old but of unknown age.

To obtain a sufficient amount of krypton for the ATTA measurements, the team had to extract dissolved gases from thousands of liters of groundwater in the field, using a device invented by the Swiss members of the team.

The gas extracted from each well was compressed into steel containers and shipped to a lab in Germany, where the trace amount of krypton in each sample was purified and delivered to Argonne for analysis of krypton-81.

ATTA measured the ratios of krypton-81 to ordinary krypton, which ranged from about five to 53 percent of that in the air, corresponding to groundwater ages of 200,000 to 1,000,000 years.

The research team explains that based on these data, it is possible to estimate the direction and velocity of the groundwater flow, which is between one and two meters per year toward the north, and to determine the recharge location in southwest Egypt.

Isotopic characteristics of the water itself indicate that it was transported by air masses traveling long distances over North Africa from the Atlantic Ocean, thus reflecting climate conditions during the past million years much different from the present climate.

Climate Change Could Release Old Arctic Carbon

Previously scientists had not known the age of the carbon that reaches the ocean, uncertain if it was recently derived from contemporary plant material or if had been locked in soils for hundreds or thousands of years and therefore not part of Earth's recent carbon cycle.

But a team of scientists from the United States and Germany has now used carbon-14 data to determine the approximate age of dissolved organic carbon in the Arctic for the first time.

In an article to be published this month in "Geophysical Research Letters," the scientists report that most of the carbon that reaches the ocean is relatively young at present, but that this could change.

Warming of the Arctic, which has been documented in recent years, could affect northern peats, collectively one of the largest reservoirs of organic carbon on Earth. As the soils rich in carbon warm, the carbon is more susceptible to being transported to the ocean by rivers small and large, they say.

The researchers, headed by Ronald Benner of the University of South Carolina, studied four rivers in northern Russia and in Alaska, along with the Arctic Ocean itself. The scientists concentrated their study in periods of peak river discharge.

River water tends to remain near the surface of the Arctic Ocean for five to 15 years. This means the land derived dissolved organic carbon from all sources and years is mixed.

Various samples gave radiocarbon average ages varying from 680 to 3,770 years, including both carbon from land derived and marine sources.

The researchers conducted analysis to determine the portion of a particular sample that had originated on land by identifying a compound that is related only to terrestrial plant material.

Key to the study is the East Greenland Current, which is the major source of both Arctic Ocean water and its dissolved organic carbon component reaching the North Atlantic Ocean.

The study concludes that the land-derived dissolved organic carbon reaching the Atlantic via this current is much younger than the marine component.

The research team reported that up to half of it reaches the Atlantic, some three million to 13 million tons.

The fate of the young land-derived dissolved organic carbon in the Atlantic Ocean is uncertain, but there is no evidence of this material at lower latitudes in the Atlantic, the researchers say.

"This suggests most of the land-derived organic carbon ends up being oxidized to carbon dioxide and thus eventually cycles back into the atmosphere," says Benner. "If current warming trends in the Arctic continue, we can expect to see more of the old carbon now sequestered in northern soils enter the carbon cycle as carbon dioxide. This will act as a positive feedback, tending to enhance the greenhouse effect and accelerate global warming."

A New View of New Jersey's Ice Sheets

The researchers found that during the Late Cretaceous greenhouse world, some 99 to 65 million years ago, sea level changes were large, more than 25 meters (82 feet), and rapid, occurring on scales of less than one million years.

The researchers maintain that either ice sheets grew and decayed in that greenhouse world or our understanding of sea level mechanisms is fundamentally flawed.

To date, analyses indicate minimal tectonic effects on the New Jersey Coastal Plain at this time, the scientists say.

They assert the other explanation for such large, rapid changes is the waxing and waning of large continental ice sheets, but are puzzled that such large and rapid sea level changes occurred during an interval thought to be ice free.

"Our studies of cores in New Jersey provide one of the best dated estimates of how fast and how much sea level changed during the greenhouse world of the Late Cretaceous," said study leader Kenneth Miller of Rutgers University.

"The Earth was certainly much warmer at that time, probably due to high carbon dioxide levels in the atmosphere," Miller said. "At the same time, our estimates require that ice sheets grew and decayed on Antarctica during this period of peak warmth, which has been a previously heretical view."

Miller and his team propose that the ice sheets were restricted in area to Antarctica and were temporary. They believe the ice sheets would not have reached the Antarctic coast, explaining the relative warmth in Antarctica, but still could significantly alter global sea level.

Miller and his colleagues aim to publish their results in the March-April issue of the "Geological Society of America Bulletin." The work is part of an onshore extension of the National Science Foundation's ocean drilling program.