News Briefs
very unstable or highly reactive. Buseck says he found other types of particles in the smoke plumes but could only characterize the tar balls. But if other carbonaceous materials are discovered, they might help further refine climate models. Soot’s quality of reflecting radiation helps to counteract greenhouse gases. “We’re not sure about tar balls,” says Buseck. “If they’re an important part of the atmosphere, then that has potentially important implications for climate modeling.” Tar balls may also be an indicator of biomass burning. Sampling smoke plumes was part of a larger NASA project called Safari 2000, an endeavor to study emissions in southern Africa. Biomass fires sometimes start from lightning. However, an estimated 90% are caused by slash and burn agriculture, which studies have shown has risen dramatically in the past 100 years and affects the global climate. —PAUL D. THACKER
Coastal monitoring tools Monitoring related to restoration of U.S. coastal habitats is complicated by the broad diversity and geographic scope of the nation’s coasts. A new manual from the National Oceanic and Atmospheric Administration consolidates the sciencebased tools needed by coastal managers, researchers, and citizens to develop the strategies best suited to a habitat’s features. The manual includes consistent principles and approaches likely to be used in a wide range of coastal efforts. It also provides an introduction to restoration monitoring related to specific habitats, including oyster reefs, water columns, and mangrove swamps. Science-Based Restoration Monitoring of Coastal Habitats, Volume One: A Framework for Monitoring Plans Under the Estuaries and Clean Waters Act of 2000 is available at http://coastalscience.noaa. gov/ecosystems/estuaries/ restoration_monitoring.html.
After a number of fits and starts, the California EPA has finally set the first public health goal in the nation of 6 parts per billion (ppb) for perchlorate in drinking water. However, the state said that it reserves the right to modify this level if the ongoing National Academy of Sciences perchlorate health review produces a significantly different evaluation of this key rocket fuel ingredient when it issues its findings later this year (Environ. Sci. Technol. 2003, 37, 166A–167A). California has been developing a perchlorate health goal since 1998. In 2002, the state proposed 6 ppb. However, a lawsuit by Lockheed Martin and Kerr McGee mandated a second round of peer review by University of California scientists, and a deadline of March 12, 2004, was set. Before that round of review, the draft goal was revised to a range of 2–6 ppb. The public health goal is based purely on a health-risk assessment, but next year the state’s Department of Health Services
PHOTODISC
California sets public health goal for perchlorate
Perchlorate, which is used in rocket fuel and other applications, has been found in the drinking water of many U.S. states, but California has become the first to set a public health goal for the compound.
Seeing Energy Stars The Whirlpool Corp. (Ben Harbor, Mich.) received one of this year’s 57 Energy Star Awards for selling the most Energy Star-certified appliances in 2003. The company offers 352 certified base models, actively promotes saving energy in its advertising, and helps make homes more energy efficient in cooperation with Habitat for Humanity. The U.S. EPA annually recognizes outstanding contributions to reducing greenhouse gas emissions through energy-efficient innovation. Energy Star now has more than 8000 partners. Last year, the program helped Americans save $9 billion and enough energy to power 20 million homes and reduced greenhouse gas emissions by the equivalent output of 18 million cars. For a complete list of award winners, go to www.energystar.gov.
MAY 15, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY ■ 177A
NOAA
Stephen Schwartz, a Senior Scientist at Brookhaven National Lab, says that large amounts of oxygen in tar balls means the particles are more hydrophilic and may have interesting chemical properties. “[Tar balls] may be more susceptible to being incorporated into precipitation,” he says. “It also means that if you inhale them, they are more likely to dissolve in cellular fluids. So there’s a lot we need to learn about these things from an air quality perspective, human health, and climate influence perspective.” Tar balls were found to be very abundant in smoke plumes barely minutes to hours old. And in hourold smoke, they were the dominant particle type. Although it is not entirely understood how they materialize, their rapid appearance in smoke indicates they form by a gasto-particle conversion. And judging from the tar balls’ insignificant presence in atmosphere, their structure is thought to be either
Environmental▼News must apply economic and technical considerations to set a water standard as close to 6 ppb as possible. California’s final health goal is higher than the U.S. EPA’s most recent draft recommendation of 1 ppb, which has prompted environmental groups to say that the goal is too high. The value was designed to protect fetuses and infants, but “the goal does not account for the huge water consumption of bottle-fed babies nor the fact that perchlorate can get into mothers’ milk,” says Gina Solomon of the National Resources Defense Council. However, James Stock, former secretary of the California EPA and a spokesperson for several industry groups, says, “Credible human research suggests, along with other studies, that it is unlikely that perchlorate at low levels poses
risks of adverse health effects in the general population or in sensitive subpopulations.” Joan Denton, California’s chief hazard assessment officer, says the science behind the goal is sound. It was “rigorously reviewed before it was finalized,” she says. Reviews included two separate rounds of peer review by University of California scientists and one by the U.S. EPA. For the risk assessment, the California EPA’s health hazard assessment branch decided that the most sensitive endpoint is perchlorate’s potential anti-thyroid effects on fetal brain development, which arise because the compound inhibits uptake of essential iodine. A 2002 human dosing study (Environ. Sci. Technol. 2002, 36, 407A ) was used to estimate the perchlorate
dose at which iodine uptake is reduced by 5%. Such a reduction was deemed to be a conservative estimate of a change that would not cause harm. Perchlorate has been found in lettuce, cucumbers, strawberries, dairy milk, and breast milk, so the health agency estimated that drinking water accounts for 60% of total exposure and added an uncertainty factor of 10 to account for differences among people. The health goal technical document also notes that other environmental contaminants—most importantly nitrate—have a thyroid effect similar to perchlorate. The technical document leaves open the possibility that such effects will be incorporated into the California EPA’s nitrate reevaluation. —REBECCA RENNER
Huge chromium plume threatens Colorado River used chromium VI to control corrosion and mold in water-cooling towers at an isolated natural gas compressor station south of the town of Needles, which is on California’s border with Arizona. PG&E dumped untreated wastewater into nearby percolation beds between 1951 and 1969. PG&E began pumping on March 8, after the Metropolitan Water District of Southern California put pressure on the state Department of Toxic Substances Control (DTSC) to take action. The chemical, made famous by the 2000 movie Erin Brockovich, is “on the brink of contaminating the Colorado River,” the water company declared in a letter PHOTODISC
To halt the advance of a massive plume of chromium VI-contaminated groundwater that threatens a major source of water for 18 million people, California utility Pacific Gas and Electric (PG&E) has begun pumping 20,000 gallons a day of contaminated water out of a remote Mojave Desert location. The plume, estimated to contain at least 108 million gallons with chromium concentrations as high as 12,000 parts per billion (ppb), has moved to within 125 feet of the Colorado River. The state’s drinking water standard is 50 ppb. The pollution began decades ago when the utility, which serves central and northern California,
Chromium used decades ago to control corrosion at a natural gas plant now threatens the Colorado River, which supplies drinking water to southern California. 178A ■ ENVIRONMENTAL SCIENCE & TECHNOLOGY / MAY 15, 2004
to state regulators. Currently, the contaminated water is being trucked more than 200 miles to treatment facilities in California and Arizona, according to DTSC spokesperson Ron Baker. Meanwhile, a group that includes representatives of federal, state, and local agencies is considering several long-term solutions, such as further pumping, in situ treatment, a physical barrier, or all three. The water company favors construction of a permanent slurry wall parallel to the banks of the river, which would be approximately 2000 feet long, 120 feet deep, and 5 feet wide. Such a structure would be like an 8–10-story building wall sunk into the ground, says Baker. Alternatively, the wall could be an iron-permeable reactive barrier that would reduce chromium VI to nontoxic chromium III and sequester it. Such a structure would cost about $10 million. Because the pristine area is part of a Department of Interior wildlife preserve, Baker says it could take up to two years to evaluate the environmental impact of such a structure. DTSC estimates that the plume is moving at about one foot per year, but not all parties agree on this estimate. —REBECCA RENNER
