NEWS OF THE WEEK
DOUBTING EPA ON FORMALDEHYDE RISK: Science panel says agency failed to support chemical’s link to leukemia, other health problems Nearly twothirds of the formaldehyde market is for resins to make construction materials such as plywood.
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N INDEPENDENT PANEL of scientific experts
SHUTTERSTO CK
is questioning the Environmental Protection Agency’s conclusion that formaldehyde causes respiratory cancers, leukemia, and several other health problems, including asthma. EPA preliminarily concluded last June that formaldehyde can cause cancer in humans when it is inhaled. But in a review of the agency’s findings, a committee of the National Academies’ National Research Council (NRC) says some of EPA’s conclusions about the potential health effects of the widely used industrial chemical go beyond available scientific evidence. The NRC analysis finds that the evi-
CHLORINATION IMPROVES ORGANIC ELECTRONICS
A prototype light-emitting diode made with chlorinated indium tin oxide glows green. COURTESY OF ZH ENGHONG LU/U OF TORONTO
MATERIALS: Treatment could simplify
manufacturing, reduce costs
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HLORINATING A COMMON electrode mate-
rial for organic light-emitting diodes (OLEDs) could make devices easier and less expensive to manufacture, researchers report (Science, DOI: 10.1126/ science.1202992). In a typical OLED, electrons move from an organic, light-emitting material to indium tin oxide. But the energy of the electrons removed from the light-emitting material is higher than the oxide can accept. Consequently, layers of other materials—for example, copper phthalocyanine—are used to bridge the gap and facilitate electron flow. The additional layers, however, add cost and complexity to manufacturing and reduce the electrical efficiency of electronic devices. In an effort to do without those extra layers, a reWWW.CEN-ONLINE.ORG
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dence is sufficient for EPA to conclude that formaldehyde causes cancer of the nose, nasal cavity, and upper throat. But the report asserts that EPA failed to support its determination that the chemical causes cancer in other sites in the respiratory tract or leukemia. “EPA should revisit its arguments and include detailed descriptions of the criteria that were used to weigh evidence and assess causality,” the committee says. The report also notes that EPA’s draft assessment “provides little discussion about how asthma could be caused or exacerbated by formaldehyde exposure.” EPA has been working since 1998 to update its formaldehyde toxicity assessment. The agency’s previous evaluation, completed in 1989, found the substance to be a “probable” human carcinogen. The chemical industry has been fighting efforts to classify formaldehyde as a known carcinogen, a designation that could lead to more stringent regulation. NRC weighed in on EPA’s latest findings after Sen. David Vitter (R-La.), an industry ally, put pressure on EPA to request an independent study. In 2009, Vitter blocked the confirmation of Yale University chemist Paul T. Anastas to head EPA’s R&D office until the agency agreed to seek the NRC review. EPA says it is examining NRC’s recommendations. “EPA conducts peer review to ensure only the highest quality science is used as the basis of our actions. Strong science depends on peer review and the robust discussion among scientists represents a strong scientific process,” the agency says in a statement.—GLENN HESS
search group led by materials science and engineering graduate students Michael G. Helander and Zhibin Wang and professor Zhenghong Lu at the University of Toronto chlorinated the electrodes by exposing the material to o-dichlorobenzene and ultraviolet light. The treatment causes chlorine radicals from the solvent to displace oxygen and bind to indium on the electrode surface. The resulting layer of polar In–Cl bonds increases the electrostatic potential just above the electrode’s surface. That change in potential increases the electron energy that the electrode can accept and closes the energy gap between the electrode and light-emitting materials, such as a phosphorescent iridium complex doped into 4,4´-N,N´-dicarbazole biphenyl. Electrons can then directly transfer between the light-emitting layer and the chlorinated electrode, making electronic devices easier to manufacture and more efficient to operate. The prototype devices made by the Toronto group show a substantial improvement in operating voltages and efficiency, says Franky So, a materials science and engineering professor at the University of Florida. “This approach might lead to a paradigm shift in OLED technology.”—JYLLIAN KEMSLEY
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