REGULATION: New EPA policies aim to boost scientific integrity
T
WO CONTROVERSIAL Bush Administration
policies affecting assessments of chemical risks and air-quality standards have been overturned by EPA Administrator Lisa P. Jackson. Late last month, Jackson implemented a new policy designed to increase the scientific integrity of an EPA database called the Integrated Risk Information System. IRIS contains scientific judgments from EPA on the safe daily dose of more than 500 chemicals. Regulators from around the world rely on the database when making decisions that have significant financial impact, such as the degree of cleanup a polluter must undertake at a contaminated site and how much human exposure to a chemical is allowable. The Bush Administration’s IRIS policy, unveiled last year, gave federal polluters, notably the Departments of Defense and Energy, more sway over EPA’s chemical risk
ROUTE TO STABLE CARBON CHAINS NANODEVICES: Strings of carbon
atoms could be building blocks for electronic nanostructures
O
PENING UP the possibility of a new class of
materials for carbon-based electronic devices, researchers in China and Japan have created stable, one-dimensional carbon chains up to 16 atoms long (Phys. Rev. Lett. 2009, 102, 205501). Theoretical studies of such carbon atomic chains indicate that they would be nearly ideal molecular wires, with properties that would be useful for semiconductor applications. Previous efforts to create chains had yielded only very short or unstable strings, hampering experimental exploration of such materials. The new approach will spur further experimental and theoretical research aimed at developing atomic-scale electronics MORE ONLINE based on carbon materials, says Philip Kim, a physics professor at Columbia University. The research group, led by Lianmao Peng of Peking University, in China, and Kazu Suenaga, of Japan’s National Institute of Advanced Industrial Science & Technology, started with a flake of graphite. They used
assessments (C&EN, April 21, 2008, page 9). The Government Accountability Office, the investigative arm of Congress, strongly criticized the Bush Administration’s move, saying it limited the scientific credibility of EPA’s chemical assessments (C&EN, May 5, 2008, page 10). Rep. Brad Miller (D-N.C.), chairman of the House Science & Technology Subcommittee on Investigations & Oversight, praises Jackson’s move. The new policy “requires that any interagency discussion be solely about the science, and no agency can take a chemical assessment off the table. Most important, the entire process is in the open—not behind closed doors,” he says. In a second move, Jackson changed the Bush Administration’s policy for reviewing and setting healthbased air-quality standards under the Clean Air Act. The Bush Administration’s approach was to blend both scientific findings and policy considerations. Critics say this process diminished the role of agency scientists and boosted political influence in the process (C&EN, Dec. 18, 2006, page 15). Jackson’s action will require creation of a sciencebased analysis of the health effects of individual air pollutants. This will restore the role that agency scientists play in determining air-quality standards, says Sen. Thomas R. Carper (D-Del.), chairman of the Senate Environment & Public Works Subcommittee on Clean Air & Nuclear Safety.—CHERYL HOGUE
a transmission electron miTo create a croscope (TEM) to irradiate nanoribbon, punch two holes in a graphene the flake with an electron (top) and thin beam, thinning it to expose a sheet the edges until a single single layer of graphene. strand of carbon They punched two holes remains (bottom). through the layer with higher intensity radiation, forming a graphene nanoribbon between the openings. The researchers then used low-intensity radiation to pare down the edges of the ribbon, leaving only one or two atomic carbon chains to bridge the graphene monolayer. The TEM resolution was not high enough to determine whether the chains were composed of cumulene, in which all carbons are connected by double bonds, or polyyne, which has carbons connected by alternating single and triple bonds. The researchers found that the connection between the chains and the graphene was not stable, and a chain end would occasionally migrate along the edge of the graphene. Chains survived for as long as 100 seconds. When they broke, it was not in the middle. Instead, one end would detach and join its mate on the other edge of the graphene. The one-dimensional carbon chains can be regarded as an ultimate basic component for electronic devices, Suenaga says, assuming ways can be found to stabilize the structures further. He envisions being able to integrate millions of chains into a device simply by patterning a single graphene layer.—JYLLIAN KEMSLEY
WWW.CEN-ONLINE.ORG
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JUNE 1, 2009
EPA made big changes to Bush Administration policies in late May.
PHYS. REV. LETT.
CHEMICAL ASSESSMENT CHANGES
CHERY L HO GU E/C& EN
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