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When the solution of DNA stained with intercalating dye is applied to the vertical channel, only one DNA molecule at a time emerges at the narrow tip. An optical system focused at this area excites the molecule as it comes out and measures its fluorescence emission. "We can measure the size on thefly,as the molecule is flowing by," Quake says. "That lets you decide what to do with the molecule before it hits the T-junction. You can sort the molecule, if it meets some criteria, by changing the fluid flow to push the molecule to either the right or the left horizontal channel." Quake says the ultimate goal is to apply the device to so-called cascaded DNA digestion, a process used in mapping genomes. Long pieces of DNA are cut with restriction enzymes, the fragments are sized and sorted, and the interesting ones are redigested with a different enzyme. With gels, the procedure is painstaking. "We'd like to do [cascade digestion] all in one shot, on a chip, in a matter of minutes," says Quake. That means the digesters, sizers, and sorters are all in a chip. "That's the real power of microfabrication." The technology is not limited to single DNA molecules. Working with the group of Caltech chemical engineering professor Frances H. Arnold, Quake's team already has adapted it to microfabricate devices for rapid screening and sorting of bacterial cells. Arnold's research in molecular evolution requires the ability to quickly interrogate hundreds of thousands, even millions, of cells that express molecules of interest. Maureen Rouhi
Formosa Plastics claims mercury waste shipped to Cambodia is harmless Two governments—Cambodia and Taiwan—say that Formosa Plastics acted illegally by sending 3,000 metric tons of toxic mercury wastes from Taiwan to Cambodia for disposal in December. The company denies any wrongdoing. According to international newswire reports, soon after the waste reached Sihanoukville, one Cambodian dockworker died from exposure to the material and four more perished in traffic accidents as thousands fled the Cambodian capital in panic. C. T. Lee, president of Formosa Plastics, tells C&EN that the waste is harmless. The 6 JANUARY 11, 1999 C&EN
company maintains that a caustic soda plant it operated in Renwu Kaohsiung County, Taiwan, for decades generated mercury-containing waste until 1989. However, in 1993, the company began to stabilize the waste into something resembling concrete. The treatment, which resulted in material containing nontoxic mercury Wearing protective clothing, Cambodian soldiers scoop sulfide, made use of mercury-containing waste into barrels. equipment bought from a U.S. firm. After it was up and run- tempers tend to flare over environmental ning, four of the U.S. firm's staff certified issues. "The appearance of poor disposal the treatment process, Lee says, adding practices is almost as bad as the signifithat the process is approved by both the cance of the problem itself," says Bruce F. U.S. and Taiwanese Environmental Pro- Berkman, who as managing director of Taipei-based environmental consultancy Protection Agencies. Lee explains that in 1993 Formosa ductivity Asia has worked toward implehad government approval to dispose of menting Responsible Care on the island. Jean-Frangois Tremblay the waste at a landfill at Dashi, Taiwan. But local residents objected. As a result, Formosa contracted with a Cambodian company for disposal of the 3,000 metric tons of waste. Taiwan's EPA says that Formosa failed to obtain an appropriate export license beforehand. Moreover, the agency notes The Nevada Supreme Court has affirmed that last fall it rejected a Formosa request Dow Chemical was negligent in testing to export 5,000 metric tons of untreated liquid silicone used in breast implants manufactured by Dow Corning, a 50/50 mercury waste to Cambodia. Wearing protective clothing, the Cam- joint venture between Dow Chemical bodian army has temporarily stored the and glassmaker Corning. Though Dow Chemical never manufacwaste in barrels. Lee points out that when Formosa employees went to Cam- tured breast implants, the court let stand bodia to look at the waste, they did not an October 1995 Reno, Nev., $4.1 million bring along any protective clothes. How- jury award to Charlotte Mahlum, a 41-yearever, in compliance with Cambodian de- old Nevada woman, for autoimmune illmands, Formosa Group Chairman Wang nesses allegedly suffered as a result of her Yung-ching has apologized for the inci- ruptured breast implants. A majority of the five justices also dedent, and Formosa will ship the waste to nied Dow Chemical's request for a new another country, Lee says. Taiwan's EPA has analyzed one sam- trial, but they did reverse a $10 million ple of the waste brought back from Cam- punitive damages award because "the bodia by the environmental group For- verdict in this case cannot stand as to the mosa Green Front. The agency found fraud and accessory liability claims." A Dow Chemical spokesman says the that the sample contained 0.284 ppm of mercury, in excess of Taiwanese stan- company "will file a motion for reconsiddards of 0.2 ppm. Taiwan's EPA con- eration as soon as is practical." The Mahlum case was the first against Dow Chemcludes Formosa broke the law. Lee rejects the assertion. He points ical to go to trial. About 14,000 other casout that the sample brought back by es against the company are pending and Green Front lacks a certified chain of have been consolidated with cases against Dow Corning. custody. Mahlum's attorney, Frederic L. Ellis of Even if blameless, Formosa's image has been tarnished by the incident. In Taiwan, Ellis & Rapacki, Boston, says, "This is a
Dow Chemical waylaid by implants
