News of the Week
Computer Secretariat makes debut A new ACS entity, the Computer Secretariat, made its debut on the program at the Miami Beach meeting. Such a body might seem superfluous in a society that already boasts a Division of Computers in Chemistry. But in fact, according to Rudolph J. Marcus, who has been instrumental in organizing the secretariat, chemists in several other ACS divisions are involved with computers in one way or another. In the past, that dispersion has led to some confusion and conflict in scheduling computer-related sessions at national meetings. As Marcus (a California-based consultant on computers in chemistry research) puts it, "We hope to eliminate a lot of unnecessary running around." Marcus explains that the newly formed secretariat will coordinate planning and programing of computeroriented activities for five ACS divisions: Analytical Chemistry, Chemical Education, Chemical Information, Com-
ter Inc., Des Plaines, 111., and former chairman of the ACS Board; and W. Lincoln Hawkins, a technical consultant in materials engineering and retired assistant research director from Bell AT&T Laboratories in Murray Hill, N.J. D
puters in Chemistry, and Physical Chemistry. A sixth division, Industrial & Engineering Chemistry, has indicated that it will join in future secretariat activities, Marcus adds. The wide-ranging presentations at the secretariat's inaugural symposium made it obvious that "computer" means different things to different chemists. For some, its prime virtue is its "number-crunching" power. For others, its attraction may lie instead in its ability to manipulate graphic representations of molecules, to control laboratory instruments, or to serve as a patient tutor to undergraduate chemistry students. Indeed, Marcus says, an important function of the secretariat will be to bring together the practitioners of the various subspecialties of computer chemistry, to provide some cross fertilization. In addition, it will be a vehicle for disseminating news of new computer hardware and software developments.
says, has been obscured by the diversity of degradation pathways and by technical limitations in the gas chromatographic analytical methodology available. But, he says, "Biodegradation has undoubtedly been taking place all along." The GE research focused on a portion of the upper Hudson River FROM MIAMI BEACH known to have received substantial discharges of PCBs from 1952 to 1973. Used as insulating fluids in electrical equipment, PCBs were banned in 1979 because they were carcinogenic in laboratory animal Polychlorinated biphenyls (PCBs) tests. GE scientists have studied more may not be as indestructible in the than 200 samples from sediment environment as thought. On the oth- cores using high-resolution capiler hand, poly cyclic aromatic hydro- lary GC. carbons (PAHs) may have an adBoth aerobic and anaerobic bacteverse effect on the environment that ria in the river sediment are dehas largely gone unrecognized. grading the PCBs, each by its own These are the implications of two distinctive pathway, the GE renew studies involving the substances. searchers found. "Unexpectedly, A team of scientists headed by much more massive transformation John F. Brown Jr., manager of health was found for the PCBs contained research at General Electric's Re- in the deeper sediment layers," search & Development Center, Sche- Brown says. nectady, N.Y., has found PCBs to be In more contaminated, deeper undergoing extensive biodégrada- layers, containing anaerobic bactetion in nature. ria, transformation is taking place Recognition of the process, Brown through reductive dechlorination.
New findings on PCBs, other pollutant group
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May 6, 1985 C&EN
The net effect, Brown says, is to make the PCBs more biodegradable. The phototoxicity of PAHs is a property that has more or less been ignored for larger organisms, according to Jacques Kagan, professor of chemistry at the University of Illinois, Chicago. Although some work has been done with microorganisms, he explains, much of the attention of biologists has been focused on the carcinogenic and mutagenic properties of PAHs—benzo[a]pyrene, for example. Kagan studied primarily those PAHs that are not carcinogenic. Using very simple aquatic organismsmosquito larvae, water fleas, brine shrimp, tadpoles, and minnows—he found that "PAHs which are not carcinogenic are indeed very phototoxic and kill these organisms at very low concentrations." Phototoxic substances depend on light for their toxicity. Organisms exposed to such compounds in the dark are not affected by them, but they die when light of appropriate wavelength is also present. When some organisms are exposed to certain PAHs, introduction of UV light leads to death with LC50s—the concentration at which 50% died—as low as a few parts per billion. The mechanism of phototoxicity for the PAHs isn't known, Kagan says. But he thinks that damage of cellular membranes, perhaps through singlet-oxygen mediated lipid peroxidation, would be a reasonable path. PAHs studied by Kagan included naphthalene, fluorene, anthracene, 9-methylanthracene, phenanthrene, chrysene, fluoranthene, and pyrene. Fluoranthene and pyrene, Kagan points out, are among the most abundant pollutants found in air and water samples. They were also the most phototoxic to the organisms tested. PAHs are formed by combustion of organic materials, Kagan points out. They accompany the acidic components, which have received the public's attention because of their acid rain effects. Kagan thinks that more attention should be given the PAHs so that the effects on the environment of the acidic pollutants and those of the PAHs can be sorted out clearly. D
