cal Threats to Man and the Environment" program 

 aimed at identifying, characterizing, and quantify- 

 ing contaminants produced from atmospheric pre- 

 cursors of manmade and natural origin. The fol- 

 lowing projects are examples of the significant 

 knowledge that is being gained in this area: 



• "Sources, Transformations, and Chemical 

 Nature of Atmospheric Pollutants", Glen 

 Gordon, University of Maryland. Although 

 the project is devoted mostly to the character- 

 ization of particulates emitted by pollution 

 sources, it has included a significant program 

 of homogeneous gas reaction kinetics. Funda- 

 mental rate constants have been measured for 

 a number of chemical reactions involving 

 many natural and pollutant species, as well as 

 short-lived intermediates. These include spec- 

 ies such as sulfur dioxide, nitric oxide, nitro- 

 gen dioxide, ozone, the OH and HO^ radi- 

 cals, and certain hydrocarbons. At least 18 of 

 these determinations can be attributed to 

 RANN support. The measurements have 

 played a role in the national effort to 

 understand plume chemistry, smog-chamber 

 simulations, and the chemistry of the tropos- 

 phere and the stratosphere. 



• "Study of Chemistry of Airborne Particu- 

 lates", T. Novakov, University of California, 

 Lawrence Berkeley Laboratory. This award 

 supported a study of the application of pho- 

 toelectron spectroscopy (ESCA, electron 

 spectroscopy for chemical analysis) to the 

 identification of molecular species in the sus- 

 pended particulates of polluted air. It was 

 shown that carbon (soot) particles from com- 

 bustion sources catalyze the oxidation of 

 gaseous sulfur dioxide to some form of sul- 

 fate on the carbon particle surfaces. This pre- 

 viously unrecognized chemical process is now 

 believed to contribute to the burden of hazar- 

 dous particulate sulfates in polluted air. 



The nature of the initially formed sulfate was 

 investigated by reflectance infrared spectroscopy. 

 It was determined not to be sulfuric acid, a bisul- 

 fate, metallic sulfate, or ammonium sulfate. It was 

 concluded that it exists as doubly charged sulfate 

 anions held on positively charged sites on the car- 

 bon surfaces. The discovery of the carbon-cata- 

 lyzed oxidation of sulfur dioxide suggests that the 

 control of airborne sulfate pollution may depend in 

 part on controlling carbon emissions. 



Screening tests for mutagenic chemicals. The 

 development and evaluation of new tests for car- 

 cinogenic and mutagenic chemicals are important 

 research objectives. The bacterial test systems 

 which are developed and generally accepted are 

 useful but they alone are not definitive. It is imper- 

 ative that other lines of testing be pursued, espe- 



cially in mammalian systems. Under NSF sponsor- 

 ship. Dr. T. C. Hsu at the University of Texas has 

 succeeded in showing that several widely used 

 anesthetic gases, suspected of causing cancer and 

 birth defects in operating room personnel, do in 

 fact cause chromosome damage in the mammalian 

 test system under development, although they 

 were negative in bacterial test systems. This new 

 test system showed that the number of chromo- 

 some breaks (a traditional measure of chromosome 

 damage) was not increased by these chemicals, but 

 that the chromosomes failed to separate properly 

 and thus normal cell division was halted. The 

 chemicals were assayed for mutagenic effects in 

 three different cell lines by several techniques. The 

 new technique allows the usual counting and char- 

 acterization of chromosomes to be done but also 

 allows observations of disruptions of the elaborate 

 cell division or mitotic system employed by mam- 

 malian cells. In animal cells, precise segregation of 

 chromosomes between daughter cells is impera- 

 tive; otherwise, the resultant cells will be geneti- 

 cally unbalanced. This can lead to adverse effects 

 on the whole system, e.g., mutagenicity, 

 carcinogenicity, birth defects, or death of the cell. 

 Improper segregation of chromosomes in these 

 cells can lead to aneuploidy, i.e., an abnormal 

 number of chromosomes, in the daughter cells. It 

 is known that many spontaneous abortions and 

 birth defects are associated with aneuploidy. Also, 

 many cancer tissues are aneuploid. Therefore, 

 chemicals that cause segregational errors may be 

 teratogens and carcinogens but not necessarily 

 mutagens. The chemicals that disrupt cell division 

 are referred to as "mitotic poisons." These "mi- 

 totic poisons" constitute a group of chemicals 

 (which have been neglected) with potentially seri- 

 ous effects on human health. 



Nonlinear earthquake behavior of structures. The 

 University of California, Berkeley, has been 

 supported to study the fundamental dynamic be- 

 havior of structures and structural components 

 during earthquakes, in both the linear and nonli- 

 near ranges. Such basic research was needed to 

 improve the engineering understanding of how var- 

 ious structures respond to the highly complex dy- 

 namic loadings caused by earthquake ground mo- 

 tions. As a result of such efforts, precise mecha- 

 nisms of lateral forces, and shear and moment 

 transfer between structural components and joints 

 have been established. Mathematical modelings of 

 the dynamic motion of structural systems have 

 been developed. Methods of characterizing the 

 energy absorption capability of structure during 

 various stages of the earthquake excitations have 

 been accomplished and developed. Engineers are 

 now in a better position to predict the inelastic 

 response of structures subjected to seismic inputs 



NATIONAL SCIENCE FOUNDATION 21 7 



