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mutant colonies. This dramatic increase of meth independent mutations with increasing concentrations of the chemical shows that bleomycin has a strong mutagenic effect in A. nidulans.

Alink, G.M., J. Smit, E. Theune and J.S.M. Boleij, Department of Toxicology and Department of Air Pollution, Agricultural University, Wageningen (The Netherlands)

Mutagenic activity of airborne particulates at non-industrial locations

Various studies indicate that aerosols which can be collected in the ambient atmosphere may have mutagenic properties. The present study was started in order to analyze the mutagenicity of aerosols at non-industrial locations over a prolonged period of time. To study background mutagenesis high-volume sam- ples of air particulates have been taken each 4th day at a "background" and a rural location over periods of 4 and 12 months resp. Each sample was collected on a glass filter over a 24-h period. The filters were extracted in a Soxhlet apparatus for 8 h in 350 ml of methanol. After evaporation to dryness the res- idue was taken up in DMSO. Mutagenic analysis was performed with the Sal- monella/microsome test, using tester strains TA98 and TA100, with and with- out the addition of Aroclor-activated liver homogenate, and with the sister- chromatid exchange (SCE) test, using V79 Chinese hamster cells. Bacterial strain TA98 appeared to be more sensitive than TA100 in the detection of mutagenic activity in airborne particles. In general the addition of a metabolic system did not increase mutagenicity which varied within 4 months between 0 and 30 His+ revertants per m 3 air. At both locations mutagenicity was depen- dent on the wind direction. The relationship with other meteorological factors and with parameters of environmental pollution was studied. Several air sam- ples which were positive in the Ames test also appeared to be positive in the SCE test.

Schfirer, C.-C. a, N. Manojlovic and N.H. Seemayer, a Medizinische Klinik A and Medizinisches Institut fiir Umwelthygiene der Universit~it Diisseldorf (F.R.G.)

Induction of "sister-chtomatid exchange" by city smog extracts and their fractions in cultured human lymphocytes

Epidemiological investigations indicate a higher incidence of lung cancer in industrialized areas which could be related to higher burden by air pollutants. City smog contains a large number of biologically active substances, e.g. car- cinogenic polycyclic aromatic hydrocarbons or acridines. We analyzed the mu: tagenic effect of city smog extract and its fractions from the heavy industrial- ized Rhine--Ruhr area in West Germany by induction of sister-chromatid exchange in cell cultures of phytohemagglutinine-stimulated human lympho- cytes. We found a highly significant dose<lependent induction of sister-chroma- tid exchange after 72 h of exposure to city smog total extract and the follow-