310 monosomies 20%, polyploidies 25%) did not differ from similar series originating from other ethnic groups. The annual variation in CA frequency was significant for trisomies alone and anomalies to- gether: their frequency dropped in 1985 and rose significantly in 1986 and 1987; the same is true for the annual development of the incidence of SA in the population of Bratislava. It may be supposed that the frequency of autosomal trisomies was mainly determined by changes in the incidence of chromosome anomalies, and even the incidence of SA as a whole. 100 Dobifi~, L., L. Jan~a, I. Lochman and A. Loch- manova, Regional Hygiene Station, Ostrava (Czechoslovakia) Genotoxic action of formaldehyde in exposed children The frequency of chromosome aberrations, humoral and other factors of immunity in relation to exposure was analysed in formaldehyde-ex- posed children. An increased frequency of chro- mosome aberrations was observed from 1984 to 1985. The rate of aberrant cells found in 1984 in exposed children (N = 20) was 4.71% (+ 2.09), the break/cell ratio was 0.071 and the formaldehyde exposure level was 317.0/~g/m 3. The rate of aber- rant cells in the second sampling period (1985) was 2.82% (_+ 1.64) (N = 16), the break/cell ratio was 0.042 and the formaldehyde exposure level was 130.0 btg/m 3. A normal frequency of chromosome aberra- tions was observed in 1986, the rate of aberrant cells was 2.06% (+1.51), and the formaldehyde level was 36.5 /~g/m 3. The increased levels of aberrant cells in peripheral blood lymphocytes detected in 1984 and 1985 were significantly dif- ferent (P= 0.005) from the control frequency (1.37% + 0.87, 1.41% + 0.79). The variations found in humoral and other immunity factors detected in the group of formaldehyde-exposed children al- tered the profile of immunity. We conclude that formaldehyde exposure levels below 35.0 /~g/m 3 do not pose any serious genotoxic risk for the exposed children. 101 Dzwonkowska, A., H. Hiibner and I. Por~bska, Department of Plant Cytology and Cytochemistry, University of Lodz, and Institute of Basic Sci- ences, Medical Military Academy, Lodz (Poland) In vitro study of the influence of pesticides positive or negative in the Ames test on SCE and satellite associations The frequency of SCE and satellite associations in metaphase chromosomes of lymphocytes cul- tured in the presence of some commercial pesti- cides was studied. Dichlorvos and demeton were mutagenic in the Ames test; dimetoate and a mixture of methoxychlor and propoxur were nega- tive in the Ames test. Two doses of pesticides (dichlorvos, demeton and the mixture of metho- xychlor and propoxur, 1 and 10 #g/ml; di- metoate, 0.3 and 3 #g/ml) were added to lymphocyte cultures for 24, 48 an 72 h. It was found that only demeton in a dose of 10 /zg/ml induced a significant increase in the frequency of sister-chromatid exchanges. It was also shown that in general the frequency of satel- lite associations in the control and test cultures was higher in the first generation of cells than in the second and third generations. 102 Eggens, M., and D. Vethaak, Ministry of Trans- port and Public Works, Public Works Depart- ment, Tidal Water Division, Section Ecotoxicol- ogy, The Hague (The Netherlands) PAHs en PCBs in relation to liver turnouts in fish in The Netherlands The prevalence of hepatomas in the bottom- dwelling fish species flounder (Platichthys flesus) derived from various localities along the Dutch coast were compared with the concentrations of PCBs and PAHs in blue mussels (Mytilus edulis) and sediments as well as eutrophic factors in the water such as nitrate and orthophosphate. A cor- relation was only found between the prevalence of tumours and the concentrations of PAHs, and clearly not with PCBs and eutrophication. It was assumed that the metabolic capability to detoxify organic chemicals in affected livers could