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6.6. Discussion of toxicological investigations
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6.6.DISCUSSION OF TOXICOLOGICAL INVESTIGATIONS K.E. Suter, Sandoz Ltd., Drug Safety Assessment, Toxicology, CH-4002 Basle, Switzerland and CH. Schlatter, /nstitute of Toxicology, Swiss Federal /nstitute of Technology and University of Zurich, CH-8603 Schwerzenbach Extracts from building ventilation filters from four locations, 0.4 to 6.8 km downwind of the fire, were investigated in three different mutagenicity tests, i.e. Ames test, V79 chromosome aberration test, and Drosophila wing spot test. Each test covered different genetic end points and represented a different biological system. In addition, extracts from the particle part of respiratory filters worn by the members of the clearing squad a few days after the fire were investigated. Mutagenicity was expressed relative to the volume of the air passed through the filters of which extracts had been prepared in order to have a basis for comparison. Investigations of filter extracts from both building ventilation filters and respiratory filters confirmed that ambient air from an industrial and/or urban area is generally mutagenic. Therefore, potential genotoxicity induced by the combustion emissions from the Schweizerhalle fire has to be seen as a superimposition on this industrial/urban background level. Investigations of building ventilation filters showed that genotoxicity varied considerably between the different locations. In the case of the Ames test, differences of up to a factor of 100 were observed. As demonstrated by all three test systems, extracts from location B, whether influenced by the fire or not, were clearly more mutagenic than those from the other locations. The local variability of genotoxicity found in this project for filter extracts from various places confirmed previous observations which had demonstrated that local combustion sources and micro-climatic conditions (Meller et al., 1983; Reali et al., 1984; Tokiwa et al., 1983) are decisive factors for the mutagenic activity of filter extracts. Besides local variability there was also a marked seasonal fluctuation of genotoxicity as shown by the control extracts taken in November 1986, shortly after the fire, and for three successive periods in March/April 1987. The variations of the mutagenic potencies observed in the Ames test for the same location were in the order of a factor of up to 17. Since the control measurements in this project were restricted to a few short periods, and did not e.g. include a typical smog situation, it can be assumed that the control data probably do not represent the whole spectrum of seasonal variability usually encountered in the Basle area. Seasonal variability of ambient air mutagenicity is well known (Alfheim et al., 1983; Alink et al., 1983; Daisey et al., 1980; Reali et al., 1984; Whong et al., 1981). It is important to note that the mutagenic activity observed in the Ames test was in the range observed for other towns, suggesting that the air quality in Basle is comparable to that of other urban areas (Tokiwa et al., 1983). In comparison to filters exposed shortly after the fire, the following fire exposed-filters showed increased activities. Ames test: location B by a factor of up to 5.3, location A by a factor of up to 2.2. Chromosome aberrations: location B by a factor of 2.1. No differences were noted in the Ames test for locations C and D and for locations A, C
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and D in the chromosome aberration test. There were also no relevant differences found in the Drosophila wing spot test for locations A and B. Extracts from locations C and D were not investigated in this test. There is little information on genotoxic activity of particulate matter resulting from accidental fires. Viau et al., 1982 Investigated extracts from forest-fire polluted air. In the Ames test forest-fire polluted air was 12-38 times more mutagenic than urban air. Similarly, 43 times more SCE's were induced in cultured human lymphocytes. in comparison to these data, increases found for the extracts from locations A and B were rather small. However, total exposure of these filters lasted 13 days, and the fire exposure lasted only 6 hrs. Thus, the mutagenic activity resulting from the fire was superimposed on, and diluted by, the background actvity. For the evaluation of mutagenic/carcinogenic effects, the total dose over a prolonged period of time rather than short-term dose increases are important. Therefore for risk assessment purposes the determination of average mutagenicity resulting from exposure over several days, as in the case of the extracts investigated in the filter project, is considered appropriate. The average mutagenicity of fire-exposed extracts, those of locations A and B included, was within the seasonal fluctuation or only slightly above it. This suggests that the fire in Schweizerhalle did not lead to a detectable increase of the mutagenic risk to which the population of Basle is normally exposed. This conclusion, derived from the results of the tests of building ventilation filters, was in principle confirmed by the investigations of respiratory mask filters. Since only the filters worn by the members of the clearing squad showed increased concentrations of organic material, investigations by means of the Ames test were restricted to these filters. Results showed that the air at the site of the fire between November 2-4, 1986 did not contain more mutagenic components than ambient air in the area of the Sandoz Ltd. plant in Basle between February 17-24, 1987. Although the situation at the site of the fire during the clearance work cannot be regarded as fully representative of the situation during the fire, it can be assumed that if potent mutagens with moderate volatility had been formed they should have still been present In the air inhaled by the clearing squad a few days after the fire. They would have been detected in extracts from respiratory filters, as were hydrocarbons, phosphorous and sulfurous compounds in the analytical Investigations. Although some uncertainties remain about the mutagenicity results because of the limited amount of extracted material available, and about the filter parameters, which could only be estimated for the respiratory filters, Ames test results Indicated that no excessive amounts of highly active mutagens were present during the fire. The lack of excessive amounts of potent mutagenic combustion products may be seen in the light of the findings of Fisher et a1.(1979) and Pani et al. (1983). They showed that after heating coal-fly ash or dust from an incinerator to over 350°C, the mutagenic activity was lost. In the initial phase of the Schweizerhalle fire, temperatures well above 1100°C prevailed, so that mutagenic combustion products, if any had been formed, were destroyed. Therefore, the persistence of mutagenic products would have been possible only during the short extinguishing phase of the fire, when the temperature had dropped substantially. In conclusion, the mutagenicity tests performed indicated that fire-exposed extracts from locations A and B were only marginally more active in comparison with control extracts from filters exposed after the fire. The increases noted for these locations were conceivable, since location B was situated in the center of the smoke trail, only some 4
1100
km away from the site of the fire, and location A was even closer, only 0.4 km away. However, average genotoxicity observed for extracts from these locations was still within or only slightly above the long-term fluctuation of ambient air genotoxicity as shown by control samples taken in March/April 1987. This suggests that the small increases observed in extracts from filters in operation during the fire period did not pose a risk for the exposed population of Basle.
6.6.DISCUSSION OF TOXICOLOGICAL INVESTIGATIONS K.E. Suter, Sandoz Ltd., Drug Safety Assessment, Toxicology, CH-4002 Basle, Switzerland and CH. Schlatter, /nstitute of Toxicology, Swiss Federal /nstitute of Technology and University of Zurich, CH-8603 Schwerzenbach Extracts from building ventilation filters from four locations, 0.4 to 6.8 km downwind of the fire, were investigated in three different mutagenicity tests, i.e. Ames test, V79 chromosome aberration test, and Drosophila wing spot test. Each test covered different genetic end points and represented a different biological system. In addition, extracts from the particle part of respiratory filters worn by the members of the clearing squad a few days after the fire were investigated. Mutagenicity was expressed relative to the volume of the air passed through the filters of which extracts had been prepared in order to have a basis for comparison. Investigations of filter extracts from both building ventilation filters and respiratory filters confirmed that ambient air from an industrial and/or urban area is generally mutagenic. Therefore, potential genotoxicity induced by the combustion emissions from the Schweizerhalle fire has to be seen as a superimposition on this industrial/urban background level. Investigations of building ventilation filters showed that genotoxicity varied considerably between the different locations. In the case of the Ames test, differences of up to a factor of 100 were observed. As demonstrated by all three test systems, extracts from location B, whether influenced by the fire or not, were clearly more mutagenic than those from the other locations. The local variability of genotoxicity found in this project for filter extracts from various places confirmed previous observations which had demonstrated that local combustion sources and micro-climatic conditions (Meller et al., 1983; Reali et al., 1984; Tokiwa et al., 1983) are decisive factors for the mutagenic activity of filter extracts. Besides local variability there was also a marked seasonal fluctuation of genotoxicity as shown by the control extracts taken in November 1986, shortly after the fire, and for three successive periods in March/April 1987. The variations of the mutagenic potencies observed in the Ames test for the same location were in the order of a factor of up to 17. Since the control measurements in this project were restricted to a few short periods, and did not e.g. include a typical smog situation, it can be assumed that the control data probably do not represent the whole spectrum of seasonal variability usually encountered in the Basle area. Seasonal variability of ambient air mutagenicity is well known (Alfheim et al., 1983; Alink et al., 1983; Daisey et al., 1980; Reali et al., 1984; Whong et al., 1981). It is important to note that the mutagenic activity observed in the Ames test was in the range observed for other towns, suggesting that the air quality in Basle is comparable to that of other urban areas (Tokiwa et al., 1983). In comparison to filters exposed shortly after the fire, the following fire exposed-filters showed increased activities. Ames test: location B by a factor of up to 5.3, location A by a factor of up to 2.2. Chromosome aberrations: location B by a factor of 2.1. No differences were noted in the Ames test for locations C and D and for locations A, C
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and D in the chromosome aberration test. There were also no relevant differences found in the Drosophila wing spot test for locations A and B. Extracts from locations C and D were not investigated in this test. There is little information on genotoxic activity of particulate matter resulting from accidental fires. Viau et al., 1982 Investigated extracts from forest-fire polluted air. In the Ames test forest-fire polluted air was 12-38 times more mutagenic than urban air. Similarly, 43 times more SCE's were induced in cultured human lymphocytes. in comparison to these data, increases found for the extracts from locations A and B were rather small. However, total exposure of these filters lasted 13 days, and the fire exposure lasted only 6 hrs. Thus, the mutagenic activity resulting from the fire was superimposed on, and diluted by, the background actvity. For the evaluation of mutagenic/carcinogenic effects, the total dose over a prolonged period of time rather than short-term dose increases are important. Therefore for risk assessment purposes the determination of average mutagenicity resulting from exposure over several days, as in the case of the extracts investigated in the filter project, is considered appropriate. The average mutagenicity of fire-exposed extracts, those of locations A and B included, was within the seasonal fluctuation or only slightly above it. This suggests that the fire in Schweizerhalle did not lead to a detectable increase of the mutagenic risk to which the population of Basle is normally exposed. This conclusion, derived from the results of the tests of building ventilation filters, was in principle confirmed by the investigations of respiratory mask filters. Since only the filters worn by the members of the clearing squad showed increased concentrations of organic material, investigations by means of the Ames test were restricted to these filters. Results showed that the air at the site of the fire between November 2-4, 1986 did not contain more mutagenic components than ambient air in the area of the Sandoz Ltd. plant in Basle between February 17-24, 1987. Although the situation at the site of the fire during the clearance work cannot be regarded as fully representative of the situation during the fire, it can be assumed that if potent mutagens with moderate volatility had been formed they should have still been present In the air inhaled by the clearing squad a few days after the fire. They would have been detected in extracts from respiratory filters, as were hydrocarbons, phosphorous and sulfurous compounds in the analytical Investigations. Although some uncertainties remain about the mutagenicity results because of the limited amount of extracted material available, and about the filter parameters, which could only be estimated for the respiratory filters, Ames test results Indicated that no excessive amounts of highly active mutagens were present during the fire. The lack of excessive amounts of potent mutagenic combustion products may be seen in the light of the findings of Fisher et a1.(1979) and Pani et al. (1983). They showed that after heating coal-fly ash or dust from an incinerator to over 350°C, the mutagenic activity was lost. In the initial phase of the Schweizerhalle fire, temperatures well above 1100°C prevailed, so that mutagenic combustion products, if any had been formed, were destroyed. Therefore, the persistence of mutagenic products would have been possible only during the short extinguishing phase of the fire, when the temperature had dropped substantially. In conclusion, the mutagenicity tests performed indicated that fire-exposed extracts from locations A and B were only marginally more active in comparison with control extracts from filters exposed after the fire. The increases noted for these locations were conceivable, since location B was situated in the center of the smoke trail, only some 4
1100
km away from the site of the fire, and location A was even closer, only 0.4 km away. However, average genotoxicity observed for extracts from these locations was still within or only slightly above the long-term fluctuation of ambient air genotoxicity as shown by control samples taken in March/April 1987. This suggests that the small increases observed in extracts from filters in operation during the fire period did not pose a risk for the exposed population of Basle.