title: Erratum.
abstract: In the report "Mutagenicity of fly ash particles in Paramecium" by J. Smith-Sonneborn et al. (9 Jan., p. 180), Tables 1 and 2 are printed incorrectly. Significance lines are missing from both tables and "uninduced" should read "induced" in the sixth, eighth, and ninth entries of the first column in Table 1. The tables are reprinted below as they should have appeared. Table 1. Mutagenic effect of fly ash and heat-treated fly ash in Paramecium. Values not connected by the same line are significantly different from each other (Wilcoxon matched-pairs signed-ranks test, alpha = .05). The data from six experiments were pooled since the control values for autogamous progeny were not significantly different. Cerophyl is the ryegrass extract used for cultivation of Paramecium. Induced S-9 is the Ames liver microsome fraction from rats receiving Arochlor 1254 (polychlorinated biphenyl) to activate the enzymes for conversion of promutagens to mutagenic form; uninduced S-9 is from rats receiving corn oil only (the vehicle for the Arochlor). Glass beads (1 to 3 ,microm) suspended in either induced or uninduced S-9 were used as a negative control for nonnutritive particles. Kaolinite was also used in one experiment, and the results were the same as those for the glass beads. Benzo[a]pyrene was the positive control for mutagenicity requiring induced S-9. The initial concentration of suspended fly ash was 535 ,microg/ml. The average number of affected progeny from treated parent cells was 20 percent higher than the average number of affected control progeny. Since one mutation would theoretically yield only 4 affected progeny in 16 autogamous progeny from a treated parent cell (6), the percentages, though low, reflect significant damage. [See table in the PDF file] Table 2. Mutagenicity of heat-treated fly ash extracted with HCl or DMSO. Values not connected by the same line are significantly different from each other (pairwise comparisons of proportions, P < .05). The concentration of fly ash particles suspended in uninduced S-9 was 1068 ,ug/ml. The higher than usual value for mutagenicity in the controls can be attributed to the considerable age of the clone used here [micronuclear damage increases with age (12)]. [See table in the PDF file].