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Study Information
Study Attribute Value
CEBS Accession Number: 002-02380-0003-0000-8
Chemical Name: Malathion
CASRN: 121-75-5
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 973704_SCE
Study Result: Positive

Study Result: Positive
Activation Trial Trial Call
No Activation  1  Weakly Positive 
Induced Rat Liver S9  1_S9   
Induced Rat Liver S9  2_S9  Positive 

Trial #: 1    Activation: No Activation    Date: 09/01/1982    Trial Call: Weakly Positive   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Dimethyl Sulfoxide 
0         
 50 1034 523 0.506 10.46 26.0 0.000
Test Chemical Malathion 
4.03      
 50 1046 561 0.536 11.22 26.0 6.035 
12.1       
 50 1040 601 0.578 12.02 26.0 14.251 
40.3       
 50 1031 917 0.889 18.34 30.0 75.845
Positive Control Mitomycin-C 
 0.001     
 50 1044 778 0.745 15.56 26.0 47.332
Mitomycin-C 
 0.01      
 5 106 257 2.425 51.40 26.0 379.343
Trend: 10.906        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 09/01/1982    Trial Call:   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Dimethyl Sulfoxide 
0         
 50 1049 460 0.439 9.20 26.0 0.000
Test Chemical Malathion 
121         
 50 1041 550 0.528 11.00 26.0 20.484
Positive Control Cyclophosphamide 
 0.35      
 50 1047 730 0.697 14.60 26.0 58.999
Cyclophosphamide 
2         
 5 105 153 1.457 30.60 26.0 232.292
Trend: 0.000        
Probability: 0.000        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 09/14/1982    Trial Call: Positive   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Dimethyl Sulfoxide 
0         
 50 1046 488 0.467 9.76 25.8 0.000
Test Chemical Malathion 
298         
 50 1047 761 0.727 15.22 34.5 55.794 
351         
 50 1040 886 0.852 17.72 34.5 82.605 
403         
 50 1046 594 0.568 11.88 34.5 21.721
Positive Control Cyclophosphamide 
 0.35      
 50 1047 608 0.581 12.16 25.8 24.471
Cyclophosphamide 
2         
 5 105 121 1.152 24.20 25.8 147.006
Trend: 4.093        
Probability: 0.000