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Study Information
Study Attribute Value
CEBS Accession Number: 002-02176-0001-0000-9
Chemical Name: Fenthion
CASRN: 55-38-9
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 574321_SCE
Study Result: Positive

Study Result: Positive
Activation Trial Trial Call
No Activation  1  Weakly Positive 
No Activation  2  Positive 
Induced Rat Liver S9  1_S9  Test Failure 
Induced Rat Liver S9  2_S9  Positive 
Induced Rat Liver S9  3_S9  Positive 

Trial #: 1    Activation: No Activation    Date: 11/16/1982    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 1013 430 0.424 8.60 25.5 0.000
Test Chemical Fenthion 
 0.57      
 50 1023 438 0.428 8.76 25.5 0.865 
1.9       
 0 0 0 0.000 0.00 0.0 N/A 
5.7       
 50 1031 491 0.476 9.82 25.5 12.192 
19         
 50 1017 595 0.585 11.90 33.5 37.828
Positive Control Mitomycin-C 
 0.01      
 5 101 206 2.040 41.20 25.5 380.493
Trend: 5.397        
Probability: 0.000        

Trial #: 2    Activation: No Activation    Date: 12/14/1982    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 1037 439 0.423 8.78 25.5 0.000
Test Chemical Fenthion 
13         
 50 1036 510 0.492 10.20 25.5 16.285 
20         
 50 1036 621 0.599 12.42 25.5 41.594 
26         
 50 1017 557 0.548 11.14 32.5 29.374 
40         
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Mitomycin-C 
 0.001     
 50 1022 593 0.580 11.86 25.5 37.062
Mitomycin-C 
 0.01      
 5 102 238 2.333 47.60 25.5 451.177
Trend: 5.104        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 11/16/1982    Trial Call: Test Failure   
  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 1021 427 0.418 8.54 25.5 0.000
Test Chemical Fenthion 
57         
 50 1028 463 0.450 9.26 25.5 7.693 
190         
 0 0 0 0.000 0.00 0.0 N/A
Trend: 1.105        
Probability: 0.135        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 12/14/1982    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 1030 427 0.415 8.54 25.5 0.000
Test Chemical Fenthion 
51         
 50 1029 467 0.454 9.34 25.5 9.474 
80         
 50 1025 542 0.529 10.84 25.5 27.551 
103         
 50 1021 605 0.593 12.10 32.5 42.935
Positive Control Cyclophosphamide 
 0.3       
 50 1029 607 0.590 12.14 25.5 42.293
Cyclophosphamide 
2         
 5 104 111 1.067 22.20 25.5 157.454
Trend: 6.156        
Probability: 0.000        

Trial #: 3_S9    Activation: Induced Rat Liver S9    Date: 02/01/1983    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 1026 504 0.491 10.08 25.5 0.000
Test Chemical Fenthion 
58.8       
 50 1016 772 0.760 15.44 35.0 54.682 
69.1       
 50 1027 790 0.769 15.80 35.0 56.593 
81.3       
 50 1020 836 0.820 16.72 35.0 66.849
Positive Control Cyclophosphamide 
 0.3       
 50 1020 729 0.715 14.58 25.5 45.494
Cyclophosphamide 
2         
 5 100 168 1.680 33.60 25.5 242.000
Trend: 8.456        
Probability: 0.000