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Study Information
Study Attribute Value
CEBS Accession Number: 002-01223-0001-0000-1
Chemical Name: 2,4-Dichlorophenoxyacetic acid
CASRN: 94-75-7
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 079515_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  Negative 
Induced Rat Liver S9  2_S9  Negative 

Trial #: 1    Activation: No Activation    Date: 02/26/1982    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         
 25 513 203 0.396 8.12 25.5 0.000
Test Chemical 2,4-Dichlorophenoxyacetic acid 
50         
 50 1008 448 0.444 8.96 25.5 12.315 
167         
 50 1026 591 0.576 11.82 25.5 45.567
Positive Control Mitomycin-C 
 0.005     
 10 210 290 1.381 29.00 25.5 248.980
Trend: 5.210        
Probability: 0.000        

Trial #: 2    Activation: No Activation    Date: 03/03/1982    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 1020 401 0.393 8.02 26.5 0.000
Test Chemical 2,4-Dichlorophenoxyacetic acid 
198         
 50 1029 625 0.607 12.50 32.1 54.497 
248         
 50 1026 646 0.630 12.92 32.1 60.155 
299         
 50 1022 668 0.654 13.36 32.1 66.258 
352         
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Mitomycin-C 
 0.005     
 25 510 589 1.155 23.56 26.5 193.766
Trend: 7.545        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 02/26/1982    Trial Call: Negative   
  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 1039 477 0.459 9.54 25.5 0.000
Test Chemical 2,4-Dichlorophenoxyacetic acid 
500         
 50 1047 494 0.472 9.88 25.5 2.773 
1670         
 50 1045 497 0.476 9.94 25.5 3.595 
5000         
 0 0 0 0.000 0.00 25.5 N/A
Positive Control Cyclophosphamide 
1.5       
 25 515 688 1.336 27.52 25.5 190.990
Trend: 0.547        
Probability: 0.292        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 03/11/1982    Trial Call: Negative   
  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 382 0.364 7.64 25.5 0.000
Test Chemical 2,4-Dichlorophenoxyacetic acid 
3000         
 50 1035 398 0.385 7.96 25.5 5.598 
3500         
 50 1019 393 0.386 7.86 25.5 5.908 
4200         
 50 1036 452 0.436 9.04 25.5 19.809 
5000         
 0 0 0 0.000 0.00 0.0 N/A
Positive Control Cyclophosphamide 
1.5       
 50 1045 1072 1.026 21.44 25.5 181.702
Trend: 2.538        
Probability: 0.006