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Study Information
Study Attribute Value
CEBS Accession Number: 002-01586-0001-0000-3
Chemical Name: Acetaminophen (4-hydroxyacetanilide)
CASRN: 103-90-2
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 034886_SCE
Study Result: Positive

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

Trial #: 1    Activation: No Activation    Date: 10/13/1986    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 1032 392 0.380 7.84 25.5 0.000
Test Chemical Acetaminophen (4-hydroxyacetanilide) 
5         
 50 1041 476 0.457 9.52 25.5 20.379 
16.7       
 50 1035 589 0.569 11.78 25.5 49.820 
50         
 50 1024 544 0.531 10.88 25.5 39.860 
166.7       
 0 0 0 0.000 0.00 31.6 N/A
Positive Control Mitomycin-C 
 0.001     
 50 1035 594 0.574 11.88 25.5 51.091
Mitomycin-C 
 0.01      
 5 105 215 2.048 43.00 25.5 439.067
Trend: 5.905        
Probability: 0.000        

Trial #: 2    Activation: No Activation    Date: 10/28/1986    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         
 25 512 224 0.438 8.96 25.5 0.000
Test Chemical Acetaminophen (4-hydroxyacetanilide) 
49.8       
 25 515 255 0.495 10.20 25.5 13.176 
100.5       
 25 514 262 0.510 10.48 25.5 16.509 
150         
 25 517 442 0.855 17.68 30.8 95.413 
200         
 0 0 0 0.000 0.00 30.8 N/A
Positive Control Mitomycin-C 
 0.001     
 25 512 292 0.570 11.68 25.5 30.357
Mitomycin-C 
 0.01      
 5 104 200 1.923 40.00 25.5 339.560
Trend: 8.084        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 10/14/1986    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 1038 381 0.367 7.62 25.5 0.000
Test Chemical Acetaminophen (4-hydroxyacetanilide) 
500         
 50 1036 452 0.436 9.04 25.5 18.864 
1666.7       
 50 1034 426 0.412 8.52 25.5 12.244 
5000         
 50 1041 644 0.619 12.88 25.5 68.542
Positive Control Cyclophosphamide 
 0.4       
 50 1025 638 0.622 12.76 25.5 69.578
Cyclophosphamide 
2         
 5 104 158 1.519 31.60 25.5 313.901
Trend: 7.701        
Probability: 0.000