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Study Information
Study Attribute Value
CEBS Accession Number: 002-01586-0002-0000-4
Chemical Name: Acetaminophen (4-hydroxyacetanilide)
CASRN: 103-90-2
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 034886_CA
Study Result: Positive

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

Trial #:1   Activation: No Activation    Date: 11/04/1986    Harvest Time: 20 hour(s)   Trial Call: Positive   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 200 6 0.030 2.5 3 0.015 1.5 2 0.010 0.5 1 0.005 0.5
Dimethyl Sulfoxide 
0         
 200 6 0.030 3.0 1 0.005 0.5 1 0.005 0.5 4 0.020 2.0
Test Chemical: Acetaminophen (4-hydroxyacetanilide) 
1257         
 60 60 1.000 43.3 17 0.283 18.3 22 0.367 25.0 21 0.350 5.0 
2513         
 58 27 0.466 27.6 7 0.121 8.6 15 0.259 12.1 5 0.086 8.6 
3750         
 75 50 0.667 42.7 10 0.133 8.0 25 0.333 20.0 15 0.200 20.0 
5000         
 200 30 0.150 8.5 3 0.015 1.5 10 0.050 3.0 17 0.085 4.0
Positive Control: Mitomycin-C 
 0.05      
 200 38 0.190 16.0 22 0.110 9.5 16 0.080 7.0 0 0.000 0.0
Mitomycin-C 
 0.08      
 25 20 0.800 56.0 10 0.400 32.0 10 0.400 28.0 0 0.000 0.0
Trend: 2.307 0.071 1.238  
Probability: 0.011 0.472 0.108  


Trial #:1_S9   Activation: Induced Rat Liver S9    Date: 11/04/1986    Harvest Time: 12 hour(s)   Trial Call: Weakly Positive*   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 200 3 0.015 1.5 3 0.015 1.5 0 0.000 0.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 200 5 0.025 2.5 1 0.005 0.5 4 0.020 2.0 0 0.000 0.0
Test Chemical: Acetaminophen (4-hydroxyacetanilide) 
2513         
 200 6 0.030 3.0 4 0.020 2.0 2 0.010 1.0 0 0.000 0.0 
3750         
 200 13 0.065 4.5 9 0.045 4.0 3 0.015 1.0 1 0.005 0.5 
5000         
 200 31 0.155 11.0 13 0.065 5.5 17 0.085 7.0 1 0.005 0.5
Positive Control: Cyclophosphamide 
7.5       
 200 15 0.075 7.5 5 0.025 2.5 10 0.050 5.0 0 0.000 0.0
Cyclophosphamide 
37.5       
 25 10 0.400 24.0 3 0.120 12.0 7 0.280 16.0 0 0.000 0.0
Trend: 3.726 3.155 2.740  
Probability: 0.000 0.001 0.003  


Trial #:2_S9   Activation: Induced Rat Liver S9    Date: 01/16/1987    Harvest Time: 12 hour(s)   Trial Call: Weakly Positive   
  Dose
µg/mL		 Total
Cells Examined		 Total Aberrations Complex Aberrations Simple Aberrations Other Abs
No. of
Abs		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs		 No. of
Abs.		 Abs
Per
Cell		 % Cells
With
Abs
Vehicle Control: Negative (Not Specified) 
0         
 100 1 0.010 1.0 1 0.010 1.0 0 0.000 0.0 0 0.000 0.0
Dimethyl Sulfoxide 
0         
 100 2 0.020 2.0 0 0.000 0.0 2 0.020 2.0 0 0.000 0.0
Test Chemical: Acetaminophen (4-hydroxyacetanilide) 
3800         
 100 10 0.100 5.0 6 0.060 4.0 4 0.040 3.0 0 0.000 0.0 
4400         
 100 10 0.100 8.0 3 0.030 3.0 7 0.070 5.0 0 0.000 0.0 
5000         
 100 15 0.150 12.0 6 0.060 5.0 9 0.090 7.0 0 0.000 0.0
Positive Control: Cyclophosphamide 
7.5       
 100 17 0.170 17.0 3 0.030 3.0 14 0.140 14.0 0 0.000 0.0
Cyclophosphamide 
37.5       
 25 20 0.800 56.0 12 0.480 44.0 8 0.320 28.0 0 0.000 0.0
Trend: 2.935 1.822 1.882  
Probability: 0.002 0.034 0.030