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Study Information
Study Attribute Value
CEBS Accession Number: 002-02269-0010-0000-2
Chemical Name: Hydroquinone
CASRN: 123-31-9
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 327913
Study Result: Positive


Table Instructions and Notes:
Studies are indicated to be "Nontoxic" when the observed reductions in relative total growth did not indicate that the maximum tolerated dose was achieved.

Nonactivation Trial: 2 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Methanol 
 0         
 85# 106 60 24 22
    93 98 49 18
    61 100 51 28
    76 96 43 19
Test Chemical Hydroquinone 
3.125     
 13 5 226 565 419*
    58 30 472 274
  
6.25      
 37 9 598 541 542*
    48 13 778 542
  
12.5       
 25 7 624 843 857*
    27 7 697 871
  
25         
 30# 7 610.5 686 773*
    28# 6 716 860
  
50         
   
Positive Control Ethyl Methane Sulfonate 
250         
 120# 114 390 108 108*

Nonactivation Trial: 3 Experiment Call:
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 90 87 123 45 38
    52 90 65 42
    62 109 88 47
    93 114 54 19
Test Chemical Hydroquinone 
 0.625     
 102 71 156 51 49
    81 68 115 47
  
1.25      
 28 16 161 195 179*
    36 22 175 164
  
2.5       
 12 4 231 642 624*
    15 7 270 607
  
5         
 13 1 718 1915
   
  
10         
   
Positive Control Ethyl Methane Sulfonate 
250         
 93 58 873 313 306*
    70 66 623 299

Induced S9 Trial: 2 Experiment Call:
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 79 100 183 77 70
    68 98 144 70
    70 102 142 67
    91 99 176 65
Test Chemical Hydroquinone 
 0.625     
 94 116 187 67 72
    90 133 210 78
  
1.25      
 81 105 169 69 78
    73 99 188 86
  
2.5       
 98 93 380 130 134*
    75 81 310 138
  
5         
 61 20 619 338 328*
    70 18 670 318
  
10         
 44 7 582 443 464*
    43 7 630 485
Positive Control 3-Methylcholanthrene 
2.5       
 45 47 653 480 451*
    55 57 693 423

Footnotes:
Asterisks(*) indicate significant responses.
r = rejected value due to quality control criteria
# = reduced sample size because of the loss of one culture dish due to contamination