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Study Information
Study Attribute Value
CEBS Accession Number: 002-01179-0020-0000-2
Chemical Name: 2,3,7,8-Tetrachlorodibenzo-p-dioxin
CASRN: 1746-01-6
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 056688
Study Result: Negative


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: 1 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 76 118 98 43 43
    62 90 112 60
    67 98 68 34
    77 94 82 35
Test Chemical 2,3,7,8-Tetrachlorodibenzo-p-dioxin 
 0.0625    
 76 110 108 47 39
    85 118 80 31
  
 0.125     
 64 112 56 29 33
    64 101 72 38
  
 0.25      
 80 104 71 30 30
    65 108 60 31
  
 0.5       
 76 98 58 26 27
    71 105 61 29
  
1         
 86 101 70 27 27
    70 90 58 28
Positive Control Methyl Methane Sulfonate 
15         
 47 34 208 148 138*
    46 45 176 129

Nonactivation Trial: 2 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 72 99 79 36 24
    76 98 44 19
    86 114 48 19
    89 88 60 23
Test Chemical 2,3,7,8-Tetrachlorodibenzo-p-dioxin 
 0.0625    
 75 119 53 23 22
    80 110 49 20
  
 0.125     
 78 120 72 31 34
    42 54 47 37
  
 0.25      
 80 176 56 23 33
    63 83 81 43
  
 0.5       
 90 127 49 18 23
    75 98 61 27
  
1         
 97 115 70 24 29
    98 88 98 33
Positive Control Methyl Methane Sulfonate 
15         
 51 41 190 124 123*
    60 43 217 122

Induced S9 Trial: 1 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 85 111 80 31 30
    87 103 98 37
    75 96 46 20
    83 90 80 32
Test Chemical 2,3,7,8-Tetrachlorodibenzo-p-dioxin 
 0.0625    
 92 87 106 39 44
    88 92 132 50
  
 0.125     
 81 79 119 49 48*
    86 86 123 47
  
 0.25      
 99 86 104 35 37
    92 85 110 40
  
 0.5       
 83 90 105 42 36
    102 101 90 30
  
1         
 103 96 112 36 37
    87 93 97 37
Positive Control 3-Methylcholanthrene 
2.5       
 93 73 373 134 139*
    78 73 337 145

Induced S9 Trial: 2 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 88 103 82 31 26
    84 91 52 21
    86 109 67 26
    70 96 51 24
Test Chemical 2,3,7,8-Tetrachlorodibenzo-p-dioxin 
 0.0625    
 76 110 71 31 30
    101 110 89 29
  
 0.125     
 82 123 64 26 28
    88 117 79 30
  
 0.25      
 96 150 107 37 32
    71 105 58 27
  
 0.5       
 75 107 81 36 36
    92 114 100 36
  
1         
 91 126 79 29 29
    94 109 79 28
Positive Control 3-Methylcholanthrene 
2.5       
 81 97 339 139 130*
    92 98 330 120

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