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Study Information
Study Attribute Value
CEBS Accession Number: 002-01867-0011-0000-6
Chemical Name: Chloroform
CASRN: 67-66-3
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 994137
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: 1 Experiment Call: Positive
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 74 100 179 80 74
    70 82 185 88
    73 98 141 64
    76 120 143 63
Test Chemical Chloroform 
 0.41      
 51# 59 68 44
  
 0.51      
 51 53 70 46 48
    51 53 77 50
  
 0.64      
 65 69 50 26 36
    76 73 107 47
  
 0.8       
 70 50 129 61 57
    68 50 108 53
  
1         
 59 35 370 210 182*
    78# 32 361 155
  
1.25      
 65 11 1250 641 688*
    63 7 1381 735
Positive Control Ethyl Methane Sulfonate 
500         
 29 26 657 751 751*
    29# 24 772.5 883
    47 44 865 618

Nonactivation Trial: 2 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 97 98 133 46 36
    110 109 109 33
    95 102 87 31
    97 91 97 33
Test Chemical Chloroform 
 0.39      
 92 79 102 37 38
    105 89 121 39
  
 0.86      
 88 52 125 48 47
    114 56 162 47
  
 0.95      
 108 52 162 50 43
    92 50 101 37
  
1.06      
 95 47 106 37 34
    102 45 95 31
  
1.17      
 82 36 86 35 44
    108 38 169 52
  
1.31      
 110 40 157 47 52
    79 26 136 57
  
1.45      
 90 12 181 67 55
    92 24 116 42
Positive Control Ethyl Methane Sulfonate 
500         
 78 63 1098 472 518*
    70 55 1165 553
    53 43 838 527

Induced S9 Trial: 1 Experiment Call: No Call
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 65 108 208 106 119
    58# 95 232.5 134
    63 102 227 120
    63 95 218 116
Test Chemical Chloroform 
 0.003     
 69 107 236 113 117
    70 114 252 121
  
 0.005     
 70 98 279 133
  
 0.008     
 69 95 251 122 111
    78 92 235 100
  
 0.013     
 77 83 204 89 107
    69 76 261 126
  
 0.022     
 67 59 225 112 113
    64 51 220 114
  
 0.036     
 43 11 190 147 169
    49 17 278 191
  
 0.06      
   
Positive Control 3-Methylcholanthrene 
5         
 32 30 516 546 452*
    34 32 470 465
    44# 28 451.5 345

Induced S9 Trial: 2 Experiment Call: Positive
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 81 95 145 59 58
    91 106 165 60
    98 114 118 40
    77# 85 164 71
Test Chemical Chloroform 
 0.007     
 93 98 185 66 61
    91 96 151 55
  
 0.014     
 73# 70 185 85 69
    91 83 146 53
  
 0.017     
 88# 77 124 47 50
    97 81 151 52
  
 0.021     
 96 65 159 55 58
    81 60 147 61
  
 0.026     
 93# 53 155 56 56
    106# 60 180 57
  
 0.032     
 90 37 180 67 70
    81 30 180 74
  
 0.04      
 80 22 207 86 86
    81 23 208 86
  
 0.05      
 87 15 202 78 101*
    76 11 287 125
Positive Control 3-Methylcholanthrene 
5         
 69# 50 628.5 303 334*
    72 54 711 329
    54 39 598 371

Induced S9 Trial: 3 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 96 99 204 71 76
    97 103 248 86
    98 100 221 75
    104 98 224 72
Test Chemical Chloroform 
 0.013     
 86# 65 322.5 125 112
    91 68 271 100
  
 0.016     
 103 68 317 103 106
    94 70 306 109
  
 0.02      
 96 63 329 115 111
    85 57 274 108
  
 0.025     
 93 49 331 119 130*
    86 46 365 142
  
 0.031     
 103 47 375 122 113
    98 49 304 104
  
 0.038     
 80 28 369 154 153*
    68# 24 311 152
  
 0.048     
 70 15 342 164 168*
    63 16 323 172
  
 0.06      
 45 6 291 214 217*
    47 6 309 220
Positive Control 3-Methylcholanthrene 
5         
 17 3 384 746 838*
    17 3 456 921
    16 3 398 847

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