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Study Information
Study Attribute Value
CEBS Accession Number: 002-01867-0010-0000-5
Chemical Name: Chloroform
CASRN: 67-66-3
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 907612
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: Inconclusive
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 102 90 86 28 29
    104 96 83 27
    86# 97 84 32
    89 116 75 28
Test Chemical Chloroform 
 0.0156    
 123r 124 96 26
    87 70 83 32
  
 0.0313    
 103 121 91 29 28
    85 91 69 27
  
 0.0625    
 78 85 69 30 30
    107 98 100 31
  
 0.125     
 99 98 96 32 30
    108 128 87 27
  
 0.25      
 120 109 91 25 27
    87 87 72 28
  
 0.5       
 69 64 55 27
Positive Control Ethyl Methane Sulfonate 
500         
 7r 1 439 2090 1287*
    19# 6 687 1238
    18 7 735 1336

Nonactivation Trial: 2 Experiment Call: Negative
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 100 86 74 25 19
    108 102 64 20
    90 94 47 17
    117 118 52 15
Test Chemical Chloroform 
 0.0625    
 102 108 63 21 17
    86 105 36 14
    80 101 41 17
  
 0.125     
 92 61 76 28 22
    106 75 50 16
    84 74 59 23
  
 0.25      
 112 97 56 17 15
    88 46 30 11
    88 69 44 17
  
 0.5       
 101 48 42 14 22
    92 39 84 30
    125r 79 107 28
  
 0.75      
 109 96 74 23 22
    107 65 38 12
    85 13 78 30
  
1         
   
   
   
Positive Control Ethyl Methane Sulfonate 
500         
 10 2 453 1461 1182*
    33 12 913 936
    18 6 620 1148

Induced S9 Trial: 1 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 82# 112 78 32 33
    87 95 109 42
    72 85 45 21
    81# 107 86 36
Test Chemical Chloroform 
 0.78      
 96 103 144 50 51
    59 59 91 51
  
1.56      
 65 69 128 65 53*
    99 81 120 40
  
3.13      
 61 48 71 39 44
    70 49 102 49
  
6.25      
 62 20 180 96
  
12.5       
 96 8 301 105 111*
    71# 9 248 117
  
25         
   
Positive Control 3-Methylcholanthrene 
5         
 14 2 199 474 398*
    13 2 147 367
    13 2 138 354

Induced S9 Trial: 2 Experiment Call: Equivocal
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 90 104 104 38 34
    78 97 67 29
    78 99 79 34
Test Chemical Chloroform 
 0.004     
 61 67 43 24 24
    75 72 56 25
    61# 66 42 23
  
 0.006     
 66 51 55 28 27
    76# 73 54 24
    52 39 47 30
  
 0.008     
 63 44 52 28 28
    78 37 63 27
    81 42 74 31
  
 0.01      
 59 23 74 42 41
    82 29 101 41
    51 23 61 40
  
 0.012     
 80 20 132 55 54*
    77 26 107 46
    81 24 147 60
  
 0.014     
 65 16 97 50 53*
    57 18 92 54
    75 17 127 56
Positive Control 3-Methylcholanthrene 
5         
 14 1 186 448 546*
    11 1 195 582
    12 1 210 609

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         
 70 102 55 26 26
    58# 83 48 28
    69 111 52 25
    57 104 45 26
Test Chemical Chloroform 
10         
 46 33 60 44 38
    79 61 77 32
  
12         
 62 41 73 39 36
    66 46 68 34
    75 55 75 33
  
14         
 63 35 71 38 43*
    76 39 92 41
    60 36 90 50
  
16         
 64 38 78 41 44*
    65 35 97 50
    59 34 73 41
  
18         
 57 26 104 61 55*
    75 28 111 49
  
20         
 78 34 132 56 47*
    79 37 101 42
    88 38 109 41
Positive Control 3-Methylcholanthrene 
2.5       
 34 18 213 211 229*
    49 33 328 223
    31 16 236 252

Induced S9 Trial: 4 Experiment Call: No Call
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 95 111 86 30 30
    95# 103 91 32
    97 94 98 34
    110# 93 81 25
Test Chemical Chloroform 
5         
 95 35 119 42 38
    98# 32 150 51
    102# 36 63 21
  
10         
 98# 23 100.5 34 45
    109 23 153 47
    88 22 141 54
  
15         
 62*
    93 13 220 79
    105 11 141 45
  
20         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 98 74 424 144 150*
    100 71 466 156

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