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Study Information
Study Attribute Value
CEBS Accession Number: 002-02934-0016-0000-7
Chemical Name: Tribromomethane
CASRN: 75-25-2
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 701597
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.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 61 82 95 52 53
    60 105 109 61
    66 110 111 56
    67 104 91 45
Test Chemical Tribromomethane 
50         
 87 140 65 25 25
    106 100 102 32
    86 160 49 19
  
75         
 64 128 92 48 34
    93 110 77 28
    73 146 57 26
  
100         
 100 113 101 34 39
    66 103 101 51
    115 109 114 33
  
150         
 79 110 96 40 47
    88 77 118 45
    68 111 111 55
  
200         
 82 80 124 50 43
    83 83 110 44
    95 72 102 36
  
250         
 78 88 100 43 85*
    53 8 223 140
    70 46 149 71
Positive Control Methyl Methane Sulfonate 
5         
 90 100 717 265 274*
    90 82 685 255
    72 101 653 304

Nonactivation Trial: 2 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 65 117 73 37 41
    82 117 109 44
    70 82 83 40
    64 84 79 41
Test Chemical Tribromomethane 
25         
 66 125 58 30 40
    73 108 82 37
    76 103 119 52
  
50         
 67 144 89 44 43
    69 130 76 37
    68 94 100 49
  
100         
 74 100 111 50 47
    71 100 102 48
    86 97 113 44
  
175         
 57 22 168 99 101*
    69 43 234 114
    74 41 201 91
  
200         
 79*
    88 52 189 71
    68 32 178 87
  
250         
 60 21 174 97
   
   
  
300         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 55 36 410 249 229*
    65 79 439 224
    68 85 437 213

Nonactivation Trial: 3 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 86 99 76 30 26
    83 101 63 25
    74 90 62 28
    101 111 69 23
Test Chemical Tribromomethane 
100         
 90# 50 101 37 33
    100 58 84 28
    62 39 65 35
  
150         
 87 36 36 14 25
    80 49 59 25
    84 39 90 36
  
175         
 63 29 72 38 34
    124r 54 14 4
    63 17 57 30
  
200         
 79 20 145 61 54*
    78 15 127 54
    91 17 129 47
  
225         
 82 8 120 49 45*
    78 15 50 21
    74 14 146 66
  
250         
 32
    80 9 126 52
    63 5 22 12
  
300         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 46 48 250 181 196*
    51 38 325 211

Induced S9 Trial: 1 Experiment Call: Equivocal
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 72 103 196 91 98
    61 120 163 89
    51 116 155 102
    52 62 170 109
Test Chemical Tribromomethane 
6.25      
 52 52 194 125 126
    58 50 249 143
    59 60 197 112
  
12.5       
 67 25 280 139 133
    49 29 218 147
    68 29 229 113
  
25         
 49 10 249 171 149*
    46 9 191 138
    62 11 255 137
  
50         
   
  
100         
   
   
Positive Control 3-Methylcholanthrene 
2.5       
 37 6 617 553 688*
    18 2 436 823

Induced S9 Trial: 2 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 80 114 165 69 79
    89 92 210 79
    91 101 223 82
    81 93 215 88
Test Chemical Tribromomethane 
2.5       
 60 64 124 69 61
    72 85 106 49
    73 61 138 63
  
5         
 69 45 187 90 68
    82 45 130 53
    66 53 121 62
  
10         
 55 27 157 96 108
    64 30 256 134
    51 23 142 94
  
25         
 47 5 234 165 122*
    64 10 213 111
    66 5 176 89
Positive Control 3-Methylcholanthrene 
2.5       
 43 24 789 612 736*
    29 11 677 765
    44 13 1084 831

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