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Study Information
Study Attribute Value
CEBS Accession Number: 002-02465-0011-0000-1
Chemical Name: Methylene chloride
CASRN: 75-09-2
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 502376
Study Result: Equivocal


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 Ethanol 
 0         
 81 87 73 30 31
    98 99 74 25
    103 104 92 30
    80 110 97 40
Test Chemical Methylene chloride 
 0.5       
 105 122 97 31 40
    81 107 114 47
    102 93 128 42
  
1         
 80 104 98 41 40
    81 103 100 41
    86 91 102 39
  
2         
 91 71 140 51 57*
    83 61 143 58
    65 58 119 61
  
3         
   
   
Positive Control Methyl Methane Sulfonate 
5         
 54 49 558 342 296*
    67 53 521 259
    66 52 564 286

Nonactivation Trial: 2 Experiment Call: Equivocal
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 99 112 92 31 32
    82 96 84 34
    80 98 80 33
    83 94 74 30
Test Chemical Methylene chloride 
 0.25      
 100# 115 77 26 32
    80 88 91 38
    101 98 98 32
  
 0.5       
 74 110 70 32 34
    69# 105 73 35
    88 84 95 36
  
 0.75      
 87 95 88 34 41
    75 88 117 52
    84 83 97 38
  
1         
 83# 80 102 41 43
    86 88 115 45
    72 102 93 43
  
1.5       
 91 44 144 53 45
    96 93 111 39
    97 84 128 44
  
2         
 73 55 96 44 47
    81 66 132 55
    76 79 95 41
Positive Control Methyl Methane Sulfonate 
5         
 65 56 487 250 284*
    64# 57 525 274
    62 44 605 328

Nonactivation Trial: 3 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 90# 100 97 36 31
    85 78 80 31
    88 109 89 34
    97 112 67 23
Test Chemical Methylene chloride 
1000         
 75 75 44 20 33
    75 86 80 36
    54 59 71 44
  
1500         
 70 63 78 37 38
    83 37 89 36
    71# 56 85 40
  
2000         
 72 51 86 40 36
    84 45 88 35
    87 43 86 33
  
2500         
 74 35 112 51 54*
    77# 33 129 56
    85 23 140 55
Positive Control Methyl Methane Sulfonate 
5         
 82*
    94 79 192 68
    76 80 217 95

Induced S9 Trial: 1 Experiment Call: Positive
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 69 90 154 75 47
    95 117 108 38
    90# 101 82 30
    83 93 112 45
Test Chemical Methylene chloride 
 0.25      
 89 82 190 71 56
    83 84 123 49
    82 63 114 46
  
 0.5       
 80 70 150 63 60
    88 82 138 52
    81 55 154 64
  
1         
 106 58 137 43 50
    78 63 145 62
    117 52 157 45
  
1.5       
 98 56 158 54 55
    86# 67 153 59
    88 58 134 51
  
2         
 95 52 242 85 82*
    107 58 257 80
  
3         
 80 15 206 85 81*
    99 27 185 62
    77 25 216 94
Positive Control 3-Methylcholanthrene 
2.5       
 60 21 697 389 348*
    76 43 721 318
    63 28 643 338

Induced S9 Trial: 2 Experiment Call: Equivocal
  Conc.
uL/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 68 63 121 59 47
    86 127 89 35
    79 117 111 47
    88 92 124 47
Test Chemical Methylene chloride 
 0.25      
 70 70 129 62 61
    68 62 126 62
    77 91 140 60
  
 0.5       
 66 84 139 70 62
    80 102 124 52
    73 72 138 63
  
1         
 79 62 156 66 63
    100 77 181 61
    76 83 145 64
  
1.5       
 94 72 147 52 68
    69 52 147 72
    76 71 185 81
  
3         
 67 11 335 166 124*
    78 19 187 80
    63 14 239 127
Positive Control 3-Methylcholanthrene 
2.5       
 71# 29 822 385 485*
    44 23 721 552
    50 18 780 517

Induced S9 Trial: 3 Experiment Call: Negative and Non-Toxic
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 117 113 192 54 62
    104 111 194 62
    82 83 165 67
    111 94 211 64
Test Chemical Methylene chloride 
1000         
 62 66 155 84 71
    91 77 186 68
    84 82 154 61
  
1500         
 87 67 190 73 67
    87 70 191 73
    93 82 152 54
  
2000         
 95 56 235 82 79
    102 81 205 67
    79 52 208 88
  
2250         
 101 51 228 75 67
    103 66 196 63
    87 44 167 64
  
2500         
 93 29 150 54 67
    97 37 187 65
    81 27 199 82
Positive Control 3-Methylcholanthrene 
2.5       
 84 52 910 360 350*
    79 57 624 264
    65 33 822 425

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