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Study Information
Study Attribute Value
CEBS Accession Number: 002-02439-0007-0000-7
Chemical Name: Methyl isocyanate
CASRN: 624-83-9
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 752783
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.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 99 116 98 33 34
    88 108 67 25
    80 100 82 34
    77 76 99 43
Test Chemical Methyl isocyanate 
 0.5       
 61# 64 41 23 35
    67 58 88 44
    53 52 64 40
  
 0.75      
 42 44 51 40 43
    51 36 63 42
    55# 40 75 46
  
1         
 55 33 89 54 49
    52 27 93 59
    63 58 65 34
  
1.5       
 32 13 119 123 147*
    34# 14 176 172
    45 12 198 146
  
2         
 35 18 104 100 130*
    43# 9 213 165
    38# 9 143 126
  
3         
 36# 3 213 196 171*
    43 4 236 185
    53# 7 206 130
Positive Control Methyl Methane Sulfonate 
5         
 39# 21 519 442 454*
    40# 12 552 466

Nonactivation Trial: 2 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Dimethyl Sulfoxide 
 0         
 103 92 41 13 21
    105# 108 87 28
    99 100 71 24
    96 99 50 17
Test Chemical Methyl isocyanate 
 0.5       
 46 45 49 36 48*
    51 39 101 67
    45 40 56 42
  
 0.75      
 80 60 36 15 56*
    20 17 48 81
    46 37 100 72
  
1         
 34 25 111 110 74*
    42 29 115 92
    58 43 34 19
  
1.5       
 50 17 164 109 130*
    49 12 217 147
    37 16 148 135
  
2         
 66 12 366 185 169*
    32 7 186 195
    54 13 204 126
  
3         
 38 2 246 216 281*
    39 3 364 310
    48 5 452 317
Positive Control Methyl Methane Sulfonate 
5         
 65 40 547 283 254*
    63 35 502 266
    66# 47 422 213

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