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Study Information
Study Attribute Value
CEBS Accession Number: 002-01073-0007-0000-0
Chemical Name: 1,3-Dichloro-5,5-dimethylhydantoin
CASRN: 118-52-5
NTP Study Type: Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID: 659873
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 Ethanol 
 0         
 67 88 49 24 24
    79 103 48 20
    70 103 75 36
    65 106 27 14
Test Chemical 1,3-Dichloro-5,5-dimethylhydantoin 
6.25      
 58 85 47 27 25
    71 92 47 22
  
12.5       
 68 70 73 36 42*
    57 72 82 48
  
25         
 67 72 86 43 33
    55 64 40 24
  
50         
 60 47 90 50 46*
    53 51 67 42
  
100         
 36 9 435 403 391*
    36 9 409 379
Positive Control Methyl Methane Sulfonate 
15         
 40 30 156 129 108*
    35 21 92 87
Methyl Methane Sulfonate 
250         
 42 43 363 292 256*
    47 64 314 221

Nonactivation Trial: 2 Experiment Call: Inconclusive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 61 99 117 64 58
    66 86 132 67
    63 112 91 48
    59 104 93 53
Test Chemical 1,3-Dichloro-5,5-dimethylhydantoin 
20         
 106 136 148 46 44
    104 131 127 41
  
40         
 103 107 106 34 41
    94 84 133 47
  
60         
 85 87 81 32
    123r 118 123 33
  
80         
 100 95 116 39 36
    96 62 96 33
  
100         
 87 69 109 42 36
    92 93 85 31
Positive Control Methyl Methane Sulfonate 
15         
 29 29 156 176 163*
    28 27 126 149
Methyl Methane Sulfonate 
250         
 92 151 154 56 58
    90 160 162 60

Nonactivation Trial: 3 Experiment Call: Negative
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 77 103 100 43 43
    86 85 136 53
    79 103 88 37
    85 108 93 37
Test Chemical 1,3-Dichloro-5,5-dimethylhydantoin 
10         
 76 93 92 41 41
    86 90 106 41
  
20         
 78 66 102 43 46
    92 92 132 48
  
40         
 75 61 97 43 48
    83 71 132 53
  
60         
 63 67 125 66 61
    70 59 119 57
  
80         
 75 48 134 59 61
    85 62 161 63
  
100         
   
Positive Control Methyl Methane Sulfonate 
20         
 24 12 223 316 314*
    11 6 103 312

Nonactivation Trial: 4 Experiment Call: Positive
  Conc.
ug/mL 		Cloning
Efficiency 		Relative Total
Growth 		Mutant Colonies Mutant Frequency Avg Mutant Frequency
Vehicle Control Ethanol 
 0         
 86 96 87 34 29
    85 106 56 22
    93 101 74 27
    78 97 77 33
Test Chemical 1,3-Dichloro-5,5-dimethylhydantoin 
45         
 107 53 78 24 28
    89 48 87 32
  
55         
 71 36 59 28 34
    81 35 97 40
  
65         
 73 28 85 39 37
    69 15 73 36
  
75         
 69 21 108 52 51*
    71 21 109 51
  
85         
 43 3 265 207 162*
    78 6 274 117
  
95         
   
Positive Control Methyl Methane Sulfonate 
15         
 43 34 297 233 224*
    52 34 337 215

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