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Study Information
Study Attribute Value
CEBS Accession Number: 002-02062-0001-0000-3
Chemical Name: Dimethyl hydrogen phosphite
CASRN: 868-85-9
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 601658_SCE
Study Result: Positive

Study Result: Positive
Activation Trial Trial Call
No Activation  1  Negative 
No Activation  2  Positive 
Induced Rat Liver S9  1_S9  Weakly Positive 
Induced Rat Liver S9  2_S9  Positive 

Trial #: 1    Activation: No Activation    Date: 07/13/1983    Trial Call: Negative   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1050 434 0.413 8.68 26.0 -5.304
Medium 
0         
 50 1047 457 0.436 9.14 26.0 0.000
Test Chemical Dimethyl hydrogen phosphite 
5         
 50 1048 368 0.351 7.36 26.0 -19.552 
16         
 50 1045 342 0.327 6.84 26.0 -25.021 
50         
 50 1040 348 0.335 6.96 26.0 -23.339 
160         
 50 1048 457 0.436 9.14 26.0 -0.095 
500         
 50 1046 403 0.385 8.06 26.0 -11.732 
1600         
 0 0 0 0.000 0.00 26.0 N/A
Positive Control Mitomycin-C 
 0.003     
 50 1047 1074 1.026 21.48 26.0 135.011
Trend: 0.040        
Probability: 0.484        

Trial #: 2    Activation: No Activation    Date: 08/04/1983    Trial Call: Positive   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1048 335 0.320 6.70 27.5 5.263
Medium 
0         
 50 1034 314 0.304 6.28 27.5 0.000
Test Chemical Dimethyl hydrogen phosphite 
250         
 50 1046 386 0.369 7.72 27.5 21.520 
500         
 50 1046 413 0.395 8.26 27.5 30.020 
1000         
 50 1047 457 0.436 9.14 27.5 43.734 
1000         
 50 1048 426 0.406 8.52 32.5 33.856 
1600         
 50 1041 358 0.344 7.16 32.5 13.246 
1600         
 0 0 0 0.000 0.00 27.5 N/A
Positive Control Mitomycin-C 
 0.005     
 50 1031 1426 1.383 28.52 27.5 355.462
Mitomycin-C 
 0.005     
 50 1045 1316 1.259 26.32 27.5 314.697
Trend: 2.894        
Probability: 0.002        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 08/04/1983    Trial Call: Weakly Positive   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1040 403 0.388 8.06 27.0 -0.412
Medium 
0         
 50 1046 407 0.389 8.14 27.0 0.000
Test Chemical Dimethyl hydrogen phosphite 
16         
 50 1044 422 0.404 8.44 27.0 3.884 
50         
 50 1048 452 0.431 9.04 27.0 10.845 
160         
 50 1047 462 0.441 9.24 27.0 13.405 
500         
 50 1048 472 0.450 9.44 27.0 15.749 
1600         
 50 1043 578 0.554 11.56 27.0 42.423 
5000         
 0 0 0 0.000 0.00 27.0 N/A
Positive Control Cyclophosphamide 
2         
 50 1042 2155 2.068 43.10 27.0 431.517
Cyclophosphamide 
2         
 50 1043 1847 1.771 36.94 27.0 355.114
Trend: 5.640        
Probability: 0.000        

Trial #: 2_S9    Activation: Induced Rat Liver S9    Date: 08/23/1983    Trial Call: Positive   
  Dose
µg/mL		 Number
Cells
Examined		 Number
Chromosomes
Examined		 Total
Number
SCEs		 SCE /
Chromosome		 SCE /
Cell		 Hours in
BRDU		 % Increase
Over Solvent
Control
Vehicle Control Negative (Not Specified) 
0         
 50 1040 383 0.368 7.66 26.0 -10.094
Medium 
0         
 50 1040 426 0.410 8.52 26.0 0.000
Test Chemical Dimethyl hydrogen phosphite 
250         
 50 1048 423 0.404 8.46 26.0 -1.462 
500         
 50 1050 487 0.464 9.74 26.0 13.230 
1000         
 50 1047 528 0.504 10.56 26.0 23.115 
1600         
 50 1050 599 0.570 11.98 26.0 39.271 
3000         
 50 1048 920 0.878 18.40 26.0 114.314 
4000         
 10 210 241 1.148 24.10 26.0 180.170
Positive Control Cyclophosphamide 
1.5       
 50 1049 1067 1.017 21.34 26.0 148.321
Cyclophosphamide 
1.5       
 50 1042 1245 1.195 24.90 26.0 191.693
Trend: 17.545        
Probability: 0.000