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Study Information
Study Attribute Value
CEBS Accession Number: 002-02445-0001-0000-8
Chemical Name: Methyl parathion
CASRN: 298-00-0
NTP Study Type: Genetic Toxicology - Mammalian Cell Cytogenetics
NTP Study ID: 433667_SCE
Study Result: Positive

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

Trial #: 1    Activation: No Activation    Date: 01/04/1983    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 Dimethyl Sulfoxide 
0         
 50 1046 506 0.484 10.12 26.0 0.000
Test Chemical Methyl parathion 
12.5       
 50 1051 764 0.727 15.28 26.0 50.270 
25         
 50 1038 980 0.944 19.60 26.0 95.169 
50         
 0 0 0 0.000 0.00 33.7 N/A
Positive Control Mitomycin-C 
 0.001     
 50 1047 626 0.598 12.52 26.0 23.597
Mitomycin-C 
 0.01      
 5 105 222 2.114 44.40 26.0 337.064
Trend: 12.405        
Probability: 0.000        

Trial #: 1_S9    Activation: Induced Rat Liver S9    Date: 12/01/1982    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 Dimethyl Sulfoxide 
0         
 50 1046 466 0.446 9.32 25.5 0.000
Test Chemical Methyl parathion 
16.7       
 50 1041 476 0.457 9.52 25.5 2.637 
50         
 50 1043 587 0.563 11.74 25.5 26.328 
167         
 50 1049 998 0.951 19.96 25.5 113.551
Positive Control Cyclophosphamide 
 0.3       
 50 1046 593 0.567 11.86 25.5 27.253
Cyclophosphamide 
2         
 5 104 145 1.394 29.00 25.5 212.954
Trend: 15.217        
Probability: 0.000