Sethoxydim Risk Assessment

Appendix 1: Toxicity of Sethoxydim (NP-55) and Poast to experimental mammals [94-99% a.i. unless 
otherwise specified]. 
Animal 
Dose/Exposure 
Response 
Reference 
Rats, 
0, 40, 100, or 250 
Significant decreases in body weight observed 
Nishibe and 
Sprague-Dawley, 
mg/kg NP-55 daily by 
at 100 and 250 mg/kg and in positive controls; 
Gotoh 1980 
mated females, 14 
gavage on days 7-17 of 
significant increases in liver weight observed at 
weeks old, 24/dose 
gestation
250 mg/kg and in positive controls; decreases 
MRID 
group, including 
in adrenal weights observed at 100 and 250 
00045863 
vehicle control and 
positive controls given 
mg/kg and in positive controls; no effects on 
positive control 
200 mg/kg aspirin 
number of corpora lutea, implantations, live 
cited as 
fetuses, sex ratios, or fetal weight observed at 
BASF 
any NP-55 dose level; and no significant 
1980b in 
abnormality observed in fetuses of any NP-55 
IRIS. 
treated group. 
Conclusion: These data indicate that NP-55 is 
not teratogenic to rats. 
Rats, 
daily gavage dose of 0, 
NOEL = 40 mg/kg (dams) 
Nisso Inst. 
Sprague-Dawley, 
40, 100, or 250 mg/kg 
NOEL = 250 mg/kg (fetuses) 
1980b 
14 weeks old, 
NP-55 on days 7-17 of 
24/dose group 
gestation. 
No teratogenic effects 
EPA/OTS 
vehicle control 
88-9200030 
(CMC) and 
vehicle control (CMC) 
Maternal toxicity included significant 
26 
positive control 
positive control (200 
reductions in body weight gains at 100 and 250 
(200 mg/kg 
mg/kg aspirin) 
mg/kg and in positive controls (200 mg/kg 
aspirin) 
aspirin); significant increases in liver weights 
at 250 mg/kg and in positive controls; and 
decreased adrenal weights at 100 and 250 
mg/kg and in positive controls.  Spleen weight 
increased significantly on in positive control 
group. 
Rabbits, New 
single daily gavage 
No teratogenic effects were observed at dose 
IRDC 
Zealand White, 
dose of 0, 40, 160, or 
#
160 mg/kg/day. 
1980a 
approx. 7 months 
480 mg/kg/day on days 
old, 6 pregnant 
6-28 of gestation 
Adverse effects at 480 mg/kg/day included 5 
EPA/OTS 
rabbits/dose group 
death, severe losses in maternal weight gain, 
88-9200030 
statistically significant and biologically 
26 
meaningful decreases in the number of viable 
fetuses, and a slight decrease in mean fetal body 
BASF 1980 
weight. 
MRID 
00045864 
Investigators conclude that adverse effects in 
high dose group indicated that 480 mg/kg/day 
Cited as 
of NP-55 was excessive for a teratology study 
BASF 
and that the reduced sample size for this dose 
1980c in 
level (only 2 litters) was insufficient for an 
IRIS. 
evaluation of the teratogenicity of the 
compound. 
Appendix 1 - 5 

---

Appendix 1: Toxicity of Sethoxydim (NP-55) and Poast to experimental mammals [94-99% a.i. unless 
otherwise specified]. 
Animal 
Dose/Exposure 
Response 
Reference 
ORAL -chronic 
Dogs, beagle, 
approximately 6 
months old, 
6/sex/dose group 
0, 300, 600, and 3600 
ppm in the diet for one 
year.  Based on 
measured food 
consumption, the 
male/female doses were 
0, 
8.86/9.41, 17.5/19.9, 
and 110/129 
mg/kg/day).  See 
unnumbered table on 
p. 21 of study. 
NOEL for liver effects and possible effects on 
the erythroid system = 300 ppm 
No mortality and no clinical signs of toxicity at 
any dose level. 
Liver effects and possible effects on the 
erythroid system were slight but considered 
treatment related. Hematological effects 
included slight but statistically significant 
decreases in erythrocyte counts, hemoglobin 
and hematocrit in males treated with 600 or 
3600 ppm (similar effects were sporadic in 
females at 3600 ppm), with a tendency toward 
recovery at 12 month interval.  Absolute and 
relative liver weights increased in males and 
females at 3600 ppm.  Liver lesions included 
trace or mild degrees of hepatocellular 
cytoplasmic alteration at 600 and 3600 ppm. 
At 3600 ppm (and in males at 600 ppm) the 
lesion was associated with increased liver 
IRDC 1984 
MRID 
00152669 
cited as 
BASF 1984 
in IRIS. 
Basis for 
RfD. 
alkaline phosphatase and high dose males also 
had slight increases in alanine 
aminotransferase. 
Rats, Fischer 344 
(C.F.), 50 days 
old, males 
(weighing 
94.2-172.4 g) and 
females (weighing 
60.4-133.3 g), 
55/sex/dose group 
0, 40, 120, or 360 ppm 
NP-55 in the diet for 
104 weeks. 
There were no treatment-related effects noted in 
a comparison of the clinical signs, survival 
data, opthalmoscopic findings, and gross and 
microscopic pathology findings. 
At all dose levels, there were statistically 
significant differences noted in growth analysis, 
food consumption values, clinical laboratory 
values, and organ/body weight values, 
compared with controls; however, these 
differences were not considered treatment 
Burdock et 
al.  1981 
MRID 
00100526 
related. 
Appendix 1 - 6 

---