Table 1.

Summary of tumor incidence findings in rodent bioassays

Gender/tumor type	EtO concentration (time-weighted average)a
NTP (1987) 2-year bioassay of B6C3F1 miceb,c
	0 ppm	50 ppm (16.3 mg/m3)	100 ppm (32.7 mg/m3)
Males
Lung adenomas plus carcinomas	11/49	19/49	26/49*
Females
Lung adenomas plus carcinomas	2/44	5/44	22/49*
Malignant lymphoma	9/44	6/44	22/49*
Uterine carcinoma	0/44	1/44	5/49j
Mammary carcinoma	1/44	8/44*	6/49
Lynch et al. (1984) 2-year bioassay of male F344 ratsd,e
	0 ppm	50 ppm (19.1 mg/m3)	100 ppm (38.1 mg/m3)
Splenic mononuclear cell leukemia	24/77	38/79*	30/76
Testicular peritoneal mesothelioma	3/78	9/79	21/79*
Brain mixed-cell glioma	0/76	2/77	5/79*
(Garman et al. (1985); Snellings et al. (1984)) 2-year bioassay of F344 ratsa,f,g
	0 ppmh	10 ppm (3.27 mg/m3)	33 ppm (10.8 mg/m3)	100 ppm (32.7 mg/m3)
Males
Splenic mononuclear cell leukemia	13/97 (13%)i	9/51 (18%)	12/39* (32%)	9/30* (30%)
Testicular peritoneal mesothelioma	2/97 (2.1%)	2/51 (3.9%)	4/39 (10%)	4/30* (13%)
Primary brain tumors	1/181 (0.55%)	1/92 (1.1%)	5/85* (5.9%)	7/87* (8.1%)
Females
Splenic mononuclear cell leukemia	11/116 (9.5%)	11/54* (21%)	14/48* (30%)	15/26* (58%)
Primary brain tumors	1/188 (0.53%)	1/94 (1.1%)	3/92 (3.3%)	4/80* (5%)

^aAdjusted to continuous exposure; 1 ppm = 1.83 mg/m³.

^bExposed 6 hr/d, 5 d/wk.

^cIncidence data were adjusted by the EPA by eliminating the animals that died prior to the occurrence of the first tumor or prior to 52 wk, whichever was earlier. No treatment-related effects on survival or body weight were observed.

^dExposed 7 hr/d, 5 d/wk.

^eMean body weights were statistically significantly decreased in both treated groups compared with controls, and increased mortality was observed in the treated groups, with the increase statistically significant in the 100-ppm exposure group (p < 0.01). The individual animal data for this study were not available.

^fSignificant decreases in mean body weight were observed in the 100-ppm exposure group in males and in the 100-ppm and 33-ppm exposure groups in females. Mortality was statistically significantly increased in the 100-ppm exposure groups of both sexes.

^gDenominators refer to the number of animals for which histopathological diagnosis was performed. For brain tumors, Garman et al. (1985) included animals in the 18-month and the 24-month kills and found dead or euthanized moribund of those alive at the time of the first brain tumor, whereas for the other sites, Snellings et al. (1984) included animals only at the 24-month kill.

^hResults for two control groups combined.

^INumbers in parentheses indicate percentage incidence values.

^jp = 0.058 by pairwise Fisher’s exact test compared to concurrent controls; however, uterine carcinomas are rare tumors in female B6C3F₁ mice, and p < 0.0001 by pairwise Fisher’s exact test compared to the NTP historical control incidence of 1/1,077 for inhalation (air) for female B6C3F₁ mice fed with the NIH-07 diet.

^*p < 0.05 by pairwise Fisher’s exact test.