Table 4.

Focal and diffuse hyperplasia of the small intestine in B6C3F1 mice exposed to SDD in drinking water for 2 years.

Tissue	Incidence/no. of animals necropsied (mean severity)a
Males
Concentration (mg/L)	0	14.3	28.6	85.7	257.4
Duodenum
Epithelium, hyperplasia
Focal	0/50	0/50	0/50	1/50 (3.0)	2/50 (3.5)
Diffuse	0/50	11/50** (2.0)	18/50** (1.6)	42/50** (2.1)	32/50** (2.1)
Females
Concentration (mg/L)	0	14.3	57.3	172	516
Duodenum
Epithelium, hyperplasia
Focal	0/50	0/50	1/50 (2.0)	2/50 (3.0)	0/50
Diffuse	0/50	16/50** (1.6)	35/50** (1.7)	31/50** (1.6)	42/50** (2.2)
Jejunum
Epithelium, hyperplasia
Diffuse	0/50	2/50 (2.0)	1/50 (2.0)	0/50	8/50** (1.9)

^aMean severity: 1, minimal; 2, mild; 3, moderate; 4, marked.

^**p ≤ 0.01 by poly-3 test.