Table 2.

Micronucleus formation in MCF-7 cells treated with B[a]P and/or lindane.

			Lindane (γ-HCH) (M)
B[a]P (M)	Micronuclei/1,000 binucleate cells	No lindane co-addition	10−12	10−11	10−10
Background	MN	21	67	64	78
	TMN	24	86	90	108
10−8	MN	28	86	77	123
	TMN	33	118	103	186
10−7	MN	45	120	115	159
	TMN	56	193	177	244
10−6	MN	91	167	135	139
	TMN	138	293	217	252
10−5	MN	110	170	132	200
	TMN	183	273	198	330

Abbreviations: MN, the number of micronucleated binucleate cells scored per treatment; TMN, the total number of micronuclei scored per treatment. MCF-7 cells were treated for 24 hr in the presence or absence of test agents, as indicated, before cytokinesis block with cytochalasin-B. After further 24-hr incubation, cells were fixed and stained with 5% Giemsa as described in “Materials and Methods.”