Genetic Toxicology - Mammalian Cell Mutagenicity

Study Information
Study Attribute	Value
CEBS Accession Number:	002-02380-0020-0000-7
Chemical Name:	Malathion
CASRN:	121-75-5
NTP Study Type:	Genetic Toxicology - Mammalian Cell Mutagenicity
NTP Study ID:	911111
Study Result:	Equivocal

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Table Instructions and Notes:
Studies are indicated to be "Nontoxic" when the observed reductions in relative total growth did not indicate that the maximum tolerated dose was achieved.

Nonactivation Trial: 1 Experiment Call: Equivocal
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	82	96	116	47	38
			73	95	75	34
			91	122	73	27
			70	87	94	45
Test Chemical	Malathion	2.5	90	99	90	33	39
			73	89	78	36
			73	70	102	47
		5	58	38	76	43	43
			91	37	135	50
			76	32	83	36
		10	71	21	98	46	69*
			28	8	65	77
			46	13	116	85
		20


Positive Control	Methyl Methane Sulfonate	5	71	86	529	250	329*
			55	66	525	318
			41	49	510	420

Nonactivation Trial: 2 Experiment Call: Positive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	85	104	81	32	33
			83	101	70	28
			82	98	93	38
			84	97	85	34
Test Chemical	Malathion	1.25	88	112	72	27	31
			94	14	104	37
			71	95	62	29
		2.5	77	97	61	26	29
			87	61	87	34
			84	76	69	27
		5	70	38	101	48	40
			78	29	101	43
			89	32	81	30
		7.5	91	19	100	37	45
			79#	14	123	52
			71	14	99	47
		10					97*
			69	6	202	98
			59	5	172	97
		15


Positive Control	Methyl Methane Sulfonate	5	60	55	648	360	375*
Positive Control			56	51	658	389	375*

Nonactivation Trial: 3 Experiment Call: Inconclusive
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	73	173	71	32	44
			48r	102	62	43
			51#	21	98	64
			90	106	100	37
Test Chemical	Malathion	2.5	81	143	92	38	32
			83	154	83	33
			82	182	60	24
		5	79	110	73	31	30
			82	137	75	31
			104	168	91	29
		10	70	164	64	31	33
			67	138	53	27
			63	127	78	41
		20	75#	161	67	30	30
			74	116	67	30
			74	181	67	30
		30	72	56	76	35	28
			114	236	80	23
			96	238	72	25
		40	80#	108	107	45	35
			76	226	68	30
			74	178	68	31
Positive Control	Methyl Methane Sulfonate	5	47	33	501	358	367*
			39	23	466	398
			46	58	476	346

Nonactivation Trial: 4 Experiment Call: Equivocal
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	79	50	164	69	52
			84	141	117	46
			71#	105	135	63
			55	104	48	29
Test Chemical	Malathion	15	75	124	95	43	39
			73	115	70	32
			79	100	103	44
		20	60	41	89	50	50
			81	167	117	48
			72	99	110	51
		40	41	44	95	78	67
			51	75	81	53
			55	78	114	69
		60	78	36	107	46	82*
			65	20	114	59
			34	7	143	140
Positive Control	Methyl Methane Sulfonate	5	57	58	570	336	429*
			24	18	396	542
			43	19	520	408

Nonactivation Trial: 5 Experiment Call: Negative
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	104	107	143	46	38
			100	96	87	29
			116	132	92	27
			98	65	147	50
Test Chemical	Malathion	2.5	114	121	88	26	40
			101	136	105	35
			79	81	140	59
		5	84	135	137	55	44
			117	177	87	25
			85	101	137	54
		7.5	87	126	129	49	42
			104	112	111	36
			65	114	78	40
		10	116	139	119	34	36
			104	123	100	32
			113#	127	138	41
		15	73	91	115	53	41
			107	121	116	36
			110	91	112	34
		20					49
			74	9	92	41
			69	35	117	56
		30


Positive Control	Methyl Methane Sulfonate	5	65	59	698	357	328*
Positive Control			60	37	539	299	328*

Nonactivation Trial: 6 Experiment Call: Negative
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	97	125	159	55	51
			103#	101	112	36
			121r	100	154	42
			113	74	213	63
Test Chemical	Malathion	2.5	119	94	198	56	49
			116	80	153	44
			97	73	137	47
		5	113	71	166	49	48
			123r	66	178	48
			93	66	133	48
		10	118	74	165	47	44
			108	73	124	38
			115	69	163	47
		15	113	60	198	58	52
			101	48	135	44
			95	34	148	52
		20	105	48	148	47	52
			97	52	158	54
			103	21	171	55
Positive Control	Methyl Methane Sulfonate	5	96	48	1221	425	461*
			100	50	1382	462
			71	41	1054	496

Induced S9 Trial: 1 Experiment Call: Negative
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	93	89	147	53	60
			85	106	91	36
			98	121	197	67
			63	85	157	83
Test Chemical	Malathion	10	103#	157	165	54	56
			104	163	184	59
			110	144	180	54
		20	118	180	177	50	50
			96	160	140	49
			99	135	150	51
		30	73	77	154	70	77
			102#	115	277	91
			95	106	196	69
		40	73	73	78	36	46
			59#	76	100	57
			111	117	155	47
		60	84	24	84	33	38
			74	21	113	51
			55	18	49	30
Positive Control	3-Methylcholanthrene	2.5					508*
			65	42	755	388
			34#	20	640	627

Induced S9 Trial: 2 Experiment Call: Negative
		Conc. ug/mL	Cloning Efficiency	Relative Total Growth	Mutant Colonies	Mutant Frequency	Avg Mutant Frequency
Vehicle Control	Ethanol	0	95	104	188	66	76
			93#	113	235	84
			94#	84	246	87
			83#	100	170	69
Test Chemical	Malathion	5	78	102	135	58	49
			79	81	83	35
			82	89	134	54
		10	95	98	119	42	74
			46	39	185	135
			87	105	120	46
		20	80	84	223	93	75
			120r	57	166	46
			110	94	191	58
		30	113	26	258	76	71
			109	21	213	65

		40


Positive Control	3-Methylcholanthrene	2.5	47	17	1114	790	614*
			78	35	1095	470
			51#	17	896	582

Footnotes:
Asterisks(*) indicate significant responses.
r = rejected value due to quality control criteria
# = reduced sample size because of the loss of one culture dish due to contamination