Formulation Toxicity

There was considerable variation in the relative toxicity of the fire-control chemicals to rainbow trout; the 96-h LC50 values ranged from 12.2 to 1,141 mg/L (Table 1). Except for Pyrocap B-136, the foam concentrates were more toxic to rainbow trout than the fire retardants, and the magnitude of difference in toxicity ranged from 4- to 94-fold.

Among the fire retardants, the two Fire-Trol formulations were similar in their toxicity to rainbow trout, and both formulations were less toxic than Phos-Chek 259F (Table 1). For each fire retardant, all of the mortality occurred within the first 24 h of exposure (24-h LC50s = 96-h LC50s). Consequently, the 96-h LC50s approximated the incipient LC50 for each formulation (Rand and Petrocelli 1985).

The rank order of toxicity for the foam concentrates from most toxic to least toxic was as follows: FireFoam 103B = FireFoam 104 > ForExpan S > Fire Quench > Pyrocap B-136 (Table 1). For each foam concentrate, most of the mortalities occurred during the first 24 h of exposure and the 96-h LC50s were not significantly different from the 24-h LC50s. Moreover, no mortalities occurred after 72 h in any of the test solutions, except for FireFoam 103B (i.e., 72-h LC50 = 96-h LC50). These results indicated that acute lethality in rainbow trout exposed to each foam had ceased during the test period and that the 96-h LC50s approximated the incipient LC50 for each chemical (Rand and Petrocelli 1985).

TABLE 1.--Acute toxicity (mg/L)a of eight fire-control chemicals to juvenile rainbow trout in soft water at 12°C; LC50 = concentration lethal to 50% of test organisms.
Chemical	LC50 (95% confidence interval) at:				NAECb
	24 h	48 h	72 h	96 h
Fire Retardants
Fire-Trol	942	942	942	942	470
LCA-F	(753-1,157)	(753-1,157)	(753-1,157)	(753-1,157)
Fire-Trol	1,141	1,141	1,141	1,141	780
LCM-R	(933-1,445)	(933-1,445)	(933-1,445)	(933-1,445)
Phos-Chek	168	168	168	168	78
259F	(136-207)	(136-207)	(136-207)	(136-207)
Foam concentrates
FireFoam 103B	15.6	13.0	13.0	12.2	6.0
	(12.7-20.2)	(10.0-17.0)c	(10.0-17.0)c	(9.6-15.1)
FireFoam 104	20.4	13.0	13.0	13.0	10.0
	(16.4-25.0)	(10.0-17.0)c	(10.0-17.0)c	(10.0-17.0)c
Fire Quench	50.6	43.2	39.0	39.0	28.0
	(44.7-58.5)	(35.2-55.5)	(31.6-48.9)	(31.6-48.9)
ForExpan S	31.9	28.7	21.8	21.8	17.0
	(28.0-47.0)c	(24.8-33.6)	(17.0-28.0)c	(17.0-28.0)c
Pyrocap B-136	193	170	156	156	100
	(153-235)	(138-225)	(127-202)	(127-202)
aBased on nominal concentrations of the formulation. bNAEC = no acute effect concentration; highest concentration with 0% mortality at 96 h. cNo partial kills; 95% confidence intervals: lower limit = highest concentration with 0% mortality, and upper limit = lowest concentration with 100% mortality.

Reference Chemicals

Measured concentrations of TA-N and NO₂-N in test solutions of ammonia and nitrite at 96 h were within 82-86% and 79-89%, respectively, of initial values. Conversely, measured NO₃-N concentrations in nitrate test solutions at 96 h were about 49-91% higher than those at test initiation.

Ammonia expressed as NH₃-N was about six times more toxic than nitrite and about 13,300 times more toxic than nitrate (Table 2). The time course of toxicity varied among the three nitrogenous chemicals. For ammonia, all of the mortalities occurred within the first 24 h of exposure. For nitrate, no mortality occurred after 72 h and the 24-h LC50 was not significantly different from the 96-h LC50, despite the increase in NO₃-N concentrations from 0 to 96 h. For nitrite, the onset of acute toxicity occurred after 24 h of exposure and nitrite toxicity increased with exposure duration, indicating that acute lethality in rainbow trout would probably have continued to occur after 96 h of exposure.

Linear alkylbenzene sulfonate was about five times more toxic to rainbow trout than SDS (Table 2). The toxicity of LAS to rainbow trout did not increase significantly after 48 h, which indicated that the 96-h LC50 approximated the incipient LC50. The toxicity of SDS to rainbow trout increased significantly with exposure duration, which indicated that acute lethality would probably have continued to occur after 96 h.

TABLE 2.--Acute toxicity (mg/L)a of reference chemicals to juvenile rainbow trout in soft water at 12oC; LC50 = concentration lethal to 50% of test organisms.
Chemical	LC50 (95% confidence interval) at:				NAECb
	24 h	48 h	72 h	96 h
Nitrogenous chemicals
Ammonium chloride
Total ammonia (as N)	112	112	112	112	57
	(90-138)	(90-138)	(90-138)	(90-138)
Un-ionized ammonia (as N)	0.125	0.125	0.125	0.125	0.065
	(0.094-0.163)	(0.094-0.163)	(0.094-0.163)	(0.094-0.163)
Sodium nitrite (as NO2-N)	>2.37	1.45	0.90	0.79	0.54
		(1.16-1.98)	(0.74-1.18)	(0.65-1.00)
Sodium nitrate (as NO3-N)	1,811	1,811	1,658	1,658	720
	(1,487-2,295)	(1,487-2,295)	(1,355-2,063)	(1,355-2,063)
Anionic surfectantsc
Linear alkylbenzene sulfonate	8.1	5.4	5.0	5.0	3.8
	(6.6-9.8)d	(4.4-6.9)	(3.8-6.6)d	(3.8-6.6)d
Sodium dodecyl sulfate	58.1	41.2	41.2	24.9	19.5
	(50.5-68.4)	(31.7-53.5)d	(31.7-53.5)d	(19.5-31.7)d
aBased on measured concentrations. bNAEC = no acute effect concentration; highest concentration with 0% mortality at 96 h. cMeasured concentrations of anionic surfectant calculated as linear alkylbenzene sulfonate, molecular weight 342. dNo partial kills; 95% confidence interval: lower limit = highest concentration with 0% mortality, and upper limit = lowest concentration with 100% mortality.

Nitrogenous Chemicals in Fire Retardants

Based on measured concentrations at 0 h, the mean percentage of ammonia (as TA-N) in Phos-Chek 259F (22.9%) was about two times higher than that in the Fire-Trol formulations (10.8-11.5%, Table 3). The estimated TA-N concentration at the 96-h LC50 of Phos-Chek 259F was lower than those of the first two Fire-Trol formulations and of NH₄Cl (Table 2). The estimated NH₃-N concentration at the 96-h LC50 of Fire-Trol LCA-F was lower than those of Fire-Trol LCM-R and NH₄Cl. Reductions in measured TA-N concentrations in test solutions of the three fire retardants from 0 to 96 h were similar to those of NH₄Cl and ranged from 9 to 13% for Fire-Trol LCA-F, from 8 to 16% for Fire-Trol LCM-R, and from 16 to 22% for Phos-Chek 259F.

Measured concentrations of NO₃-N in test solutions of the three fire retardants and NH₄Cl at 0 and 96 h were less than or equal to 0.9 mg/L, and in most of the solutions, NO₃-N concentrations were below the detection limit (0.1 mg/L). Concentrations of NO₂-N in test solutions of the fire retardants and NH₄Cl at 0 and 96 h were less than or equal to 0.02 mg/L. These results indicated that ammonia was not oxidized to nitrite or nitrate under these test conditions.

TABLE 3.--Summary of measured total ammonia (TA, mg/L as N) concentrations and estimated un-ionized ammonia (NH3, mg/L as N) concentrations in solutions of fire retardants tested with rainbow trout; LC50 = concentration lethal to 50% of test organisms.
Chemical	Percent TA in chemicala	pH Rangeb	Concentration at the 96-h LC50c (95% confidence interval) for:
			TA	NH3
Fire-Trol LCA-F	11.5	6.32-6.41	107	0.051*
	(11.2-11.9)		(84-133)	(0.037-0.069)
Fire-Trol LCM-R	10.8	6.54-6.61	124	0.101
	(10.3-11.2)		(101-158)	(0.078-0.136)
Phos-Chek 259F	22.9	6.91-6.99	39*	0.074
	(21.7-23.6)		(31-48)	(0.054-0.101)
aMean (and range) across all concentrations. bInitial pH of concentrations that bracketed the 96-h LC50. cValues with an asterisk are significantly different (P = 0.05) from the corresponding 96-h LC50 for ammonium chloride (see Table 2).

Anionic Surfactants in Foams

Based on measured concentrations of anionic surfactants in test solutions at 0 h, the percentage of anionic surfactant in the foams ranged from 11.1 to 22.3% (Table 4). The descending rank order of toxicity based on estimated concentrations of anionic surfactant at the 96-h LC50 of the foam concentrates and two reference surfactants was as follows: FireFoam 103B = FireFoam104 > Fire Quench = ForExpan S = LAS > Pyrocap B-136 > SDS (Tables 2, 4).

TABLE 4.--Summary of measured concentrations of anionic surfectant (mg/L)a in solutions of five foam concentrates tested with rainbow trout; LC50 = concentration lethal to 50% of test organisms.
Chemical	Anionic surfectant in chemicalb (%)	Concentration at the 96-h LC50c (95% confidence interval)
FireFoam 103B	22.3	2.3*
	(19.1-25.2)	(1.8-2.9)
FireFoam 104	19.7	2.8*
	(16.4-22.1)	(2.2-3.5)d
Fire Quench	11.1	4.4
	(9.7-13.5)	(4.0-4.9)
ForExpan S	22.3	4.6
	(20.7-23.3)	(3.6-5.8)d
Pyrocap B-136	12.6	13.5*
	(11.2-14.6)	(11.2-17.1)
aCalculated as linear alkylbenzene sulfonate, molecular weight 342. bMean (and range) across all concentrations. cValues with an asterisk are significantly different (P = 0.05) from the corresponding 96-h LC50 for linear alkylbenzene sulfonate (see Table 2). dNo partial kills; 95% confidence interval: lower limit = highest concentration with 0% mortality, and upper limit = lowest concentration with 100% mortality.