USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

Acute Toxicity of Fire-Control Chemicals, Nitrogenous Chemicals, and Surfactants to Rainbow Trout

Results


There were no mortalities in any of the control treatments. Dissolved oxygen concentrations in all tests were maintained at greater than or equal to 73% saturation after 48 h and at greater than or equal to 57% saturation after 96 h. In tests with the foams, LAS, and SDS, the mean pH ranged from 7.46 to 7.53 at 0 h and from 6.62 to 6.80 at 96 h. For the fire retardants and nitrogenous chemicals, the mean pH values of test solutions at 0 and 96 h were as follows: 6.20 and 6.95 for Fire-Trol LCA-F; 6.52 and 7.26 for Fire-Trol LCM-R; 6.85 and 7.26 for Phos-Chek 259F; 6.75 and 6.92 for NH4Cl; 7.22 and 6.97 for NaNO3; 6.62 and 6.81 for NaNO2; and 6.82 and 6.88 for the controls. Mean (range) hardness and alkalinity of test solutions (excluding the fire retardants) after 24 h were 41 (39-44) mg/L as CaCO3 and 32 (30-38) mg/L as CaCO3. For the fire retardants, alkalinity varied directly with test concentration (adjusted r2 = 0.999, P = 0.003) and ranged from 39 to 469 mg/L as CaCO3.


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.


Previous Section -- Methods
Return to Contents
Next Section -- Discussion

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/fish/fchem/results.htm
Page Contact Information: Webmaster
Page Last Modified: Saturday, 02-Feb-2013 04:32:06 EST
Sioux Falls, SD [sdww55]