Perchloric acid

Sediment toxicity

Description of key information

By analogy with sodium perchlorate, the chronic NOEC value of perchloric acid is 58.5 mg/L for emergence of midge when exposed via spiked water. This NOEC value is recalculated in concentration in dry sediment uqing the partition coefficient of the substance.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

467 mg/kg sediment dw

Additional information

No data on perchloric acid is available for this endpoint. However, three reliable studies are available for sodium perchlorate (Dean et al., 2004), which is used in a read-across approach (See the endpoint study summary "Aquatic toxicity" for the read-across justification). The studies were performed according to requirements of the U.S. EPA guidelines without GLP statement. The results are expressed in perchlorate moiety in order to be applicable for the derivation of the PNEC of perchloric acid.

 

 

The first study has been performed with midge (Chironomus tentans) to assess chronic toxicity using spiked water. The method presents similarities with the OECD Testing Guideline 219. The midges utilized were approximately 1-d posthatch at study initiation. The test was initiated with the addition of 12 midge larvae into 12 replicate test chambers, for a total of 144 midges per treatment. The artificial sediment consisted of 76% fine silica sand, 20% kaolinite clay, and 4% fine peat moss (passed through a 500-mm mesh sieve). The sediment was hydrated with water of approximately 43% of its dry weight, and calcium carbonate was added to the sediment to adjust its pH to between 6.5 and 7.0 before use. Four additional replicate test chambers were initiated with the addition of 12 midge larvae on day 10 to provide additional male midges during the reproduction evaluation portion of the study. An emergent trap covered each of the test replicates. An intermittent feeding system was used to deliver concentrated algae (i.e., a mixture ofSelenastrum capricornutumandAnkistrodesmus falcatus) to each test chamber during each diluter cycle. Nominal perchlorate exposure concentrations in the definitive test were 0 (controls), 62.5, 125, 250, 500, 1000 and 2,000 mg/L perchlorate ion.

Survival in the control and the sodium control over the 42-d exposure was 90 and 81%, respectively. In perchlorate treatments, survival was 87, 62, 24, 21, 4, and 0% in the 58.5, 118, 233, 489, 1020, and 2080 mg/L exposures. Most of the surviving larvae from exposure concentrations greater than 233 mg/L were discolored. However, this sublethal effect was not considered in the calculation of the EC50.

Adult midge emergence was first recorded after 21 d of exposure. Emergence totaled 89 and 28% in the control and sodium control, respectively, through day 42, when the exposure was terminated. Emergence in the perchlorate treatments ranged from 0 to 85%.

The mean individual ash-free dry weight of surviving larvae at day 20 was 1.6 and 0.55 mg/L in the control and sodium control, respectively, and 1.4, 1.4, 0.93, 0.48, and 0.40 in the 58.5, 118, 233, 489, and 1020 mg/L exposures, respectively.

The control and sodium control females produced egg masses with an average of 936 and 1792 eggs per egg mass, respectively. The mean number of eggs per egg mass was 918, 900 and 393 in the 58.5, 118 and 233 mg/L exposures, respectively. A single female emerged in the 1080 mg/L treatment but could not be paired.

The adult emergence was the most sensitive biological endpoint measured during the midge life-cycle exposure to perchlorate. The 42d-NOEC, LOEC, and EC50 for emergence were 58.5, 118, and 146 mg/L, respectively, with a 95% confidence interval of 134 to 159 mg/L for the EC50.

Even if not performed according to OECD Guideline 219, the method applied follows the same principle, therefore the fulfillment of the OECD validity criteria was checked by the applicant. All validity criteria cannot be assessed. The emergence in the sodium control was lower than 70% after 21 days of exposure (exactly 28%) but no information was provided at the end of the test. No information was mentioned on the time of emergence to adults midges from control vessels. The pH was comprised between 6 and 9 and the water temperature was maintained at 23 +/- 2°C but raw data were not available.

This study is considered reliable with restrictions and is selected as key study for the chronic 42d NOEC = 58.5 mg/L (emergence). In the ECHA guidance R7b, section R.7.8.11.3 "Concluding on suitability for use in Chemical Safety Assessment", it is stated that "If sediment tests are available in which the test substance was applied to the test system via spiking of the water phase, the effect values given in mg/l have to be converted into a sediment concentration (mg/kg) using the substance-specific partitioning coefficient or if available, measured sediment concentrations can be used." As no measurement in the sediment has been performed in this study, the partition coefficient should be used to derive a NOEC value in mg/kg of sediment.

Considering Ksusp_water is 1.99 (calculated with a koc value of 43.89) and the default value of bulk density of wet suspended matter (RHOsusp=1150), the NOEC can be converted as follows (equation R.10-2 of ECHA Guidance): NOEC = (1.99 / 1150) * 58.5 * 1000 = 101.6 mg/kg sediment in wwt. This value can be converted in dry weight: NOEC = 467 mg/kg sediment in dw.

The second study is an acute toxicity of Perchlorate to midge (Chironomus tentans). The method applied presents similarities with the OECD Testing Guideline 235 except that third instar organisms were tested instead of first instar as recommended by the OECD TG 235, therefore the sensitivity of this study may be less important than full OECD TG 235 compliant study.

The midges utilized were approximately 11-d posthatch at study initiation and were in the third instar. Twenty organisms per treatment level, in two replicates of 10 each, were exposed to sodium perchlorate 48 h. A thin layer of silica sand coated the bottom of the test chambers to provide a substrate for the midges. Nominal exposure concentrations were 0 (control), 625, 1250, 2500, 5000, and 10000 mg/L perchlorate ion.

Mean measured perchlorate concentrations ranged from 772 to 12700 mg/L (113–127% of the nominal concentrations). One midge (5%) was missing and considered to be dead in the control and in the 1000 mg/L equivalent sodium control, but no mortality was observed in the level 5 (10000 mg/L equivalent) sodium control. In the perchlorate treatments, mortality (missing midge were considered to be dead) was 5, 20, 15, 15, and 90% in the 772, 1545, 3045, 5640, and 12700 mg/L treatments, respectively.

The 48-h NOEC for C. tentans was 5640 mg/L, and the LOEC was 12700 mg/L. The 48-h EC50 was calculated to be 8100 mg/L, with a 95% confidence interval of 6600 to 10000 mg/L.

Even if not performed according to OECD Guideline 235, the method applied follows the same principle, therefore the fulfillment of the OECD validity criteria was checked by the applicant. All validity criteria cannot be assessed. In the controls less than 15% of effects were observed at the end of the test but no information was provided on the dissolved oxygen concentration. This study is considered reliable with restrictions.

This study is considered reliable with restrictions and is selected as key study for the acute 48h EC50 = 8100 mg/L (mortality). It shows that perchlorate has a low acute toxicity to sediment invertebrates.

 

The third study was performed according to requirements in the U.S. EPA guidelines (but not specific to the species tested) without GLP statement, to assess the acute toxicity of Perchlorate to adult oligochaete annelidsLumbriculus variegatus.

TwentyLumbriculus variegatusper treatment level, in two replicates of 10 each, were exposed to sodium perchlorate in 500 -ml glass jars with a screen collar for 96 h. Nominal exposure concentrations in the definitive test were 0 (control), 625, 1250, 2500, 5000, and 10000 mg/L perchlorate ion.

Mean measured perchlorate concentrations ranged from 470 to 10700 mg/L (75–115% of the nominal concentrations). Sublethal effects included discoloration and annular constrictions in the body walls, forming sausage-like links, at exposure concentrations of 470 mg/L and higher. Neither of these effects was immobilizing or appeared to lead to death, and the worms recovered from these effects in many cases, possibly by excising the segments posterior to the kink. No mortality was observed in the control or the sodium controls. One organism (5%) died in each of the 470, 1240, and 2500 mg/L treatments. All 20 (100%) organisms died in the 5760 and 10700 mg/L treatments. Based on mortality, the 96-h NOEC for L. variegatus was 2500 mg/L, the LOEC was 5760 mg/L, and the LC50 was 3710 mg/L, with a 95% confidence interval of 3550 to 3880 mg/L.

This study is well documented but no equivalent OECD Guideline is available. Therefore, this study has not been selected as key study.