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A total of eight aquatic toxicity studies were performed with CAS# 756-13-8.  All acknowledged the hydrolytic instability of CAS# 756-13-8 under the test conditions and expressed results in terms of the concentration of its water-soluble hydrolysis product pentafluoropropionic acid (CAS# 422-64-0; perfluoropropionic acid; PFPA).  Therefore all equated the effects due to CAS# 756-13-8 with the equivalent mass of PFPA.  Seven of these studies were performed by dissolving CAS# 756-13-8 in water and testing the toxicity of the resulting solution, while one examined the toxicity of PFPA directly.  The results are summarized in the Table (below).

 

All studies were performed according to accepted international guidelines for testing of chemical toxicity to algae, fish, and daphnia, and were in compliance with OECD GLP standards.  Studies with Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Navicula pelliculosa were performed in accordance with OECD Guideline 201 (Alga, Growth Inhibition Test).  Testing in Lemna gibba was performed following EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II).  Toxicity in the Water flea (Daphnia magna) was measured using OECD Guideline 202 (Daphnia sp. Acute Immobilization Test).  The 96-hr LC50 for Pimephales promelas was determined following OECD Guideline 203 (Fish, Acute Toxicity Test), while toxicity in Oryzias latipes was determined under the Japanese guideline JIS K 0102-1998-71, “Testing methods for industrial waste water, Acute toxicity test with fish,” as a preliminary study to the determination of the bioconcentration of CAS# 756-13-8 / PFPA in fish.

 

These tests yielded time-appropriate EC50/LC50 values ranging from ~6.8 mg/L to >1080 mg/L for aquatic organisms.  Four were assigned Klimish rankings of 1 (reliable without restriction), three were assigned rankings of 2 (reliable with restrictions), and one was assigned a ranking of 3 (not reliable).

 

Of note, two studies were performed measuring average specific growth rate in the green algae Pseudokirchneriella subcapitata (formerly Selanastrum capricornutum).  One study examined the toxicity of PFPA generated from CAS# 756-13-8 in a separate vessel and added to the test solutions, while the other added CAS# 756-13-8 directly to the test solutions.  The 96-h EC50 values from the two studies were 10.6 mg/L and > 6.78 mg/L respectively.  Using data from these same two studies, 96-h NOEC values were determined to be 3.71 and 3.47 mg/L, again, respectively.  The geometric mean of the EC50 values was used to calculate the PNEC for CAS# 756-13-8 which was used in conjunction with the environmental distribution to determine the risk characterization ratio for CAS# 756-13-8 / PFPA.

Aquatic Toxicity Studies on CAS# 756-13-8 and its hydrolysis product PFPA

Nominal test substance

Test substance

Class of organism

Test organism

Study purpose

End points (expressed as concentration of PFPA)

Analysis of test substance

Klimisch

PFPA from CAS# 756-13-8

PFPA

algae & freshwater plants (green algae)

Pseudo-kirchneriella subcapitata

key

Average specific growth rate:
EC50(96h) = 10.6 mg/L
NOEC(96h) = 3.71 mg/L

Cell count:
EC50(96h) = 5.37 mg/L
NOEC(96h) = 1.57 mg/L

Analyzed

1

CAS# 756-13-8

PFPA

algae & freshwater plants (green algae)

Pseudo-kirchneriella subcapitata

key

Average specific growth rate:
EC50(72&96h) > 6.78 mg/L
NOEC(96h) = 3.47 mg/L

Analyzed

2

CAS# 756-13-8

PFPA

algae & freshwater plants (blue-green algae)

Anabaena flos-aquae

supporting

Average specific growth rate:
EC50(72&96) > 86.6 mg/L
NOEC (96h) = 44.0 mg/L

Analyzed

3

CAS# 756-13-8

PFPA

algae & freshwater plants (diatom)

Navicula pelliculosa

supporting

Average specific growth rate:
EC50(72&96h) > 14.2 mg/L
NOEC(72&96h) = 14.2 mg/L

Analyzed

2

CAS# 756-13-8

PFPA

algae & freshwater plants (green plant)

Lemna gibba

key

EC50 (7d) > 17.7 mg/L
NOEC (7d) Not calculated

Analyzed

1

PFPA from CAS# 756-13-8

PFPA

crustacean

Daphnia magna

key

EC50(48h) > 1080 mg/L
NOEC - not determined

Analyzed

1

PFPA from CAS# 756-13-8

PFPA

fish

Pimephales promelas

key

LC50(96h) > 1070 mg/L
NOEC(96h) = 1070 mg/L

Analyzed

1

PFPA

PFPA

fish

Oryzias latipes

supporting

LC50(96h) = 408 mg/L
NOEC(96h) = 333 mg/L
(NOEC estimated by author of RSS; not estimated in report from testing organization

Nominal

2