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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

PTBA is not expected to be toxic to algae at the limit of solubility (0.710 µg/L) by readacross from category members FC-770 and PMM.  No toxicity was observed to P. subcapitata in OECD201 assays tested at the limit of media solubility.  These category member results are considered applicable to PTBA.

Key value for chemical safety assessment

Additional information

PTBA is the least water soluble member of the Perfluorinated Organic Chemicals, C5-C18 category. Because these substances exhibit similarity in their physicochemical properties and toxicological properties in mammals, and because available data indicates that parent molecules are not reactive toward biological molecules and cannot undergo bioactivation by normal enzymatic processes, they can be considered members of a chemical category. Data gaps for ecological toxicity can therefore be addressed by read-across and/or trend analysis between category members. Reliable OECD201 studies are available for algae toxicity of category members perfluoromethyl morpholine (PMM), and FC-770. In both cases, EC50s (72-h and 48-h, respectively) were in excess of the maximum achievable test substance concentrations. Analytically determined test substance concentrations are not reasonable to use for readacross since the solubilities of PMM and FC-770 are substantially higher than that of PTBA. Lack of toxicity at the limit of solubility is read across qualitatively to PTBA. The solubility of PTBA was determined to be 0.710 µg/L in organism-free Daphnia medium controls during the short-term toxicity test. This value is greater than the measured PTBA solubility in water (<0.06 µg/L) but less than the analytically determined concentrations in medium containing live daphnids. The organism-free medium solubility value is understood to be better representative of PTBA solubility in natural waters, and avoids potential impacts on the analytical result by the action of living organisms. Therefore, 0.710 µg/L is accepted as the basis for estimating the highest possible exposure concentration of PTBA in order to define the EC50.

Please see IUCLID section 13 for a matrix of aquatic toxicity data for members of the Perfluorinated Organic Chemicals C5-C18 category.