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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The EC50 is the value from the OECD Guideline 201 72-hour Selenastrum capricornutum assay conducted in accordance with GLP by Weytjens and Wils (1991) on 3-methylpyridine.  This EC50 was the key value for short-term toxicity to aquatic algae for all chemicals in the category (i.e., pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine).  The 72-hour EC50 of 244.6 mg 2-methylpyridine/L (nominal concentration) in Desmodesmus subspicatus (nee Selenastrum capricornutum) reported by Eisentraeger is similar to the EC50 reported by Weytens and Wils (1991).

Key value for chemical safety assessment

EC50 for freshwater algae:
320 mg/L

Additional information

The point of departure for the derivation of the PNECaquaticwas the EC50 value from the 72-hour Selenastrum capricornutum (aquatic alga) assay and the EC50 value from the 48-hour Daphnia magna (aquatic invertebrate) conducted by Weytjens and Wils (1991) on 3-methylpyridine; these two EC50 values (which were equivalent) represented the lowest of the short-term toxicity values from the key study for each of three trophic levels (fish, aquatic invertebrates and aquatic algae), and were selected as the point of departure for the derivation of the PNECaquatic for the chemical category including pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine. 

2-Methylpyridine (alpha-picoline, CAS 109-06-8) is a member of a category with is utilized for “read-across” to fill data gaps and for risk assessment for hazard identification. The category of pyridine and alkyl pyridine derivatives is comprised of pyridine (CAS 110 -86 -1), 2-methylpyridine (CAS 109-06-8), 3-methylpyridine (CAS 108-99-6) and 4-methylpyridine (CAS 108-89-4). The foundation of the category is a common functional group (the pyridine unsaturated ring structure) and similar physico-chemical properties, environmental fate and toxicity, and mammalian toxicity. Similar ecotoxicological and environmental fate properties derive from physico-chemical parameters and common pathways of metabolism and elimination among all members of the category. Three of four members of this category have harmonized classification and labelling. Read-across for non-harmonized endpoints is adequate for risk assessment purposes.