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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 89 - 92.2% (ThCO, ThO2) in 28 days (OECD 301 B, 301 F)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

No studies investigating the biodegradability of sodium methylparaben (CAS No. 5026-62-0) are available. Therefore, biodegradation data of the corresponding acid methylparaben (CAS No. 99-76-3) are used as read across.

This read across approach is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach as is explained within the analogue justification in section 13. Except for different cations (hydrogen vs. sodium) the anions of both the source and target substance have identical chemical structures. Since dissociation of the sodium salt under environmental conditions (pH 4 - 9) yields the same ionic species as the acidic form of the substance, this read across can be considered as justified.

For the analogue read across substance methylparaben, biodegradation data from four studies are available. Ready biodegradability data are reported in two studies and additional data for inherent and anaerobic biodegradability are reported in one study each. The key study was carried out according to OECD guideline 301 B under GLP (Noack, 2004). Domestic activated sludge was used as inoculum. The substance reached 89% degradation after an incubation time of 28 days. The supporting study on ready biodegradability was carried out according to OECD guideline 301 F (Madsen et al., 2001). No details on the source and amount of inoculum are given in the report. The substance attained 92.2% degradation within 28 days. Taken together, the substance can be assumed as readily biodegradable according to the strict OECD criteria.

In the supporting study on inherent biodegradability according to OECD guideline 302 B (Wellens, 1990), methylparaben was incubated with non-adapted industrial activated sludge. Based on DOC removal, methylparaben attained 100% degradation after a contact time of 6 days. In the supporting study on biodegradation under anaerobic conditions according to ISO 11734 (Madsen et al., 2001), methylparaben was incubated with digested sludge. Based on theoretical gas production, methylparaben reached a maximum of 40% degradation after 56 days.