Investigations on the direct photodegradation of a fragrance ingredient for its persistence assessment in worldwide natural waters

Abstract

• The fragrance ingredient EMCP underwent rapid direct photodegradation with a short half-life of 1.3 h around summer noon time due to the high quantum yield of 0.294. • The estimated yearly average half-life of EMCP in a 3 meters deep water with the global average surface water [DOC] of 5 mg C/L is less than 19 days even at extreme latitudes. • EMCP is mostly non-persistent in countries of the largest economies, i.e. US, China, Japan, Australia and European countries, based regional persistence assessments of EMCP using the measured local [DOC] levels with the corresponding latitudes. A persistence assessment is required for the introduction of new chemicals to the market and is usually based on biodegradation data. This is the first time that a persistence assessment of a fragrance ingredient in worldwide aquatic environment was systematically conducted using photodegradation data while considering both the relevant average DOC levels and latitudes. A fragrance ingredient, 1-(5-ethyl-5-methylcyclohex-1-en-1-yl)pent-4-en-1-one ( EMCP ) was used as an example. First, EMCP ’s photodegradation kinetics and degradation products were studied in the laboratory using a recently reported workflow. EMCP was found to undergo rapid direct photodegradation in pure water with a validated high quantum yield of 0.294 and a half-life of 1.3 h around summer noon time. Formation of two cycloaddition products as the main volatile photoproducts and their further photodegradation were observed. Second, photodegradation half-lives of EMCP in worldwide natural waters were estimated using the state-of-the art methodology by considering variation of solar irradiance according to latitude and season, and the effect of light attenuation due to absorption by dissolved organic carbon (DOC) at water depth. The estimated yearly average half-life of EMCP in a 3 meters deep water with the global average surface water [DOC] of 5 mg C/L is less than 19 days even at extreme latitude of 70° in both northern and southern hemisphere. Finally, regional persistence assessments of EMCP were conducted for countries of the largest economies, by considering the measured local [DOC] levels with the corresponding latitudes. The results indicated that EMCP is mostly non-persistent in Europe, US, China, Japan and Australia, but persistent with an estimated half-life of 43 to 49 days in Central and Southern Finland waters with a high [DOC] of 12.5 to 15 mg C/L.