title: Effect of test concentration in the ready biodegradability test for chemical substances: Improvement of OECD test guideline 301C.
abstract: In Japan, understanding the environmental persistence of chemicals is very important for risk assessment, and ready biodegradability tests are mainly conducted according to the Organisation for Economic Co-operation and Development test guideline 301C. However, the highest test concentration specified in test guideline 301C, 100 mg/L, may cause microbial toxicity and incomplete biodegradation. The authors performed test guideline 301C tests at test concentrations of 30 mg/L for 13 substances that were readily biodegradable in ready biodegradability tests but not in test guideline 301C tests. Of the 5 substances with potential to cause microbial toxicity at 100 mg/L, the percentage of biodegradation of sodium dimethyldithiocarbamate, 4-chloro-3-cresol (CC), thymol (THY), and p-tert-butyl-α-methylbenzenepropionaldehyde measured by biochemical oxygen demand (BOD) increased in the test guideline 301C test at 30 mg/L, suggesting a reduction in toxicity effects. Furthermore, CC and THY met the criteria for ready biodegradability, which are more than 60% of biodegradation by BOD and a 10-d window. Of the 8 substances with a low potential for causing microbial toxicity at 100 mg/L, the percentage of biodegradation of only 2-(diethylamino)ethanol increased in the test guideline 301C test at 30 mg/L. Employing a lower test concentration in the standard test guideline 301C test will contribute to improvement of consistency between results of a test guideline 301C test and other ready biodegradability tests.
authors.affiliation: Chemicals Evaluation and Research Institute, Kurume, Fukuoka, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Nabeoka
authors.affiliation: Chemicals Evaluation and Research Institute, Kurume, Fukuoka, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Taruki
authors.affiliation: Chemicals Evaluation and Research Institute, Kurume, Fukuoka, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Kayashima
authors.affiliation: Chemicals Evaluation and Research Institute, Kurume, Fukuoka, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Faculty of Environment and Information Sciences, Yokohama National University, Yokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kameya
mesh_terms: D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity; D007564:Japan; D066150:Organisation for Economic Co-Operation and Development; D012722:Sewage / Q000032:analysis; D017408:Guidelines as Topic
chemical_list: D004785:Environmental Pollutants; D012722:Sewage
keywords: Microbial toxicity; OECD test guideline 301C; Persistence; Ready biodegradability