Current biodegradation screening
tests are not specifically designed
for persistence assessment of chemicals, often show high inter- and
intra-test variability, and often give false negative biodegradation
results. Based on previous studies and recommendations, an international
ring test involving 13 laboratories validated a new test method for
marine biodegradation with a focus on improving the reliability of
screening to determine the environmental degradation potential of
chemicals. The new method incorporated increased bacterial cell concentrations
to better represent the microbial diversity; a chemical is likely
to be exposed in the sampled environments and ran beyond 60 days,
which is the half-life threshold for chemical persistence in the marine
environment. The new test provided a more reliable and less variable
characterization of the biodegradation behavior of five reference
chemicals (sodium benzoate, triethanolamine, 4-nitrophenol, anionic
polyacrylamide, and pentachlorophenol), with respect to REACH and
OSPAR persistence thresholds, than the current OECD 306 test. The
proposed new method provides a cost-effective screening test for non-persistence
that could streamline chemical regulation and reduce the cost and
animal welfare implications of further higher tier testing.
The Organisation for Economic Co-operatoin and development (OECD) Guidelines for the Testing of Chemicals list 7 types of tests for determining the ready biodegradability of chemical compounds (301A-F and 310). The present study compares the biodegradation performance of test guideline 301C, which is applied in Japan's Chemical Substances Control Law, with the performance of the other 6 ready biodegradability tests (RBTs) listed in the guidelines. Test guideline 301C specifies use of activated sludge precultured with synthetic sewage containing glucose and peptone (301C sludge) as a test inoculum; in the other RBTs, however, activated sludge from wastewater treatment plants (WWTP sludge) is frequently employed. Analysis based on percentage of biodegradation and pass levels revealed that the biodegradation intensity of test guideline 301C is relatively weak compared with the intensities of RBTs using WWTP sludge, and the following chemical compounds are probably not biodegraded under test guideline 301C conditions: phosphorus compounds; secondary, tertiary, and quaternary amines; and branched quaternary carbon compounds. The relatively weak biodegradation intensity of test guideline 301C may be related to the markedly different activities of the 301C and WWTP sludges. These findings will be valuable for evaluating RBT data in relation to Japan's Chemical Substances Control Law.
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.
A resin-phase extraction method has been optimized for the trace determination of tin(II) by ETAAS. Tin(II) was extracted on a finely divided anion exchange resin as the complex with ammonium pyrrolidinedithiocarbamate (APDC). The resin was collected on a membrane filter and then dispersed in 1.00 ml of 1 mol l −1 nitric acid containing 100 μg of Pd(II) and 60 μg of Ni(II). The resulting resin suspension was subjected to GFAAS. The proposed method was applied to the determination of tin(II) in hydrochloric acid.
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