Acute-to-chronic extrapolation is an important approach to predict acceptable no-effect levels from acute data which has some uncertainties, but is valuable for risk assessment of chemical substances. With regard to the still limited and heterogenic data of chronic fish tests, conclusions on aquatic hazard estimation need to be checked and the question arises whether the chronic toxicity to fish can be adequately derived from acute data. A comprehensive dataset including ecotoxicological studies of 203 substances was used to investigate acute-to-chronic ratios (ACR) for both fish and Daphnia. To address potential uncertainty parameters of the approach, the influence of the octanol–water partition coefficient Kow, the mode of action, and the acute toxicity levels on the ACR was evaluated. For industrial chemicals, median ACRs of 12.0 for fish and 8.8 for Daphnia and 90th percentiles of 68.0 and 50.2, respectively, were determined. The ACR for the most sensitive aquatic trophic level (ACRaqu) is derived by comparing the lowest acute and chronic effect value of Daphnia and fish. The median ACRaqu was 9.9, and the 90th percentile was determined to 58.5. The influence of the Kow on the ACR value was analysed and a correlation could not be confirmed. Non-polar narcosis was associated with a lower ACR, whereas polar narcosis was associated with an increased ACR. The result suggests that an acute-to-chronic extrapolation factor of 100 is protective for more than 90 % of the chemicals. Polar narcosis may represent a predictor for an increased ACR and an increased uncertainty of the approach. The result further suggests that a high Kow is probably not associated with increased ACRs and does not necessarily represent a determinant for chronic toxicity testing within this context.

Products containing biocides are used for a variety of purposes in the home environment. To assess potential health risks, data on products containing biocides were gathered by means of a market survey, exposures were estimated using a worst case scenario approach (screening), the hazard of the active components were evaluated, and a preliminary risk assessment was conducted.

Synthetic polymers are chemicals of emerging concern for the environment, which is mainly attributed to their persistence in environmental compartments. On the other hand, polymers exist in nature as well. They are regarded of no concern for the environment. The present article focusses on the environmental fate of natural polymers and the implications on the persistence assessment for synthetic polymers. Natural polymers vary widely in structure, function, and properties. Crystallinity, wettability and surface area are important influencing factors on the (bio)degradation kinetics. Chemical and enzymatic hydrolysis is the most important process for the degradation of natural polymers, which for particulate material takes place either by bulk or surface erosion. Some natural polymers are degraded rapidly, but in other cases, degradation of natural polymers takes very long until complete mineralization. These differences in biodegradability are a result of evolution as they have to fulfil specific functions in nature which might require a certain persistency. Consequently, many natural polymers would have to be considered persistent or very persistent (P or vP) based on the available studies using the standard assessment approach. At the same time, they are considered no concern to the environment for good reasons. The analysis emphasizes that mineralization alone is not a resilient persistence endpoint for polymers. This needs to be recognized when assessing synthetic polymers, many of which would fulfil the existing P/vP criteria as well. For such synthetic polymers, it would be important to establish meaningful endpoints and polymer specific criteria to enable an adequate persistence assessment using a weight-of-evidence approach.