A Family of Water-Immiscible, Dipolar Aprotic, Diamide Solvents from Succinic Acid

Three dipolar aprotic solvents were designed to possess high dipolarity and low toxicity: N,N,N',N'-tetrabutylsuccindiamide (TBSA), N,N'-diethyl-N,N'-dibutylsuccindiamide (EBSA), and N,N'-dimethyl-N,N'-dibutylsuccindiamide (MBSA). They were synthesized catalytically by using a K60 silica catalyst in a solventless system. Their water immiscibility stands out as an unusual and useful property for dipolar aprotic solvents. They were tested in a model Heck reaction, metal-organic framework syntheses, and a selection of polymer solubility experiments in which their performances were found to be comparable to traditional solvents. Furthermore, MBSA was found to be suitable for the production of an industrially relevant membrane from polyethersulfone. An integrated approach involving in silico analysis based on available experimental information, prediction model outcomes and read across data, as well as a panel of in vitro reporter gene assays covering a broad range of toxicological endpoints was used to assess toxicity. These in silico and in vitro tests suggested no alarming indications of toxicity in the new solvents.

A TTC threshold for acute oral exposure to non-genotoxic substances

To derive an acute TTC threshold, the correlation between Allowable Daily Intakes (ADIs, chronic values) and Acute Reference Doses (ARfDs) of pesticides evaluated in the EU was investigated and their distributions were compared. The correlation between ARfDs and ADIs was significant (p = 0.01), but weak (r(2) = 0.051). Consequently, using this approach to derive acute TTC values does not seem valid. Therefore, the distributions of ARfDs and ADIs were compared directly, in order to extrapolate from chronic to acute TTC values. This comparison made for the combined Cramer structural class II and III pesticides showed a ratio ARfD/ADI of approximately 3 at the fifth percentile of the distributions. Based on these results, it is justified to propose a TTC for acute effects for Cramer III substances by multiplying the Cramer class III TTC threshold of 90 μg/person/day with a factor 3. This leads to an acute TTC threshold based on the Munro dataset for Cramer class III substances of 270 μg/person/day.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants in a grouping context

Previously we showed a battery consisting of CALUX transcriptional activation assays, the ReProGlo assay, and the embryonic stem cell test, and zebrafish embryotoxicity assay as 'apical' tests to correctly predict developmental toxicity for 11 out of 12 compounds, and to explain the one false negative [7]. Here we report on applying this battery within the context of grouping and read across, put forward as a potential tool to fill data gaps and avoid animal testing, to distinguish in vivo non- or weak developmental toxicants from potent developmental toxicants within groups of structural analogs. The battery correctly distinguished 2-methylhexanoic acid, monomethyl phthalate, and monobutyltin trichloride as non- or weak developmental toxicants from structurally related developmental toxicants valproic acid, mono-ethylhexyl phthalate, and tributyltin chloride, respectively, and, therefore, holds promise as a biological verification model in grouping and read across approaches. The relevance of toxicokinetic information is indicated.

Derivation of the minimal magnitude of the Critical Effect Size for continuous toxicological parameters from within-animal variation in control group data

Assuming that temporal fluctuations in physiological parameters (e.g. haematology, biochemistry) in individual healthy non-exposed animals are non-adverse, the minimal magnitude of the Critical Effect Size (CES) for a number of continuous parameters of toxicity studies was derived. A total of 36 studies (19 pharmaceutical preclinical studies in dogs and 17 chemical risk assessment studies in rats) were analysed to determine within-animal variation in their control groups. Minimal CES-values were derived for each group of studies, differentiating where necessary between strains and sexes, using the 2.5 percentile (lower limit) and/or 97.5 percentile (upper limit) of the distribution of the within-animal variation around the mean of each parameter. We concluded that minimal CES-values for continuous clinical chemistry and haematology parameters should be established separately per species, strain, sex and study duration investigated. Grouping of minimal CES-values, leading to more or less "general" values, seems possible for those parameters that are subject to tight homeostatic control and consequently show little within-animal variation. Nearly a quarter of the proposed CES-values is 5%, nearly a quarter range from 6% to 10%, a quarter is 15% or 20%, and nearly 30% of the proposed values is 20% of the mean of the control animals.

Effects of single and repeated exposure to biocidal active substances on the barrier function of the skin in vitro

The dermal route of exposure is important in worker exposure to biocidal products. Many biocidal active substances which are used on a daily basis may decrease the barrier function of the skin to a larger extent than current risk assessment practice addresses, due to possible skin effects of repeated exposure. The influence of repeated and single exposure to representative biocidal active substances on the skin barrier was investigated in vitro. The biocidal active substances selected were alkyldimethylbenzylammonium chloride (ADBAC), boric acid, deltamethrin, dimethyldidecylammonium chloride (DDAC), formaldehyde, permethrin, piperonyl butoxide, sodium bromide, and tebuconazole. Of these nine compounds, only the quaternary ammonium chlorides ADBAC and DDAC had a clear and consistent influence on skin permeability of the marker compounds tritiated water and [(14)C]propoxur. For these compounds, repeated exposure increased skin permeability more than single exposure. At high concentrations the difference between single and repeated exposure was quantitatively significant: repeated exposure to 300 mg/L ADBAC increased skin permeability two to threefold in comparison to single exposure. Therefore, single and repeated exposure to specific biocidal products may significantly increase skin permeability, especially when used undiluted.