Electronic Supplementary Material (ESI) for Environmental Science: Processes & Impacts. This journal is © The Royal Society of Chemistry 2017 Electronic Supplementary Information

Classification of baseline toxicants for QSAR predictions to replace fish acute toxicity studies

Monika Nendza1*, Martin Müller2 and Andrea Wenzel2 1 Analytical Laboratory AL-Luhnstedt, Bahnhofstraße 1, 24816 Luhnstedt, Germany 2 Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany

S1. Additional information on the training set

Fish acute toxicity data for Pimephales promelas were taken from the EPA Fathead Minnow acute toxicity database (EPAFHM).1 The EPAFHM contains high quality data, obtained consistently with the same fish species in the same laboratory. Exclusion of inorganic compounds (n=1), organometallic compounds (n=3), organic salts and complexes (n=22), and compounds without an LC50 value (n=36) resulted in a dataset of 96h LC50 data [mmol/L] for 555 discrete organic compounds (447 baseline, 108 excess) 2 with a range in molecular weight from 32.0 to 488.6 g/mol and calculated log Kow from -4.15 to 7.43 (Table S1). Chemicals were grouped as either baseline or excess toxicants based on their experimental fish acute toxicity data relative to a log 3 Kow-dependent baseline QSAR for acute fish toxicities [96-h LC50 (Pimephales promelas): log 1/LC50 [mmol/L] = 0.79 log Kow - 1.35, where n = 147, r = 0.92, s = 0.40; n is the number of observations, r is the correlation coefficient and s is the standard deviation of the residuals]. The toxicity estimates were compared to the available experimental fish acute toxicity data. If calculated and experimental toxicity data agreed within a factor of 10, i.e. residuals (log 1/LC50 exp - log 1/LC50 calc) <1 log unit, chemicals were considered baseline toxicants. Excess toxicity as introduced by Lipnick4, 5 refers to enhanced effects of compounds relative to their baseline toxicity. Excess toxicity significantly, at least 10-times, exceeds the calculated baseline toxicity. Deviations larger than a factor of 10, i.e. residuals (log 1/LC50 exp - log 1/LC50 calc) >1 log unit, prompted assignment of excess toxicity. Note that excess toxicities are based on a formal comparison of the experimental and calculated numeric values and may be due to diverse MOA related to the chemical reactivities of the toxicants with biological targets.6

Table S1: Training set of fish acute toxicity data. Residuals CAS Compound log Kow LC50 [mg/L] (log 1/LC50 exp - log 1/LC50 calc) 100-01-6 p-Nitroaniline 1.47 125 0.23 100-02-7 p-Nitrophenol 1.91 44.8 0.33 100-10-7 p-Dimethylaminobenzaldehyde 1.89 45.7 0.37 100-25-4 1,4-Dinitrobenzene 1.63 0.709 2.44 10031-82-0 p-Ethoxybenzaldehyde 2.28 28.1 0.28 100-37-8 N,N-Diethylethanolamine 0.05 1780 0.13 100-41-4 Ethylbenzene 3.03 10.5 -0.04 100-46-9 Benzylamine 1.07 102 0.53 100-52-7 Benzaldehyde 1.71 9.87 1.03 100-61-8 N-Methylaniline 1.62 100 0.10 100-64-1 Cyclohexanone oxime 0.91 208 0.37 100-70-9 2-Cyanopyridine 0.35 726 0.23 100-71-0 2-Ethylpyridine 1.84 414 -0.69 100-79-8 Solketal 1.07 16700 -1.60 100-97-0 Hexamethylenetetramine (aliphatic) -4.15 49800 2.08 101-84-8 Phenyl ether 4.05 4 -0.22 102-27-2 N-Ethyl-m-toluidine 2.66 49.5 -0.31 102-69-2 Tripropylamine 2.99 50.9 -0.56 102-71-6 Triethanolamine -2.48 11800 1.41 10293-06-8 [1(R)-endo]-(+)-3-Bromocamphor 3.31 68.4 -0.74 103-05-9 Benzyl-tert-butanol 2.93 66.4 -0.57 103-76-4 1-(2-Hydroxyethyl)piperazine -1.56 6410 0.89 103-83-3 N,N-Dimethylbenzylamine 1.75 37.9 0.52 103-90-2 4-Acetamidophenol 0.27 814 0.41 104-13-2 4-Butylaniline 3.10 10.1 0.07 10453-86-8 Resmethrin 7.11 0.00616 0.47 104-76-7 2-Ethyl-1-hexanol 2.73 28.3 -0.14 104-88-1 4-Chlorobenzaldehyde 2.35 2.19 1.30 104-90-5 5-Ethyl-2-methylpyridine 2.39 81.1 -0.36 Residuals CAS Compound log Kow LC50 [mg/L] (log 1/LC50 exp - log 1/LC50 calc) 105-14-6 5-Diethylamino-2-pentanone 0.94 336 0.28 105-53-3 Diethyl malonate 0.90 14.7 1.68 105-67-9 2,4-Dimethylphenol 2.61 16.6 0.15 105-75