Ecotoxicity of paint mixtures: Comparison between measured and calculated toxicity

The aims of the current study were to test the validity of the concentration addition (CA) and independent action (IA) calculation methods for mixture toxicity as well as the REACH guidelines for mixture exposure scenarios for paint products. Based on ecotoxicity tests of nine anticorrosive paint mixtures and the nine substances that contributed to classification of the mixtures as hazardous for the aquatic environment, neither CA nor IA was found to be appropriate calculation methods, although CA calculations were conservative for half of the mixtures tested. The REACH mixture approach, based on “lead” substances, resulted in conservative predictions for three out of five mixtures and the “lead” substance corresponded to the substance contributing the most in the CA mixture calculations for four out of six mixtures. The use of paints as a matrix for toxicity testing required adaptation of test procedures, development of sample handling and chemical analysis methods.

► CA calculations of EL50Mix were conservative for half of the mixtures tested.
► Most IA calculations of toxic effects resulted in less toxicity than was observed.
► The DPD + approach in REACH led to conservative predictions for three of five mixtures.
► The curing process caused enhanced and decreased toxicity in different mixtures.
► Adaptations of test procedures and development of analytical methods were required.