The aim of this work was to study the biological effects of four monoterpenes, i.e. alpha-pinene, beta-pinene, 3-carene and D-limonene present in the wastewater of a citrus transformation factory. The study was carried out by exposing V79 Chinese hamster cells to single terpene or to the mixture of four terpenes at concentrations corresponding to those in the wastewater evaluated by head space solid phase micro extraction and gas chromatography (HS-SPME-GC) analyses. Treatments with single or combined terpenes similarly affected cell vitality, but only the combined treatments induced the 6-thioguanine resistant mutants. Moreover the photocatalytic degradation of the four terpenes was successfully achieved with the photocatalyst TiO2 Degussa P25 in both the actual effluent and in synthetic solutions. (C) 2010 Elsevier B.V. All rights reserved.