We monitored the exposure of hairdressers to oxidative hair dyes for 6 working days under controlled conditions. Eighteen professional hairdressers (3/day) coloured hairdresser's training heads bearing natural human hair (hair length: approximately 30 cm) for 6 h/working day with a dark-shade oxidative hair dye containing 2% [14C]-para-phenylenediamine (PPD). Three separate phases of hair dyeing were monitored: (A) dye preparation/hair dyeing, (B) rinsing/shampooing/conditioning and (C) cutting/drying/styling. Ambient air and personal monitoring samples (vapours and particles), nasal and hand rinses were collected during all study phases. Urine (pre-exposure, quantitative samples for the 0-12, 12-24, 24-48 h periods after start of exposure) and blood samples (blank, 4, 8 or 24 h) were collected from all exposed subjects. Radioactivity was determined in all biological samples and study materials, tools and washing liquids, and a [14C]-mass balance was performed daily. No adverse events were noted during the study. Waste, equipment, gloves and coveralls contained 0.41 ± 0.16%, dye mixing bowls 2.88 ± 0.54%, hair wash 45.47 ± 2.95%, hair + scalp 53.46 ± 4.06% of the applied radioactivity, respectively. Plasma levels were below the limit of quantification (≤10 ng PPDeq/mL). Total urinary 0-48 h excretion of [14C] levels ranged from a total of <2-18 μg PPDeq and was similar in subjects exposed during the different phases of hair dyeing. Minimal air levels at or slightly above the limit of quantification were found in a few personal air monitoring samples during the phases of hair dyeing and hair cutting, but not during the rinsing phase. Air area monitoring samples or nasal rinses contained no measurable radioactivity. Hand residues ranged from 0.006 to 0.15 μg PPDeq/cm2, and were found predominantly after the cutting/drying phase. The mean mass balance of [14C] across the six study days was 102.50 ± 2.20%. Overall, the mean, total systemic exposure of hairdressers to oxidative hair dyes during a working day including 6 hair dyeing processes was estimated to be <0.36 μg PPDeq/kg body weight/working day. Our results suggest that (a) current safety precautions for the handling of hair dyes offer sufficient protection against local and systemic exposure and (b) professional exposure to oxidative hair dyes does not pose a risk to human health. © 2006 Elsevier Ltd. All rights reserved.