Predictive testing of metalworking fluids: a comparison of 2 cumulative human irritation models and correlation with...

Metalworking fluids (MWF) have been reported as being an important cause of irritant contact dermatitis in metal workers. Our purpose was to determine whether the irritancy of different MWF assessed by 2 different types of predictive human in vivo tests could be compared with epidemiological data. 3 water-based MWF were tested in the same panel of subjects. Reactions were assessed by a visual score (VS), evaporimetry to evaluate the transepidermal water loss (TEWL) and chromametry to quantify erythema. Test 1: MWF were applied with Finn Chambers on the volunteers' mid-back, removed after 1 day of exposure, and reapplied for a further 2 days. Test 2: Cumulative irritant contact dermatitis was induced using a repetitive irritation test for 2 weeks (omitting weekends) for 6 h per day. We observed an increase in VS, TEWL, and erythema for all MWF, with the same irritancy ranking in both test models. Differentiation of the substances was better in the D1/D3 test. The experimental results partially correlated with the epidemiological data. Considering the shorter application time and the better discrimination of irritancy, we prefer the D1/D3 model as a predictive test of MWF irritancy. Our results might aid development of a standardized test to reduce cumulative skin irritation in metal workers.