Dermal irritancy assessment of microbial toxins and pesticidal contaminants found in recreational water using two- and three-dimensional human skin models.

Abstract

Purpose: Dermal exposure to freshwaters contaminated with pesticides and microbial toxins may result in toxicity. This study assessed the in vitro dermal irritancy of selected pesticides and microbial toxins using two- (2D) and three-dimensional (3D) human skin models.

Materials and methods: The 2D model was normal human keratinocytes. The 3D model was EpiDerm, derived from normal human keratinocytes that forms a multi-layered differentiated human epidermal model. Pesticides included dimethipin, α-1,2,3,4,5,6-hexachlorocylohexane, oxyfluorfen, permethrin, profenofos, and tribufos. Toxins included cylindrospermopsin and microcystin-LA, -LR, and -RR. Exposure to contaminants was either 1 or 24 h. Viability was assessed by the MTT assay. Results were determined relative to negative control.

Results: Significant effects in viability were observed in both models and time points. The greatest significant decrease in viability in the 2D model was tribufos at 1 h (23%) and cylindrospermopsin (37%) at 24 h. In the 3D model, the greatest significant decrease was microcystin-LA (16%) at 1 h and microcystin-RR (32%) at 24 h.

Conclusion: Several microbial toxins and pesticides were cytotoxic in both models and time points. However, no contaminant tested in the 3D model for 1 h was > 50% cytotoxic, which would categorize a chemical as a dermal irritant (Organisation for Economic Cooperation and Development Test Guideline 439 for skin irritation). The 24 h exposure time point had a greater number of cytotoxic contaminants in both models, particularly the 2D model. Screening potential irritants in the 2D model for 24 h may prioritize chemicals for further assessment in the 3D model.