Formaldehyde solutions in simulated sweat increase human melanoma but not normal human keratinocyte cells proliferation

Our skin is in close contact with clothes most of the time thus risking potentially noxious chemicals contact. One of the potentially harmful manufacturing by-products that can be released by textiles when sweating is formaldehyde, used as an anti-crease treatment. As it is known to be carcinogenic to humans and a potent skin sensitizer, the aim of this study was to investigate its effects on both normal human keratinocytes (HaCaT cells) and on a highly invasive malignant melanoma cell line (SK-MEL-28) in order to contribute to the definition of safety cut-off to be applied to the production processes. Formaldehyde concentrations below the commonly accepted limits (10–50 μM) were obtained by diluting formaldehyde in simulated sweat (UNI EN ISO 105-E04). The effects on cell proliferation were evaluated by cell counting, while ERK pathway activation was evaluated by western blot. Low concentrations of formaldehyde (10 μM) in both acidic and alkaline simulated sweat were able to increase malignant melanoma cell proliferation, while not affecting normal keratinocytes. Melanoma proliferation increase was greater in acidic (pH = 5.5) than in alkaline (pH = 8) conditions. Moreover, formaldehyde stimulation was able to induce ERK pathway activation. The data obtained suggest the need for an even increasing attention to the potentially harmful effects of textile manufacturing by-products.