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We attempted to determine the processing conditions for decreasing the migration of phthalate esters, particularly di-2-ethylhexyl phthalate (DEHP), from polyvinyl chloride (PVC) products using a drug solvent after dilution based on the package insert. PVC sheets and PVC tubing were subjected to optical irradiation (ultraviolet (UV), visible light irradiation) and heat treatment to determine whether they are deteriorated by these treatments. UV irradiation to one side of the PVC sheet decreased the levels of DEHP migration from the sheets by almost 50%, although the amount of DEHP content in PVC sheet was observed no significant change. On the other hand, the levels of DEHP migrating from the inner surface of PVC tubing UV-irradiated from the outer surface were not decreased compared with the control. Therefore, the surface structure was examined by conducting Fourier transform infrared spectroscopy (FT-IR), electron spectroscopy for chemical analysis (ESCA) and static angle of contact measurement. In FT-IR analysis, we found that the UV-irradiated PVC sheets were exhibited broadened absorption bands with time. In ESCA analysis, the chlorine content was decreased and the oxygen content was increased with time in UV-irradiated PVC sheets. Moreover, the other treated PVC sheets shows no significant change compared with the non-UV-irradiated PVC sheet. Therefore, the surface structure of the UV-irradiated PVC sheet was changed. As a result, the migration of DEHP from PVC products can be decreased with simple treatment, such as UV-irradiation. This could be a useful method to develop novel PVC products.

The relationships between cell attachment, cytotoxicity and in vivo tissue response such as muscle inflammation and eye irritation were investigated using lens materials, radiation vulcanized natural rubber latex (RVNRL) and standard reference materials (SRM). Five RVNRL materials, which induced muscle tissue inflammation, were cytotoxic and also significantly decreased cell attachment activities. The cytotoxic potential of a SRM made of segmented polyurethane correlated well with the decrease in cell attachment activity. However, among lens materials, cytotoxicity was detected in fluorosilicone acrylate but not in poly(methylmethacrylate) (PMMA), although the cell attachment activity of PMMA was the lowest. Eye irritation induced by wearing various kinds of lenses correlated with cytotoxic potential (r = −0·90) but not with cell attachment activities. In conclusion, in vivo toxic tissue responses correlated well with cytotoxic potentials but not always with cell attachment activity. Our experimental results also showed that direct contact colony formation was mainly inhibited by cytotoxicity, but not the low activity of cell attachment.