AbstractPlasticized polyvinyl chloride will be attacked by microorganisms. The microorganisms will use the plasticizer as a carbon source, whereas favorable growth conditions, like water and oxygen, promotes their growth.A clear effect of the temperature of the water used in leaching experiments on the rate of fungal growth on the foil surface could be demonstrated. Studies also showed a difference in susceptibility of several types of plasticizers to fungal attack. The plasticizers can be divided into several classes based on their susceptibility to fungal attack.Detailed studies on the microbiological population on foil surfaces showed the predominating position of fungi. This indicated a metabiotic system between fungi and bacteria on foil surface. Addition of biocides, during manufacturing of PVC, primarily must have fungistatic properties. The fungistatic activity of 10,10′‐oxybisphenoxyarsine (OBPA) is very high, and in consequence, very low concentration must be available on foil surfaces which will prevent fungal growth. These low amounts on foil surfaces are directly correlated to the amount of OBPA insite of the foil. The transport process of the insite OBPA to the surface of the foil will principally be determined by the recepe of the foil. Therefore the application concentration recommended to ensure to achieve the minimum inhibitory concentration for fungi on the foil surface will be determined from where the application actually manifests its