Exposure levels, vinyl acetate

When critical levels of exposure to the ensuing acetaldehyde and acetic acid are achieved, thresholds are exceeded and further critical steps in the mechanism ultimately leading to cancer become active. These steps are illustrated for olfactory epithelium inFigure 14. The PBPK model predicts that in rat nasal olfactory tissue, exposure to 50-ppru vinyl acetate causes a 0.08 unit reduction in pHj and abasal cell acetaldehyde concentration of 1.7 /xg/ruL. Fifty-ppm vinyl acetate is a NOAEL,... 

Polar copolymers of ethylene, such as ethylene-vinyl acetate (EVA) and ethylene-ethyl acrylate (EEA), are readily crosslinked upon exposure to high energy irradiation [88]. In fact, the melt index of EVA can be controlled by the use of low doses (<50 kGy) of irradiation [89]. The presence in polar ethylene copolymers of comonomer units such as vinyl acetate or alkyl acrylates (methyl, ethyl and n-butyl) proportionately reduces the level of crystallinity, and since the majority of radiation responses of interest take place in the amorphous phase, the responses are more uniform throughout the polymer mass. When the irradiation is done at room temperature, the physical properties after irradiation follow the same trend as polyethylene [90]. 

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