MEASUREMENT OF STYRENE OXIDE IN POLYSTYRENES, ESTIMATION OF MIGRATIONTO FOODS, AND REACTION-KINETICS AND PRODUCTS IN FOOD SIMULANTS

The concentration of styrene-7,8-oxide has been measured in nine base resins and 16 samples of polystyrene articles intended for food contac t. The epoxide was not detected in the resins (limit of detection 0.5 mg/kg) but was found in 11 of the 16 packaging samples at up to 2.9 mg /kg. Assuming that the propensity of styrene oxide to migrate is the s ame as styrene monomer, and using existing survey data for styrene mon omer in packaging and foods, the migration levels expected for styrene oxide were calculated. Estimates were from 0.002 to 0.15 mu g/kg styr ene oxide in foods. The stability of styrene oxide in the four standar d EU food simulants was studied at 40, 100, 150 and 175 degrees C, to establish the transformation products to be expected following migrati on testing. The half-life at 40 degrees C in distilled water, 15% aque ous ethanol, 3% aqueous acetic acid and olive oil was 15, 23, <1, >200 0 hr, respectively. The principal product was the diol from hydrolysis of the epoxide group. Ring opening in aqueous ethanol simulant gave t he diol and also the glycol monoethyl ether. It is concluded that this instability of styrene oxide will reduce concentrations in foods, fro m an already low migration level to even lower levels with the formati on of hydrolysis products that are less toxic than the parent epoxide. Crown copyright.