Safety evaluation of mechanical recycling processes used to produce polyethylene terephthalate (PET) intended for food contact applications.

The development of a scheme for the safety evaluation of mechanical recycling processes for polyethylene terephthalate (PET) is described. The starting point is the adoption of a threshold of toxicological concern such that migration from the recycled PET should not give rise to a dietary exposure exceeding 0.0025 µg kg(-1) bw day(-1), the exposure threshold value for chemicals with structural alerts raising concern for potential genotoxicity, below which the risk to human health would be negligible. It is practically impossible to test every batch of incoming recovered PET and every production batch of recycled PET for all the different chemical contaminants that could theoretically arise. Consequently, the principle of the safety evaluation is to measure the cleaning efficiency of a recycling process by using a challenge test with surrogate contaminants. This cleaning efficiency is then applied to reduce a reference contamination level for post-consumer PET, conservatively set at 3 mg kg(-1) PET for a contaminant resulting from possible misuse by consumers. The resulting residual concentration of each contaminant in recycled PET is used in conservative migration models to calculate migration levels, which are then used along with food consumption data to give estimates of potential dietary exposure. The default scenario, when the recycled PET is intended for general use, is that of an infant weighing 5 kg and consuming every day powdered infant formula reconstituted with 0.75 L of water coming from water bottles manufactured with 100% recycled PET. According to this scenario, it can be derived that the highest concentration of a substance in water that would ensure that the dietary exposure of 0.0025 µg kg(-1) bw day(-1) is not exceeded, is 0.017 µg kg(-1) food. The maximum residual content that would comply with this migration limit depends on molecular weight and is in the range 0.09-0.32 mg kg(-1) PET for the typical surrogate contaminants.

The sources of light and lighting at work.

Succeeding in lighting industrial, office and other work environments is dependent on many factors. Good result is not guaranteed if only one of these factors is taken into account. It is essential to choose appropriate light sources and use them correctly for different tasks. Although the amount of light and its composition is considered satisfactory for a certain task, glare and reflected glare still cause inconvenience in the work places making the performance of visual tasks difficult. The lux and luminance levels of the work areas regulate the size of the observer's pupils. The size of the pupil determines for its part how easily and quickly eyes can be accommodated for a sight distance. The indirect disadvantages caused by poor visual conditions are often significant. For example at display work reflected glare does not only slow down reading. The effort to avoid the reflections from the screen by changing the direction of observation effects the working positions. Inconvenient posture may cause pains in the neck and back. In lighting design the problems of age vision are taken into account. We should also bear in mind the significance of the colour of light when considering these problems.