Exposure to printing inks is grossly underestimated

Frequent detection of the photoinitiator isopropylthioxant (ITX) in baby milk, dairy products and cloudy fruit juices packaged in beverage cartons highlights the need for more regular screening of food products packaged in paper and cardboard. UV filters have been associated with exposure to sensitization, endocrine activity and cancer. In this study, researchers from the Technical University of Dresden (TU Dresden) and the German Food Law Enforcement Agency of Baden-Württemberg (CVUA) analyzed 310 packaging materials containing dry food products for the presence of 11 photoinitiators and amine synergists. Ultraviolet (UV) filters such as ITX and benzophenone (BP), previously found in food, are used in UV-curable printing inks and varnishes. Some UV filters such as BP require amine synergists to improve curing. BP has shown a positive response in uterine nutrition tests for estrogenic activity and is classified as a high yield chemical. Printing inks are currently not specifically regulated by European law, although substances used in food contact materials are not usually hazardous to human health, and some printing inks are regulated by plastics regulations. As a result, most printing inks still lack toxicological assessment and specific migration restrictions in Europe. In the people's study, they detected BP in 49% of the packaging samples.

The method.

To analyze the substances present in the packaging material, 0.5 dm 2 of the packaging material was cut into small pieces and extracted with acetonitrile at 70°C for 24 hours. Depending on the absorbency of the food, 25 or 45 ml of the food was extracted at 70°C for 24 hours. Cereal was selected as the worst-case food simulant for the recovery test. Migration of dry grains was studied using food simulants according to Eurocode Standard 14338. The extracts were analyzed using high performance liquid chromatography with diode array detection (HPLC-DAD). The recoveries ranged from 90% to 110%. The detection limits for packaging materials ranged from 2.8 (BP) to 29 (PBP) µg/dm 2 and 2.5 (except BP) to 38 (BP) µg/dm 2.

Results.

BP was detected in 49% of the package samples. other photoinitiators and amine synergists were detected in less than 10% of the package samples. The researchers found the highest concentration of BP in the cocoa paperboard packaging at 2510 µg/dm 2. Packaging for cereal, Indian papaya and breakfast cereals also contained high levels of photoinitiators and amine synergists.

The German researchers analyzed only the contents of packages that did not have an obvious barrier material such as aluminum foil. They detected photoinitiators and amine synergists in 33 of the 99 foods analyzed.20 Containing more than the regulatory

20 contained photoinitiators or amine synergists that exceeded regulatory limits. The legal limit of 600 µg/kg was exceeded in 12 of the 23 BP-quantified food samples.6, 3, 1 and 1 products violated the SML for methyl benzophenone (MBP), methyl o-benzoylbenzoate (MOBB), ethyl 4-dimethylaminobenzoate (EDAB) and 2-ethylhexyl-4-(dimethylamino)-benzoate (EHDAB) as specified in the Swiss decree, respectively. The authors confirmed that the polyethylene liner is permeable to BP and that BP also migrates through the gas phase, independent of paper or polypropylene barriers.

To assess migration over time and to avoid cross-contamination, eight samples with high levels of photoinitiator were wrapped in aluminum foil until the expiration date. This form of storage also simulated the storage of a large number of packages on trays. Migration of 1-hydroxycyclohexyl phenyl ketone (HCHKP) was found to be very rapid and reached a level of 4260 µg/kg after 3.5 months. In addition, BP and MBP migrated into the food through the internal PE packaging material. On the other hand, the migration of PBP into food was still very low, despite the large amount of PBP detected in the packaging. Therefore, it is generally observed that contaminants with small PE was found to have, at best, a temporary barrier effect to slow migration.

To confirm that the results were not food-related, migration tests were also performed using food. For this purpose, three cardboard samples were coated with UV varnish and one with dispersion varnish without photoinitiator. BP was detected in all materials. even the dispersion varnish contained low levels of BP, which the authors assume is due to cross-contamination. BP was detected in three food simulants contained in UV-coated paperboard. 36% of the HCHPK detected in the packaging was transferred to the food simulants. The migration variation measured between the different paperboard samples using UV-cured inks may be due to the level of cross-linking of the polymer network. Among other factors, the crosslinking depends on the quality of the light used for the UV curing process.

In conclusion, the authors confirmed that many food products packaged in paperboard contain photoinitiators and amine synergists when UV-curable inks are used. The lack of sufficient barriers indicates a lack of awareness among food packaging manufacturers. Junger et al. found that photoinitiator and amine synergist concentrations, vapor pressure and crosslinking were related to transfer rates. Concentration alone did not adequately predict the transfer rate. When using Tenax® for migration testing, they recommend using true surface to mass ratios, otherwise daily intakes will be grossly underestimated.