Poly(ethylene terephthalate), Poly(butylene terephthalate), and Polystyrene Oligomers: Occurrence and Analysis in Food Contact Materials and Food.

Polyesters (PES) and polystyrene (PS) are among the most used plastics in the production of food contact materials (FCM). The existence of compounds that could migrate from these materials into food requires a constant analytical control to ensure the safety of consumers due to consumption. It also implies a significant research challenge for their identification and quantification. One of the most important groups of known FCM migrants are the substances known as oligomers. PES and PS oligomers have long been suspected to possess some toxicological effects. The International Agency for Research on Cancer and the European Food Safety Authority alerted recently to the potential carcinogenicity of styrene, with its oligomers consequently being also in the spotlight. At the same time, PES cyclic oligomers are categorized as having Cramer III toxicity. Many recent works on the occurrence of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and PS oligomers in FCM and food have been published. The oligomeric chemical analysis requires the use of demanding analytical strategies to address their different physicochemical characteristics (melting points, octanol/water partition coefficients, and solubility properties). Chromatographic methods are normally preferred due to the intrinsic complexity of the target matrices, but the reduced amount of reliable analytical standards still hinders the widespread screening analysis of oligomers in food. This work presents the most relevant recent studies and analytical methodologies used in the analysis of PET, PBT, and PS oligomers in food and FCM, as well as current and future challenges.

Cellular lipids and protein alteration during biodegradation of expanded polystyrene by mealworm larvae under different feeding conditions.

The present study reports the biodegradation of polystyrene (PS) by mealworm (Tenebrio molitor) following different feeding regimes. Changes in lipids and protein were studied to evaluate possible differences in the growth and metabolic pathways of the insects depending on the diets. Thermo-gravimetric analysis of the excretions (frass) revealed a decrease in the molecular mass of the PS polymers. The insects' biomass contained less protein when PS was part of the diet, suggesting that the insects undergo a certain level of stress compared to control diets. The frass also contained lower amount of nitrogen content compared to that from insects fed a control diet. NH4+ and other cations involved in biochemical processes were also measured in insects' frass, including potassium, sodium, magnesium, and calcium, combined with a small pH change. The decrease in the mineral content of the frass was attributed to increased cellular activity in PS-fed insects. A higher amount of ceramides and cardiolipins, biomarkers of apoptosis, were also found in association with PS consumption. It was concluded that the insects could metabolize PS, but this caused an increase in its stress levels.

Biodegradation of expanded polystyrene by mealworm larvae under different feeding strategies evaluated by metabolic profiling using GC-TOF-MS.

The present study investigated the biodegradation of polystyrene (PS) plastic by mealworm (Tenebrio molitor) on different diets followed by untargeted screening of larvae gut intestine tissue and frass (manure and feed residuals) to investigate the existence of polymer-generated organic residues. Three different diets, consisting of PS, rolled barley and water were tested. PS degradation rates ranged from 16% to 23% within 15 days, with no statistical differences in survival rates. The larvae fed with ad libitum barley:PS (20:1 w/w) and water had the highest growth rate, while higher PS consumption was observed for barley:PS of 4:1 w/w. A GC-TOF-MS analysis revealed no contaminating substances in the gut intestine tissue, nor styrene or PS oligomers, whilst several bioactive compounds and traces of alkanes, mostly with small carbon chains, were present. Metabolomics analysis on the collected frass, either on the lipophilic (CHCl3) or the polar fraction (MeOH-H2O) was performed. Styrene and PS oligomers (dimers, trimers) were identified, though in a relatively low total amount, up to a total of 346.0 ng/mg 2,4 di-tert butylphenol was identified in both frass and tissue, coming from the PS polymer (Non-intentionally added substances; NIAS). Finally, in the polar fraction of frass, bioactive molecules (fatty acids, amides) were identified, together with several hydrocarbons, mostly with longer carbon chains. The formation of these substances indicated enzymatic and biochemical activity in the larvae-gut intestine. It was shown that degrading and contaminating organic compounds occur at low levels, in both gut intestine and frass, during bio-degradation of PS.

Laboratory and field dissipation of penoxsulam, tricyclazole and profoxydim in rice paddy systems.

Rice cultivation relies on pesticide applications to ensure high yields. However, the regular use of pesticides seriously affects the quality of neighboring surface water systems. Thus complete knowledge of the environmental fate and dissipation of pesticides in the paddy rice environment should become available. So far only a few studies have provided comprehensive assessment of the dissipation of pesticides under the submerged cultivation conditions followed in rice. Thus, laboratory and 2-year field studies were performed to assess the dissipation of two new generation rice herbicides (penoxsulam and profoxydim) and one of the most important rice fungicides (tricyclazole). A good agreement between laboratory and field experiments was observed with a faster dissipation of penoxsulam and tricyclazole under field conditions. Profoxydim was the least persistent chemical (DT50 soil<1d; DT50 water 0.5-1.2d), followed by penoxsulam which persisted for longer particularly in the water compartment (DT50water=3.8-5.9d). Tricyclazole was the most persistent pesticide, especially in the soil compartment with DT50 values of 44.5-84.6 (field) and 197d (laboratory). These results could be utilized for the assessment of the environmental risk associated with the use of those pesticides in rice cultivation and the determination of potential mitigation measures for minimizing the risk for contamination of neighboring natural water resources.