## 4 Discussion/Conclusions
### Analysis of Thermal Decomposition Products (Pyrolysis and GC-MS)  
In performing pyrolysis, the heating of the polymers revealed which substances were produced in abundance and in traces. From these results, initial predictions can then be made about the risk of such plastic particles and their degradation products in various baked foods. However, not all parameters needed for a specific toxicological assessment could be considered in this study, and further studies are needed for a complete estimation. In the case of the ABS polymer, the main substances detected were styrene, benzaldehyde, and acrolein. This is concerning, as all these substances are considered carcinogenic [18; 19]. Furthermore, substances such as acetophenone, methylstyrene, and ethylbenzene were found. These substances are also harmful to health, as they can irritate the respiratory system [18; 19]. In addition, it was possible to detect traces of substances such as ketones, phenols, alkenes, and aromatics. However, they can be neglected due to their low concentrations. Analysis of the PS polymer revealed mainly benzaldehydes and styrenes as products. Benzaldehydes are only considered harmful to health in higher quantities. In the case of syrenes, there is a risk of them being converted into styrene oxides when ingested [20; 21]. These are extremely dangerous, as they are potentially muta genic and carcinogenic [18; 19; 20]. Substances such as benzene or benzyl alcohol were found in traces. The results of the analysis of the melamine polymer are extremely worrying, as the major products were the very toxic and carcinogenic substance formaldehyde [18; 19] and the toxic and highly hazardous substance methanol [18; 19]. This was observed when pyrolysis was carried out at both temperatures of 200 \({}^{\circ}\)C and 250 \({}^{\circ}\)C. In addition, the presence of acetaldehyde, methyl formates, and 2,3-butananedione could be determined at a temperature of 250 \({}^{\circ}\)C. At the temperature of 200 \({}^{\circ}\)C, these could only be found in traces. In Germany, it is forbidden to heat products containing melamine to over 70 \({}^{\circ}\)C, since formaldehyde is released at this temperature [22]. Regarding the LDPE polymer, the formation of the substance acetaldehyde, which is harmful to health and carcinogenic, was one the main products. Acetic acid was also synthesized in higher quantities. The acid has an irritating effect on mucous tissues [18; 19]. Formic acid was also released, which is considered dangerous, especially in high concentrations, as it is irritating to the eyes and can cause respiratory distress if inhaled [18; 19]. Butane was also formed, which has a fatiguing effect [23], as well as aldehydes, which can potentially cause allergies [18; 19]. Traces of acroleine, propane, ketones, and short-chain alcohols were detected. However, in the second pyrolysis experiment at a temperature of 250 \({}^{\circ}\)C, both acetic acid and formic acid were not formed. Pyrolysis products of SAN polymer have been identified primarily as styrene and ethylbenzene. These are both considered hazardous to health, as they can cause cancer. However, when pyrolysis was carried out at 250 \({}^{\circ}\)C, acetophenones and benzaldehyde were also formed in larger concentrations. The trace substances formed at both 200 \({}^{\circ}\)C and 250 \({}^{\circ}\)C included hydrocyanic acid and phenols as well as other aromatic hydrocarbons and acetophenone. More trace substances were found during pyrolysis at 250 \({}^{\circ}\)C. When examining the resulting products concerning the polymer PP, acetone as well as formic and acetic acid could be identified in large quantities. Acetone is extremely harmful because it is particularly irritating to the eyes. The same applies to acetic acid. Formic acid is very damaging if it is ingested and, in addition, it has a severe corrosive effect on tissues. In addition, methanol was detected. This is hazardous to health when inhaled, touched, or ingested.