Migration and Toxicity
Composition. A polyester of terephthalic acid and ethylene glycol can be obtained by the poly= condensation of dimethyl terephthalate (q.v.) with ethylene glycol, and also terephthalic acid with ethylene glycol or ethylene oxide.
Properties. A white or light-cream material. Noted for high heat resistance and chemical stability. When melt-blown, it provides a good barrier for both flavors and hydrocarbons (fat). It is not transparent. PET is resistant to acids, bases, some solvents, and oils and fats. It is difficult to mold. The melting point of unmodified PET is below boiling. Monolayer films will hold a crease, are heat sealable, and transparent. Dens. 1.33220. M. p. 255 to 265°C. n25 =1.574. Insoluble in water.
Applications. PET is used for high-impact resistant containers. It is used for packaging of soda, mouthwash, pourable dressings, edible oils, and peanut butter. It is used for cereal box liners, soda bottles, boil-in-the-bag pouches, and microwave food trays. Modified PETS can be heated in a microwave or in a conventional oven at 180°C for 30 minutes. There has been a moderate amount of concern that additives from these trays may migrate into foods, particularly if the trays are reused in a microwave oven. PET is also used in the production of different bottles, fibers, films for food packaging, and different articles. Lavsan fabric is used in the dairy industry for filtering. Used in medicine for plastic vessels and for implantation.
Migration Data. A total of 19 migrants from commercial amber PET bottle wall has been identified by GC/MS analysis: the majority of compounds appeared to be intermediate reaction products or residual monomers of their dehydration and transesterification products. Fatty acids and commonly used plasticizers were also identified.1
Quantities of PET cyclic oligomers found in the microwaveable French fries, popcorn, fish sticks, waffles, and pizza ranged from less than 0.012 to approximately 7.0 g/kg.2
PET contains detectable amounts of acetaldehyde, which is able to migrate from the polymer into liquid media With the help of a static headspace GC method, acetaldehyde was found in carbonate mineral water and lemonade. Acetaldehyde concentration ranged between 11 and 7.5 mg/l, while the contents of acetaldehyde in the PET packages ranged from 1.1 to 3.8 µg/g.3
Migration of acetaldehyde from PET at 40°C reached a constant level after 4 days which was about 10% of the residual value of acetaldehyde (6.3 mg/kg). At 60°C this level was raised up to 50%.
PET caused no changes in the taste of soft drinks containing carbonic acid when exposed at lower temperature and over a relatively short period of time 4 Lavsan material had no effect on the taste and odor of aqueous extracts, nor on their oxidizability. Migration of antimony ion (catalyst) into water was not observed.07 Piekacz discovered migration of calcium and magnesium ions from pellets and film. Diethylene glycol and dimethyl terephthalate were not found in extracts.5
PET samples including laminates, bottles, and roasting bags, were heated at 120, 150, and 230°C for 50 min, according to sample type. Volatiles released from the material were identified by GC-MS and assessed against a 10 mg/kg migration threshold limit. The main substances identified were not related to PET, but probably came from printing inks and adhesives. Authors concluded that the migration potential of PET in high temperature applications is very low and that the formation of volatiles during use is unlikely to cause any special problems in polymer recovery in recycling schemes.6
Migration of ethylene glycol (EG) from PET bottles stored at 32°C for 6 months into the food simulant 3.0% acetic acid was studied by gas-liquid chromatographic procedure and observed at the level of about 94 µg EG/bottle.7
Migration of residual contaminants remaining in the extruded PET (benzene, butyric acid, dodecane, octadecane, tetracosane, diazinon, lindane, and cooper ethyl hexonate) into food-simulating solvents, aqueous ethanol, and heptane, resulted in concentrations lower than 0.01 mg/kg. Authors concluded that unwashed recycled PET may not comply with FDA requirements.
Migration of antimony from PET into food simulants, measured by inductively-coupled plasma-mass spectrometry amounted to 4.0 µg/kg. The concentration found was less than proposed limit of migration.9
Migration from colored PET bottles for carbonated beverages was studied. PET bottles filled with naturally carbonated mineral water up to 6-month storage released total organic carbon within the EEC and FDA limits. The following migrating substances were identified by GC-MS analysis: acetaldehyde, dimethyl terephthalate, and terephthalic acid. 10
Acute Toxicity. Neither administration of PET powder nor a single administration of chloroform extracts of PET at a dose of 10 g/kg BW had a toxic effect on rats."
Repeated Exposure. In a 1-month study, rats received wine extracts obtained after several months contact with PET. The treatment produced no harmful effect on animals. 12
Short-term Toxicity. Rats were given 5.0 to 400 mg technical grade PET/kg BW and 5.0 to 100 mg pure PET/kg BW over a 3-month period. There were no changes in their behavior, BW gain, biochemical indices of blood serum, urine, or hematology analyses, or in relative weights of internal organs."
Long-term Toxicity. No manifestations of toxicity were observed in rats, given aqueous extracts of PVC film reinforced with Lavsan. 13
In vitro genotoxicity. De Fusco et al. studied the mutagenicity in unconcentrated mineral water stored in PET bottles and growing Salmonella strains directly in the plastic bottles. Leaching of mutagens after 1 month of water storage in daylight and in the dark in PET bottles used for beverage packaging was noted. This activity was higher after storage in daylight. 14 The mutagenicity test on non-volatile migrant compounds identified in the above-sited study gave negative results. 10
Carcinogenicity. Dacron induced malignant tumors at the site of application in rodents following s/c imbedding of polymer films. Nevertheless, the results of this study have been later considered inadequate. 026 S/c implantation of pieces of PET graft to mice and Syrian golden hamsters showed no statistical evidence of tumor induction. Observation period was 73 and 82 weeks, respectively. 15
Regulations. U.S. FDA (1998) approved the use of PET as components of polyethylene phthalate polymers intended for use in contact with food in accordance with the conditions prescribed in 21 CFR part 177.1630.References:
1. Kim, H., Gilbert, S. G., and Johnson, J. B., Determination of potential migrants from commercial amber polyethylene terephthalate bottle wall, Pharmacol. Res., 7, 176, 1990.
2. Begley, I. H, Dennison, J. L, and Hollifield, H. C., Migration into food of polyethylene terephthalate (PET) cyclic oligomers from PET microwave packaging, Food Addit. Contam., 7, 797, 1990.
3. Linssen, G., Reitsma, H., and Cozynsen, G., Static headspace gas chromatography of acetaldehyde in aqueous foods and polythene terephthalate, Z. Lebensm. Untersuch. Forsch., 201, 253, 1995.
4. Eberhartlinger, S., Steiner, J., Washuttl, J., and Kroyer, G., The migration of acetaldehyde from polythene terephthalate bottles for fresh beverages containing carbonic acid, Z. Lebensm. Untersuch. Forsch., 191, 286, 1990.
5. Piekacz, H., in Cz. II Ricz. Panst. Zakl. Hig., 22, 295, 1971 (in Polish).
6. Freire, M. T., Castle, L., Reyes, F. G., and Damant, A. P., Thermal stability of polyethylene terephthalate food contact materials: formation of volatiles from retain samples and implications for recycling, Food Addit. Contam.,15, 473, 1998.
7. Kashtock, M. and Breder, C. V., Migration of ethylene glycol from polyethylene terephthalate bottles into 3% acetic acid, J. Assoc. Off. Anal. Chem.,63, 168, 1980.
8. Komolprasert, V., Lawson, A. R., and Begley, T. H., Migration of residual contaminants from sec . lary recycled poly(ethylene terephthalate) into food-simulating solvents, aqueous ethanol and heptane, Food Addit. Contam., 14, 491, 1997.
9. Fordham, P. J., Gramshaw, J. W., Crews, H. M., and Castle, L., Element residues in food contact plastics and their migration into food simulants, measured by inductively-coupled plasma-mass spectrometry, Food. Addit. Contam., 12, 651, 1997.
10. Monarca, S., De Fusco, R., Biscardi, D., De Feo, V., Pasquini, R., Fatigoni, C., Moretti, M., and Zanardini, A., Studies of migration of potentially genotoxic compounds into water stored in pet bottles, Food Chem. Toxicol., 32, 783, 1994.
11. Otaka et al., cit in Excerpta Medica, Sec. 17, 1, 1980, Abstract 284.
12. Bazanova, A. I., Effect of chemical substances extracted from plastics on mammals and micro
organisms, in Toxicology and Hygiene of High-Molecular-Mass Compounds and of the Chemical
Raw Material Used for Their Synthesis, Proc.3rd All-Union Conf, S. L. Danishevsky, Ed., Khimiya,
Moscow-Leningrad, 1966, 113 (in Russian).
13. Kupyrov, V. N., Kaplina, T. V., Gakal, R. K., Vinarskaya, E. I., and Starchenko, S. N., Hygienic evaluation of films intended for the waterproofing of unit prefabricated swimming pools, Gig. Sanit., 5, 91, 1978 (in Russian).
14. de Fusca, R., Monarca, S., Biscardi, D., Pasquini, R., and Fatigoni, C., Leaching of mutagens into mineral water from polyethylene terephthalate bottles, Sci. Total Environ., 90, 241, 1990.
15. Blagoeva, P., Stoichev, I., Balanski, R., Purvanova, L., Mircheva, T. S., and Smilov, A., The testing for carcinogenicity of a polyethylene terephthalate vascular prosthesis, Khirurgia, 43, 98, 1990 (in
source: Sheftel, VO. Indirect Food Additives and Polymers: Migration and Toxicology. Lewis Publishers, Boca Raton, FL, 2000. pp.1132-1134
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