Beyond BPA – Many bisphenols migrate from food packaging
Four studies investigate bisphenol (BP) migration from food packaging and human health effects; demonstrate wide presence of 11 bisphenols in polystyrene take-out food containers from China, Canada, and Poland; report material quality influences BPA migration from polycarbonate cups; indicate higher BPA migration from lined cans than plastic packaging into meat based on probabilistic models; find bisphenols A, F, and S induce genotoxic effects and changes in human endogenous retroviruses (HERVs) expression using human blood cells.
In an article published on September 9, 2022, in the journal Environmental Science and Pollution, Nan Zhao and co-authors from Zhejiang University of Technology, Hangzhou, China, analyzed white foam take—out containers made of polystyrene (PS) for the presence of 20 different bisphenols and estimated exposure for the general population. They acquired 152 new containers, mainly used for fast food packaging, from restaurants located in 21 Chinese and three Canadian cities as well as in Krakow, Poland between 2018 and 2019. Zhao and colleagues performed migration experiments with food simulants (tap water, 10% and 50% ethanol, corn oil) and food (rice) by heating the samples to 100 °C and keeping them for 30 min at room temperature. They also extracted the chemicals from the containers using methanol as a solvent. Using ultra-performance liquid chromatography (UPLC) coupled with mass spectrometry, allowed the scientists to determine the quantity of the 20 target bisphenols.
Zhao et al. detected 11 bisphenols in the 126 samples collected in China, five in the 18 samples collected in Canada, and four in the six samples from Krakow. Overall of the 11 detected bisphenols, bisphenol A (BPA; CAS 80-05-7) was found most frequently, followed by bisphenol S (BPS; CAS 80-09-1) and bisphenol AF (BPAF; CAS 1478-61-1). The concentrations varied between countries; PS containers from China had the highest mean concentrations for BPA and BPS with 2694 and 5525 ng/g, respectively while the corresponding levels in Canadian samples were 81 and 45 ng/g, and in Polish samples 95 and 16 ng/g.
The researchers also estimated the daily intake of BPA, BPS, and bisphenol TMC (BPTMC; CAS 129188-99-4) by using the analyzed PS containers and reported the intake to be “0.50 − 547, 0.054 − 229, and < 0.66 ng/kg bw/day, respectively, for the general population in China, Canada, and Poland.” However, BPTMC was only detected in samples from China and the estimated daily intake was calculated to be 0.065 and 0.055 ng/kg bw/day for females and males, respectively. The authors concluded that their “results suggest that humans were widely exposed to bisphenols through using white foam take-out containers.”
BPA can not only be used as an additive, which might have been the reason for the presence in the PS containers, but also as a monomer for polycarbonate (PC) based plastics. Aparna Agarwal from the University of Delhi, New Delhi, India, and co-authors, quantified the levels of BPA migrating from PC cups into coffee and the influence of microwave heating. In their article published on September 22, 2022, in the International Journal of Food Science + Technology, they described that they compared chemical migration from six locally manufactured with six branded microwavable PC cups into approximately 85 °C hot coffee after different contact times (10, 30, and 60 min) and with and without subsequent microwave heating. BPA concentrations were analyzed by UPLC.
The researchers detected BPA in levels of up to 391 ± 0.05 µg/kg in the analyzed samples. They reported that BPA migration was “minimal in good-quality PC cups”, i.e., branded cups. According to the authors, branded PC containers would “have better material composition and processing conditions than local containers” leading to a worse quality of the local containers. Furthermore, longer contact times and microwave heating were found to increase BPA migration from the locally produced cups. Agarwal and co-authors expressed the need for the Food Safety and Standards Authority of India to specify the tolerable daily intake of BPA and for the Indian government to restrict its use in plastic food contact materials in general.
Xin Wang and co-authors from the University College Dublin, Ireland, also aimed to investigate factors influencing BPA migration. In their study, published on September 14, 2022, in the journal Science of the Total Environment, they developed two probabilistic models to estimate BPA migration from plastic and can packaging, respectively, into meat and meat products. Parameters considered in their models included BPA concentrations in the packaging, food contact areas, migration ratios (calculated based on storage conditions and initial BPA concentrations in the packaging), ratios of weight to surface area, and an uncertainty factor amongst others. Different scenarios were modeled. For the plastic packaging, migration from polyvinyl chloride (PVC)-based films, mainly polyethylene terephthalate (PET)- based trays, and from both films and trays was estimated based on BPA concentrations reported in the literature. For the cans, epoxy-based coatings, and polyester-based coatings were considered. The probabilistic approach was conducted based on the Monte Carlo simulation “that produces a range of possible outcomes from the repeated calculation of random sampling of input values.”
The modeling showed that higher levels of BPA migrated from the can compared to the plastic packaging. Specifically, from plastic packaging, BPA migrated in concentrations between 0.017 to 0.13 (5th–95th percentile) µg/kg with a simulated mean of 0.056 µg/kg while it migrated from cans in concentrations from 59.17 to 223.25 µg/kg (5th–95th percentile) and a simulated mean of 134.57 µg/kg. Based on these results, Wang and co-authors estimated that plastic packaging contributes only 3% of BPA levels in meat products leading them to conclude “that plastic packaging may not be the only or dominant source of BPA in non-canned meat products.” Migration ratios were slightly higher for the trays than for the films. For the canned meat they expressed the “need for caution regarding BPA migration from the can coatings.” The plastic packaging migration model further demonstrated that the contact area of food and packaging has the greatest impact on BPA migration.
The authors highlighted that their modeling procedure is a fast and cheap approach to define more focused experimental testing. As a subsequent step, they suggested examining other BPA contamination sources in food such as industrial processing. Overall, their results would indicate “that plastic packaging contributes little to the BPA contamination in non-canned meat products.”
Exposure to BPA and other bisphenols has been found to increase the risk of cancer (FPF reported), including prostate (FPF reported) and breast cancer (FPF reported). In an article published on August 12, 2022, in the journal Environmental and Molecular Mutagenesis, Stefano Roberto and co-authors from the University of Sassari, Italy, investigated the genotoxic effects of BPA and its widely used analogs bisphenol F (BPF; CAS 620-92-8) and BPS using an in vitro micronucleus assay as well as the effect on the expression of human endogenous retroviruses (HERVs). HERVs expression is associated with the pathogenesis of several human diseases (e.g., neurodegenerative diseases, and cancers). Human peripheral blood mononuclear cells were used to perform the micronucleus assay as well as to analyze the expression of HERV-H/env and HERV-R/env genes.
The assay results showed that BPA and also its analogs BPS and BPF increase micronuclei frequency indicating genotoxic effects in the peripheral blood cells. BPA and BPF induced these effects at concentrations down to 0.0025 µg/ml and BPS down to 0.05 µg/ml. Furthermore, all three bisphenols changed the expression of HERVs. However, while BPA led to an upregulation, BPF and BPS led to a downregulation. The authors emphasized that the sample size of their study was small but the relationships between exposure and effects were strong. They recommended performing in vivo studies with a larger sampling size. Roberto et al. concluded that “BPA, BPS, and BPF reported significant genotoxicity in peripheral human blood even at a concentration of reference dose, so these BPA analogs need further studies to better assess their long-term impact on human health.”
In December 2021, the European Food Safety Authority (EFSA) proposed to lower the tolerable daily intake of BPA from 4 µg/kg body weight/day to 0.04 ng/kg body weight/day (FPF reported). And in April 2022 the European Chemicals Agency (ECHA) recommended that 34 bisphenols be classified as substances of very high concern (SVHCs) as a group in order to avoid regrettable substitution.