In an article published on May 24, 2022, in the journal Environmental Science and Pollution Research, Hao‑Wen Zhong and co-authors from Jinan University, Guangzhou, China, present a biomonitoring study investigating whether consumption of takeaway food is connected with increased phthalate levels and oxidative stress. Zhong and colleagues collected spot urine samples from 288 college students from several universities in Guangzhou, south China, between April and July 2021 to analyze them for 19 phthalate metabolites as well as 8-hydroxydeoxyguanosine (8-OHdG), a marker for DNA oxidative damage. Participants further completed a questionnaire on personal information, and takeaway food eating habits (e.g., frequency, type). Students were divided into four groups based on their frequency of takeaway food consumption: less than 3-times per week, between 3 and 7, between 8 and 12, and above 12 times per week.
Seven of the 19 monitored phthalate metabolites as well as 8-OHdG were detected in all urine samples. With a median concentration of 3.10 µg per kg body weight per day (µg/kg bw/ day), the exposure dose was highest for di-butyl phthalate (DBP, CAS 84-74-2). Comparison with tolerable daily intake (TDI) doses showed that DBP exceeded the TDI of 10 µg/kg bw/day by 8.3%. TDIs of di-isobutyl phthalate (DIBP, CAS 99 84-69), di-(2-ethylhexyl) phthalate (DEHP, CAS 117-81-7) and di-(2-propyl heptyl) phthalate (DPHP, CAS 53306-54-0) were also exceeded. No association was found between the frequency of takeaway food consumption and levels of the DNA oxidative damage marker, 8-OHdG, but instead between phthalate exposure and 8-OHdG (0.639 – 33.7 ng/mL).
Total urine phthalate metabolite levels were detected to be between 42.5 and 893 ng/mL in all participants. Zhong et al. further reported that phthalate metabolite levels were lowest in the group with least often takeaway eating and the concentration of most metabolites increased with increasing frequency of takeaway consumption. The authors concluded, “that people who regularly consume takeaway foods (e.g., more than three times per week) have higher phthalate exposure levels, especially DEHP, DIBP, and DINP.”
Li’e Zhang from Sun Yat-sen University, Guangzhou, China, and co-authors, also performed a phthalate metabolite biomonitoring study in Guangzhou, China, but studied whether phthalates induce inflammation. In an article published on May 18, 2022, in the journal Environmental Science & Technology, they describe that they evaluated phthalate metabolite levels and inflammatory cytokine expression in 48 college students in December 2018. Since the scientists aimed to analyze how high-temperature (> 60°C) soup packaged in plastic affects analyte levels, they collected urine and blood samples before, during, and after a five-day intervention period where participants had to eat hot soup stored for 30 min in plastic twice a day.
Monitoring ten major metabolites of six phthalates showed “that urinary creatinine adjusted levels of monomethyl phthalate (MMP, [CAS 4376-18-5]), mono-n-butyl phthalate (MBP, [CAS 131-70-4]), mono-isobutyl phthalate (MIBP, [CAS 30833-53-5]), and total phthalate metabolites in the intervention period were significantly higher, with increases of 71.6, 41.8, 38.8, and 29.8% for MMP, MBP, MIBP, and the total phthalate metabolites, respectively.” Therefore, the authors assumed that these compounds originated from the plastic packaging.
Zhang and co-authors also measured mRNA levels of ten and protein levels of six inflammatory cytokines in the participants’ blood samples. While mRNA levels of some cytokines were increased and some decreased in the intervention period, protein levels did not change. Consequently, the dietary intervention only seemed to change cytokine mRNA expression but not protein levels.
Analyzing the association between phthalate metabolite and cytokine levels, the researchers found that “phthalate exposure may be associated with increased expression of proinflammatory cytokines at both the gene and protein levels and decreased expression of anti-inflammatory cytokine protein levels across dietary intervention periods.” For instance, they reported a positive association between mRNA levels of the pro-inflammatory cytokines, I-8 and TNF-α with DEHP, DBP, and DIBP metabolites, and the protein level of IL-8 and MMP. On the other hand, the association between protein levels of the anti-inflammatory cytokine IL-10 and MBP and MIBP levels were negative.
The authors clarified that large-scale population studies would need to verify their results since they only included 48 participants. However, they think their results “provide necessary information for consumers’ choices, regulatory decision-making, and health risk management.”
A biomonitoring study from 2021 that surveyed adolescents and children in the US and New Zealand, found that diet partly explains urinary phthalate levels (FPF reported). Increased urinary phthalate levels have previously been associated with high fast food consumption (FPF reported) as well as with eating out compared to food preparation at home (FPF reported). Phthalates were among the priority substances selected for advanced human biomonitoring under The European Human Biomonitoring Initiative (HBM4EU) which ran from December 2016 to early 2022 (FPF reported). HBM4EU found that following the regulation of some phthalates, measured levels within Europeans were going down but detection frequency remained high (FPF reported).
According to a review published in September 2021, there is “robust evidence” for an association between phthalate exposure and lower semen quality, neurodevelopment, and risk of childhood asthma (FPF reported). In 2017, the EU REACH Committee recognized diisobutyl phthalate DIBP, DBP, benzyl butyl phthalate (BBP, CAS 85-68-7), and DEHP as substances of very high concern (SVHCs) due to their endocrine disrupting properties (FPF reported).
In an article published on May 29, 2022, in the journal Toxics, Torki A. Zughaibi and co-authors from King Abdulaziz University, Jeddah, Saudi Arabia, examined whether non-phthalate alternative plasticizers have lower endocrine disrupting potential. Specifically, they analyzed the potential of diisononyl hexahydrophthalate (DINCH, CAS 166412-78-8), acetyl tributyl citrate (ATBC, CAS 77-90-7), and di-(2-ethylhexyl) adipate (DEHA, CAS 103-23-1) to disrupt thyroid activity.
To approach this aim, the scientists used a molecular docking simulation approach based on the structural binding characteristics of the analytes against the thyroid hormone receptor alpha (TRα). Zughaibi and co-authors reported that all plasticizers “were stably placed in the TRα ligand-binding pocket” with DINCH and ATBC showing higher binding energy and higher thyroid disruption potential than DEHA and DEHP. They concluded “all three alternate plasticizers i.e., DINCH, ATBC, and DEHA have the potential to disrupt thyroid signaling, which may result in alteration of thyroid hormone homeostasis, leading to thyroid-related adverse effects on health.”
References
Zhang, L. et al (2022). “High-temperature soup Foods in plastic packaging are associated with phthalate body burden and expression of inflammatory mRNAs: A dietary intervention study.” Environmental Science & Technology. DOI: /10.1021/acs.est.1c08522
Zhong, H.-W. et al (2022). “Phthalate exposure and DNA oxidative damage in young people of takeaway food lovers.” Environmental Science and Pollution Research. DOI: 10.1007/s11356-022-20849-z
Zughaibi, T. A. et al (2022). “Insights into the endocrine disrupting activity of emerging non-phthalate alternate plasticizers against thyroid hormone receptor: A structural perspective.” Toxics. DOI: 10.3390/toxics10050263
