Exposure to endocrine-disrupting chemicals (EDCs), such as phthalates and bisphenols, has been linked with chronic diseases (FPF reported and here) and food and beverages are one source of EDCs (FPF reported and here). Two studies investigated how diet may influence exposure to EDCs, and one assessed whether and to what extent phthalates and bisphenol A (BPA, CAS 80-05-7) contained in microplastics become bioaccessible when consumed.
In an article published on February 28, 2022, in the journal Environmental Research, Melissa M. Melough from Seattle Children’s Research Institute, US, and co-authors evaluated whether healthy diets recommended to prevent chronic diseases reduce exposure to non-persistent EDCs.
For their analysis, Melough and co-authors used EDC levels measured in spot urine of 6,862 US adults as part of the National Health and Nutrition Examination Survey (NHANES; FPF reported here, here, and here) between 2013 and 2016. Among the EDCs considered in the study were several bisphenols, phthalates, naphthalenes, fluorenes, anthrenes, as well as 1-hydroxypyrene (1-PYR), perchlorate, nitrate, and thiocyanate. Participants were also asked to recall their food and beverage consumption on the day of urine sampling. Using multivariable linear regression, the authors analyzed whether healthy diet scores, i.e., the Healthy Eating Index (HEI), relative Mediterranean Diet (rMED), and Dietary Approaches to Stop Hypertension (DASH), were associated with urinary EDC concentrations.
For most EDCs studied, the researchers observed no association between diet and the chemical’s level, which suggests that, based on the three diets analyzed, “recommended healthy diets were not protective against EDC exposures.” None of the three diets were associated with lower urinary levels of bisphenols, phthalates, or polycyclic aromatic hydrocarbons (PAHs). The scientists further reported that recommended diets may even increase exposure to some EDCs. For instance, the Mediterranean diet was found to be associated with higher exposure to nitrate and perchlorate, whose cumulative exposure “may inhibit thyroid hormone production, potentially increasing risks for adverse health outcomes in key stages of development.” A previous study found that fast food consumption leads to higher urinary phthalate levels (FPF reported). Melough and co-authors emphasized the need to identify strategies in food production and processing that effectively reduce EDCs in food and thus dietary exposure.
Francesco Sessa from the University of Foggia, Italy, and co-authors also evaluated the association between diet and urinary EDC levels but looked at children and whether a diet using less plastic food packaging was associated with reduced BPA (CAS 80-05-7) levels. Their research was published on February 1, 2022, in the journal Frontiers in Public Health. The scientists analyzed urinary BPA levels of 15 Italian children that consumed one plastic-free meal at school five days a week over six months and compared it to data from 15 children with unchanged meal habits. The authors reported that BPA decreased after six months in the ‘plastic-free meal’ group as well as in comparison to the ‘control’ group. Thus, though they acknowledged the small size of the study, Sessa et al. concluded that “reduction in the use of plastic food packaging directly correlates with a decrease of urinary BPA concentration.”
Humans may also be exposed to EDCs when microplastics are consumed with food and beverages, and any EDCs contained in the particles get released while passing through the body. In an article published on February 23, 2022, in the peer-reviewed journal Science of the Total Environment, Javier López-Vázquez from Universidade de Santiago de Compostela, and co-authors evaluated whether BPA and phthalate esters (PAEs) present in microplastics become bioaccessible under simulated physiologically relevant digestion conditions.
For their analysis, López-Vázquez et al. used low-density polyethylene (LDPE) and polyvinyl chloride (PVC) particles with average sizes of 110 µm and 140 µm, respectively, that had eight PAEs and BPA (only in LDPE) added in certified concentrations of either 30,000 µg/g or 3000 µg/g depending on the substance. To simulate the human digestion process, they applied physically relevant extraction conditions that mimic the different digestive fluids of the gastric and small intestine compartments. Subsequently, the scientists measured the leached compounds in the respective gut fluid using gas chromatography-mass spectrometry (GC-MS) and determined the bioaccessible and non-bioacessible fraction of the compounds in microplastics. The bioaccessible fraction is “the maximum amount of compound amenable to be bioavailable and reach the systemic circulation.” They also compared fed and fasted states, PAEs of different polarities, as well as microplastic types with different particle sizes, surface properties, and structural rigidity and how these may influence the release of the target compounds.
The scientists found that “the oral bioaccessibility of PAEs and BPA in the gastric compartment usually accounts for more than 65% of overall bioaccessibility and increases significantly for those compounds with log Kow < 4.0”, meaning those with higher polarity. Dimethyl phthalate (DMP; CAS 131-11-3), diethyl phthalate (DEP; CAS 84-66-2), and BPA leached at the highest levels. However, DMP and DEP were partially hydrolyzed to phthalate monoesters under gastric conditions. Bioaccessibility was observed to be higher under fed- compared to fasted-state gastrointestinal extraction conditions. The authors further reported a larger release of PAEs and BPA from LDPE than PVC, which they attributed to the diverging material characteristics. For instance, PVC’s higher surface polarity may have favored the adherence of polar additives while LDPE’s larger surface area contacting the body fluids may have enhanced additive release.
López-Vázquez and co-authors also calculated potential human health risk of PAEs and BPA via microplastics ingestions by using the microplastic mass ingested daily on average, the assumption that plastics contain 0.1-5% phthalates and by comparing the results against the human safe reference values e.g., based on the oral reference doses (RfDs) provided by the US Environmental Protection Agency (EPA). The scientists found that DMP, di-n-butyl phthalate (DnBP; CAS 84-74-2), and BPA at levels of 0.3% (w/w) of the microplastics “may pose severe risks after oral uptake in contrast to the more hydrophobic congeners for which concentrations above 3% (w/w), except for diethylhexyl phthalate, would be tolerated.” They concluded that “the human uptake of primary microplastics might pose severe health risks” because of the leachability of some endocrine-disrupting additives under gastrointestinal digestion conditions, especially the most polar ones such as DMP, DnBP and BPA.
References
López-Vázquez, J. et al (2022). “Mimicking human ingestion of microplastics: Oral bioaccessibility tests of bisphenol A and phthalate esters under fed and fasted states.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2022.154027
Melissa, M. M. et al (2022). “Diet quality and exposure to endocrine-disrupting chemicals among US adults.” Environmental Research. DOI: 10.1016/j.envres.2022.113049
Sessa, F. et al (2022). “Effects of a Plastic-Free Lifestyle on Urinary Bisphenol A Levels in School-Aged Children of Southern Italy: A Pilot Study.” Frontiers in Public Health. DOI: 10.3389/fpubh.2021.626070
