Jenny L. Carwile from the Maine Medical Center Research Institute, Portland, USA, and co-authors published their findings on how diet is associated with phthalate metabolite concentration in the urine of 6-19 year olds in the journal Environmental Research on September 25, 2021. The researchers collected urine samples and requested a 24 hour dietary recall (type and amount of food consumed) from over 2300 six to 19 year old participants of the 2011 – 2016 US National Health and Nutrition Examination Survey (NHANES) (FPF reported here, here, and here). They classified food and beverages into 136 groups, which they further separated into purchased from a grocery store vs. prepared at a restaurant. By reduced rank regression they related the food groups to the measured urinary concentrations of di-2-ethylhexyl phthalate (DEHP, CAS 117-81-7) and seven phthalate metabolites.
The study “found that diet explained 12.1% of the variability in urinary phthalate metabolites.” Urinary concentrations of DEHP, and three phthalate metabolites, were higher in participants with a higher intake of starchy vegetables (excluding potatoes), quick breads, and citrus juice prepared at a restaurant. In addition, “several dairy and meat food groups were associated with individual urinary phthalate metabolites.” According to the authors, dairy may make up a larger share of a child’s diet compared to adults, which could lead to higher exposure. By giving “insight into the source of high phthalate-containing foods,” the study can help to identify interventions to limit food contact with and exposure to phthalates. However, further studies are needed to analyze how phthalates get into the food.
Previous studies that used NHANES data (including data from adults) to analyze associations between food consumption and phthalate concentration reported increased urinary phthalate levels with a higher fast-food consumption (FPF reported) and with eating out compared to food preparation at home (FPF reported).
On September 29, 2021, the results of a New Zealand biomonitoring survey conducted between 2014 and 2016 on phthalate levels in children (5-18 years) and adults (20-65 years) were published in the journal International Journal of Hygiene and Environmental Health. Andrea ’t Mannetje and co-authors from Massey University, Wellington, New Zealand, analyzed ten phthalate metabolites in the urine of 600 participants and also collected demographic and dietary information. They detected metabolites of DEHP, diethyl phthalate (DEP, CAS 84-66-2), and dibutyl phthalate (DBP, CAS 84-74-2) in more than 95% of the participants with the highest geometric mean concentration of 36.1 μg/L (adults) and 60.5 μg/L (children) for the DBP metabolite monobutyl phthalate iso+n (MBP iso+n, CAS 131-70-4). For most analyzed metabolites, concentrations were higher in children than adults while levels in Māori and non-Māori were similar. Mannetje and colleagues further reported that urinary DEP and DEHP in some participants exceeded their “biomonitoring equivalents of health-based guidance values” which “indicate[s] that potential health effects from exposure to these phthalates cannot be excluded with sufficient certainty.” Connecting the concentrations with the surveyed dietary information, showed that higher levels of DEHP, MBP iso+n, and monobenzyl phthalate (MBzP, CAS 2528-16-7) were detected in participants consuming “warm meals from plastic containers ≥2 times/week.”
In a review published on September 30, 2021, in the peer-reviewed journal Environment International, J. Eales from the University of Exeter Medical School, United Kingdom, and co-authors give an overview of the human health outcomes that have been associated with such phthalate exposure. The authors searched five bibliographic databases finding 42 relevant structured reviews of epidemiological studies from which they extracted data on the number of studies included, exposure route, phthalate type and measurement method, population characteristics, and health outcomes. They also assessed the reliability of the included reviews and rated eight as “Good”, 31 as “Medium”, and three as “Low”, based on several criteria such as whether a protocol or crucial appraisal was included.
Eales et al. “found robust evidence for an association [of phthalate and phthalate metabolites exposure] with lower semen quality, neurodevelopment and risk of childhood asthma, and moderate to robust evidence for impact on anogenital distance in boys.” Moderate evidence was further identified for an association with “low birthweight, endometriosis, decreased testosterone, ADHD [attention deficit hyperactivity disorder], Type 2 diabetes and breast/uterine cancer.” Regarding evidence gaps, Eales and colleagues emphasized the complete lack of reviews focusing on phthalates from recycled plastics and their impacts on human health (FPF reported). With the current state of evidence in mind, the authors recommend researchers focus on outcomes with inconsistent or lacking results, such as malformation of testes, spontaneous abortion, time to pregnancy, as well as on reproductive effect in females which are “generally under-represented.” In addition, the overview highlights that the chemical composition of final products and the “substances of concern entering plastics waste streams via recycling” need to be given more attention.
In a comparative study, combining activity and computational analysis, Sumbul Ahmad and colleagues from the Aligarh Muslim University, Aligarh, India, analyzed the effects of the phthalates DEHP, DEP, and DBP on the human salivary aldehyde dehydrogenase (hsALDH). The enzyme hsALDH helps to maintain oral health by detoxifying aldehydes that are, for instance, used as food additives. In their study published online on September 14, 2021, in the journal Toxicology, they demonstrated that all three phthalates bind to the enzyme and inhibit its activity, with DEHP being the most potent inhibitor. The phthalates were found to bind non-covalently close to the enzyme’s catalytic site leading to structural changes of the enzyme which together contribute to the inhibition and reduced affinity for the enzyme’s substrate. The authors conclude that “exposure to phthalate plasticizers inhibits hsALDH and hence increases the risk of aldehyde caused toxicity including oral carcinogenesis, and this is expected to adversely affect the oral health of an individual.”
Ahmed, S. (2021). “A comparative study based on activity, conformation and computational analysis on the inhibition of human salivary aldehyde dehydrogenase by phthalate plasticizers: Implications in assessing the safety of packaged food items.” Toxicology. DOI: 10.1016/j.tox.2021.152947
Carwile, J., L. (2021). “Dietary correlates of urinary phthalate metabolite concentrations in 6–19 Year old children and adolescents.” Environmental Research. DOI: 10.1016/j.envres.2021.112083
Eales, J. (2021). “Human health impacts of exposure to phthalate plasticizers: An overview of reviews.” Environment International. DOI: 10.1016/j.envint.2021.106903
Mannetje, A. (2021). “Levels and determinants of urinary phthalate metabolites in New Zealand children and adults.” International Journal of Hygiene and Environmental Health. DOI: 10.1016/j.ijheh.2021.113853