Indoor exposure to phthalates and its burden of disease in China

Impaired energy metabolism and altered brain histoarchitecture characterized by inhibition of glycolysis and mitochondrial electron transport-linked enzymes in rats exposed to diisononyl phthalate

The brain is an energy demanding organ, constituting about 20 % of the body's resting metabolic rate. An efficient energy metabolism is critical to neuronal functions. Glucose serves as the primary essential energy source for the adult brain and plays a critical role in supporting neural growth and development. Endocrine disrupting chemicals (EDCs) such as phthalates has been shown to have a negative impact on neurological functions. The impact of diisononyl phthalate (DiNP) on neural energy transduction using cellular energy metabolizing enzymes as indicators was examined. Over the course of 14 days, eighteen (18) albino rats divided into three groups (1,2 and 3) of six albino rats were given Tween-80/saline, 20 and 200 mg/kg body weight respectively. In the brain, we assessed histological changes as well as activities of selected enzymes of energy metabolism such as the glycolytic pathway, citric acid cycle and mitochondrial electron transport-linked complexes. Activities of the glycolytic and TCA cycle enzymes assayed were significantly decreased except citrate synthase activity with no statistically significant change following the administration of DiNP. Also, respiratory chain complexes (Complex I-IV) activities were significantly reduced when compared to control. DiNP exposure altered the histological integrity of various brain sections. These include degenerated Purkinje neurons, distortion of the granular layer and Purkinje cell layer. Data from this study indicated impaired brain energy metabolism via down-regulation of enzymes of cellular respiration of the glycolytic and oxidative phosphorylation pathways and altered brain histoarchitecture orchestrated by DiNP exposure.

Analysis and remediation of phthalates in aquatic matrices: current perspectives

Phthalic acid esters (PAEs) are high production volume chemicals used extensively as plasticizers, to increase the flexibility of the main polymer. They are reported to leach into their surroundings from plastic products and are now a ubiquitous environmental contaminant. Phthalate levels have been determined in several environmental matrices, especially in water. These levels serve as an indicator of plasticizer abuse and plastic pollution, and also serve as a route of exposure to different species including humans. Reports published on effects of different PAEs on experimental models demonstrate their carcinogenic, teratogenic, reproductive, and endocrine disruptive effects. Therefore, regular monitoring and remediation of environmental water samples is essential to ascertain their hazard quotient and daily exposure levels. This review summarises the extraction and detection techniques available for phthalate analysis in water samples such as chromatography, biosensors, immunoassays, and spectroscopy. Current remediation strategies for phthalate removal such as adsorption, advanced oxidation, and microbial degradation have also been highlighted.

The necroptosis-mediated imbalance of mitochondrial dynamics is involved in DEHP-induced toxicity to immature testes via the PGAM5-DRP1 interaction

Di-(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer that has been shown to impair male reproduction, but the potential mechanism underlying testicular injury caused by DEHP remains unclear. In vivo, rats were gavaged consecutively from postnatal day (PND) 21 to PND 31 with 0, 250, or 500 mg/kg DEHP for 10 days, and impaired mitochondria and increased necroptosis were observed in immature testes. In vitro, the GC-1 and GC-2 cell lines were exposed to monoethylhexyl phthalate (MEHP) at 100, 200 and 400 μM for 24 h, and this exposure induced oxidative stress damage, necroptosis and mitochondrial injury. Necroptosis and mitochondrial fission were inhibited by the reactive oxygen species (ROS) inhibitor acetylcysteine, and the imbalanced mitochondrial dynamics were rescued by the RIPK1 inhibitor necrostatin-1. Colocalization and co-IP analyses confirmed an interaction between dynamin-related protein 1 (DRP1) and phosphoglycerate mutase 5 (PGAM5), indicating that PGAM5 dephosphorylates DRP1 at serine 637 to induce mitochondrial fragmentation and thereby induces germ cell damage. Drug prediction with Connectivity Map (cMap) identified sulforaphane as a therapeutic drug. In summary, our findings indicate that DEHP triggers necroptosis and mitochondrial injury via a ROS storm in immature testes and that the PGAM5-DRP1 interaction is involved in this process.

Association of maternal phthalates exposure and metabolic gene polymorphisms with congenital heart diseases: a multicenter case-control study

BACKGROUND

The majority of congenital heart diseases (CHDs) are thought to result from the interactions of genetics and the environment factors. This study aimed to assess the association of maternal non-occupational phthalates exposure, metabolic gene polymorphisms and their interactions with risk of CHDs in offspring.

METHODS

A multicenter case-control study of 245 mothers with CHDs infants and 268 control mothers of health infant was conducted from six hospitals. Maternal urinary concentrations of eight phthalate metabolites were measured by ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Twenty single nucleotide polymorphisms (SNPs) in cytochrome P450 family 2 subfamily C member 9 (CYP2C9) and 19 (CYP2C19), uridine diphosphate (UDP) glucuronosyl transferase family 1 member A7 (UGT1A7), family 2 member B7 (UGT2B7) and B15(UGT2B15) genes were genotyped. The multivariate logistic regressions were used to estimate the association between maternal phthalates exposure or gene polymorphisms and risk of CHDs. Generalized multifactor dimensionality reduction (GMDR) was used to analyze the gene-gene and gene-phthalates exposure interactions.

RESULTS

There was no significant difference in phthalate metabolites concentrations between the cases and controls. No significant positive associations were observed between maternal exposure to phthalates and CHDs. The SNPs of UGT1A7 gene at rs4124874 (under three models, log-additive: aOR = 1.74, 95% CI:1.28-2.37; dominant: aOR = 1.86, 95% CI:1.25-2.78; recessive: aOR = 2.50, 95% CI: 1.26-4.94) and rs887829 (under the recessive model: aOR = 13.66, 95% CI: 1.54-121) were significantly associated with an increased risk of CHDs. Furthermore, the associations between rs4124874 (under log-additive and dominant models) of UGT1A7 were statistically significant after the false discovery rate correction. No significant gene-gene or gene-phthalate metabolites interactions were observed.

CONCLUSIONS

The polymorphisms of maternal UGT1A7 gene at rs4124874 and rs887829 were significantly associated with an increased risk of CHDs. More large-scale studies or prospective study designs are needed to confirm or refute our findings in the future.

Multi-source exposure and health risks of phthalates among university students in Northeastern China

The endocrine disruptor phthalates (PAEs) are widely used as important chemical additives in a variety of areas around the globe. PAEs are toxic to reproduction and development and may adversely affect the health of adolescents. Risk assessments of exposure to PAEs from different sources are more reflective of actual exposure than single-source assessments. We used personal exposure parameters to estimate the dose of PAEs to 107 university students from six media (including dormitory dust, dormitory air, clothing, food, disposable food containers, and personal care products (PCPs)) and three exposure routes (including ingestion, inhalation, and dermal absorption). Individual factors and lifestyles may affect PAE exposure to varying degrees. Based on a positive matrix factorization (PMF) model, the results indicated that the main sources of PAEs in dust were indoor building materials and plastics, while PCPs and adhesives were the major sources of airborne PAEs. The relative contribution of each source to PAE exposure showed that food and air were the primary sources of dimethyl phthalate (DMP) and dibutyl phthalate (DBP). Air source contributed the most to diethyl phthalate (DEP) exposure, followed by PCPs. Food was the most significant source of diisobutyl phthalate (DiBP), benzyl butyl phthalate (BBP), and bis(2-ethylhexyl) phthalate (DEHP) exposure. Additionally, the exposure of DEHP to dust was not negligible. The ingestion pathway was the most dominant among the three exposure pathways, followed by dermal absorption. The non-carcinogenic risk of PAEs from the six sources was within acceptable limits. DEHP exhibits a low carcinogenic risk. We suggest university students maintain good hygienic and living habits to minimize exposure to PAEs.

Comprehensive assessment of phthalates in indoor dust across China between 2007 and 2019: Benefits from regulatory restrictions

China is the largest producer and consumer of phthalates in the world. However, it remains unclear whether China's phthalate restrictions have alleviated indoor phthalate pollution. We extracted the concentrations of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), benzyl butyl phthalate (BBP), and bis(2-ethylhexyl) phthalate (DEHP) in indoor dust at 2762 sites throughout China between 2007 and 2019 from the published literature. Based on these data, we investigated the effects of phthalate restrictions and environmental factors on the temporal-spatial distribution and sources of phthalates and estimated human exposure and risk of phthalates. The results revealed that the mean concentrations of phthalates in indoor dust throughout China decreased in the following order: DEHP > DBP > DIBP > DMP > DEP > BBP. The concentrations of six phthalates were generally higher in northern and central-western China than in southern regions. BBP and DEHP concentrations decreased by 73.5% and 17.9%, respectively, from 2007 to 2019. Sunshine was a critical environmental factor in reducing phthalate levels in indoor dust. Polyvinyl chloride materials, personal care products, building materials, and furniture were the primary sources of phthalates in indoor dust. The phthalates in indoor dust posed the most significant threat to children and older adults. This study provides a picture of phthalate pollution, thus supporting timely and effective policies and legislation.

Harm from Residential Indoor Air Contaminants

This study presents a health-centered approach to quantify and compare the chronic harm caused by indoor air contaminants using disability-adjusted life-year (DALY). The aim is to understand the chronic harm caused by airborne contaminants in dwellings and identify the most harmful. Epidemiological and toxicological evidence of population morbidity and mortality is used to determine harm intensities, a metric of chronic harm per unit of contaminant concentration. Uncertainty is evaluated in the concentrations of 45 indoor air contaminants commonly found in dwellings. Chronic harm is estimated from the harm intensities and the concentrations. The most harmful contaminants in dwellings are PM2.5, PM10-2.5, NO2, formaldehyde, radon, and O3, accounting for over 99% of total median harm of 2200 DALYs/105 person/year. The chronic harm caused by all airborne contaminants in dwellings accounts for 7% of the total global burden from all diseases.

The burden of disease attributable to indoor air pollutants in China from 2000 to 2017

BACKGROUND

High-level exposure to indoor air pollutants (IAPs) and their corresponding adverse health effects have become a public concern in China in the past 10 years. However, neither national nor provincial level burden of disease attributable to multiple IAPs has been reported for China. This is the first study to estimate and rank the annual burden of disease and the financial costs attributable to targeted residential IAPs at the national and provincial level in China from 2000 to 2017.

METHODS

We first did a systematic review and meta-analysis of 117 articles from 37 231 articles identified in major databases, and obtained exposure-response relationships for the candidate IAPs. The exposure levels to these IAPs were then collected by another systematic review of 1864 articles selected from 52 351 articles. After the systematic review, ten IAPs with significant and robust exposure-response relationships and sufficient exposure data were finally targeted: PM2·5, nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide, radon, formaldehyde, benzene, toluene, and p-dichlorobenzene. The annual exposure levels in residences were then evaluated in all 31 provinces in mainland China continuously from 2000 to 2017, using the spatiotemporal Gaussian process regression model to analyse indoor originating IAPs, and the infiltration factor method to analyse outdoor originating IAPs. The disability-adjusted life-years (DALYs) attributable to the targeted IAPs were estimated at both national and provincial levels in China, using the population attributable fraction method. Financial costs were estimated by an adapted human capital approach.

FINDINGS

From 2000 to 2017, annual DALYs attributable to the ten IAPs in mainland China decreased from 4620 (95% CI 4070-5040) to 3700 (3210-4090) per 100 000. Nevertheless, in 2017, IAPs still ranked third among all risk factors, and their DALYs and financial costs accounted for 14·1% (95% CI 12·3-15·6) of total DALYs and 3·45% (3·01-3·82) of the gross domestic product. Specifically, the rank of ten targeted IAPs in order of their contribution to DALYs in 2017 was PM2·5, carbon monoxide, radon, benzene, nitrogen dioxide, ozone, sulphur dioxide, formaldehyde, toluene, and p-dichlorobenzene. The DALYs attributable to IAPs were 9·50% higher than those attributable to outdoor air pollution in 2017. For the leading IAP, PM2·5, the DALYs attributable to indoor origins are 18·3% higher than those of outdoor origins.

INTERPRETATION

DALYs attributed to IAPs in China have decreased by 20·0% over the past two decades. Even so, they are still much higher than those in the USA and European countries. This study can provide a basis for determining which IAPs to target in various indoor air quality standards and for estimating the health and economic benefits of various indoor air quality control approaches, which will help to reduce the adverse health effects of IAPs in China.

FUNDING

The National Key Research and Development Program of China and the National Natural Science Foundation of China.

Di(2-ethylhexyl) phthalate induces reproductive toxicity and transgenerational reproductive aging in Caenorhabditis elegans

With the large-scale production and use of plastic products, the global plastic pollution problem is becoming more and more serious. The plasticizer di (2-ethylhexyl) phthalate (DEHP), which is widely used in the production of plastics, has caused great concern for the health of the population. Exposure of organisms to DEHP can cause a variety of health damage, of which reproductive system damage is an important part. At present, there are still few studies on DEHP in reproductive aging, and it is of great significance to explore the role of DEHP in promoting reproductive aging and its underlying mechanism. In this study, the model organism Caenorhabditis elegans (C. elegans) was used to preliminarily explore the mechanism of DEHP-induced female reproductive senescence. The results showed that DEHP reduced the number of offspring and gonad area of C. elegans, resulting in shortened reproductive and life span, abnormal phenotypes in somatic gonad structure including the Emo phenotype, the BOW phenotype, a twisted gonad arm, and atrophied oocytes. Biochemical studies showed that DEHP promoted oxidative stress and autophagy in C. elegans. Further, we found the decreased number of offspring, malformed somatic gonad structure, oxidative damage and autophagy induced by DEHP in parental worms can be inheritance to the not directly exposed offspring.

Association between phthalate exposure and obesity risk: A meta-analysis of observational studies

According to epidemiological studies, phthalate exposure is associated with an increased risk of obesity in children and adults; however, these observations remain debatable. Therefore, we performed a systematic review and meta-analysis of the current literature to explore the effects of phthalate exposure on obesity. A systematic search was performed from inception to July 2022 in PubMed, EMBASE, Scopus, and Web of Science. Quality assessment was completed using criteria modified from Newcastle-Ottawa Scale (NOS) for the included studies. Meta-analysis showed that childhood exposure to MnBP, MBP, MEP, MiBP, and MECPP was positively correlated with obesity. In adults, MMP, MEP, and MiBP were positively correlated with adult abdominal obesity, while MEHHP, MECPP, and MCOP were positively correlated with adult general obesity. Subgroup analysis revealed that the positive correlation was particularly significant in women, as well as in Europe and the United States. Overall, a substantial association exists between phthalate exposure and obesity in children and adults. Sex and study site may provide limited sources of heterogeneity.

Secondary oxidized di-2-ethylhexyl phthalate metabolites may be associated with progression from isolated premature thelarche to central precocious or early puberty

Phthalate esters (PAEs) may act as estrogen receptor agonists, and their relationship with precocious puberty is a global health concern. However, their role in isolated premature thelarche (IPT) progression remains unclear. We conducted a cohort study investigating the relationship between IPT progression and urinary PAE metabolites. Girls with IPT aged 6-8 years were regularly followed up every three months for one year. Clinical data and urine PAE metabolite levels were collected. Participants who progressed to central precocious puberty (CPP) or early puberty (EP) had significantly higher ovarian volume, breast Tanner stage, and levels of the creatinine-adjusted urinary secondary oxidized di-2-ethylhexyl phthalate (DEHP) metabolites (Σ₄DEHP). Breast Tanner stage (odds ratio [OR] = 7.041, p = 0.010), ovarian volume (OR = 3.603, p = 0.019), and Σ₄DEHP (OR = 1.020, p = 0.005) were independent risk factors for IPT progression. For each 10 µg/g/Cr increase in the urine level of Σ₄DEHP, the risk of progression from IPT to CPP/EP within one year increased by 20%. This study demonstrated that the breast Tanner stage, ovarian volume, and Σ₄DEHP in urine were independent risk factors for IPT progression, and Σ₄DEHP may be associated with the progression of IPT to CPP or EP.

Di-(2-ethylhexyl) phthalate exposure impairs cortical development in hESC-derived cerebral organoids

Di-(2-ethylhexyl) phthalate (DEHP), a ubiquitous environmental endocrine disruptor, is widely used in consumer products. Increasing evidence implies that DEHP influences the early development of the human brain. However, it lacks a suitable model to evaluate the neurotoxicity of DEHP. Using an established human cerebral organoid model, which reproduces the morphogenesis of the human cerebral cortex at the early stage, we demonstrated that DEHP exposure markedly suppressed cell proliferation and increased apoptosis, thus impairing the morphogenesis of the human cerebral cortex. It showed that DEHP exposure disrupted neurogenesis and neural progenitor migration, confirmed by scratch assay and cell migration assay in vitro. These effects might result from DEHP-induced dysplasia of the radial glia cells (RGs), the fibers of which provide the scaffolds for cell migration. RNA sequencing (RNA-seq) analysis of human cerebral organoids showed that DEHP-induced disorder in cell-extracellular matrix (ECM) interactions might play a pivotal role in the neurogenesis of human cerebral organoids. The present study provides direct evidence of the neurodevelopmental toxicity of DEHP after prenatal exposure.

Association between phthalate exposure and accelerated bone maturation in Chinese girls with early puberty onset: a propensity score-matched case-control analysis

Estrogen can promote the acceleration of bone maturation and phthalate esters (PAEs) have estrogen-mimicking effects. We investigated whether PAEs are associated with the acceleration of bone age (BA) in girls with early onset of puberty (EOP). This case–control study enrolled 254 girls with EOP from the Endocrinology Department at Shenzhen Children’s Hospital between December 2018 and August 2019. Ultra-performance liquid chromatography and tandem mass spectrometry were used to analyze the 10 metabolites of PAEs (mPAEs) in urine samples. BA was measured using an artificial intelligence system. BA exceeding the chronological age (CA) by > 2 years (BA-CA ≥ 2 years) was referred to as significant BA advancement. Participants were divided into groups A (BA-CA ≥ 2 years; case group) and B (BA-CA < 2 years; control group). Propensity score matching (PSM) was performed for both groups in a 1:2 ratio with a caliper of 0.25. To identify potential dose–response relationships between PAEs exposure and BA advancement, we grouped the participants after PSM according to the tertiles of the mPAE concentrations. After PSM, 31 and 62 girls in groups A and B were selected. The concentration of Mono-ethyl phthalate (MEP) in group A was significantly higher than in group B (11.83 μg/g vs. 7.11 μg/g, P < 0.05); there was no significant difference in the levels of other mPAEs between the groups. The degree of BA advancement and proportion of significantly advanced BA in the lowest, middle, and highest tertiles of the MEP sequentially increased, as well as in the lowest, middle, and highest tertiles of Mono-(2-ethyl-5-carboxypentyl) phthalate; however, these were only statistically different between the highest and lowest MEP tertiles (both P < 0.05). For the remaining mPAEs, differences in the degree of BA advancement among the lowest, middle, and highest tertiles, as well as differences in the proportion of significantly advanced BA among the lowest, middle, and highest tertiles, were not significant (all P > 0.05). Our findings suggested that MEP was positively associated with BA advancement in girls with EOP. Exposure to PAEs may promote accelerated bone maturation.