Effects of Di-2-Ethylhexyl Phthalate on Central Nervous System Functions: A Narrative Review

Pollution Status, Ecological Effects, and Bioremediation Strategies of Phthalic Acid Esters in Agricultural Ecosystems: A Review

Phthalic acid esters (PAEs) are common organic contaminants in farmland soil throughout agricultural systems, posing significant threats to human health and thus closely associated with food safety concerns. Here, we consolidate the latest findings regarding the distribution, ecological effects, bioremediation methods, and microbial degradation pathways of PAEs in agricultural ecosystems. Generally, di(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DnBP), and di-isobutyl phthalate (DiBP) exhibit the highest detection frequencies and concentrations in soil, air and agricultural products. The presence of these PAEs in agricultural ecosystems can significantly affect soil and plant-associated microbial communities, leading to decreased yield and quality of agricultural products. Bioremediation techniques, such as microbial degradation and phytoremediation, are frequently explored to address these issues. Overall, this review provides a comprehensive overview of current research on PAEs in China's agricultural systems and offers insights into potential problems and future research directions.

Di(2-ethylhexyl) phthalate exposure aggravates hypoxia/reoxygenation injury in cerebral endothelial cells by downregulating epithelial cadherin expression

Di-(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer that has adverse health effects. Most phthalates exhibit reproductive toxicity and are associated with diseases such as cardiovascular disorders. However, the effect of DEHP exposure on acute hypoxia/reperfusion injury remains unknown. Therefore, we assessed whether hypoxia/reperfusion injury is aggravated by exposure to DEHP and investigated plausible underlying mechanisms, including oxidative stress and expression of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) and endothelial junctional proteins. bEnd.3 cells were exposed to DEHP and subsequently subjected to oxygen-glucose deprivation (OGD). Cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) proliferation assay. The effect of DEHP/OGD/reoxygenation (R) was evaluated by assessing the levels of NO, reactive oxygen species (ROS), and PGE2. The expression of COX-2, cleaved caspase-3, cleaved PARP, inducible nitric oxide synthase (iNOS), and the endothelial tight junction proteins claudin-5 and ZO-1 was evaluated using quantitative polymerase chain reaction and western blotting. OGD/R decreased cell viability, and DEHP exposure before OGD/R further aggravated cell viability. DEHP/OGD/R significantly increased NO, PGE2, and ROS production following OGD/R. In the DEHP/OGD/R group, iNOS, COX-2, cleaved caspase-3, and cleaved PARP expression increased, and claudin-5 and ZO-1 levels decreased compared with those in the OGD/R group. E-Cadherin expression decreased significantly after DEHP/OGD/R exposure compared with that after OGD/R; this decrease in expression was recovered by treatment with the COX-2 inhibitor indomethacin and antioxidant N-acetylcysteine. Exposure to DEHP exacerbated hypoxia-reoxygenation injury. The enhanced damage upon DEHP exposure was associated with increased oxidative stress and COX-2 expression, leading to E-cadherin downregulation and increased apoptosis.

Di (2-ethyl hexyl) phthalate and its metabolite-induced metabolic syndrome: a review of molecular mechanisms

OBJECTIVES

Metabolic disorders, as multifactorial disorders, are induced by genetic susceptibility and exposure to environmental chemicals. Di (2-ethyl hexyl) phthalate (DEHP), a ubiquitous plasticizer, is well known as an endocrine-disrupting chemical in living organisms. In recent decades, researchers have focused on the potential of DEHP and its main metabolite (Mono (2-ethylhexyl) phthalate) (MEHP) to induce metabolic disorders. In the present review, we aimed to summarize studies regarding DEHP and MEHP-induced Metabolic syndrome (MetS) as well as address the involved mechanisms.

METHODS

A search has been carried out in Google Scholar, PubMed, Scopus, and Web of Science databases using appropriate keywords including 'Metabolic syndrome' or 'Metabolic disorder' or 'Obesity' or 'Hyperglycemia' or 'Hyperlipidemia' or 'Hypertension' or 'Non-alcoholic fatty liver disease' and 'DEHP' or 'Di (2-ethyl hexyl) phthalate' or 'Bis(2-ethylhexyl) phthalate' or 'MEHP' or 'Mono (2-ethylhexyl) phthalate'. Studies were chosen based on inclusion and exclusion criteria. Inclusion criteria are in vitro, in vivo, epidemiological studies, and English-written studies. Exclusion criteria are lack of access to the full text of studies, editorial articles, review articles, and conference articles.

RESULTS

Animal studies indicate that DEHP and MEHP disrupt insulin hemostasis, increase glucose content, and induce hyperlipidemia and hypertension as well as obesity, which could lead to type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). DEHP and its metabolite induce such effects directly through influence on nuclear receptors such as peroxisome proliferator-activated receptors (PPARs) or indirectly through reactive oxygen species (ROS) production. Both events led to the disruption of several molecular signaling pathways and subsequently metabolic syndrome (MetS). Furthermore, epidemiological studies showed that there was a correlation between DEHP metabolites levels and obesity, hyperglycemia, and hypertension.

CONCLUSIONS

According to studies, DEHP and its main metabolite have the potential to induce MetS by involving various molecular mechanisms. Epidemiological studies concerning the association of DEHP and MetS in humans are not sufficient. Therefore, more studies are needed in this regard.

Maslinic acid supplementation prevents di(2-ethylhexyl) phthalate-induced apoptosis via PRDX6 in peritubular myoid cells of Chinese forest musk deer

Chinese forest musk deer (FMD), an endangered species, have exhibited low reproductive rates even in captivity due to stress conditions. Investigation revealed the presence of di(2-ethylhexyl) phthalate (DEHP), an environmental endocrine disruptor, in the serum and skin of captive FMDs. Feeding FMDs with maslinic acid (MA) has been observed to alleviate the stress response and improve reproductive rates, although the precise molecular mechanisms remain unclear. Therefore, this study aims to investigate the molecular mechanisms underlying the alleviation of DEHP-induced oxidative stress and cell apoptosis in primary peritubular myoid cells (PMCs) through MA intake. Primary PMCs were isolated and exposed to DEHP in vitro. The results demonstrated that DEHP significantly suppressed antioxidant levels and promoted cell apoptosis in primary PMCs. Moreover, interfering with the expression of PRDX6 was found to induce excessive reactive oxygen species (ROS) production and cell apoptosis in primary PMCs. Supplementation with MA significantly upregulated the expression of PRDX6, thereby attenuating DEHP-induced oxidative stress and cell apoptosis in primary PMCs. These findings provide a theoretical foundation for mitigating stress levels and enhancing reproductive capacity of in captive FMDs.

Concerted monoamine oxidase activity following exposure to di-2-ethylhexyl phthalate is associated with aggressive neurobehavioral response and neurodegeneration in zebrafish brain

Di-2-ethylhexyl phthalate (DEHP) is the most commonly preferred synthetic organic chemical in plastics and its products for making them ductile, flexible and durable. As DEHP is not chemically bound to the macromolecular polymer of plastics, it can be easily leached out to accumulate in food and environment. Our recent report advocated that exposure to DEHP significantly transformed the innate bottom-dwelling and scototaxis behaviour of zebrafish. Our present study aimed to understand the possible role of DEHP exposure pertaining towards the development of aggressive behaviour and its association with amplified monoamine oxidase activity and neurodegeneration in the zebrafish brain. As heightened monoamine oxidase (MAO) is linked with genesis of aggressive behaviour, our observation also coincides with DEHP-persuaded aggressive neurobehavioral transformation in zebrafish. Our preliminary findings also showed that DEHP epitomized as a prime factor in transforming native explorative behaviour and genesis of aggressive behaviour through oxidative stress induction and changes in the neuromorphology in the periventricular grey zone (PGZ) of the zebrafish brain. With the finding demarcating towards heightened chromatin condensation in the PGZ of zebrafish brain, our further observation by immunohistochemistry showed a profound augmentation in apoptotic cell death marker cleaved caspase 3 (CC3) expression following exposure to DEHP. Our further observation by immunoblotting study also demarcated a temporal augmentation in CC3 and tyrosine hydroxylase expression in the zebrafish brain. Therefore, the gross findings of the present study delineate the idea that chronic exposure to DEHP is associated with MAO-instigated aggressive neurobehavioral transformation and neurodegeneration in the zebrafish brain.

Early childhood exposures to phthalates in association with attention-deficit/hyperactivity disorder behaviors in middle childhood and adolescence in the ReCHARGE study

BACKGROUND

Early-life exposure to phthalates alters behaviors in animals. However, epidemiological evidence on childhood phthalate exposure and attention-deficit/hyperactivity disorder (ADHD) behaviors is limited.

METHODS

This study included 243 children from the ReCHARGE (Revisiting Childhood Autism Risks from Genetics and Environment) study, who were previously classified as having autism spectrum disorder (ASD), developmental delay, other early concerns, and typical development in the CHARGE case-control study. Twenty phthalate metabolites were measured in spot urine samples collected from children aged 2-5 years. Parents reported on children's ADHD symptoms at ages 8-18 years using Conners-3 Parent Rating Scale. Covariate-adjusted negative binomial generalized linear models were used to investigate associations between individual phthalate metabolite concentrations and raw scores. Weighted quantile sum (WQS) regression with repeated holdout validation was used to examine mixture effects of phthalate metabolites on behavioral scores. Effect modification by child sex was evaluated.

RESULTS

Among 12 phthalate metabolites detected in >75% of the samples, higher mono-2-heptyl phthalate (MHPP) was associated with higher scores on Inattentive (β per doubling = 0.05, 95% confidence interval [CI]: 0.02, 0.08) and Hyperactive/Impulsive scales (β = 0.04, 95% CI: 0.00, 0.07), especially among children with ASD. Higher mono-carboxy isooctyl phthalate (MCiOP) was associated with higher Hyperactivity/Impulsivity scores (β = 0.07, 95% CI: -0.01, 0.15), especially among typically developing children. The associations of the molar sum of high molecular weight (HMW) phthalate metabolites and a phthalate metabolite mixture with Hyperactivity/Impulsivity scores were modified by sex, showing more pronounced adverse associations among females.

CONCLUSION

Exposure to phthalates during early childhood may impact ADHD behaviors in middle childhood and adolescence, particularly among females. Although our findings may not be broadly generalizable due to the diverse diagnostic profiles within our study population, our robust findings on sex-specific associations warrant further investigations.

Association of exposure to phthalates and phthalate alternatives with dyslexia in Chinese primary school children

Previous studies have shown associations between children's exposure to phthalates and neurodevelopmental disorders. Whereas the impact of exposure to phthalate alternatives is understudied. This study aimed to evaluate the association of exposure to phthalates/their alternatives with the risk of dyslexia. We recruited 745 children (355 dyslexia and 390 non-dyslexia) via the Tongji Reading Environment and Dyslexia Research Project, and their urine samples were collected. A total of 26 metabolites of phthalates/their alternatives were measured. Multivariate logistic regression and quantile-based g-computation were used to estimate the associations of exposure to the phthalates/their alternatives with dyslexia. More than 80% of the children had 17 related metabolites detected in their urine samples. After adjustment, the association between mono-2-(propyl-6-hydroxy-heptyl) phthalate (OH-MPHP) with the risk of dyslexia was observed. Compared with the lowest quartile of OH-MPHP levels, the odds of dyslexia for the third quartile was 1.93 (95% CI 1.06, 3.57). Regarding mixture analyses, it was found that OH-MPHP contributed the most to the association. Further analyses stratified by sex revealed that this association was only observed in boys. Our results suggested a significantly adverse association of di-2-propylheptyl phthalate exposure with children's language abilities. It highlights the necessity to prioritize the protection of children's neurodevelopment by minimizing their exposure to endocrine-disrupting chemicals like di-2-propylheptyl phthalate.

Maternal exposure to di-(2-ethylhexyl) phthalate impaired the social interaction via activating microglia in male pups

Di-(2-ethylhexyl) phthalate (DEHP), a common endocrine-disrupting chemical (EDC), is widely used in daily articles, early exposure to DEHP is associated with many behavioral changes in pups. This study aimed to investigate the effects and underlying mechanisms of maternal exposure to DEHP on the impaired social interaction in pups. Pregnant rats were administered 0, 30, 300, or 750 mg/kg/d DEHP daily by oral gavage. Highly aggressive proliferating immortalized (HAPI) cells were treated with mono-(2-ethylhexyl) phthalate (MEHP) and tyrosine phosphorylation inhibitor (AG490). Our results showed that DEHP exposure induced the activation of microglias (MGs) via activating the janus kinase 2 / signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway, and increased the level of pro-inflammatory factors, then impaired the social behavior in male pups, but not female pups. Moreover, MEHP exposure could also activate HAPI via activating this signaling pathway, and AG490 could inhibit the activation of this signaling pathway caused by MEHP. Therefore, we indicated that maternal exposure to DEHP could cause the gender-specific impaired social interaction in pups that might be related to the activation of MGs.

Di-2-ethylhexyl phthalate disrupts hepatic lipid metabolism in obese mice by activating the LXR/SREBP-1c and PPAR-α signaling pathways

Di-2-ethylhexyl phthalate (DEHP), a widely utilized plasticizer, has been described as a potential obesogen based on in vivo disruption of hepatic lipid homeostasis and in vitro promotion of lipid accumulation. However, limited literature exists regarding the specific ramifications of DEHP exposure on obese individuals, and the precise mechanisms underlying the adverse effects of DEHP exposure remain unclear. This study aimed to assess the impact of DEHP on hepatic lipid metabolism in obese mice by comparing them to normal mice. Following a 10-week DEHP exposure period, the obese mice exhibited higher blood lipid levels, more severe hepatic steatosis, and more infiltrations of inflammatory cells in liver tissue than normal mice. Interestingly, the body weight of the mice exhibited no significant alteration. In addition, transcriptomic analyses revealed that both lipogenesis and fatty acid oxidation contributed to hepatic lipid metabolism dysregulation following DEHP exposure. More specifically, alterations in the transcription of genes associated with hepatic lipid metabolism were linked to the different responses to DEHP exposure observed in normal and obese mice. Additionally, the outcomes of in vitro experiments validated the in vivo findings and demonstrated that DEHP exposure could modify hepatic lipid metabolism in normal mice by activating the LXR/SREBP-1c signaling pathway to promote lipogenesis. At the same time, DEHP exposure led to inhibition of the Camkkβ/AMPK pathway to suppress β-fatty acid oxidation. Conversely, in obese mice, DEHP exposure was found to be associated with the stimulation of both lipogenesis and fatty acid oxidation via activation of the LXR/SREBP-1c and PPAR-α signaling pathways, respectively. The findings presented in this study first elucidate the contrasting mechanisms underlying DEHP-induced liver damage in obese and normal mice, thereby offering valuable insights into the pathogenesis of DEHP-induced liver damage in individuals with obesity.

Regulation of BTB (POZ) Structural Domain 6b by MicroRNA-222b in Zebrafish Embryos after Exposure to Di(2-ethylhexyl)phthalate at Low Concentrations

Di-(2-ethylhexyl) phthalate (DEHP) is a sort of endocrine disruptor that induces abnormal physiological and biochemical activities such as epigenetic alterations, apoptosis, and oxidative stress. MicroRNAs (miRNAs) are a class of short noncoding RNAs that may regulate the expression of many protein-coding genes when organisms are exposed to environmental chemicals. miR-222b is a differentially expressed miRNA after DEHP exposure. miRNA-mRNA prediction suggested that BTB (POZ) structural domain 6b (BTBD6B) might be a target mRNA of miR-222b, and DEHP exposure altered its expression. However, the correlation between miR-222b and BTBD6B has not been experimentally confirmed. The aim of this study was to investigate the regulation of BTBD6B by miR-222b in zebrafish embryos under the effect of low concentration of DEHP. Dual fluorescent protein assays and dual luciferase reporter gene assays confirmed the interaction between miR-222b and the 3'-untranslated region (3'-UTR) of BTBD6B. Ectopic expression assays showed that miR-222b could negatively regulate BTBD6B in ZF4 cells. However, the relative expression of miR-222b and BTBD6B was significantly higher at both transcriptional and post-transcriptional levels in zebrafish embryos exposed to low concentrations of DEHP. The results of this study improved our understanding of the molecular mechanism of DEHP exposure toxicity. It identified that the aberrant expression of miR-222b/BTBD6B may be one of the mechanisms of DEHP toxicity, which can provide a theoretical reference and scientific basis for environmental management and biological health risk assessment.

Di (2-ethylhexyl) phthalate alters neurobehavioral responses and oxidative status, architecture, and GFAP and BDNF signaling in juvenile rat's brain: Protective role of Coenzyme10

Di-(2-ethylhexyl) phthalate (DEHP), a phthalate plasticizer, is widely spread in the environment, presenting hazards to human health and food safety. Hence, this study examined the probable preventive role of coenzyme10 (CQ10) (10 mg/kg.b.wt) against DEHP (500 mg/kg.wt) - induced neurotoxic and neurobehavioral impacts in juvenile (34 ± 1.01g and 3 weeks old) male Sprague Dawley rats in 35-days oral dosing trial. The results indicated that CQ10 significantly protected against DEHP-induced memory impairment, anxiety, depression, spatial learning disorders, and repetitive/stereotypic-like behavior. Besides, the DEHP-induced depletion in dopamine and gamma amino butyric acid levels was significantly restored by CQ10. Moreover, CQ10 significantly protected against the exhaustion of CAT, GPx, SOD, GSH, and GSH/GSSG ratio, as well as the increase in malondialdehyde, Caspas-3, interleukin-6, and tumor necrosis factor-alpha brain content accompanying with DEHP exposure. Furthermore, CQ10 significantly protected the brain from the DEHP-induced neurodegenerative alterations. Also, the increased immunoexpression of brain-derived neurotrophic factor, not glial fibrillary acidic protein, in the cerebral, hippocampal, and cerebellar brain tissues due to DEHP exposure was alleviated with CQ10. This study's findings provide conclusive evidence that CQ10 has the potential to be used as an efficient natural protective agent against the neurobehavioral and neurotoxic consequences of DEHP.

MEHP activates JNK to inhibit the migration of human foreskin fibroblasts

This study aimed to investigate the impact of mono(2-ethylhexyl) phthalate (MEHP) on the proliferation, apoptosis, and migration of human foreskin fibroblast cells (HFF-1) and the role of the JNK signaling pathway in cell migration. HFF-1 cells were randomly assigned to the control group with 0 MEHP exposure (M0) or the experimental groups with 25, 50, 100, 200, and 400 μmol/L MEHP exposure (M25, M50, M100, M200, and M400, respectively). After 24 and 48 h of MEHP exposure, the proliferation of HFF-1 cells in any group had no significant change. However, compared with the M0 group, the M200 and M400 groups presented substantially increased apoptosis of HFF-1 cells. Moreover, cell migration ability significantly decreased in all groups (p < 0.05). Additionally, the transcription and phosphorylated protein activation of JNK kinase in HFF-1 cells were substantially upregulated with the increase in MEHP exposure. Subsequently, HFF-1 cells were randomly divided into three groups: the DMSO blank control group, the 100 μM MEHP experimental group (M100), and the 100 μM MEHP plus 10 μM SP600125 (specific JNK inhibitor) experimental group (S10). The activation of JNK protein in HFF-1 cells was substantially downregulated in the S10 group. HFF-1 cells were also divided into the blank control group (M0). They were treated with 100 μM MEHP and varying concentrations of SP600125 (5, 10, and 15 μM for S5, S10, and S15, respectively). As the concentration of the antagonist increased, the migration ability of HFF-1 cells was returned to normal. Finally, the ROS in HFF-1 cells increased under MEHP exposure. This finding indicates that the regulation of cell migration by the JNK signaling pathway may be important in the occurrence of hypospadias.

Lycopene Prevents Phthalate-Induced Cognitive Impairment via Modulating Ferroptosis

Di-(2-ethylhexyl) phthalate (DEHP) is frequently used as a plasticizer in industrial and agricultural products. DEHP can cause severe neurotoxicity, such as impaired learning and memory function. Lycopene (LYC) as a carotenoid exerts excellent antioxidant capacity and therapeutic effects in neurodegenerative diseases. However, whether LYC can prevent the cognitive impairment induced by DEHP and the specific mechanisms are unclear. In the present study, the behavioral test results suggested that LYC alleviated the learning and memory impairment induced by DEHP. The histopathological data revealed that LYC attenuated DEHP-induced disordered arrangement of the neurons in the CA1 and CA3 regions of the hippocampus tissue. Moreover, LYC inhibited the occurrence of DEHP-induced ferroptosis via regulating iron metabolism, inhibiting lipid peroxidation, and activating the cysteine transporter and nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (NrF2/HO-1) signaling pathway. Overall, the study contributes novel perspectives into the potential mechanisms of LYC preventing phthalate-induced cognitive impairment in the hippocampus.

MiR-93 alleviates DEHP plasticizer-induced neurotoxicity by negatively regulating TNFAIP1 and inhibiting ubiquitin-mediated degradation of CK2β

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is widely used in various products, such as plastic packaging in food industries. As an environmental endocrine disruptor, it induces adverse effects on brain development and function. However, the molecular mechanisms by which DEHP induces learning and memory impairment remain poorly understood. Herein, we found that DEHP impaired learning and memory in pubertal C57BL/6 mice, decreased the number of neurons, downregulated miR-93 and the β subunit of casein kinase 2 (CK2β), upregulated tumor necrosis factor-induced protein 1 (TNFAIP1), and inhibited Akt/CREB pathway in mouse hippocampi. Coimmunoprecipitation and western blotting assays revealed that TNFAIP1 interacted with CK2β and promoted its degradation by ubiquitination. Bioinformatics analysis showed a miR-93 binding site in the 3'-untranslated region of Tnfaip1. A dual-luciferase reporter assay revealed that miR-93 targeted TNFAIP1 and negatively regulated its expression. MiR-93 overexpression prevented DEHP-induced neurotoxicity by downregulating TNFAIP1 and then activating CK2/Akt/CREB pathway. These data indicate that DEHP upregulates TNFAIP1 expression by downregulating miR-93, thus promoting ubiquitin-mediated degradation of CK2β, subsequently inhibiting Akt/CREB pathway, and finally inducing learning and memory impairment. Therefore, miR-93 can relieve DEHP-induced neurotoxicity and may be used as a potential molecular target for prevention and treatment of related neurological disorders.

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.

Behavioral Effects of Exposure to Phthalates in Female Rodents: Evidence for Endocrine Disruption?

Phthalates have been widely studied for their reprotoxic effects in male rodents and in particular on testosterone production, for which reference doses were established. The female rodent brain can also represent a target for exposure to these environmental endocrine disruptors. Indeed, a large range of behaviors including reproductive behaviors, mood-related behaviors, and learning and memory are regulated by sex steroid hormones. Here we review the experimental studies addressing the effects and mechanisms of phthalate exposure on these behaviors in female rodents, paying particular attention to the experimental conditions (period of exposure, doses, estrous stage of analyses etc.). The objective of this review is to provide a clear picture of the consistent effects that can occur in female rodents and the gaps that still need to be filled in terms of effects and mode(s) of action for a better risk assessment for human health.