Early-life exposure to Tris(1,3-dichloroisopropyl) phosphate induces dose-dependent suppression of sexual behavior in male rats

Organophosphate Flame Retardants in Pregnant Women: Sources, Occurrence, and Potential Risks to Pregnancy Outcomes

Organophosphate flame retardants (OPFRs) are found in various environmental matrixes and human samples. Exposure to OPFRs during gestation may interfere with pregnancy, for example, inducing maternal oxidative stress and maternal hypertension during pregnancy, interfering maternal and fetal thyroid hormone secretion and fetal neurodevelopment, and causing fetal metabolic abnormalities. However, the consequences of OPFR exposure on pregnant women, impact on mother-to-child transmission of OPFRs, and harmful effects on fetal and pregnancy outcomes have not been evaluated. This review describes the exposure to OPFRs in pregnant women worldwide, based on metabolites of OPFRs (mOPs) in urine for prenatal exposure and OPFRs in breast milk for postnatal exposure. Predictors of maternal exposure to OPFRs and variability of mOPs in urine have been discussed. Mother-to-child transmission pathways of OPFRs have been scrutinized, considering the levels of OPFRs and their metabolites in amniotic fluid, placenta, deciduae, chorionic villi, and cord blood. The results showed that bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP) were the two predominant mOPs in urine, with detection frequencies of >90%. The estimated daily intake (EDI_M) indicates low risk when infants are exposed to OPFRs from breast milk. Furthermore, higher exposure levels of OPFRs in pregnant women may increase the risk of adverse pregnancy outcomes and influence the developmental behavior of infants. This review summarizes the knowledge gaps of OPFRs in pregnant women and highlights the crucial steps for assessing health risks in susceptible populations, such as pregnant women and fetuses.

Urinary concentrations of organophosphate esters in relation to semen quality: A cross-sectional study

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers in consumer products. Toxicological studies have indicated that OPEs may affect male reproductive health, but human evidence is inconclusive. In this study, we explored associations of individual and mixtures of OPE exposure with semen quality among 1015 Chinese men from an infertility clinic. After adjusting for potential confounders, we observed that higher diphenyl phosphate (DPHP) and [Bis(2-methylphenyl) phosphate (BMPP)] exposure was associated with increased odds ratios (ORs) of having below-reference total sperm count. Higher bis (2-butoxyethyl) phosphate (BBOEP) exposure was associated with increased ORs of having below-reference progressive motility and total motility. For semen quality parameters modeled as continuous outcomes, inverse associations with individual OPE were still observed. In addition, urinary 1-hydroxy-2-propyl bis (1-chloro-2-propyl) phosphate (BCIPHIPP) concentrations were inversely associated with the percentage of normal morphology while positively associated with the percentage of abnormal heads. Quantile g-computation regression analyses showed that exposure to higher OPE mixtures was associated with lower total sperm motility and normal morphology. Our results indicated that both individual and mixtures of OPE exposure were associated with reduced semen quality.

Toxicological effects of Tris (1,3-dichloro-2-propyl) phosphate exposure in adult male rats differ depending on the history of exposure in the neonatal period

There is increasing concern about multiple high concentration exposure to toxins in disaster and emergency situations. However, conventional toxicology testing methods may not adequately address these situations. Thus, we assessed whether the toxic effects of exposure in the adulthood differ depending on the presence or absence of neonatal exposure to Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) in male rats to investigate the effects of exposure history of chemicals. In the neonatal stage [postnatal days (PNDs) 1-7], animals were treated with either sesame oil (5 ml/kg/day) as a control or TDCIPP (250 mg/kg/day) dissolved in sesame oil. In adulthood (PND 101-107), animals were treated with either sesame oil (5 ml/kg/day) or TDCIPP (650 mg/kg/day). One day after the final administration, dissection was performed, and body and organ weight, hematology, blood biochemistry and histopathology were examined. The results demonstrated that the toxic effects of TDCIPP exposure in adulthood on adrenal gland size, serum iron content, and unsaturated iron binding capacity were enhanced by TDCIPP exposure in the neonatal stage. From these findings, it was indicated that the toxic effects of TDCIPP exposure in the adult stage are affected by pediatric exposure. These results suggest that the toxic effects of high-dose and long-term unsteady exposure to chemicals in large-scale disasters may change based on the exposure history of chemicals.

Effects of tris(1,3-dichloro-2-propyl) phosphate on epididymal sperm parameters in adult male rats

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is widely used as a flame retardant and is known to exhibit anti-androgenic effects in vitro and in vivo. To assess the reproductive toxicity potency of TDCIPP, we investigated the effects of 7 days of TDCIPP oral administration on epididymal sperm motion and concentration in adult male Wistar-Imamichi rats. Thirty-five days after the final administration, sperm parameters were evaluated by computer-assisted sperm analysis. Results showed that sperm swimming progression and vigor and sperm concentration in TDCIPP-treated rats were unexpectedly higher than those in control rats. TDCIPP did not significantly affect the percentage of motile sperms or sperm swimming pattern. These results contribute to the understanding of the biological effects of TDCIPP.

Tris (1,3-dichloro-2-propyl) phosphate exposure disrupts the gut microbiome and its associated metabolites in mice

BACKGROUND

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) has been frequently detected in environmental media and biological samples. However, knowledge of its adverse health consequences is limited, and its impacts on the human gut microbiota, which play a key role in health and disease, remain unexplored.

OBJECTIVES

To better evaluate the potential risk of TDCIPP exposure in human health, we investigated the effects of TDCIPP on gut microbiome and gut metabolites in C57BL/6 mice.

METHODS

We applied an integrated analytical approach by combing 16S rRNA gene sequencing, metagenomic sequencing and ¹H NMR metabolomics analysis in fecal samples collected from mouse with TDCIPP exposure as well as those from controls.

RESULTS

Both 16S rRNA sequencing and metagenome sequencing showed that TDCIPP exposure significantly changed the gut microbiome, with a remarkable increased Firmicutes at the expense of Bacteroidetes after exposure. Perturbed gut metabolic profiles in the treated group were also observed and closely related with altered gut microbiome. Gene functional annotation analysis further suggested perturbed gut metabolites could be directly caused by altered gut microbiome.

CONCLUSION

TDCIPP exposure has great influence on the gut ecosystem as reflected by perturbation of microbiome community structure, microbial species, gut microbe associated gene expression and gut metabolites, which may contribute to the progression of certain uncharacterized gut microbiota related host diseases. Our findings provide novel insights into adverse effects of TDCIPP exposure on human health.

Novel toxicity of tris(1,3-dichloro-2-propyl) phosphate in adult male rats

The widespread use of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) as a flame retardant has led to its release to the environment. Thus, the toxicological effects of TDCIPP on humans and animals are of importance. For better understanding of its potential toxicities, TDCIPP (250, 500, or 650 mg/kg/day) or vehicle control was administrated orally to adult male Wistar-Imamichi rats for 7 days. After the final administration of compounds, organ weights, histopathology, blood biochemistry, and hematology were examined. Hepatic toxicity was observed at doses ≥ 500 mg/kg/day of TDCIPP, and renal toxicity was observed at 650 mg/kg/day. The anti-androgenic activity of TDCIPP was previously confirmed in vitro and in vivo, but weights of epididymis, an androgen-dependent organ, were not affected by TDCIPP treatment in adults. Serum alkaline phosphatase activity was significantly decreased in all TDCIPP-treated rats independent of dose. Hemoglobin concentration, hematocrit, red blood cell count, and reticulocyte count were decreased in all TDCIPP-treated rats, but mean corpuscular volume, total iron-binding capacity, and serum iron were normal, suggesting that renal anemia was caused by TDCIPP. Together with previous reports on effects of anti-androgenic substances on red blood cell indices, anemia caused by TDCIPP could be due to its anti-androgenic activity. These considerations will contribute to further assessment of the toxicity of the compound.