Prenatal exposure to drinking-water chlorination by-products, cytochrome P450 gene polymorphisms and small-for-gestational-age neonates

Dichloroacetic acid and trichloroacetic acid as disinfection by-products in drinking water are endocrine-disrupting chemicals

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 102-, 103-, 104-, or 5 × 104-fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 103-fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 104-fold MCL of DCAA (264 mg/kg/d) or ≥ 103-fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 103-fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 102-fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 104-fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water.

Chloroacetonitrile reduces rat prenatal bone length and induces oxidative stress, apoptosis, and DNA damage in rat fetal liver

One of the disinfection byproducts of chlorinating drinking water is chloroacetonitrile (CAN). Thirty-six female rats were used and distributed equally into four groups. The low dose treated group received CAN at a dose of 5.5 mg/kg body weight/day (1/40 LD₅₀ ) orally from the 6th to 12th day of gestation. The high dose treated group received 11 mg/kg body weight/day (1/20 LD₅₀ ) of CAN orally for the same period, the vehicle control group received 1 mL of corn oil, and the water control group received 1 mL of distilled water orally for the same period. High dose exposure to CAN significantly reduced gravid uterine weight, fetal body weights, and length, and caused obvious skeletal deformities, weak mineralization. Fetal tibial growth plates displayed histopathologic changes. Induced oxidative stress and redox imbalance in fetal liver tissues was evidenced by significantly decreased in catalase and superoxide dismutase activity, and elevated malondialdehyde levels. Histopathological, glycogen content changes, and DNA damage were observed in the fetal liver of high dose treated group. Additionally, administration of high dose of CAN induced apoptosis, evidenced by increased caspase-3 concentration in fetal liver. Thus, extensive exposure to CAN induces poor pregnancy outcomes. CAN levels in water should be monitored regularly.

Gene-environment interactions related to maternal exposure to environmental and lifestyle-related chemicals during pregnancy and the resulting adverse fetal growth: a review

Background

There are only limited numbers of reviews on the association of maternal-child genetic polymorphisms and environmental and lifestyle-related chemical exposure during pregnancy with adverse fetal growth. Thus, this article aims to review: (1) the effect of associations between the above highlighted factors on adverse fetal growth and (2) recent birth cohort studies regarding environmental health risks.

Methods

Based on a search of the PubMed database through August 2021, 68 epidemiological studies on gene-environment interactions, focusing on the association between environmental and lifestyle-related chemical exposure and adverse fetal growth was identified. Moreover, we also reviewed recent worldwide birth cohort studies regarding environmental health risks.

Results

Thirty studies examined gene-smoking associations with adverse fetal growth. Sixteen maternal genes significantly modified the association between maternal smoking and adverse fetal growth. Two genes significantly related with this association were detected in infants. Moreover, the maternal genes that significantly interacted with maternal smoking during pregnancy were cytochrome P450 1A1 (CYP1A1), X-ray repair cross-complementing protein 3 (XRCC3), interleukin 6 (IL6), interleukin 1 beta (IL1B), human leukocyte antigen (HLA) DQ alpha 1 (HLA-DQA1), HLA DQ beta 1 (HLA-DQB1), and nicotinic acetylcholine receptor. Fetal genes that had significant interactions with maternal smoking during pregnancy were glutathione S-transferase theta 1 (GSTT1) and fat mass and obesity-associated protein (FTO). Thirty-eight studies examined the association between chemical exposures and adverse fetal growth. In 62 of the 68 epidemiological studies (91.2%), a significant association was found with adverse fetal growth. Across the studies, there was a wide variation in the analytical methods used, especially with respect to the genetic polymorphisms of interest, environmental and lifestyle-related chemicals examined, and the study design used to estimate the gene-environment interactions. It was also found that a consistently increasing number of European and worldwide large-scale birth cohort studies on environmental health risks have been conducted since approximately 1996.

Conclusion

There is some evidence to suggest the importance of gene-environment interactions on adverse fetal growth. The current knowledge on gene-environment interactions will help guide future studies on the combined effects of maternal-child genetic polymorphisms and exposure to environmental and lifestyle-related chemicals during pregnancy.

Supplementary information

The online version contains supplementary material available at https://doi.org/10.1265/ehpm.21-00033.

Exposure to disinfection by-products and reproductive hormones among women: Results from the Tongji Reproductive and Environmental (TREE) study

BACKGROUND

Disinfection by-products (DBPs) have been shown to impair female reproductive function. However, epidemiological evidence on reproductive hormones is scarce.

OBJECTIVE

To investigate the associations between DBP exposures and reproductive hormones among women undergoing assisted reproductive technology.

METHODS

We included 725 women from the Tongji Reproductive and Environmental (TREE) Study, an ongoing cohort conducted in Wuhan, China during December 2018 and January 2020. Urine samples collected at recruitment were quantified for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures. At day 2-5 of menstruation, serum reproductive hormones including luteinizing hormone (LH), estradiol (E₂), total testosterone (T), progesterone (PRGE), and prolactin (PRL) were determined. Multivariate linear regression models were performed to assess the associations of urinary DCAA and TCAA concentrations with reproductive hormone levels. Dose-response relationships were investigated using natural cubic spline (NCS) and restricted cubic spline (RCS) models.

RESULTS

After adjusting for relevant confounders, we observed that higher urinary DCAA levels were associated with increased serum PRGE (9.2%; 95% CI: -0.55%, 19.8% for the highest vs. lowest tertile; P for trend = 0.06). Based on NCS models, we observed U-shaped associations of urinary DCAA with serum PRGE and PRL; each ln-unit increment in urinary DCAA concentrations above 3.61 μg/L and 6.30 μg/L was associated with 18.9% (95% CI: 4.8%, 34.7%) and 23.3% (95% CI: -0.92%, 53.5%) increase in serum PRGE and PRL, respectively. The U-shaped associations were further confirmed in RCS models (P for overall association ≤0.01 and P for non-linear associations ≤0.04). We did not observe evidence of associations between urinary TCAA and reproductive hormones.

CONCLUSION

Urinary DCAA but not TCAA was associated with altered serum PRGE and PRL levels among women undergoing assisted reproductive technology.

Meta-analysis of small for gestational age births and disinfection byproduct exposures

BACKGROUND

Some epidemiological studies show associations between disinfection byproducts (DBPs) and adverse developmental outcomes.

OBJECTIVES

We undertook a meta-analysis of epidemiological studies on maternal exposure to trihalomethanes (THMs) and haloacetic acids (HAAs) and risk of small for gestational age (SGA) birth.

METHODS

We identified forty-five publications including two reports and five theses via a 2020 literature search. Nineteen study populations from 16 publications met the inclusion criteria and were systematically evaluated. Effect measures were pooled using random effects meta-analytic methods along with cumulative, sub-group and meta-regression analyses to examine between-study heterogeneity and variation in risk across different DBP measures.

RESULTS

We detected a small increased risk for SGA with exposure to the sum of four (i.e., THM4) THM4 (odds ratio (OR) = 1.07; 95%CI: 1.03, 1.11), chloroform (OR = 1.05; 95%CI: 1.01, 1.08), bromodichloromethane (OR = 1.08; 95%CI: 1.05, 1.11) and the sum of the brominated THM4 (OR = 1.05; 95%CI: 1.02, 1.09). Larger ORs were detected for the sum of five haloacetic acids (i.e., HAA5) (OR = 1.12; 95%CI: 1.01, 1.25), dichloroacetic acid (OR = 1.25; 95%CI: 1.01, 1.41) and trichloroacetic acid (OR = 1.21; 95%CI: 1.07, 1.37). We detected larger SGA risks for several THM4 among the prospective cohort and case-control studies compared to retrospective cohorts and for the SGA3/5% (vs. SGA10%) studies. The THM4 meta-regression showed associations between SGA and the total quality score based on categorical or continuous measures. For example, an OR of 1.03 (95%CI: 1.01, 1.06) was detected for each 10-point increase in the study quality score based on our systematic review.

CONCLUSIONS

We detected a small increased risk of SGA based on 18 THM4 study populations that was comparable to a previous meta-analysis of eight THM4 study populations. We also found increased risks for other THM4 and HAA measures not previously examined; these results were robust after accounting for outliers, publication bias, type of SGA classification, different exposure windows, and other factors.

Risk factors for low birth weight in hospitals of North Wello zone, Ethiopia: A case-control study

BACKGROUND

Low birth weight at birth is an important underlying contributor for neonatal and infant mortality. It accounts for nearly half of all perinatal deaths. Identifying predictors of low birth weight is the first essential step in designing appropriate management strategies. Hence, this study aimed to identify risk factors for low birth weight in hospitals of northeastern Ethiopia.

METHODS

An institution based case-control study design was conducted from 10th April to 15th December 2016. Three hundred sixty mother-infant pairs (120 low birth weight babies as cases and 240 normal birth weights as controls) were included in the study. Data were collected by face-to-face interview. Univariable and multivariable logistic regression models were computed to examine the effect of independent variables on outcome variable using SPSS 20.0. Variables with p-value <0.05 were considered statistically significant.

RESULTS

The mean (±SD) gestational age and birth weight (±SD) were 39.2 (±1.38) weeks and 2800 (±612), grams respectively. Partner's education/being illiterate (AOR: 4.09; 95% CI 1.45, 11.50), antenatal care visit at private health institutions (AOR: 0.13; 95% CI 0.02, 0.66), having history of obstetric complications (AOR: 5.70; 95% CI 2.38, 13.63), maternal weight during pregnancy (AOR: 4.04; 95% CI 1.50, 10.84) and gravidity (AOR: 0.36; 95% CI 0.18, 0.73) were significantly associated with low birth weight. Additionally, a site for water storage and water treatment were significant environmental factors.

CONCLUSION

Maternal weight during pregnancy, paternal education, previous obstetric complication and place of antenatal follow-up were associated with low birth weight. The risk factors identified in this study are preventable. Thus, nutritional counseling, health education on improvement of lifestyle and early recognition and treatment of complications are the recommended interventions.