Household renovation before and during pregnancy in relation to preterm birth and low birthweight in China

First Trimester of Pregnancy as the Sensitive Period for the Association between Prenatal Mosquito Coil Smoke Exposure and Preterm Birth

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother-child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05-1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09-1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03-1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01-1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.

Critical window for the association between prenatal environmental tobacco smoke exposure and preterm birth

Although environmental tobacco smoke (ETS) exposure is considered to be a severe public health problem and a modifiable risk factor for preterm birth (PTB), we still lack a comprehensive understanding of the PTB risk associated with trimester-specific prenatal ETS exposure. This study aimed to examine the accumulation of risk across trimester ETS exposure and the critical window of the association between maternal ETS exposure during pregnancy and PTB. A total of 63,038 mother-child pairs were involved in the analysis of the 2017 survey of Longhua Child Cohort Study. Information about socio-demographic characteristics, prenatal ETS exposure, and birth outcomes were collected using a self-report questionnaire. A series of logistic regression models were employed to assess the associations between prenatal ETS exposure and PTB. We found that maternal ETS exposure during pregnancy significantly increased the risk of PTB and this association increased with both the average level of daily ETS exposure and the number of trimesters of ETS exposure. Moreover, mothers who were initially exposed to ETS in the 1st trimester of pregnancy had significant higher risk of PTB (OR = 1.34, 95% CI: 1.25-1.44). Furthermore, mothers exposed to ETS in the 1st trimester only (OR = 1.26, 95%CI: 1.04-1.50), in both 1st and 2nd trimester (OR = 1.35, 95%CI: 1.08-1.67) and throughout pregnancy (OR = 1.35, 95%CI: 1.24-1.46) experienced a significantly high risk of PTB. Prenatal maternal ETS exposure during only the 2nd trimester also resulted in a high risk of PTB with marginal significance (OR = 1.33, 95% CI:0.78-2.13). To conclude, the 1st and early 2nd trimester might be the critical window for prenatal ETS exposure causing PTB.

Effects of household environmental exposure and ventilation in association with adverse birth outcomes: A prospective cohort study in rural China

Prenatal exposure to outdoor air pollution have been associated with birth outcomes. However, there is limited evidence on the adverse effects of household indoor air pollution worldwide, much less in rural areas of China. This study aimed to explore the associations of household environmental factors (primary cooking fuel, housing renovation, and home ventilation) with four adverse birth outcomes (preterm birth (PTB), small for gestational age (SGA), low birth weight (LBW), and term low birth weight (T-LBW)). We conducted a cohort study involving 10,324 pregnancies in women who delivered a live-born infant from 2015 to 2018 in Guangxi, China. Risk ratios and 95% confidence intervals (CI) were estimated with control for reproductive history, lifestyle, home environmental confounders, and other potential confounders. A total of 5.4% of the infants were PTB, 10.7% were SGA, 5.5% had LBW, and 3.0% had T-LBW. Household-use induction cookers as the primary cooking fuel during pregnancy was associated with SGA (RR = 1.31, 95% CI: 1.07-1.60), LBW (1.41, 1.09-1.82), and T-LBW(1.62, 1.16-2.26), as compared with household-use gas as the primary cooking fuel. Housing renovation within one year before pregnancy was associated with PTB (1.45, 1.06-1.98) and LBW (1.56, 1.17-2.09), while housing renovation during pregnancy was associated with a higher risk of SGA only in moderate home ventilation conditions (3.74, 1.69-8.28). Our findings suggested that household-use induction cookers as the primary cooking fuel increased the risks of SGA, LBW, and T-LBW. In addition, housing renovation within one year before pregnancy increased the risks of PTB and LBW. Proper home ventilation may reduce the effect on the association between housing renovation during pregnancy and SGA.

Maternal exposure to ambient PM2.5 and term birth weight: A systematic review and meta-analysis of effect estimates

Effect estimates of prenatal exposure to ambient PM_2.5 on change in grams (β) of birth weight among term births (≥37 weeks of gestation; term birth weight, TBW) vary widely across studies. We present the first systematic review and meta-analysis of evidence regarding these associations. Sixty-two studies met the eligibility criteria for this review, and 31 studies were included in the meta-analysis. Random-effects meta-analysis was used to assess the quantitative relationships. Subgroup analyses were performed to gain insight into heterogeneity derived from exposure assessment methods (grouped by land use regression [LUR]-models, aerosol optical depth [AOD]-based models, interpolation/dispersion/Bayesian models, and data from monitoring stations), study regions, and concentrations of PM_2.5 exposure. The overall pooled estimate involving 23,925,941 newborns showed that TBW was negatively associated with PM_2.5 exposure (per 10 μg/m³ increment) during the entire pregnancy (β = -16.54 g), but with high heterogeneity (I² = 95.6%). The effect estimate in the LUR-models subgroup (β = -16.77 g) was the closest to the overall estimate and with less heterogeneity (I² = 18.3%) than in the other subgroups of AOD-based models (β = -41.58 g; I² = 95.6%), interpolation/dispersion models (β = -10.78 g; I² = 86.6%), and data from monitoring stations (β = -11.53 g; I² = 97.3%). Even PM_2.5 exposure levels of lower than 10 μg/m³ (the WHO air quality guideline value) had adverse effects on TBW. The LUR-models subgroup was the only subgroup that obtained similar significant of negative associations during the three trimesters as the overall trimester-specific analyses. In conclusion, TBW was negatively associated with maternal PM_2.5 exposures during the entire pregnancy and each trimester. More studies based on relatively standardized exposure assessment methods need to be conducted to further understand the precise susceptible exposure time windows and potential mechanisms.

Gestational exposures to outdoor air pollutants in relation to low birth weight: A retrospective observational study

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO₂ were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO₂ in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02-3.58 for increment of interquartile range (18.5 μg/m³); p-value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO₂ during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO₂ exposures could be greater during early periods than during later periods of gestation.

Assessing Human Exposure to SVOCs in Materials, Products, and Articles: A Modular Mechanistic Framework

A critical review of the current state of knowledge of chemical emissions from indoor sources, partitioning among indoor compartments, and the ensuing indoor exposure leads to a proposal for a modular mechanistic framework for predicting human exposure to semivolatile organic compounds (SVOCs). Mechanistically consistent source emission categories include solid, soft, frequent contact, applied, sprayed, and high temperature sources. Environmental compartments are the gas phase, airborne particles, settled dust, indoor surfaces, and clothing. Identified research needs are the development of dynamic emission models for several of the source emission categories and of estimation strategies for critical model parameters. The modular structure of the framework facilitates subsequent inclusion of new knowledge, other chemical classes of indoor pollutants, and additional mechanistic processes relevant to human exposure indoors. The framework may serve as the foundation for developing an open-source community model to better support collaborative research and improve access for application by stakeholders. Combining exposure estimates derived using this framework with toxicity data for different end points and toxicokinetic mechanisms will accelerate chemical risk prioritization, advance effective chemical management decisions, and protect public health.