Introduction
While prenatal exposure to air pollution has been shown to reduce birth weight, epidemiological studies where source-specific exposure data is available are still very few. The aim of the present study was to investigate the associations between source-specific exposure to ambient fine particulate matter (PM2.5) from different local sources during pregnancy and birth weight of the child.

Materials and methods
We defined an administrative cohort using data on 40,245 singleton births in southern Sweden. Exposure to ambient PM2.5 at the residential address during pregnancy was modelled with 100 x 100 m spatial resolution. Concentrations of PM2.5 from all local sources (all-source PM2.5), tailpipe exhaust, vehicle wear-and-tear, and small-scale residential heating were investigated separately. The relationship between birth weight (continuous) and low birth weight (<2,500 grams) were analysed using linear and logistic regression, respectively, in crude and adjusted models.

Results
There were associations between each local source of PM2.5 and birth weight as a continuous variable in the adjusted models. Birth weight decreased by an average of 34 grams (95% confidence interval, CI: 26–43) in association with a 1 µg/m3 increase in all-source PM2.5 in the adjusted models. Tailpipe exhaust seemed to have the greatest effect per 1 µg/m3 increase, with a mean reduction of 278 grams (95% CI: 207–349), followed by vehicle wear-and-tear: mean decrease of 106 grams (95% CI: 81–132). For small-scale residential heating, the corresponding decline was 36 grams on average (95% CI: 14–57). The only local source of PM2.5 associated with low birth weight (<2500 g) was small-scale residential heating, with an adjusted odds ratio (OR) of 1.50 (95% CI: 1.12–2.03).

Conclusion
Locally produced prenatal exposure to all-source PM2.5, tailpipe exhaust, vehicle wear-and-tear, as well as small-scale residential heating may all reduce newborns’ birth weight.

Background and Aim. Air pollution exposure is associated with impaired neurodevelopment, altered structural brain morphology in children and neurodegenerative disorders. Differential susceptibility to air pollution may be influenced by genetic features. We aimed to evaluate whether the apolipoprotein E (APOE) genotype or the polygenic risk score (PRS) for Alzheimer’s Disease (AD), modify the association between air pollution exposure during pregnancy and childhood and structural brain morphology in preadolescents.

Methods. We included 1186 children from the Generation R Study. Concentrations of 14 air pollutants were calculated at the participants’ home address during pregnancy and childhood using land-use-regression models. Structural brain images were collected at age 9–12 years to assess (sub)cortical brain volumes. APOE status and PRS for AD were examined as effect modifiers. We conducted single-pollutant analyses with a two-way interaction between air pollution and APOE status or PRS for AD and multi-pollutant analyses with the two-way interaction.

Results. Higher pregnancy PMcoarse and childhood PAHs exposure was differentially associated with larger cerebral white matter volume in APOE ε4 carriers compared to non-carriers (29485 mm3 [95% CI 6189, 52781] and 18663 mm3 [469, 36856], respectively). Higher pregnancy PMcoarse exposure was differentially associated with larger cortical grey matter volume in children with higher compared to lower PRS for AD (19436 mm3 [825, 38046]).

Conclusions. APOE status and PRS for AD have a possible modifying effect on the association between air pollution exposure and brain structural morphology in preadolescents. Both seem to modify the association towards the typical development of the brain, with increasing cortical volumes, highlighting the possibility of the antagonistic pleiotropic effect (i.e., protective effect in early life but altered neurodegenerative processes in adulthood). Future studies should research this antagonistic pleiotropic effect and study trajectorial brain development using a longitudinal design.

Keywords. environmental pollution, neurodevelopment, neuroimaging, genetic modifiers

Background and Aim: Over 11 million Americans reside within 150 m of a major highway, an area of high air pollution exposure. Traffic congestion further contributes to this problem but has not been evaluated in epidemiological studies to-date. We hypothesize that degraded air quality due to traffic congestion will have an adverse impact on infant birth weight.

Methods: Using a population-based birth cohort in 2015-2016 for the State of Texas, we limited our study population to addresses within 1,000 m of a road in this database. We calculated traffic congestion around each geocoded maternal address at delivery for 100 m, 300 m, and 500 m buffer distances. We leveraged novel congestion and vehicle volume measurement data from the Texas Most Congested Roads database, which contains measurements of traffic volume, delay, and emissions from connected vehicle and device data. We used linear regressions to evaluate the association between traffic congestion and term birth weight, adjusting for sociodemographic characteristics and vehicle volume.

Results: Among 580,992 births, we find consistent negative associations between traffic congestion and term birth weight. We observed a 15.8 g reduction in term birth weight (95% CI: -20.5, -11.1) among the highest quintile of delay exposure at 500 m compared to births with no delay exposure in this buffer distance. Results are similar, though attenuated, for truck-specific congestion. When we calculate excess vehicle emissions from congestion, we observe a -17.6 g reduction in term birth weight (95% CI: -21.4, -13.9) when comparing the highest and lowest quintiles.

Conclusion: Our study provides important new evidence that traffic congestion is associated with adverse infant health outcomes, in addition to total traffic volumes on nearby roads. Therefore, programs to reduce traffic congestion may have positive co-benefits for infant health with respect to birth weight.

Keywords: traffic-related air pollution, infant health, birth weight

Background/Aim. Personal exposure to fine particulate matter (PM₂.₅) from household air pollution is well-documented in Sub-Saharan Africa, but spatial patterns of exposure are poorly characterized. Our study aimed to evaluate personal exposure to PM₂.₅ when within the household and community, and during typical hours of cooking, among mothers and children in rural communities near Kintampo, Ghana. We also explored other geographic determinants of exposure.
Methods. Our study included 259 sessions of geolocated, gravimetrically-calibrated one-minute PM₂.₅ measurements from participants in the GRAPHS Child Lung Function Study. Household boundaries were defined using a 50-meter buffer around participants’ homes. Community boundaries were developed by applying a spatial clustering algorithm to an open-source dataset of building footprints in Africa. For each GPS location, we estimated building density (500m buffer) and proximity to roadways (100m buffer). We estimated the percentage change in logarithm PM₂.₅ by location (household, community), time of day (morning/evening cooking hours versus nighttime), building density and proximity to roadways using linear mixed effect models.
Results. Relative to nighttime household exposures, PM₂.₅ exposure during evening cooking hours increased by 175% (95CI=162-188%) and 75% (95CI=50-105%) in the household and community, respectively. Exposures were elevated in areas with the highest versus lowest quartile of building density (Q1vsQ4=28%, 95CI=14-45%). The effect of building density was strongest when modeled jointly with evening cooking hours, and influenced levels in both the household and community (64% and 82% increase from Q1 to Q4, respectively). Being proximal to a tertiary or trunk roadway increased PM₂.₅ exposure by 44% (95CI=24-67%) and 13% (95CI=4-22%), respectively.
Conclusions. Our findings suggest that neighbors’ cooking and other community PM₂.₅ sources contribute substantially to personal PM₂.₅ exposure. Building density may exacerbate community exposures when multiple households are cooking simultaneously. Proximity to tertiary or trunk roadways increase personal PM₂.₅ exposure.
Keywords. Air pollution; exposure assessment; spatial statistics

Background and aim
Household air pollution (HAP) from cooking with solid fuels used during pregnancy has been associated with adverse pregnancy outcomes. The HAPIN trial is a randomized controlled trial of liquefied petroleum gas (LPG) stoves and fuel distribution in 3200 households conducted across Guatemala, India, Peru, and Rwanda. We describe the effects of the LPG intervention on fetal/infant stillbirth, neonatal mortality and congenital anomalies.

Methods
Pregnant women (18-35 years of age; gestation confirmed by ultrasound at 9-20 weeks) were randomly assigned to an intervention arm (n=1593) or control arm (n=1607). Participants were monitored for stillbirth (fetal death ≥ 20 weeks gestation), neonatal mortality (death of any live-born infant in first 28 completed days of life), and congenital anomalies (any structural/functional anomalies that occur during intrauterine life). Analyses were performed according to intention-to-treat (ITT) analysis, and binary outcomes were compared between the two arms using log binomial models.

Results
Pregnant women were enrolled in the study and received their LPG stoves at 15.4 (SD 3.1) weeks gestation. We recorded 47 congenital anomalies (23 intervention, 24 control), 56 stillbirths (28 intervention, 28 control), and 41 neonatal deaths (20 intervention, 21 control) between enrollment and 28 days of live of the infant. Compared to the control arm, the relative risk among women randomized to the intervention was 0.96 (95% CI: 0.55, 1.70) for congenital anomaly, 1.01 (95% CI: 0.60, 1.70) for stillbirth and 0.97 (95% CI: 0.53, 1.77) for neonatal mortality.

Conclusions
We did not find a significant reduction in incidence of stillbirth, neonatal mortality and congenital anomalies. The small number of cases may have contributed to the lack of power and the intervention was introduced after the first trimester, which may be too late to find a protective effect.

Keywords: household air pollution; congenital anomalies, stillbirth, neonatal mortality.
intention-to-treat, HAPIN trial

Background and Aim
Ramadan fasting during pregnancy linked with low dietary intake could adversely affect fetal growth. However, previous studies report mixed findings on the effect of fasting on infant birth weight. Therefore, this study of term newborns aims to estimate the association between Ramadan fasting during pregnancy and birth weight and evaluate the effect modification by maternal biomass fuel exposure.
Methods
Our study included 1,514 mother-child pairs recruited from Kaduna in northwestern Nigeria. The outcome variable was birth weight. The exposure was Ramadan fasting based on the overlap between Ramadan and index pregnancy, cooking fuel type, categorized as biomass fuel or liquefied petroleum gas and kerosene (reference). We estimated the covariate-adjusted association between Ramadan fasting and birth weight. In addition, we performed stratified analysis and estimated interaction to compare the association between biomass fuel and birth weight for various trimesters of Ramadan fasting exposure.
Results
639 (42%) mothers were exposed to Ramadan fasting during pregnancy; first (338, 53%), second (187, 29%), and third trimester (114, 18%). Adjusting for maternal age, education, parity, BMI at birth, and child sex, mothers exposed to Ramadan fasting delivered infants weighing an average of 31g lighter (95%CI −80 to 18) than the unexposed. The association between biomass fuel and birth weight was not significantly different for women exposed and unexposed to fasting (Pinteraction=0.77). But we observed a disparity by trimester of fasting exposure in the association of biomass fuel with birth weight; first (-146g 95%CI -294 to 1), second (-58g 95%CI -240 to 125), and third trimester (-57g 95%CI -396 to 282).
Conclusions
Ramadan fasting during pregnancy is not associated with birth weight. Furthermore, maternal biomass fuel use is significantly related to reduced birth weight only among mothers exposed to Ramadan fasting during the first trimester.
Keywords: Ramadan fasting; biomass fuel; birth weight; Nigeria