Household Air Pollution, Levels of Micronutrients and Heavy Metals in Cord and Maternal Blood, and Pregnancy Outcomes

Air Pollution and Racial Disparities in Pregnancy Outcomes in the United States: A Systematic Review

BACKGROUND

Exposure to air pollutants and other environmental factors increases the risk of adverse pregnancy outcomes. There is growing evidence that adverse outcomes related to air pollution disproportionately affect racial and ethnic minorities. The objective of this paper is to explore the importance of race as a risk factor for air pollution-related poor pregnancy outcomes.

METHODS

Studies investigating the effects of exposure to air pollution on pregnancy outcomes by race were reviewed. A manual search was conducted to identify missing studies. Studies that did not compare pregnancy outcomes among two or more racial groups were excluded. Pregnancy outcomes included preterm births, small for gestational age, low birth weight, and stillbirths.

RESULTS

A total of 124 articles explored race and air pollution as risk factors for poor pregnancy outcome. Thirteen percent of these (n=16) specifically compared pregnancy outcomes among two or more racial groups. Findings across all reviewed articles showed more adverse pregnancy outcomes (preterm birth, small for gestational age, low birth weight, and stillbirths) related to exposure to air pollution among Blacks and Hispanics than among non-Hispanic Whites.

CONCLUSION

Evidence support our general understanding of the impact of air pollution on birth outcomes and, specifically, of disparities in exposure to air pollution and birth outcomes for infants born to Black and Hispanic mothers. The factors driving these disparities are multifactorial, mostly social, and economic factors. Reducing or eliminating these disparities require interventions at individual, community, state, and national level.

Understanding trimester-specific miscarriage risk in Indian women: insights from the calendar data of National Family Health Survey (NFHS-5) 2019-21

BACKGROUND

The primary public health issue, especially in low- and middle-income countries, is early pregnancy loss driven by miscarriage. Understanding early pregnancy losses and the characteristics of mothers who have miscarriages is essential to creating effective reproductive health strategies. Thus, this study's primary goal is to delve into the factors which impact miscarriages that take place prior to and following the first 12 weeks of gestation.

METHODS

The bivariate analysis was employed to determine the frequency of miscarriages. The factors associated with miscarriages in the first (≤12 weeks) and second & above (> 12 weeks) trimesters of pregnancy were then examined using a generalised linear regression model, with 95% confidence intervals. Finally, we use ArcGIS to illustrate the prevalence of miscarriage in the districts of India.

RESULTS

Our result shows that miscarriages occur often in India (4.9%), with 23% of cases occurring in the first trimester (≤12 weeks). In our bivariate analysis, we identified several factors associated with a higher prevalence of miscarriages in India. It was found that mothers aged thirty years or older, residing in urban areas, with less than ten years of education, belonging to the richest wealth quantile, expressing a desire for more children, having no demand for contraception, and possessing no parity experienced a higher prevalence of miscarriage in total pregnancies in India. On the other hand, the generalised linear model's findings show that mothers who are thirty years of age or older, practise other religions, live in urban areas, are members of other castes, want more children, marry before the age of eighteen, and meet their contraceptive needs are more likely to have miscarriages in total pregnancy. However, there is a larger likelihood of miscarriage in the first trimester (≤12 weeks) for mothers who follow other religions, live in urban areas, are from Other Backward Class (OBC), get married before the age of eighteen, and fall into the middle and upper wealth quantiles. A mother is more likely to miscarriage in the second & above (> 12 weeks) trimesters if she is older than thirty, from other castes, wants more children, has moderate media exposure, marries before turning eighteen, meets her contraceptive needs, and does not feel the need for contraception. After accounting for socioeconomic characteristics, all results were statistically significant.

CONCLUSIONS

Given the substantial number of miscarriages in India, police need to improve planning and guidance in order to lower pregnancy loss due to miscarriage. Miscarriage rates may be significantly decreased by enhancing the availability and quality of reproductive health care infrastructure, particularly in rural areas.

Combined exposure to PM2.5 and PM10 in reductions of physiological development among preterm birth: a retrospective study from 2014 to 2017 in China

Background

Preterm birth (PTB) has been linked with ambient particulate matter (PM) exposure. However, data are limited between physiological development of PTB and PM exposure.

Methods

Trimester and season-specific PM exposure including PM2.5 and PM10 was collected from Jiaxing between January 2014 and December 2017. Information about parents and 3,054 PTB (gestational age < 37 weeks) outcomes such as weight (g), head circumference (cm), chest circumference (cm), height (cm) and Apgar 5 score were obtained from birth records. We used generalized linear models to assess the relationship between PTB physiological developmental indices and PM2.5, PM10 and their combined exposures. A binary logistic regression model was performed to assess the association between exposures and low birth weight (LBW, < 2,500 g).

Results

Results showed that there were 75.5% of low birth weight (LBW) infants in PTB. Decreased PM2.5 and PM10 levels were found in Jiaxing from 2014 to 2017, with a higher PM10 level than PM2.5 each year. During the entire pregnancy, the highest median concentration of PM2.5 and PM10 was in winter (61.65 ± 0.24 vs. 91.65 ± 0.29 μg/m3) followed by autumn, spring and summer, with statistical differences in trimester-specific stages. After adjusting for several potential factors, we found a 10 μg/m3 increase in joint exposure of PM2.5 and PM10 during the entire pregnancy associated with reduced 0.02 week (95%CI: -0.05, -0.01) in gestational age, 7.9 g (95%CI: -13.71, -2.28) in birth weight, 0.8 cm in height (95%CI: -0.16, -0.02), 0.05 cm (95%CI: -0.08, - 0.01) in head circumference, and 0.3 (95%CI: -0.04, -0.02) in Apgar 5 score, except for the chest circumference. Trimester-specific exposure of PM2.5 and PM10 sometimes showed an opposite effect on Additionally, PM2.5 (OR = 1.37, 95%CI: 1.11, 1.68) was correlated with LBW.

Conclusion

Findings in this study suggest a combined impact of fine particulate matter exposure on neonatal development, which adds to the current understanding of PTB risk and health.

Effect of PM concentration on anemia blood indicators reduced by air purifiers

Housewives perform daily household chores, which directly expose them to indoor particulate matter (PM). Indoor PM exposure is a potential factor that increases systemic inflammation and affects hematopoietic action. This study investigated the decrease in indoor PM concentration by air purifiers on indicators of anemia, such as hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). We analyzed the data of 40 housewives who were subjected to an air purifier intervention in Seoul and Ulsan, Republic of Korea. Indoor exposure levels of PM2.5 and PM10 were analyzed with sensor adjusted and gravimetric measurement. We also investigated the same anemia indicators before and after the installation of an air purifier for three months (short-term: one month, long-term: three months). Statistical analysis was performed by a multiple linear model and a linear mixed model. The indoor PM exposure levels and air purifier use were related to anemia indicators (hemoglobin and MCHC). The increase in indoor PM2.5 level was associated with a decrease in MCHC (β: 0.034, P = 0.031) and hemoglobin (β: 0.013, P = 0.04). The decrease in indoor PM2.5 concentration by air purifier was associated with an increase in MCHC (β: 0.204, P = 0.087) and hemoglobin (β: 0.190, P = 0.039). In particular, after air purifier intervention, the amounts of MCHC and hemoglobin significantly increased. Our results suggest that indoor air purifier use could decrease indoor PM level and the risk of anemia to housewives. Because the effect on anemia is subacute, it was confirmed three months after air purifier operation. In conclusion, anemia indicators can be improved by PM reduction management.

Association between cooking fuel and folate insufficiency among pregnant women in Northern China

This study explored whether using a coal or biomass stove for cooking was associated with a greater risk of red blood cell (RBC) folate insufficiency among pregnant women compared to using clean energy. A researcher-designed questionnaire was used to collect information on exposure-related factors and confounding factors. RBC folate concentrations were examined by microbiological assay. Binary logistic regression analysis was used to identify factors related to RBC folate insufficiency. The use of coal or firewood for cooking was associated with an increased risk of RBC folate insufficiency (<906 nmol/L) compared to gas. In subgroup analyses, associations between the use of polluting cooking fuels and folate insufficiency were positive for both urban and rural residents and statistically significant for rural women. Efforts to promote the use of clean energy and proper ventilation, especially in rural areas, are recommended to improve the health of pregnant women and their offspring.

Cellular mechanisms linking to outdoor and indoor air pollution damage during pregnancy

Pregnancies are a critical window period for environmental influences over the mother and the offspring. There is a growing body of evidence associating indoor and outdoor air pollution exposure to adverse pregnancy outcomes such as preterm birth and hypertensive disorders of pregnancy. Particulate matter (PM) could trigger oxi-inflammation and could also reach the placenta leading to placental damage with fetal consequences. The combination of strategies such as risk assessment, advise about risks of environmental exposures to pregnant women, together with nutritional strategies and digital solutions to monitor air quality can be effective in mitigating the effects of air pollution during pregnancy.

Birth Size Outcomes in Relation to Maternal Blood Levels of Some Essential and Toxic Elements

Exposures to toxic trace elements and deficiencies of essential trace elements during pregnancy may impact fetal growth. This study was conducted to determine the association between maternal blood levels of essential elements including manganese (Mn), copper (Cu), and zinc (Zn) and toxic elements including arsenic (As), cadmium (Cd), and lead (Pb) at the first trimester with neonatal anthropometric parameters. This cross-sectional study was conducted in 2019-2020 in Isfahan, Iran. Overall, 263 mother-infant pairs were recruited in the first trimester of pregnancy. Maternal whole blood was collected, and essential and toxic elements were determined by mass spectrometry (ICP-MS)-based method. Birth size measurements were performed according to standardized protocols. Geometric means and standard deviations of maternal blood concentrations of Mn, Cu, Zn, As, Cd, and Pb were 3.94 ± 0.82, 5.22 ± 0.57, 7.67 ± 0.58, 2.21 ± 0.77, - 0.59 ± 0.98, and 3.23 ± 0.72 µg/l, respectively. Mean age of mothers was 29.94 ± 5.22 years. Thirty-one (12.1%) neonates were preterm. Maternal blood Pb levels were negatively correlated with birth weight (β = - 0.22 (CI 95%: - 0.38, - 0.05) p = 0.010) and marginally with birth head circumference (β = - 0.14(CI 95%: - 0.29, 0.02), P = 0.094) after adjustment for potential confounder variables. There was no significant association between Mn, Cu, Zn, As, Cd, and birth size measurements. Reverse association was found between maternal blood Pb levels and birth weight and birth head circumference. There is limited evidence related to the association between essential and toxic elements during pregnancy with birth size measurements and pregnancy disorders. More studies are suggested to assess of the effect of the trace elements and birth outcomes.

A secondary data analysis of a cluster randomized controlled trial: improved cookstoves associated with reduction in incidence of low birthweight in rural Malawi

BACKGROUND

In northern rural Malawi, the majority of households cook using open fires and there is also a high burden of adverse birth outcomes. The use of open fires or highly polluting cookstoves is associated with low birthweight in babies. There is mixed evidence on whether implementation of cleaner burning cookstoves reduces the number of babies born with low birthweight.

METHODS

This is a secondary analysis of a cluster randomized control trial in Malawi, conducted over 2014-17. Households were randomized to receive improved cookstoves or to continue current practices. For this analysis, the primary outcome was low birthweight in households under routine demographic surveillance, among births occurring within the trial time frame (N = 4010). A subset of data with stricter exposure definitions respecting the original randomized allocation was also analysed (N = 1050). A causal, forwards modelling approach was used.

RESULTS

The main dataset showed evidence of effect of the intervention on low birthweight [adjusted odds ratio (aOR) 0.69; 95% CI 0.48-0.99, n = 2788). The subset analysis lacked power to provide evidence of association between improved cookstoves and low birthweight in the stricter exposure definition (aOR 0.62; 95% CI 0.35-1.09, n = 932).

CONCLUSIONS

This study provides some evidence that an improved cookstove intervention in rural Malawi reduced the number of babies born with low birthweight by 30%. This direction of the effect was also seen in the subset analysis. The analysis suggests that the intervention reduced the number of infants born prematurely or with intra-uterine growth restriction, indicating that improved cookstoves could be a useful maternal health intervention.

Association between Wood and Other Biomass Fuels and Risk of Low Birthweight in Uganda: A Cross-Sectional Analysis of 2016 Uganda Demographic and Health Survey Data

In utero exposure to household air pollution (HAP) from polluting cooking fuels has been linked to adverse pregnancy outcomes including low birthweight (LBW). No previous study in Uganda has attempted to investigate the association between the different types of biomass cooking fuels and LBW. This study was conducted to investigate the association between wood and other biomass cooking fuel use with increased risk of LBW, using the 2016 Uganda Demographic and Health Survey for 15,270 live births within five years prior to interview. LBW, defined as birthweight of <2500 g, was estimated from maternal recall and health cards. Association between household exposure to the different solid biomass cooking fuels and LBW was determined using multivariable logistic regression. Biomass cooking fuels were used in 99.6% of the households, with few (0.3%) using cleaner fuels and 0.1% with no cooking, while the prevalence of LBW was 9.6% of all live-births. Although the crude analysis suggested an association between wood fuel use and LBW compared to other biomass and kerosene fuel use (AOR: 0.82; 95% CI: 0.67−1.00), after adjusting for socio-demographic and obstetric factors, no association was observed (AOR: 0.94; 95% CI: 0.72−1.22). LBW was significantly more likely among female neonates (AOR: 1.32 (95% CI: 1.13−1.55) and neonates born to mothers living in larger households (AOR: 1.03; 95% CI: 1.00−1.07). LBW was significantly less likely among neonates delivered at term (AOR: 0.39; 95% CI: 0.31−0.49), born to women with secondary or tertiary level of education (AOR: 0.80; 95% CI: 0.64−1.00), living in households with a higher wealth index (AOR: 0.69; 95% CI: 0.50−0.96), Eastern (AOR: 0.76; 95% CI:0.59−0.98) and Northern (AOR: 0.75; 95% CI: 0.57−0.99) regions. The study findings suggest inconclusive evidence regarding the association between the use of wood compared to other biomass and kerosene cooking fuels and risk of LBW. Given the close observed association between socioeconomic status and LBW, the Ugandan government should prioritize public health actions which support female education and broader sustainable development to improve household living standards in this setting.

Direct and Indirect Effects of Indoor Particulate Matter on Blood Indicators Related to Anemia

Exposure to indoor particulate matter (PM) is a potential risk factor that increases systemic inflammation and affects erythropoiesis. This study investigated the association between exposure to indoor PM and blood indicators related to anemia (BIRA) in housewives. Indoor PM and blood folate status are important factors in the risk of anemia. This was a housewife cohort study; we recruited 284 housewives in Seoul and Ulsan, Republic of Korea. Indoor exposure to PM2.5 and PM10 was measured by gravimetric analysis and sensors. We investigated the BIRA, such as hemoglobin (Hb), hematocrit, mean corpuscular volume (MCV), mean corpuscular Hb (MCH), and mean corpuscular Hb concentration (MCHC). Statistical analysis was performed by multiple linear regression model and mediation analysis. The association between BIRA and PM was assessed by multiple linear regression models fitted by mediation analyses. The increase in the level of indoor PM2.5 was associated with a decrease in MCV (Beta coefficient (B): −0.069, Standard error (SE): 0.022) and MCH (B: −0.019, SE: 0.009) in gravimetric measurements. The increase in the level of indoor PM2.5 was associated with a decrease in Hb (B: −0.024, SE: 0.011), hematocrit (B: −0.059, SE: 0.033), and MCV (B: −0.081, SE: 0.037) and MCH (B: −0.037, SE: 0.012) in sensor measurements (PM2.5-Lag10). Further, we identified a serum folate-mediated PM effect. The indoor PM exposure was significantly associated with decreased Hb, MCV, and MCH in housewives. Taken together, our data show that exposure to indoor PM is a risk factor for anemia in housewives. Blood folate concentration can be a mediating factor in the effect of indoor PM on BIRA. Therefore, folate intake should be recommended to prevent anemia in housewives. Moreover, indoor PM exposure should be managed.

Mercury and Prenatal Growth: A Systematic Review

The intrauterine environment is critical for healthy prenatal growth and affects neonatal survival and later health. Mercury is a toxic metal which can freely cross the placenta and disrupt a wide range of cellular processes. Many observational studies have investigated mercury exposure and prenatal growth, but no prior review has synthesised this evidence. Four relevant publication databases (Embase, MEDLINE/PubMed, PsycINFO, and Scopus) were systematically searched to identify studies of prenatal mercury exposure and birth weight, birth length, or head circumference. Study quality was assessed using the NIH Quality Assessment Tool, and results synthesised in a narrative review. Twenty-seven studies met the review criteria, these were in 17 countries and used 8 types of mercury biomarker. Studies of birth weight (total = 27) involving populations with high levels of mercury exposure, non-linear methods, or identified as high quality were more likely to report an association with mercury, but overall results were inconsistent. Most studies reported no strong evidence of association between mercury and birth length (n = 14) or head circumference (n = 14). Overall, our review did not identify strong evidence that mercury exposure leads to impaired prenatal growth, although there was some evidence of a negative association of mercury with birth weight.

Ambient air pollution exposure during the late gestational period is linked with lower placental iodine load in a Belgian birth cohort

BACKGROUND

Adequate intake of iodine is required for the production of thyroid hormones and contributes in pregnant women to a healthy brain development and growth in their offspring. To date, some evidence exists that fine particulate air pollution is linked with the fetal thyroid hormone homeostasis. However, possible effects of air pollutants on the placental iodine storage have not been investigated so far.

OBJECTIVES

We investigated the association between air pollution exposure to particulate matter with a diameter less than 2.5 µm (PM_2.5), NO₂, and black carbon and the placental iodine load.

METHODS

The current study is part of the ENVIRONAGE birth cohort and included 470 mother-newborn pairs. Iodine concentrations were measured in placental tissue. A high-resolution air pollution model was used to estimate the daily exposure to PM_2.5, NO₂, and black carbon over the entire pregnancy based on the maternal residential addresses. Distributed lag nonlinear models (DLNMs) were used to estimate gestational week-specific associations between placental iodine concentrations and the air pollutants to understand the impact of specific exposure windows.

RESULTS

PM_2.5 showed a positive association with placental iodine concentration between the 16^th and 22^nd week of gestation. In contrast, a significant inverse association between PM_2.5 and placental iodine concentration was observed in gestational weeks 29-35. The effect estimate, for a 5 µg/m³ increment in PM_2.5 concentration, was the strongest at week 32 (β -0.11 µg/kg; 95%CI: -0.18 to -0.03). No associations were observed between placental iodine concentrations and NO₂ or black carbon. Assuming causality, we estimated that placental iodine mediated 26% (-0.33 pmol/L; 95%CI: -0.70 to 0.04 pmol/L) of the estimated effect of a 5 µg/m³ increment in PM_2.5 exposure on cord blood free thyroxine (FT₄) concentrations.

CONCLUSION

In utero exposure to particulate matter during the third trimester of pregnancy is linked with a lower placental iodine load. Furthermore, the effect of air pollution on cord blood FT₄ levels was partially mediated by the placental iodine load.

Elevated non-essential metals and the disordered metabolism of essential metals are associated to abnormal pregnancy with spontaneous abortion

Spontaneous abortion is a considerable threat to the physiology and mental health of the mother. The etiology of spontaneous abortion is multifactorial with complicated mechanisms, of which overexposure to non-essential metals (especially heavy metals) has been proposed to be associated with adverse birth outcomes. However, significant knowledge gaps remain to be filled in, such as the deleterious profile of non-essential metals and their interplay with essential metals in abnormal pregnancy. Under this setting, we aimed to address these challenges by conducting a cross-sectional study on 56 patients with spontaneous abortion in the 1^st trimester, by comparing to 55 healthy pregnant women in 1^st the trimester and 41 non-pregnant healthy women. Overexposure to a few non-essential metals, such as arsenic (As), antimony (Sb) and bismuth (Bi), was found in patients with spontaneous abortion, and likewise, some essential elements, such as magnesium (Mg), copper (Cu), vanadium (V), strontium (Sr) and tin (Sn), were also found to be elevated under spontaneous abortion. Further evidence of abnormal pregnancy was induced by a reduced level of internal hormones necessary for normal gestation, such as estradiol (E2) and progesterone (PRGE) in women with spontaneous abortion. Lactate dehydrogenase (LDH) and thyroid-stimulating hormone (TSH) levels were slightly increased in patients with spontaneous abortion. Comprehensive correlation analyses were carried out to identify the crucial factors that result in abortion. Our data stratified the important variables in decreasing order: PRGE, As, Mg, Sb, Sr, Sn, Bi and pregnant times in the progress of spontaneous abortion. Moreover, labyrinthine associations were uncovered between PRGE, non-essential metals and essential elements in causing spontaneous abortion. Therefore, our combined data unveiled the likely synergistic implications of elevated non-essential metals and the disordered metabolism of essential metals in abnormal pregnancy.

Differential association of air pollution exposure with neonatal and postneonatal mortality in England and Wales: A cohort study

BACKGROUND

Many but not all studies suggest an association between air pollution exposure and infant mortality. We sought to investigate whether pollution exposure is differentially associated with all-cause neonatal or postneonatal mortality, or specific causes of infant mortality.

METHODS AND FINDINGS

We separately investigated the associations of exposure to particulate matter with aerodynamic diameter ≤ 10 μm (PM10), nitrogen dioxide (NO2), and sulphur dioxide (SO2) with all-cause infant, neonatal, and postneonatal mortality, and with specific causes of infant deaths in 7,984,366 live births between 2001 and 2012 in England and Wales. Overall, 51.3% of the live births were male, and there were 36,485 infant deaths (25,110 neonatal deaths and 11,375 postneonatal deaths). We adjusted for the following major confounders: deprivation, birthweight, maternal age, sex, and multiple birth. Adjusted odds ratios (95% CI; p-value) for infant deaths were significantly increased for NO2, PM10, and SO2 (1.066 [1.027, 1.107; p = 0.001], 1.044 [1.007, 1.082; p = 0.017], and 1.190 [1.146, 1.235; p < 0.001], respectively) when highest and lowest pollutant quintiles were compared; however, neonatal mortality was significantly associated with SO2 (1.207 [1.154, 1.262; p < 0.001]) but not significantly associated with NO2 and PM10 (1.044 [0.998, 1.092; p = 0.059] and 1.008 [0.966, 1.052; p = 0.702], respectively). Postneonatal mortality was significantly associated with all pollutants: NO2, 1.108 (1.038, 1.182; p < 0.001); PM10, 1.117 (1.050, 1.188; p < 0.001); and SO2, 1.147 (1.076, 1.224; p < 0.001). Whilst all were similarly associated with endocrine causes of infant deaths (NO2, 2.167 [1.539, 3.052; p < 0.001]; PM10, 1.433 [1.066, 1.926; p = 0.017]; and SO2, 1.558 [1.147, 2.116; p = 0.005]), they were differentially associated with other specific causes: NO2 and PM10 were associated with an increase in infant deaths from congenital malformations of the nervous (NO2, 1.525 [1.179, 1.974; p = 0.001]; PM10, 1.457 [1.150, 1.846; p = 0.002]) and gastrointestinal systems (NO2, 1.214 [1.006, 1.466; p = 0.043]; PM10, 1.312 [1.096, 1.571; p = 0.003]), and NO2 was also associated with deaths from malformations of the respiratory system (1.306 [1.019, 1.675; p = 0.035]). In contrast, SO2 was associated with an increase in infant deaths from perinatal causes (1.214 [1.156, 1.275; p < 0.001]) and from malformations of the circulatory system (1.172 [1.011, 1.358; p = 0.035]). A limitation of this study was that we were not able to study associations of air pollution exposure and infant mortality during the different trimesters of pregnancy. In addition, we were not able to control for all confounding factors such as maternal smoking.

CONCLUSIONS

In this study, we found that NO2, PM10, and SO2 were differentially associated with all-cause mortality and with specific causes of infant, neonatal, and postneonatal mortality.