Ambient air pollution and preterm birth: A prospective birth cohort study in Wuhan, China

Low-cost measurement techniques to characterize the influence of home heating fuel on carbon monoxide in Navajo homes

A large fraction of the global population relies on the inefficient combustion of solid fuels for cooking and home heating, resulting in household exposure to combustion byproducts. In the southwestern United States, unhealthy air quality has been observed in some homes that use solid fuels as a primary source of heat on the Navajo Nation. In order to better understand how home heating fuel choice can influence indoor air quality in this region, we used recently developed low-cost electrochemical sensors to measure carbon monoxide (CO) air mole fractions continuously inside and outside 41 homes in two communities on the Navajo Nation. Using low-cost sensors in this study, which don't require extensive training to operate, enabled collaboration with local Diné College students and faculty in the planning and implementation of home deployments. Households used natural gas, propane, pellets, wood, and/or coal for heating. We developed quantification methods that included uncertainty estimation for Alphasense CO-B4 sensors, for measurements both inside and outside homes. CO concentrations elevated above background were observed in homes in each heating fuel group, but the highest hourly concentrations were observed in wood and coal burning homes, some of which exceeded World Health Organization Guidelines on both an hourly and eight-hourly basis. In order to probe the many factors that can influence indoor pollutant concentrations, we developed and implemented methods that employ CO emission and decay time periods observed in homes during everyday activities to estimate air exchange rates as well as CO emission rates on the basis of a given well-mixed volume of air. The air quality measurement tools and methods demonstrated in this study can be readily extended to indoor air quality studies in other communities around the world to inform how home heating and cooking practices are influencing indoor air quality during normal daily activities.

Association of Long-term Exposure to Airborne Particulate Matter of 1 μm or Less With Preterm Birth in China

IMPORTANCE

Airborne particulate matter pollution has been associated with preterm birth (PTB) in some studies. However, most of these studies assessed only populations living near monitoring stations, and the association of airborne particulate matter having a median diameter of 1 μm or less (PM1) with PTB has not been studied.

OBJECTIVE

To evaluate whether PM1 concentrations are associated with the risk of PTB.

DESIGN, SETTING, AND PARTICIPANTS

This national cohort study used National Free Preconception Health Examination Project data collected in 324 of 344 prefecture-level cities from 30 provinces of mainland China. In total, 1 300 342 healthy singleton pregnancies were included from women who were in labor from December 1, 2013, through November 30, 2014. Data analysis was conducted between December 1, 2016, and April 1, 2017.

EXPOSURES

Predicted weekly PM1 concentration data collected using satellite remote sensing, meteorologic, and land use information matched with the home addresses of pregnant women.

MAIN OUTCOMES AND MEASURES

Preterm birth (<37 gestational weeks). Gestational age was assessed using the time since the first day of the last menstrual period. Cox proportional hazards regression analysis was used to examine the associations between trimester-specific PM1 concentrations and PTB after controlling for temperature, seasonality, spatial variation, and individual covariates.

RESULTS

Of the 1 300 342 singleton live births at the gestational age of 20 to 45 weeks included in this study, 104 585 (8.0%) were preterm. In fully adjusted models, a PM1 concentration increase of 10 μg/m3 over the entire pregnancy was significantly associated with increased risk of PTB (hazard ratio [HR], 1.09; 95% CI, 1.09-1.10), very PTB as defined as gestational age from 28 through 31 weeks (HR, 1.20; 95% CI, 1.18-1.23), and extremely PTB as defined as 20 through 27 weeks' gestation (HR, 1.29; 95% CI, 1.25-1.34). Pregnant women who were older (30-50 years) at conception (HR, 1.13; 95% CI, 1.11-1.14), were overweight before pregnancy (HR, 1.13; 95% CI, 1.11-1.15), had a rural household registration (HR, 1.09; 95% CI, 1.09-1.10), worked as farmers (HR, 1.10; 95% CI, 1.09-1.11), and conceived in autumn (HR, 1.48; 95% CI, 1.46-1.50) appeared to be more sensitive to PM1 exposure than their counterparts.

CONCLUSIONS AND RELEVANCE

Results from this national cohort study examining more than 1.3 million births indicated that exposure to PM1 air pollution was associated with an increased risk of PTB in China. These findings will provide evidence to inform future research studies, public health interventions, and environmental policies.

Ambient air pollution the risk of stillbirth: A prospective birth cohort study in Wuhan, China

BACKGROUND

Recent studies suggest that ambient air pollution exposure during pregnancy is associated with stillbirth occurrence. However, the results on the associations between ambient air pollutants and stillbirths are inconsistent and little is known about the gestational timing of sensitive periods for the effects of ambient air pollutants exposure on stillbirth.

OBJECTIVE

This study aimed to examine whether exposure to high levels of ambient air pollutants in a Chinese population is associated with an increased risk of stillbirth, and determine the gestational period when the fetus is most susceptible.

METHODS

We conducted a population-based cohort study in Wuhan, China, involving 95,354 births between June 10, 2011 and June 9, 2013. The exposure assessments were based on the daily mean concentrations of air pollutants obtained from the exposure monitor nearest to the pregnant women's residence. Logistic regression analyses were performed to determine the associations between stillbirths and exposure to each of the air pollutants at different pregnancy periods with adjustment for confounding factors.

RESULTS

Stillbirth increased with a 10 μg/m³ increase in particulate matter 2.5 (PM_2.5) in each stage of pregnancy, and a significant association between carbon monoxide (CO) exposure and stillbirth was found during the third trimester (adjusted odds ratio (aOR): 1.01, 95% confidence interval (CI): 1.00-1.01) and in the entire pregnancy (aOR: 1.18, 95% CI: 1.04-1.34). Furthermore, an increased risk of stillbirth in the third trimester was associated with a 10 μg/m³ increase in PM₁₀ (aOR: 1.08, 95% CI: 1.04-1.11), nitrogen dioxide (NO₂) (aOR: 1.13, 95% CI: 1.07-1.21) and sulfur dioxide (SO₂) (aOR: 1.26, 95% CI: 1.16-1.35). However, no positive association was observed between ozone exposure and stillbirth. In the two-pollutant models, PM_2.5 and CO exposures were found to be consistently associated with stillbirth.

CONCLUSIONS

Our study revealed that exposure to high levels of PM_2.5, PM₁₀, SO₂, NO₂ and CO increases the risk of stillbirth and the most susceptible gestational period to ambient air pollution exposure was in the third trimester. Further toxicological and prospective cohort studies with improved exposure assessments are needed to confirm the causal link between air pollutants and stillbirth.

Exposure to particulate air pollution during early pregnancy is associated with placental DNA methylation

Maternal exposure to particulate matter with aerodynamic diameter <10μm (PM₁₀) during pregnancy results in adverse birth outcomes. Changes in placental DNA methylation might mediate those adverse effects. In this study, we examined the associations between prenatal PM₁₀ exposure and DNA methylation of LINE1, HSD11B2 and NR3C1 in human placenta. One hundred and eighty-one mother newborn pairs (80 fetal growth restriction newborns, 101 normal newborns) participated in this study. The average PM₁₀ exposure of each trimester and of the whole pregnancy was calculated using daily air pollution concentration data. Placental DNA methylation was measured by quantitative polymerase chain reaction-pyrosequencing. Placental LINE-1 DNA methylation was reversely associated with first trimester PM₁₀ exposure 1.78% (-β=1.78, 95% CI: -3.35, -0.22%), while placental HSD11B2 DNA methylation was associated with both first and second trimester PM₁₀ exposure, and relatively increased by 1.03% (95% CI: 0.07, 1.98%) and 2.33% (95% CI: 0.69, 3.76%) for each 10μg/m³ increase in exposure to PM₁₀. Those associations were much more evident in fetal growth restriction newborns than those in normal newborns. In summary, early pregnancy PM₁₀ exposure was associated with placental DNA methylation of LINE1 and HSD11B2, suggesting that such methylation alterations might mediate PM-induced reproductive and developmental toxicity.

Estimation of disease burdens on preterm births and low birth weights attributable to maternal fine particulate matter exposure in Shanghai, China

BACKGROUND

Studies have shown that maternal exposure to particulate matter ≤2.5μm in aerodynamic diameter (PM_2.5) was associated with adverse birth outcomes such as preterm birth (PTB) and low birth weight (LBW). However, the burdens of PTB and LBW attributable to PM_2.5 were rarely evaluated, especially in developing countries.

OBJECTIVES

To estimate the burdens of PTBs and LBWs attributable to outdoor PM_2.5 in Shanghai, China.

METHODS

We collected annual-average PM_2.5 concentrations, concentration-response relationships between PM_2.5 exposure during pregnancy and PTBs and LBWs, rates of PTB and LBW, number of live births, and population sizes in grids of 10km×10km in Shanghai in 2013. Then, they were combined to estimate the odds ratios (ORs), relative risks (RRs), attributable fractions (AFs), and numbers of PTBs and LBWs associated with PM_2.5 exposure.

RESULTS

The population-weighted annual-average concentration of PM_2.5 in Shanghai was 56.19μg/m³ in 2013. According to the first-class limit of PM_2.5 (15μg/m³) in the Ambient Air Quality Standards of China, the weighted RRs of PTBs or LBWs associated with PM_2.5 in Shanghai were 1.49 [95% confidence interval (CI): 1.16-1.80] and 1.31 (95% CI: 1.04-1.67), respectively. There might be 32.61% (95% CI: 13.93%-44.42%) or 4160 (95% CI: 1778-5667) PTBs and 23.36% (95% CI: 3.86%-40.02%) or 1882 (95% CI: 311-3224) LBWs attributable to PM_2.5 exposure. The estimates varied appreciably among different districts of Shanghai.

CONCLUSIONS

Our analysis suggested that outdoor PM_2.5 air pollution might have led to considerable burdens of PTBs and LBWs in Shanghai, China.

Pollution from Fossil-Fuel Combustion is the Leading Environmental Threat to Global Pediatric Health and Equity: Solutions Exist

Fossil-fuel combustion by-products are the world's most significant threat to children's health and future and are major contributors to global inequality and environmental injustice. The emissions include a myriad of toxic air pollutants and carbon dioxide (CO₂), which is the most important human-produced climate-altering greenhouse gas. Synergies between air pollution and climate change can magnify the harm to children. Impacts include impairment of cognitive and behavioral development, respiratory illness, and other chronic diseases-all of which may be "seeded" in utero and affect health and functioning immediately and over the life course. By impairing children's health, ability to learn, and potential to contribute to society, pollution and climate change cause children to become less resilient and the communities they live in to become less equitable. The developing fetus and young child are disproportionately affected by these exposures because of their immature defense mechanisms and rapid development, especially those in low- and middle-income countries where poverty and lack of resources compound the effects. No country is spared, however: even high-income countries, especially low-income communities and communities of color within them, are experiencing impacts of fossil fuel-related pollution, climate change and resultant widening inequality and environmental injustice. Global pediatric health is at a tipping point, with catastrophic consequences in the absence of bold action. Fortunately, technologies and interventions are at hand to reduce and prevent pollution and climate change, with large economic benefits documented or predicted. All cultures and communities share a concern for the health and well-being of present and future children: this shared value provides a politically powerful lever for action. The purpose of this commentary is to briefly review the data on the health impacts of fossil-fuel pollution, highlighting the neurodevelopmental impacts, and to briefly describe available means to achieve a low-carbon economy, and some examples of interventions that have benefited health and the economy.

Association between exposure to particulate matter during pregnancy and birthweight: a systematic review and a meta-analysis of birth cohort studies

Studies of the associations between maternal exposure to particulate matter (PM) and risk of adverse effects on fetal growth are inconsistent and inconclusive. This question can be well answered by carefully designed birth cohort studies; however, so far the evidence from such studies has not come to the same conclusion. We sought to evaluate the association between maternal exposures to PM and low birthweight (LBW) enrolling 14 studies from 11 centers, and to explore the influence of trimester and exposure assessment methods on between-center heterogeneity in this association. Data were derived from PubMed, Embase, Google Scholar, CNKI, and WanFang database, references from relevant articles, and results from published studies until March 2017. Using a random-effects meta-analysis, we combined the coefficient and odds ratios (OR) of individual studies conducted among 14 birth cohort studies. Random-effect meta-analysis results suggested that a 17% and 6% increase in risk of LBW was relevant to a 10 mg/m3 rise in PM2.5 and PM10 exposure concentrations at the 3rd trimester (pooled odds ratios (OR), 1.17 and 1.06; 95% confidence interval (CI), 0.94-1.46 and 0.97-1.15, respectively), but the null value was included in our 95% CI. Our results showed that exposure to PM2.5 and PM10 during pregnancy has a positive relevance to LBW based on birth cohort studies. However, neither reached formal statistical significance. Negative impacts on outcomes of birth is implied by maternal exposure to PM. Further mechanistic researches are needed to explain the connection between PM pollution and LBW.

Exposure to fine particulate matter during pregnancy and risk of term low birth weight in Jinan, China, 2014-2016

BACKGROUND

Existing studies exploring the association between low birth weight (LBW) and maternal fine particulate matter (aerodynamic diameter<2.5μm, PM_2.5) exposure have presented equivocal results, and one of the possible reasons for this finding might be due to relatively low maternal exposures. In addition, relatively narrow maternal exposure windows to PM_2.5 have not been well established for LBW.

METHODS

We employed a nested matched case-control design among 43,855 term births in a large maternity and child care hospital in Jinan, China. A total of 369 cases were identified, and four controls per case matched by maternal age were randomly selected among those with normal birth weight (n=1,476) from 2014 to 2016. Ambient air monitoring data on continuous measures of PM_2.5, nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) (24-h average concentrations) from 2013 to 2016 were collected from thirteen local monitoring stations. An inverse distance weighting method based on both home and work addresses was adopted to estimate the individual daily exposures to these air pollutants during pregnancy by weighting the average of the twelve nearest monitoring stations within 30km of each 100m×100m grid cell by an inverse squared distance, and then the average exposure concentrations for gestational months, trimesters and the entire pregnancy were calculated. Adjusted conditional logistic regression models were used to estimate the odds ratios (ORs) per 10μg/m³ increment in PM_2.5 and by PM_2.5 quartiles during different gestational periods.

RESULTS

In this study, the estimated mean values of PM_2.5, NO₂, and SO₂ exposure during the entire pregnancy were 88.0, 54.6, and 63.1μg/m³, respectively. Term low birth weight (TLBW) increased in association with per 10μg/m³ increment in PM_2.5 for the 8th month [OR=1.13, 95% confidence interval (CI): 1.04, 1.22], the 9th month (OR=1.06, 95% CI: 0.99, 1.15), the third trimester (OR=1.17, 95% CI: 1.05, 1.29), and the entire pregnancy (OR=1.38, 95% CI: 1.07, 1.77) in models adjusted for one pollutant (PM_2.5). In models categorizing the PM_2.5 exposure by quartiles, comparing the second, third, and highest with the lowest PM_2.5 exposure quartile, the PM_2.5 was positively associated with TLBW during the 8th month (OR: 1.77, 95% CI: 1.09, 2.88; OR: 1.77, 95% CI: 1.03, 3.04; OR: 1.92, 95% CI: 1.04, 3.55, respectively) and for the 9th month, only association for exposure in the third versus the lowest quartile was significant (OR: 1.91, 95% CI: 1.02, 3.58).

CONCLUSIONS

The study provides evidence that exposure to PM_2.5 during pregnancy might be associated with the risk of TLBW in the context of very high pollution level of PM_2.5, and the 8th and 9th months were identified as potentially relevant exposure windows.

Early-life exposure to air pollutants and adverse pregnancy outcomes: protocol for a prospective cohort study in Beijing

INTRODUCTION

The association between early exposure to ambient air pollution and adverse pregnancy outcomes in China is unclear. This study will assess the risk of early-life exposure to air pollutants in Beijing and explore the viability of 8-hydroxydeoxyguanosine (8-OHdG) as a biological indicator to assess oxidative stress induced by early-life exposure to air pollution.

METHODS AND ANALYSIS

Here, 2500 women with singleton pregnancies and their infants will be recruited from the Beijing Obstetrics and Gynecology Hospital. We will collect nine types of biological samples, including maternal serum, urine, placental tissue, umbilical cord tissue and umbilical cord blood during all three trimesters. The air pollution data (particulate matter (PM)2.5, PM10 and similar factors) will be recorded at official fixed-site monitoring stations closest to where the pregnant women live. We plan to assess the effect of air pollutants on adverse pregnancy outcomes and infant respiratory and circulatory disease using Cox regression and competitive risk analysis and explore possible critical windows of exposure during pregnancy using daily pollutant concentrations averaged over various periods of pregnancy combined with individual activity and physiological parameters. Maternal and umbilical cord blood samples (1000 samples) will be randomly selected for 8-OHdG assays to assess the correlation between exposures to air pollutants and oxidative stress. We will determine whether air pollutant exposure or 8-OHdG levels are associated with adverse pregnancy outcomes. SPSS and SAS statistical software will be used for data analysis. Cox regression and competing risk analysis will be used to compute the HR and population attributable risk.

ETHICS AND DISSEMINATION

This research protocol has already been approved by the Medical Ethics Committee of Beijing Obstetrics and Gynecology Hospital. Written informed consent will be obtained from all study participants prior to enrolment. The results will be published in peer-reviewed journals or disseminated through conference presentations.

TRIAL REGISTRATION NUMBER

This study has been registered in WHO International Clinical Trial Register-Chinese Clinical Trial Registry under registrationnumber ChiCTR-ROC-16010181 (http :// www.chictr.org.cn / showproj.aspx ?proj=17328).

Effects of ambient PM1 air pollution on daily emergency hospital visits in China: an epidemiological study

BACKGROUND

China is experiencing severe ambient air pollution. However, few studies anywhere have examined the health effects of PM₁ (particulate matter with aerodynamic diameter <1 μm), which are a major part of PM_2·5 (particulate matter with aerodynamic diameter <2·5 μm) and even potentially more harmful than PM_2·5. We aimed to estimate the effects of ambient daily PM₁ and PM_2·5 concentrations on emergency hospital visits in China.

METHODS

In this epidemiological study, we collected daily counts of emergency hospital visits from the 28 largest hospitals in 26 Chinese cities from Sept 9, 2013, to Dec 31, 2014. Ground-based monitoring data for PM₁ and PM_2·5 and meteorological data were also collected. Hospital-specific emergency hospital visits associated with PM₁ or PM_2·5 were evaluated with a time-series Poisson regression. The effect estimates were then pooled at the country level using a random-effects meta-analysis.

FINDINGS

The mean daily concentration of PM₁ in all cities was 42·5 μg/m³ (SD 34·6) and of PM_2·5 was 51·9 μg/m³ (41·5). The mean daily number of emergency hospital visits in all hospitals was 278 (SD 173). PM₁ and PM_2·5 concentrations were significantly associated with an increased risk of emergency hospital visits at lag 0-2 days (cumulative relative risk [RRs] 1·011 [95% CI 1·006-1·017] for a 10 μg/m³ increase in PM₁ and 1·010 [1·005-1·016] for a 10 μg/m³ increase in PM_2·5). Slightly higher RRs of ambient PM₁ and PM_2·5 pollution were noted among women and children than among men and adults, respectively, but without statistical significance. Given a cause-effect association, 4·47% (95% CI 2·05-6·79) and 5·05% (2·23-7·75) of daily emergency hospital visits in China could be attributed to ambient PM₁ and PM_2·5 pollution, respectively.

INTERPRETATION

Exposure to both ambient PM₁ and PM_2·5 were significantly associated with increased emergency hospital visits. The results suggest that most of the health effects of PM_2·5 come from PM₁.

FUNDING

None.

Different exposure levels of fine particulate matter and preterm birth: a meta-analysis based on cohort studies

The previous studies estimated the association between PM_2.5 (particulate matter with aerodynamic diameter less than or equal to 2.5 μm) exposure during pregnancy and preterm birth, only considered and highlighted the hazard effects of high levels of air pollutant exposure, and underestimated that low levels of pollutant exposure might also affect pregnancy outcome. We conducted a meta-analysis of 11 cohort studies, a total of more than 1,500,000 subjects. The results of these studies were pooled by exposure levels and study periods. PM_2.5 exposure during pregnancy was positively associated with preterm birth (OR = 1.15, 95% CI = 1.07-1.23), and during the first trimester of pregnancy, low levels of PM_2.5 exposure were also positively associated with preterm birth (OR = 1.17, 95% CI = 1.04-1.30). It is important to protect pregnant women from PM_2.5 exposures, especially during their first trimester of pregnancy even when the ambient PM_2.5 concentration is relatively low. More relevant health policy should be carried out to prevent hazard effect of air pollutants.

Temperature exposure during pregnancy and birth outcomes: An updated systematic review of epidemiological evidence

Seasonal patterns of birth outcomes have been observed worldwide, and there was increasing evidence that ambient temperature played as a trigger of adverse birth outcomes, such as preterm birth (PTB), low birth weight (LBW), and stillbirth. To systematically review updated epidemiological evidence about the relationship between temperature exposure during pregnancy and PTB, LBW, and stillbirth, we searched for related studies published in English from electronic databases and references of identified papers. We only included original articles that directly reported the effects of prenatal temperature exposure on birth outcomes. The characteristics and main findings of included studies were examined. A total of 36 epidemiological studies were finally included in this review. Most of these studies focused on PTB and LBW, while less attention has been paid to stillbirth that was relatively rare in the occurrence. Several designs including ecological (e.g., descriptive and time-series) and retrospective cohort studies (e.g., case-crossover and time-to-event) were applied to assess temperature effects on birth outcomes. Temperature metrics and exposure windows varied greatly in these investigations. Exposure to high temperature was generally found to be associated with PTB, LBW, and stillbirth, while several studies also reported the adverse impact of low temperature on birth outcomes of PTB and LBW. Despite no conclusive causality demonstrated, the current evidence for adverse effect on birth outcomes was stronger for heat than for cold. In summary, the evidence linking birth outcomes with ambient temperature was still very limited. Consequently, more related studies are needed worldwide and should be conducted in diversified climate zones, so as to further ascertain the association between temperature and birth outcomes. Future studies should focus on more sophisticated study designs, more accurate estimation of temperature exposure during pregnancy, and more efficient methods to find out the exposure windows, as well as cold-related effects on birth outcomes.

Risk factors for low birth weight and preterm birth: A population-based case-control study in Wuhan, China

Low birth weight (LBW) and preterm birth (PB) are associated with newborn mortality and diseases in adulthood. We explored factors related to LBW and PB by conducting a population-based case-control study from January 2011 to December 2013 in Wuhan, China. A total of 337 LBW newborn babies, 472 PB babies, and 708 babies with normal birth weights and born from term pregnancies were included in this study. Information of newborns and their parents was collected by trained investigators using questionnaires and referring to medical records. Univariate and logistic regression analyses with the stepwise selection method were used to determine the associations of related factors with LBW and PB. Results showed that maternal hypertension (OR=6.78, 95% CI: 2.27-20.29, P=0.001), maternal high-risk pregnancy (OR=1.53, 95% CI: 1.06-2.21, P=0.022), and maternal fruit intake ≥300 g per day during the first trimester (OR=1.70, 95% CI: 1.17-2.45, P=0.005) were associated with LBW. BMI ≥24 kg/m² of mother prior to delivery (OR=0.48, 95% CI: 0.32-0.74, P=0.001) and gestation ≥37 weeks (OR=0.01, 95% CI: 0.00-0.02, P<0.034) were protective factors for LBW. Maternal hypertension (OR=3.36, 95% CI: 1.26-8.98, P=0.016), maternal high-risk pregnancy (OR=4.38, 95% CI: 3.26-5.88, P<0.001), maternal meal intake of only twice per day (OR=1.88, 95% CI: 1.10-3.20, P=0.021), and mother liking food with lots of aginomoto and salt (OR=1.60, 95% CI: 1.02-2.51, P=0.040) were risk factors for PB. BMI ≥24 kg/m² of mother prior to delivery (OR=0.66, 95% CI: 0.47-0.93, P=0.018), distance of house from road ≥36 meters (OR=0.72, 95% CI: 0.53-0.97, P=0.028), and living in rural area (OR= 0.60, 95% CI: 0.37-0.99, P=0.047) were protective factors for PB. Our study demonstrated some risk factors and protective factors for LBW and PB, and provided valuable information for the prevention of the conditions among newborns.

Burden of disease attributed to ambient PM2.5 and PM10 exposure in 190 cities in China

Particulate air pollution is becoming a serious public health concern in urban cities of China. Association of disability-adjusted life years (DALYs) and economic loss with air pollution-related health effects demand quantitative analysis for correctional measures in air quality. This study applies an epidemiology-based exposure-response function to obtain the quantitative estimate of health impact of particulate matter PM_2.5 and PM₁₀ across 190 cities of China during years 2014-2015. The annual average concentration of PM_2.5 and PM₁₀ is 57 ± 18 μg/m³ (ranging from 18 to 119 μg/m³) and 97.7 ± 34.2 μg/m³ (ranging from 33.5 to 252.8 μg/m³), respectively. Based on the present study, the total estimated annual premature mortality due to PM_2.5 is 722,370 [95% confidence interval (CI) = 322,716-987,519], 79% of which accounts for adult cerebrovascular disease (stroke) and ischemic heart disease (IHD). The premature mortality in megacities is very high, such as Chongqing (25,162/year), Beijing (19,702/year), Shanghai (19,617/year), Tianjin (13,726/year), and Chengdu (12,356/year). PM₁₀ pollution has caused 1,491,774 (95% CI = 972,770-1,960,303) premature deaths (age >30) in China. Further, 3,614,064 cases of chronic bronchitis (CB); 13,759,894 cases of asthma attack among all ages; 191,709 COPD-related hospital admission (HA) cases; 499,048 respiratory-related HA; 357,816 cerebrovascular HA; and 308,129 cardiovascular-related HA due to PM₁₀ pollution have been estimated during 2014-2015. Chongqing, Beijing, Baoding, Tianjin, and Shijiazhuang are the top five contributors to pollution-related mortality, accounting for 3.10, 2.71, 2.49, 2.20, and 2.02%, respectively, of the total deaths caused by PM₁₀ pollution. The total DALYs associated with PM_2.5 and PM₁₀ pollution in China is 7.2 and 20.66 million in 2014-2015, and mortality and chronic bronchitis shared about 93.3% of the total DALYs for PM₁₀. During this period, the economic cost of health impact due to PM₁₀ is approximately US$304,122 million, which accounts for about 2.94% of China's gross domestic product (GDP). Megacities are expected to contribute relatively more to the total costs. The present methodology could be used as a tool to help policy makers and pollution control board authorities, to further analyze costs and benefits of air pollution management programs in China.

Preterm birth associated with maternal fine particulate matter exposure: A global, regional and national assessment

Reduction of preterm births (<37 completed weeks of gestation) would substantially reduce neonatal and infant mortality, and deleterious health effects in survivors. Maternal fine particulate matter (PM_2.5) exposure has been identified as a possible risk factor contributing to preterm birth. The aim of this study was to produce the first estimates of ambient PM_2.5-associated preterm births for 183 individual countries and globally. To do this, national, population-weighted, annual average ambient PM_2.5 concentration, preterm birth rate and number of livebirths were combined to calculate the number of PM_2.5-associated preterm births in 2010 for 183 countries. Uncertainty was quantified using Monte-Carlo simulations, and analyses were undertaken to investigate the sensitivity of PM_2.5-associated preterm birth estimates to assumptions about the shape of the concentration-response function at low and high PM_2.5 exposures, inclusion of provider-initiated preterm births, and exposure to indoor air pollution. Globally, in 2010, the number of PM_2.5-associated preterm births was estimated as 2.7 million (1.8-3.5 million, 18% (12-24%) of total preterm births globally) with a low concentration cut-off (LCC) set at 10μgm^-3, and 3.4 million (2.4-4.2 million, 23% (16-28%)) with a LCC of 4.3μgm^-3. South and East Asia, North Africa/Middle East and West sub-Saharan Africa had the largest contribution to the global total, and the largest percentage of preterm births associated with PM_2.5. Sensitivity analyses showed that PM_2.5-associated preterm birth estimates were 24% lower when provider-initiated preterm births were excluded, 38-51% lower when risk was confined to the PM_2.5 exposure range in the studies used to derive the effect estimate, and 56% lower when mothers who live in households that cook with solid fuels (and whose personal PM_2.5 exposure is likely dominated by indoor air pollution) were excluded. The concentration-response function applied here derives from a meta-analysis of studies, most of which were conducted in the US and Europe, and its application to the areas of the world where we estimate the greatest effects on preterm births remains uncertain. Nevertheless, the substantial percentage of preterm births estimated to be associated with anthropogenic PM_2.5 (18% (13%-24%) of total preterm births globally) indicates that reduction of maternal PM_2.5 exposure through emission reduction strategies should be considered alongside mitigation of other risk factors associated with preterm births.

Environmental chemicals and preterm birth: Biological mechanisms and the state of the science

PURPOSE OF REVIEW

Preterm birth is a significant worldwide health problem of uncertain origins. The extant body of literature examining environmental contaminant exposures in relation to preterm birth is extensive but results remain ambiguous for most organic pollutants, metals and metalloids, and air pollutants. In the present review we examine recent epidemiologic studies investigating these associations, and identify recent advances and the state of the science. Additionally, we highlight biological mechanisms of action in the pathway between chemical exposures and preterm birth, including inflammation, oxidative stress, and endocrine disruption, that deserve more attention in this context.

RECENT FINDINGS

Important advances have been made in the study of the environment and preterm birth, particularly in regard to exposure assessment methods, exploration of effect modification by co-morbidities and exposures, and in identification of windows of vulnerability during gestation. There is strong evidence for an association between maternal exposure to some persistent pesticides, lead, and fine particulate matter, but data on other contaminants is sparse and only suggestive trends can be noted with the current data.

SUMMARY

Beyond replicating current findings, further work must be done to improve understanding of mechanisms underlying the associations observed between environmental chemical exposures and preterm birth. By examining windows of vulnerability, disaggregating preterm birth by phenotypes, and measuring biomarkers of mechanistic pathways in these epidemiologic studies we can improve our ability to detect associations with exposure, provide additional evidence for causality in an observational setting, and identify opportunities for intervention.

Exposure and health impact evaluation based on simultaneous measurement of indoor and ambient PM2.5 in Haidian, Beijing

Because people spend most of their time indoors, the characterization of indoor air quality is important for exposure assessment. Unfortunately, indoor air data are scarce, leading to a major data gap in risk assessment. In this study, PM_2.5 concentrations in both indoor and outdoor air were simultaneously measured using on-line particulate counters in 13 households in Haidian, Beijing for both heating and non-heating seasons. A bimodal distribution of PM_2.5 concentrations suggests rapid transitions between polluted and non-polluted situations. The PM_2.5 concentrations in indoor and outdoor air varied synchronously, with the indoor variation lagging. The lag time in the heating season was longer than that in the non-heating season. The particle sizes in indoor air were smaller than those in ambient air in the heating season and vice versa in the non-heating season. PM_2.5 concentrations in indoor air were generally lower than those in ambient air except when ambient concentrations dropped sharply to very low levels or there were internal emissions from cooking or other activities. The effectiveness of an air cleaner to reduce indoor PM_2.5 concentrations was demonstrated. Non-linear regression models were developed to predict indoor air PM_2.5 concentrations based on ambient data with lag time incorporated. The models were applied to estimate the overall population exposure to PM_2.5 and the health consequences in Haidian. The health impacts would be significantly overestimated without the indoor exposure being taken into consideration, and this bias would increase as the ambient air quality improved in the future.

Spatial and temporal trends in the mortality burden of air pollution in China: 2004-2012

While recent assessments have quantified the burden of air pollution at the national scale in China, air quality managers would benefit from assessments that disaggregate health impacts over regions and over time. We took advantage of a new 10×10km satellite-based PM_2.5 dataset to analyze spatial and temporal trends of air pollution health impacts in China, from 2004 to 2012. Results showed that national PM_2.5 related deaths from stroke, ischemic heart disease and lung cancer increased from approximately 800,000 cases in 2004 to over 1.2 million cases in 2012. The health burden exhibited strong spatial variations, with high attributable deaths concentrated in regions including the Beijing-Tianjin Metropolitan Region, Yangtze River Delta, Pearl River Delta, Sichuan Basin, Shandong, Wuhan Metropolitan Region, Changsha-Zhuzhou-Xiangtan, Henan, and Anhui, which have heavy air pollution, high population density, or both. Increasing trends were found in most provinces, but with varied growth rates. While there was some evidence for improving air quality in recent years, this was offset somewhat by the countervailing influences of in-migration together with population growth. We recommend that priority areas for future national air pollution control policies be adjusted to better reflect the spatial hotspots of health burdens. Satellite-based exposure and health impact assessments can be a useful tool for tracking progress on both air quality and population health burden reductions.

Do the pollution related to high-traffic roads in urbanised areas pose a significant threat to the local population?

Many large neighbourhoods are located near heavy-traffic roads; therefore, it is necessary to control the levels of air pollution near road exposure. The primary air pollutants emitted by motor vehicles are CO, NO2 and PM. Various investigations identify key health outcomes to be consistently associated with NO2 and CO. The objective of this study was the measurement-based assessment for determining whether by high-traffic roads, such as motorways and express ways, and the concentrations of CO and NO2 are within normal limits and do not pose threat to the local population. Average daily values (arithmetic values calculated for 1-h values within 24 h or less, depending on result availability) were measured for concentrations of NO2 and CO by automatic stations belonging to the Voivodship Environmental Protection Inspectorate in Katowice, in areas with similar dominant source of pollutant emission. The measurements were made in three sites: near the motorway and expressway, where the average daily traffic intensity is 100983 and 35414 of vehicles relatively. No evidence was found of exceeding average daily values equal to the maximum allowable NO2 concentration due to the protection of human health in the measurement area of the stations. No daily average values exceeding the admissible CO concentration (8-h moving average) were noted in the examined period. The results clearly show lack of hazards for general population health in terms of increased concentrations of CO and NO2 compounds that are closely related to high intensity car traffic found on selected motorways and speedways located near the city centres.