Impacts of heat and wildfire on preterm birth.

BACKGROUND: Climate change continues to increase the frequency, intensity, and duration of heat events and wildfires, both of which are associated with adverse pregnancy outcomes. Few studies simultaneously evaluated exposures to these increasingly common exposures. OBJECTIVES: We investigated the relationship between exposure to heat and wildfire smoke and preterm birth (PTB). METHODS: In this time-stratified case-crossover study, participants consisted of 85,806 California singleton PTBs (20-36 gestational weeks) from May through October of 2015-2019. Birthing parent ZIP codes were linked to high-resolution daily weather, PM2.5 from wildfire smoke, and ambient air pollution data. Heat day was defined as a day with apparent temperature >98th percentile within each ZIP code and heat wave was defined as ≥2 consecutive heat days. Wildfire-smoke day was defined as a day with any exposure to wildfire-smoke PM2.5. Conditional logistic regression was used to calculate the odds ratio (OR) and 95% confidence intervals (CI) comparing exposures during a hazard period (lags 0-6) compared to control periods. Analyses were adjusted for relative humidity, fine particles, and ozone. RESULTS: Wildfire-smoke days were associated with 3.0% increased odds of PTB (ORlag0: 1.03, CI: 1.00-1.05). Compared with white participants, associations appeared stronger among Black, Hispanic, Asian, and American Indians/Alaskan Native participants. Heatwave days (ORlag2: 1.07, CI: 1.02-1.13) were positively associated with PTB, with stronger associations among those simultaneously exposed to wildfire smoke days (ORlag2: 1.19, CI: 1.11-1.27). Similar findings were observed for heat days and when other temperature metrics (e.g., maximum, minimum) were used. DISCUSSION: Heat and wildfire increased PTB risk with evidence of synergism. As the occurrence and co-occurrence of these events increase, exposure reduction among pregnant people is critical, especially among racial/ethnic minorities.

Air pollution and preterm birth: A time-stratified case-crossover study in the San Joaquin Valley of California.

BACKGROUND: Air pollution is linked to preterm birth (PTB), but existing studies are primarily focused on chronic exposures, conducted in areas with moderate pollution, and/or subject to confounding. OBJECTIVES: We investigated short-term associations between two pollutants [particulate matter <2.5 microns (PM2.5 ) and ozone] and PTB, and estimated excess PTB cases potentially attributed to these pollutants. METHODS: This time-stratified case-crossover study includes 196,970 singleton pregnancies affected by PTB and early term birth from the San Joaquin Valley (SJV), California, USA (2007-2015). Daily ozone and PM2.5 concentrations were estimated by the SJV Air Pollution Control District and geospatially linked to maternal zip code. We used conditional logistic regression models to estimate the odds ratio (OR) and 95% confidence intervals (CI) for the associations between an interquartile range (IQR) increase in pollutants and very preterm (VPTB, 20-34 weeks), moderate preterm (MPTB, 34-36 weeks) and early term births (ETB, 37-38 weeks). We adjusted all models for co-pollutants and meteorological factors. RESULTS: During warm seasons (May-October), an IQR increase in ozone was associated with 9-11% increased odds of VPTB from lag 0 (ORlag0 1.09, 95% CI 1.04,1.16) to lag 7 (ORlag7 1.11, 95% CI 1.04,1.16). Findings were consistent for MPTB and ETB. Ozone was potentially responsible for an excess of 3-6 VPTBs, 7-9 PTBs and 24-42 ETBs per 1,000 singleton deliveries. During cold seasons (November-April), increased PM2.5 exposure was associated with 5-6% increased odds of VPTB beginning at lag 3 (ORlag3 1.06, 95% CI 1.02,1.11). PM2.5 was associated with an excess of 1-3 VPTBs, 0-3 MPTBs and 6-18 ETBs per 1,000 singleton deliveries. CONCLUSIONS: PM2.5 and ozone are associated with increased risk of VPTB, MPTB and ETB within one week of exposure and are potential contributors to the increasing PTB trend. More research is needed to further understand the role of air pollution on PTB risk.

Air pollution and neurological development in children.

Pregnancy and early childhood are periods with high plasticity in neurological development. Environmental perturbations during these sensitive windows can have lifelong developmental consequences. This review summarizes key findings relevant to the effects of air pollution on neurological development. Mounting evidence suggests that exposure to air pollution, both during pregnancy and childhood, is associated with childhood developmental outcomes ranging from changes in brain structures to subclinical deficits in developmental test scores, and, ultimately, developmental disorders such as attention-deficit/hyperactivity disorders or autism spectrum disorders. Although the biological mechanisms of effects remain to be elucidated, multiple pathways are probably involved and include oxidative stress, inflammation, and/or endocrine disruption. Given the alarming global increase in developmental disorders in recent years, and increased human exposures to pollution, it is critical to reduce personal and community-level exposures through tight collaboration of interdisciplinary and multi-level bodies including community partners, physicians, industry partners, policy makers, public health practitioners, and researchers. WHAT THIS PAPER ADDS: Exposure to air pollution is associated with a range of childhood developmental complications. Biological mechanisms may include oxidative stress, inflammation, and endocrine disruption.

Joint effects of ethnic enclave residence and ambient volatile organic compounds exposure on risk of gestational diabetes mellitus among Asian/Pacific Islander women in the United States.

BACKGROUND: Asian/Pacific Islander (API) communities in the United States often reside in metropolitan areas with distinct social and environmental attributes. Residence in an ethnic enclave, a socially distinct area, is associated with lower gestational diabetes mellitus (GDM) risk, yet exposure to high levels of air pollution, including volatile organic compounds (VOCS), is associated with increased GDM risk. We examined the joint effects of ethnic enclaves and VOCs to better understand GDM risk among API women, the group with the highest prevalence of GDM. METHODS: We examined 9069 API births in the Consortium on Safe Labor (19 hospitals, 2002-2008). API ethnic enclaves were defined as areas ≥66th percentile for percent API residents, dissimilarity (geographic dispersal of API and White residents), and isolation (degree that API individuals interact with another API individual). High levels of 14 volatile organic compounds (VOC) were defined as ≥75th percentile. Four joint categories were created for each VOC: Low VOC/Enclave (reference group), Low VOC/No Enclave, High VOC/Enclave, High VOC/No Enclave. GDM was reported in medical records. Hierarchical logistic regression estimated odds ratios (OR) and 95% confidence intervals (95%CI) between joint exposures and GDM, adjusted for maternal factors and area-level poverty. Risk was estimated for 3-months preconception and first trimester exposures. RESULTS: Enclave residence was associated with lower GDM risk regardless of VOC exposure. Preconception benzene exposure was associated with increased risk when women resided outside enclaves [High VOC/No Enclave (OR:3.45, 95%CI:1.77,6.72)], and the effect was somewhat mitigated within enclaves, [High VOC/Enclave (OR:2.07, 95%:1.09,3.94)]. Risks were similar for 12 of 14 VOCs during preconception and 10 of 14 during the first trimester. CONCLUSIONS: API residence in non-enclave areas is associated with higher GDM risk, regardless of VOC level. Ethnic enclave residence may mitigate effects of VOC exposure, perhaps due to lower stress levels. The potential benefit of ethnic enclaves warrants further study.

Ambient temperature and stillbirth: Risks associated with chronic extreme temperature and acute temperature change.

BACKGROUND: Ambient temperature events are increasing in frequency and intensity. Our prior work in a U.S. nationwide study suggests a strong association between both chronic and acute temperature extremes and stillbirth risk. OBJECTIVE: We attempted to replicate our prior study by assessing stillbirth risk associated with average whole-pregnancy temperatures and acute ambient temperature changes in a low-risk U.S. METHODS: Singleton deliveries in the NICHD Consecutive Pregnancies Study (Utah, 2002-2010; n = 112,005) were identified using electronic medical records. Ambient temperature was derived from the Weather Research and Forecasting model. Binary logistic regression determined the adjusted odds ratio (aOR) and 95% confidence interval (95% CI) for stillbirth associated with whole-pregnancy exposure to extreme cold (<10th percentile) and hot (>90th percentile) versus moderate (10th-90th percentiles) average temperature, adjusting for maternal demographics, season of conception, hypertensive disorders of pregnancy, and gestational diabetes. In a case-crossover analysis, we estimated the stillbirth aOR and 95% CI for each 1° Celsius increase during the week prior to delivery using conditional logistic regression. In both models, we adjusted for relative humidity, ozone, and fine particulates. RESULTS: We observed 500 stillbirth cases among 498 mothers. Compared to moderate temperatures, whole-pregnancy exposure to extreme cold (aOR: 4.42, 95% CI:3.43, 5.69) and hot (aOR: 5.06, 95% CI: 3.34, 7.68) temperatures were associated with stillbirth risk. Case-crossover models observed a 7% increased odds (95% CI: 1.04, 1.10) associated with each 1° Celsius increase during the week prior to delivery. DISCUSSION: Both chronic and acute ambient temperature were associated with odds of stillbirth in this low-risk population, similar to our prior nationwide findings. Future increases in temperature extremes are likely and the observed risk in a low-risk population suggests this association merits attention.

Ozone pollution and asthma emergency department visits in the Central Valley, California, USA, during June to September of 2015: a time-stratified case-crossover analysis.

Objective: The San Joaquin Valley (SJV) exceeds the state and national standards for ozone (O3). This study investigates whether short-term exposure to O3 is associated with asthma emergency department (ED) visits. Methods: We identified 1,101 ED visits in June-September of 2015 in SJV, California, who lived within 15 km of active air monitors. Conditional logistic regression models were used to obtain the odds ratio (OR) and 95% confidence interval (CI) associated with an interquartile (IQR) increase in ozone. We explored the potential effect modification by sex (female and male), race (White, Black and Hispanic), age (2-5, 6-18, 19-40, 41-64 and > = 65) and county (Merced, Madera, Kings, Fresno and Kern). Results: An IQR range (18.1 ppb) increase in O3 exposure three days before an asthma attack (lag 3) was associated with a 6.6% [OR: 1.066 (95% CI: 1.032, 1.082)] increase in the odds of having an asthma ED visit. The overall ORs differed across age groups and races/ethnicities, with strongest for children aged 6-18 years [OR: 1.219 (95% CI: 1.159, 1.280)], adults 19-40 years [OR: 1.102 (95% CI: 1.053, 1.154)] and Blacks [OR: 1.159 (95% CI: 1.088, 1.236)], respectively. O3 exposure was not positively associated with asthma ED visits for Whites, while it was for other underrepresented groups. Fresno had the highest number of asthma ED visits and positive association among all five counties. Conclusion: We found that O3 exposure is associated with asthma ED visits in the SJV.

Prenatal and early life exposures to ambient air pollution and development.

BACKGROUND: Residential proximity to major roadways, and prenatal exposures to particulate matter <2.5 µm (PM2.5) and ozone (O3) are linked to poor fetal outcomes but their relationship with childhood development is unclear. OBJECTIVES: We investigated whether proximity to major roadways, or prenatal and early-life exposures to PM2.5 and O3 increase the risk of early developmental delays. STUDY DESIGN: Prospective cohort. SETTINGS: New York State excluding New York City. PARTICIPANTS: 4089 singletons and 1016 twins born between 2008 and 2010. EXPOSURES: Proximity to major roadway was calculated using road network data from the NY Department of Transportation. Concentrations of PM2.5 and O3 estimated by the Environmental Protection Agency Downscaler models were spatiotemporally linked to each child's prenatal and early-life addresses incorporating residential history, and locations of maternal work and day-care. OUTCOMES: Parents reported their children's development at ages 8, 12, 18, 24, 30 and 36 months in five domains using the Ages and Stages Questionnaire. Generalized mixed models estimated the relative risk (RR) and 95% CI for failing any developmental domain per 10 units increase in PM2.5 and O3, and for those living <1000 m away from a major roadway compared to those living further. Models adjusted for potential confounders. RESULTS: Compared to those >1000 m away from a major roadway, those resided 50-100 m [RR: 2.12 (1.00-4.52)] and 100-500 m [RR: 2.07 (1.02-4.22)] away had twice the risk of failing the communication domain. Prenatal exposures to both PM2.5 and ozone during various pregnancy windows had weak but significant associations with failing any developmental domain with effects ranging from 1.6% to 2.7% for a 10 µg/m3 increase in PM2.5 and 0.7%-1.7% for a 10 ppb increase in ozone. Average daily postnatal ozone exposure was positively associated with failing the overall screening by 8 months [3.3% (1.1%-5.5%)], 12 months [17.7% (10.4%-25.5%)], and 30 months [7.6%, (1.3%-14.3%)]. Findings were mixed for postnatal PM2.5 exposures. CONCLUSIONS: In this prospective cohort study, proximity to major roadway and prenatal/early-life exposures to PM2.5 and O3 were associated with developmental delays. While awaiting larger studies with personal air pollution assessment, efforts to minimize air pollution exposures during critical developmental windows may be warranted.

Acute Associations Between Outdoor Temperature and Premature Rupture of Membranes.

BACKGROUND: Extreme ambient temperatures have been linked to preterm birth. Preterm premature rupture of membranes is a common precursor to preterm birth but is rarely studied in relation to temperature. METHODS: We linked 15,381 singleton pregnancies with premature rupture of membranes from a nationwide US obstetrics cohort (2002-2008) to local temperature. Case-crossover analyses compared daily temperature during the week preceding delivery and the day of delivery to 2 control periods, before and after the case period. Conditional logistic regression models calculated the odds ratio (OR) and 95% confidence intervals (CIs) of preterm and term premature rupture of membranes for a 1°C increase in temperature during the warm (May-September) and cold (October-April) season separately after adjusting for humidity, barometric pressure, ozone, and particulate matter. RESULTS: During the warm season, 1°C increase during the week before delivery was associated with a 5% (95% CI, 3%, 6%) increased preterm premature rupture of membranes risk, and a 4% (95% CI, 3%, 5%) increased term premature rupture of membranes risk. During the cold season, 1°C increase was associated with a 2% decreased risk for both preterm (95% CI, 1%, 3%) and term premature rupture of membranes (95% CI, 1%, 3%). The day-specific associations for the week before delivery were similar, but somewhat stronger for days closer to delivery. CONCLUSIONS: Relatively small ambient temperature changes were associated with the risk of both preterm and term premature of membranes. Given the adverse consequences of premature rupture of membranes and concerns over global climate change, these findings merit further investigation. See video abstract at, http://links.lww.com/EDE/B312.

Time-varying cycle average and daily variation in ambient air pollution and fecundability.

STUDY QUESTION: Does ambient air pollution affect fecundability? SUMMARY ANSWER: While cycle-average air pollution exposure was not associated with fecundability, we observed some associations for acute exposure around ovulation and implantation with fecundability. WHAT IS KNOWN ALREADY: Ambient air pollution exposure has been associated with adverse pregnancy outcomes and decrements in semen quality. STUDY DESIGN, SIZE, DURATION: The LIFE study (2005-2009), a prospective time-to-pregnancy study, enrolled 501 couples who were followed for up to one year of attempting pregnancy. PARTICIPANTS/MATERIALS, SETTING, METHODS: Average air pollutant exposure was assessed for the menstrual cycle before and during the proliferative phase of each observed cycle (n = 500 couples; n = 2360 cycles) and daily acute exposure was assessed for sensitive windows of each observed cycle (n = 440 couples; n = 1897 cycles). Discrete-time survival analysis modeled the association between fecundability and an interquartile range increase in each pollutant, adjusting for co-pollutants, site, age, race/ethnicity, parity, body mass index, smoking, income and education. MAIN RESULTS AND THE ROLE OF CHANCE: Cycle-average air pollutant exposure was not associated with fecundability. In acute models, fecundability was diminished with exposure to ozone the day before ovulation and nitrogen oxides 8 days post ovulation (fecundability odds ratio [FOR] 0.83, 95% confidence interval [CI]: 0.72, 0.96 and FOR 0.84, 95% CI: 0.71, 0.99, respectively). However, particulate matter ≤10 microns 6 days post ovulation was associated with greater fecundability (FOR 1.25, 95% CI: 1.01, 1.54). LIMITATIONS, REASONS FOR CAUTION: Although our study was unlikely to be biased due to confounding, misclassification of air pollution exposure and the moderate study size may have limited our ability to detect an association between ambient air pollution and fecundability. WIDER IMPLICATIONS OF THE FINDINGS: While no associations were observed for cycle-average ambient air pollution exposure, consistent with past research in the United States, exposure during critical windows of hormonal variability was associated with prospectively measured couple fecundability, warranting further investigation. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Longitudinal Investigation of Fertility and the Environment study contract nos. #N01-HD-3-3355, NO1-HD-#-3356, N01-HD-3-3358 and the Air Quality and Reproductive Health Study Contract No. HHSN275200800002I, Task Order No. HHSN27500008). We declare no conflict of interest.

Ambient air pollution and semen quality.

BACKGROUND: Ambient air pollution is associated with systemic increases in oxidative stress, to which sperm are particularly sensitive. Although decrements in semen quality represent a key mechanism for impaired fecundability, prior research has not established a clear association between air pollution and semen quality. To address this, we evaluated the association between ambient air pollution and semen quality among men with moderate air pollution exposure. METHODS: Of 501 couples in the LIFE study, 467 male partners provided one or more semen samples. Average residential exposure to criteria air pollutants and fine particle constituents in the 72 days before ejaculation was estimated using modified Community Multiscale Air Quality models. Generalized estimating equation models estimated the association between air pollutants and semen quality parameters (volume, count, percent hypo-osmotic swollen, motility, sperm head, morphology and sperm chromatin parameters). Models adjusted for age, body mass index, smoking and season. RESULTS: Most associations between air pollutants and semen parameters were small. However, associations were observed for an interquartile increase in fine particulates ≤2.5 µm and decreased sperm head size, including -0.22 (95% CI -0.34, -0.11) µm2 for area, -0.06 (95% CI -0.09, -0.03) µm for length and -0.09 (95% CI -0.19, -0.06) µm for perimeter. Fine particulates were also associated with 1.03 (95% CI 0.40, 1.66) greater percent sperm head with acrosome. CONCLUSIONS: Air pollution exposure was not associated with semen quality, except for sperm head parameters. Moderate levels of ambient air pollution may not be a major contributor to semen quality.

Invited Commentary: Ambient Environment and the Risk of Preterm Birth.

Preterm birth is a common adverse birth outcome known to be associated with increased infant mortality, and it often results in a higher burden of offspring morbidity in both the short and long terms. The potential for environmental factors, particularly air pollution and meteorological parameters, to increase preterm birth risk has received significant attention worldwide, but the findings are generally inconsistent, with variations in study designs and methods across populations and geographic locations. In the current issue of the Journal, Giorgis-Allemand et al. (Am J Epidemiol. 2017;185(4):247-258) take the field a step further than most prior investigations of the ambient environment. They examined the associations of ambient air pollution and meteorological factors with preterm risk among 13 cohorts across 11 European countries. No association with air pollution was observed, but associations with increased preterm birth risk were found for both increased atmospheric pressure and ambient temperature exposures during the first trimester. The study is notable in attempting to address several important issues that challenge the field, including exposure misclassification and defining critical windows of exposure. Their comprehensive evaluation of ambient exposures is to be commended.

Ambient Air Pollution and Risk of Gestational Hypertension.

Air pollution has been linked to hypertension in the general population, but data on gestational hypertension (GH) are limited. We investigated criteria air pollutants and air toxics during the period before conception and in early gestation in relation to GH risk in the Consortium on Safe Labor/Air Quality and Reproductive Health Study (United States, 2002-2008). Modified Community Multi-scale Air Quality models estimated air pollution exposures for 6,074 singleton pregnancies in which GH was present and 199,980 normotensive pregnancies. Generalized estimating equations estimated relative risks per interquartile-range increment for pollutants and high exposure (≥75th percentile) for air toxics after adjustment for major risk factors. For an interquartile-range increment, GH risk was significantly increased by 18% for sulfur dioxide during the 3 months before conception and, during gestational weeks 1-20, 17% for nitrogen oxides, 10% for particulate matter with an aerodynamic diameter <2.5 µm, 7% for particulate matter with an aerodynamic diameter <10 µm, and 22% for sulfur dioxide. High exposures to several polycyclic aromatic hydrocarbons before conception and during the first trimester were significantly associated with 8%-20% higher risk of GH. Further, preconceptional exposures to several volatile organic compounds were significantly associated with 11%-19% higher risk. Our findings suggest that early exposures to criteria air pollutants, particularly from transport emissions, and high exposure to several air toxics before conception may increase GH risk.

Ozone and hypertensive disorders of pregnancy in Florida: Identifying critical windows of exposure.

INTRODUCTION: Ozone (O3) has been linked to hypertensive disorders of pregnancy (HDP). However, inconsistent results have been reported, and no study has examined the critical exposure windows during pregnancy. MATERIALS AND METHODS: We used Florida birth vital statistics records to investigate the association between HDP and O3 exposure among 655,529 pregnancies with conception dates between 2005 and 2007. Individual O3 exposure was assessed at mothers' home address at the time of delivery using the Hierarchical Bayesian space-time statistical model. We examined the association during three predefined exposure windows including trimester 1, trimester 2, and trimesters 1&2, as well as in each week of the first two trimesters using distributed lag models. RESULTS: Pregnancies with HDP had a higher mean exposure to O3 (39.07 in trimester 1, 39.02 in trimester 2, and 39.06 in trimesters 1&2, unit: ppb) than those without HDP (38.65 in trimester 1, 38.57 in trimester 2, and 38.61 in trimesters 1&2, unit: ppb). In the adjusted logistic regression model, increased odds of HDP were observed for each 5 ppb increase in O3 (ORTrimester1=1.04, 95% CI: 1.03, 1.06; ORTrimester2=1.03, 95% CI: 1.02, 1.04; ORTrimester1&2=1.07, 95% CI: 1.05, 1.08). In the distributed lag models, elevated odds of HDP were observed with increased O3 exposure during the 1st to 24th weeks of gestation, with higher odds during early pregnancy. CONCLUSIONS: O3 exposure during pregnancy is related to increased odds of HDP, and early pregnancy appears to be a potentially critical window of exposure.

Ambient temperature and air quality in relation to small for gestational age and term low birthweight.

BACKGROUND: Exposures to extreme ambient temperature and air pollution are linked to adverse birth outcomes, but the associations with small for gestational age (SGA) and term low birthweight (tLBW) are unclear. We aimed to investigate exposures to site-specific temperature extremes and selected criteria air pollutants in relation to SGA and tLBW. METHODS: We linked medical records of 220,572 singleton births (2002-2008) from 12 US sites to local temperature estimated by the Weather Research and Forecasting model, and air pollution estimated by modified Community Multiscale Air Quality models. Exposures to hot (>95th percentile) and cold (<5th percentile) were defined using site-specific distributions of daily temperature over three-month preconception, each trimester, and whole-pregnancy. Average concentrations of five criteria air pollutants and six fine particulate matter constituents were also calculated for these pregnancy windows. Poisson regression with generalized estimating equations calculated the relative risks (RR) and 95% confidence intervals for SGA (weight <10th percentile conditional on gestational age and sex) and tLBW (≥37 weeks and <2500g) associated with an interquartile range increment of air pollutants, and cold or hot compared to mild (5-95th percentile) temperature. Models were adjusted for maternal demographics, lifestyle, and clinical factors, season, and site. RESULTS: Compared to mild temperature, cold exposure during trimester 2 [RR: 1.21 (1.05-1.38)], trimester 3 [RR: 1.18 (1.03-1.36)], and whole-pregnancy [RR: 2.57 (2.27-2.91)]; and hot exposure during trimester 3 [RR: 1.31 (1.15-1.50)] and whole-pregnancy [RR: 2.49 (2.20-2.83)] increased tLBW risk. No consistent association was observed between temperature and SGA. Air pollutant analyses were generally null but preconception elemental carbon was associated with a 4% increase in SGA while dust particles increased tLBW by 10%. Particulate matter ≤10µm in the second trimester and whole pregnancy also appeared related to tLBW. CONCLUSIONS: Our findings suggest prenatal exposures to extreme ambient temperature relative to usual environment may increase tLBW risk. Given concerns related to climate change, these findings merit further investigation.

Ambient temperature and risk of cardiovascular events at labor and delivery: A case-crossover study.

BACKGROUND: Extreme ambient temperatures are linked to cardiac events in the general population, but this relationship is unclear among pregnant women. We estimated the associations and attributable risk between ambient temperature and the risk of cardiovascular event at labor/delivery, and investigated whether these associations vary by maternal race/ethnicity. METHODS: We identified 680 women with singleton deliveries affected by cardiovascular events across 12 US sites (2002-2008). Average daily temperature during the week before, delivery day, and each of the seven days before delivery was estimated for each woman. In a case-crossover analysis, exposures during these hazard periods were compared to two control periods before and after delivery using conditional logistic regression adjusted for other environmental factors. RESULTS: During the cold season (October-April), 1°C lower during the week prior to delivery was associated with a 4% (95% CI: 1-7%) increased risk of having a labor/delivery affected by cardiovascular events including cardiac arrest and stroke. During the warm season (May-September), 1°C higher during the week prior was associated with a 7% (95% CI: 3-12%) increased risk. These risks translated to 13.4 and 23.9 excess events per 100,000 singleton deliveries during the cold and warm season, respectively. During the warm season, the risks were more pronounced on days closer to delivery and Black women appeared to be more susceptible to the same temperature increase. CONCLUSION: Small changes in temperature appear to affect the risk of having cardiovascular events at labor/delivery. Black women had a differentially higher warm season risk. These findings merit further investigation.

Associations Between Residential Proximity to Power Plants and Adverse Birth Outcomes.

Few studies have assessed the associations between residential proximity to power plants and adverse birth outcomes including preterm delivery (PTD), very preterm delivery (VPTD), and term low birth weight (LBW). We geocoded 423,719 singleton Florida births born from 2004 to 2005 and all active power plants and determined residential proximity to the nearest power plant for each birth. Prenatal exposure to particulate matter less than 2.5 µm in diameter for women living near different types of power plants was also determined by using National Environmental Public Health Tracking Network data. Logistic regression models were used to test the hypothesized associations. Women who lived closer to coal and solid waste power plants were exposed to higher levels of particulate matter less than 2.5 µm in diameter compared with other types. We observed a 1.8% (95% confidence interval (CI): 1.3, 2.3) increased odds for PTD, 2.2% (95% CI: 1.0, 3.4) for VPTD, and 1.1% (95% CI: 0.2, 2.0) for term LBW for each 5 km closer to any power plant. When stratifying by different fuel type, we found that only solid waste had an association with term LBW, whereas oil, gas, and solid waste all had an association with PTD and VPTD. Results were consistent when exposure was categorized by number of power plants. Our study found evidence of increasing odds of adverse birth outcomes among infants born to pregnant women living closer to power plants. More research is warranted to better understand the causal relationship.

The effects of ambient temperature on outpatient visits for varicella and herpes zoster in Shanghai, China: a time-series study.

BACKGROUND: The seasonality of varicella and herpes zoster has been widely observed, but there is limited evidence on their associations with ambient temperature. OBJECTIVE: The associations between ambient temperature and outpatient visits for varicella and herpes zoster were examined. METHODS: We collected daily outpatient visit data for varicella (N = 3520) and herpes zoster (N = 6614) from a major hospital in Shanghai, China, from 2008 to 2010. We adopted the generalized additive model in time-series analysis to investigate the short-term associations between temperature and outpatient visits for varicella and herpes zoster after controlling for seasonal trends, day of the week, and humidity. RESULTS: A 1°C increase in daily mean temperature was associated with a 1.33% (95% confidence interval 0.93%-1.74%) decrease in outpatient visits for varicella whereas it was associated with a 2.18% (95% confidence interval 1.90%-2.46%) increase in outpatient visits for herpes zoster. LIMITATIONS: Only 1 hospital was included and we did not control for individual-level risk factors. CONCLUSION: Our results demonstrated that temperature variation might be an important risk factor for varicella and herpes zoster in China.

Does ambient CO have protective effect for COPD patient?

BACKGROUND: Existing studies found paradoxical effects of carbon monoxide (CO) on human health. Carbon monoxide (CO), at high concentrations, is a well-known toxicant, but recent studies suggest that CO at low concentrations may have protective health effects under certain conditions. OBJECTIVES: To investigate the acute effect of ambient CO on hospital admission for chronic obstructive pulmonary disease (COPD) in Shanghai, China. METHODS: Daily data on COPD admissions and CO concentrations between 2006 and 2008 were collected. We applied over-dispersed generalized additive Poisson models, adjusted for weather conditions, day of the week and public holidays, long-term and seasonal trends. RESULTS: During the study period, the average CO concentration was 1.3mg/m(3), well below the international health-based standard. Negative associations were found between ambient CO concentration and daily COPD hospitalization. An interquartile range increase (0.6 mg/m(3)) in CO concentration at lag 3 day corresponded to -2.97% (95% confidence interval: -4.63%, -1.31%) change in COPD hospitalization. The negative associations were robust after adjustment for co-pollutants (PM10, NO2 and SO2). The protective effect of CO appeared to be more evident in the cool season. CONCLUSION: Short-term exposure to CO at low ambient concentration may be associated with reduced risk of COPD hospitalization. Our results may contribute to a comprehensive understanding on the health effects of ambient CO.

Particulate air pollution and circulating biomarkers among type 2 diabetic mellitus patients: the roles of particle size and time windows of exposure.

BACKGROUND: Short-term associations between size-fractionated particulate matter (PM) air pollution and circulating biomarkers are not well established, especially among diabetes patients. METHODS: We conducted a longitudinal panel study involving 6 repeated measurements of 12 circulating biomarkers among 35 diabetes patients from April to June, 2013 in Shanghai, China. Real-time number and mass concentrations of PM with multiple size fractions between 0.25 and 10 µm were measured. Linear mixed-effect models were used to explore the associations between size-fractionated PM concentrations and blood biomarkers at different time windows. RESULTS: Short-term exposure to PM was significantly associated with elevated levels of 5 biomarkers of inflammation, 3 biomarkers of coagulation and 1 vasoconstrictor. The effects varied considerably by particle size and time windows. Overall, PM with smaller size had stronger associations, and the most significant size fractions were 0.25-0.40 µm. Even 2 h exposure to PM can lead to a significant increase in biomarkers. The effects on biomarkers of inflammation and vasoconstriction were restricted to the first 12h after exposure, but the effects on coagulation persisted for 24-72 h. For example, an interquartile range increase in 2h average exposure to PM(0.25-0.40) was associated with 6-20% increase in biomarkers of inflammation, 19-38% in coagulation and 17% in vasoconstriction. PM had a stronger effect among male patients than female patients. CONCLUSIONS: Our results provided important evidence on the roles of the size and time windows of exposure in the PM-mediated effects on circulating biomarkers of inflammation, coagulation and vasoconstriction in diabetes patients in China.

The effects of air pollution on adverse birth outcomes.

BACKGROUND: Air pollution has been shown to have adverse effects on many health outcomes including cardiorespiratory diseases and cancer. However, evidence on the effects of prenatal exposure is still limited. The purpose of this retrospective cohort study is to evaluate the effects of prenatal exposure to air pollutants including particulate matter with aerodynamic diameter less than 2.5 µm (PM2.5) and ozone (O3) on the risk of adverse birth outcomes (ABOs) including term low birth weight (LBW), preterm delivery (PTD) and very PTD (VPTD). METHODS: singleton births from 2004 to 2005 in Florida were included in the study (N=423,719). Trimester-specific exposures to O3 and PM2.5 at maternal residence at delivery were estimated using the National Environmental Public Health Tracking Network data, which were interpolated using Hierarchical Bayesian models. RESULTS: After adjustment for potential confounders such as demographics, medical and lifestyle factors PM2.5 exposures in all trimesters were found to be significantly and positively associated with the risk of all ABOs. Second-trimester exposure had the strongest effects. For an interquartile range (IQR) increase in PM2.5 during the second trimester, the risk of term LBW, PTD and VPTD increased by 3% [95% confidence interval (CI): 1-6%)], 12% (11-14%) and 22% (18-25%), respectively. O3 was also found to be positively associated with PTD and VPTD with the strongest effects over the whole pregnancy period [3% (1-5%) for PTD and 13% (7-19%) for VPTD for each IQR increase]. However, O3 was observed to have protective effects on term LBW. Results were consistent for multi-pollutant models. CONCLUSION: PM2.5 has consistent adverse effects on ABOs whereas O3 has inconsistent effects. These findings warrant further investigation.