Air pollution and population health: a global challenge

“Air pollution and population health” is one of the most important environmental and public health issues. Economic development, urbanization, energy consumption, transportation/motorization, and rapid population growth are major driving forces of air pollution in large cities, especially in megacities. Air pollution levels in developed countries have been decreasing dramatically in recent decades. However, in developing countries and in countries in transition, air pollution levels are still at relatively high levels, though the levels have been gradually decreasing or have remained stable during rapid economic development. In recent years, several hundred epidemiological studies have emerged showing adverse health effects associated with short-term and long-term exposure to air pollutants. Time-series studies conducted in Asian cities also showed similar health effects on mortality associated with exposure to particulate matter (PM), sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and ozone (O₃) to those explored in Europe and North America. The World Health Organization (WHO) published the “WHO Air Quality Guidelines (AQGs), Global Update” in 2006. These updated AQGs provide much stricter guidelines for PM, NO₂, SO₂ and O₃. Considering that current air pollution levels are much higher than the WHO-recommended AQGs, interim targets for these four air pollutants are also recommended for member states, especially for developing countries in setting their country-specific air quality standards. In conclusion, ambient air pollution is a health hazard. It is more important in Asian developing countries within the context of pollution level and population density. Improving air quality has substantial, measurable and important public health benefits.     

中国空气污染与不良出生结局的研究进展

目的 对中国空气污染与不良出生结局的相关研究进展进行综述。方法 通过检索万方、中国知网（CNKI）、PubMed、Science Direct、Web of Science等数据库2016年6月30日前发表的中国人群空气污染物暴露与不良出生结局相关文献,按照制定的纳入排除标准进行筛选,并对纳入的27篇文献进行综述。结果 中国孕产妇妊娠期间空气动力学直径≤10 μm的颗粒物（PM₁₀）、二氧化硫（SO₂）、二氧化氮（NO₂）、总悬浮颗粒物（TSP）暴露可能增加低出生体重发病风险;妊娠期间暴露PM₁₀、SO₂、NO₂可能增加早产发病风险;妊娠期间暴露SO₂、NO₂、臭氧（O₃）、PM₁₀可能增加先天性心脏缺陷及其他出生缺陷发病风险。结论 中国孕产妇妊娠期间空气污染物暴露可能增加不良出生结局发病风险,需进一步开展研究探讨其相关性。     

Short-term association between exposure to ozone and mortality in Oporto, Portugal

Exposures to air pollution in developed countries have generally decreased over the last two decades. However, many recent epidemiological studies have consistently shown positive associations between low-level exposure to air pollutants and health outcomes. In Portugal, very few studies have analysed the acute effect of air pollutants on health.The present study evaluates the association between exposure to air pollution and daily mortality in the Oporto Metropolitan Area, Portugal. Generalised additive models were used for this analysis. Pollutants assessed were ozone, nitrogen dioxide, and particulate matter (PM₁₀). Models were adjusted for time trend, seasonality, and weather.We report that an increase of 10 μg/m³ in the daily ozone 8-h maximum moving-average corresponds to an increase of 0.95% (95%CI: 0.30, 1.60) and 1.58% (95%CI: 0.45, 2.73) in non-accidental mortality and cardiovascular mortality, respectively, in the summer season. A significant effect of 0.67% (95% CI: 0.03:1.32) was also found for the association between PM₁₀ and non-accidental mortality in the summer season. Associations with ozone and PM₁₀ exposures were higher in the elderly people. No significant effects on mortality were observed during the summer season with nitrogen dioxide exposures.Our analyses provide the first significant evidence in Oporto that exposures to O₃ and PM₁₀ have adverse effects on the health of the general population in the summer months.     

Air pollutants and their monitoring]

Some basic concepts regarding air pollution are set out. Although, from a health care standpoint, our interest revolves around the impact which pollution has on human health, it being important to ascertain the main pollutants, the sources of emissions, the physiochemical properties thereof, the sampling and analysis methods which are used at the air pollution control stations, the limits set by the laws currently in impact and the World Health Organization recommendations with regard to the levels of immission. This study reviews these concepts with regard to the pollutants which have been analyzed in the Spanish Multicenter Study of Air Pollution and Mortality (EMECAM): particles, sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3). For this purpose, the most recent publications on this subject have been used, including part of what is going to be the line around which all of the measures aimed at combating air pollution are going to be revolving in the very near future, that is, the new set of European Union Directives (some currently in the proposal stage) and the latest recommendations (not as yet published) of the World Health Organization. Lastly, a wide range of aspects are set out which involve Public Health in the field of air pollution, despite the monitoring and control thereof falling to the environmental affairs authorities in terms of government organization.     

Health effects of ambient air pollution – recent research development and contemporary methodological challenges

Exposure to high levels of air pollution can cause a variety of adverse health outcomes. Air quality in developed countries has been generally improved over the last three decades. However, many recent epidemiological studies have consistently shown positive associations between low-level exposure to air pollution and health outcomes. Thus, adverse health effects of air pollution, even at relatively low levels, remain a public concern. This paper aims to provide an overview of recent research development and contemporary methodological challenges in this field and to identify future research directions for air pollution epidemiological studies.     

Air Pollution and Mortality in Elderly People: A Time-Series Study in Sao Paulo,Brazil

The relationship between daily mortality of elderly (65 + y) persons and air pollution in the metropolitan area of Sao Paulo, Brazil, for the period May 1990 to April 1991 was evaluated by time series regression, controlling for season, weather, and other factors. Mortality was associated with respirable particles (PM₁₀), nitrogen oxides (NO_x), sulfur dioxide (SO₂), and carbon monoxide (CO). The association with PM₁₀ was most statistically significant, robust, and independent of other air pollutants. An increase in PM₁₀ equal to 100 μg/m³ was associated with an increase in overall mortality equal to approximately 13%. This association was consistent across various model specifications and estimation techniques. The dose-response relationship between mortality and respirable particulate pollution was almost linear, with no evidence of a “safe” threshold level. The results were similar to those observed in London and several U.S. cities. The results were also supportive of recent animal studies that have observed adverse health outcomes in experimental animals exposed to air pollution in Sao Paulo.     

A spatially disaggregated time-series analysis of the short-term effects of particulate matter exposure on mortality in Chennai, India

The global burden of disease due to air pollution is concentrated in the rapidly developing counties of Asia, but a recent meta-analysis found that relatively few studies on short-term exposure to air pollution and mortality have been performed in these countries, including India. Local evidence on the effects of short-term exposures to air pollutants on mortality and cardio-respiratory morbidity in Asia would reduce the uncertainties in current impact estimations and facilitate effective public policy responses to a deteriorating air pollution situation in South Asia. Here, we report the results from one of the first of such studies in metropolitan Chennai, India, conducted as part of a co-ordinated multi-city time-series initiative in India aimed at estimating the effect of short-term exposure to particulate matter ≤10 μm in aerodynamic diameter (PM₁₀) on all-cause mortality. The studies in Indian cities (Chennai, Delhi and Ludhiana) were part of a larger multi-city effort in Asia, co-ordinated by The Health Effects Institute (Boston, MA, USA) under their program for Public health and Air Pollution in Asia (PAPA). An important study output included the development of methodological refinements to overcome the limitations of routinely collected data in terms of missing measurements, small footprints of air pollution monitors and incomplete address information on death records. We used data on ambient air quality and all-cause mortality collected over the period 2002–2004. Exposures and health outcomes were disaggregated at the level of individual city zones and subsequently used in quasi-Poisson generalized additive models with smooth functions of time, temperature and relative humidity. Our model estimated a 0.44% (95% confidence interval?0.17–0.71) increase in mortality per 10 μg/m³ increase in daily average concentrations of PM₁₀, which is comparable to estimates from other PAPA cities and previous studies in North America and Europe. The results from PAPA studies in India, while preliminary, serve to strengthen the local evidence base for air pollution-related health effects that is imminently needed for better air quality management, while adding valuable information from India to the global repository of evidence.     

Public Health and Air Pollution in Asia (PAPA): a multicity study of short-term effects of air pollution on mortality

Background and objectives

Although the deleterious effects of air pollution from fossil fuel combustion have been demonstrated in many Western nations, fewer studies have been conducted in Asia. The Public Health and Air Pollution in Asia (PAPA) project assessed the effects of short-term exposure to air pollution on daily mortality in Bangkok, Thailand, and in three cities in China: Hong Kong, Shanghai, and Wuhan.

Methods

Poisson regression models incorporating natural spline smoothing functions were used to adjust for seasonality and other time-varying covariates that might confound the association between air pollution and mortality. Effect estimates were determined for each city and then for the cities combined using a random effects method.

Results

In individual cities, associations were detected between most of the pollutants [nitrogen dioxide, sulfur dioxide, particulate matter ≤ 10 μm in aerodynamic diameter (PM₁₀), and ozone] and most health outcomes under study (i.e., all natural-cause, cardiovascular, and respiratory mortality). The city-combined effects of the four pollutants tended to be equal or greater than those identified in studies conducted in Western industrial nations. In addition, residents of Asian cities are likely to have higher exposures to air pollution than those in Western industrial nations because they spend more time outdoors and less time in air conditioning.

Conclusions

Although the social and environmental conditions may be quite different, it is reasonable to apply estimates derived from previous health effect of air pollution studies in the West to Asia.     

Prenatal ambient air pollution exposure and small for gestational age birth in the Puget Sound Air Basin

Several studies have identified high concentrations of air pollution as harmful to the developing fetus, but few studies of traffic-derived air pollution and birth outcomes have been conducted in areas of low to moderate air pollution. We identified singleton live births between 1997 and 2005 (N?=?367,046 births) in the Puget Sound Air Basin of Washington State. We estimated nitrogen dioxide (NO₂) exposure using a land use regression model of traffic, PM_2.5 exposure from the nearest community monitor, and proximity to highways/roadways for the residential location of all subjects. Logistic regression estimates of odds ratios (OR) of small for gestational age (SGA) and low birth weight (<2,500 g) among term births were calculated. We observed a modest association between SGA births with increasing quartile of first trimester NO₂ exposure: second (OR?=?1.01, 95 % confidence interval (CI) 0.97, 1.04), third (OR?=?1.06, 95 % CI 1.03, 1.10), and fourth (OR?=?1.08, 95 % CI 1.04, 1.12) (p trend <0.001). We did not observe an association between PM_2.5 and SGA or low birth weight among term births. Our findings suggest that prenatal exposure to traffic-derived air pollutants has a modest effect on fetal growth in a region with low overall air pollutant concentrations. Given the modest associations, future studies in similar settings that maximize the opportunity to address potential residual confounding are needed.     

Perinatal Air Pollutant Exposures and Autism Spectrum Disorder in the Children of Nurses’ Health Study II Participants

Objective: Air pollution contains many toxicants known to affect neurological function and to have effects on the fetus in utero. Recent studies have reported associations between perinatal exposure to air pollutants and autism spectrum disorder (ASD) in children. We tested the hypothesis that perinatal exposure to air pollutants is associated with ASD, focusing on pollutants associated with ASD in prior studies.Methods: We estimated associations between U.S. Environmental Protection Agency–modeled levels of hazardous air pollutants at the time and place of birth and ASD in the children of participants in the Nurses’ Health Study II (325 cases, 22,101 controls). Our analyses focused on pollutants associated with ASD in prior research. We accounted for possible confounding and ascertainment bias by adjusting for family-level socioeconomic status (maternal grandparents’ education) and census tract–level socioeconomic measures (e.g., tract median income and percent college educated), as well as maternal age at birth and year of birth. We also examined possible differences in the relationship between ASD and pollutant exposures by child’s sex.Results: Perinatal exposures to the highest versus lowest quintile of diesel, lead, manganese, mercury, methylene chloride, and an overall measure of metals were significantly associated with ASD, with odds ratios ranging from 1.5 (for overall metals measure) to 2.0 (for diesel and mercury). In addition, linear trends were positive and statistically significant for these exposures (p < .05 for each). For most pollutants, associations were stronger for boys (279 cases) than for girls (46 cases) and significantly different according to sex.Conclusions: Perinatal exposure to air pollutants may increase risk for ASD. Additionally, future studies should consider sex-specific biological pathways connecting perinatal exposure to pollutants with ASD.     

妊娠妇女空气污染暴露相关生物学标记研究进展

空气污染可以导致呼吸道疾病以及心脑血管疾病。妊娠妇女机体处于一种高代谢状态,对空气污染物比较敏感;胎儿处于生长发育的关键时期,对污染物也更敏感。近年来的研究表明,妊娠妇女暴露于空气污染物与各种不良妊娠结局有关,包括自然流产、胎儿生长受限、早产和低出生体质量等。然而,其潜在机制尚不清楚。目前暴露组学、代谢组学的应用筛选出许多空气污染体内暴露的生物学标记物,如DNA加合物等代谢产物。生物学标记物可以用来反映个体的内暴露水平,相比外暴露的污染物监测更为准确,更能反映机体的暴露水平,从而指导探究空气污染暴露与各种妊娠结局相关的潜在机制。     

Air pollution and health: bridging the gap from sources to health outcomes: conference summary

??Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes,?? an international specialty conference sponsored by the American Association for Aerosol Research, was held to address key uncertainties in our understanding of adverse health effects related to air pollution and to integrate and disseminate results from recent scientific studies that cut across a range of air pollution-related disciplines. The Conference addressed the science of air pollution and health within a multipollutant framework (herein ??multipollutant?? refers to gases and particulate matter mass, components, and physical properties), focusing on five key science areas: sources, atmospheric sciences, exposure, dose, and health effects. Eight key policy-relevant science questions integrated across various parts of the five science areas and a ninth question regarding findings that provide policy-relevant insights served as the framework for the meeting. Results synthesized from this Conference provide new evidence, reaffirm past findings, and offer guidance for future research efforts that will continue to incrementally advance the science required for reducing uncertainties in linking sources, air pollutants, human exposure, and health effects. This paper summarizes the Conference findings organized around the science questions. A number of key points emerged from the Conference findings. First, there is a need for greater focus on multipollutant science and management approaches that include more direct studies of the mixture of pollutants from sources with an emphasis on health studies at ambient concentrations. Further, a number of research groups reaffirmed a need for better understanding of biological mechanisms and apparent associations of various health effects with components of particulate matter (PM), such as elemental carbon, certain organic species, ultrafine particles, and certain trace elements such as Ni, V, and Fe(II), as well as some gaseous pollutants. Although much debate continues in this area, generation of reactive oxygen species induced by these and other species present in air pollution and the resulting oxidative stress and inflammation were reiterated as key pathways leading to respiratory and cardiovascular outcomes. The Conference also underscored significant advances in understanding the susceptibility of populations, including the role of genetics and epigenetics and the influence of socioeconomic and other confounding factors and their synergistic interactions with air pollutants. Participants also pointed out that short- and long-term intervention episodes that reduce pollution from sources and improve air quality continue to indicate that when pollution decreases so do reported adverse health effects. In the limited number of cases where specific sources or PM_2.5 species were included in investigations, specific species are often associated with the decrease in effects. Other recent advances for improved exposure estimates for epidemiological studies included using new technologies such as microsensors combined with cell phone and integrated into real-time communications, hybrid air quality modeling such as combined receptor- and emission-based models, and surface observations used with remote sensing such as satellite data.     

Ambient air pollution and congenital heart disease: a register-based study

Maternal exposure to ambient air pollution has increasingly been linked to adverse pregnancy outcomes. The evidence linking this exposure to congenital anomalies is still limited and controversial. This case–control study investigated the association between maternal exposure to ambient particulate matter with aerodynamic diameter less than 10 μm (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide, nitric oxide (NO), ozone (O₃), and carbon monoxide (CO) and the occurrence of congenital heart disease in the population of Northeast England (1993–2003). Each case and control was assigned weekly average (weeks 3–8 of pregnancy) of pollutant levels measured by the closest monitor to the mother’s residential postcode. Using exposure as both continuous and categorical variables, logistic regression models were constructed to quantify the adjusted odds ratios of exposure to air pollutants and the occurrence of each outcome group. We found exposure to CO and NO to be associated with ventricular septal defect and cardiac septa malformations. CO was also associated with congenital pulmonary valve stenosis and NO with pooled cases of congenital heart disease and tetralogy of Fallot. Findings for SO₂, O₃ and PM₁₀ were less consistent.     

GSTM1, GSTT1, and GSTP1 Polymorphisms and Associations between Air Pollutants and Markers of Insulin Resistance in Elderly Koreans

Background: Previous studies have suggested that diabetes mellitus (DM) is an outcome of exposure to air pollution, and metabolic detoxification genes affect air pollution–related outcomes.Objectives: We evaluated associations between air pollutants and markers of insulin resistance (IR), an underlying mechanism of type 2 DM, and effect modification by GSTM1, GSTT1, and GSTP1 genotypes among elderly participants in the Korean Elderly Environmental Panel (KEEP) study.Methods: We recruited 560 people ≥ 60 years of age and obtained blood samples from them up to three times between 2008 and 2010. For air pollution exposure, we used ambient air pollutant [i.e., particulate matter ≤ 10 µm in diameter (PM₁₀), sulfur dioxide (SO₂), ozone (O₃), and nitrogen dioxide (NO₂)] monitoring data. We measured levels of fasting glucose and insulin and derived the homeostatic model assessment (HOMA) index to assess IR. Mixed-effect models were used to estimate associations between air pollutants and IR indices on the same day or lagged up to 10 days prior, and effect modification by GSTM1, GSTT1, and GSTP1 genotypes.Results: Interquartile range increases in PM₁₀, O₃, and NO₂ were significantly associated with IR indices, depending on the lag period. Associations were stronger among participants with a history of DM and among those with GSTM1-null, GSTT1-null, and GSTP1 AG or GG genotypes.Conclusions: Our results suggest that PM₁₀, O₃, and NO₂ may increase IR in the elderly, and that GSTM1-null, GSTT1-null, and GSTP1 AG or GG genotypes may increase susceptibility to potential effects of ambient air pollutants on IR.     

Meeting report: atmospheric pollution and human reproduction

BACKGROUND: There is a growing body of epidemiologic literature reporting associations between atmospheric pollutants and reproductive outcomes, particularly birth weight and gestational duration. OBJECTIVES: The objectives of our international workshop were to discuss the current evidence, to identify the strengths and weaknesses of published epidemiologic studies, and to suggest future directions for research. DISCUSSION: Participants identified promising exposure assessment tools, including exposure models with fine spatial and temporal resolution that take into account time-activity patterns. More knowledge on factors correlated with exposure to air pollution, such as other environmental pollutants with similar temporal variations, and assessment of nutritional factors possibly influencing birth outcomes would help evaluate importance of residual confounding. Participants proposed a list of points to report in future publications on this topic to facilitate research syntheses. Nested case-control studies analyzed using two-phase statistical techniques and development of cohorts with extensive information on pregnancy behaviors and biological samples are promising study designs. Issues related to the identification of critical exposure windows and potential biological mechanisms through which air pollutants may lead to intrauterine growth restriction and premature birth were reviewed. CONCLUSIONS: To make progress, this research field needs input from toxicology, exposure assessment, and clinical research, especially to aid in the identification and exposure assessment of feto-toxic agents in ambient air, in the development of early markers of adverse reproductive outcomes, and of relevant biological pathways. In particular, additional research using animal models would help better delineate the biological mechanisms underpinning the associations reported in human studies.     

Traffic related air pollution and acute hospital admission for respiratory diseases in Drammen, Norway 1995–2000

The aim of this study was to estimate the associations between seven ambient air pollutants [particulate matter (PM₁₀), nitrous dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), benzene, formaldehyde and toluene] and acute hospital admissions for respiratory diseases in Drammen, Norway 1995–2000. Time-series analysis of counts was performed by means of generalized additive models with log link and Poisson distribution. The results showed that benzene was the pollutant having the strongest association with respiratory diseases for the total study period, the relative risk of an interquartile increase of benzene was 1.095 with 95% confidence interval: 1.031–1.163. The corresponding results were 1.049 (0.990–1.112) for formaldehyde, 1.044 (1.000–1.090) for toluene, 1.064 (1.019–1.111) for NO₂, 1.043 (1.011–1.075) for SO₂, 0.990 (0.936–1.049) for O₃ and 1.022 (0.990–1.055) for PM₁₀. Dividing the total study period into two 3-year periods, there was a substantial reduction in the exposure levels of the volatile organic compounds (benzene, formaldehyde and toluene) from the first to the second period. Separate analyses for the second time period showed weaker association between these pollutants and the health outcome. This study provides further evidence for short-term respiratory health effects of traffic related air pollution.     

Traffic-related air toxics and term low birth weight in Los Angeles County, California

Background: Numerous studies have linked criteria air pollutants with adverse birth outcomes, but there is less information on the importance of specific emission sources, such as traffic, and air toxics.Objectives: We used three exposure data sources to examine odds of term low birth weight (LBW) in Los Angeles, California, women when exposed to high levels of traffic-related air pollutants during pregnancy.Methods: We identified term births during 1 June 2004 to 30 March 2006 to women residing within 5 miles of a South Coast Air Quality Management District (SCAQMD) Multiple Air Toxics Exposure Study (MATES III) monitoring station. Pregnancy period average exposures were estimated for air toxics, including polycyclic aromatic hydrocarbons (PAHs), source-specific particulate matter < 2.5 μm in aerodynamic diameter (PM_2.5) based on a chemical mass balance model, criteria air pollutants from government monitoring data, and land use regression (LUR) model estimates of nitric oxide (NO), nitrogen dioxide (NO₂) and nitrogen oxides (NO_x). Associations between these metrics and odds of term LBW (< 2,500 g) were examined using logistic regression.Results: Odds of term LBW increased approximately 5% per interquartile range increase in entire pregnancy exposures to several correlated traffic pollutants: LUR measures of NO, NO₂, and NO_x, elemental carbon, and PM_2.5 from diesel and gasoline combustion and paved road dust (geological PM_2.5).Conclusions: These analyses provide additional evidence of the potential impact of traffic-related air pollution on fetal growth. Particles from traffic sources should be a focus of future studies.     

Current approaches used in epidemiologic studies to examine short-term multipollutant air pollution exposures

PurposeAir pollution epidemiology traditionally focuses on the relationship between individual air pollutants and health outcomes (e.g., mortality). To account for potential copollutant confounding, individual pollutant associations are often estimated by adjusting or controlling for other pollutants in the mixture. Recently, the need to characterize the relationship between health outcomes and the larger multipollutant mixture has been emphasized in an attempt to better protect public health and inform more sustainable air quality management decisions.MethodsNew and innovative statistical methods to examine multipollutant exposures were identified through a broad literature search, with a specific focus on those statistical approaches currently used in epidemiologic studies of short-term exposures to criteria air pollutants (i.e., particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and ozone).ResultsFive broad classes of statistical approaches were identified for examining associations between short-term multipollutant exposures and health outcomes, specifically additive main effects, effect measure modification, unsupervised dimension reduction, supervised dimension reduction, and nonparametric methods. These approaches are characterized including advantages and limitations in different epidemiologic scenarios.DiscussionBy highlighting the characteristics of various studies in which multipollutant statistical methods have been used, this review provides epidemiologists and biostatisticians with a resource to aid in the selection of the most optimal statistical method to use when examining multipollutant exposures.     

Opportunities for using spatial property assessment data in air pollution exposure assessments

Background  

Many epidemiological studies examining the relationships between adverse health outcomes and exposure to air pollutants use ambient air pollution measurements as a proxy for personal exposure levels. When pollution levels vary at neighbourhood levels, using ambient pollution data from sparsely located fixed monitors may inadequately capture the spatial variation in ambient pollution. A major constraint to moving toward exposure assessments and epidemiological studies of air pollution at a neighbourhood level is the lack of readily available data at appropriate spatial resolutions. Spatial property assessment data are widely available in North America and may provide an opportunity for developing neighbourhood level air pollution exposure assessments.