Sources of uncertainty in calculating mortality and morbidity attributable to air pollution

Particulate matter pollutants and risk of type 2 diabetes: a time for concern?

The World Health Organization estimates that worldwide in 2012 around 7 million deaths occurred prematurely due to air pollution, which is now the world's largest single environmental health risk. The higher premature mortality associated with air pollution is due to exposure to small particulate matter of 10 microns (PM10) or less in diameter. Exposure to air pollution has also been suggested as a contributing to diabetes incidence and progression. There are a number of possible biological pathways linking air pollutants to diabetes, including endothelial dysfunction, dysregulation of the visceral adipose tissue through inflammation, hepatic insulin resistance, elevated hemoglobin A1c level, elevated blood pressure, and alterations in autonomic tone, which may increase insulin resistance. The risk of future diabetes associated with exposure to 10 μg/m(3) increase of PM2.5 has been quantified in the range of 10 to 27%; the risk of diabetes mortality associated with PM2.5 appears to be quite lower, around 1% for each increment exposure of 10 μg/m(3) of both PM2.5 and PM10. Limitations of the current epidemiological evidence include the complex mixture of pollutants, the different design of the studies, the limited data available for non Western populations, and the lack of demonstration that improvement of air quality is associated with a decrease incidence of type 2 diabetes. Although the most sources of outdoor air pollution are well beyond the control of individuals, people should be informed that there are means to reduce the burden of air pollutants on diabetes risk, including avoidance of passive smoking, adoption of an healthy diet, and increasing leisure-time physical activity.

Systematic review and metaanalysis of air pollution exposure and risk of diabetes

The present systematic review and metaanalysis of published observational studies was conducted to assess the health effects of exposure to air pollution on diabetes risk. Online databases were searched through January 2013, and the reference lists of pertinent articles reporting observational studies in humans were examined. Pooled relative risks and 95 % confidence intervals were calculated with a random-effects model. Exposure to air pollution was associated with slight increase in risk of diabetes and susceptibility of people with diabetes to air pollution. These results were consistent between time-series, case-crossover and cohort studies and between studies conducted in North America and Europe. The association between exposure to air pollution and diabetes was stronger for gaseous pollutants than for particulate matter. Our metaanalysis suggests that exposure to air pollution may be a risk factor for diabetes and increase susceptibility of people with diabetes to air pollution.

Air-Pollution and Cardiometabolic Diseases (AIRCMD): a prospective study investigating the impact of air pollution exposure and propensity for type II diabetes

There is a paucity of prospective cohort studies investigating the impact of environmental factors on the development of cardiometabolic (CM) disorders like type II diabetes (T2DM). The objective of the Air-Pollution and Cardiometabolic Diseases (AIRCMD) study is to investigate the impact of personal level air pollution measures [personal black carbon (BC)/sulfate measures] and ambient fine particulate matter [(PM2.5)/NO2] levels on propensity to type II diabetes in Beijing, China. Subjects with metabolic syndrome will undergo four repeated study visits within each season over a one year period following an initial screening visit. At each study visit, subjects will be monitored for sub-acute exposure to personal and ambient measures of air-pollution exposure and will undergo a series of functional CM outcomes. The primary endpoints include independent associations between integrated 5-day mean exposure to PM2.5 and BC and homeostasis model assessment of insulin resistance (HOMA-IR) measures, 24-hour mean diastolic and mean arterial pressure and endothelial-dependent vasodilatation. The secondary endpoints will explore the mechanistic explanation for a causal relationship between exposures and propensity for type II diabetes and will include additional functional outcomes such as arterial compliance, heart rate variability and plasma adipokines. The novel aspects of the study include the launch of infrastructure for future translational investigations in highly polluted urbanized environments and the creation of novel methodologies for linking personalized exposure measurements with functional CM outcomes. We believe that AIRCMD will allow for unprecedented new investigations into the association between environmental risk factors and CM disorders.

An assessment of air pollution and its attributable mortality in Ulaanbaatar, Mongolia

Epidemiologic studies have consistently reported associations between outdoor fine particulate matter (PM_2.5) air pollution and adverse health effects. Although Asia bears the majority of the public health burden from air pollution, few epidemiologic studies have been conducted outside of North America and Europe due in part to challenges in population exposure assessment. We assessed the feasibility of two current exposure assessment techniques, land use regression (LUR) modeling and mobile monitoring, and estimated the mortality attributable to air pollution in Ulaanbaatar, Mongolia. We developed LUR models for predicting wintertime spatial patterns of NO₂ and SO₂ based on 2-week passive Ogawa measurements at 37 locations and freely available geographic predictors. The models explained 74% and 78% of the variance in NO₂ and SO₂, respectively. Land cover characteristics derived from satellite images were useful predictors of both pollutants. Mobile PM_2.5 monitoring with an integrating nephelometer also showed promise, capturing substantial spatial variation in PM_2.5 concentrations. The spatial patterns in SO₂ and PM, seasonal and diurnal patterns in PM_2.5, and high wintertime PM_2.5/PM₁₀ ratios were consistent with a major impact from coal and wood combustion in the city's low-income traditional housing (ger) areas. The annual average concentration of PM_2.5 measured at a centrally located government monitoring site was 75 μg/m³ or more than seven times the World Health Organization's PM_2.5 air quality guideline, driven by a wintertime average concentration of 148 μg/m³. PM_2.5 concentrations measured in a traditional housing area were higher, with a wintertime mean PM_2.5 concentration of 250 μg/m³. We conservatively estimated that 29% (95% CI, 12-43%) of cardiopulmonary deaths and 40% (95% CI, 17-56%) of lung cancer deaths in the city are attributable to outdoor air pollution. These deaths correspond to nearly 10% of the city's total mortality, with estimates ranging to more than 13% of mortality under less conservative model assumptions. LUR models and mobile monitoring can be successfully implemented in developing country cities, thus cost-effectively improving exposure assessment for epidemiology and risk assessment. Air pollution represents a major threat to public health in Ulaanbaatar, Mongolia, and reducing home heating emissions in traditional housing areas should be the primary focus of air pollution control efforts.

Health benefits of improving air quality in the rapidly aging Korean society

Korea is experiencing an extraordinarily rapid demographic transition. We investigated the short-term association between air pollution and mortality and assessed the impact of improved air quality on mortality in a rapidly aging city, Seoul, Korea. The generalized additive model (GAM) was used to estimate the relative risks (RR) of mortality associated with changes in air pollution. The time trends, seasonal variations, day of the week effects, and weather effects were controlled in the models. To estimate the health benefits, we used the US Environmental Protection Agency's BenMAP. For people 0-64 years of age, elderly people (65+ years), and all age groups, an increase of 10 microg/m(3) in PM(10) was associated with increases in daily death counts of 0.27% (95% CI: 0.04-0.50), 0.45% (95% CI: 0.27-0.64), and 0.37% (95% CI: 0.23-0.52), respectively. For ages 0-64 years, elderly people, and all age groups, a 10 ppb increase in 1-hour maximum ozone concentration resulted in an increased risk of daily death counts of 0.28% (95% CI: -0.19-0.74), 0.96% (95% CI: 0.46-1.47), and 0.81% (95% CI: 0.35-1.26), respectively. For elderly people, it was estimated that the health benefits of attaining the World Health Organization's (WHO) air quality guidelines (AQGs) for PM(10) (24-hour average 50 microg/m(3)) would suggest an annual reduction of 964 (95% CI: 564-1366) premature deaths, and 329 (95% CI: 159-500) premature deaths could be prevented annually in 2015 from attaining the WHO's guidelines for ozone (8-hour average 100 microg/m(3)). The rapid increase of the elderly population has major consequences and implications for society and public health. This study showed that elderly people are at higher risk for the acute mortality effects of air pollution. Therefore, cleaner air will substantially contribute to improved public health in Seoul, given the growing concern about the adverse effects of air pollution for elderly people.