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Beijing’s pollution saviour: Mother Nature


Construction cranes are shrouded in smog in Beijing. Photo: Bloomberg

Residents say officials now rely on weather to control capital’s dire smog

What a difference a day makes. The arrival of strong winds overnight on Tuesday blew away much of the heavy smog that had choked Beijing for days, allowing the capital’s air quality to return to a healthy level within hours.

A cold front from the north reached the capital at about 11pm on Tuesday, and by midnight the concentration of PM2.5 particles, considered most dangerous to human health, had dropped to 22 – considered a healthy level – in the suburbs and 88 in the city. Residents woke up to a clear blue sky with cold, fresh air as the concentration of the fine particulates dropped to below 10 from more than 500 on Tuesday.

Internet users were quick to share pictures of the city’s clear skyline on social media while at the same time expressing in frustration that the capital was relying entirely on weather changes to fight the smog.

Officials, when questioned why the highest-level red pollution warning alert was not issued as the pollution index reached a hazardous level over the previous five days, explained that this was due to technological limitations.

Peng Yingdeng, a researcher at the National Engineering Research Centre for Urban Pollution Control, said air pollution had been dropping for three years, yet the weather – especially this year’s severe El Nino conditions – made the air quality worse. Beijing is prone to spells of low pressure that trap air pollutants closer to the ground.

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Some questioned why a red alert, the highest level in a four-tier system, was not issued to help residents cope better. A red alert would force schools to shut down, cars to stay off the road on alternate days and construction projects halted.

The city’s Environmental Protection Administration has been under fire for issuing and maintaining only the orange alert even though air quality was so bad that readings were off the charts.

Unfavourable weather, together with coal-burning in Beijing’s suburban area and vehicle exhaust emissions, were to blame for the heavy smog, authorities said. (CTA: note that goods vehicles can only enter Beijing and other big Mainland cities after midnight)

According to Beijing Severe Air Pollution Contingency Plan, a red alert can only be issued by the Beijing Emergency Management Office after being approved by the city mayor. It should be issued 24 hours in advance if air quality is forecast to be severe, with the air quality index over 300, for 72 hours.

But Peng said it was not possible to forecast air pollution precisely for a period longer than three days, and the Beijing environmental watchdog was upgrading its air quality projection system at a cost of 30 million yuan to extend forecasts to five days.

When air quality plummeted last Friday, the Beijing Municipal Environmental Monitoring Centre forecast it to improve on Saturday. But the AQI nosedived on Sunday and continued to drop on Monday and Tuesday, an environmental protection Administration official told The Beijing News.

“But technical limitation is no excuse,” Peng said. “The local environmental protection authority could have warned people of the severity of the smog.”

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People in Delhi are fashioning their own masks as hazardous smog chokes the Indian capital

The world’s most polluted major city has been blanketed in hazardous, choking smog as climate change talks started in Paris

There was a time when winter in the Indian capital was a glorious thing. Clear, sunny days and crisp cold nights.

No longer. Over the last decade air pollution has grown so rapidly that the cold weather turns the city into a grey, smog-filled health nightmare.

New Delhi has earned the dubious distinction of being the world’s most polluted major city, surpassing Beijing.

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While the Chinese capital has made progress in spreading awareness about air pollution and is taking steps to address it, New Delhi has barely begun to acknowledge the problem.

But as hacking coughs linger for months and red, watery eyes itch, a slow awareness is developing.

Some people tie handkerchiefs around their mouths and noses and others wear surgical masks.

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Sitesh Singh drives one of the city’s many auto rickshaws and suffers from asthma. He has started wearing a surgical mask through the winter and says it helps him breathe.

While surgical masks protect from larger pollution particles they do little to filter out smaller PM2.5, the most lethal particulate pollution that can become lodged deep inside the lungs.

While there is scant reliable data on respiratory illness in India, doctors say the number of cases is rising and the ones they see are more serious.

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Over the last week PM2.5 levels have soared above 300 micrograms per cubic meter on some days, 12 times the standard set by the World Health Organisation.

When air quality hits hazardous levels in China schools may be closed, industries shut down and government vehicles taken off the roads.

India has no such emergency protocols. Anti-pollution laws remain widely ignored and unenforced.

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Its fledgling air quality index covers only a few cities with a patchy network of monitors that often don’t work.

Globally, air pollution kills millions of people every year, including more than 627,000 in India, according to WHO.

India’s air pollution comes mostly from coal-fired power plants, crop burning, domestic cooking with firewood or cow dung, and vehicles burning diesel fuel.

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Beijing residents told to stay inside as smog levels soar

Air pollution in the Chinese capital has reached more than 15 times the safe level as smog engulfs large parts of the country

Chinese women wear masks as haze from smog caused by air pollution hangs over the Forbidden City in Beijing. Photograph: Kevin Frayer/Getty Images

Chinese women wear masks as haze from smog caused by air pollution hangs over the Forbidden City in Beijing. Photograph: Kevin Frayer/Getty Images

Beijing’s residents have been advised to stay indoors after air pollution in the Chinese capital reached hazardous levels.

The warning comes as the governments of more than 190 nations gather in Paris to discuss a possible new global agreement on climate change.

China, the biggest emitter of greenhouse gases in the world, is suffering from serious air pollution, largely attributed to smog from coal-fired power plants.

The onset of winter and the need for more heating of homes means the problem has intensified in the capital, which has an estimated population of 20 million.

At noon on Saturday, the US embassy in Beijing reported the level of the poisonous, tiny articles of PM2.5 at 391 micrograms per cubic metre.

The World Health Organisation considers the safe level to be 25 micrograms per cubic metre of the particulates.

Since Friday, the city had been shroud in grey smog, reducing visibilities to a few hundred metres.

The ministry of environmental protection has forecast severe pollution for the greater Beijing region, as well as the west part of Shandong and the northern part of Henan until Tuesday, when strong winds from the north are expected to blow away air pollutants.

The ministry has advised the public to stay indoors.

Residents of Beijing posted photographs of the pollution on Twitter.

Authorities blame coal burning for winter heating as a major culprit for the air pollution. The ministry said it had sent teams to check on illegal emissions by factories in several northern Chinese cities.

In the past, authorities have shut down factories and pulled half of the vehicles off the roads to curb pollution. But such drastic measures are disruptive and only used when Beijing feels it needs to present a better image to the world, such as hosting major global leaders and events.

Earlier this month, air pollution reached almost 50 times above the recommended levels in Shenyang, in the country’s north-east.

On 9 November, levels of PM2.5 reached 1,157 micrograms per cubic metre in the city, reducing visibility to as little as 100 metres.

Officials said the dangerous smog was caused by a surge in coal-fired electricity use, as the region’s central heating systems kick into gear for winter.

Smog soars in Chinese city to over 40 times safe limits as winter central heating turned on

Air quality reached extremely hazardous levels in the northeastern Chinese city of Shenyang as northern China began to burn coal to heat homes for winter.

Real-time data released by the Shenyang Environmental Protection Agency on Sunday showed the density of the poisonous tiny airborne matters known as PM2.5 was more than 1,000 micrograms per cubic metre. Nearby cities also reported very high levels of the harmful particulates.

The World Health Organisation considers the safe level of PM 2.5 to be 25 micrograms per cubic meter on a 24-hour average basis.

The readings from Shenyang are possibly the highest pollution levels ever recorded in China since the country began to monitor air quality and release real-time data in 2013.

The local authorities said the density of PM 2.5, considered extremely harmful to human health, peaked on Sunday afternoon at more than 1,200 micrograms per cubic metre.

The state-run Xinhua News Agency reported that the reading had reached as high as 1,400 micrograms per cubic meter at some monitoring sites.

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The local authorities issued the highest alert, warning residents to stay indoors and demanding that factories cut output to reduce pollution.

Photographs posted on social media showed grey skies and members of the public complained of sore throats.

Northern China typically burns coal to heat homes in the winter, a practice believed to have fouled the air.

Emissions from industrial plants and the increasing use of cars also are major causes of air pollution in China.

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Hong Kong’s air quality will suffer if bureaucrat once again heads environment department

Alexis Lau and Bill Barron

We refer to the report, “Appoint a professional to head Hong Kong’s environment department rather than a bureaucrat, say advisers” (September 19).

We strongly support calls for the new head of the Environmental Protection Department to be someone with professional expertise when the incumbent retires.

Environmental management requires trade-offs and compromises. Nonetheless, scientific evidence tends to be complex and involve uncertainties, while in the short term, political and economic costs may appear simple and compelling. Under such circumstances, as Melonie Chau Yuet-cheung of Friends of the Earth noted, “scientific evidence often takes a back seat”. This is more likely when the person making the final decisions lacks the required scientific background.

For example, the department is considering cutting back its chemical “speciation” network for PM2.5, arguably the pollutant contributing the greatest environmental health risks in Hong Kong. There are many sources of PM2.5, including marine shipping, power plants, vehicles, off-road diesel engines, commercial cooking and outflow from the mainland. We must compare chemical characteristics from different sites to determine the contributions of different sources to the measured PM2.5 concentrations. Cutting back this network will severely limit our ability to determine where the pollutants came from or design effective control strategies against them.

The science is well understood by professionals. One of the first steps the mainland took when it started to take air quality seriously in 2013 was to enhance its PM2.5 speciation capability. In Hong Kong, thanks to more forward-looking professionals in the department, it has been gathering such information for over a decade. This data was critical for the science behind the Clean Air Plan in 2013 and the subsequent HK$11.3 billion vehicle control programmes. It is incomprehensible that when governments elsewhere are trying to better understand the sources of PM2.5, the department is considering cutting that back.

In recent years, we have noticed changes in the department’s top-level decision-making. The hard-earned scientific and professional culture that used to make it a professional department, respected by colleagues and academics globally, has become noticeably weaker.

We urge the government to return to a professional-led department and reverse this move away from science-based assessment and decision-making. This is essential if the department is to keep its reputation as a respected organisation that we trust to get the science right when developing policy recommendations and programmes.

Alexis Lau, professor, and Bill Barron, adjunct associate professor, division of environment, Hong Kong University of Science and Technology

A new study suggests that air pollution is even worse than thought


THE capital’s “airpocalypse”, the choking smog that descended on Beijing in the winter of 2012-13, galvanised public opinion and spooked the government. The strange thing is, though, that information about air pollution—how extensive it is, how much damage it does—has long been sketchy, based mostly on satellite data or computer models. Until now.

Responding to the outcry, the government set up a national air-reporting system which now has almost 1,000 monitoring stations, pumping out hourly reports on six pollutants, including sulphur dioxide, ozone and (the main culprit) particulate matter less than 2.5 microns in diameter, or PM2.5. These are tiny particles which lodge in the lungs and cause respiratory disease. The six are the main cause of local pollution but have little to do with climate change, since they do not include carbon dioxide, the main greenhouse gas. Scientists from Berkeley Earth, a not-for-profit foundation in America, have trawled through this recent cloud of data for the four months to early August 2014, sieved out the bits that are manifestly wrong (readings where the dial seems to be stuck, for instance) and emerged with the most detailed and up-to-date picture of Chinese air pollution so far.

Pollution is sky-high everywhere in China. Some 83% of Chinese are exposed to air that, in America, would be deemed by the Environmental Protection Agency either to be unhealthy or unhealthy for sensitive groups. Almost half the population of China experiences levels of PM2.5 that are above America’s highest threshold. That is even worse than the satellite data had suggested.

Berkeley Earth’s scientific director, Richard Muller, says breathing Beijing’s air is the equivalent of smoking almost 40 cigarettes a day and calculates that air pollution causes 1.6m deaths a year in China, or 17% of the total. A previous estimate, based on a study of pollution in the Huai river basin (which lies between the Yellow and Yangzi rivers), put the toll at 1.2m deaths a year—still high.

The sliver of good news is that pollution levels are better in some places than in others. They are worst in the corridor between Beijing and Shanghai and least bad in the south (see map—the study covers China east of 95ºE, accounting for 97% of China’s population), probably because that area was washed by monsoon rains during the period of the study. More importantly, levels of PM2.5 in large western cities such as Chongqing and Chengdu are about half the national average. Figuring out what they are doing right would be a first step towards reducing the smog elsewhere.

Air pollution in Central and Causeway Bay exceeds WHO levels 280 days in a year

Air pollution levels in Central and Causeway Bay violated global health and safety standards for almost 280 days in the past year, with Des Voeux Road and Hennessy Road experiencing the worst levels of fine particulate matter on Hong Kong Island, a new study has found.

The air quality study, results of which were announced on Thursday, measured fine particulate matter known as PM2.5 in the air on the northern shore of Hong Kong Island along the tramway, by installing a monitoring unit on a tram car for a year’s worth of constant monitoring.

Even in Eastern District, where there was less traffic, the PM2.5 levels exceeded the international standard for more than 80 days in a year, the study found.

“The study offers another set of data to confirm the air pollution in the city is very serious,” said Simon Ng, chief research officer of Civic Exchange, a think tank that worked with the University of Science and Technology on the research.

“Our government must make it a policy priority to improve roadside air quality in major urban street canyons.”

Ng cited an earlier University of Hong Kong study that suggested older people were particularly vulnerable to the pollution, which could lead to respirational problems and heart conditions.

The new study, conducted between March last year and February this year, also found that areas with good ventilation and lower buildings helped to dispense the pollution.

The World Health Organisation’s recommended standard for PM2.5 is 25 millionths of a gram per cubic metre daily, and 10 millionths of a gram per cubic metre as an annual mean.

But Des Voeux Road has the highest concentration, registering 55 millionths of a gram per cubic metre as its annual mean, followed by Hennessy Road between Tonnochy Road in Wai Chai to the west and Yee Wo Street in Causeway Bay to the east.

In general, Central and Causeway Bay exceeded the WHO daily standard for almost 280 days in the yearlong study. But areas around spacious Victoria Park contained lower levels of the harmful particles than Yee Wo Street, which is congested with tall buildings, despite heavy traffic in both areas, the study suggested.

Professor Jimmy Fung, head of HKUST’s Division of Environment, said good city planning would help to ease the pressing problem. “The government should devise a long term strategy to improve wind and air dispersion in urban street canyons with every new development and urban re-development opportunities.

“He said pedestrianisation scheme and low emission zone should be considered in locations where roadside air quality is really bad, such as Des Voeux Road West, Hennessy Road and King’s Road.

Source URL (modified on Apr 30th 2015, 6:54pm):

Exposure to air pollution may damage brains

Long-term exposure to fine particle air pollution, even at low levels, may cause subtle structural changes in the brain that could precede cognitive impairment and hidden brain damage, according to research in the journal Stroke.

Between 1995 and 2005, researchers tracked 943 adults from Boston and throughout New England and New York, who were relatively healthy and free of dementia and stroke. They found a 2 microgram per cubic metre of air increase in PM2.5, a range commonly observed across a metropolitan region, was associated with a 0.32 per cent smaller total cerebral brain volume – similar to about one year of brain ageing – and a 46 per cent higher risk of covert brain infarcts, a type of silent stroke. Fine particle air pollution, or PM2.5, comes from burning wood or coal, car exhaust and other sources.

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Hong Kong’s elderly face special air pollution risk, unique study finds

Research over 13 years shows a link between fine particles and increased death rates

A groundbreaking tracker study offers evidence for the first time that the fine suspended particles known as PM2.5 lead to a higher death rate among elderly people in the city.

Conducted by a team from the University of Hong Kong’s School of Public Health, the study successfully tracked more than 60,200 elderly Hongkongers for 10 to 13 years, from 1998 to 2011, and analysed the mortality rate in correlation to the levels of PM2.5 where they lived. There are participants from all 18 districts.

Its results were published yesterday in journal Environmental Health Perspectives.

“There have been studies on the lethalness of PM2.5 and other pollutants but no data at all in Asia … this study provides new evidence on mortality from the long-term effects of being exposed to PM2.5 among the elderly,” said HKU associate professor Dr Wong Chit-ming, of the School of Public Health, who led the study. “This refutes [claims] that perhaps Asians are less susceptible to the effects of PM2.5.”

The study – which used Nasa satellites to narrow down PM2.5 levels by square kilometre – was the first of its kind in Asia not just Hong Kong, and was rare worldwide in its scope and detail, Wong said. While most overseas studies compare different cities, HKU’s examined Hong Kong in detail, and can therefore give more accurate results specific to the city.

The study is also relevant as Hong Kong grapples with a fast-ageing population.

Every 10-unit increase in PM2.5 correlated to a 22 per cent hike in deaths by cardiovascular causes, a 42 per cent increase in coronary heart disease and a 24 per cent increase in strokes.

The study took into account participants’ individual variables – health records, income, education level and lifestyle habits such as smoking – as well as the socio-economic status of the communities in which they lived, Wong said. The variables were factored in to the calculations.

There were around 16,000 deaths from natural causes during the study. The report stated that survival was highest among those who were exposed to the least amount of PM2.5, and “markedly lower” for those with high exposure.

The World Health Organisation sets 25 micrograms per square metre as the maximum 24-hour average concentration for PM2.5. Hong Kong averages 40 to 50, while mainland readings often surpass 100.

Source URL (modified on Apr 26th 2015, 4:01am):

Air pollution , stroke, and anxiety

Particulate air pollution is an emerging risk factor for an increasing number of common conditions

The effects of air pollution on the lungs and heart are now widely appreciated, with expanding evidence for an important role in cardiac disease.1 The Global Burden of Disease Study identified fine particulate matter (PM2.5) in outdoor air and household air pollution from use of solid fuels as the ninth and fourth leading risk factors, respectively, for disease worldwide,2 and the World Health Organization attributes one in every eight deaths to air pollution.3 The effects of air pollution are not limited to cardiopulmonary diseases. Recent evidence suggests a role in diverse outcomes, including diabetes,4 low birth weight, and preterm birth.5 This research stems from improved understanding of the role of air pollution in initiating systemic inflammation, a response that may affect multiple organ systems. Two linked studies (doi:10.1136/bmj.h1295, doi:10.1136/bmj.h1111) add to growing evidence that air pollution is an important risk factor for an increasing number of common diseases.6 7

In the first of the two papers, Shah and colleagues6 systematically reviewed and meta-analysed 103 studies conducted in 28 countries and including 6.2 million events to assess the role of short term fluctuations in air pollution as a trigger for stroke. Although evidence from several cohort studies of long term exposure to particulate matter indicates associations with stroke mortality, such findings are not universal.8

The role of air pollution as a possible trigger for stroke has important implications for disease burden, especially in China where air pollution and the incidence of (especially haemorrhagic) stroke are high. In their analysis, Shah and colleagues found that increases in each of the common gaseous and particulate air pollutants were significantly associated with admission to hospital for stroke or stroke related mortality, with associations strongest for strokes on the same day as exposure; increased ozone was only weakly associated with cerebrovascular events.

Air pollution remained significantly associated with stroke in sensitivity analyses that adjusted for potential biases related to quality of outcome ascertainment, assessment of exposure, and adjustment for confounders. This analysis supports a role for air pollution as a modifiable risk factor for stroke, although associations with air pollution were less precise for haemorrhagic stroke than for ischaemic stroke. The impact of chronic exposure to air pollution on development of carotid atherosclerosis (a precursor for stroke) remains unclear. Although this is not covered in the analysis, evidence of an association is growing.9

Since air pollution causes systemic inflammation, it is reasonable that researchers have now turned to the arena of mental health, a leading priority for research given the relative absence of known modifiable risk factors and a high and growing disease burden.10 In the second linked paper, Power and colleagues exploit rich data in the Nurse’s Health Study cohort to assess the role of particulate pollution on prevalent anxiety symptoms.7 They found an exposure dependent association between higher levels of PM2.5 and increased symptoms of anxiety, and indications that associations were stronger for exposures in the month immediately preceding the scoring of anxiety.

These observations were supported by several sensitivity analyses, which indicated that associations were robust to broad geographical region, health status (to control for the possibility of anxiety as a sequela of cardiopulmonary effects of air pollution), and demographic characteristics, although the study was limited to older women. Power and colleagues’ findings add to a growing literature on the mental health effects of air pollution, including a small but intriguing body of research linking short term variability in air pollution to suicide.11

Power and colleagues used spatiotemporal exposure estimates and reported stronger effects for more recent exposures, reducing confounding by spatially varying factors correlated with air pollution. Since effects were observed over all time periods, spatial variation seems to have had an important influence on effect estimates. Furthermore, although effects were observed in all geographical regions, the investigators did not examine other potentially adverse (for example, noise, barometric pressure, solar intensity) or healthy (for example, natural spaces) environmental exposures that may operate at different scales. Indeed, evidence is accumulating that natural spaces may have beneficial effects on stress and social cohesion, both of which deserve further study in relation to mental health.12

As with any observational study, questions remain, as the authors acknowledge, and the findings should be replicated in other populations and with other study designs. Moreover, although these observations are biologically plausible, given links between inflammation and anxiety there is a need for greater mechanistic supporting evidence, of the type that now exists for associations between particulate matter and pulmonary, cardiac, and circulatory disease.

The findings of these two studies support a sharper focus on air pollution as a leading global health concern. They also suggest opportunities for reducing the prevalence of two debilitating and common diseases. One of the unique features of air pollution as a risk factor for disease is that exposure to air pollution is almost universal. While this is a primary reason for the large disease burden attributable to outdoor air pollution, it also follows that even modest reductions in pollution could have widespread benefits throughout populations. The two linked papers in this issue confirm the urgent need to manage air pollution globally as a cause of ill health and offer the promise that reducing pollution could be a cost effective way to reduce the large burden of disease from both stroke and poor mental health.


Cite this as: BMJ 2015;350:h1510


Research, doi:10.1136/bmj.h1295
Research, doi:10.1136/bmj.h1111

Competing interests: I have read and understood the BMJ policy on declaration of interests and declare the following: none.

Provenance and peer review: Commissioned; not externally peer reviewed.

1. ↵
Newby DE, Mannucci PM, Tell GS, et al. Expert position paper on air pollution and cardiovascular disease. Eur Heart J2015;36:83-93b.
OpenUrlFREE Full Text
2. ↵
Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet2012;380:2224-60.
OpenUrlCrossRefMedlineWeb of Science
3. ↵
World Health Organization. Burden of disease from ambient and household air pollution. 2014.
4. ↵
Eze IC, Hemkens LG, Bucher HC, et al. Association between ambient air pollution and diabetes mellitus in Europe and North America: systematic review and meta-analysis. Environ Health Perspect2015; published online 27 Jan.
5. ↵
Stieb DM, Chen L, Eshoul M, et al. Ambient air pollution, birth weight and preterm birth: a systematic review and meta-analysis. Environ Res2012;117:100-11.
OpenUrlMedlineWeb of Science
6. ↵
Shah ASV, Lee KK, McAllister DA, et al. Short term exposure to air pollution and stroke: a systematic review and meta-analysis. BMJ2015;350:h1295.
OpenUrlAbstract/FREE Full Text
7. ↵
Power MC, Kioumourtzoglou M-A, Hart JE, et al. The relation between past exposure to fine particulate air pollution and prevalent anxiety: observational cohort study. BMJ2015;350:h1111
OpenUrlAbstract/FREE Full Text
8. ↵
Ljungman PL, Mittleman MA. Ambient air pollution and stroke. Stroke2014;45:3734-41.
OpenUrlFREE Full Text
9. ↵
Adar SD, Sheppard L, Vedal S, et al. Fine particulate air pollution and the progression of carotid intima-medial thickness: a prospective cohort study from the multi-ethnic study of atherosclerosis and air pollution. PLoS Med2013;10:e1001430.
10. ↵
Murray CJ, Vos T, Lozano R, et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 201215;380:2197-223.
11. ↵
Bakian AV, Huber RS, Coon H, et al. Acute air pollution exposure and risk of suicide completion. Am J Epidemiol2015;181:295-303.
OpenUrlAbstract/FREE Full Text
12. ↵
Hartig T, Mitchell R, de Vries S, et al. Nature and health. Annu Rev Public Health 2014;35:207-28.
OpenUrlCrossRefMedlineWeb of Science