Amyloid-β (Aβ) deposition is a feature of Alzheimer disease (AD) and may be promoted by exogenous factors, such as ambient air quality.To examine the association between the likelihood of amyloid positron emission tomography (PET) scan positivity and ambient air quality in individuals with cognitive impairment.This cross-sectional study used data from the Imaging Dementia-Evidence for Amyloid Scanning Study, which included more than 18 000 US participants with cognitive impairment who received an amyloid PET scan with 1 of 3 Aβ tracers (fluorine 18 [18F]-labeled florbetapir, 18F-labeled florbetaben, or 18F-labeled flutemetamol) between February 16, 2016, and January 10, 2018. A sample of older adults with mild cognitive impairment (MCI) or dementia was selected.Air pollution was estimated at the patient residence using predicted fine particulate matter (PM2.5) and ground-level ozone (O3) concentrations from the Environmental Protection Agency Downscaler model. Air quality was estimated at 2002 to 2003 (early, or approximately 14 [range, 13-15] years before amyloid PET scan) and 2015 to 2016 (late, or approximately 1 [range, 0-2] years before amyloid PET scan).Primary outcome measure was the association between air pollution and the likelihood of amyloid PET scan positivity, which was measured as odds ratios (ORs) and marginal effects, adjusting for demographic, lifestyle, and socioeconomic factors and medical comorbidities, including respiratory, cardiovascular, cerebrovascular, psychiatric, and neurological conditions.The data set included 18 178 patients, of which 10 991 (60.5%) had MCI and 7187 (39.5%) had dementia (mean [SD] age, 75.8 [6.3] years; 9333 women [51.3%]). Living in areas with higher estimated biennial PM2.5 concentrations in 2002 to 2003 was associated with a higher likelihood of amyloid PET scan positivity (adjusted OR, 1.10; 95% CI, 1.05-1.15; z score = 3.93; false discovery rate [FDR]-corrected P < .001; per 4-μg/m3 increments). Results were similar for 2015 to 2016 data (OR, 1.15; 95% CI, 1.05-1.26, z score = 3.14; FDR-corrected P = .003). An average marginal effect (AME) of +0.5% (SE = 0.1%; z score, 3.93; 95% CI, 0.3%-0.7%; FDR-corrected P < .001) probability of amyloid PET scan positivity for each 1-μg/m3 increase in PM2.5 was observed for 2002 to 2003, whereas an AME of +0.8% (SE = 0.2%; z score = 3.15; 95% CI, 0.3%-1.2%; FDR-corrected P = .002) probability was observed for 2015 to 2016. Post hoc analyses showed no effect modification by sex (2002-2003: interaction term β = 1.01 [95% CI, 0.99-1.04; z score = 1.13; FDR-corrected P = .56]; 2015-2016: β = 1.02 [95% CI, 0.98-1.07; z score = 0.91; FDR-corrected P = .56]) or clinical stage (2002-2003: interaction term β = 1.01 [95% CI, 0.99-1.03; z score = 0.77; FDR-corrected P = .58]; 2015-2016: β = 1.03; 95% CI, 0.99-1.08; z score = 1.46; FDR-corrected P = .47]). Exposure to higher O3 concentrations was not associated with amyloid PET scan positivity in both time windows.This study found that higher PM2.5 concentrations appeared to be associated with brain Aβ plaques. These findings suggest the need to consider airborne toxic pollutants associated with Aβ pathology in public health policy decisions and to inform individual lifetime risk of developing AD and dementia.

China's extraordinary economic growth, industrialization, and urbanization, coupled with inadequate investment in basic water supply and treatment infrastructure, have resulted in widespread water pollution. In China today approximately 700 million people--over half the population--consume drinking water contaminated with levels of animal and human excreta that exceed maximum permissible levels by as much as 86% in rural areas and 28% in urban areas. By the year 2000, the volume of wastewater produced could double from 1990 levels to almost 78 billion tons. These are alarming trends with potentially serious consequences for human health. This paper reviews and analyzes recent Chinese reports on public health and water resources to shed light on what recent trends imply for China's environmental risk transition. This paper has two major conclusions. First, the critical deficits in basic water supply and sewage treatment infrastructure have increased the risk of exposure to infectious and parasitic disease and to a growing volume of industrial chemicals, heavy metals, and algal toxins. Second, the lack of coordination between environmental and public health objectives, a complex and fragmented system to manage water resources, and the general treatment of water as a common property resource mean that the water quality and quantity problems observed as well as the health threats identified are likely to become more acute.

Nearly all China's rural residents and a shrinking fraction of urban residents use solid fuels (biomass and coal) for household cooking and/or heating. Consequently, global meta-analyses of epidemiologic studies indicate that indoor air pollution from solid fuel use in China is responsible for approximately 420,000 premature deaths annually, more than the approximately 300,000 attributed to urban outdoor air pollution in the country. Our objective in this review was to help elucidate the extent of this indoor air pollution health hazard.We reviewed approximately 200 publications in both Chinese- and English-language journals that reported health effects, exposure characteristics, and fuel/stove intervention options.Observed health effects include respiratory illnesses, lung cancer, chronic obstructive pulmonary disease, weakening of the immune system, and reduction in lung function. Arsenic poisoning and fluorosis resulting from the use of "poisonous" coal have been observed in certain regions of China. Although attempts have been made in a few studies to identify specific coal smoke constituents responsible for specific adverse health effects, the majority of indoor air measurements include those of only particulate matter, carbon monoxide, sulfur dioxide, and/or nitrogen dioxide. These measurements indicate that pollution levels in households using solid fuel generally exceed China's indoor air quality standards. Intervention technologies ranging from simply adding a chimney to the more complex modernized bioenergy program are available, but they can be viable only with coordinated support from the government and the commercial sector.

Evidence of spatial disparity in dementia mortality in China has been found to have higher dementia mortality in eastern and rural China. Regional factors of physical and social features may be influencing this spatial disparity. However, the extent of spatial difference in dementia mortality across small regional localities is unclear. This study aims to investigate the geographic variations in mortality and risk of all dementia subtypes and identify the effect of the associated environmental risk factors.

The risk of dementia and Alzheimer's disease in Latin America and the Caribbean (LAC) rises with increasing age and polluted air. Currently, at least 172 million people breathe unhealthy levels of air pollution in LAC countries. Several cohort studies have indicated that air pollution increases the risk of developing dementia and neurodegenerative diseases, but the mechanisms underlying the association are still not clear. Air pollution causes and aggravates five established risk factors for dementia (obesity, hypertension, stroke, diabetes mellitus, and heart diseases) and is linked to three other risk factors (physical inactivity, cognitive inactivity, and depression). Some of these risk factors could be mediating the association between air pollution and dementia. Reducing the risks for dementia is crucial and urgently needed in LAC countries. There is room for improving air quality in many urban areas in the LAC region and other low- and middle-income countries (LMICs), a routealready explored by many urban areas in developing regions. Moreover, reducing air pollution has proved to improve health outcomes before. In this article, we propose that despite the ongoing and valid scientific discussion, if air pollution can or cannot directly affect the brain and cause or aggravate dementia, we are ready to consider air pollution as a potentially modifiable risk factor for dementia in LAC and possibly in other LMICs. We suggest that controlling and reducing current air pollution levels in LAC and other LMIC regions now could strongly contribute.

We aimed to assess the association between low-level air pollution and the risk of dementia, and examine the modification effect by genetic susceptibility on the relationship.

\n Most of the population in developing countries live in places with unsafe air. Utilizing variations in transitory and cumulative air pollution exposures for the same individuals over time in China, we provide evidence that polluted air may impede cognitive ability as people become older, especially for less educated men. Cutting annual mean concentration of particulate matter smaller than 10 μm (PM10) in China to the Environmental Protection Agency’s standard (50 μg/m\n 3\n ) would move people from the median to the 63rd percentile (verbal test scores) and the 58th percentile (math test scores), respectively. The damage on the aging brain by air pollution likely imposes substantial health and economic costs, considering that cognitive functioning is critical for the elderly for both running daily errands and making high-stake decisions.\n

Background: Ambient air pollution has been associated with Alzheimer’s disease (AD) in the elderly. However, its effects on AD have not been meta-analyzed comprehensively. Objective: We conducted a systematic review and meta-analysis to assess the associations between air pollution and AD incidence. Methods: We searched PubMed and Web of Science for indexed publications up to March 2020. Odds risk (OR) and confidence intervals (CI) were estimated for particulate matter (PM)10 (PM10), PM2.5, ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). The subgroup analysis was conducted based on the pollution levels. Results: Nine studies were included in the meta-analysis and review. The OR per 10μg/m3 increase of PM2.5 was 1.95 (95% CI: 0.88–4.30). The corresponding values per 10μg/m3 increment of other pollutants were 1.03 (95% CI: 0.68–1.57) for O3, 1.00 (95% CI: 0.89–1.13) for NO2, and 0.95 (95% CI: 0.91–0.99) for PM10 (only one study), respectively. Overall OR of the five air pollutants above with AD was 1.32 (95% CI: 1.09–1.61), suggesting a positive association between ambient air pollution and AD incidence. The sub-analysis indicated that the OR (2.20) in heavily polluted regions was notably higher than that in lightly polluted regions (1.06). Although AD risk rate data related to SO2 or CO exposure are still limited, the epidemiologic and toxicological evidence indicated that higher concentration of SO2 or CO exposure increased risks of dementia, implying that SO2 or CO might have a potential impact on AD. Conclusion: Air pollution exposure may exacerbate AD development.

Background Outdoor air pollution is now a well-known risk factor for morbidity and mortality, and is increasingly being identified as a major risk factor for stroke. Methods A narrative literature review of the effects of short and long-term exposure to air pollution on stroke and dementia risk and cognitive functioning. Results Ten papers on stroke and 17 on dementia were selected. Air pollution, and in particular small particulate matter, contributes to about one-third of the global stroke burden and about one-fifth of the global burden of dementia. It particularly affects vulnerable patients with other vascular risk factors or a prior history of stroke in low- and medium-income countries. New pathophysiological mechanisms of the cause-effect associations are suggested. Conclusion Air pollution should be considered as a new modifiable cerebrovascular and neurodegenerative risk factor. This massive worldwide public health problem requires environmental health policies able to reduce air pollution and thus the stroke and dementia burden.

Updated information on the burden of Alzheimer's disease and other forms of dementia are of great importance for evidence-based health care planning. However, such an estimate has been lacking in Chinese populations at both national and provincial levels.To estimate the temporal trends and the attributable burdens of selected risk factors of Alzheimer's disease and other forms of dementia in China.This is an observational description of the Global Burden of Diseases Study 2019 (GBD 2019). Data on incidence, mortality, prevalence, disability-adjusted life years (DALYs), years lived with disability (YLDs), and years of life lost (YLLs) of Alzheimer's disease and other forms of dementia were derived from the GBD 2019 study at both national and provincial levels in China.Six indicators were used: incidence, mortality, prevalence, DALYs, YLLs, and YLDs. Absolute numbers in detail by age, sex, region, and age-standardized rates (with 95% uncertainty intervals) were calculated.There were notable increasing trends in the number of deaths (247·9%), incidence (264·8%), prevalence (296·5%), DALYs (228·1%), YLDs (308·7%) and YLLs (201·7%) from 1990 to 2019, respectively. The corresponding age-standardized rates increased by 6·2%, 19·3%, 33·6%, 10·7%, 33·4% and 3·1%. Smoking, high body mass index, high fasting plasma glucose levels, and metabolic risks were the four leading risk factors. Higher burden was observed among females versus males and in the more developed regions.The disease burden in China were increasing substantially. Regional differences of the disease burden are accompanied by discrepancies of economic level and geographical location, as well as different levels of exposure to risk factors. Targeted prevention and control strategies are urgently needed to reduce the disease burden.

Air pollution has long been a significant environmental health issue. Previous studies have employed diverse methodologies to investigate the impacts of air pollution on public health, yet few have thoroughly examined its spatiotemporal heterogeneity. Based on this, this study investigated the spatiotemporal heterogeneity of the impacts of air pollution on public health in 31 provinces in China from 2013 to 2020 based on the theoretical framework of multifactorial health decision-making and combined with the spatial durbin model and the geographically and temporally weighted regression model. The findings indicate that: (1) Air pollution and public health as measured by the incidence of respiratory diseases (IRD) in China exhibit significant spatial positive correlation and local spatial aggregation. (2) Air pollution demonstrates noteworthy spatial spillover effects. After controlling for economic development and living environment factors, including disposable income, population density, and urbanization rate, the direct and indirect spatial impacts of air pollution on IRD are measured at 3.552 and 2.848, correspondingly. (3) China’s IRD is primarily influenced by various factors such as air pollution, economic development, living conditions, and healthcare, and the degree of its influence demonstrates an uneven spatiotemporal distribution trend. The findings of this study hold considerable practical significance for mitigating air pollution and safeguarding public health.

We evaluated studies that used the World Health Organization’s (WHO) AirQ and AirQ+ tools for air pollution (AP) health risk assessment (HRA) and provided best practice suggestions for future assessments.

Air pollution, especially the fine particulate matter (PM), may impair cognitive performance, but its short-term impact remains poorly understood. We investigated the short-term associations of PM with the cognitive performances of 954 white males measured as the global cognitive function (GCF) and Mini-Mental State Examination (MMSE) scores, and further explored whether taking nonsteroidal anti-inflammatory drugs (NSAIDs) could modify their relationships. Higher short-term exposure to PM demonstrated non-linear negative associations with cognitive function. Compared with the lowest quartile of the 28-day average PM concentration, the 2, 3, and 4 quartiles were associated with 0.378-, 0.376-, and 0.499-unit decreases in GCF score, 0.484-, 0.315-, and 0.414-unit decreases in MMSE score, and 69%, 45%, and 63% greater odds of low MMSE scores (≤25), respectively. Such adverse effects were attenuated among NSAIDs users compared to non-users. This study elucidates the short-term impacts of air pollution on cognition and warrants further investigations on the modifying effects of NSAIDs.

The lack of interoperability in Britain’s medical records systems precludes the realisation of benefits generated by increased spending elsewhere in healthcare. Growing concerns regarding the security of online medical data following breaches, and regarding regulations governing data ownership, mandate strict parameters in the development of efficient methods to administrate medical records. Furthermore, consideration must be placed on the rise of connected devices, which vastly increase the amount of data that can be collected in order to improve a patient’s long-term health outcomes. Increasing numbers of healthcare systems are developing Blockchain-based systems to manage medical data. A Blockchain is a decentralised, continuously growing online ledger of records, validated by members of the network. Traditionally used to manage cryptocurrency records, distributed ledger technology can be applied to various aspects of healthcare. In this manuscript, we focus on how Electronic Medical Records in particular can be managed by Blockchain, and how the introduction of this novel technology can create a more efficient and interoperable infrastructure to manage records that leads to improved healthcare outcomes, while maintaining patient data ownership and without compromising privacy or security of sensitive data.

It is challenging at baseline to predict when and which individuals who meet criteria for mild cognitive impairment (MCI) will ultimately progress to Alzheimer's disease (AD) dementia.A deep learning method is developed and validated based on magnetic resonance imaging scans of 2146 subjects (803 for training and 1343 for validation) to predict MCI subjects' progression to AD dementia in a time-to-event analysis setting.The deep-learning time-to-event model predicted individual subjects' progression to AD dementia with a concordance index of 0.762 on 439 Alzheimer's Disease Neuroimaging Initiative testing MCI subjects with follow-up duration from 6 to 78 months (quartiles: [24, 42, 54]) and a concordance index of 0.781 on 40 Australian Imaging Biomarkers and Lifestyle Study of Aging testing MCI subjects with follow-up duration from 18 to 54 months (quartiles: [18, 36, 54]). The predicted progression risk also clustered individual subjects into subgroups with significant differences in their progression time to AD dementia (P < .0002). Improved performance for predicting progression to AD dementia (concordance index = 0.864) was obtained when the deep learning-based progression risk was combined with baseline clinical measures.Our method provides a cost effective and accurate means for prognosis and potentially to facilitate enrollment in clinical trials with individuals likely to progress within a specific temporal period.Copyright © 2019 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

Previous studies have empirically investigated the influence of China’s urbanization on atmosphere pollution, the findings in the literature are however controversial and inconclusive across regions, data, and methodologies. This study uses the city-level panel data, 113 key cities of environment protection from the Ministry of Ecology and Environment, covering most of the provinces in China for the period 2013–2017 to investigate the different impacts of the new urbanization pilot policy on air quality and related air pollutants including six major pollutant sources, which are PM2.5, PM10, SO2, CO, NO2, and O3. The study finds that, first, based on the difference-in-difference (DID) method, the new urbanization on average tends to improve the air quality in the pilot cities. Second, based on the quantile DID method, the new urbanization tends to improve the air quality in the lower air quality quantiles (0.1–0.6); however, it has no significant impact in the higher air quality quantiles (0.7–0.9). Third, the impacts of the new urbanization on the air quality vary among different energy-related air pollutants. The new urbanization pilot policy tends to restrain SO2, PM10, and PM2.5, increase CO and O3 and has no impact on NO2. The results indicate that China should pay more attention to promote green consumption and new energy applications and increase urban construction efficiency to further reducing air pollutions in the new urbanization process.

Given a fast-growing aging population in South Korea, the prevalence of cognitive impairment in elderly is increasing. Despite growing evidence of air pollution exposure as one of the risk factors for declining cognition, few studies have been conducted on gender difference in the relation of cognitive function associated with outdoor air pollution. The aim of this study is to investigate the effect modification of gender difference in the association between cognitive function and air pollutant exposure (PM, PM, and NO). The study focused on elderly, and the resulting sample included 1,484 participants aged 55 and older with no neurologic diseases, recruited from the four regions in Korea (Seoul, Incheon, Pyeongchang, and Wonju). We used the Mini-Mental State Examination (MMSE) score (with the conventional cut-off point "23-24") to assess cognitive decline as the primary outcome of the study. Air pollution data used in this study were based on the 5-year average of predicted PM and NO concentrations, as well as the 2015 average PM concentration. Additionally, a survey questionnaire was utilized to obtain information about general health assessment. To explore gender differences in the effects of air pollution exposure on cognitive function, we used penalized logistic regression, negative binomial regression, and generalized linear mixed model analyses. Subgroup analyses were also performed by the geographic location of residence (metropolitan vs. non-metropolitan). We found that women than men had a higher risk for decreased cognitive function associated with increased exposure to PM and PM, respectively, even after adjustments for confounding factors (OR 1.01 [95%CI 1.00-1.03] in PM; OR 1.03 [95%CI 1.01-1.07] in PM). After stratification by metropolitan status, we also found that the adverse effect of NO exposure on cognitive function was higher in women than men [OR 1.02 [95%CI 1.00-1.05] in metropolitan; OR 1.12 [95%CI 1.04-1.20] in non-metropolitan]. Notably, the magnitude of the effect sizes was greater among those in non-metropolitan regions than metropolitan ones. Although our findings suggest that the adverse effects of outdoor air pollution on cognitive function appeared to be higher in women than men, this should be tentatively reflected due to some limitations in our results. While additional research is warranted to confirm or dispute our results, our findings suggest an indication of the need for developing and implementing prevention or interventions with a focus on elderly women with increased risk for air pollution exposure.Copyright © 2019 Kim, Noh, Noh, Oh, Koh and Kim.

Background: The impact of air pollution on cognitive impairment in older people has not been fully understood. It is unclear which air pollutants are the culprit. Objective: We assessed the associations of six air pollutants and air quality index (AQI) with cognitive impairment. Methods: We examined 7,311 participants aged ≥60 years from the ZJMPHS cohort in China. They were interviewed for baseline socio-demographic and disease risk factors in 2014, and re-interviewed in 2015 and 2016, respectively. The presence of cognitive impairment was determined by the Chinese version of the Mini-Mental State Examination. Daily area-level data monitored for air pollution during 2013-2015 was then examined for associations with cognitive impairment in logistic regression models. Results: Over the two years follow-up, 1,652 participants developed cognitive impairment, of which 917 were severe cases. Continuous air pollution data showed the risk of cognitive impairment increased with exposure to PM2.5 (fully adjusted odds ratio [aOR] 1.04, 95% CI 1.01–1.08), PM10 (1.03, 1.001–1.06), and SO2 (1.04, 1.01–1.08), but not with NO2, CO, O3, and AQI. Categorized data analysis for low, middle, and high level exposure demonstrated that the aOR increased with PM2.5 and AQI, somehow with PM10 and CO, but not significantly with SO2 and NO2, and decreased with O3. The patterns for these associations with severe cognitive impairment were stronger. Conclusion: Lowering PM2.5, PM10, SO2, and CO level could reduce the risk of cognitive impairment in older Chinese. Strategies to target most important air pollutants should be an integral component of cognitive interventions.

Evidence suggests long-term exposure to fine particulate matter air pollution (PM2.5) is associated with a higher risk of cognitive impairment, especially among older adults. This study examines the relationship between PM2.5 exposure and cognitive function in China’s aging population.

Long-term exposure to PM2.5 is related to poor lung function and cognitive impairment, but less is known about the pathway involved in this association. We aimed to explore whether the effect of PM2.5 on cognitive function was mediated by lung function.

\n From 2013 to 2017, with the implementation of the toughest-ever clean air policy in China, significant declines in fine particle (PM\n 2.5\n ) concentrations occurred nationwide. Here we estimate the drivers of the improved PM\n 2.5\n air quality and the associated health benefits in China from 2013 to 2017 based on a measure-specific integrated evaluation approach, which combines a bottom-up emission inventory, a chemical transport model, and epidemiological exposure-response functions. The estimated national population–weighted annual mean PM\n 2.5\n concentrations decreased from 61.8 (95%CI: 53.3–70.0) to 42.0 µg/m\n 3\n (95% CI: 35.7–48.6) in 5 y, with dominant contributions from anthropogenic emission abatements. Although interannual meteorological variations could significantly alter PM\n 2.5\n concentrations, the corresponding effects on the 5-y trends were relatively small. The measure-by-measure evaluation indicated that strengthening industrial emission standards (power plants and emission-intensive industrial sectors), upgrades on industrial boilers, phasing out outdated industrial capacities, and promoting clean fuels in the residential sector were major effective measures in reducing PM\n 2.5\n pollution and health burdens. These measures were estimated to contribute to 6.6- (95% CI: 5.9–7.1), 4.4- (95% CI: 3.8–4.9), 2.8- (95% CI: 2.5–3.0), and 2.2- (95% CI: 2.0–2.5) µg/m\n 3\n declines in the national PM\n 2.5\n concentration in 2017, respectively, and further reduced PM\n 2.5\n -attributable excess deaths by 0.37 million (95% CI: 0.35–0.39), or 92% of the total avoided deaths. Our study confirms the effectiveness of China’s recent clean air actions, and the measure-by-measure evaluation provides insights into future clean air policy making in China and in other developing and polluting countries.\n

This study aims to explore the current status of dementia-specific diagnosis and treatment in China.This national survey was conducted in mainland China from September 2022 to February 2023, with strong support from the Cognitive Disorders Group of the Chinese Society of Neurology, Chinese Medical Association.Among 2721 hospitals surveyed, 244 (8.97%) have dementia-specific clinics (DSCs) and 166 (6.10%) have dementia-specific inpatient departments (DSIDs). Almost all hospitals have brain structural imaging capabilities and basic hematological examinations, but dementia-specific medical staff (DSMS) equipped for DSCs or DSIDs are rare. The proportion of patients with cognitive impairment receiving care through a DSCs or DSIDs is low, and most patients present with advanced (moderate to severe) disease.The survey shows that the proportion of DSCs and DSIDs is low, and the regional distribution varies significantly. Trained DSMS and specialized facilities for the diagnosis and treatment of dementia are inadequate.This study was a multi-center national research to comprehensively investigate the distribution and features of dementia-specific clinics and inpatient departments in mainland China, given that the limited literature was available regarding the dementia-specific centers. The study points to significant regional differences in the distribution of cognitive-specific clinics and inpatient departments in mainland China. More centers in Eastern Regions compared to Western Regions, a greater presence in provincial capitals as opposed to other cities, and a predominance of tertiary hospitals over non-tertiary ones. The aim is to provide data support for advancements in medical research within this field. Domestic dementia patients have inadequate access to specialized medical resources and expert assistance, which significantly contrasts with the growing number of dementia cases in China.© 2024 The Author(s). Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.

To understand the varieties, evaluation, treatment, and prognosis of severe neurological diseases using the third NCU survey in China.

Fine particulate matter (PM2.5), one of the major atmospheric pollutants, has a significant impact on human health. However, the determinant power of natural and socioeconomic factors on the spatial-temporal variation of PM2.5 pollution is controversial in China.