Temperature modulation of the adverse consequences on human mortality due to exposure to fine particulates: A study of multiple cities in China

Combined effects of ambient air pollution and temperature on mortality in Thailand

This study aimed to investigate the combined effects of air pollution and temperature on mortality in 34 provinces of Thailand by modeling temperature as a confounding factor and effect modifier, estimating the effects of air pollution at low, moderate, and high temperature categories defined by the 1st and 99th province-specific temperature percentiles. When the temperature was modeled as a confounding factor, the relative risk (RR) of mortality associated with a 10 µg/m3 increase in PM10 and PM2.5 (lag 0-2), and a 10-ppb increase in NO2 (lag 0-2) and O3 (lag 0-7) was respectively 1.0096 (95% Confidence Interval (CI): 1.0073, 1.0118), 1.0134 (95% CI: 1.0099, 1.0170), 1.0172 (95% CI: 1.0122, 1.0222), and 1.0164 (95% CI: 1.0093, 1.0236). Regarding temperature as an effect modifier, the combined effects of air pollution and temperature were observed as a U-shaped pattern, where the effects of PM10, PM2.5, NO2, and O3 on mortality were greater at low (< 1st percentile) and high (> 99th percentile) temperature days compared to those at moderate temperature days (1st - 99th percentile). The pattern of combined effects of air pollution and temperature remained robust even when different temperature percentiles were employed, except for that of NO2. Furthermore, the estimated effects of PM10, PM2.5, NO2, and O3 on mortality at high-temperature days were mitigated by high green density. Findings of this study revealed that extreme temperature (both hot and cold) could exacerbate the effect of air pollution on mortality, and higher green density mitigate the combined effects of air pollution and high temperature.

Exposure to submicron particulate matter and long-term survival: Cross-cohort analysis of 3 Chinese national surveys

BACKGROUND

Cohort evidence linking increased mortality with airborne fine particulate matter (PM2.5, particulate matter [PM] with aerodynamic diameter ≤2.5 μm) exposure was extensively validated worldwide. Nevertheless, long-term survival associated with submicron particulate matter (PM1, PM with aerodynamic diameter ≤1 μm) exposure remained largely unstudied, particularly in highly exposed populations.

METHODS

We performed a population-based investigation involving 86844 adults aged 16+ years from 3 national dynamic cohorts spanning from 2005 to 2018. Residential annual exposure to PM1 and PM2.5 was assigned for each follow-up year using satellite-derived spatiotemporal estimates at a 1-km2 resolution. The concentration of PM1-2.5 (PM with aerodynamic diameter between 1 and 2.5 μm) was calculated by subtracting PM1 from PM2.5. Time-independent Cox proportional hazards regression models were applied to assess the associations of all-cause mortality with long-term exposure to size-specific particles. To investigate the effect of PM1 on PM2.5-mortality associations, we categorized participants into low, medium, and high groups based on PM1/PM2.5 ratio and examined the risk of PM2.5-associated mortality in each stratum. Effect modifications were checked via subgroup analyses.

RESULTS

A total of 18722 deaths occurred during 497069.2 person-years of follow-up (median 5.7 years). Participants were exposed to an average annual concentration of 31.8 μg/m³ (range: 7.6-66.8 μg/m³) for PM1, 56.3 μg/m³ (range: 19.8-127.2 μg/m³) for PM2.5, and 24.5 μg/m³ (range: 7.3-60.3 μg/m³) for PM1-2.5. PM1, PM2.5, and PM1-2.5 were consistently associated with elevated mortality risks, with a hazard ratio (HR) of 1.029 (95% confidence interval [CI]: 1.013-1.046), 1.014 (95% CI: 1.005-1.023), and 1.019 (95% CI: 1.001-1.038) for each 10-μg/m3 increase in exposure, respectively. Compared with low (HR = 0.986, 95% CI: 0.967-1.004) and medium (HR = 1.015, 95% CI: 1.002-1.029) PM1/PM2.5 ratio groups, PM2.5-related risk of mortality was more pronounced in high PM1/PM2.5 ratio stratum (HR = 1.041, 95% CI: 1.019-1.064). Greater risks of mortality associated with size-specific particles were found among the elderly (>80 years old), southeastern participants, and those living in warmer areas.

CONCLUSIONS

This study demonstrated that long-term exposure to PM1, PM2.5, and PM1-2.5 was associated with heightened mortality, and PM1 may play a predominant role in PM2.5-induced risk. Our results emphasized the population health implications of establishing ambient PM1 air quality guidelines to mitigate the burden of premature mortality stemming from particulate air pollution.

Short-Term Interaction Effects of PM2.5 and O3 on Daily Mortality: A Time-Series Study of Multiple Cities in China

In recent years, PM2.5 and O3 have been the two main pollutants affecting public health in China, but the interaction of the two pollutants on human health remains unclear. A two-stage analytical approach was used to investigate the relationships of PM2.5-O3 co-pollution with nonaccidental, cardiovascular, and respiratory mortality levels across 14 cities in China. We first utilized a generalized additive model (GAM) to determine the city-specific associations of PM2.5 and O3 with daily mortality. The associations were then combined at the national and regional levels using meta-analysis. To investigate the potential interactions between the two pollutants and cause-specific mortality, we performed stratified analyses by co-pollutant exposure levels and the synergy index (SI) (SI > 1 indicates a synergistic interaction). The effect of changes in the two pollutants' concentrations (in 10 μg/m3 increases) on mortality was assessed. The stratification analysis results suggested that each 10 μg/m3 increase in PM2.5 at lag0-1 (lag01) in the low, moderate, and high strata of the O3 concentrations increased nonaccidental mortality by 0.07% (95% confidence interval: -0.03%, 0.17%), 0.33% (0.13%, 0.53%), and 0.68% (0.30%, 1.06%), respectively, with significant between-group differences (p < 0.001). Moreover, each 10 μg/m3 increase in O3 (lag01) in the low, moderate, and high strata of the PM2.5 concentrations increased nonaccidental mortality by 0.15% (-0.06%, 0.36%), 0.53% (0.19%, 0.87%), and 0.75% (0.14%, 1.36%), respectively, with significant between-group differences (p < 0.001). We also found substantial synergistic interactions between the two pollutants and nonaccidental, cardiovascular, and respiratory mortality levels, with SI values of 1.48, 1.51, and 1.33, respectively. Additionally, a subgroup analysis revealed that the interaction of these two pollutants on nonaccidental mortality were greater in South China compared to elsewhere, and during the warm season compared to during the cold season. Our findings suggested that the simultaneous control of PM2.5 and O3 within the context of combined air pollution could significantly decrease the disease risk, especially in southern China and during the warm season.

A Review of the Interactive Effects of Climate and Air Pollution on Human Health in China

PURPOSE OF REVIEW

Through a systematic search of peer-reviewed epidemiologic studies, we reviewed the literature on the human health impacts of climate and ambient air pollution, focusing on recently published studies in China. Selected previous literature is discussed where relevant in tracing the origins.

RECENT FINDINGS

Climate variables and air pollution have a complex interplay in affecting human health. The bulk of the literature we reviewed focuses on the air pollutants ozone and fine particulate matter and temperatures (including hot and cold extremes). The interaction between temperature and ozone presented substantial interaction, but evidence about the interactive effects of temperature with other air pollutants is inconsistent. Most included studies used a time-series design, usually with daily mean temperature and air pollutant concentration as independent variables. Still, more needs to be studied about the co-occurrence of climate and air pollution. The co-occurrence of extreme climate and air pollution events is likely to become an increasing health risk in China and many parts of the world as climate changes. Climate change can interact with air pollution exposure to amplify risks to human health. Challenges and opportunities to assess the combined effect of climate variables and air pollution on human health are discussed in this review. Implications from epidemiological studies for implementing coordinated measures and policies for addressing climate change and air pollution will be critical areas of future work.

Short-term joint effects of ambient PM2.5 and O3 on mortality in Beijing, China

Introduction

In recent years, air pollution caused by co-occurring PM2.5 and O3, named combined air pollution (CAP), has been observed in Beijing, China, although the health effects of CAP on population mortality are unclear.

Methods

We employed Poisson generalized additive models (GAMs) to evaluate the individual and joint effects of PM2.5 and O3 on mortality (nonaccidental, respiratory, and cardiovascular mortality) in Beijing, China, during the whole period (2014-2016) and the CAP period. Adverse health effects were assessed for percentage increases (%) in the three mortality categories with each 10-μg/m3 increase in PM2.5 and O3. The cumulative risk index (CRI) was adopted as a novel approach to quantify the joint effects.

Results

The results suggested that both PM2.5 and O3 exhibited the greatest individual effects on the three mortality categories with cumulative lag day 01. Increases in the nonaccidental, cardiovascular, and respiratory mortality categories were 0.32%, 0.36%, and 0.43% for PM2.5 (lag day 01) and 0.22%, 0.37%, and 0.25% for O3 (lag day 01), respectively. There were remarkably synergistic interactions between PM2.5 and O3 on the three mortality categories. The study showed that the combined effects of PM2.5 and O3 on nonaccidental, cardiovascular, and respiratory mortality were 0.34%, 0.43%, and 0.46%, respectively, during the whole period and 0.58%, 0.79%, and 0.75%, respectively, during the CAP period. Our findings suggest that combined exposure to PM2.5 and O3, particularly during CAP periods, could further exacerbate their single-pollutant health risks.

Conclusion

These findings provide essential scientific evidence for the possible creation and implementation of environmental protection strategies by policymakers.

Independent risk evaluation associated with short-term black carbon exposure on mortality in two megacities of Yangtze River Delta, China

The adverse health effects of PM_2.5 have been well demonstrated by many studies. However, as a component of PM_2.5, evidence on the mortality risk of black carbon (BC) is still limited. In this study, based on the data of daily mean PM_2.5 concentration, BC concentration, meteorological factors, total non-accidental (all-cause) and cardiovascular mortality in Shanghai and Nanjing during 2015-2016, a semi-parameter generalized additive model (GAM) in the time series and the constituent residual approach were employed to explore the exposure-response relationship between BC and human mortality in these two megacities of Yangtze River Delta, China. The main objective was to separate the health effects of BC from total PM_2.5, and compare the difference of mortality ER related to BC original concentration and adjusted concentration after controlling PM_2.5. Results showed that there were all significantly associated with daily mortality for PM_2.5 and BC. The percentage excess risk (ER) increases in all-cause and cardiovascular categories were 1.68 % (95 % s 1.28, 2.08) and 2.16 % (95 % CI: 1.54, 2.79) with 1 μg/m³ increment in original BC concentration in Shanghai. And the ER in Nanjing was smaller than that in Shanghai. After eliminating PM_2.5 confounding effects by a constituent residual approach, the BC residual concentration still had a strong significant ER. The ER for BC residual in Shanghai got an obvious increase, and ER of the cardiovascular mortality for all, females and males increased by 0.55 %, 1.46 % and 0.62 %, respectively, while the ER in Nanjing decreased slightly. It also revealed that females were more sensitive to the health risk associated with short-term BC exposure than males. Our findings provide additional important evidence and ER for mortality related to independent BC exposure. Therefore, BC emission reduction should be paid more attention in air pollution control strategies to reduce BC-related health burdens.

Acute effect of fine particulate matter and respiratory mortality in Changsha, China: a time-series analysis

Background

Previous studies have confirmed that exposure to fine particulate matter (PM_2.5) is associated with respiratory disease mortality. However, due to the differences in PM_2.5 concentration, composition and population susceptibility within different regions, the estimates of the association between PM_2.5 concentration and mortality are different. Moreover, few studies have examined the potential hazard of excessive PM_2.5 exposure in terms of respiratory disease mortality.

Methods

Daily recorded data on meteorological indices, environmental pollutants, and causes of death data in Changsha from January 2015 to December 2018 were obtained. The potential relationship between PM_2.5 concentrations and respiratory disease mortality was determined using distributed lag nonlinear model (DLNM), which includes the relative risk (RR) and cumulative relative risk (CRR) of the lagged effect. The synergistic effects of other air pollutants were also considered.

Results

A total of 8,825 cases of respiratory disease mortality occurred in Changsha between 2015 and 2018. The acute effect of PM_2.5 concentration was associated with an increased risk of respiratory disease mortality. Regarding the lag specific effect, a 10 μg/m³ increase in PM_2.5 concentration on respiratory disease mortality was statistically significant at lag day 0 and lag day 7 with a relative risk of 1.019 (95% CI 1.007- 1.031) and 1.013(95%CI: 1.002-1.024). As for the cumulative lag effect, a 4-day moving average of PM_2.5 concentrations was significantly associated with a cumulative relative risk of 1.027 (95%CI: 1.011-1.031). The single-day lag effect and cumulative 4-day lag effect for male individuals were more significant than those observed in females. The effect of PM_2.5 concentrations and respiratory disease mortality remained statistically significant in the multi-pollutant models (SO₂, NO₂, and O₃). A higher risk was observed in the cold season than in the warm season.

Conclusions

Our findings show a potential association between exposure to PM_2.5 concentration and respiratory disease mortality in Changsha, with male individuals observed to have particularly higher risk.

Visits to the accident and emergency department in hot season of a city with subtropical climate: association with heat stress and related meteorological variables

BACKGROUND

Literature reporting the association between heat stress defined by universal thermal climate index (UTCI) and emergency department visits is mainly conducted in Europe. This study aimed to investigate the association between heat stress, as defined by the UTCI, and visits to the accident and emergency department (AED) in Hong Kong, which represents a subtropical climate region.

METHODS

A retrospective study involving 13,438,846 AED visits in the public sector from May 2000 to September 2016, excluding 2003 and 2009, was conducted in Hong Kong. Age-sex-specific ANCOVA models of daily AED rates on heat stress and prolonged heat stress, adjusting for air quality, prolonged poor air quality, typhoon, rainstorm, year, day of the week, public holiday, summer vacation, and fee charging, were used.

RESULTS

On a day with strong heat stress (32.1 °C ≤ UTCI ≤ 38.0 °C), the AED visit rate (per 100,000) increased by 0.9 (95% CI: 0.5, 1.3) and 1.7 (95% CI: 1.3, 2.1) for females and males aged 19-64 and 4.1 (95% CI: 2.7, 5.4) and 4.1 (95% CI: 2.6, 5.6) for females and males aged ≥ 65, while keeping other variables constant. On a day with very strong heat stress (38.1 °C ≤ UTCI ≤ 46.0 °C), the corresponding rates increased by 0.6 (95% CI: 0.1, 1.2), 2.2 (95% CI: 1.7, 2.7), 4.9 (95% CI: 3.1, 6.7), and 4.7 (95% CI: 2.7, 6.6), respectively. The effect size of heat stress associated with AED visit rates was negligible among those aged ≤ 18. Heat stress showed the greatest effect size for males aged 19-64 among all subgroups.

CONCLUSION

Biothermal condition from heat stress was associated with the health of the citizens in a city with a subtropical climate and reflected in the increase of daily AED visit. Public health recommendations have been made accordingly for the prevention of heat-related AED visits.

Modification effects of ambient temperature on ozone-mortality relationships in Chengdu, China

A multitude of epidemiological studies have demonstrated that both ambient temperatures and air pollution are closely related to health outcomes. However, whether temperature has modification effects on the association between ozone and health outcomes is still debated. In this study, three parallel time-series Poisson generalized additive models (GAMs) were used to examine the effects of modifying ambient temperatures on the association between ozone and mortality (including non-accidental, respiratory, and cardiovascular mortality) in Chengdu, China, from 2014 to 2016. The results confirmed that the ambient high temperatures strongly amplified the adverse effects of ozone on human mortality; specifically, the ozone effects were most pronounced at > 28 °C. Without temperature stratification conditions, a 10-μg/m³ increase in the maximum 8-h average ozone (O_3-8hmax) level at lag01 was associated with increases of 0.40% (95% confidence interval [CI] 0.15%, 0.65%), 0.61% (95% CI 0.27%, 0.95%), and 0.69% (95% CI 0.34%, 1.04%) in non-accidental, respiratory, and cardiovascular mortality, respectively. On days during which the temperature exceeded 28 °C, a 10-μg/m³ increase in O_3-8hmax led to increases of 2.22% (95% CI 1.21%, 3.23%), 2.67% (95% CI 0.57%, 4.76%), and 4.13% (95% CI 2.34%, 5.92%) in non-accidental, respiratory, and cardiovascular mortality, respectively. Our findings validated that high temperature could further aggravate the health risks of O_3-8hmax; thus, mitigating ozone exposure will be brought into the limelight especially under the context of changing climate.