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Nitryl chloride (ClNO2) is a dominant source of chlorine radical in polluted environment, and can significantly affect the atmospheric oxidative chemistry. However, the abundance of ClNO2 and its exact role are not fully understood under different environmental conditions. During the summer of 2014, we deployed a chemical ionization mass spectrometer to measure ClNO2 and dinitrogen pentoxide (N2O5) at a rural site in the polluted North China Plain. Elevated mixing ratios of ClNO2 (> 350 pptv) were observed at most of the nights with low levels of N2O5 (< 200 pptv). The highest ClNO2 mixing ratio of 2070 pptv (1 min average) was observed in a plume from a megacity (Tianjin), and was characterized with a faster N2O5 heterogeneous loss rate and ClNO2 production rate compared to average conditions. The abundant ClNO2 concentration kept increasing even after sunrise, and reached a peak 4 h later. Such highly sustained ClNO2 peaks after sunrise are discrepant from the previously observed typical diurnal pattern. Meteorological and chemical analysis shows that the sustained ClNO2 morning peaks are caused by significant ClNO2 production in the residual layer at night followed by downward mixing after breakup of the nocturnal inversion layer in the morning. We estimated that ~1.7-4.0 ppbv of ClNO2 would exist in the residual layer in order to maintain the observed morning ClNO2 peaks at the surface site. Observation-based box model analysis show that photolysis of ClNO2 produced chlorine radical with a rate up to 1.12 ppbv h-1, accounting for 10-30% of primary ROx production in the morning hours. The perturbation in total radical production leads to an increase of integrated daytime net ozone production by 3% (4.3 ppbv) on average, and with a larger increase of 13% (11 ppbv) in megacity outflow that was characterized with higher ClNO2 and a relatively lower oxygenated hydrocarbon (OVOC) to non-methane hydrocarbon (NMHC) ratio. [ABSTRACT FROM AUTHOR]

Numerous studies have described the adverse associations between particle mass and respiratory health. The aim of the study was to analyze the associations of particle properties, especially size-segregated particle number concentrations (PNC), and respiratory mortality in Beijing, P.R. China. We gathered daily values of respiratory mortality and air pollution data of the Beijing urban area. Generalized additive models were used to estimate the associations. Single pollutant models showed that delayed concentrations of SO2, total PNCs, and PNC of 300–1000 nm were adversely associated with total respiratory mortality. There was an indication that adverse health effects of PNCs might be stronger for stagnant air masses. Two-pollutant models verified the independence of associations of total PNCs of other pollutants (SO2, NO2, and PM10). In conclusion, particle number concentrations, especially accumulation mode particles, might be factors influencing the adverse associations between particulate matter and respiratory health. [ABSTRACT FROM AUTHOR]

This study discusses the evolution of particle number size distribution during episodes of heavy pollution and new particle formation in the urban atmosphere of Beijing to quantify the effects of dynamic processes (coagulation and condensation) on the particle number size distribution. During a heavy-pollution event, an extremely low number concentration of 3-10 nm particles (on average 46 cm) was observed. This is because nucleation-mode particles were easily removed by strong coagulational scavenging of larger particles under this condition. In addition, a large condensation sink (on average 0.13 s) restrained nucleation, which is one of the major sources of nucleation-mode particles. Conversely, during a new-particle formation event, the small condensation sink (0.01 s) of precursor facilitated nucleation. At the same time, preexisting particles had little ability to scavenge newly formed particles (around 1 nm) and allowed them to grow to a detectable size (larger than 3 nm currently). We suggest that the effects of dynamic processes (coagulation and condensation) on particle size distribution should be stressed under some extreme conditions of the relatively polluted urban atmosphere in addition to traffic and meteorological factors. [ABSTRACT FROM AUTHOR]

BACKGROUND: The link between concentrations of particulate matter (PM) and respiratory morbidity has been investigated in numerous studies. OBJECTIVES: The aim of this study was to analyze the role of different particle size fractions with respect to respiratory health in Beijing, China. METHODS: Data on particle size distributions from 3 nm to 1 μm; PM10 (PM ≤ 10 μm), nitrogen dioxide (NO2), and sulfur dioxide concentrations; and meteorologic variables were collected daily from March 2004 to December 2006. Concurrently, daily counts of emergency room visits (ERV) for respiratory diseases were obtained from the Peking University Third Hospital. We estimated pollutant effects in single- and two-pollutant generalized additive models, controlling for meteorologic and other time-varying covariates. Time-delayed associations were estimated using polynomial distributed lag, cumulative effects, and single lag models. RESULTS: Associations of respiratory ERV with NO2 concentrations and 100-1,000 nm particle number or surface area concentrations were of similar magnitude-that is, approximately 5% increase in respiratory ERV with an interquartile range increase in air pollution concentration. In general, particles < 50 nm were not positively associated with ERV, whereas particles 50-100 nm were adversely associated with respiratory ERV, both being fractions of ultrafine particles. Effect estimates from two-pollutant models were most consistent for NO2. CONCLUSIONS: Present levels of air pollution in Beijing were adversely associated with respiratory ERV. NO2 concentrations seemed to be a better surrogate for evaluating overall respiratory health effects of ambient air pollution than PM10 or particle number concentrations in Beijing. [ABSTRACT FROM AUTHOR]

Background: Associations between air temperature and mortality have been consistently observed in Europe and the United States; however, there is a lack of studies for Asian countries. Our study investigated the association between air temperature and cardio-respiratory mortality in the urban area of Beijing, China. Methods: Death counts for cardiovascular and respiratory diseases for adult residents (≥15 years), meteorological parameters and concentrations of particulate air pollution were obtained from January 2003 to August 2005. The effects of two-day and 15-day average temperatures were estimated by Poisson regression models, controlling for time trend, relative humidity and other confounders if necessary. Effects were explored for warm (April to September) and cold periods (October to March) separately. The lagged effects of daily temperature were investigated by polynomial distributed lag (PDL) models. Results: We observed a J-shaped exposure-response function only for 15-day average temperature and respiratory mortality in the warm period, with 21.3°C as the threshold temperature. All other exposure-response functions could be considered as linear. In the warm period, a 5°C increase of two-day average temperature was associated with a RR of 1.098 (95% confidence interval (95%CI): 1.057-1.140) for cardiovascular and 1.134 (95%CI: 1.050-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.040 (95%CI: 0.990-1.093) for cardiovascular mortality. In the cold period, a 5°C increase of two-day average temperature was associated with a RR of 1.149 (95%CI: 1.078-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.057 (95%CI: 1.022-1.094) for cardiovascular mortality. The effects remained robust after considering particles as additional confounders. Conclusions: Both increases and decreases in air temperature are associated with an increased risk of cardiovascular mortality. The effects of heat were immediate while the ones of cold became predominant with longer time lags. Increases in air temperature are also associated with an immediate increased risk of respiratory mortality. [ABSTRACT FROM AUTHOR]

In developing countries, aerosol particles damage the health of hundreds of millions of people. Migration from the country side to megacities increases emissions and exposure to particles. Some countries have started to limit emissions based on particulate mass, but this may increase particle number concentrations. In this study we discuss some earlier measurements carried out in the developing world and compare results from one-week measurement campaigns concerning the particle number size distribution and PM10 mass concentrations in New Delhi, India and Beijing, China. Our results show that submicron particle concentrations are high in both places. The average PM10 concentration was 360 μg/m3 in New Delhi and 120 μg/m3 in Beijing. The corresponding total particle number concentrations in the size range 3–800 nm were 63 000 cm−3 and 35 000 cm−3. Number and mass concentrations and their characteristics showed significantly different behaviour between these two locations, which stresses the importance of long-term simultaneous measurements of both quantities in different types of megacities. [ABSTRACT FROM AUTHOR]

Cooking emission is one of sources for ambient volatile organic compounds (VOCs), which is deleterious to air quality, climate and human health. These emissions are especially of great interest in large cities of East and Southeast Asia. We conducted a case study in which VOC emissions from kitchen extraction stacks have been sampled in total 57 times in the Megacity Shanghai. To obtain representative data, we sampled VOC emissions from kitchens, including restaurants of seven common cuisine types, canteens, and family kitchens. VOC species profiles and their chemical reactivities have been determined. The results showed that 51.26% ± 23.87% of alkane and 24.33 ± 11.69% of oxygenated VOCs (O-VOCs) dominate the VOC cooking emissions. Yet, the VOCs with the largest ozone formation potential (OFP) and secondary organic aerosol potential (SOAP) were from the alkene and aromatic categories, accounting for 6.8–97.0% and 73.8–98.0%, respectively. Barbequing has the most potential of harming people's heath due to its significant higher emissions of acetaldehyde, hexanal, and acrolein. Methodologies for calculating VOC emission factors ( EF ) for restaurants that take into account VOCs emitted per person ( EF person ), per kitchen stove ( EF kitchen stove ) and per hour ( EF hour ) are developed and discussed. Methodologies for deriving VOC emission inventories (S) from restaurants are further defined and discussed based on two categories: cuisine types ( S type ) and restaurant scales ( S scale ). The range of S type and S scale are 4124.33–7818.04 t/year and 1355.11–2402.21 t/year, respectively. We also found that S type and S scale for 100,000 people are 17.07–32.36 t/year and 5.61–9.95 t/year, respectively. Based on Environmental Kuznets Curve, the annual total amount of VOCs emissions from catering industry in different provinces in China was estimated, which was 5680.53 t/year, 6122.43 t/year, and 66,244.59 t/year for Shangdong and Guangdong provinces and whole China, respectively. Large and medium-scaled restaurants should be paid more attention with respect to regulation of VOCs. [ABSTRACT FROM AUTHOR]

Abstract: Background: Although short-term exposure to ambient particulate matter has increasingly been linked with cardiovascular diseases, it is not quite clear how physical characteristics of particles, such as particle size may be responsible for the association. This study aimed at investigating whether daily changes in number or mass concentrations of accurately size-segregated particles in the range of 3nm–10μm are associated with daily cardiovascular emergency room visits in Beijing, China. Methods: Cardiovascular emergency room visit counts, particle size distribution data, and meteorological data were collected from Mar. 2004 to Dec. 2006. Particle size distribution data was used to calculate particle number concentration in different size fractions, which were then converted to particle mass concentration assuming spherical particles. We applied a time-series analysis approach. We evaluated lagged associations between cardiovascular emergency room visits and particulate number and mass concentration using distributed lag non-linear models up to lag 10. We calculated percentage changes of cardiovascular emergency room visits, together with 95% confidence intervals (CI), in association with an interquartile range (IQR, difference between the third and first quartile) increase of 11-day or 2-day moving average number or mass concentration of particulate matter within each size fraction, assuming linear effects. We put interaction terms between season and 11-day or 2-day average particulate concentration in the models to estimate the modification of the particle effects by season. Results: We observed delayed associations between number concentration of ultrafine particles and cardiovascular emergency room visits, mainly from lag 4 to lag 10, mostly contributed by 10–30nm and 30–50nm particles. An IQR (9040cm−3) increase in 11-day average number concentration of ultrafine particles was associated with a 7.2% (1.1–13.7%) increase in total, and a 7.9% (0.5–15.9%) increase in severe cardiovascular emergency room visits. The delayed effects of particulate mass concentration were small. Regarding immediate effects, 2-day average number concentration of Aitken mode (30–100nm) particles had strongest effects. An IQR (2269cm−3) increase in 2-day average number concentration of 30–50nm particles led to a 2.4% (−1.5–6.5%) increase in total, and a 1.7% (−2.9–6.5%) increase in severe cardiovascular emergency room visits. The immediate effects of mass concentration came mainly from 1000–2500nm particles. An IQR (11.7μgm−3) increase in 2-day average mass concentration of 1000–2500nm particles led to an around 2.4% (0.4–4.4%) increase in total, and a 1.7% (−0.8–4.2%) increase in severe cardiovascular emergency room visits. The lagged effect curves of number and mass concentrations of 100–300nm particles or 300–1000nm particles were quite similar, indicating that using particulate number or mass concentrations seemed not to affect the cardiovascular effect (of particles within one size fraction). The effects of number concentration of ultrafine particles, sub-micrometer particles (3–1000nm) and 10–30nm particles were substantially higher in winter comparing with in summer. Conclusions: Elevated concentration levels of sub-micrometer particles were associated with increased cardiovascular morbidity. Ultrafine particles showed delayed effects, while accumulation mode (100–1000nm) particles showed immediate effects. Using number or mass concentrations did not affect the particle effects. [Copyright &y& Elsevier]

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm-3 and 1.62 ± 0.38 g cm-3 for PM1.8 and 1.73 ± 0.14 g cm-3 and 1.67 ± 0.37 g cm-3 for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm-3 at the size of 0.1 μm to above 2.0 g cm-3 in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 μm during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles. [ABSTRACT FROM AUTHOR]

Abstract: Background: While the link between particulate matter and cardiovascular mortality is well established, it is not fully investigated and understood which properties of the aerosol might be responsible for the health effects, especially in polluted mega-city areas. Objectives: Our goal was to explore the association between daily cardiovascular mortality and different particle metrics in the sub-micrometer range in Beijing, China. Methods: We obtained daily counts of cause-specific cardiovascular deaths in the Beijing urban area for the period March 2004 to August 2005. Concurrently, continuous measurements of particle number size distributions were performed. Particle number concentrations (NC) between 0.003μm and 0.8μm were converted to particle mass and surface area concentrations assuming spherical particles. Semi-parametric Poisson regression models adjusting for trend, seasonality, day of the week, and meteorology were used to estimate immediate, delayed and cumulative particle effects. Additionally, effect modification by air mass origin was investigated. Results: We observed associations between daily cardiovascular mortality and particle NC for a 2-days delay. Moreover, nearly all particle metrics showed 2-days delayed associations with ischemic heart disease mortality. The strongest association was found for particle NC in the size range 0.03–0.1μm (7.1% increase in daily mortality with a 95%-confidence interval of 2.9%–11.5%, per an increase of 6250particles/cm3). Results for surface and mass concentrations with a lag of two days indicated effect modification by air mass origin, whereas effects of particle NC were not modified. Conclusions: Results show an elevated risk of cardiovascular mortality in Beijing from short-term exposure to particulate air pollution in the sub-micrometer range. Results also indicate that locally produced smaller particles and regionally transported particles may exhibit different effects in Beijing. [Copyright &y& Elsevier]

Two-year measurements of particle number size distribution (3nm–10μm) were conducted in Beijing, China since March 2004. Their seasonal, weekly and diurnal variations and dependencies on meteorological parameters were investigated. The annual average particle number concentrations of the nucleation mode (3–20nm), Aitken mode (20–100nm), and accumulation mode (0.1–1μm) are 9000cm−3, 15,900cm−3, and 7800cm−3, respectively. Particle number concentrations in Beijing are generally higher than that in cities of developed countries, especially for the accumulation mode particles. Both the highest total particle number concentration and the lowest volume concentration occurred in spring due to the frequent nucleation events. However, the minimum particle number concentration was observed in summer, and the maximum volume concentration in fall. The diurnal variation of the nucleation mode particles was mainly influenced by nucleation events, primarily in spring and winter. The diurnal variation of number concentration of the Aitken mode particles closely correlates with the traffic densities in all the four seasons. At the same time, obvious contribution of the growth of the nucleation mode to the number concentration of the Aitken mode particle has been also found in spring, summer, and fall. Significant differences in diurnal patterns of particle number concentrations between workdays and weekends are not observed in Beijing. Local wind speed plays an important role in shaping the particle number size distributions in the urban area of Beijing. With increasing wind speed, the nucleation and coarse mode particle number concentrations increase, while the number concentrations of the Aitken mode and accumulation mode particles decrease. A “U-shape relationship” between the total particle volume concentration and wind speed is observed. Frequently low wind speed (lower than 3m s−1) in Beijing is one of key factors leading to the poor air quality and low visibility. [Copyright &y& Elsevier]

Continuous measurements of aerosol number size distribution in the range of 3nm–10μm were performed in Pearl River Delta (PRD), China. These measurements were made during the period of 3 October to 5 November in 2004 at rural/coastal site, Xinken (22°37′N, 113°35′E, 6m above sea level), in the south suburb of Guangzhou City (22°37′N, 113°35′E, 6m above sea level), using a Twin Differential Mobility Particle Sizer (TDMPS) combined with an Aerodynamic Particle Sizer (APS). The aerosol particles at Xinken were divided into four groups according to the observation results: nucleation mode particles (3–30nm), Aitken mode particles (30–130nm), accumulation mode particles (130–1000nm) and coarse mode particles (1–10μm). Concentrations of nucleation mode, Aitken mode and accumulation mode particles were observed in the same order of magnitude (about 10,000cm−3), among which the concentration of Aitken mode particle was the highest. The Aitken mode particles usually had two peaks: the morning peak may be caused by the land–sea circulation, which is proven to be important for transporting aged aerosols back to the sampling site, while the noon peak was ascribed to the condensational growth of new particles. New particle formation events were found on 7 days of 27 days, the new particle growth rates ranged from 2.2 to 19.8nmh−1 and the formation rates ranged from 0.5 to 5.2cm−3 s−1, both of them were in the range of typical observed formation rates (0.01–10cm−3 s−1) and typical particle growth rates (1–20nmh−1). The sustained growth of the new particles for several hours under steady northeast wind indicated that the new particle formation events may occur in a large homogeneous air mass. [Copyright &y& Elsevier]

Though the importance of HONO as an OH precursor has been recognized for years, its chemical formation pathway is still not well understood. This inhibited the simulations of HONO and observation-based formation rates provided an alternative for the air quality models. However, HONO formation rate derived from certain period may be significantly influenced by uncertainties in transport and emission processes. In this study the use of large sample and scaling methods were recommended in the calculation of HONO formation rate. During the Program of Regional Integrated Experiments of Air Quality over Pear River Delta (PRIDE-PRD2004), good correlations between HONO and were found supporting the involvement of in HONO formation. An average -to-HONO nighttime conversion rate of was derived at a non-urban site Xinken. This conversion rate was comparable to other field measurements and could not be explained by gas phase reactions only. If assumed that HONO was formed only on the ground surface, the observed conversion rate could be explained by the reactions of on ground surfaces only if three deposited lead to one HONO released. The emission factor of HONO and its sampling interferences during the measurements were also evaluated in this article. [Copyright &y& Elsevier]

The oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO 2 ) and organic peroxy radicals (RO 2 ) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area. Radical and trace gas concentrations were measured, allowing for calculating the turnover rates of gas-phase radical reactions. Therefore, the importance of heterogeneous HO 2 uptake on aerosol could be experimentally determined. HO 2 uptake could have suppressed ozone formation at that time because of the competition with gas-phase reactions that produce ozone. The successful reduction of the aerosol load in the North China Plain in the last years could have led to a significant decrease of HO 2 loss on particles, so that ozone-forming reactions could have gained importance in the last years. However, the analysis of the measured radical budget in this campaign shows that HO 2 aerosol uptake did not impact radical chemistry for chemical conditions in 2014. Therefore, reduced HO 2 uptake on aerosol since then is likely not the reason for the increasing number of ozone pollution events in the North China Plain, contradicting conclusions made from model calculations reported in the literature.

As nitrous acid (HONO) photolysis is an important source of hydroxyl radical (OH), apportionment of the ambient HONO sources is necessary to better understand atmospheric oxidation. Based on the data HONO-related species and various parameters measured during the one-month campaign at Wangdu (a rural site in North China plain) in summer 2014, a box model was adopted with input of current literature parametrizations for various HONO sources (nitrogen dioxide heterogeneous conversion, photoenhanced conversion, photolysis of adsorbed nitric acid and particulate nitrate, acid displacement, and soil emission) to reveal the relative importance of each source at the rural site. The simulation results reproduced the observed HONO production rates during noontime in general but with large uncertainty from both the production and destruction terms. NO 2 photoenhanced conversion and photolysis of particulate nitrate were found to be the two major mechanisms with large potential of HONO formation but the associated uncertainty may reduce their importance to be nearly negligible. Soil nitrite was found to be an important HONO source during fertilization periods, accounted for (80 ± 6)% of simulation HONO during noontime. For some episodes of the biomass burning, only the NO 2 heterogeneous conversion to HONO was promoted significantly. In summary, the study of the HONO budget is still far from closed, which would require a significant effort on both the accurate measurement of HONO and the determination of related kinetic parameters for its production pathways.

Large quantities of mineral dust particles are frequently ejected into the atmosphere through the action of wind. The surface of dust particles acts as a sink for many gases, such as sulfur dioxide. It is well known that under most conditions, sulfur dioxide reacts on dust particle surfaces, leading to the production of sulfate ions. In this report, for specific atmospheric conditions, we provide evidence for an alternate pathway in which a series of reactions under solar UV light produces first gaseous sulfuric acid as an intermediate product before surface-bound sulfate. Metal oxides present in mineral dust act as atmospheric photocatalysts promoting the formation of gaseous OH radicals, which initiate the conversion of SO(2) to H(2)SO(4) in the vicinity of dust particles. Under low dust conditions, this process may lead to nucleation events in the atmosphere. The laboratory findings are supported by recent field observations near Beijing, China, and Lyon, France.

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm(-3) and 1.62 ± 0.38 g cm(-3) for PM(1.8) and 1.73 ± 0.14 g cm(-3) and 1.67 ± 0.37 g cm(-3) for PM(10). Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 μm to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 μm during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.

Background: Associations between air temperature and mortality have been consistently observed in Europe and the United States; however, there is a lack of studies for Asian countries. Our study investigated the association between air temperature and cardio-respiratory mortality in the urban area of Beijing, China., Methods: Death counts for cardiovascular and respiratory diseases for adult residents (≥15 years), meteorological parameters and concentrations of particulate air pollution were obtained from January 2003 to August 2005. The effects of two-day and 15-day average temperatures were estimated by Poisson regression models, controlling for time trend, relative humidity and other confounders if necessary. Effects were explored for warm (April to September) and cold periods (October to March) separately. The lagged effects of daily temperature were investigated by polynomial distributed lag (PDL) models., Results: We observed a J-shaped exposure-response function only for 15-day average temperature and respiratory mortality in the warm period, with 21.3°C as the threshold temperature. All other exposure-response functions could be considered as linear. In the warm period, a 5°C increase of two-day average temperature was associated with a RR of 1.098 (95% confidence interval (95%CI): 1.057-1.140) for cardiovascular and 1.134 (95%CI: 1.050-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.040 (95%CI: 0.990-1.093) for cardiovascular mortality. In the cold period, a 5°C increase of two-day average temperature was associated with a RR of 1.149 (95%CI: 1.078-1.224) for respiratory mortality; a 5°C decrease of 15-day average temperature was associated with a RR of 1.057 (95%CI: 1.022-1.094) for cardiovascular mortality. The effects remained robust after considering particles as additional confounders., Conclusions: Both increases and decreases in air temperature are associated with an increased risk of cardiovascular mortality. The effects of heat were immediate while the ones of cold became predominant with longer time lags. Increases in air temperature are also associated with an immediate increased risk of respiratory mortality.