[Stimulus and reward information encoded by population neurons in the primate prefrontal cortex and striatum].

It has been reported that single-unit activity in the prefrontal cortex (PFC) and striatum represented visual stimulus and reward information. But how to encode these pieces of information is quite complex from the view of single-neuron activity. Different neurons represented stimulus or reward information in different task epochs with increasing or decreasing their activities relative to their baseline firing rates. The present paper was aimed to study whether population neurons in the two brain areas could stably encode task-relevant parameters in a whole trial period. We recorded single-unit activities in the lateral PFC (LPFC) and striatum while the monkey was performing a stimulus- reward prediction task, and analyzed the neuronal activities by the method of a multi-variable regression model and the linear support vector machine. The results showed that, although proportions of task-related neurons in the two areas varied largely in the whole trial period, LPFC population neurons encoded reward and stimulus information stably and reliably. Population neurons in the striatum encoded only reward information, not stimulus information. A group of neurons in the two areas represented combined information of stimulus and reward. Further analysis showed that LPFC neurons encoded reward information for a group of relevant stimuli, while striatal neurons encoded reward information for a specific stimulus. These results suggest that both LPFC and striatal population neurons are able to stably represent task-relevant information, but from different aspects of the task. The different strategies to encode information in the LPFC and striatum suggest their different contributions in reward-based decision making.

[Reward information encoded by power of local field potentials in the primate prefrontal cortex and striatum].

Prefrontal cortex and striatum are two major areas in the brain. Some research reports suggest that both areas are involved in many advanced cognitive processes, such as learning and memory, reward processing, and behavioral decision. Single-unit recording experiments have found that neurons in the prefrontal cortex and striatum can represent reward information, but it remains elusive whether and how local field potentials (LFPs) in the two areas encode reward information. To investigate these issues, we recorded LFPs simultaneously in the prefrontal cortex and striatum of two monkeys by performing a reward prediction task (a large amount reward vs a small amount reward). Recorded LFP signals were transformed from the time domain to the time and frequency domain using the method of short-time Fourier transform (STFT). We calculated the power in each frequency and time, and examined whether they were different in the two reward conditions. The results showed that power of LFPs in both the prefrontal cortex and striatum distinguished one reward condition from the other one. And the power in small reward trials was greater than that in large reward trials. Furthermore, it was found that the LFPs better encoded reward information in the beta band (14-30 Hz) rather than other frequency bands. Our results suggest that the LFPs in the prefrontal cortex and striatum effectively represent reward information, which would help to further understand functional roles of LFPs in reward processing.

Relationship between ambient fine particles and ventricular repolarization changes and heart rate variability of elderly people with heart disease in Beijing, China.

OBJECTIVE: To explore the effects of particulate matters less than 2.5 µm in aerodynamic diameter (PM2.5) on heart repolarization/depolarization and heart rate variability (HRV). METHODS: We conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram (ECG) indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PM2.5 and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology. RESULTS: Significant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.5 on HRV was on lag 1 day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension. CONCLUSION: This study showed ambient PM2.5 could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5.

[Association between ambient PM10/PM2.5 levels and population mortality of circulatory diseases: a case-crossover study in Beijing].

OBJECTIVE: To explore the association between levels of ambient particulate matters (PM10 and PM2.5) and population mortality of circulatory diseases (ICD10: I00~I99) in Beijing. METHODS: The daily data of ambient PM2.5 levels were monitored by the research team in Peking University from Jan. 1, 2007 to Dec. 31, 2008, and the corresponding meteorological and other air quality data (PM10, SO2 and NO2) were collected from National Meteorological Information Center (NMIC) of China and Beijing Environmental Monitoring Center. The data of daily death for the circulatory diseases were collected from the local center for Disease Control and Prevention of Haidian District in Beijing. The symmetric bidirectional case-crossover design and conditional logistic regression model were used for the data analysis. The cases were stratified by gender, age and seasons. The lagged effect was analyzed and the related confounders from meteorological factors and other air pollutants were adjusted. RESULTS: For a 10 µg/m(3) increase of the ambient concentration of PM2.5, the corresponding increase of daily mortality of the circulatory diseases, cardiovascular diseases and cerebrovascular diseases was 0.78% (95% CI: 0.07% to 1.49%), 0.85% (95% CI: -0.28% to 1.99%), and 0.75% (95% CI: -0.17% to 1.68%), respectively, for a 10 µg/m(3) increase of the ambient concentration of PM10, the corresponding increase of daily mortality of the circulatory diseases, cardiovascular diseases and cerebrovascular diseases was 0.36% (95% CI: -0.07% to 0.78%), 0.63% (95% CI: -0.02% to 1.28%), and 0.33% (95% CI: -0.26% to 0.92%),respectively. The significant positive associations were observed statistically between PM2.5 and the circulatory diseases (P<0.05). The association between ambient PMs and the population mortality was stronger in "warm season (April to September)" than in "cool season (October to the next March)" in Beijing (P<0.05). CONCLUSION: The elevated levels of ambient PM2.5 and PM10 were positively associated with the increase of the population mortality of the circulatory diseases, and the association is stronger in warm season, and the adverse effect of PM2.5 is greater than that of PM10.

[Evaluation of excess mortality caused by PM2.5 in four typical Chinese big cities].

OBJECTIVE: To evaluate the adverse effects of particulate matter ≤ 2.5 µm in aerodynamic diameter (PM2.5) on public health in four typical cities: Beijing, Shanghai, Guangzhou and Xi'an. METHODS: Daily health and meteorological data (including ambient temperature and relative humidity) were collected in the past several years. For the relative risk of PM2.5 effects on mortalities, generalized additive model (GAM) was used to obtain the exposure-response coefficients between PM2.5 and non-accidental mortalities after controlling time trend, week effects and meteorological factors. Then excess mortalities were calculated according to coefficients, health data and air pollution level. RESULTS: The relative risks of PM2.5 effects on mortalities were 1.0027(1.0010-1.0044), 1.0020 (1.0007-1.0033) , 1.0056 (1.0022-1.0091), 1.0036 (1.0011-1.0061) for Beijing, Xi'an, Shanghai, Guangzhou respectively. Compared with relative risks in northern cities (Beijing and Xi'an), relative risks in southern cities (Shanghai and Guangzhou) were higher. The numbers of excess mortalities caused by PM2.5 in Beijing, Shanghai, Guangzhou, Xi'an were 2349, 2980, 1715, 726 and accounted for 1.9%, 1.6%, 2.2% and 1.6% of the total death number in 2010 respectively. CONCLUSIONS: Although relative health risks caused by PM2.5 vary geographically for urban residents, public health is endangered. More efforts should be devoted to reducing PM2.5 pollution.

[Preliminary study of source apportionment of PM10 and PM2.5 in three cities of China during spring].

OBJECTIVE: To study source apportionment of atmospheric PM10 (particle matter ≤ 10 µm in aerodynamic diameter) and PM2.5 (particle matter ≤ 2.5 µm in aerodynamic diameter) in Beijing,Urumqi and Qingdao, China. METHODS: The atmospheric particle samples of PM10 and PM2.5 collected from Beijing between May 17th and June 18th, 2005, from Urumqi between April 20th and June 1st, 2006 and from Qingdao between April 4th and May 15th, 2005, were detected to trace the source apportionment by factor analysis and enrichment factor methods. RESULTS: In Beijing, the source apportionment results derived from factor analysis model for PM10 were construction dust and soil sand dust (contributing rate of variance at 45.35%), industry dust, coal-combusted smoke and vehicle emissions (contributing rate at 31.83%), and biomass burning dust (13.57%). The main pollution element was Pb, while the content (median (minimum value-maximum value)was 0.216 (0.040-0.795) µg/m(3)) . As for PM2.5, the sources were construction dust and soil sand dust (38.86%), industry dust, coal-combusted smoke and vehicle emissions (25.73%), biomass burning dust (13.10%) and burning oil dust (11.92%). The main pollution element was Zn (0.365(0.126-0.808) µg/m(3)).In Urumqi, source apportionment results for PM10 were soil sand dust and coal-combusted dust(49.75%), industry dust, vehicle emissions and secondary particles dust (30.65%). The main characteristic pollution element was Cd (0.463(0.033-1.351) ng/m(3)). As for PM2.5, the sources were soil sand dust and coal-combusted dust (43.26%), secondary particles dust (22.29%), industry dust and vehicle emissions (20.50%). The main characteristic pollution element was As (14.599 (1.696-36.741) µg/m(3)).In Qingdao, source apportionment results for PM10 were construction dust (30.91%), vehicle emissions and industry dust (29.65%) and secondary particles dust (28.99%). The main characteristic pollution element was Pb (64.071 (5.846-346.831) µg/m(3)). As for PM2.5, the sources were secondary particles dust, industry dust and vehicle emissions (49.82%) and construction dust (33.71%). The main characteristic pollution element was Pb(57.340 (5.004-241.559) µg/m(3)).Enrichment factors of Zn, Pb, As and Cd in PM2.5 were higher than those in PM10 both in Beijing and Urumqi. CONCLUSION: The major sources of the atmospheric particles PM10 and PM2.5 in Beijing were cement dust from construction sites and sand dust from soil; while the major sources of those in Urumqi were pollution by smoke and sand dust from burning coal. The major sources of the atmospheric particles PM10 in Qingdao were cement dust from construction sites; however, the major sources of PM2.5 there were secondary particles dust, industry dust and vehicle emissions. According to our study, the heavy metal elements were likely to gather in PM2.5.

Associations between size-segregated particle number concentrations and respiratory mortality in Beijing, China.

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 SO(2), 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 (SO(2), NO(2), and PM(10)). In conclusion, particle number concentrations, especially accumulation mode particles, might be factors influencing the adverse associations between particulate matter and respiratory health.

[Relationship between daily mean temperature and emergency department visits for respiratory diseases: a time-series analysis].

OBJECTIVE: To quantitatively evaluate the influences of daily mean air temperature (DMT) on Emergency Department Visits (EDVs) for the respiratory diseases. METHODS: The EDV data from medical records for respiratory diseases in Peking University Third Hospital between January 2004 and June 2009 were collected. The data of the air pollutants (SO(2), NO(2) and PM(10)) and meteorological factors at the same time periods were also collected from the local authorities of Beijing. Time-series analysis and generalized additive models (GAM) were used to explore the exposurrre-response relationship between DMT and EDVs for respiratory diseases. RESULTS: A total of 35 073 patients [males 14 707(41.93%,14 707/35 073), females 19 122(54.52%,19 122/35 073) and gender missing 1 244(3.55%, 1 244/35 073)] EDVs for respiratory diseases were included. The relationship between DMT and EDVs for the respiratory diseases was mainly of "V" shape, the optimum temperature(OT) was about 4 °C and the effect of DMT was significant with a 0-3 day lag structure for most of the models. When DMT≤OT, each 1°C decrease in DMT corresponded to 3.75% (95% CI of RR: 0.938 3-0.965 3), 3.10% (95% CI of RR:0.949 2-0.989 1), 4.09% (95% CI of RR:0.940 7-0.977 8) increase of EDVs for the overall, male, and female, respectively. When DMT>OT, the value caused by each increase in 1°C in DMT was 1.54% (95% CI of RR:1.006 6-1.024 3), 1.80% (95% CI of RR:1.005 3-1.030 9), and 1.51 (95% CI of RR:1.003 2- 1.027 2), respectively. The effect was statistically significant within the 0-3 day lag. When DMT≤OT, the effect was stronger for the older people, while the effect was strongest for the 45-59 years old people. CONCLUSION: The relationship between DMT and EDVs for respiratory diseases is mainly of "V" type, with an optimum temperature of 4 °C.Both DMT decrease when DMT≤OT and increase when DMT>OT correspond to different increase of EDVs for respiratory diseases. Low DMT has stronger effect than high DMT. Different age group and gender have different effects.

[Time-series analysis on relationship between air pollution and mortality from circulatory system diseases among registered residents in Chaoyang district of Beijing].

OBJECTIVE: This study aims to investigate relationship between daily concentration of PM(10), SO(2), NO(2) and daily mortality due to circulatory system diseases in Chaoyang district, Beijing. METHODS: The time-series data of daily mortality from circulatory system diseases of registered residents in Chaoyang were obtained from Chaoyang District Center for Disease Control and Prevention. The daily concentration of sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)), and particulate matter (PM(10)) were collected from Beijing Municipal Environmental Monitoring Center. And the routine monitoring meteorological data were collected from Beijing Meteorological Bureau, including daily mean temperature and daily mean relative humidity. The time-series analysis was then conducted to determine the relationship of mortality from circulatory system diseases with daily concentrations of SO(2), NO(2) and PM(10) by using Poisson regression with generalized additive model (GAM). RESULTS: During January 2004 to September 2008, the cumulative death number from circulatory system diseases of registered residents in Chaoyang district of Beijing was 19 241, the daily average concentration of SO(2), NO(2), PM(10) was 48.7, 63.9, 146.1 µg/m(3), respectively. The single pollutant model showed an increase of daily concentration of PM(10), SO(2) and NO(2) by 10 µg/m(3) will augment the mortality from circulatory system diseases by 0.20% (95%CI: 0.01% - 0.39%), 0.36% (95%CI: -0.13% - 0.85%) and 0.30% (95%CI: -0.34% - 0.94%), respectively. In the multiple air pollutants models, combinatorial effects of PM(10) and SO(2) still positively correlated with increased mortality from circulatory system diseases (P < 0.05), whereas changes of the concentration of NO(2) had no significant effect on mortality from circulatory system diseases (P > 0.05). CONCLUSION: Our findings in this study elucidated that changes of the concentration of PM(10) and SO(2) had a positive correlation with daily mortality from circulatory system diseases among the local residents in Chaoyang District, whereas the daily concentration of NO(2) was irrelevant with that.

[Status and distribution of atmospheric ultrafine particles during Olympics Games in Beijing].

OBJECTIVE: To understand the characteristics of size and concentration of the ultrafine particles (UFPs) during the 2008 Olympics in Beijing, as well as the influencing factors for number concentration of UFPs. METHODS: Ultrafine particle monitor model 3031, manufactured by USA TSI Co., was used to monitor the daily number concentration of 20-500 nm particles, and descriptive analysis was conducted based on the data collected. RESULTS: During the Olympics, the mean value of number concentration for 20-100 nm particulate matter is 5 920.43 particles/ cm3. Particles ranging 30-50 nm account for the largest portion(23.49%) among particles of all sizes. There are two peak values on the curve of 24 hours' number concentration for 20-100 nm particles, respectively, at noon and evening. CONCLUSION: This paper indicates that the number concentration of ultrafine particles registered considerable reduction in the 2008's Olympics compared to the pre-Olympics years. And observation of the curves indicated that the number concentrations of the UFPs with bigger size are related to traffic volume, whereas for smaller size UFPs, illumination may be a more important influencing factor. Also there are significant correlations between number concentration and temperature as well as relative humidity.

[The correlations between air quality and heart rate variability in aged susceptible people during Beijing Olympic Games 2008].

OBJECTIVE: To observe the variations of the concentrations of air pollutants and explore the correlation between the heart rate variability (HRV) of the aged people and the air quality during Beijing Olympic Games 2008. METHODS: A panel study design was adopted. A total of twenty-six over 55-year-old patients with coronary heart disease or angina pectoris or a symptom of myocardial ischemia at least for one year were enrolled as a panel and followed up five times by measuring HRV index and other related indexes from June to September in 2008. The correlations between the HRV of the aged people and the air quality was analyzed with the linear mixed-effect models according to the data of air pollutants and meteorological conditions collected simultaneously from Beijing Environmental Protection Bureau and Beijing Meteorological Bureau. RESULTS: In single-pollutant mixed-effect models, the significant correlation was observed in the reduction of ambient PM(10), SO(2) and NO(2) with the improvement of the total power and high-frequency power (HF) of HRV in the panel subjects, and a 10 microg/m(3) decrease in PM(10), SO(2) and NO(2) level was correlated with 2.51% (95%CI: -3.80% - -1.22%, t = -1.99, P = 0.0497), 31.39% (95%CI: -52.24% - -10.53%, t = -1.99, P = 0.0497) and 42.72% (95%CI: -75.06% - -10.38%, t = -1.99, P = 0.0497) rises in total power of HRV respectively. A 10 microg/m(3) decrease in PM(10), SO(2) and NO(2) level was correlated with 3.46% (95%CI: -5.14% - -1.77%, t = -2.11, P = 0.0378), 40.63% (95%CI: -68.70% - -12.56%, t = -2.11, P = 0.0378) and 53.76% (95%CI: -97.97% - -9.56%, t = -2.11, P = 0.0378) rises in high-frequency power (HF) of HRV respectively. CONCLUSION: It suggests that the air pollution reduction could improve the cardiovascular functions of the susceptible population.

Chord-based image reconstruction in cone-beam CT with a curved detector.

Modern computed tomography (CT) scanners use cone-beam configurations for increasing volume coverage, improving x-ray-tube utilization, and yielding isotropic spatial resolution. Recently, there have been significant developments in theory and algorithms for exact image reconstruction from cone-beam projections. In particular, algorithms have been proposed for image reconstruction on chords; and advantages over the existing algorithms offered by the chord-based algorithms include the high flexibility of exact image reconstruction for general scanning trajectories and the capability of exact reconstruction of images within a region of interest from truncated data. These chord-based algorithms have been developed only for flat-panel detectors. Many cone-beam CT scanners employ curved detectors for important practical considerations. Therefore, in this work, we have derived chord-based algorithms for a curved detector so that they can be applied to reconstructing images directly from data acquired by use of a CT scanner with a curved detector. We have also conducted preliminary numerical studies to demonstrate and evaluate the reconstruction properties of the derived chord-based algorithms for curved detectors.

Exposure-response functions for health effects of ambient air pollution applicable for China -- a meta-analysis.

Assessing the benefits of projects and policies to reduce air pollution requires quantitative knowledge about the relationship between exposure to air pollution and public health. This article proposes exposure-response functions for health effects of PM10 and SO2 pollution in China. The functions are based on Chinese epidemiological studies, and cover mortality, hospital admissions, and chronic respiratory symptoms and diseases. We derive the following coefficients for acute effects: a 0.03% (S.E. 0.01) and a 0.04% (S.E. 0.01) increase in all-cause mortality per microg/m3 PM10 and SO2, respectively, a 0.04% (S.E. 0.01) increase in cardiovascular deaths per microg/m3 for both PM10 and SO2, and a 0.06% (S.E. 0.02) and a 0.10% (S.E. 0.02) increase in respiratory deaths per microg/m3 PM10 and SO2, respectively. For hospital admissions due to cardiovascular diseases the obtained coefficients are 0.07% (S.E. 0.02) and 0.19% (S.E. 0.03) for PM10 and SO2, respectively, whereas the coefficients for hospital admissions due to respiratory diseases are 0.12% (S.E. 0.02) and 0.15% (S.E. 0.03) for PM10 and SO2, respectively. Exposure-response functions for the impact of long-term PM10 levels on the prevalence of chronic respiratory symptoms and diseases are derived from the results of cross-sectional questionnaire surveys, and indicate a 0.31% (S.E. 0.01) increase per microg/m3 in adults and 0.44% (S.E. 0.02) per microg/m3 in children. With some exceptions, Chinese studies report somewhat lower exposure-response coefficients as compared to studies in Europe and USA.

[Relationship of the hair content of rare earth elements in young children aged 0 to 3 years to that in their mothers living in a rare earth mining area of Jiangxi].

OBJECTIVE: To study the relationship of hair content of rare earth elements (REEs) in the young children aged 0 - 3 years to that in their mothers living in a rare earth mining area of Jiangxi Province. METHODS: Content of five kinds of REEs, i.e., lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd) and samarium (Sm) were determined for the hair-root samples collected from 71 young children and 62 of their mothers by inductively coupled plasma source mass spectrometry (ICP-MS). RESULTS: The mean hair content of REEs (e.g., La) was the highest (2,202.90 ng/g) in the young children living in the place nearest to the REE mining area, next (471.72 ng/g) was in those nearer to the REE mining area, and the lowest (97.37 ng/g) was in those in the control area. And, the hair content of REEs in the mothers was the same as that in their children, i.e, the mean content of La was the highest (1,510.21 ng/g) in high-exposure area, next (241.63 ng/g) was that in the low-exposure area, and the lowest (59.15 ng/g) was that in the control area, with P < 0.001. Pair-comparison analysis for the means showed that the average hair level of five kinds of REEs in the young children was two times high as their mothers' (P < 0.001). For example, the hair level of La was 533.83 ng/g in the young children and 279.78 ng/g in their mothers, respectively. Simple linear regression analysis showed that there was a significant correlation between the hair levels of each kind of REEs in the young children and those in their mothers, with a correlation coefficient of more than 0.75, e.g., that of La was 0.878 (P < 0.01). CONCLUSIONS: The hair level of REEs can be used as a bio-marker to reflect body's level of exposure to REEs. The hair level of REEs in young children and their mothers decreased with the increase of the distance from their home to rare earth mining area. Young children living in the area with REEs mining may be the high-exposure population, and their hair level of REEs was significantly higher than that in their mothers and more attention should be paid to them.

Visual pattern discrimination by population retinal ganglion cells' activities during natural movie stimulation.

In the visual system, neurons often fire in synchrony, and it is believed that synchronous activities of group neurons are more efficient than single cell response in transmitting neural signals to down-stream neurons. However, whether dynamic natural stimuli are encoded by dynamic spatiotemporal firing patterns of synchronous group neurons still needs to be investigated. In this paper we recorded the activities of population ganglion cells in bullfrog retina in response to time-varying natural images (natural scene movie) using multi-electrode arrays. In response to some different brief section pairs of the movie, synchronous groups of retinal ganglion cells (RGCs) fired with similar but different spike events. We attempted to discriminate the movie sections based on temporal firing patterns of single cells and spatiotemporal firing patterns of the synchronous groups of RGCs characterized by a measurement of subsequence distribution discrepancy. The discrimination performance was assessed by a classification method based on Support Vector Machines. Our results show that different movie sections of the natural movie elicited reliable dynamic spatiotemporal activity patterns of the synchronous RGCs, which are more efficient in discriminating different movie sections than the temporal patterns of the single cells' spike events. These results suggest that, during natural vision, the down-stream neurons may decode the visual information from the dynamic spatiotemporal patterns of the synchronous group of RGCs' activities.

[The impact of ambient particulate matter (PM10) on the population mortality for cerebrovascular diseases-a case-crossover study].

OBJECTIVE: To analyze the association between the concentration of ambient inhalable particulate matter (PM10) and population mortality for cerebrovascular diseases and to explore the impact of PM10 on cerebrovascular diseases. METHODS: Data including meteorological factors, air pollutants (NO2, SO2 and PM10) and cerebrovascular disease mortality in one district of Beijing from 2004 to 2008 were collected and both symmetric bidirectional case-crossover design and conditional logistic regression model were used to analyze the associations among them. RESULTS: After adjusting the influence of meteorological factors as daily average temperature and relative humidity, the single pollutant model showed that there was no significant lag effect. In the multi-pollutant model, the effect of the every 105.43 µg/m(3) increase of ambient PM10 had a larger impact on the daily death of the cerebrovascular diseases with statistically significant difference (P < 0.05). The effect of ambient PM10 pollution on daily death of cerebrovascular diseases was significant for females, 65 year-olds and in winter season. CONCLUSION: Our data showed that elevated levels of ambient PM10 was positively associated with the increase of cerebrovascular disease mortality. The elevated levels of ambient PM10 could lead to the increase of the daily mortality on cerebrovascular diseases for females, elderly who were 65 or older and in winter seasons.

Sub-micrometer particulate air pollution and cardiovascular mortality in Beijing, China.

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 0.003 µm and 0.8 µm 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 0.03-0.1 µm (7.1% increase in daily mortality with a 95%-confidence interval of 2.9%-11.5%, per an increase of 6250 particles/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.

Size-segregated particle number concentrations and respiratory emergency room visits in Beijing, China.

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 (NO(2)), 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 NO(2) 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 NO(2). CONCLUSIONS: Present levels of air pollution in Beijing were adversely associated with respiratory ERV. NO(2) concentrations seemed to be a better surrogate for evaluating overall respiratory health effects of ambient air pollution than PM(10) or particle number concentrations in Beijing.

[Association between ambient air pollution and hospital emergency room visits for respiratory diseases: a case-crossover study].

OBJECTIVE: Using case-crossover design to explore the association between ambient air pollution and the hospital emergency room visits for respiratory diseases (International Classification of Diseases, tenth vision ICD-10: J00-J99) in Beijing, China. METHODS: Data regarding the daily hospital emergency room visits of the respiratory diseases (ICD-10: J00-J99) were obtained in 2004.01.01 - 2005.12.31, from the Peking University Third Hospital and data on relevant air pollution and meteorological factors from the local municipal environmental monitoring center and meteorology bureau of Beijing, respectively. Time-stratified case-crossover technique was used to evaluate their relationships. Results from the bi-directional control sampling approach were compared with unidirectional approach. RESULTS: Using a unidirectional control sampling approach, the results obtained from a conditional logistic regression model (multi-pollutant model) after adjusting for meteorological variables, showed that the ORs of the hospital emergency room visits for the respiratory diseases associated with each 10 µg/m(3) increment of PM(10), SO(2), NO(2) were 1.010 (95%CI: 1.005 - 1.014), 1.010 (95%CI: 1.001 - 1.018), 0.996 (95%CI: 0.983 - 1.009) respectively. In the bi-directional control sampling approach, the ORs were 1.002 (95%CI: 0.998 - 1.005), 1.011 (95%CI: 1.003 - 1.018), 1.012 (95%CI: 1.001 - 1.022). CONCLUSION: Results from this study provided evidence that higher levels of ambient air pollutants increased the risk of hospital emergency room visits for respiratory diseases.

Exposures to particulate matter and polycyclic aromatic hydrocarbons and oxidative stress in schoolchildren.

BACKGROUND: Air pollution is known to contribute to respiratory and cardiovascular mortality and morbidity. Oxidative stress has been suggested as one of the main mechanisms for these effects on health. OBJECTIVE: The aim of this study was to analyze the effects of exposure to particulate matter (PM) with aerodynamic diameters < or = 10 microm (PM10) and < or = 2.5 microm (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) on urinary malondialdehyde (MDA) levels in schoolchildren. METHODS: The study population consisted of 120 schoolchildren. The survey and measurements were conducted in four cities--two in China (Ala Shan and Beijing) and two in Korea (Jeju and Seoul)--between 4 and 9 June 2007. We measured daily ambient levels of PM and their metal components at the selected schools during the study period. We also measured urinary 1-hydroxypyrene (1-OHP) and 2-naphthol, to assess PAH exposure, and MDA, to assess oxidative stress. Measurements were conducted once a day for 5 consecutive days. We constructed a linear mixed model after adjusting for individual variables to estimate the effects of PM and PAH on oxidative stress. RESULTS: We found statistically significant increases in urinary MDA levels with ambient PM concentrations from the current day to the 2 previous days (p < 0.0001). Urinary 1-OHP level also showed a positive association with urinary MDA level, which was statistically significant with or without PM in the model (p < 0.05). Outdoor PM and urinary 1-OHP were synergistically associated with urinary MDA levels. Some metals bound to PM10 (aluminum, iron, strontium, magnesium, silicon, arsenic, barium, zinc, copper, and cadmium) and PM2.5 (magnesium, iron, strontium, arsenic, cadmium, zinc, aluminum, mercury, barium, and copper) also had significant associations with urinary MDA level. CONCLUSION: Exposure to PM air pollution and PAHs was associated with oxidative stress in schoolchildren.