Chuan-Yao Lin

Higher temperature and urbanization affect the spatial patterns of dengue fever transmission in subtropical Taiwan

Our study conducted spatial analysis to examine how temperature and other environmental factors might affect dengue fever distributions, and to forecast areas with potential risk for dengue fever endemics with predicted climatic change in Taiwan. Geographic information system (GIS) was used to demonstrate the spatial patterns of all studied variables across 356 townships. Relationships between cumulative incidence of dengue fever, climatic and non-climatic factors were explored. Numbers of months with average temperature higher than 18 degrees C per year and degree of urbanization were found to be associated with increasing risk of dengue fever incidence at township level. With every 1 degrees C increase of monthly average temperature, the total population at risk for dengue fever transmission would increase by 1.95 times (from 3,966,173 to 7,748,267). A highly-suggested warmer trend, with a statistical model, across the Taiwan Island is predicted to result in a sizable increase in population and geographical areas at higher risk for dengue fever epidemics.

Characterization and sources of aerosol particles over the southeastern Tibetan Plateau during the Southeast Asia biomass-burning season

The Tibetan Plateau is one of the highest regions in theworld, exerting profound influence on the large-scale atmospheric circulation of Asia and the global climate. Here we report ambient concentrations of black carbon (BC), aerosol mass (PM2.5 and PM10) and associated carbonaceous species and water-soluble inorganic ions from a remote mountain site in the southeastern part of the Tibetan Plateau during spring, in order to characterize the major sources contributing to the ambient aerosol in the background atmosphere of Southeast Asia. Significant build-up of aerosol and BC concentrations was observed during a dry period, accompanied by the occurrence of fires and transport of pollution from the nearby regions of Southeast Asia and the northern part of the Indian Peninsula. The concentrations of BC, PM2.5 and PM10 mass reached maximum hourly values of 1470 ng m-3, 107 and 117 μg m-3, respectively. Organic carbon (OC), elemental carbon (EC) and sulfate were the predominant aerosol components. OC showed strong correlations with EC (R2 = 0.93 for PM2.5 and 0.74 for PM10) and non-sea-salt potassium, especially in fine aerosol (R2 = 0.95). In addition, the relative change rates of K+ against OC reached characteristically high values, highlighting the important contributions of biomass-burning smoke.

Effects of extreme precipitation to the distribution of infectious diseases in Taiwan, 1994-2008.

The incidence of extreme precipitation has increased with the exacerbation of worldwide climate disruption. We hypothesize an association between precipitation and the distribution patterns that would affect the endemic burden of 8 infectious diseases in Taiwan, including water- and vector-borne infectious diseases. A database integrating daily precipitation and temperature, along with the infectious disease case registry for all 352 townships in the main island of Taiwan was analysed for the period from 1994 to 2008. Four precipitation levels, <130 mm, 130–200 mm, 200–350 mm and >350 mm, were categorized to represent quantitative differences, and their associations with each specific disease was investigated using the Generalized Additive Mixed Model and afterwards mapped on to the Geographical Information System. Daily precipitation levels were significantly correlated with all 8 mandatory-notified infectious diseases in Taiwan. For water-borne infections, extreme torrential precipitation (>350 mm/day) was found to result in the highest relative risk for bacillary dysentery and enterovirus infections when compared to ordinary rain (<130 mm/day). Yet, for vector-borne diseases, the relative risk of dengue fever and Japanese encephalitis increased with greater precipitation only up to 350 mm. Differential lag effects following precipitation were statistically associated with increased risk for contracting individual infectious diseases. This study’s findings can help health resource sector management better allocate medical resources and be better prepared to deal with infectious disease outbreaks following future extreme precipitation events.

Impact of the Urban Heat Island Effect on Precipitation over a Complex Geographic Environment in Northern Taiwan

Abstract To evaluate the impacts of the urban heat island (UHI) effect on precipitation over a complex geographic environment in northern Taiwan, the next-generation mesoscale model, the Weather Research and Forecasting (WRF) model, coupled with the Noah land surface model and urban canopy model (UCM), was used to study this issue. Based on a better land use classification derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data (the MODIS case), it has significantly improved simulation results for the accumulation rainfall pattern as compared with the original U.S. Geological Survey (USGS) 25-category land use classification (the USGS case). The precipitation system was found to develop later but stronger in the urban (MODIS) case than in the nonurban (USGS) case. In comparison with the observation by radar, simulation results predicted reasonably well; not only was the rainfall system enhanced downwind of the city over the mountainous area, but it also occurred at the upwind pla...

The Association between Enterovirus 71 Infections and Meteorological Parameters in Taiwan

Background Enterovirus 71 (EV71) infections are a significant cause of neurological disorder and death in children worldwide. Seasonal variations in EV71 infections have been recognized, but the mechanisms responsible for this phenomenon remain unknown. The purpose of this study was to examine the relationship between meteorological parameters and EV71 infection. Methods and Findings We analyzed the number of EV71 infections and daily climate data collected in Taiwan between 1998 and 2008 and used Poisson regression analysis and case-crossover methodology to evaluate the association between weather variability and the incidence of EV71 infection. A total of 1,914 EV71-infected patients were reported between 1998 and 2008. The incidence of EV71 infections reflected significant summertime seasonality (for oscillation, p<0.001). The incidence of EV71 infections began to rise at temperatures above 13°C (r2 = 0.76, p<0.001); at temperatures higher than approximately 26°C (r2 = 0.94, p<0.05), the incidence began to decline, producing an inverted V-shaped relationship. The increase in the incidence with increasing relative humidity was positive and linear (r2 = 0.68, p<0.05). EV71 infection was most highly correlated with temperature and relative humidity in the period that likely preceded the infection. Conclusion Our study provides quantitative evidence that the rate of EV71 infection increased significantly with increasing mean temperature and relative humidity in Taiwan.

Cardiovascular mortality during heat and cold events: determinants of regional vulnerability in Taiwan

Objectives To identify the vulnerable regions with underlying susceptibility and poor adaptive capability in response to cold and heat events in Taiwan, and to characterise the determinants associated with such an increasing risk to design better adaptive strategies in view of predicted weather changes in the future. Methods The authors used spatial regression models to measure the relationships between the spatial characteristics of temperature, extracted factors from demographic and socio-economic parameters, and the mean cardiovascular mortality 2 weeks before and after cold or heat events from 1994 to 2003. Results Metropolitan regions were found to have a substantially lower mortality than rural areas after cold and heat events. Events of cold, compared with heat, had greater impacts on the mortality ratio in most townships. A negative association was identified, using a spatial lag model, between the mortality after cold and heat events and urbanisation, and the availability of medical resources. A higher percentage of older people, vulnerable and aborigines might have contributed to the increasing vulnerability of townships during cold and heat events. Conclusions These data, using an island-wide spatial analysis, suggest that urban areas have a greater adaptive capability than rural areas, plausibly because people in urban areas have a higher socio-economic status and more medical resources. Social inequality across urban and rural townships is apparent and developing customised adaptation programmes for vulnerable regions to cope with heat and cold event should be prioritised.

PCDD/F Measurement at a High-Altitude Station in Central Taiwan: Evaluation of Long-Range Transport of PCDD/Fs during the Southeast Asia Biomass Burning Event

Recent biomass burning in Southeast Asia has raised global concerns over its adverse effects on visibility, human health, and global climate. The concentrations of total suspended particles (TSPs) and other vapor-phase pollutants (CO and ozone) were monitored at Lulin, an atmospheric background station in central Taiwan in 2008. To evaluate the long-range transport of persistent organic pollutants (POPs) during the Southeast Asia biomass burning event, the atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were also measured at Lulin station. The atmospheric PCDD/F and TSP concentrations measured at Lulin station ranged from 0.71-3.41 fg I-TEQ/m(3) and 5.32-55.6 microg/m(3), respectively, during the regular sampling periods. However, significantly higher concentrations of PCDD/Fs, TSPs, CO, and ozone were measured during the spring season. These high concentrations could be the result of long-range transport of the products of Southeast Asia biomass burning. During the Southeast Asia biomass burning event (March 18-24, 2008), an intensive observation program was also carried out at the same station. The results of this observation program indicated that the atmospheric PCDD/F concentration increased dramatically from 2.33 to 390 fg I-TEQ/m(3) (March 19, 2008). The trace gas (CO) of biomass burning also significantly increased to 232 ppb during the same period, while the particle-bound PCDD/Fs in the TSP increased from 28.7 to 109 pg I-TEQ/g-TSP at Lulin station during the burning event. We conclude that there was a significant increase in the PCDD/F concentration in ambient air at a high-altitude background station in central Taiwan during the Southeast Asia biomass burning event.

Relationship between mean daily ambient temperature range and hospital admissions for schizophrenia: Results from a national cohort of psychiatric inpatients

Environmental temperature is known to correlate with schizophrenia, but little is known about the association with changes in temperature. This 12-year study aimed to evaluate the relationship between the mean daily range of ambient temperature and schizophrenia admissions in a national cohort of psychiatric inpatients in Taiwan. Meteorological data provided by the Central Weather Bureau of Taiwan were interpolated to create representative estimates. Psychiatric inpatient admissions in all hospitals with medical services enrolled in the current health care insurance system were retrieved from the 1996-2007 Psychiatric Inpatient Medical Claim dataset of the National Health Insurance Research Database. Generalized linear models with Poisson distributions were used to analyze the impact of mean diurnal change of temperature on schizophrenia admissions, controlling for internal correlations and demographic covariates. The daily temperature range varied between 1.7°C and 12.1°C (1st to 99th percentile). The relative risk of schizophrenia admission was significantly increased at a temperature range of 3.2°C (10th percentile), and the maximum was at 12.1°C (99th percentile); however, no such association was found with schizoaffective disorder. When restricted to the capital and largest city, the effects of temperature range were prominent and may correlate with temperature itself. The joint effect of temperature and temperature range was associated with elevated risk, particularly at cooler temperatures. A positive correlation was found between increasing temperature range and schizophrenia admissions. The increase in morbidity at high percentiles suggests that the increasing dynamics of temperature range are a valid reflection of risk, highlighting the need for precautionary action.

Relationship between heat index and mortality of 6 major cities in Taiwan

Increased mortality, linked to events of extreme high temperatures, is recognized as one critical challenge to the public health sector. Therefore, this ecological study was conducted to assess whether this association is also significant in Taiwan and the characteristics of the relationship. Daily mean heat indices, from 1994 through 2008, were used as the predictor for the risk of increased mortality in populations from 6 major Taiwanese cities. Daily mortality data from 1994 through 2008 were retrieved from the Taiwan Death Registry, Department of Health, Taiwan, and meteorological data were acquired from the Central Weather Bureau. Poisson regression analyses using generalized linear models were applied to estimate the temperature-mortality relationship. Daily mean heat indices were calculated and used as the temperature metric. Overall, increased risk ratios in mortality were associated with increased daily mean heat indices. Significantly increased risk ratios of daily mortality were evident when daily mean heat indices were at and above the 95th percentile, when compared to the lowest percentile, in all cities. These risks tended to increase similarly among those aged 65 years and older; a phenomenon seen in the cities of Keelung, Taipei, Taichung, Tainan, and Kaohsiung, but not Chiayi. Being more vulnerable to heat stress is likely restricted to a short-term effect, as suggested by lag models which showed that there was dominantly an association during the period of 0 to 3 days. In Taiwan, predicting city-specific daily mean heat indices may provide a useful early warning system for increased mortality risk, especially for the elderly. Regional differences in health vulnerabilities should be further examined in relation to the differential social-ecological systems that affect them.

Modelling of long-range transport of Southeast Asia biomass-burning aerosols to Taiwan and their radiative forcings over East Asia

Biomass burning produces aerosols and air pollutants during springtime in Southeast Asia. At the Lulin Atmospheric Background Station (LABS) (elevation 2862 m) in central Taiwan, the concentrations of carbon monoxide (CO), ozone (O3) and particulate matter with a diameter less than 10 µm (PM10) were found to be 135–200 ppb, 40–56 ppb and 13–26 µg/m3, respectively, in the springtime (February–April) between 2006 and 2009, which are 2–3 times higher than those in other seasons. Simulation results indicate that higher concentrations during springtime are related to biomass-burning plumes transported from the Indochinese peninsula of Southeast Asia. The spatial distribution of high aerosol optical depth (AOD) was identified by satellite measurement and Aerosol Robotic Network (AERONET) ground observation, and could be reasonably captured by the WRF-Chem model during the study period of 15–18 March 2008. Simulated AOD reached as high as 0.8–1.2 in Indochina situated between 10–22°N and 95–107°E. According to the simulation results, 34% of the AOD was attributed to organic carbon over Indochina, while the contribution of black carbon to AOD was about 4%. During the study period, biomass-burning aerosols over Indochina have a net negative effect (−26.85 W·m−2) at ground surface, a positive effect (22.11 W·m−2) in the atmosphere and a negative forcing (−4.74 W·m−2) at the top of atmosphere. Under the influence of biomass-burning aerosol plume transported by strong wind, there is a NE−SW zone stretching from southern China to Taiwan with reduction in shortwave radiation of about 20 W·m−2 at ground surface. Such significant reduction in radiation attributed to biomass-burning aerosols and their impact on the regional climate in East Asia merit attention.