Particulate-bound polycyclic aromatic hydrocarbons in naturally ventilated multi-storey residential buildings of Singapore: Vertical distribution and potential health risks

The main objective of the study is to quantify the polycyclic aromatic hydrocarbons (PAHs) concentration levels (US EPA priority components) in fine traffic-generated particles (PM_2.5) at various heights of typical multi-storey public housing buildings located in close proximity, i.e. within 30 m and along a busy major expressway in Singapore. The secondary objective is to estimate the potential health risks associated with inhalation exposure, based on the toxic equivalency factors (TEFs) at the various floors of these buildings. Two typical public housing buildings, both naturally ventilated residential apartment blocks, of point block configuration (22-storey) and slab block configuration (16-storey) were selected for the study. Particulate samples were collected for chemical analysis at three representative floors: the lower, the mid, and the upper floors of the buildings. Key meteorological parameters such as wind speed, wind direction, ambient temperature, and relative humidity were also measured at the representative floors. All samples were analyzed for the 16 PAH priority pollutants listed by US EPA. The vertical PAH distribution profile varies with height of building depending on the type of block configuration. The total mean concentrations of particulate PAHs for point and slab blocks are 3.32±1.76 ng/m³ (0.56–7.2 ng/m³) and 6.0±1.88 ng/m³ (3.19–10.26 ng/m³), respectively. For the point block, the highest mean total PAH concentration occurred at the mid floor followed by the upper floor. The lower floor had the least mean total PAH concentration. For the slab block, the highest mean total PAH concentration occurred at the lower floor and remained almost constant up to the mid floor and thereafter gradually decreased from mid floor to upper floor of the building. These results suggest that the building configuration influences the vertical distribution of particulate PAHs. The dominant particulate PAHs measured at the point block are naphthalene, acenaphthylene, benzo(b)fluoranthene, and benzo(g,h,i)perylene while those for the slab block, the main particulate PAHs are naphthalene, phenanthrene, fluoranthene, and benzo(g,h,i)perylene. The Bpe/Ind ratio for both blocks ranged from 0.92±0.2 to 1.63±0.6 indicating particulate PAHs are contributed by a mixture of both diesel and petrol engine type of vehicles, with diesel engine vehicles contributing a higher percentage of particulate PAHs to the different floor levels of both buildings. The total BaP_eq concentrations for point and slab blocks are 1.06±0.64 ng/m³ (0.14–2.45 ng/m³) and 0.94±1.22 ng/m³ (0.10–4.59 ng/m³), respectively. The total BaP equivalency results showed the potential health risk to cancer due to inhalation exposure is of concern for residents living in both blocks since the total BaP_eq concentrations for both blocks were very close to, or slightly exceeded the maximum permissible risk level of 1 ng/m³ of benzo(a)pyrene.     

中国钛发展的四十年

系统介绍了钛基复合材料的最新研究和发展，涉及非连续颗粒增强和连续纤维增强两大类钛基复合材料近１０多年来的研究成果和发展趋势；重点评述了钛基材和增强剂的选择，增强剂与基体界面反应的研究，扩散障碍涂层技术和钛基复合材料制造工艺的研究和发展，讨论了钛基复合材料的应用前景。     

Is the association between temperature and mortality modified by age, gender and socio-economic status?

Background

A number of studies have examined the relationship between high ambient temperature and mortality. Recently, concern has arisen about whether this relationship is modified by socio-demographic factors. However, data for this type of study is relatively scarce in subtropical/tropical regions where people are well accustomed to warm temperatures.

Objective

To investigate whether the relationship between daily mean temperature and daily all-cause mortality is modified by age, gender and socio-economic status (SES) in Brisbane, Australia.

Methods

We obtained daily mean temperature and all-cause mortality data for Brisbane, Australia during 1996-2004. A generalised additive model was fitted to assess the percentage increase in all deaths with every one degree increment above the threshold temperature. Different age, gender and SES groups were included in the model as categorical variables and their modification effects were estimated separately.

Results

A total of 53,316 non-external deaths were included during the study period. There was a clear increasing trend in the harmful effect of high temperature on mortality with age. The effect estimate among women was more than 20 times that among men. We did not find an SES effect on the percent increase associated with temperature.

Conclusions

The effects of high temperature on all deaths were modified by age and gender but not by SES in Brisbane, Australia.     

The relationship between particulate air pollution and emergency hospital visits for hypertension in Beijing, China

Background

A number of epidemiological studies have examined the adverse effect of air pollution on mortality and morbidity. Also, several studies have investigated the associations between air pollution and specific-cause diseases including arrhythmia, myocardial infarction, and heart failure. However, little is known about the relationship between air pollution and the onset of hypertension.

Objective

To explore the risk effect of particulate matter air pollution on the emergency hospital visits (EHVs) for hypertension in Beijing, China.

Methods

We gathered data on daily EHVs for hypertension, fine particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5), particulate matter less than 10 μm in aerodynamic diameter (PM₁₀), sulfur dioxide, and nitrogen dioxide in Beijing, China during 2007. A time-stratified case-crossover design with distributed lag model was used to evaluate associations between ambient air pollutants and hypertension. Daily mean temperature and relative humidity were controlled in all models.

Results

There were 1,491 EHVs for hypertension during the study period. In single pollutant models, an increase in 10 μg/m³ in PM_2.5 and PM₁₀ was associated with EHVs for hypertension with odds ratios (overall effect of five days) of 1.084 (95% confidence interval (CI): 1.028, 1.139) and 1.060% (95% CI: 1.020, 1.101), respectively.

Conclusion

Elevated levels of ambient particulate matters are associated with an increase in EHVs for hypertension in Beijing, China.     

Capacitance monitoring of the infiltration of ceramic Particulate Preforms with Liquid Metals at 750 to 850 °C

The authors previously developed a capacitance technique to determine the position of the infiltration front as a function of time during the pressure infiltration of ceramic particulate preforms with liquid metals. In the present work, the technique was extended to higher temperatures and was used to monitor the infiltration of alumina particulate preforms with Al-Mg alloys and silicon carbide particulate pre-forms with Sn and an Al-Si alloy. The infiltration front position could be determined in the alumina pre-forms. However, it was not possible to clearly interpret the results obtained from the infiltration of semiconducting silicon carbide preforms. The observed range of capacitance circuit voltage to infiltra-tion distance ratios agreed with the predicted range for both simulated and alumina preform infiltration experiments. Formation of unstable infiltration fronts could also be detected.     

The effect of coal and diesel particulates on the weathering loss of Portland Limestone in an urban environment

Due to reductions in domestic usage, legislation and changes in fuel use, coal derived particulates in the UK urban atmosphere have been significantly reduced. However, a large increase in road usage and an expansion in the use of diesel engines, has meant that the majority of particulates, now present in the urban atmosphere, originate from vehicle exhausts. Particulate matter, resulting from coal combustion, has been recorded as being present in black patinas observed on some historic stone buildings and monuments and has been associated with accelerated weathering of stone surfaces as a result of enhanced gypsum formation. In contrast, the effects of particulates resulting from vehicle exhaust on stone are much less understood. To investigate this, a comparative study was undertaken using the technique of microcatchments under ambient atmospheric conditions. This compared the elemental composition and volume of precipitation runoff from Portland Limestone coated with three different particulate treatments. Treatments consisted of coal and diesel particulates, both separately and in combination. Combining these treatments attempts to investigate any synergistic effects that may occur when coal derived particulates are overlain by layers formed by particulates from more contemporary sources. It was found that diesel-coated samples were much darker in appearance and showed a significant reduction (P<0.05) in the overall rate of weathering loss when compared to untreated samples. Microcatchment runoff volume was reduced from diesel-coated Portland Limestone compared to untreated stone. Enhanced surface temperatures may be increasing the rate of moisture loss from the pore network between rainfall events. Since, generally, the pores must be full before runoff can occur, the reduction may be due to the differential volume of empty pore space between diesel-coated and untreated Portland Limestone.     

Particulate Lead in Water Supplies

This paper describes research in areas where the occasional failure to meet the EC standard for lead in drinking water is due to the presence of particulate lead. A method is described to disinguish between soluble, particulate and colloidal lead in tap water, and characteristics are given of water sources which are most likely to suffer from this form of lead problem. At least two types of particulate (insoluble) lead in tap water have been identified, and some factors are discussed which cause the occurrence of both types. Interim results of trials are presented, with remedial actions.     

Bacterial communities in commercial aircraft high‐efficiency particulate air (HEPA) filters assessed by PhyloChip analysis

Abstract  Air travel can rapidly transport infectious diseases globally. To facilitate the design of biosensors for infectious organisms in commercial aircraft, we characterized bacterial diversity in aircraft air. Samples from 61 aircraft high‐efficiency particulate air (HEPA) filters were analyzed with a custom microarray of 16S rRNA gene sequences (PhyloChip), representing bacterial lineages. A total of 606 subfamilies from 41 phyla were detected. The most abundant bacterial subfamilies included bacteria associated with humans, especially skin, gastrointestinal and respiratory tracts, and with water and soil habitats. Operational taxonomic units that contain important human pathogens as well as their close, more benign relatives were detected. When compared to 43 samples of urban outdoor air, aircraft samples differed in composition, with higher relative abundance of Firmicutes and Gammaproteobacteria lineages in aircraft samples, and higher relative abundance of Actinobacteria and Betaproteobacteria lineages in outdoor air samples. In addition, aircraft and outdoor air samples differed in the incidence of taxa containing human pathogens. Overall, these results demonstrate that HEPA filter samples can be used to deeply characterize bacterial diversity in aircraft air and suggest that the presence of close relatives of certain pathogens must be taken into account in probe design for aircraft biosensors.

Practical Implications

A biosensor that could be deployed in commercial aircraft would be required to function at an extremely low false alarm rate, making an understanding of microbial background important. This study reveals a diverse bacterial background present on aircraft, including bacteria closely related to pathogens of public health concern. Furthermore, this aircraft background is different from outdoor air, suggesting different probes may be needed to detect airborne contaminants to achieve minimal false alarm rates. This study also indicates that aircraft HEPA filters could be used with other molecular techniques to further characterize background bacteria and in investigations in the wake of a disease outbreak.

     

机动车颗粒物排放控制策略研究

颗粒物已经成为造成环境污染和影响人体健康的主要污染物之一,而机动车颗粒物排放占污染物的60%以上。目前中国对机动车颗粒物排放的研究较少,没有系统提出相应的控制策略。文章首先分析了机动车颗粒物的生成机理及影响因素;根据《中国机动车污染防治年报》统计数据,使用MATLAB建立了汽车、低速汽车及机动车数量与颗粒物排放量之间的数学模型,预测未来5 a内的机动车颗粒物的排放总量。结果表明机动车颗粒物排放逐年增加,2015年将达到1.032 2×10 6 t;而低速汽车数的PM排放量会逐年缓慢降低,这主要受国家政策影响。最后,根据分析预测结果,提出了机动车颗粒物排放控制策略。     

State of the art in additive manufacturing and its possible chemical and particle hazards—review

Additive manufacturing, enabling rapid prototyping and so-called on-demand production, has become a common method of creating parts or whole devices. On a 3D printer, real objects are produced layer by layer, thus creating extraordinary possibilities as to the number of applications for this type of devices. The opportunities offered by this technique seem to be pushing new boundaries when it comes to both the use of 3D printing in practice and new materials from which the 3D objects can be printed. However, the question arises whether, at the same time, this solution is safe enough to be used without limitations, wherever and by everyone. According to the scientific reports, three-dimensional printing can pose a threat to the user, not only in terms of physical or mechanical hazards, but also through the potential emissions of chemical substances and fine particles. Thus, the presented publication collects information on the additive manufacturing, different techniques, and ways of printing with application of diverse raw materials. It presents an overview of the last 5 years’ publications focusing on 3D printing, especially regarding the potential chemical and particle emission resulting from the use of such printers in both the working environment and private spaces.