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Objectives Nail workers are exposed to many hazardous chemicals. Despite many warnings about health problems among nail workers in other countries, data concerning exposure to chemical hazards among nail workers is still limited in Vietnam. In this study, we aimed to identify exposure to volatile organic compounds and their relationship with occupational symptoms among Vietnamese female nail salon workers. Methods A cross‐sectional study was conducted in Danang, Vietnam, from January 2019 to September 2019. Total 42 personal passive samplers were collected to evaluate 12 substances from 21 nail workers (15 salons) twice a week. We chose one representative worker from each of the nine salons with less than six workers and two representative workers from each of the six salons with over five workers for personal sampling based on the principle of similar exposure groups. We interviewed a total of 100 nail workers in 15 salons and 100 office workers in offices adjacent to the salons to compare occupational symptoms among them. Results The commonly detected compounds in nail salons were acetone (97.6%), butyl acetate (83.3%), and ethyl acetate and ethyl methacrylate (78%). The concentration of total target VOCs was related to the number of serviced customers, the concentration of CO2, and general ventilation used. The subjective symptoms were significantly higher for the nail workers than for the comparison subjects, that is, headache, nausea, nose irritation, skin irritation, shortness of breath, and confusion. Among 100 nail workers, nose irritation was significantly higher for nail workers who were exposed to acetone at levels exceeding the Vietnam occupational exposure limit (VOEL) adjusted with the Brief‐Scala model. Conclusions Exposure to VOCs such as acetone in nail salons results in occupational symptoms among workers.

Airborne particulate samples were collected in Bangkok, Thailand, using high-volume air samplers from March 2006 to March 2007. The sampling sites were the Huay-Khwang Community Housing (HCH) and the Ratburana Post Office (RPO), represented as residential and industrial areas, respectively. The samples collected were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) for elemental analysis. The study reveals that total suspended particulate (TSP) concentrations are higher in the RPO (144.47 microg/m(3)) than at the HCH (110.93 microg/m(3)) site. The results also indicate that most of the metals were highest in winter and lowest in the rainy season. Na, Al, K, and Fe are the elements mostly found in the study. High-correlation coefficients of Al-K, K-Zn, and Al-Zn are observed at the HCH (R=-0.99, -0.97, and -0.97) and the RPO (R=-0.94, -0.92, and -0.83), respectively. Most of the measured metallic elements show weak correlation with meteorological parameters. Principal component analysis (PCA) indicates that soil, construction, vehicular emission, and biomass burning are the major pollutant sources of both sampling site. The HCH site is influenced by the domestic activities like vehicular emission, construction, and biomass burning. The sources of airborne metals found in the RPO come from both domestic and industrial activities.

The space/time distribution of PM 10 in Thailand is modeled using the Bayesian maximum entropy (BME) method of modern spatiotemporal geostatistics. Three kinds of BME spatiotemporal maps over Thailand are sought on the most polluted day for each year of a 6-year period from 1998 to 2003. These three maps are (1) the map of the BME estimate of daily PM 10 , (2) the map of the associated BME prediction error, and (3) the BME non-attainment map showing areas where the BME estimate does not attain a 68% probability of meeting the ambient standard for PM 10 . These detailed space/time PM 10 maps provide invaluable information for decision-makers in air quality management. Knowing accurately the spatiotemporal distribution of PM 10 is necessary to develop and evaluate strategies used to abate PM 10 levels. The space/time BME estimate of PM 10 on the worst day of the year offers a general picture as to where daily PM 10 levels are not in compliance with the air-quality standard. Delineating these areas leads to the BME non-attainment maps, which are useful in identifying unhealthy zones, where sensitive population such as asthmatic children, seniors, or those with cardiopulmonary disease should be advised to avoid outdoor activities. The results of the space/time BME analysis of PM 10 are further extended to assess whether the current monitoring network is adequate. The current distribution of monitoring stations can be evaluated by combining the available demographic information with the BME estimation error maps. Administrative districts with large population size and high BME normalized estimation error are suggested as the target for adding new monitoring stations.

In order to investigate the ozone dry deposition above a tropical forest in Southeast Asia, the field experiments were performed in a flat deciduous (teak) forest in Mea Moh located in northern Thailand, in the dry season, from January to April 2002. The experimental period included both the leafless period and transitional period between lush and leafless. Ozone fluxes were obtained by coupling a UV photometric ozone monitor with an ultrasonic anemometer on the basis ofthe gradient method. Ozone concentrations exceeded 60 ppb on average in the af ternoons during the experimental period. The ozone fluxes peak around noon. The daytime level ofthe fluxes in this study is relatively high compared with the fluxes from previous experiments over a tropical forest or a leafless deciduous forest in other regions. This high daytime flux level is mainly caused by the high concentrations in the dry season in Mae Moh. Median deposition velocities ofozone were 0.32 cm s � 1 in daytime (6:00–17:00) and 0.04 cm s � 1 in nighttime (18:00–5:00), respectively. The deposition velocities as well as the fluxes peaks around noon. Observed surface resistances decreased in daytime. The surface resistances were found to be affected by aerodynamic process rather than stomatal process during the time from 10:00 to 2:00. Wesely’s parameterization to infer surface resistance was examined to consider its applicability in the region. The observed surface resistance in the dry season is closer to the inferred surface resistance using the input resistances oftransitional spring than that using the input resistances ofleafless seasons. This indicates that the parameterization ofnon-stomatal resistances needs modification above the teak f in the dry season taking into account the influence ofaerodynamic process and the specific conditions in northern Thailand. r 2005 Elsevier Ltd. All rights reserved.

Several studies in North American cities have reported associations between air pollution and respiratory symptoms. Replicating these studies in cities with very different population and weather characteristics is a useful way of addressing uncertainties and strengthening inferences of causality. To this end we examined the responses of three different panels to particulate matter (PM) air pollution in Bangkok, Thailand, a tropical city characterized by a very warm and humid climate. Panels of schoolchildren, nurses, and adults were asked to report daily upper and lower respiratory symptoms for 3 months. Concentrations of daily PM(10) (PM with a mass median aerodynamic diameter less than 10 microm) and PM(2.5) (airborne particles with aerodynamic diameters less than 2.5 microm) were collected at two sites. Generally, associations were found between these pollution metrics and the daily occurrence of both upper and lower respiratory symptoms in each of the panels. For example, an interquartile increase of 45 microg/m(3) in PM(10) was associated with about a 50% increase in lower respiratory symptoms in the panel of highly exposed adults, about 30% in the children, and about 15% in the nurses. These estimates were not appreciably altered by changes in the specification of weather variables, stratification by temperature, or inclusion of individual characteristics in the models; however, time trends in the data cause some uncertainty about the magnitude of the effect of PM on respiratory symptoms. These pollutants were also associated with the first day of a symptom episode in both adult panels but not in children. The estimated odds ratios are generally consistent with and slightly higher than the findings of previous studies conducted in the United States.

Recognizing the adverse effects of acid deposition and its transboundary nature, efforts have been made for the past six years by countries in the East Asian region to establish acid deposition monitoring network in the region by taking a step-by-step approach towards the formal establishment. The First Intergovernmental Meeting held in March 1998 agreed as the first step to implement preparatory-phase activities for two years with the aim to officially establish the EANET in the year 2000. With the successful implementation of the preparatory-phase activities, the Second Intergovernmental Meeting held in October 2000 subsequently agreed to start the activities of the EANET on a regular basis from January 2001. Thailand developed and carried out the national monitoring plan for the preparatory-phase activities through the cooperation of various agencies. Four monitoring sites were included in the preparatory-phase activities of the EANET. Monitoring capacity in Thailand has been gradually built during the preparatory-phase and Thailand is now ready to start monitoring activities of the EANET on a regular basis. Efforts should be continued to study the complex nature of acid deposition phenomena, to quantify the adverse environmental impacts of acid deposition, and to eventually reduce emissions of acid precursors. Strong supports from international and regional organizations are essential for effective implementation of the EANET activities and to address acid deposition problem in the East Asian region.

In studies at 5 degrees C and pH 9.0, poliovirus 1 was inactivated about 15 times more rapidly by free chlorine (FC) in purified water in the presence of 1,262 mg of KCl per liter (approximately 0.0169 M) than in the absence of KCl. In the presence of 526 mg of KCl per liter, the virus was inactivated about seven times more rapidly by FC than in the absence of KCl. At a level of 21 mg/liter, KCl did not significantly potentiate the virucidal activity of FC in purified water. Although poliovirus 1 was inactivated almost three times more rapidly by FC in borate-buffered purified water than in purified water, the presence of the buffer did not alter the extent of potentiation by KCl. Most of FC exists as OCl- at pH 9.0. Tap water has been shown to markedly potentiate the polivirucidal effectiveness of FC at pH 9.0. For the same degree of virucidal potentiation of FC at this pH, a considerably greater quantity of KCl was required in purified water than the total salt content that appeared to be present in the tap water.

Poliovirus 1 was inactivated by free chlorine at pH 9.0 three times more rapidly in boric acid (0.05 M)-NaOH buffer than in purified (carbon-filtered, deionized) water. Thus, at a given concentration of free chlorine, it took three times longer to inactivate the same fraction of the poliovirus in purified water than in the boric acid-NaOH buffer. Conversely, in a given period of time, three times more chlorine was required to inactivate a given percentage of the virus in purified water than in the boric acid-NaOH buffer. Buffers are almost always used to control pH in disinfection studies with free chlorine and with other chlorine compounds also. The use of buffers for pH control in such disinfection studies may distort the resulting data and, at least for waters that contain little salt, may cause serious overestimation of the rates at which viruses are inactivated.

At 5 degrees C, poliovirus 1 was inactivated by free chlorine (FC) at pH 9.0 more than 10 times as rapidly in drinking water as in purified water. Because ions that comprise many salts potentiate the virucidal effectiveness of FC, we believe that ions and possible other substances in the drinking water potentiated the virucidal effectiveness of FC. Since viruses may be much more sensitive to chlorination in drinking waters than laboratory tests in purified waters have heretofore led us to believe, it may be possible to reduce the amounts of FC applied to many water supplies for disinfection and thereby perhaps reduce the quantities of halomethanes and other toxic compounds produced in these supplies by the chlorination process.