Air Quality Surveillance Research Articles

Low-cost quadrotor hardware design with PID control system as flight controller

In designing an Unmanned Aerial Vehicle (UAV), such as quadrotor, sometimes an engineer should consider the required cost that is relatively expensive. As we know, quadrotor is one of robots that very usefull and has several advantages for human needs such as disaster area monitoring, air quality monitoring, area mapping, aerial photography, and surveillance. Thus, designing a rapid quadrotor with low-cost components and simple control system needs to be considered here. This paper presents design and implementation of a quadrotor using relatively low-cost components with Proportional Integral Derivative (PID) control system as its controller. The components used consist of microcontroller, Inertial Measurement Unit (IMU) sensor, Brushless Direct Current (BLDC) motor, Electronic Speed Control (ESC), remote control unit, battery, and frame. These components can be easily found in the electronic markets, especially in Indonesia. As an addition, this paper also describes PID control system as flight controller. A simple economic analysis is presented to clarify the cost in designing this quadrotor. Based on experimental testing result, the quadrotor able to fly stably with PID controller although there still overshoot at the attitude responses.

Transboundary transport of biomass burning aerosols and photochemical pollution in the Orinoco River Basin

The “Llanos” is a complex savanna ecosystem that occupies most of the Orinoco River Basin, from the Colombian Andes foothills almost to the Orinoco River Delta at the Atlantic Ocean in Venezuela. It undergoes periodic, human-induced and natural biomass burning during the dry season, which is shorter in Colombia. Northeast trade winds that prevail during the dry season can transport biomass burning plumes from Venezuela to Colombia, even during the Colombian Llanos wet season. Our analysis is based on ambient air measurements at two middle size Colombian Llanos cities located 266 km apart, during April–May 2015, right after the end of the dry season in Colombia, but when there was still high fire activity in Venezuela. Observed 24-h averaged PM10 concentrations in the two cities were unexpectedly high (up to 112 μg/m3), particularly when considering their relatively small size, and low industrial and road traffic activity, and their trends were very similar, which indicates a common remote source. Ozone enhancements of up to ∼94 ppbv (7-day average) were also observed. A reasonably good correlation was found between PM10 and a proxy of fire emissions within footprints calculated using the Stochastic Time-Inverted Lagrangian Transport model. There is currently no permanent air quality surveillance system in the Colombian Llanos. Our findings imply that such a system should be established and incorporate near real-time, synoptic scale biomass burning remote sensing information.

Traffic regulation and environmental pollution by particulate material (2.5 and 10), sulfur dioxide, and nitrogen dioxide in Metropolitan Lima, Peru

To assess the change in environmental levels of PM2.5, PM10, SO2, and NO2, after the application of a traffic regulation plan in Abancay Avenue between the years 2013-2015 vs. to 2007-2009, and comparing it against two other avenues, in which no traffic regulation was implemented: Guillermo de La Fuente Avenue in the district of Comas and Cesar Vallejo Avenue in El Agustino. Environmental data were collected by three air monitors from the Ministry of Health's Environmental Health and Food Safety General Directorate (Dirección General de Salud Ambiental e Inocuidad Alimentaria) that are part of the Air Quality Surveillance network of the city of Lima. The beta coefficient of the linear regression allowed to assess change in the concentration of each pollutant. The traffic regulation plan of Abancay Av. reduced the levels of PM2.5 by 62%; 55% for PM10 levels; 65% for the NO2 levels, and 82% for the SO2 levels. In the other two avenues assess, this reduction was not observed. A significant reduction in PM2.5 (β: -53.11 μg/m3; 95% CI: -63.92 to -42.30), PM10 (β: -47.99 μg/m3; 95% CI: -62.61 to -33.37), NO2 (β: -41.71 μg/m3; 95% CI: -48.18 to -35.23), and SO2 (β: -28.59 μg/m3; 95% CI: -35.23 to -21.95) was observed in Abancay Av., with respect to the other two avenues, after the traffic regulation plan was implemented. Traffic regulation can contribute to the continuous reduction of different air pollutants. The expansion of this measure could improve air quality and the health status of the residents of Lima.

Association between air pollution and suicide: a time series analysis in four Colombian cities

BackgroundRecent epidemiological studies have suggested that air pollution could be associated with suicide. However, other studies have criticized these results for being analytically weak and not taking into account potential confounding factors. As such, further studies examining the relationship under diverse contexts are necessary to help clarify this issue. This study explored the association between specific air pollutants (NO2, SO2, PM10, PM2.5, CO and O3) and suicide incidence in four Colombian cities after adjusting for climatic variables and holidays.MethodsA time series of daily suicides among men and women living in Bogota, Medellin, Cali and Bucaramanga was generated using information from the National Administrative Department of Statistics (DANE) for the years 2011–2014. At the same time, the average daily concentration of each air pollutant for each city was obtained from monitoring stations belonging to the National Air Quality Surveillance System. Using this information together, we generated conditional Poisson models (stratified by day, month and year) for the suicide rate in men and women, with air pollutants as the principal explanatory variable. These models were adjusted for temperature, relative humidity, precipitation and holidays.ResultsNo association was found between any of the examined pollutants and suicide: NO2 (IRR:0.99, 95% CI: 0.95–1.04), SO2 (IRR:0.99, 95% CI: 0.98–1.01), PM10 (IRR:0.99, 95% CI:0.95–1.03), PM2.5 (IRR:1.01, 95% CI: 0.98–1.05), CO (IRR:1.00, 95% CI:1.00–1.00) and O3 (IRR: 1.00, 95% CI: 0.96–1.04). In the same way, no association was found in stratified models by sex and age group neither in lagged and cumulative effects models.ConclusionsAfter adjusting for major confounding factors, we found no statistically significant association between air pollution and suicide in Colombia. These “negative” results provide further insight into the current discussion regarding the existence of such a relationship.

Climate Change, Air Quality and Urban Health: Evidence from Urban Air Quality Surveillance System in 161 Cities of China 2014

Air pollution has posed a serious public health issue in China. In the study, we aimed to examine the burden of air pollution and its association with climate factors and total mortality. City-level daily air quality index (AQI) data in 161 cities of China in 2014, and meteorological factors, socioeconomic status and total morality were obtained from China environmental, meteor-ology and healthcare agencies. Linear regression, spatial autocorrelation analysis and panel fixed models were applied in data analysis. Among 161 cities, monthly average AQI was significantly different by seasons and regions. The highest average AQI was in winter, and the lowest in summer. A significant clustering distribution of AQI by cities was observed, with the highest AQI in north China (22 cities, mean = 117.36). Among the 161 cities, 5 cities (3%) had AQI > 150 (e.g., moderate polluted reference value), and 50 cities (31.1%) had AQI between 100 and 150 (slightly polluted value). Heat index, precipitation and sunshine hours were negatively and significantly, but air pressure was positively correlated with AQI. Cities with higher AQI concentrations had higher total mortality than those with lower AQI. This AQI-mortality association remained significant after adjustment for socioeconomic status. In conclusion, the study highlights the burden and seasonal, regional and areas variations in air pollution across the nation. Air pollution is estimated to account for more than 4% of the urban health inequality in total mortality in China.

Acute effect of air pollutants (carbon monoxide and ozone) on myocardial infarction mortality in Ningbo

Objective: To explore the effect of carbon monoxide (CO) and ozone (O(3)) in the air on the myocardial infarction mortality in Ningbo, Zhejiang province, from 2011 to 2015. Methods: The data of daily air quality surveillance and the causes of deaths in Ningbo from January 1, 2011 to December 31, 2015 were collected and the time series study using a generalized additive model was conducted to evaluate the relationship between the mortality of myocardial infarction and the air pollutants after adjustment for the long-term trend of death, weather conditions," days of the week" and other confounding factors. Results: The daily average concentrations of CO and O(3) in Ningbo during 2011-2015 were 0.90 (0.02-3.31) mg/m(3) and 82.78 (4-236) μg/m(3), respectively. A total of 5 388 myocardial infarction deaths occurred, with a daily average of 3 deaths. In single-pollutant model, an increase of 0.1 mg/m(3) in average concentration of CO could increase the risk of myocardial infarction mortality by 1.06% (95% CI: 0.29%-1.93%) in general population, and by 1.26% (95% CI:0.28%-2.24%) in aged people aged ≥65 years in lagged 6 days, but the influence was not significant in people aged <65 years. The influence had no significant difference in males, but it increased the risk of myocardial infarction mortality by 1.77% in females (95% CI: 0.44%-3.13%). In multi-pollutant model, CO did remain robust after adjusting for other co-pollutants. Whereas the effect of O(3) had no significant influence. Conclusion: These findings suggested that the increased risk of daily myocardial infarction mortality was associated with the increase of CO concentration, but no such association was found for O(3) in Ningbo.

Microbiological Surveillance of Operation Theatres: Five Year Retrospective Analysis from a Tertiary Care Hospital in North India.

Introduction:Microbiological contamination of air and environment in the operation theaters (OTs) are major risk factor for surgical site and other hospital-associated infections.Objectives: The aim was to identify bacterial colonization of surfaces and equipment and to determine the microbial contamination of air in the OTs of a tertiary care hospital.Materials and Methods:Five years (January 2010–December 2014) retrospective analysis of the data obtained from routine microbiological surveillance of the five OTs of the hospital was done. Surface samples were taken with wet swabs from different sites and equipment. Bacterial species were isolated and identified by conventional methods. Air quality surveillance of OTs was done by settle plate method.Results: A total of 4387 samples were collected from surfaces and articles of various OTs. Out of these only 195 (4.4%), samples showed bacterial growth and yielded 210 isolates. The predominant species isolated was Bacillus with 184 (87.6%) isolates followed by coagulase-negative Staphylococcus 17 (8.1%), Staphylococcus aureus 6 (2.9%), and Enteroccoccus spp. 3 (1.4%). Analysis of the OT air samples showed least colony forming unit (cfu) rate of air (27 cfu/m3) in ophthalmology OT and highest rate of 133 cfu/m3 in general surgery OT.Conclusion:The study shows that OTs of our hospital showed a very low bacterial contamination rate on surface swabbing and a cfu count per m3 of air well within permissible limits.

Spatial-Temporal Analysis of Air Pollution, Climate Change, and Total Mortality in 120 Cities of China, 2012-2013.

China has had a rapid increase in its economy over the past three decades. However, the economic boom came at a certain cost of depleting air quality. In the study, we aimed to examine the burden of air pollution and its association with climatic factors and health outcomes using data from Chinese national and city-level air quality and public health surveillance systems. City-level daily air pollution index (API, a sum weighted index of SO2, NO2, PM10, CO, and Ozone) in 120 cities in 2012 and 2013, and its association with climate factors were analyzed using multiple linear regression analysis, spatial autocorrelation analysis, and panel fixed models. City-level ecological association between annual average API and total mortality were examined using univariate and partial correlation analysis. Sensitivity analysis was conducted by taking the consideration of time-lag effect between exposures and outcomes. The results show that among the 120 cities, annual average API significantly increased from 2012 to 2013 (65.05 vs. 75.99, p < 0.0001). The highest average API was in winter, and the lowest in summer. A significantly spatial clustering of elevated API was observed, with the highest API in northwest China in 2012 and with the highest in east China in 2013. In 2012, 5 (4%) of the 120 cities had ≥60 days with API >100 (defined as “slightly polluted”), however, it increased to 21 cities (18%) that experienced API >100 for ≥60 days in 2013. Furthermore, 16 cities (13%) in 2012 and 35 (29%) in 2013 experienced a maximum API >300 (defined as “severely polluted”). API was negatively and significantly correlated with heat index, precipitation, and sunshine hours, but positively with air pressure. Cities with higher API concentrations had significantly higher total mortality rates than those with lower API. About a 4–7% of the variation in total mortality could be explained by the difference in API across the nation. In conclusion, the study highlights an increased trend of air pollution from 2012 to 2013 in China. The magnitude of air pollution varied by seasons and regions and correlated with climatic factors and total mortality across the country.

Method validation and quality assurance of an ICP-MS protocol for the evaluation of trace and major elements in ambient aerosol samples and application to an air quality surveillance network

This study presents the results of a quality assurance evaluation program applied to the method routinely used for the evaluation of a large elemental profile in aerosol samples from the air quality surveillance network of Extremadura, Spain, where low pollution levels are usually encountered. A critical evaluation of the most relevant analytical steps is presented, including long-term blank values evaluation, limits of detection, certified reference material recoveries, method uncertainty and results of comparison studies for gravimetric and trace element analysis. Results obtained at the air quality network of Extremadura for the gravimetric and multielemental analysis are presented for the 2008 campaign.

Aerosol distribution during open suctioning and long-term surveillance of air quality in a respiratory care center within a medical center.

The investigation of hospital air quality has been conducted in wards, ICUs, operating theaters, and public areas. Few studies have assessed air quality in respiratory care centers (RCCs), especially in mechanically ventilated patients with open suctioning. The RCC air quality indices (temperature, relative humidity, levels of CO2, total volatile organic compounds, particulate matter [PM], bacteria, and fungi) were monitored over 1 y. The air around the patient's head was sampled during open suctioning to examine the probability of bioaerosol exposure affecting health-care workers. This investigation found that the levels of indoor air pollutants (CO2, PM, bacteria, and fungi) were below the indoor air quality standard set by the Taiwan Environmental Protection Agency. Meanwhile, the levels of total volatile organic compounds sometimes exceeded the indoor air quality standard, particularly in August. The identified bacterial genera included Micrococcus species, Corynebacterium species, and Staphylococcus species, and the predominant fungal genera included yeast, Aspergillus species, Scopulariopsis species, and Trichoderma species. Additionally, airborne PM2.5, PM1, and bacteria were clearly raised during open suctioning in mechanically ventilated patients. This phenomenon demonstrated that open suctioning may increase the bacterial exposure risk of health-care workers. RCC air quality deserves long-term monitoring and evaluation. Health-care workers must implement self-protection strategies during open suctioning to ensure their occupational health and safety in health-care settings.

Regional dust storm modeling for health services: The case of valley fever

On 5 July 2011, a massive dust storm struck Phoenix, Arizona (USA), raising concerns for increased cases of valley fever (coccidioidomycosis, or, cocci). A quasi-operational experimental airborne dust forecast system predicted the event and provides model output for continuing analysis in collaboration with public health and air quality communities. An objective of this collaboration was to see if a signal in cases of valley fever in the region could be detected and traced to the storm – an American haboob. To better understand the atmospheric life cycle of cocci spores, the DREAM dust model (also herein, NMME-DREAM) was modified to simulate spore emission, transport and deposition. Inexact knowledge of where cocci-causing fungus grows, the low resolution of cocci surveillance and an overall active period for significant dust events complicate analysis of the effect of the 5 July 2011 storm. In the larger context of monthly to annual disease surveillance, valley fever statistics, when compared against PM10 observation networks and modeled airborne dust concentrations, may reveal a likely cause and effect. Details provided by models and satellites fill time and space voids in conventional approaches to air quality and disease surveillance, leading to land–atmosphere modeling and remote sensing that clearly mark a path to advance valley fever epidemiology, surveillance and risk avoidance.

Satellite-based PM concentrations and their application to COPD in Cleveland, OH.

A hybrid approach is proposed to estimate exposure to fine particulate matter (PM(2.5)) at a given location and time. This approach builds on satellite-based aerosol optical depth (AOD), air pollution data from sparsely distributed Environmental Protection Agency (EPA) sites and local time-space Kriging, an optimal interpolation technique. Given the daily global coverage of AOD data, we can develop daily estimate of air quality at any given location and time. This can assure unprecedented spatial coverage, needed for air quality surveillance and management and epidemiological studies. In this paper, we developed an empirical relationship between the 2 km AOD and PM(2.5) data from EPA sites. Extrapolating this relationship to the study domain resulted in 2.3 million predictions of PM(2.5) between 2000 and 2009 in Cleveland Metropolitan Statistical Area (MSA). We have developed local time-space Kriging to compute exposure at a given location and time using the predicted PM(2.5). Daily estimates of PM(2.5) were developed for Cleveland MSA between 2000 and 2009 at 2.5 km spatial resolution; 1.7 million (∼79.8%) of 2.13 million predictions required for multiyear and geographic domain were robust. In the epidemiological application of the hybrid approach, admissions for an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) was examined with respect to time-space lagged PM(2.5) exposure. Our analysis suggests that the risk of AECOPD increases 2.3% with a unit increase in PM(2.5) exposure within 9 days and 0.05° (∼5 km) distance lags. In the aggregated analysis, the exposed groups (who experienced exposure to PM(2.5) >15.4 μg/m(3)) were 54% more likely to be admitted for AECOPD than the reference group. The hybrid approach offers greater spatiotemporal coverage and reliable characterization of ambient concentration than conventional in situ monitoring-based approaches. Thus, this approach can potentially reduce exposure misclassification errors in the conventional air pollution epidemiology studies.

Temporal variation in airborne microbial populations and microbially-derived allergens in a tropical urban landscape

The microbial component of outdoor aerosols was assessed along a gradient of urban development from inner-city to rural in the seasonal-tropical metropolis of Hong Kong. Sampling over a continuous one-year period was conducted, with molecular analyses to characterize bacterial and eukaryal microbial populations, immuno-assays to detect microbially-derived allergens and extensive environmental and meteorological observations. The data revealed bio-aerosol populations were not significantly impacted by the level of urban development as measured by anthropogenic pollutants and human population levels, but instead exhibited a strong seasonal trend related to general climatic variables. We applied back-trajectory analysis to establish sources of air masses and this allowed further explanation of urban bio-aerosols largely in terms of summer-marine and winter-continental origins. We also evaluated bio-aerosols for the potential to detect human health threats. Many samples supported bacterial and fungal phylotypes indicative of known pathogenic taxa, together with common indicators of human presence. The occurrence of allergenic endotoxins and beta-glucans generally tracked trends in microbial populations, with levels known to induce symptoms detected during summer months when microbial loading was higher. This strengthens calls for bio-aerosols to be considered in future risk assessments and surveillance of air quality, along with existing chemical and particulate indices.

English

BACKGROUND: Air as a means of nosocomial transmission has always remained as a cause of concern for health care providers and especially personnel involved in infection control activities. Although there are no uniform consensus on either the standards for surveillance, methodology for monitoring or the levels of acceptable contamination, it still remains a fact that we need to have some criteria to monitor air quality in atleast the critical care areas like the operation theatres. METHODOLOGY: Air quality surveillance in the operation theatres was performed simultaneously using the settle plate technique and an air sampling device. A total of 9 operation theatres were subjected to 4 surveillance cycles with a minimum of 2 recordings in each theatre following standard protocols and accepted method used to calculate bioburden. RESULTS: A comparison was made between the two methods using the data available with 72 recordings . In the settle plate technique, the mean cfu /mm3 was found to be 17.11 and 22cfu/mm3 at less than 30cm and at a point more than 30cms of the operating table where as the corresponding means using the air sampler was137.83 and 164.11cfu/mm3 respectively which showed considerable statistical significance . CONCLUSION : The use of an air sampler would be more appropriate in monitoring the air quality in critical care areas ensuring a more stringent method of quality check without compromising on the the standard accepted norms and addressing the issue of patient safety with reference to infection prevention .

Detection of isocyanates and polychlorinated biphenyls using proton transfer reaction mass spectrometry

Isocyanates are highly reactive species widely used in industry. They can cause irritation of the eyes, trigger asthma, etc. Polychlorinated biphenyls (PCBs) were widely used in electrical equipments like capacitors and transformers in the last century and are still present in the environment today. PCBs are known to cause cancer and to affect the immune, reproductive, nervous and endocrine systems. Therefore, there is a need for a simple, rapid and reliable analytical method for the detection of traces of isocyanates and of PCBs. The data presented in this paper were obtained using a proton transfer reaction (PTR) time-of-flight mass spectrometer and a high sensitivity PTR quadrupole mass spectrometer. We also utilized a recently developed direct aqueous injection (DAI) inlet system for proton transfer reaction mass spectrometry (PTR-MS) instruments that allows the analysis of trace compounds in liquids. We detected four isocyanates in the headspace above small sample quantities and investigated their fragmentation pathways to obtain a fundamental understanding of the processes involved in proton transfer reactions and also to determine the best operating conditions of the PTR-MS instruments. In addition, nine PCBs were unambiguously identified via their exact mass and isotopic distribution and detected in different concentration levels via direct injection of the liquid. Utilizing recent developments and improvements in PTR-MS, we can rapidly detect two important environmental pollutant compound classes (isocyanates and PCBs) at high accuracy and without any sample preparation. In this paper, we provide proof of the detection of traces of isocyanates and PCBs in air and also of PCBs in liquids. These results could be used for the development of a real-time monitoring device for industrial waste, polluted air or water quality surveillance.

Ambient Air Quality Surveillance and Indexing in and around Mining Clusters in Western Kachchh Region, Gujarat, India

Generation of baseline information about ambient air quality of any given region assumes significance, when the area is 1) an active mine site, 2) proposed to be mined out in future, and 3) industrialization in the area is in fast pace. Ambient air quality monitoring (with respect to SPM, RPM, SO2, NOx and CO) was carried out in and around two mining complexes in western parts of Kachchh district in Gujarat to generate baseline air quality status of the area. This area has two major mine complexes and various large scale industrial projects (thermal power plants, cement plants and several ports and jetties) are also in pipeline. Ambient air sampling was carried out in eight locations within five km radial distance from two major mine sites, i.e. Panandhro and Mata-na-Madh, with four locations for each mine site. Air Quality Indexing was done for all the locations, since it is a simplest way for the prediction of ambient air quality status of any region with respect to industrial, residential and rural areas. Of the eight locations studied the air quality for six locations fell under fairly clean (Light Air Pollution, AQI 25-50) category, while the rest (rural areas in the region), had relatively better air quality and fell under clean (Clean Air, AQI 10-25) category.

Atmospheric pollution in an urban environment by tree bark biomonitoring – Part II: Sr, Nd and Pb isotopic tracing

The harmful effect of manmade particles on natural processes and human health is documented by a large number of studies showing a positive correlation between particulate matter (PM) concentration and health effects. Diminution of this health risk necessitates among others the precise knowledge of the particle sources, their physical and chemical properties and their dissemination in the environment. Pb isotope ratios have been successfully used during the past decades as tracers of anthropogenic Pb disseminated in the biosphere. Here we show that tree bark biomonitoring with lead (Pb), strontium (Sr) and neodymium (Nd) isotope ratios as tracers allow a thorough analysis of the impacts of industrial and other anthropogenic emissions on the urban environment. This is the first comprehensive multi-isotope tracer study of atmospheric pollution in an urban environment allowing to identify and to integrate the different plume paths of emissions in a digital map system. This innovative approach might become an important tool for environmental management and policy-making processes dealing especially with risks and surveillance of air quality in the urban environment.

Study of the correlation between the near-ground PM 10 mass concentration and the aerosol optical depth

This work aims to analyze the relationship between in situ measurements of PM 10 mass concentrations near the ground and daily mean Aerosol Optical Depth (AOD) values. Measurements were performed with sun-photometers part of the Aerosol Robotic Network (AERONET) for AOD, and low-volume samplers near the ground for in situ PM 10 mass concentrations. The analysis was applied for some periods of 2007 and 2009. It is known that several factors like aerosol vertical distribution or hygroscopic growth factor could affect the link between PM 10 ground measurements and AOD. Using a new filtering condition, our linear regression analysis results have shown a significant correlation coefficient, around 0.70. It may be concluded that the columnar optical observation can be transferred to the near-surface conditions with a rather high degree of confidence. This study showed that it is possible to use sun photometric measurements to improve existent air quality surveillance or to extend their spatial coverage.

Retrieval of aerosol mass load (PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt;) from MERIS/Envisat top of atmosphere spectral reflectance measurements over Germany

Abstract. Results of a new methodology for retrievals of surface particulate matter concentration (PM10) from satellite reflectance measurements over Germany are presented in this paper. The retrieval derives effective radii from Ångström-α exponents and benefits from the fitting of a smooth spectral slope from seven MERIS spectrometer channels. Comparisons with ground measurements from the air quality surveillance show standard deviations of 33.9% with −18.9% bias over Hamburg. Over rural sites a standard deviation of 17.9% (bias 12.9%) is reached. We discuss critically limitations and potential applications of the retrieval. Additionally, we talk about the aspects at comparing of retrieved particulate matter with ground station measurements.

Long-term surveillance of air quality in medical center operating rooms

Maintenance of adequate indoor air quality (IAQ) in operating rooms (ORs) is critical to the prevention of nosocomial infection in hospitalized patients. This study evaluated the characteristics of IAQ in various ORs in a medical center. Air temperature, relative humidity, carbon dioxide (CO(2)), particulate matter (PM), and bacterial concentrations were monitored in the ORs, and monthly variations were noted. The mean CO(2) concentrations in the ORs were lower than the suggested level (600 ppm average over 8 hours) set by Taiwan's Environmental Protection Agency. Positive relationships were found among the number of persons, temperature (Spearman's rho coefficient [r(s)] = 0.19; P < .01), and CO(2) concentration (r(s) = 0.34; P < .01) in the OR. Bacterial concentration was significantly associated with PM level when adjusted for OR category and the number of persons in the room. Gram-positive bacteria (eg, Bacillus spp, Micrococcus spp, Staphylococcus spp) were frequently found in the monitored ORs. The IAQ in the ORs varied significantly from month to month. The number of persons in the OR affected IAQ, and a decreased PM level might indicate reduced microbial contamination in the OR.