Exposure to environmental tobacco smoke in restaurants without separate ventilation systems for smoking and nonsmoking dining areas

In this study, the author examined (a) levels of airborne pollutants from environmental tobacco smoke in 8 restaurants, and (b) changes in urinary cotinine and nicotine levels among 97 nonsmoking subjects (i.e., 40 restaurant employees, 37 patrons, and 20 referents). Airborne pollutant levels were significantly lower in the control environments than in the nonsmoking dining rooms in which smoking was not permitted, and the levels were significantly lower in the dining rooms in which smoking was not permitted than in the dining rooms in which smoking was permitted. Levels of urinary cotinine and nicotine increased among subjects in the dining rooms in which smoking was permitted, and the increase was significantly greater in employees than patrons. There was a significant positive correlation between levels of urinary nicotine increase and the levels of airborne nicotine and solanesol. The results of this study support the restriction of smoking to designated areas that have separate ventilation systems, or the prohibition of smoking in restaurants.     

Effectiveness of Clean Indoor Air Ordinances in Controlling Environmental Tobacco Smoke in Restaurants

Clean indoor air (CIA) ordinances in Toledo, Ohio, and Bowling Green, Ohio, regulate smoking in restaurants to protect patrons and employees. Yet complete protection is questionable because the ordinances allow for smoking in certain dining sections. Two restaurants were studied in each city, one smoking and one nonsmoking. Levels of contaminants related to environmental tobacco smoke (ETS)—determined by personal and area air monitoring—in the nonsmoking restaurants were comparable to levels in a control environment. However, levels of ETS-related contaminants in the smoking restaurants, including designated nonsmoking sections, were significantly higher than levels in the control environment. ETS-related contamination of the nonsmoking sections in the smoking restaurants is attributable to direct openings between the smoking and nonsmoking sections. Reasonable protection of employees and patrons against ETS-related contaminants requires strict enforcement of CIA ordinances. Full protection is achievable only with 100% smoke-free policies.     

Effectiveness of clean indoor air ordinances in controlling environmental tobacco smoke in restaurants

Clean indoor air (CIA) ordinances in Toledo, Ohio, and Bowling Green, Ohio, regulate smoking in restaurants to protect patrons and employees. Yet complete protection is questionable because the ordinances allow for smoking in certain dining sections. Two restaurants were studied in each city, one smoking and one nonsmoking. Levels of contaminants related to environmental tobacco smoke (ETS)--determined by personal and area air monitoring-in the nonsmoking restaurants were comparable to levels in a control environment. However, levels of ETS-related contaminants in the smoking restaurants, including designated nonsmoking sections, were significantly higher than levels in the control environment. ETS-related contamination of the nonsmoking sections in the smoking restaurants is attributable to direct openings between the smoking and nonsmoking sections. Reasonable protection of employees and patrons against ETS-related contaminants requires strict enforcement of CIA ordinances. Full protection is achievable only with 100% smoke-free policies.     

Carbon monoxide levels in the breath of smokers and nonsmokers: effect of domestic heating systems.

Breath and ambient (room) carbon monoxide (CO) levels were measured in a random sample of 168 adults in their own homes. The levels of breath CO in the 69 smokers ranged from 3 ppm to over 100 ppm, 74% being above 10 ppm; mean levels in the 99 nonsmokers were lower than in the smokers, 79% being below 6 ppm. In the remaining 21% of nonsmokers with higher breath levels than expected, the ambient CO was also found to be elevated, ranging up to 38 ppm. A close correlation in the nonsmokers was found between the breath and ambient CO levels (r = 0.952, p less than 0.001). The rooms with the elevated ambient CO levels (above 5 ppm) were those which, at the time of testing, were being heated by gas radiant heaters, open fires or stoves. The maximum ambient CO in the rooms of smokers with non CO generating heating was 16 ppm. The results suggest that many people, both smokers and nonsmokers, may be at risk from CO generated by certain domestic heating systems and that nonsmokers are far more likely to be exposed to high levels of CO from these sources than from being in a room with a heavy smoker. Poor ventilation associated with the current trend towards excluding all draughts is likely to exacerbate the situation for both smokers and nonsmokers.     

"Breathing freely" in schools--results and model approaches concerning the air quality in classrooms

Seven schools in Lower Saxony participated in a scientific re-search project measuring the concentration of carbon dioxide (CO2), indoor air temperatures and the relative air humidity in naturally ventilated classrooms on 58 days during the period of one year. The results are as follows: The hygienic reference value of 1500 ppm CO2 (in accordance with the official German regulation DIN 1946-2) was exceeded on 7 days in summer when measurements were taken (32% of all samples in summer) and on 32 days in winter (89% of all samples in winter). The mean CO2-concentration was 1316 ppm, 766 ppm and 1652 ppm in all samples (58 measuring days), summer samples (22 measuring days) and winter samples (36 measuring days), respectively. The mean indoor air temperature was 21.7 degrees C, 22.9 degrees C and 20.9 degrees C. The mean relative humidity was 50.7%, 54.3% and 48.5%. The mean number of persons per classroom (including the teacher) was 25.1, corresponding to a mean volume of 8.5 m3 for each person and a mean area of 2.9 m2 per person. A statistical association of CO2 concentration with season, outdoor temperature and the age of the windows was found. A software programme has been developed for calculating the concentration of CO2 depending on the number of persons and the ventilation rate in a classroom. A 3-level scheme based on CO2 concentration was developed to assess the air quality. The results showed that the classrooms were not ventilated regularly but depending on the outdoor temperature and the season. Deficits concerning all 3 parameters were found. It is very likely that the deficits are not limited to the schools participating in this project. Ventilation and indoor climate deficits might cause health problems and therefore lead to costly measurement programmes. To enable schools to take their own health-related measurements, measuring instruments were purchased which can be loaned to schools in Lower Saxony.     

Indoor air quality in restaurants with and without designated smoking rooms

Indoor air quality in restaurants was studied in two cities in northwest Ohio after clean indoor air ordinances had been enacted. Carbon dioxide and ultrafine particles were measured in two restaurants in Toledo and two restaurants in Bowling Green. One restaurant in each city was smoke free, and one restaurant in each city contained a dedicated smoking room. A smoke free office space was also assessed as a reference site. Measurements were collected with datalogging instrumentation simultaneously in both the designated smoking room, if present, and in the nonsmoking section. For smoke free establishments, datalogging instrumentation was also used. Carbon dioxide levels were elevated in all four restaurants, with only 32% of the measurements meeting the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) criterion level of 1000 ppm. Ultrafine particles currently do not have any formal standard or guideline. Statistically significant differences were evident between all four restaurants and the reference site. The largest differences were found between the two designated smoking rooms and the reference site (p < 0.001), with the mean levels in the smoking rooms up to 43 times higher than in the reference site. The results from this study indicate inadequate fresh air supply in all four restaurants, particularly in the designated smoking rooms, and the possibility that the designated smoking rooms were not containing the environment tobacco smoke, based on the ultrafine particle concentrations measured in the nonsmoking areas of the smoking restaurants.     

Evaluation and determinants of airborne bacterial concentrations in school classrooms

A survey of 39 elementary schools was undertaken to determine indoor air concentrations of bioaerosols within a coastal, temperate climatic zone in British Columbia, Canada. This article reports the results for airborne bacteria. Determinants of exposure were grouped into environmental (outdoor temperature, relative humidity, season, weather), ventilation and comfort parameter (indoor relative humidity, temperature, indoor CO2 concentration, indoor fungal concentration), and occupancy (number of occupants, activity levels, occupancy patterns) variables. Regression modeling was used to evaluate the association between these factors and measured concentrations of indoor mesophilic bacteria. Naturally ventilated rooms (47% of the total rooms surveyed) had higher bacterial counts than mechanically ventilated rooms (geometric mean 325 vs. 166 CFU/m3, respectively, p < 0.001). In univariate analyses, bacterial counts were negatively correlated with supply and exhaust flow rates, air exchange rates, and the percentage of the day that occupants spent quietly sitting at their desks. Analysis of bacterial groups indicated various sources of the bacterial aerosol, with micrococci and staphylococci closely associated with occupancy variables, Bacillus with site and occupancy, and coryneform bacteria with site variables only. Approximately 60% of the variance in the outcome measurement of total bacteria was accountedfor by indoor CO2, lower air exchange rate, the age of the building, signs of current or old moisture stains, room volume, indoor relative humidity, and occupant activity level in a multiple linear regression model, with ventilation factors accounting for 40% of the variance.     

Sick building syndrome in relation to air exchange rate, CO2, room temperature and relative air humidity in university computer classrooms: an experimental study

OBJECTIVE: To study the effects of ventilation and temperature changes in computer classrooms on symptoms in students. METHODS: Technical university students participated in a blinded study. Two classrooms had higher air exchange (4.1-5.2 ac/h); two others had lower (2.3-2.6 ac/h) air exchange. After 1 week, ventilation conditions were interchanged between the rooms. The students reported symptoms during the last hour, on a seven-step rating scale. Room temperature, relative air humidity (RH) carbon dioxide (CO(2)), PM10 and ultra-fine particles (UFP) were measured simultaneously (1 h). Illumination, air velocity, operative temperature, supply air temperature, formaldehyde, NO(2) and O(3) were measured. Multiple logistic regression was applied in cross-sectional analysis of the first answer (N = 355). Those participating twice (N = 121) were analysed longitudinally. RESULTS: Totally 31% were females, 2.9% smokers and 3.8% had asthma. Mean CO(2) was 993 ppm (674-1,450 ppm), temperature 22.7 degrees C (20-25 degrees C) and RH 24% (19-35%). Lower and higher air exchange rates corresponded to a personal outdoor airflow of 7 l/s*p and 10-13 L/s*P, respectively. Mean PM10 was 20 mug/m(3) at lower and 15 mug/m(3) at higher ventilation flow. Ocular, nasal and throat symptoms, breathlessness, headache and tiredness were significantly more common at higher CO(2) and temperature. After mutual adjustment, ocular (OR = 1.52 per 1 degrees C), nasal (OR = 1.62 per 1 degrees C) and throat symptoms (OR = 1.53 per 1 degrees C), headache (OR = 1.51 per 1 degrees C) and tiredness (OR = 1.54 per 1 degrees C) were significantly associated with temperature; headache was associated only with CO(2) (OR = 1.19 per 100 ppm CO(2)). Longitudinal analysis demonstrated that increased room temperature was related to tiredness (P < 0.05). CONCLUSION: Computer classrooms may have CO(2) above 1,000 ppm and temperatures above 22 degrees C. Increased temperature and CO(2) may affect mucosal membrane symptoms, headaches and tiredness. Room temperature was most important. CO(2) associations may partly be temperature effects.     

火锅餐厅的空气质量

目的：了解火免餐厅营业中的空气卫生质量。方法：于冬季选择石嘴山市35家以液化石油气为燃料的火锅餐厅，主要调查通风状况，微小气候及空气卫生质量，并对营业前后不同通风情况下空气中CO浓度进行比较。结果：CO污染最严重，超标率高达63．64％，温，湿度合格率仅20％和12％，雅间关闭窗打开空调及换气扇，点燃火锅30min后CO为34．3mg/m^3，而关闭火锅开门窗10－15min后CO为6．35mg/m^3，就餐者头晕，头痛等不适症状出现率在CO＞15mg/m^3时为70．8％，在CO＜15mg/m^3时仅9．1％，结论：火锅餐厅主要空气污染物为CO。     

Ethylene oxide dispersion from gas sterilizers

Ethylene oxide (EtO) is widely used by the health industry for sterilizing heat-sensitive devices. About 100 000 workers are regularly exposed to this chemical, used in an estimated 10 000 sterilizing units in U.S. health care facilities. Based on recent findings. NIOSh has recommended that EtO be regarded as a potential carcinogen and has urged OSHA to reexamine its present standard of 50 ppm. The ACGIH Notice of Intended Changes for 1982 has proposed reducing the recommended limit from 10 ppm TWA to 1 ppm and considers EtO a suspect carcinogen for man. Because of this increasing concern for its toxicity, it is imperative that the exposures to EtO be assessed, and that all reasonable steps to reduce these exposures be taken. This study demonstrates the effects of local exhaust ventilation, sterilizer chamber temperature, and sterilizer relative humidity in relation to their influence on EtO plume directionality, concentration and duration. Using two Foxboro/Wilks Miran 1A General Purpose Gas Analyzers, EtO concentrations were simultaneously monitored both immediately above and below the sterilizer door during various process runs, at three different types of sterilizers. Sterilizer operating conditions were representative of temperatures (38-54 degrees C (100-130 degrees F)), and relative humidities (30-50%) commonly employed in the sterilization process. The effects of varying local exhaust parameters were observed. Results clearly demonstrated that EtO tends to flow upward when the sterilizer door is opened. In all cases, the highest concentrations were observed at the upper location. Local exhaust ventilation significantly reduced the concentration of EtO observed and lessened the duration for which these levels persisted. Changes in temperature and relative humidity, within the range cited, have not shown any significant differences in EtO evolution patterns, concentrations or duration.     

Indoor air quality assessment of daycare facilities with carbon dioxide,temperature, and humidity as indicators

Poor indoor air quality (IAQ) in daycare facilities affects both attending children and care providers. Incident rates of upper-respiratory-tract infections have been reported to be higher in children who attend daycare. Excessive carbon dioxide (CO2) exposure can cause several health effects and even sudden infant death. For this study, 26 facilities were randomly selected in a Midwestern county of the United States. CO2, room temperature, and relative humidity were used as indicators for IAQ and comfort levels. These IAQ parameters were continuously monitored for eight hours at each facility by a direct-reading instrument that was calibrated before each measurement. More than 50 percent of the facilities had an average CO2 level over the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) standard of 1,000 parts per million (ppm). For temperature and relative humidity, respectively, 42.3 percent and 15.4 percent of facilities were outside of the ASHRAE-recommended comfort zones. The nap-time average CO2 level was about 117 ppm higher than the non-nap-time level. The increment of the nap-time CO2 level in the sleeping-only room over the level in multipurpose rooms was statistically significant (p < .05). According to stepwise multiple regression analysis, nap-time CO2 level was predicted by CO2 level before occupancy, nap-time average temperature, carbon monoxide, and child density (R2 = .83). It is recommended that an appropriate IAQ standard for daycare facilities be established and that children should not be placed in a completely isolated room during nap time.     

Formaldehyde exposure in some educational hospitals of Tehran

This research was conducted to determine formaldehyde exposure of staffs in pathology laboratories, surgery rooms and endoscopy wards in eight large hospitals of Tehran University of Medical Sciences located at Tehran, Iran. Air sampling have been made by both long and short-term methods. Total numbers of samples were 160 for both methods. Nineteen samples of 160 samples were collected as blank in other non-exposed environments such as administrative sections. The mean (SD) levels of formaldehyde in long-term methods were 0.96 (0.74), 0.25 (0.21) and 0.13 (0.18) ppm, at pathology laboratories, surgery rooms and endoscopy wards, respectively. The results of measurements showed that mean (SD) concentration of formaldehyde in one hour sampling at short intervals were 0.83 (0.29), 0.23 (0.16) and 0.75 (0.25) ppm at pathology labs, surgery rooms and endoscopy wards, respectively. There were significant differences in the mean levels of formaldehyde (long-term) at surgery rooms (p < 0.02) and endoscopy wards (p < 0.005) in eight hospitals of this study. It is concluded that the concentration levels of formaldehyde at pathology laboratories exceeded recommended limit which established by the American Conference of Governmental and Industrial Hygienists ACGIH (TLV-C = 0.3 ppm). It is recommended that local exhaust ventilation should be installed to minimize the contact to formaldehyde in the staffs.     

Environmental allergens and irritants in schools: a focus on asthma

As part of the Partners in School Asthma Management Program, environmental data were collected from 385 rooms in 60 elementary schools in southeast Texas, using an Environmental Observation Checklist and a Q-TRAK Indoor Air Quality Monitor. Dust samples for allergen analysis were collected from floors, carpets, and area rugs in 80 classrooms in a subset of 20 schools. CO2 levels > 1,000 ppm were found in 86% of rooms; 69% had indoor humidity above recommended levels. Der p I dust mite allergen levels > 2,000 ng/g were present in 20% of rooms, but only 2.5% of rooms had Der f I mite allergen levels exceeding recommended tolerances. Detectable levels of cockroach allergen (Bla g II) were found in all schools (median 5.5 ng/g), with 10% of rooms over the recommended threshold. Almost two-thirds of classrooms had mold spore counts > 10,000 col/g (median, 14,400 col/g; range, 2,000-52,000 col/g).     

Evaluation of a sampling method for the measurement of occupational exposures to ethylene

In an effort to assess the scope of occupational exposures to ethylene, the Olefins Panel of the American Chemistry Council designed and conducted a research project to develop and apply a sampling and analytical method to measure workplace exposure. The method uses packed Carbosieve S-III thermal desorption tubes (Supelco, Bellefonte, Pa.) with a low sample collection flow rate. The tubes were analyzed by thermal desorption gas chromatography. The methodology was validated for both 15-min short-term exposure limit and 8-hr time-weighted average (TWA) samples in the laboratory prior to the field study. The effects of varying sampling flow rate (2, 5, 10, and 25 mL/min) and temperature (25 and 35 degrees C) on sample breakthrough time were assessed at a constant relative humidity of 90%. Breakthrough times decreased linearly with sampling flow rate and temperature. The optimal sampling flow rate and temperature at 90% relative humidity were 2 mL/ min and 25 degrees C. A full-shift TWA sample can be collected using two tubes for up to 4 hours each at a flow rate of 2 mL/min, while a STEL sample can be collected at 25 mL/min flow rate. The evaluation indicated samples can be stored under ambient conditions for a period up to 14 days without significant sample loss. Field measurements were performed at 14 petrochemical facilities within North America. The mean 8-hour TWA ethylene concentration (71 sample pairs) was 2.6 ppm (range: <0.05 to 2100 ppm). Significant ethylene concentrations were observed for only two of the 73 TWA sample pairs. Each of these two samples was obtained from the same facility, and only one tube of the sample pairs showed a high ethylene concentration (3200 ppm and 4200 ppm, respectively) for the 1600 ppm and 2100 ppm TWA sample. The first tube of each of these two sample pairs showed no detectable levels. Further, 69 of 71 sample pairs had TWA concentrations below 13 ppm. The mean of 26 short-term exposure limit samples was 16 ppm (range: <0.05 to 63 ppm), with only one sample above 50 ppm. The results of this study indicate that airborne concentrations of ethylene can be effectively measured using Carbosieve S-III packed thermal desorption tubes under typical workplace conditions.     

An international survey of indoor air quality,ventilation, and smoking activity in restaurants: a pilot study

During a pilot study of indoor air quality in restaurants, a survey was performed in 34 medium-priced restaurants in six countries in Asia, Europe, and North America using a uniform protocol. The concentration of selected constituents of environmental tobacco smoke (ETS) present in occupied areas was determined during lunch and dinner periods by measuring the levels of four particulate-phase markers and two gas-phase markers. The particulate-phase markers determined were respirable suspended particles, ultraviolet particulate matter, fluorescing particulate matter, and solanesol particulate matter. The gas-phase markers were nicotine and 3-ethenylpyridine (3-EP). Correlation between the markers was investigated to explore an improved monitoring approach. It was concluded that at least one marker in each phase was necessary to describe adequately the ETS load. An assessment was made of the ventilation system in each restaurant, and effective ventilation rates were determined based on CO(2) measurements. Smoking activity was also monitored. These data were used to model nicotine and 3-EP concentrations that resulted in a satisfactory prediction of their levels, especially at the higher concentrations. A total number of 1370 questionnaires were returned by the restaurant patrons in five countries. In some countries, dissatisfaction rates above 20% were observed for draft, freshness of air, and noise. The dissatisfaction rates related to tobacco smoke were less than 20%, which is lower than would be predicted based on measured ETS levels. Based on the results of this international pilot study, recommendations are given for future studies of this type.     

Ambient carbon monoxide levels and acute cardiorespiratory complaints: an exploratory study.

Over a 92-day seasonally excessive period of ambient carbon monoxide (CO), chief cardiorespiratory complaints (CRC) of a nontraumatic origin were identified from each of 8,556 patient encounters at the Emergency Room of Colorado General Hospital. Excessive numbers of CRC were seen above a CO level of 5 ppm for the 24-hour mean and 11 ppm for the one hour mean maximum ambient CO (p less than 0.05 for both). Increasing relative risk was shown by comparing daily numbers of CRC with its mean in two-day trend analyses with both ambient CO measures above and below these thresholds. Other ambient pollutants were generally low during the winter period studies. These findings suggest an association between health effects and lower levels of CO than has been previously reported.     

The impact of maintenance and design for ventilation systems

Ventilation systems need to be designed to include access for cleaning and preventive maintenance. Without such access, the exhaust volume will deteriorate. Because of access difficulties and the many demands on their time, plant managers are sometimes errant in performing proper preventive maintenance. Three surveys measuring workers' exposures to methylene chloride were conducted at the same furniture stripping facility. A new ventilation system was installed for the first survey, resulting in an exhaust volume of 2900 cfm and worker exposure to methylene chloride of 59 ppm (geometric mean). Immediately after the first survey, the gasoline-powered fan was replaced by a smaller capacity electrically powered fan. Deterioration in the ventilation system was seen after seven years. Problems included clogged slots, paint chips and sawdust deposits in plenums, and a loose and frayed fan belt. The second survey indicated a reduction in exhaust volume to 1060 cfm and increased worker exposure to 330 ppm. With the smaller capacity fan still in place, the system was otherwise upgraded to allow for easier access and maintenance was performed. The third survey showed that the ventilation system performance was better (exhaust volume improved to 2080 cfm) and the worker exposures were reduced to 73 ppm. This study shows the benefits of designing for preventive maintenance and the necessity of keeping the ventilation systems clean.     

Perceptions of indoor air quality associated with ventilation system types in elementary schools

With the increased utilization of school buildings on a year-round basis, school indoor air quality has become a national concern. The purpose of this study was to evaluate possible associations between ventilation system type and occupant perception of indoor air quality. Staff (n = 403) from 12 schools completed a self-administered questionnaire. Carbon dioxide (CO2) levels, air exchange rates, and particle counts were also measured for each school. Schools with unit ventilator (UV) systems had the lowest mean CO2 level at 637 ppm, followed by the variable air volume (VAV) systems with 664 ppm, and constant volume (CV) systems with a mean of 703 ppm. Schools with UV systems had the lowest mean air exchange rate at 2.67 air changes per hour (ACH), followed by the VAV system type at 2.80 ACH and the CV system type at 4.61 ACH. Indoor versus outdoor particle ratios were calculated for each ventilation system type. Particles with aerodynamic diameters ranging from 0.1-1.0 microm had a geometric mean ratio ranging from 0.38 to 0.68; particles with aerodynamic diameters ranging from 1-3 microm had ratios ranging from 1.39 to 5.47, and particles with aerodynamic diameters greater than 3 microm had ratios ranging from 3.20 to 14.76. Schools using VAV systems had a significantly lower prevalence of red and watery eyes while schools with UV systems had an elevated prevalence of nasal congestion, sore throat, headache, and dustiness complaints. This increased prevalence of complaints in buildings with UV systems may be due to the increased particulate levels.     

安徽省27家医院洁净手术部综合性能调查

目的了解安徽省各级医疗机构洁净手术部的综合性能达标状况。方法于2009～2011年对安徽省27家医院的191间洁净手术室和391间辅助用房进行尘埃粒子、沉降菌和相关技术指标的现场静态监测。根据《医院洁净手术部建筑技术规范》GB 50333-2002监测并评价。结果Ⅰ级手术室的尘埃粒子数、沉降菌数、压差、温度、相对湿度、噪声、照度、风速等技术指标的合格率分别为96.4%、100.0%、92.9%、96.4%、89.3%、75.0%、64.3%、92.9%。所有洁净手术室的尘埃粒子数、沉降菌数、压差、温度、相对湿度、噪声、照度、风速、换气次数等技术指标的合格率分别为98.4%、100.0%、94.2%、96.9%、93.7%、83.2%、72.5%、92.9%、82.2%。结论安徽省部分医院的洁净手术室的主要洁净指标合格率较高;但Ⅰ级手术室的噪声、照度,其他手术室及辅房的照度、换气次数的合格率较低。     

Indoor air quality of schools in Alexandria City

Poor air quality in schools can affect children's desire and ability to concentrate and learn and may lead to increased rate of absenteeism. This study was carried out with the aim of characterizing and measuring indoor air quality in school buildings, measuring ventilation status and studying the impact of design and environmental parameters on some measured pollutant levels. The study was carried out in some primary schools of Alexandria City. All ventilation rate levels exceeded the ASHRAE standard of 15 cfm/pupil except for a few cases. Badly located and small window area led to air stagnation and low ventilation rates. Levels of TSP greatly exceeded a suggested daily guideline of 150 microg/m3. The highest average levels of TSP were found inside classrooms surrounded by unpaved playground and located near semi rural, commercial and heavy traffic areas, while lowest levels were in classrooms located next to residential areas. The average total bacteria were highest in winter. There was also a slight increase in respiratory symptoms and signs in winter. There was a significant positive correlation between average total, pathogenic and non-pathogenic bacteria with average TSP levels, indoor CO2 levels and relative humidity while a significant negative correlation was observed with ventilation rate and class volume occupied. The average attack rate of respiratory conditions was 1.96 episode per child. Running nose was the highest frequent symptom. Students of first grade, had an incidence rate higher than that among fifth grade students.