Indoor and outdoor formaldehyde concentrations in homes in residential areas in Greater Cairo

Indoor and outdoor measurements of formaldehyde were conducted at seven flats located in residential areas in Greater Cairo, during spring and summer seasons 1999. The mean daytime formaldehyde concentrations in kitchens, bedrooms and living rooms were 89, 100 and 100 ppb, respectively, in the seven flats. Significant positive correlations were found between the concentrations of formaldehyde found in these three rooms. On the other hand, no significant differences were found between the mean formaldehyde concentrations in these three rooms. The maximum mean concentration of formaldehyde (147 ppb) was recorded in a new flat, while the minimum concentration (43 ppb) was observed in an old flat. The maximum hourly and daytime concentrations were 350 and 225 ppb, respectively. Air temperature, relative humidity and the age of the flat are factors affecting the emission and concentration of formaldehyde. The maximum indoor and outdoor formaldehyde concentrations were recorded during the summer season. During the spring, 38% of the samples indicated that the concentration of formaldehyde in the seven flats exceeded 0.1 ppm, the American Society of Heating, Refrigerating, and Air Conditioning Engineers' (ASHRAE) standard; in the summer, this figure increased to 53%.     

Diurnal, seasonal and weekdays–weekends variations of ground level ozone concentrations in an urban area in greater Cairo

Ground level ozone (O3) concentration was monitored during the period of December 2004 to November 2005 in an urban area in Greater Cairo (Haram, Giza). During the winter and summer seasons, nitrogen dioxide (NO2) and nitric oxide(NO) concentrations and meteorological parameters were also measured. The mean values of O3 were 43.89, 65.30, 91.30 and 58.10 ppb in daytime and 29.69, 47.80, 64.00 and 42.70 ppb in whole day (daily) during the winter, spring, summer and autumn seasons, respectively. The diurnal cycles of O3 concentrations during the four seasons revealed a uni-modal peak in the mid-day time, with highest O3 levels in summer due to the local photochemical production. The diurnal variations in NO and NO2 concentrations during the winter and summer showed two daily peaks linked to traffic density. The highest levels of NOx were found in winter. Nearly, 75%, 100%, 34.78% and 52.63% of the mean daytime concentrations of O3 during spring,summer, autumn and the whole year, respectively, exceeded the Egyptian and European Union air quality standards (60 ppb) for daytime (8-h) O3 concentration. About, 41.14% and 10.39% of the daytime hours concentrations and 14.93% and 3.77% of the daily hour concentrations in summer and the whole year, respectively, exceeded the Egyptian standard (100 ppb) for maximum hourly O3 concentration, and photochemical smog is formed in the study area (Haram) during a periods represented by the same percentages. This was based on the fact that photochemical smog usually occurs when O3 concentration exceeds 100 ppb. The concentrations of O3 precursors (NO and NO2) in weekends were lower than those found in weekdays, whereas the O3 levels during the weekends were high compared with weekdays. This finding phenomenon is known as the "weekend effect". Significant positive correlation coefficients were found between O3 and temperature in both seasons and between O3 and relative humidity in summer season, indicating that high temperature and high relative humidity besides the intense solar radiation (in summer) are responsible for the formation of high O3 concentrations.     

贵阳室内氡时空分布特征研究

为了全面分析室内氡的时空分布特征、来源和影响因素,选择了贵阳市不同地理位置的居民住宅、办公场所和公共场所,进行了为期一年的室内氡监测。贵阳市室内氡的平均浓度为(72.7±1.6)Bq/m3,低于室内空气污染国家标准,达标率98.5%。其中居民住宅、办公场所和公共场所的室内氡浓度分别为(93.46±86.93)、(74.68±40.74)、(61±26.93)Bq/m3。研究表明,室内涂料、装修程度和通风效果、小区环境等对室内氡浓度高低有显著影响,室内氡也随季节变化而发生波动。对于居民住宅和公共场所氡的室内外来源相对重要性不同。居民住宅内新楼和旧楼不同楼层室内氡的来源、影响因素和分布特征有显著差异。     

Indoor and outdoor concentrations of PM2.5 trace elements at homes, preschools and schools in Stockholm, Sweden

Fine particles (PM2.5) were sampled indoors and outdoors at 40 sampling sites; in ten classrooms in five schools, at ten preschools and 20 non-smoking homes, in three communities in Stockholm, Sweden, during nine 2-week periods. Each sampling site was sampled twice, once during winter and once during spring. The samples were analysed for elemental concentrations using X-ray fluorescence (XRF) spectroscopy. In all locations significantly higher outdoor concentrations were found for elements that are related to long-range transported air masses (S, Ni, Br and Pb), while only Ti was higher indoors in all locations. Similar differences for S, Br and Pb were found in both seasons for homes and schools. In preschools different seasonal patterns were seen for the long-range transported elements S, Br and Pb and the crustal elements Ti, Mn and Fe. The indoor/outdoor ratios for S and Pb suggest an outdoor PM2.5 particle net infiltration of about 0.6 in these buildings. The community located 25 km from the city centre had significantly lower outdoor concentrations of elements of crustal or traffic origin compared with the two central communities, but had similar levels of long-range transported elements. Significant correlations were found between PM2.5 and most elements outdoors (rs = 0.45-0.90). Copper levels were found to correlate well (rs = 0.64-0.91) to the traffic marker NO2 during both winter and spring in all locations. Copper may be a suitable elemental marker for traffic-related aerosols in health studies in areas without other significant outdoor Cu sources.     

Personal, indoor, and outdoor exposure to VOCs in the immediate vicinity of a local airport

This study measures the effect of emissions from an airport on the air quality of surrounding neighborhoods. The ambient concentrations of benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) were measured using passive samplers at 15 households located close to the airport (indoor, outdoor, and personal), at the end of airport runways and an out-of-neighborhood location. Measurements occurred over a 48-h period during summer 2006 and winter 2006?C2007. The average concentrations were 0.84, 3.21, 0.30, 0.99, and 0.34 ??g/m³ at the airport runways and 0.84, 3.76, 0.39, 1.22, and 0.39 ??g/m³ in the neighborhood for benzene, toluene, ethylbenzene, m-, p-, and o-xylene. The average neighborhood concentrations were not significantly different to those measured at the airport runways and were higher than the out-of-neighborhood location (0.48, 1.09, 0.15, 0.78, and 0.43 ??g/m³, each BTEX). B/T ratios were used as a tracer for emission sources and the average B/T ratio at the airport and outdoors were 0.20 and 0.23 for the summer and 0.40 and 0.42 for the winter, suggesting that both areas are affected by the same emission source. Personal exposure was closely related to levels in the indoor environment where subjects spent most of their time. Indoor/outdoor (I/O) ratios for BTEX ranged from 1.13 to 2.60 and 1.41 to 3.02 for summer and winter. The seasonal differences in I/O ratios reflected residential ventilation patterns, resulting in increased indoor concentrations of volatile organic compounds during winter.     

Nitrogen Dioxide in the Workplace Environment

Concentrations of nitrogen dioxide were measured in shops and car parks over a 19 week period during the winter. For the shops indoor:outdoor ratios varied from 0.34 to 0.54 with an average value of 0.44. NO2 levels ranged from 13 to 38 µg m-3. With little or no contribution from indoor sources, ambient concentrations are the primary factor in determining indoor levels. Concentrations of NO2 in car parks were similar to those measured at the kerb side. Concentrations in the payment booths were higher than those in shops and ranged from 42 to 60 µg m-3. Despite ventilation systems in the payment booths ratios of booth:car park NO2 varied from 0.65 to 0.86.     

Seasonal evaluation of outdoor/indoor air quality in primary schools in Lisbon

The aim of this study was to evaluate the indoor (I) and outdoor (O) levels of NO?, speciated volatile organic compounds (VOCs) and carbonyls at fourteen primary schools in Lisbon (Portugal) during spring, autumn and winter. Three of these schools were also selected to be monitored for comfort parameters, such as temperature and relative humidity, carbon dioxide (CO?), carbon monoxide (CO), total VOCs, and both bacterial and fungal colony-forming units per cubic metre. The concentration of CO? and bioaerosols greatly exceeded the acceptable maximum values of 1800 mg m?3 and 500 CFU m?3, respectively, in all seasons. Most of the assessed VOCs and carbonyls occurred at I/O ratios above unity in all seasons, thus showing the importance of indoor sources and building conditions in indoor air quality. However, it has been observed that higher indoor VOC concentrations occurred more often in the colder months, while carbonyl concentrations were higher in the warm months. In general, the I/O NO? ratios ranged between 0.35 and 1, never exceeding the unity. Some actions are suggested to improve the indoor air quality in Lisbon primary schools.     

Outdoor-indoor air quality in Riyadh: SO2, NH3, and HCHO

A funded research project was conducted during the period July1992 through November 1994. The project was designed to evaluateindoor and ambient air quality in and around buildings of different types and uses in Riyadh, the capital of Saudi Arabia.Thirty intercity buildings and two outercity (background) siteswere carefully selected and monitored for air quality. Ten airpollutants, together with relevant meteorological parameters, were monitored indoor and outdoor at each site continuously andsimultaneously for a period of two weeks covering summer and winter seasons.This article discusses the results obtained for sulfur dioxide (SO₂), ammonia (NH₃) and formaldehyde (HCHO). Results of this investigation revealed that most sites had on the averageexceeded the recommended standards for SO₂ and NH₃ bothindoor and outdoor, with indoor levels being worse than outdoorduring winter time. Several sites also showed high levels of HCHO, with outdoor levels being consistently higher than indoor.Statistical and frequency analyses were performed on the collected data, showing seasonal and sector by sector variability, and outdoor-indoor correlations.     

Airborne particulate matter and BTEX in office environments

Total suspended particulate (TSP), PM(2.5) and BTEX were collected in nine offices in the province of Antwerp, Belgium. Both indoor and outdoor aerosol samples were analysed for their weight, elemental composition, and water-soluble fraction. Indoor TSP and PM(2.5) concentrations ranged from 7-31 microg m(-3) and 5-28 microg m(-3), with an average of 18 and 11 microg m(-3), respectively. Of all the elements analysed in indoor TSP, more than 95% was represented by Al, Si, K, Ca, Fe, Cl and S, accounting for 12% of the TSP by mass. The other elements showed significant enrichment relative to the earth's crust. The water-soluble ionic fraction accounted for almost 30% of the sampled indoor TSP by weight, and was enriched by anthropogenic activities. It was shown that the indoor PM levels varied among the offices, depending on the ventilation pattern, location, and occupation density of the office. Indoor BTEX levels ranged together from 5-47 microg m(-3) and were considerably higher than the corresponding outdoor levels. It was observed that some recently constructed and renovated buildings were clearly burdened with elevated levels for toluene, ethyl benzene, and xylenes, while outdoor air was found to be the main source for BTEX levels at the 'older' offices.     

Periodicities of the radon level in Butte,Montana

Hourly measurements of radon level at four houses in Butte, Montana were analyzed. Previous studies suggestes that there are diurnal cycles, spectral analysis confirms this assertion. Moreover, there are also long term trends and weekly cycles at certain locations. The periodical cycles highly suggest that indoor radon level can be dependent on the ventilation condition of the house and the activities of the residents.The relationship of indoor and outdoor radon level was investigated by cross-spectral analysis. In view of the possible different patterns caused by different seasons, data from the winter and summer are analyzed separately. The results shows that winter and summer data do display different patterns.     

Levels, sources, and health risks of carbonyls in residential indoor air in Hangzhou, China

Concentrations of formaldehyde, acetaldehyde, acetone, propionaldehyde, i-pentanal, and butyraldehyde in residential indoor air in Hangzhou were determined. The mean concentration of the total carbonyl compounds in summer was 222.6 μg/m³, higher than that in winter (68.5 μg/m³). The concentration of a specific carbonyl in indoor air was higher than the outdoor air measurement, indicating the release of carbonyls from the indoor sources. Formaldehyde and acetone were the most abundant carbonyls detected in summer and winter, respectively. Multiple regression analysis indicated that carbonyl concentrations in residential indoor air depended on the age of decoration and furniture, as well as their concentrations in outdoor air. In addition, a primary estimation showed that the health risks of carbonyls in summer were higher than those in winter.     

Ambient site, home outdoor and home indoor particulate concentrations as proxies of personal exposures

Despite strong longitudinal associations between particle personal exposures and ambient concentrations, previous studies have found considerable inter-personal variability in these associations. Factors contributing to this inter-personal variability are important to identify in order to improve our ability to assess particulate exposures for individuals. This paper examines whether ambient, home outdoor and home indoor particle concentrations can be used as proxies of corresponding personal exposures. We explore the strength of the associations between personal, home indoor, home outdoor and central outdoor monitoring site ("ambient site") concentrations of sulfate, fine particle mass (PM(2.5)) and elemental carbon (EC) by season and subject for 25 individuals living in the Boston, MA, USA area. Ambient sulfate concentrations accounted for approximately 70 to 80% of the variability in personal and indoor sulfate levels. Correlations between ambient and personal sulfate, however, varied by subject (0.1-1.0), with associations between personal and outdoor sulfate concentrations generally mirroring personal-ambient associations (median subject-specific correlations of 0.8 to 0.9). Ambient sulfate concentrations are good indicators of personal exposures for individuals living in the Boston area, even though their levels may differ from actual personal exposures. The strong associations for sulfate indicate that ambient concentrations and housing characteristics are the driving factors determining personal sulfate exposures. Ambient PM(2.5) and EC concentrations were more weakly associated with corresponding personal and indoor levels, as compared to sulfate. For EC and PM(2.5), local traffic, indoor sources and/or personal activities can significantly weaken associations with ambient concentrations. Infiltration was shown to impact the ability of ambient concentrations to reflect exposures with higher exposures to particles from ambient sources during summer. In contrast in the winter, lower infiltration can result in a greater contribution of indoor sources to PM(2.5) and EC exposures. Placing EC monitors closer to participants' homes may reduce exposure error in epidemiological studies of traffic-related particles, but this reduction in exposure error may be greater in winter than summer. It should be noted that approximately 20% of the EC data were below the field limit of detection, making it difficult to determine if the weaker associations with the central site for EC were merely a result of methodological limitations.     

Seasonal variability of endotoxin in ambient fine particulate matter

Endotoxin is a toxic, pro-inflammatory compound that has been detected in indoor air and dust in homes and occupational settings, and also in outdoor air. Data on the outdoor sampling of endotoxin are limited. Currently, little is known about the seasonal variation and influence of temperature on outdoor endotoxin levels. In the present study, we report endotoxin levels in fine fraction particulate matter with a 50% aerodynamic cutoff diameter of 2.5 microm (PM2.5) and describe the seasonal variation of endotoxin in Munich, Germany. In 1999-2000, PM2.5 was collected at forty outdoor monitoring sites across Munich. Approximately four samples were collected at each site for a total of 158 samples. Endotoxin concentrations in the PM2.5 samples were determined using the kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay. The geometric mean endotoxin concentration was 1.07 EU mg PM2.5(-1) (95% C.I.: 0.915-1.251) or 0.015 EU m(-3) of sampled air (95% C.I.: 0.013-0.018). Munich endotoxin levels were significantly related to ambient temperature (p < 0.0001) and percent relative humidity (p < 0.0001). Sampling periods with higher average temperatures yielded higher levels of endotoxin in PM2.5 (r = 0.641), whereas decreases in percent relative humidity were associated with increased endotoxin levels in PM2.5 (r = -0.388). Endotoxin levels were significantly higher during the warmer seasons of spring [means ratio (MR): 2.5-2.7] and summer (MR: 2.1-3.0) than during winter. Although temperature and relative humidity do not explain all of the variability in endotoxin levels, their effects were significant in our data set. Temperature effects and seasonal variation of endotoxin should be considered in future studies of outdoor endotoxin.     

Inter-seasonal and spatial distribution of ground-level greenhouse gases (CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript>, N<Subscript>2</Subscript>O) over Nagpur in India and their management roadmap

Ground-level concentrations of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) were monitored over three seasons, i.e., post-monsoon (September–October), winter (January–February), and summer (May–June) for 1 year during 2013–2014 in Nagpur City in India. The selected gases had moderate to high variation both spatially (residential, commercial, traffic intersections, residential cum commercial sites) and temporally (at 7:00, 13:00, 18:00, and 23:00 hours in all three seasons). Concentrations of gases were randomly distributed diurnally over city in all seasons, and there was no specific increasing or decreasing trend with time in a day. Average CO₂ and N₂O concentrations in winter were higher over post-monsoon and summer while CH₄ had highest average concentration in summer. Observed concentrations of CO₂ were predominantly above global average of 400 ppmv while N₂O and CH₄ concentrations frequently dropped down below global average of 327 ppbv and 1.8 ppmv, respectively. Two-tailed Student’s t test indicated that post-monsoon CO₂ concentrations were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). CH₄ concentrations in all seasons were statistically at par to each other. In case of N₂O, concentrations in post-monsoon were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). Average ground-level concentrations of the gases calculated for three seasons together were higher in commercial areas. Environmental management priorities vis a vis greenhouse gas emissions in the city are also discussed.     

Indoor/ambient residential air toxics results in rural western Montana

Indoor and ambient concentrations of 21 volatile organic compounds (including 14 hazardous air pollutants) were measured in the homes of nearly 80 western Montana (Missoula) high school students as part of the 'Air Toxics Under the Big Sky' program during the 2004/2005 and 2005/2006 school years. Target analytes were measured using low flow air sampling pumps and sorbent tubes, with analysis of the exposed samples by thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS). The results reported here present the findings of the first indoor/ambient air toxics monitoring program conducted in a semi-rural valley location located in the Northern Rocky Mountain/Western Montana region. Of all of the air toxics quantified in this study, toluene was found to be the most abundant compound in both the indoor and ambient environments during each of the two school years. Indoor log-transformed mean concentrations were found to be higher when compared with ambient log-transformed mean concentrations at P < 0.001 for the majority of the compounds, supporting the results of previous studies conducted in urban areas. For the air toxics consistently measured throughout this program, concentrations were approximately six times higher inside the student's homes compared to those simultaneously measured directly outside their homes. For the majority of the compounds, there were no significant correlations between indoor and ambient concentrations.     

Assessment of microbiological indoor air quality in an Italian office building equipped with an HVAC system

The purpose of this study was to evaluate the level and composition of bacteria and fungi in the indoor air of an Italian office building equipped with a heating, ventilation and air conditioning (HVAC) system. Airborne bacteria and fungi were collected in three open-space offices during different seasons. The microbial levels in the outdoor air, supply air diffusers, fan coil air flow and air treatment unit humidification water tank were used to evaluate the influence of the HVAC system on indoor air quality (IAQ). A medium–low level of bacterial contamination (50–500 CFU/m³) was found in indoor air. Staphylococcus and Micrococcus were the most commonly found genera, probably due to human presence. A high fungal concentration was measured due to a flood that occurred during the winter. The indoor seasonal distribution of fungal genera was related to the fungal outdoor distribution. Significant seasonal and daily variation in airborne microorganisms was found, underlining a relationship with the frequency of HVAC system switching on/off. The results of this monitoring highlight the role of the HVAC system on IAQ and could be useful to better characterise bacterial and fungal population in the indoor air of office buildings.     

Indoor air pollution levels in public buildings in Thailand and exposure assessment

Levels of pollutants including PM2.5 and PM2.5 composition (black carbon and water soluble ions), SO(2), NO(2), CO, CO(2), and BTEX (benzene, toluene, ethylbenzene, xylene) were monitored for indoor and outdoor air at a university campus and a shopping center, both located in the Northern suburb of Bangkok. Sampling was done during December 2005-February 2006 on both weekdays and weekends. At the university, indoor monitoring was done in two different air conditioned classrooms which shows the I/O ratios for all pollutants to be below 0.5-0.8 during the weekends. However, on weekdays the ratios for CO(2) and most detected BTEX were above 1.0. The concept of classroom occupancy was defined using a function of the student number in a lecture hour and the number of lecture hours per day. Classroom 2, which had a higher occupancy than classroom 1, was characterized by higher concentrations of most pollutants. PM2.5 was an exception and was higher in classroom 1 (37 microg/m(3), weekdays) as compared to classroom 2 (26 microg/m(3), weekdays) which was likely linked to the dust resuspension from the carpeted floor in the former. Monitoring was also done in the shopping mall at three different sites. Indoor pollutants levels and the I/O ratios at the shopping mall were higher than at the university. Levels of all pollutants measured at the car park, except for toluene and CO(2), were the highest. I/O ratios of the pollutants at the mall were above 1.0, which indicates the relatively higher influence of the indoor sources. However, the black carbon content in PM2.5 outdoor is higher than indoor, which suggest the important contribution from outdoor combustion sources such as the traffic. Major sources of outdoor air pollution in the areas were briefly discussed. Exposure modeling was applied using the time activity and measured pollutant concentrations to assess the exposure of different groups of people in the study areas. High exposure to PM2.5, especially for the people working in the mall, should be of health effect concern.     

Measurements of atmospheric aerosol size distributions by co-located optical particle counters

Ambient aerosol number concentrations and size distributions were measured in both indoor and outdoor environments using two identical co-located and concurrently operated optical particle counters (OPCs). Indoor measurements were performed in a research laboratory, whereas two different locations were used for outdoor measurements; the sampling duration exceeded 12 hours and one hour respectively. Results from the two OPCs have been presented for eight size classes between 0.5 and 20 [micro sign]m, represented by central value diameters 0.875, 1.5, 2.75, 4.25, 6.25, 8.75, 12.5 and 15 microm. Overall, for the six indoor and outdoor experiments conducted at different times of day, the mean particle count ratios from the two OPCs for the individual samples showed +/-20% variation for indoor experiments and +/-50% variations for outdoor experiments. Significant random departures of the mean ratios from unity at all size classes were noticed even for indoor sample periods exceeding 20 hours. However, the coefficient of determination (R(2)) for the plots of readings from the two OPCs indicated higher consistency for "fine" particles (0.5-3.5 microm) than for "coarse" particles (10-20 microm), with average R(2) > 0.8 and R(2) < 0.5 respectively. Poisson counting statistics help to explain the divergence in the latter case where number concentrations were very low for the outdoor experiments. However, it cannot explain the divergence for indoor measurements where the concentrations were much higher. Increasing the averaging period reduced the scatter, especially in size classes with low number concentration. However, this procedure may lead to over-smoothing of data for environments with rapidly changing number concentration. These results indicate that, when two such analysers are used for comparative studies, the divergence between their responses may generate significant values of source contribution or deposition flux, even for nominally similar aerosol populations.     

Ground level nitrogen dioxide concentrations in the rural Waikato Valley,New Zealand

Ground level nitrogen dioxide (NO₂) concentrations have been measured for one year over an area of 400 square kilometres in rural New Zealand using an array of 21 sites. Three passive samplers were exposed at each site for intervals of two weeks from August 1989 to August 1990. The exposure sites were centred around the Waikato Valley township of Huntly (population 6900). Important features of the survey area include a 1000 MW thermal power station situated on the outskirts of the town, the Waikato River and State Highway 1, a major north-south traffic route along the valley. The NO₂ concentrations in the survey area ranged from below 0.1 to 10.1 ppb, with an annual average of 1.2 ppb. Seasonal variations indicate summer values about three times lower than those found in the winter. The spatial distribution of NO₂ appears to be related to contributions from State Highway 1.     

Measurement of atmospheric concentrations of common household pesticides: A pilot study

Air concentrations of 28 of the most commonly used household pesticides were measured inside nine homes in Jacksonville, Florida, and compared with corresponding outdoor levels. The households selected were sorted into three categories according to the degree of pesticide indoor usage. Personal air monitoring was also performed on one resident of each household by means of a portable sampler, which was kept with the person at all times. Five of the pesticides were found in the air inside of the majority of the homes at concentrations as high as 15 gm^–3 (average concentrations, 12 ngm^–3 to 2.4 gm^–3). Indoor levels were generally one to two ordrrs of magnitude higher than surrounding outdoor air levels and personal air measurements were within ± 50% of corresponding indoor values. All samples were collected over 24-hr periods on polyurethane foam and analyzed by capillary colum gas chromatography with mass spectrometric and/or electron capture detection.