Average Carbon Monoxide Concentrations Research Articles

The effect of São Paulo's smoke-free legislation on carbon monoxide concentration in hospitality venues and their workers

BackgroundStudies have shown that there is no safe level of secondhand smoke (SHS) exposure and there is a close link between SHS and the risk of coronary heart disease and...

Prediction of tropospheric ozone concentrations: Application of a methodology based on the Darwin’s Theory of Evolution

This study aims to predict the next day hourly average tropospheric ozone (O 3) concentrations using genetic programming (GP). Due to the complexity of this problem, GP is an adequate methodology as it can optimize, simultaneously, the structure of the model and its parameters. It is an artificial intelligence methodology that uses the same principles of the Darwinian Theory of Evolution. GP enables the automatic generation of mathematical expressions that are modified following an iterative process applying genetic operations. The inputs of the models were the hourly average concentrations of carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO 2) and O 3, and some meteorological variables (temperature – T; solar radiation – SR; relative humidity – RH; and wind speed – WS) measured 24 h before. GP was also applied to the principal components (PC) obtained from these variables. The analysed period was from May to July 2004 divided in training and test periods. GP was able to select the most relevant variables for prediction of O 3 concentrations. The original variables, T, RH and O 3 measured 24 h before were considered significant inputs for prediction. The selected PC had also important contributions of the same variables and of NO 2. GP models using the original variables presented better performance in training period and worse performance in test period when compared with the models obtained using PC. The results achieved using the GP methodology demonstrated that it can be very useful to solve several environmental complex problems.

Air Pollution in Accra Neighborhoods: Spatial, Socioeconomic, and Temporal Patterns

This study examined the spatial, socioeconomic status (SES), and temporal patterns of ambient air pollution in Accra, Ghana. Over 22 months, integrated and continuous rooftop particulate matter (PM) monitors were placed at a total of 11 residential or roadside monitoring sites in four neighborhoods of varying SES and biomass fuel use. PM concentrations were highest in late December and January, due to dust blown from the Sahara. Excluding this period, annual PM(2.5) ranged from 39 to 53 microg/m(3) at roadside sites and 30 to 70 microg/m(3) at residential sites; mean annual PM(10) ranged from 80 to 108 microg/m(3) at roadside sites and 57 to 106 microg/m(3) at residential sites. The low-income and densely populated neighborhood of Jamestown/Ushertown had the single highest residential PM concentration. There was less difference across traffic sites. Daily PM increased at all sites at daybreak, followed by a mid-day peak at some sites, and a more spread-out evening peak at all sites. Average carbon monoxide concentrations at different sites and seasons ranged from 7 to 55 ppm, and were generally lower at residential sites than at traffic sites. The results show that PM in these four neighborhoods is substantially higher than the WHO Air Quality Guidelines and in some cases even higher than the WHO Interim Target 1, with the highest pollution in the poorest neighborhood.

Applicability of biogas digestate as solid fuel

Biogas digestate is a byproduct in biogas plants. Using the dried digestate as solid fuel seems to be a promising alternative. Objectives were to verify whether digestate from biogas plants is suitable as a solid biomass fuel and to classify the digestate according to current regulations for biofuels. Combustion experiments in a biomass combustion facility were carried out to ascertain both, emissions and combustion behavior. Two different digestates were used as test fuel and pressed into pellets. Net calorific value of digestate pellets were between 15.8 MJ/kg and 15.0 MJ/kg with water content of 9.2% and 9.9%. Ash content was between 14.6% and 18.3%, with softening temperature between 1090 °C and 1110 °C. Major compounds of ash were calcium 13.6–17.0%, phosphorous 20.4–26.7%, silicon 18.0–30.4% and potassium with 8.5–15.5%. The average concentration of carbon monoxide was between 104 mg/m 3 and 275 mg/m 3 and 334–398 mg/m 3 of nitrogen oxides. Average dust concentration of 100–106 mg/m 3 has been detected, which was reduced to 40–43 mg/m 3 by using an electric filter. Chemical composition and physical properties of digestate fuel pellets depend on the blend of substrates used as feedstock for biogas production. The digestates investigated in this study can be recommended as a fuel for combustion. The calorific value, the ash properties and the emissions allow their use in the investigated solid biomass combustion unit. Further investigations are required to cover a broader range of digestates and combustion techniques.

Cooking as a source of indoor air pollution in rural areas of Tanzania

This study was concerned with the assessment of the contribution of cooking fuelwood, charcoal and kerosene to indoor air pollution in households in Msangani, Chahua and Kazimzumbwi villages in the Coast Region, Tanzania. It has also assessed the performance of Single Compartment Model in predicting indoor pollution levels under Tanzania conditions. The methods used in this study were household survey, measurements, and observation. The pollutants measured were Carbon monoxide (CO), Sulphur dioxide (SO2) and Nitrogen oxides (NOX) using a combustion analyzer CA-6200-CALc manufacured by RAECO of USA, and Suspended Particulate Matter (SPM) using a filter and vacuum pump. It was observed that 97.3% of the 112 families surveyed utilized simple “three stones” fires for cooking. Other observed cooking facilities in the study areas were charcoal stoves and kerosene stoves. The overall pattern shows that the population in the three villages spent about 76.8% of their time indoors. The hourly indoor average SPM levels during cooking period ranged from 13571 mg/m3 to 305798 mg/m3. Compared with SPM levels recorded in similar studies, these values were much higher, and may contribute to health problems observed in the study areas. The CO concentrations before cooking, for households that use fuel wood, exceeded the WHO hourly standard of 30 mg/m3 in 69.4 % of the surveyed households, while the concentrations for those households using charcoal and kerosene were zero. The overall average CO concentrations in mg/m3 at all households during cooking were 325 ± 211 and 148 ± 44 when fuelwood and charcoal biomass were used respectively. The measured values of CO were above the recommended WHO guidelines with an hourly objective value of 30 mg/m3. A Single Compartment Model provided a satisfactory approximation of the measured CO concentrations with an average ratio of measured/modelled CO concentration at 1.1± 0.3. The study recommends improvement to the ventilation system including the provision of an adequate number of windows and installation of chimneys for removal of combustion pollutants from indoor environment. © 2009 International Formulae Group. All rights reserved. Key words : Biomass; cooking; fuelwood; indoor air pollution.

On the regional distributions of background carbon monoxide concentrations observed in East Asia during 1991–2008

The carbon monoxide (CO) concentrations observed at Mt. Waliguan in China (WLG), Ulaan Uul in Mongolia (UUM), Tae-ahn Peninsula in Korea (TAP) and Ryori in Japan (RYO) were analysed between 1991 and 2008. The average annual concentration of CO, a toxic air pollutant, was the highest at TAP (235±44 ppb), followed by RYO (169±35 ppb), UUM (154±27 ppb) and WLG (138±24 ppb). These data obtained in East Asia were also compared with CO data from Mauna Loa, Hawaii. CO tends to be highest in spring and lowest in summer in East Asia, with the exception of WLG. TAP had the highest CO concentrations in all seasons compared with WLG, UUM and RYO, and displays a wide short-term variability in concentration. This is caused by large-scale air pollution owing to its downwind location, close to continental East Asia. CO concentrations observed at TAP were analysed as follows: according to the origin of the isentropic backward trajectory and its transport passage; as continental background airflows (CBG); regionally polluted continental airflows (RPC); oceanic background airflows (OBG); and partly perturbed oceanic airflows (PPO). The high concentrations of CO at TAP are because of the airflow originating from the East Asian continent, rather than the North Pacific. RPCs, which pass through eastern China, appear to have high CO concentrations in spring, autumn and winter. It is noteworthy that the overall trend at TAP does not show an increase despite the fact that energy use in China approximately doubled from 1991 to 2008. OBGs, however, are affected by North Pacific air masses with low CO concentrations in summer.

Temporal variations of elemental carbon in Beijing

Concentrations of elemental carbon (EC), carbon monoxide (CO), and carbon dioxide (CO2) were measured in Beijing between 2005 and 2006. EC was measured every hour with a semicontinuous thermal optical analyzer. The observed concentrations were rather uniform over a distance of about 50 km from the observation site. The annual average concentrations of EC and CO were 6.9 μgC m−3 and 1120 parts per billion by volume, respectively. The concentrations of these species increased with decreasing near‐surface wind speed (WS). The slopes of the CO‐CO2, EC‐CO2, and EC‐CO correlations are used to estimate major EC and CO sources. In the weak wind regime (WS ≤ 2.0 m s−1), the median EC, ΔEC/ΔCO2, and ΔEC/ΔCO (except for winter) increased in the late evening and remained high until early morning. The traffic of heavy duty diesel trucks during nighttime was about 20 times higher than that during daytime. These results indicate a dominant contribution of exhaust from diesel vehicles to the nighttime EC. In winter, the nighttime CO and ΔCO/ΔCO2 ratio were largely higher than those in the other seasons. The most likely cause is the increase in the CO emissions from the exhaust of gasoline vehicles at low temperature. The ΔEC/ΔCO2 ratio in winter was lower than that in fall, indicating no significant additional EC emissions. The diurnal variations of EC, CO, CO2, and ΔEC/ΔCO were similar between weekdays and weekends. The slopes of the CO‐CO2‐EC correlations are compared with the CO‐CO2‐EC ratios derived from a published emission inventory in the Beijing area.

Exposure to Carbon Monoxide from Second-hand Tobacco Smoke in Polish Pubs

Carbon monoxide (CO) is one of the more toxic agents present in the gas phase of second-hand tobacco smoke. There is sufficient evidence suggesting that passive smokers are involuntarily poisoned by low CO concentrations. At lower doses, CO affects the central nervous system leading to deterioration in visual perception, manual dexterity, learning, driving performance, and attention level. The effects of chronic inhalation of CO at doses corresponding to tobacco smoking on the cardiovascular system are not well investigated but might involve myocardial hypertrophy and arrhythmias. In people with pre-existing disease, CO pollution alone may result in increased morbidity and mortality. In the study CO levels were monitored in 22 Polish pubs. The temporary CO concentration varied in examined pubs from 0 to 33.11 ppm. The average 8-hours CO concentration varied from 0.21 to 10.20 ppm. Nine percent of pubs exceeded the WHO or EU limit value at some point during the monitoring process. The average weekly CO concentration in all examined microenvironments varied from 0 to 4.80 ppm. The most important factor influencing CO concentration was air-exchange through open doors and windows. In pubs where doors and windows were closed, the following statistical important factors influencing CO concentration were found: 1. the number of smokers present in the pub, 2. the pub's capaciousness, and 3. and the pub's location. The results of the study show that second-hand tobacco smoke is a significant source of CO in Polish pubs. Passive smokers in Polish pubs might be exposed to very high CO concentration exceeding EU reference value.

Air pollution and emergency department visits for cardiac and respiratory conditions: a multi-city time-series analysis

BackgroundRelatively few studies have been conducted of the association between air pollution and emergency department (ED) visits, and most of these have been based on a small number of visits, for a limited number of health conditions and pollutants, and only daily measures of exposure and response.MethodsA time-series analysis was conducted on nearly 400,000 ED visits to 14 hospitals in seven Canadian cities during the 1990s and early 2000s. Associations were examined between carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), and particulate matter (PM10 and PM2.5), and visits for angina/myocardial infarction, heart failure, dysrhythmia/conduction disturbance, asthma, chronic obstructive pulmonary disease (COPD), and respiratory infections. Daily and 3-hourly visit counts were modeled as quasi-Poisson and analyses controlled for effects of temporal cycles, weather, day of week and holidays.Results24-hour average concentrations of CO and NO2 lag 0 days exhibited the most consistent associations with cardiac conditions (2.1% (95% CI, 0.0–4.2%) and 2.6% (95% CI, 0.2–5.0%) increase in visits for myocardial infarction/angina per 0.7 ppm CO and 18.4 ppb NO2 respectively; 3.8% (95% CI, 0.7–6.9%) and 4.7% (95% CI, 1.2–8.4%) increase in visits for heart failure). Ozone (lag 2 days) was most consistently associated with respiratory visits (3.2% (95% CI, 0.3–6.2%), and 3.7% (95% CI, -0.5–7.9%) increases in asthma and COPD visits respectively per 18.4 ppb). Associations tended to be of greater magnitude during the warm season (April – September). In particular, the associations of PM10 and PM2.5with asthma visits were respectively nearly three- and over fourfold larger vs. all year analyses (14.4% increase in visits, 95% CI, 0.2–30.7, per 20.6 μg/m3 PM10 and 7.6% increase in visits, 95% CI, 5.1–10.1, per 8.2 μg/m3 PM2.5). No consistent associations were observed between three hour average pollutant concentrations and same-day three hour averages of ED visits.ConclusionIn this large multicenter analysis, daily average concentrations of CO and NO2 exhibited the most consistent associations with ED visits for cardiac conditions, while ozone exhibited the most consistent associations with visits for respiratory conditions. PM10 and PM2.5 were strongly associated with asthma visits during the warm season.

Air Pollution and Recent Symptoms of Asthma, Allergic Rhinitis, and Atopic Eczema in Schoolchildren Aged Between 6 and 7 Years

Objective The objective of the study was to analyze the relationship between air pollutants and the prevalence of recent symptoms of asthma, allergic rhinitis, and atopic eczema in schoolchildren aged between 6 and 7 years. Patients and Methods The prevalence of recent (previous 12 months) symptoms of allergic diseases was obtained by means of the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC), Spain, with the participation of 7 centers (Asturias, Barcelona, Bilbao, Cartagena, La Coruña, Madrid, and Valencia) and 20 455 schoolchildren aged between 6 and 7 years, from 2002 to 2003. The pollutant detection systems of the aforementioned centers provided the mean annual concentrations of sulfur dioxide (SO 2), nitrogen dioxide (NO 2), carbon monoxide (CO), and total suspended particulate matter. Results The annual average concentration of SO 2 showed a significant association with a higher prevalence of recent severe asthma (adjusted odds ratio [aOR] between level-1 and level-3 pollution, 1.32; 95% confidence interval [CI], 1.01–1.73), rhinitis (aOR, 1.56; 95% CI, 1.39–1.75), and rhinoconjunctivitis (aOR, 1.70; 95% CI, 1.45–2.00). The annual average concentration of CO was associated with a higher prevalence of rhinitis (aOR, 1.65; 95% CI, 1.34-2.04), rhinoconjunctivitis (aOR, 1.76; 95% CI, 1.31–2.37), and eczema (aOR, 1.55; 95% CI, 1.17–2.04). The annual average concentration for NO 2 and total suspended particulate matter showed inverse associations with the prevalence of nocturnal dry cough. Conclusions Findings suggest that air pollutants such as SO 2 and CO increase the risk of recent symptoms of asthma and allergic rhinitis in schoolchildren aged between 6 and 7 years in Spain.

Temporal and spatial variations of carbon monoxide over the western part of the Pacific Ocean

Systematic observations of atmospheric carbon monoxide (CO) have been carried out in the western part of the Pacific Ocean since February 1990. The average CO concentration showed a latitudinal gradient, with higher values in the northern hemisphere than in the southern hemisphere. A clear seasonal CO cycle was found nearly at all sampling locations, showing maximum and minimum concentrations in spring and summer, respectively. In the 30°–35°N latitude zone, the average CO concentration was higher and the seasonal amplitude was larger compared with other latitudes. The CO concentration also showed a large interannual variability mainly in association with forest fires. In particular, the forest fires in Siberia in 1998 and Indonesia in 1997–1998 contributed to a remarkable increase in the regional CO concentration, followed by a recovery that took several months to a year. A three‐dimensional atmospheric global chemical transport model (CHASER) was used to simulate the observed characteristics of the latitudinal distribution, seasonal cycle, and interannual variability relatively well. Tagged CO experiments with the model revealed that the contribution of CO emissions from various regions in the northern hemisphere to the CO concentrations at our sampling locations varied seasonally in association with Asian outflows and long‐range transport from Europe and North America. In the southern hemisphere, biomass burnings significantly affected the regional seasonal CO cycle, in addition to the effect of CO oxidation with OH. It was also found that CHASER underestimates the average CO concentration in the northern hemisphere and its interannual variability.

Contaminación del aire y síntomas recientes de asma, rinitis alérgica y eccema atópico en escolares de 6 y 7 años

Objective The objective of the study was to analyze the relationship between air pollutants and the prevalence of recent symptoms of asthma, allergic rhinitis, and atopic eczema in schoolchildren aged between 6 and 7 years. Patients and Methods The prevalence of recent (previous 12 months) symptoms of allergic diseases was obtained by means of the questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC), Spain, with the participation of 7 centers (Asturias, Barcelona, Bilbao, Cartagena, La Coruña, Madrid, and Valencia) and 20 455 schoolchildren aged between 6 and 7 years, from 2002 to 2003. The pollutant detection systems of the aforementioned centers provided the mean annual concentrations of sulfur dioxide (SO 2), nitrogen dioxide (NO 2), carbon monoxide (CO), and total suspended particulate matter. Results The annual average concentration of SO 2 showed a significant association with a higher prevalence of recent severe asthma (adjusted odds ratio [aOR] between level-1 and level-3 pollution, 1.32; 95% confidence interval [CI], 1.01–1.73), rhinitis (aOR, 1.56; 95% CI, 1.39–1.75), and rhinoconjunctivitis (aOR, 1.70; 95% CI, 1.45–2.00). The annual average concentration of CO was associated with a higher prevalence of rhinitis (aOR, 1.65; 95% CI, 1.34–2.04), rhinoconjunctivitis (aOR, 1.76; 95% CI, 1.31–2.37), and eczema (aOR, 1.55; 95% CI, 1.17–2.04). The annual average concentration for NO 2 and total suspended particulate matter showed inverse associations with the prevalence of nocturnal dry cough. Conclusions Findings suggest that air pollutants such as SO 2 and CO increase the risk of recent symptoms of asthma and allergic rhinitis in schoolchildren aged between 6 and 7 years in Spain.

Outdoor air pollution in close proximity to a continuous point source

Data are lacking on human exposure to air pollutants occurring in ground-level outdoor environments within a few meters of point sources. To better understand outdoor exposure to tobacco smoke from cigarettes or cigars, and exposure to other types of outdoor point sources, we performed more than 100 controlled outdoor monitoring experiments on a backyard residential patio in which we released pure carbon monoxide (CO) as a tracer gas for continuous time periods lasting 0.5–2 h. The CO was emitted from a single outlet at a fixed per-experiment rate of 120–400 cc min −1 (∼140–450 mg min −1). We measured CO concentrations every 15 s at up to 36 points around the source along orthogonal axes. The CO sensors were positioned at standing or sitting breathing heights of 2–5 ft (up to 1.5 ft above and below the source) and at horizontal distances of 0.25–2 m. We simultaneously measured real-time air speed, wind direction, relative humidity, and temperature at single points on the patio. The ground-level air speeds on the patio were similar to those we measured during a survey of 26 outdoor patio locations in 5 nearby towns. The CO data exhibited a well-defined proximity effect similar to the indoor proximity effect reported in the literature. Average concentrations were approximately inversely proportional to distance. Average CO levels were approximately proportional to source strength, supporting generalization of our results to different source strengths. For example, we predict a cigarette smoker would cause average fine particle levels of approximately 70–110 μg m −3 at horizontal distances of 0.25–0.5 m. We also found that average CO concentrations rose significantly as average air speed decreased. We fit a multiplicative regression model to the empirical data that predicts outdoor concentrations as a function of source emission rate, source–receptor distance, air speed and wind direction. The model described the data reasonably well, accounting for ∼50% of the log-CO variability in 5-min CO concentrations.

TREND IN EXHAUST EMISSIONS FROM IN-USE GASOLINE VEHICLES

The main goal of this study is to determine the trend in exhaust concentrations during the last 12 years. Accordingly, a non-disperse infrared gas analyzer was used to measure the concentrations of carbon monoxide (CO) and hydrocarbons (HC) emitted from vehicle exhaust. A total of 449 vehicles distributed across model years ranging between 1968 and 2005 were tested under idling conditions. The results indicated that there is a strong relationship between the age of the vehicle and the concentration of exhaust emissions. Moreover, there has been a significant reduction in exhaust emissions over the last 12 years with decrease in the average concentrations of CO and HC of 25% and 28%, respectively. Therefore, it is recommended removing the customs fees for the new vehicles and maintenance spare parts, which will encourage the purchase of new vehicles and participation in maintenance programs, with further decreases in exhaust emissions.

Abatement of indoor air pollution achieved with coal–biomass household briquettes

We investigated the abatement of indoor pollution achieved when two types of coal–biomass briquettes (L-BBs and H-BBs) were used in place of honeycombed coal briquettes (H-coal) in household stoves in rural Chongqing, China. Indoor concentrations of sulfur dioxide (SO 2), carbon monoxide (CO), and gaseous fluoride were measured. Additionally, we evaluated the factors that affected indoor concentrations of these gases, including the amount of fuel used as well as its sulfur content, the sulfur-emission ratio determined from the amount of sulfur retained in the combustion ash, and the combustion temperature in the stoves. The average 8-h and 24-h SO 2 concentrations for L-BBs were nearly equal to or less than the World Health Organization's 40 ppb guideline, whereas those for H-coal and H-BBs exceeded the guideline. The average 8-h SO 2 concentrations for L-BBs were from 63 to 89% lower than those for H-coal, even though the 8-h average weight of fuel and its sulfur content for L-BBs were equal to those of H-coal. A chemical analysis of combustion ash indicated that the sulfur-emission ratio was from 26 to 48% for L-BBs, as compared with 86% for H-coal, and this difference resulted in reduction of indoor SO 2 concentrations for L-BBs as compared with H-coal. Most of the 8-h average concentrations of CO and gaseous fluoride for all fuels were lower than the WHO guidelines. We concluded that BBs are a useful domestic fuel for the abatement of indoor air pollution.

Inspiratory Carbon Monoxide and Compound A Concentrations During Desflurane and Sevoflurane Anesthesia in Humans: An Observational Study

All modern vapor anesthetics are capable of carbon monoxide (CO) production as a result of interaction with desiccated strong base containing carbon dioxide absorbents. In desiccated absorbents, desflurane produces the highest concentrations of CO. Sevoflurane is known to produce the nephrotoxic compound A (CA) independently from water content of the carbon dioxide absorbent. The purpose of this study was to register the average CO concentrations in forty patients receiving anesthesia with desflurane or sevoflurane after implementation of a safety protocol adapted from Woehlck et al.. This protocol was developed to prevent desiccation of the strong base containing absorbent Dägersorb 800 Plus®. Methods: In 40 patients a low-flow anesthesia was maintained using an oxygen/air mixture with either sevoflurane or desflurane in combination with the CO2 absorbent Dägersorb 800 plus®. CO and CA production was measured in the inspiratory limb of the anesthesia machine using a portable gas chromatograph, with a sampling frequency of 12 samples per hour. Results: No carbon monoxide was measured in any of the desflurane or sevoflurane anesthesia’s. The mean concentration of CA for anesthesia with sevoflurane was 17.1 ± 5.5 parts per million. Conclusion: With the introduction of a safety protocol no carbon monoxide was measured in anesthesia performed with desflurane or sevoflurane. Compound A is almost continuously detected in anesthetic procedures with the use of sevoflurane in very low concentrations. Implementation of a simple safety protocol possibly prevents desiccation of the absorbent and could subsequently reduce the risk of carbon monoxide intoxication.

Measuring the exposure of infants and children to indoor air pollution from biomass fuels in The Gambia

Indoor air pollution (IAP) from biomass fuels contains high concentrations of health damaging pollutants and is associated with an increased risk of childhood pneumonia. We aimed to design an exposure measurement component for a matched case-control study of IAP as a risk factor for pneumonia and severe pneumonia in infants and children in The Gambia. We conducted co-located simultaneous area measurement of carbon monoxide (CO) and particles with aerodynamic diameter <2.5 microm (PM(2.5)) in 13 households for 48 h each. CO was measured using a passive integrated monitor and PM(2.5) using a continuous monitor. In three of the 13 households, we also measured continuous PM(2.5) concentration for 2 weeks in the cooking, sleeping, and playing areas. We used gravimetric PM(2.5) samples as the reference to correct the continuous PM(2.5) for instrument measurement error. Forty-eight hour CO and PM(2.5) concentrations in the cooking area had a correlation coefficient of 0.80. Average 48-h CO and PM(2.5) concentrations in the cooking area were 3.8 +/- 3.9 ppm and 361 +/- 312 microg/m3, respectively. The average 48-h CO exposure was 1.5 +/- 1.6 ppm for children and 2.4 +/- 1.9 ppm for mothers. PM(2.5) exposure was an estimated 219 microg/m3 for children and 275 microg/m3 for their mothers. The continuous PM(2.5) concentration had peaks in all households representing the morning, midday, and evening cooking periods, with the largest peak corresponding to midday. The results are used to provide specific recommendations for measuring the exposure of infants and children in an epidemiological study. Measuring personal particulate matter (PM) exposure of young children in epidemiological studies is hindered by the absence of small personal monitors. Simultaneous measurement of PM and carbon monoxide suggests that a combination of methods may be needed for measuring children's PM exposure in areas where household biomass combustion is the primary source of indoor air pollution. Children's PM exposure in biomass burning homes in The Gambia is substantially higher than concentrations in the world's most polluted cities.

On the regional background levels of carbon monoxide observed in East Asia during 1991∼2004

The carbon monoxide (CO) concentrations observed in Mt. Waliguan in China (WLG), Ulaan Uul in Mongolia (UUM), Tae-ahn Peninsula in Korea (TAP) and Ryori in Japan (RYO) were analysed between 1991 and 2004. The average annual concentration of CO, a toxic air pollutant, was the highest at TAP (233 ± 41 ppb), followed by RYO (171 ± 36 ppb), UUM (155 ± 26 ppb) and WLG (135 ± 22 ppb). CO tends to be highest in spring and lowest in summer in East Asia, with the exception of WLG. TAP had the highest CO concentrations in all seasons compared with WLG, UUM and RYO and displays a wide short-term variability in concentration. This is caused by large-scale air pollution owing to its downwind location, close to continental East Asia. CO concentrations observed at TAP were analysed as follows: according to the origin of the isentropic backward trajectory and its transport passage, as continental background airflows (CBG) measuring 216 ± 47 ppb, regionally polluted continental airflows (RPC) measuring 316 ± 56 ppb, oceanic background airflows (OBG) measuring 108 ± 41 ppb and partly perturbed oceanic airflows measuring 161 ± 6 ppb. The high concentrations of CO at TAP are because of the airflow originating from the East Asian continent, rather than the North Pacific. RPCs, which pass through eastern China, appear to have high CO concentrations in spring, autumn and winter. OBGs, however, are affected by North Pacific air masses with low CO concentrations in summer. National Oceanic and Atmospheric Administration satellite images and the Goddard Earth Observing System (GEOS)-Chem simulation model confirmed that a large-scale air pollution event originated in eastern China and reached the Korean Peninsula and the Korea East Sea by way of the Yellow Sea. It is noteworthy that the overall trend at TAP does not show an increase despite the fact that energy use in China approximately doubled from 1991 to 2004.

Experimental Analysis of Vehicle Operation Parameters Affecting Emission Behavior of Public Transport Buses with Alternative Diesel Fuels

Key results are presented from an exhaust emission study conducted on more than 105 buses in idling condition and selected sample buses from seven fleets in real-world operating conditions in Toledo, Ohio, of the effects of varying vehicular operation parameters on public transport bus emissions. It was observed that for the same amount of time in operation, vehicles in idling mode produced higher average concentrations of carbon monoxide, nitric oxide, nitrogen dioxide, and sulfur dioxide than those in on-road operation. Operating the vehicles in normal engine idling mode and with higher engine temperatures was found to reduce vehicular emissions by up to 30% to 42% as compared with fast idling and lower or colder engine temperatures. Performing regular preventive maintenance reduced emission concentrations by 15% to 20%. The results also highlight that a combination of multiple influencing factors including engine technology, vehicle age, vehicular maintenance, fuel, and past and present operating conditions should be evaluated to better understand and predict vehicular emission behavior.

Chaos in Air Pollutant Concentration (APC) Time Series

Three chaotic indicators, namely the correlation dimension, the Lyapunov exponent, and the Kolmogorov entropy, are estimated for one-year long hourly average NO (nitrogen monoxide), CO (carbon monoxide), SO2 (sulfur dioxide), PM10 (particles with an aerodynamic diameter of approximately 10 μm or less), and NO2 (nitrogen dioxide) concentration to examine the possible chaotic characteristics in the air pollutant concentration (APC) time series. The presence of chaos in the examined APC time series is evident with the low correlation dimensions (3.42-4.71), the positive values of the largest Lyapunov exponent (0.128-0.427), and the positive Kolmogorov entropies (0.628-0.737). Since the existence of multifractal characteristics in the above time series has been confirmed in our previous investigations, the presence of chaotic behavior identified in the current study suggests the possibility of a chaotic multifractal approach for APC time series characterization. Some problems concerning the applicability of chaos analysis in air pollution are also discussed.