Ambient Carbon Monoxide Concentrations Research Articles

Does ambient CO have protective effect for COPD patient?

BackgroundExisting studies found paradoxical effects of carbon monoxide (CO) on human health. Carbon monoxide (CO), at high concentrations, is a well-known toxicant, but recent studies suggest that CO at low concentrations may have protective health effects under certain conditions. ObjectivesTo investigate the acute effect of ambient CO on hospital admission for chronic obstructive pulmonary disease (COPD) in Shanghai, China. MethodsDaily data on COPD admissions and CO concentrations between 2006 and 2008 were collected. We applied over-dispersed generalized additive Poisson models, adjusted for weather conditions, day of the week and public holidays, long-term and seasonal trends. ResultsDuring the study period, the average CO concentration was 1.3mg/m3, well below the international health-based standard. Negative associations were found between ambient CO concentration and daily COPD hospitalization. An interquartile range increase (0.6mg/m3) in CO concentration at lag 3day corresponded to −2.97% (95% confidence interval: −4.63%, −1.31%) change in COPD hospitalization. The negative associations were robust after adjustment for co-pollutants (PM10, NO2 and SO2). The protective effect of CO appeared to be more evident in the cool season. ConclusionShort-term exposure to CO at low ambient concentration may be associated with reduced risk of COPD hospitalization. Our results may contribute to a comprehensive understanding on the health effects of ambient CO.

Driving Restrictions that Work? Quito's Pico y Placa Program

Programs to reduce traffic congestion and air pollution by restricting use of motor vehicles on working days have generally not met with success, given existing studies of such programs. We conduct the first study of Quito, Ecuador's four-year-old Pico y Placa program and find that it has reduced ambient concentrations of carbon monoxide (CO), a pollutant primarily emitted by vehicles, by 9-11% during peak traffic hours. Given that ambient concentrations of CO generally track the spatial and temporal distributions of traffic, these reductions in pollution suggest similar reductions in vehicle flows. We find no evidence that traffic has shifted to other times of the day or week, or to other locations.

Multifactorial airborne exposures and respiratory hospital admissions — The example of Santiago de Chile

Our results provide evidence for respiratory effects of combined exposure to airborne pollutants in Santiago de Chile. Different pollutants account for varying adverse effects. Ozone was not found to be significantly associated with respiratory morbidity. BackgroundHigh concentrations of various air pollutants have been associated with hospitalization due to development and exacerbation of respiratory diseases. The findings of different studies vary in effect strength and are sometimes inconsistent. ObjectivesWe aimed to assess associations between airborne exposures by particulate matter as well as gaseous air pollutants and hospital admissions due to respiratory disease groups under the special orographic and meteorological conditions of Santiago de Chile. MethodsThe study was performed in the metropolitan area of Santiago de Chile during 2004–2007. We applied a time-stratified case-crossover analysis taking temporal variation, meteorological conditions and autocorrelation into account. We computed associations between daily ambient concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5 — particulate matter with aerodynamic diameters less than 10 or 2.5μm, respectively) or ozone (O3) and hospital admissions for respiratory illnesses. ResultsWe found for CO, NO2, PM10 and PM2.5 adverse relationships to respiratory admissions while effect strength and lag depended on the pollutant and on the disease group. By trend, in 1-pollutant models most adverse pollutants were CO and PM10 followed by PM2.5, while in 2-pollutant models effects of NO2 persisted in most cases whereas other effects weakened and significant effects remain for PM2.5, only. In addition the strongest effects seemed to be immediate or with a delay of up to one day, but effects were found until day 7, too. Adverse effects of ozone could not be detected. ConclusionsTaking case numbers and effect strength of all cardiovascular diseases into account, mitigation measures should address all pollutants especially CO, NO2, and PM10.

Trends in on-road vehicle emissions and ambient air quality in Atlanta, Georgia, USA, from the late 1990s through 2009

On-road vehicle emissions of carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOCs) during 1995–2009 in the Atlanta Metropolitan Statistical Area were estimated using the Motor Vehicle Emission Simulator (MOVES) model and data from the National Emissions Inventories and the State of Georgia. Statistically significant downward trends (computed using the nonparametric Theil-Sen method) in annual on-road CO, NOx, and VOC emissions of 6.1%, 3.3%, and 6.0% per year, respectively, are noted during the 1995–2009 period despite an increase in total vehicle distance traveled. The CO and NOx emission trends are correlated with statistically significant downward trends in ambient air concentrations of CO and NOx in Atlanta ranging from 8.0% to 11.8% per year and from 5.8% to 8.7% per year, respectively, during similar time periods. Weather-adjusted summertime ozone concentrations in Atlanta exhibited a statistically significant declining trend of 2.3% per year during 2001–2009. Although this trend coexists with the declining trends in on-road NOx, VOC, and CO emissions, identifying the cause of the downward trend in ozone is complicated by reductions in multiple precursors from different source sectors.Implications:Large reductions in on-road vehicle emissions of CO and NOx in Atlanta from the late 1990s to 2009, despite an increase in total vehicle distance traveled, contributed to a significant improvement in air quality through decreases in ambient air concentrations of CO and NOx during this time period. Emissions reductions in motor vehicles and other source sectors resulted in these improvements and the observed declining trend in ozone concentrations over the past decade. Although these historical trends cannot be extrapolated to the future because pollutant concentration contributions due to on-road vehicle emissions will likely become an increasingly smaller fraction of the atmospheric total, they provide an indication of the benefits of past control measures.

Birth Defects and Mothers’ Proximity to Natural Gas Development: Is There a Connection?

More than 15 million Americans are now estimated to live within one mile of a natural gas well drilled since 2000.1 Research has demonstrated that natural gas development results in the emission of pollutants that include suspected developmental toxicants, such as benzene, toluene, and xylenes,2 although few studies have investigated the public health impact of these emissions. In this issue of EHP, researchers report preliminary evidence of an association between two birth defects and a mother’s residential proximity to natural gas wells at the time of birth.3 “Studies like this underscore the need for more representative and comprehensive research on workers and communities to understand their exposures and potential health risks,” says Aubrey Miller, a senior medical advisor at the National Institute of Environmental Health Sciences. Researchers led by Lisa McKenzie at the Colorado School of Public Health estimated exposure to natural gas development for nearly 125,000 Colorado women. They used an “inverse distance weighting” method in which they determined the density of natural gas wells within a 10-mile radius of each mother’s home at the time she gave birth, with greater weighting for wells nearer the home. Then they compared proximity to gas wells between mothers who had adverse birth outcomes—including three types of birth defects, preterm birth, and term low birth weight—and those who did not. Future studies should assess exposure to benzene (inset) among people living near gas wells. Among 59 cases of neural tube defects, prevalence was twice as high among babies of mothers in the highest exposure group—a group of 19 women with more than 125 wells per mile within a 10-mile radius of the home—compared with babies of unexposed mothers. However, there was no evidence that neural tube defects were increased among the 13 babies of mothers classified as having low or medium exposure. Among 1,823 cases of congenital heart defects, prevalence was 30% higher among babies of mothers in the highest exposure group, compared with babies born to unexposed mothers. In contrast to neural tube defects, however, the likelihood of a congenital heart defect increased steadily with increasing exposure. Congenital heart defects are the most common type of birth defect, affecting about 8 of every 1,000 newborns in the United States.4 There was no association observed between proximity to natural gas development and having babies with an oral cleft. In addition, babies whose mothers experienced the highest exposures to natural gas wells were slightly less likely to be born prematurely or at a low birth weight. However, the association between proximity to gas wells and improving birth weights diminished when the researchers accounted for elevation. “Higher elevations are associated with lower birth weights, while most natural gas drilling in Colorado occurs at low elevations,” McKenzie explains. Although low levels of maternal folic acid—a B vitamin found in green leafy vegetables—is an established risk factor for neural tube defects,5 little is known about other environmental factors that may contribute to these birth defects. Two previous studies suggested that maternal exposure to benzene could increase congenital heart defects and neural tube defects.6,7 Another study reported associations between several birth defects in California and increased ambient concentrations of carbon monoxide and ozone.8 “The study certainly raises legitimate concerns, given that there are plausible mechanisms for many of the chemicals that are used in natural gas development,” says Kenneth Spaeth, medical director of the Occupational and Environmental Medicine Center at North Shore University Hospital inNew York, who was not involved in the study. The authors suggest that exposure to benzene from the wells is one such plausible explanation for their findings. However, they did not identify or measure specific pollutants that may have been present at natural gas wells or specific activities occurring at the sites, so it is not possible to know which chemicals and/or other environmental stressors—if any—explain the associations. It’s also possible that some other risk factor not associated with wells, such as mothers’ folic acid consumption or level of prenatal care, could have influenced the results. “Our findings are far from representing a causal effect,” says McKenzie. Her plans for future research include interviews with study mothers to get more information about their pregnancy and place of residence during the first trimester, a critical period for birth defect formation. She also plans to obtain more detailed information on specific activities taking place at well sites during the first trimester.

Carbon monoxide concentrations in outdoor wood-fired kitchens in Ouagadougou, Burkina Faso—implications for women’s and children’s health

A majority of households in developing countries rely on biomass fuel for cooking, typically burned in open fires or simple stoves. The incomplete combustion of these fuels causes adverse health effects such as respiratory diseases, especially among women and children. However, quantitative data on pollution levels and on associated diseases are limited. We examined cooking habits and self-reported health in 31 households with outdoor open wood fires in Ouagadougou, Burkina Faso, using structured interviews. In eight households, carbon monoxide (CO) was measured using passive sampling. In addition, meteorology and ambient CO concentrations were assessed. The average CO concentration during cooking was 4.3ppm, with a maximum of 65.3ppm and minimum of 0.3ppm (1-min values). A clear daily pattern was observed, with relatively low concentrations during the day and high during the evening, occasionally exceeding the World Health Organization 1- and 8-h guidelines when the air stabilised. On average, CO concentrations were 43% higher in kitchens located in closed yards than in those located in open yards, showing that fireplace location affected the levels. Eye irritation and coughing among women and children were reported by 30% of the households. Based on previously reported relations between CO concentrations and fine particles (<2.5μm), the exposure to biomass smoke appears to be high enough to pose a considerable health risk among women and children in households with outdoor open wood fires. The results suggest that burning should be limited between sunset and dawn and in areas with limited ventilation to reduce pollutions levels.

Brachial Artery Responses to Ambient Pollution, Temperature, and Humidity in People with Type 2 Diabetes: A Repeated-Measures Study

Background: Extreme weather and air pollution are associated with increased cardiovascular risk in people with diabetes.Objectives: In a population with diabetes, we conducted a novel assessment of vascular brachial artery responses both to ambient pollution and to weather (temperature and water vapor pressure, a measure of humidity).Methods: Sixty-four 49- to 85-year-old Boston residents with type 2 diabetes completed up to five study visits (279 repeated measures). Brachial artery diameter (BAD) was measured by ultrasound before and after brachial artery occlusion [i.e., flow-mediated dilation (FMD)] and before and after nitroglycerin-mediated dilation (NMD). Ambient concentrations of fine particulate mass (PM2.5), black carbon (BC), organic carbon (OC), elemental carbon, particle number, and sulfate were measured at our monitoring site; ambient concentrations of carbon monoxide, nitrogen dioxide, and ozone were obtained from state monitors. Particle exposure in the home and during each trip to the clinic (home/trip exposure) was measured continuously and as a 5-day integrated sample. We used linear models with fixed effects for participants, adjusting for date, season, temperature, and water vapor pressure on the day of each visit, to estimate associations between our outcomes and interquartile range increases in exposure.Results: Baseline BAD was negatively associated with particle pollution, including home/trip–integrated BC (–0.02 mm; 95% CI: –0.04, –0.003, for a 0.28 μg/m3 increase in BC), OC (–0.08 mm; 95% CI: –0.14, –0.03, for a 1.61 μg/m3 increase) as well as PM2.5, 5-day average ambient PM2.5, and BC. BAD was positively associated with ambient temperature and water vapor pressure. However, exposures were not consistently associated with FMD or NMD.Conclusion: Brachial artery diameter, a predictor of cardiovascular risk, decreased in association with particle pollution and increased in association with ambient temperature in our study population of adults with type 2 diabetes.Citation: Zanobetti A, Luttmann-Gibson H, Horton ES, Cohen A, Coull BA, Hoffmann B, Schwartz JD, Mittleman MA, Li Y, Stone PH, de Souza C, Lamparello B, Koutrakis P, Gold DR. 2014. Brachial artery responses to ambient pollution, temperature, and humidity in people with type 2 diabetes: a repeated-measures study. Environ Health Perspect 122:242–248; http://dx.doi.org/10.1289/ehp.1206136

Ambient Carbon Monoxide Associated with Reduced Risk of Hospital Admissions for Respiratory Tract Infections

Recent experimental and clinical studies suggest that exogenous carbon monoxide (CO) at lower concentrations may have beneficial effects under certain circumstances, whereas population-based epidemiologic studies of environmentally relevant CO exposure generated mixed findings. To examine the acute effects of ambient CO on respiratory tract infection (RTI) hospitalizations. A time series study was conducted. Daily emergency hospital admission and air pollution data in Hong Kong were collected from January 2001 to December 2007. Log-linear Poisson models were used to estimate the associations between daily hospital admissions for RTI and daily average concentrations of CO across three background air monitoring stations and three roadside stations, respectively, controlling for other traffic-related copollutants. CO concentrations were low during the study period with a daily average of 0.6 ppm in background stations and 1.0 ppm in roadside stations. Negative associations were found between ambient CO concentrations and daily hospital admissions for RTI. One ppm increase in background CO at lag 0-2 days was associated with -5.7% (95% confidence interval, -9.2 to -2.1) change in RTI admissions from the whole population according to single-pollutant model; the negative association became stronger when nitrogen dioxide or particulate matter with aerodynamic diameter less than 10 μm was adjusted for in two-pollutant models. The negative association seemed to be stronger in the adults than in the children and elderly. Short-term exposure to ambient CO was associated with decreased risk of hospital admissions for RTI, suggesting some acute protective effects of low ambient CO exposure on respiratory infection.

Multiple exposures to airborne pollutants and hospital admissions due to diseases of the circulatory system in Santiago de Chile

BackgroundHigh concentrations of various air pollutants have been associated with hospitalization due to development and exacerbation of cardiovascular diseases. ObjectivesWe aimed to assess associations between airborne exposures by particulate matter as well as gaseous air pollutants and hospital admissions due to different cardiovascular disease groups in Santiago de Chile. MethodsThe study was performed in the metropolitan area of Santiago de Chile during 2004–2007. We applied a time-stratified case-crossover analysis taking temporal variation, meteorological conditions and autocorrelation into account. We computed associations between daily ambient concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5 — particulate matter with aerodynamic diameters less than 10 or 2.5μm, respectively) or ozone (O3) and hospital admissions for cardiovascular illnesses. ResultsWe found for CO, NO2, PM10 and PM2.5 adverse relationships to cardiovascular admissions while effect strength and lag depended on the pollutant and on the disease group. By trend, in 1-pollutant models most adverse pollutants were NO2 and particulate matter (PM10 and PM2.5) followed by CO, while in 2-pollutant models effects of PM10 persisted in most cases whereas other effects weakened. In addition the strongest effects seemed to be immediate or with a delay of up to 2days. Adverse effects of ozone could not be detected. ConclusionsOur results provided evidence for adverse health effects of combined exposure to airborne pollutants. Different pollutants accounted for varying adverse effects within different cardiovascular disease groups. Taking case numbers and effect strength of all cardiovascular diseases into account, mitigation measures should address all pollutants but especially NO2, PM10, and CO.

Exposure to Carbon Monoxide for Patients and Providers in an Urban Emergency Medical Service

Background. Carbon monoxide (CO) poisoning poses danger to both patients and emergency medical services (EMS) personnel, as its symptoms are nonspecific and EMS is currently not equipped to detect CO in ambient air. Objective. We aimed to assess the degree of non–fire-related CO exposure at the high-volume EMS system of a city with 2 million inhabitants. Methods. The EMS system was equipped with handheld CO detectors (Dräger Pac 3500), which were added to EMS standard backpacks and had to be carried to the patient at all times. During a period of one year, all alarms by those devices were recorded, sources of CO were confirmed by the fire department, and hospital follow-up was conducted for both patients and exposed EMS staff. Results. During the study period, there were 40 alarms, including two false alarms. Alarms occurred during the whole year, with a peak during the winter months. The median ambient CO concentration was 167 parts per million; gas heating systems were the main source of CO. One hundred ten patients and 108 EMS personnel were exposed. One hundred fifteen persons, including 22 EMS staff, had to be hospitalized, which represents one out of 1,000 total EMS patients. Conclusions. Carbon monoxide poisoning was found to be a significant matter for a high-volume EMS system. Handheld CO detectors helped in identifying those cases. Key words: carbon monoxide; emergency care, prehospital; equipment and supplies; poisoning

Adaptive neuro-fuzzy modeling for prediction of ambient CO concentration at urban intersections and roadways

This paper describes development of neuro-fuzzy models to predict 1-h average carbon monoxide (CO) concentrations. The neuro-fuzzy models are developed at two urban air quality control regions in the Delhi city, India—one, a typical traffic intersection (i.e., Income Tax Office, ITO); and second, an urban straight roadway (i.e., Siri Fort). ITO models have been validated at Siri Fort site and Siri Fort models have been validated at ITO site. The models have been developed for ‘heterogeneous’ traffic conditions and ‘tropical’ meteorology having three meteorological and one traffic characteristic variables as their inputs. Two-year data, from 1 January 1997 to 31 December 1998 has been used to train the model. The models have been tested using data from 1 January to 31 December 1999 at the same site and then validated using data set from 1 January 2004 to 30 June 2005 at different sites. Prediction performances of 1-h average neuro-fuzzy CO models have been found to be satisfactory with predictions accuracy varying from 89% to 93%.

Dépistage des intoxications au monoxyde de carbone (CO) par des médecins généralistes effectuant des visites à domicile

To evaluate the interest of carbon monoxide (CO) detector used by general practionners visiting patients at home.CO detector (cost: 200 euros) was attributed to 300 general practionners visiting at least 20 patients at home per week. Alarm was triggered when ambient CO concentration exceeded 80ppm. Measurement of CO in expired breath was also possible. Activity and alarms were prospectively collected. Circumstances of intoxication were recorded. Evaluation was finally performed. The end-poind was to quantify CO-poisoning detected by the use of the device and the cost of this stratégy.From November 2001 to November 2004, 65 scenes of intoxication with 79 victims were prospectively reported by 12 general practionners. Final evaluation revealed that 23 physicians omitted to declare alarms. Alarm incidence was of 1 for 17.527 visits; with a related cost of approximately 858 euros for 24 months. Ambient carbon monoxide concentration exceeded 200ppm in 25% of cases. Hospital admission was required for 91% of the victims. Hyperbaric oxygen therapy was performed in two cases. General practionners (n=272) considered that CO detector was useful for safety reasons (91%), they wanted to continue the experience, but did not plan to buy such device (59%).Use of CO detectors by general practionners visiting patients at home allowed to identify 65 scenes of CO intoxication. In most cases, the cause of the visit did not suggested CO poisoning. The cost of the device seems to limits its large use.CO detector is a safety tool for both general prationners and patients. Its large use has to be questioned.

1056 Reduced Symptoms and Visceral Sensitivity Is Related to Menstrual Cycle Changes in IBS

Background: Non-specific abdominal pain (NSAP) is one of the most common discharge diagnoses from the emergency department (ED). In many patients an underlying disease is never discovered and the symptoms are often considered functional. NSAP has been associated with depression and headaches, which have both been shown to be exacerbated by exposure to air pollutants. Aim: We studied whether acute exposure to air pollution was independently associated with ED visits for NSAP. Methods: We identified 95,173 patients who visited an Edmonton area ED between April 1, 1992 and March 31, 2002 and were recorded with an ICD-9 code for NSAP (789.0X). We replicated our study by identifying 25,852 ED visits for NSAP at the Jewish General Hospital in Montreal between January 1, 1997 and December 31, 2002. Environmental data were used to calculate the daily mean concentrations for ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and particles <10 (PM10) and <2.5 (PM2.5) micrometers. We performed a timeseries analysis using generalized linear mixed hierarchical models to estimate the percentage value of changes in the relative risk (%RR) with 95% confidence intervals (CI) associated with an increase in the interquratile range (IQR) of SO2, NO2, CO, O3, PM10, and PM2.5 after adjusting for temperature and humidity. Estimates whose 95% CI did not cross 0 were significant. Stratified analyses investigated differential effects by age and gender. Findings: Nearly 2/3 of ED visits for NSAP were by women and the majority of women presented in adolescence and early adulthood. PM10 was significantly associated with NSAP patients aged 15 to 24 years in both Edmonton (%RR = 3.2; 95% CI: 1.1, 5.4) and Montreal (%RR = 8.0; 95% CI: 2.8, 13.5). In women aged 15 to 24 years CO, NO2, and PM10 were positively associated with NSAP in Edmonton [%RR=2.5 (95% CI: 0.4, 4.5); %RR=3.2 (95% CI: 0.4, 6.0); and %RR=3.2 (95% CI: 0.8, 5.6), respectively] and Montreal [%RR =6.0 (95% CI: 2.4, 9.8); %RR=8.2 (95% CI: 2.8, 13.8); and %RR=9.2 (95% CI: 3.4 15.4), respectively]. In contrast, O3 was negatively associated with NSAP in women aged 15 to 24 years in Edmonton (%RR=-4.7; 95% CI: -8.0, -1.4) and Montreal (%RR=-10.6; 95% CI: -16.7, -4.0). Interpretation: Women aged 15 to 24 years were more likely to present to EDs with NSAP when ambient concentrations of CO, NO2, and PM10were elevated. In contrast, O3 exposure appeared to be negatively associated with NSAP. These findings were identified in two geographically distinct metropolitan Canadian cities.

Methaemoglobin and Carboxyhaemoglobin Formation in Human Blood Due to NOx and CO Exposure: A Mathematical Model

Combustion of Liquefied Petroleum Gas (LPG) in household kitchens results in the production of several harmful gases including Carbon Monoxide (CO) and Nitrogen Oxides (NOx). In the present work, an attempt has been made to investigate the effect of such gases on the percent oxygen saturation of blood and a nonlinear exponential model has been proposed based on reaction kinetics to quantify the amount of carboxyhaemoglobin and methaemoglobin formed in blood due to such exposures using a non-invasive technique. The model parameters have been estimated by using the experimental data obtained from exposure of the individuals to different concentrations of CO and NOx. Non-linear regression technique has been used in MATLAB® to optimise the objective function. The model has been validated for %COHb concentration in blood and corresponding data for ambient CO concentration reported in literature. The proposed model can be used to find the concentration of methaemoglobin and carboxyhaemoglobin formed in the blood for low exposures.

Evaluation of the Mesoscale Meteorological Model (MM5)-Community Multi-Scale Air Quality Model (CMAQ) Performance in Hindcast and Forecast of Ground-Level Ozone

This paper presents the first attempt to apply the Mesoscale Meteorological Model (MM5)-Community Multi-Scale Air Quality Model (CMAQ) model system to simulate ground-level ozone (O3) over the continental Southeast Asia (CSEA) region for both hindcast and forecast purposes. Hindcast simulation was done over the CSEA domain for two historical O3 episodes, January 26– 29, 2004 (January episode, northeast monsoon) and March 24–26, 2004 (March episode, southwest monsoon). Experimental forecast was done for next-day hourly O3 during January 2006 over the central part of Thailand (CENTHAI). Available data from 20 ambient monitoring stations in Thailand and 3 stations in Ho Chi Minh City, Vietnam, were used for the episode analysis and for the model performance evaluation. The year 2000 anthropogenic emission inventory prepared by the Center for Global and Regional Environmental Research at the University of Iowa was projected to the simulation year on the basis of the regional average economic growth rate. Hourly emission in urban areas was prepared using ambient carbon monoxide concentration as a surrogate for the emission intensity. Biogenic emissions were estimated based on data from the Global Emissions Inventory Activity. Hindcast simulations (CSEA) were performed with 0.5° ×0.5° resolution, whereas forecast simulations (CENTHAI) were done with 0.1° ×0.1° hourly emission input data. MM5-CMAQ model system performance during the selected episodes satisfactorily met U.S. Environmental Protection Agency criteria for O3 for most simulated days. The experiment forecast for next-day hourly O3 in January 2006 yielded promising results. Modeled plumes of ozone in both hindcast and forecast cases agreed with the main wind fields and extended over considerable downwind distances from large urban areas.

Long-term spatial distributions and trends of ambient CO concentrations in the central Taiwan Basin

Long-term spatial distributions and trends of atmospheric carbon monoxide (CO) concentrations in the central Taiwan Basin were investigated by analysis of CO data obtained from the Taiwan Air Quality Monitoring Network (TAQMN). The influence of meteorological conditions on the CO patterns was also analyzed in this paper. The results showed the highest CO concentrations were found in the vicinity of urban areas with a 13-yr mean value of 0.79±0.16ppm. This was associated with the most intensive anthropogenic CO emissions at the urban sites. For all sites, lower CO levels were consistently observed during the summer season. This was explained by favorable conditions for dispersion and loss of CO via photochemical reactions. Analysis of wind fields and backward trajectories revealed that two types of synoptic sea breezes directly influenced the CO spatial distributions in the basin. During autumn to spring, northerly flow accompanied by pollutants traveled to inland areas, resulting in higher CO concentrations in the remote areas. During summer, breezes coming from the sea or areas to the south with lower CO emissions, resulted in more uniform spatial distributions of CO in the study region. While CO concentrations exhibited decreasing trends, the average CO mixing ratio from 1994 through 2006 decreased at a rate of approximately 0.02ppmyr−1 in the central Taiwan Basin.

Prediction of ambient carbon monoxide concentration using nonlinear time series analysis technique

This study evaluates the potential of nonlinear time series analysis based methods in predicting the carbon monoxide concentration in an urban area. To establish the functional relationship between current and future observations, two models based on local approximations and neural network approximations are used. To compare the performance of the models, an autoregressive integrated moving average model is also applied. The multi-step forecasting capabilities of the models are evaluated.

Estimation of Monthly Average Ambient Air Pollutant Concentrations Using Geographic Information Systems

P-057 Introduction: The epidemiologic literature provides evidence that air pollutant exposures may increase risks of several pregnancy-related health outcomes. The literature also suggests that short-term exposures before or during pregnancy may be more relevant than long-term (e.g.[r], annual) exposures. Thus, we sought a method by which individual short-term air pollutant exposures could be estimated among 1,699 participants of a cohort study of pregnancy. Methods: We developed models to estimate ambient concentrations of carbon monoxide (CO), particulate matter ≤ 10 um in diameter (PM10), and particulate matter ≤ 2.5 um in diameter (PM2.5) within an urban United States region. Using geographic information systems software and publicly available data, we measured traffic, weather, and population characteristics at regional air pollutant monitoring stations. We used multivariable linear models to relate these local characteristics to monthly CO, PM10, and PM2.5 concentrations measured at the stations between 1996 and 2002. By applying the coefficients obtained from these models to local characteristics measured at participants' homes, we estimated residential monthly CO, PM10, and PM2.5 concentrations. We used a split-sample reliability assessment to quantify the agreement between the concentrations measured at the monitoring stations and the estimates obtained by the exposure models. Results: Estimates from the CO and PM2.5 models correlated well with concentrations measured at monitoring stations. The Pearson correlation coefficients (rho) were 0.74 and 0.56, respectively. Root mean square errors for the CO and PM2.5 models were 0.27 ppm and 2.9 ug/m3, respectively. We were unable to develop a satisfactorily predictive PM10 model (rho=0.06). The mean (standard deviation, range) estimated CO and PM2.5 concentrations at participants' residences during the the calendar month of conception were 0.95 ppm (0.30, 0.23–1.97 ppm) and 10.9 ug/m3 (3.5, 2.0–22.2 ug/m3), respectively. Discussion: Using easily accessible data sources and information from a regional air pollutant monitoring network, we were able to estimate monthly CO and PM2.5 concentrations at residential locations within the region. The strong correlations between estimates and measured concentrations suggest that this method can be used to estimate monthly ambient air pollutant exposures in epidemiologic studies.

The Contribution of Hemolysis to Early Jaundice in Normal Newborns

Neonatal jaundice is the result of an imbalance between bilirubin production and elimination, and our objective was to clarify the contribution of an increase in bilirubin production to hyperbilirubinemia in newborns. We measured the end-tidal carbon monoxide concentration corrected for ambient carbon monoxide concentration in 108 jaundiced newborns (total serum bilirubin level >75th percentile) and 164 control newborns in our well-infant nursery, for the first 4 days after birth. Mean end-tidal carbon monoxide levels decreased in the control infants in the first 4 days but increased in the hyperbilirubinemic group. The differences between the jaundiced and nonjaundiced infants were statistically significant on all days. Before hospital discharge, most infants with bilirubin levels >75th percentile are producing significantly more bilirubin than those with lower bilirubin levels. Because the ability of newborns to conjugate bilirubin is significantly impaired in the first few days, even a small increase in the rate of production can contribute to the development of hyperbilirubinemia. These data suggest that increased heme catabolism is an important mechanism responsible for hyperbilirubinemia in the first 4 days after birth.

Validation of the emission inventory in the Sao Paulo Metropolitan Area of Brazil, based on ambient concentrations ratios of CO, NMOG and NO x and on a photochemical model

In recent years, photochemical air pollution has become a significant problem in the São Paulo Metropolitan Area (SPMA). For some air pollutants, especially ozone and particulate matter, concentrations in excess of national air quality standards have been registered. According to data published by the State Environmental Agency (CETESB), approximately 90% of ozone precursors are emitted into the atmosphere by the vehicle fleet [CETESB, 2000. Relatório de Qualidade do ar do Estado de Sao Paulo, 1999; CETESB, 2002. Relatório de Qualidade do ar do Estado de Sao Paulo, 2004]. The estimation of precursor emissions speciation is a rather complex task. Estimating spatial and temporal variation of vehicle emissions is the greatest source of uncertainty. As in other locales, data regarding motor vehicle emissions are scarce. Due to the considerable discrepancies in emission inventories reported in various regions of the world, we evaluated the official emission inventories of non-methane organic gas (NMOG) and nitrogen oxides (NO x ) using an observation-based approach. Ratios of NO x /carbon monoxide (CO) and NMOG/CO were calculated from ambient measurements taken in the early morning (0700–0800) during July and August of 1999. This top-down approach assumes that early morning ambient concentrations of CO, NO x and NMOG are dominated by motor vehicle emissions, and that the photochemical process has not substantially affected the concentrations. Based on these ratios and on the assumption that official inventory of CO emissions is reasonably accurate, on-road motor vehicle emissions of NO x seem to be significantly overestimated and NMOG emissions slightly underestimated. An Eulerian photochemical model, using both the revised motor vehicle emission inventory and the original official emissions provided by CETESB, was applied to an episodic air pollution event in the SPMA (9–12 August 1999). Meteorology fields were obtained from the CALMET model. When the revised, rather than the official, emission inventories are used, ozone and NO concentrations predicted by the California Institute of Technology (CIT) airshed model more closely match observed values.