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PubMed2003

Short-term effects of air pollution on daily asthma emergency room admissions.

Many time-series studies have shown positive associations between air pollutants and asthma morbidity. However, few studies have included pollen as a potential confounder when examining this relationship. This study analysed the short-term association between air pollutants (sulphur dioxide (SO2), particles measured with a median aerodynamic diameter of <10 microm (PM10), nitrogen dioxide (NO2) and ozone (O3)) and asthma emergency room admissions in Madrid, Spain, in 1995-1998, adjusting for four types of pollen with allergenic potential (Olea europaea, Plantago sp., Poaceae and Urticaceae). Data were analysed using autoregressive Poisson regression and generalised additive models (GAM). The strongest associations were observed at 1 day lag for O3, and 3 days lag for the remaining pollutants. Using Poisson regression, a single-pollutant model showed that a 10-microg x m(-3) rise in pollutant level led to relative risks of: 1.039 for PM10; 1.029 for SO2; 1.033 for NO2; and 1.045 for O3. Adjustment for the different types of pollen led to no substantial variation in these associations. In the multipollutant models for cold-season pollutants (including PM10, SO2 and the four types of pollen) and photochemical pollutants (including NO2, O3 and the four types of pollen) the associations for PM10, NO2 and O3 held, but no relationship with SO2 was evident. GAM analysis yielded the same results, both in terms of lags and of quantification of the effect for all pollutants. In conclusion, the usual air pollution levels in Madrid were associated with an increase in asthma emergency room admissions, and this association remained controlling for the presence of ambient pollen.

Acute Disease↗
PubMed1997

The role of particulate size and chemistry in the association between summertime ambient air pollution and hospitalization for cardiorespiratory diseases.

In order to address the role that the ambient air pollution mix, comprised of gaseous pollutants and various physical and chemical measures of particulate matter, plays in exacerbating cardiorespiratory disease, daily measures of fine and coarse particulate mass, aerosol chemistry (sulfates and acidity), and gaseous pollution (ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide) were collected in Toronto, Ontario, Canada, in the summers of 1992, 1993, and 1994. These time series were then compared with concurrent data on the number of daily admissions to hospitals for either cardiac diseases (ischemic heart disease, heart failure, and dysthymias) or respiratory diseases (tracheobronchitis, chronic obstructive long disease, asthma, and pneumonia). After adjusting the admission time series for long-term temporal trends, seasonal variations, the effects of short-term epidemics, day of the week effects, and ambient temperature and dew point temperature, positive associations were observed for all ambient air pollutants for both respiratory and cardiac diseases. Ozone was least sensitive to adjustment for the gaseous and particulate pollution measures. However, the association between the health outcomes and carbon monoxide, fine and coarse mass, sulfate levels and aerosol acidity could be explained by adjustment for exposure to gaseous pollutants. Increases in ozone, nitrogen dioxide, and sulfur dioxide equivalent to their interquartile ranges corresponded to an 11% and 13% increase in daily hospitalizations for respiratory and cardiac diseases, respectively. The inclusion of any one of the particulate air pollutants in multiple regression models did not increase these percentages. Particle mass and chemistry could not be identified as an independent risk factor for the exacerbation of cardiorespiratory diseases in this study beyond that attributable to climate and gaseous air pollution. We recommend that effects of particulate matter on health be assessed in conjunction with temporally covarying gaseous air pollutants.

Air Pollutants↗
PubMed2003

Air pollution and hospital admissions for ischemic heart diseases among individuals 64+ years of age residing in Seoul, Korea.

There is increased evidence that air pollution may be associated with cardiovascular disease. The authors' prior investigations on the association between air pollution exposure and stroke mortality led to the current study, which was conducted to assess the effects of ambient air pollution on ischemic cardiovascular diseases among the elderly population (i.e., males and females 64+ yr of age) in Seoul, Korea. The authors estimated the relative risks of hospitalization associated with an interquartile range (IQR) increase in pollution concentrations; a generalized additive Poisson model was used to conduct a time-series analysis of the counts. The concentrations of ambient air pollutants were lower than the current recommendations for air quality in Korea. The estimated relative risks of hospitalization associated with an IQR were 1.05 (95% confidence interval [CI] = 1.01, 1.10) for particulate matter less than or equal to 10 microm in diameter (PM10) (IQR = 40.4 microg/m3); 1.10 (95% CI = 1.05, 1.15) for ozone (IQR = 21.7 ppb); 1.08 (95% CI = 1.03, 1.14) for nitrogen dioxide (IQR = 14.6 ppb); 1.07 (95% CI = 1.01, 1.13) for carbon monoxide (IQR = 1.0 ppm); and 0.95 (95% CI = 0.90, 1.01) for sulfur dioxide (IQR = 4.4 ppb). The authors observed that sulfur dioxide was a significant risk factor for ischemic heart disease-related hospital admissions during the summer months (i.e., June, July, and August) (relative risk = 1.32; 95% CI = 1.08, 1.62). Hospital admissions for ischemic heart diseases were associated significantly with daily variations in levels of ambient air pollutants. These findings may provide new insights into the possible pathologic mechanisms involving air pollutants, and they support the hypothesis that the elderly appear to be at particular risk from the effects of air pollution, at pollutant levels lower than the standards commonly adopted by many countries.

Age Factors↗
PubMed2003

Groundwater abstraction pollution risk assessment.

A generic groundwater pollution risk assessment methodology has been developed to enable the evaluation and ranking of the potential risk of pollution to groundwater abstractions. The ranking can then be used to prioritise risk management or mitigation procedures in a robust and quantifiable framework and thus inform business investment decisions. The risk assessment consider the three components of the pollution transport model: source-pathway-receptor. For groundwater abstractions these correspond to land use (with associated pollutants and shallow subsurface characteristics), aquifer and the abstraction borehole. An hierarchical approach was chosen to allow the risk assessment to be successfully carried out with different quality data for different parts of the model. The 400-day groundwater protection zone defines the catchment boundary that form the spatial limit of the land use audit for each receptor. A risk score is obtained for each land use (potential pollution source) within the catchment. These scores are derived by considering the characteristics (such as load, persistence and toxicity) of all pollutants pertaining to each land use, their on-site management and the potential for the unsaturated subsurface to attenuate their effects in the event of a release. Risk scores are also applied to the aquifer characteristics (as pollutant pathway) and to the abstraction borehole (as pollutant receptor). Each risk score is accompanied by an uncertainty score which provides a guide to the confidence in the data used to compile the risk assessment. The application of the methodology has highlighted a number of problems in this type of work and results of initial case studies are being used to trial alternative scoring methods and a more simplified approach to accelerate the process of pollution risk assessment.

Models, Theoretical↗
PubMed2006

Remediating polluted soils.

This review focuses on treatment-based remediation of soils and the acquisition of data to support and monitor this remediation. Only in the last two decades has significant progress been made in regulating for soil pollution, with a parallel development of methodologies for soil assessment and remediation. However, soil complexity remains a problem for pollutant measurements relevant to environmental risk and informative to the design or evaluation of remediation technologies. Understanding the distribution of pollutants between different soil phases and the kinetics of transfer between these pools is fundamental to prediction for these processes; further progress is needed to characterise less accessible pollutant pools and to develop guidelines for their analysis. Available remediation options include physical, chemical and biological treatments, and these options offer potential technical solutions to most soil pollution. However, selecting the most appropriate approach requires detailed information on how pollutants interact with soil physio-chemical properties. Only general information is available as to the effectiveness of specific treatment systems for particular soil type-pollutant combinations. Given the high degree of heterogeneity in physio-chemical characteristics and pollutant distribution of affected soils, prediction of treatment timescales and levels of residual contamination remains a problem. On sites with a range of organic and inorganic pollutants present, combinations of different treatment approaches may offer the best prospect for effective remediation. Further work is needed to provide evidence that residual contamination does not pose significant risk and to evaluate effects of treatments on general soil function in relation to this contamination.

Conservation of Natural Resources↗
PubMed2001

Toward the bioremediation of dioxin-polluted soil: structural and functional analyses of in situ microbial populations by quinone profiling and culture-dependent methods.

In order to obtain basic information toward the bioremediation of dioxin-polluted soil, microbial communities in farmland soils polluted with high concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were studied by quinone profiling as well as conventional microbiological methods. The concentration of PCDD/Fs in the polluted soils ranged from 36 to 4,980 pg toxicity equivalent quality (TEQ) g(-1) dry weight of soil. There was an inverse relationship between the levels of PCDD/Fs and microbial biomass as measured by direct cell counting and quinone profiling. The most abundant quinone type detected was either MK-6 or Q-10. In addition, MK-8, MK-8(H2), and MK-9(H8) were detected in significant amounts. Numerical analysis of quinone profiles showed that the heavily polluted soils (> or = 1,430 pg TEQ g(-1)) contained different community structures from lightly polluted soils (< or = 56 pg TEQ g(-1)). Cultivation of the microbial populations in the heavily polluted soils with dibenzofuran or 2-chlorodibenzofuran resulted in enrichment of Q-10-containing bacteria. When the heavily polluted soil was incubated in static bottles with autoclaved compost as an organic nutrient additive, the concentrations of PCDD/Fs in the soil were decreased by 22% after 3 months of incubation. These results indicate that dioxin pollution exerted a significant effect on microbial populations in soil in terms of quantity, quality, and activity. The in situ microbial populations in the dioxin-polluted soil were suggested to have a potential for the transformation of PCDD/Fs and oxidative degradation of the lower chlorinated ones thus produced.

Biodegradation, Environmental↗
PubMed2004

Relation between children's height and outdoor air pollution from coal-burning sources in the British 1946 birth cohort.

OBJECTIVE: Air pollution is associated with a number of health outcomes in childhood. In this study, we investigated whether air pollution is related to children's height. METHODS: The 1946 British birth cohort study recruited 5,362 children born in 1 week in March 1946. Height was measured when the children were aged 2, 4, 6, 7, 11 and 15 years. Data on socio-economic conditions and other characteristics were obtained in interviews. Areas of children's residence were categorised into four groups of air pollution on the basis of published coal-consumption data. RESULTS: After controlling for socio-economic factors, we found that air pollution was associated with children's height at several ages. The association, adjusted for socio-economic factors, was strongest at the age of 7 years, when children in the most polluted areas were 1.2 (95% confidence interval 0.5-1.8) cm shorter than those in the least polluted areas. After the age of 7 years the effect of air pollution diminished and disappeared by the age of 15 years. Further adjustment for birth weight and respiratory illness in childhood did not change this pattern. CONCLUSIONS: Children's height was inversely associated with air pollution, but the magnitude of the effect depended on age. However, the biological mechanisms linking children's growth with air pollution are not evident, and it remains to be confirmed whether the relationship is genuine and causal.

Adolescent↗
PubMed2005

Heavy metal pollution affects dawn singing behaviour in a small passerine bird.

Although several studies have suggested that behavioural measures may be more comprehensive than other biomarkers for indicating an organism's health or welfare, this has rarely been investigated in free-living terrestrial vertebrates. Here we examine the expression of dawn singing behaviour in a free-living small songbird in relation to environmental pollution. We compared the singing behaviour of male great tits Parus major inhabiting an area extremely polluted with heavy metals with that of males inhabiting areas of low(er) pollution (at 4 and 20 km distance from the pollution source). Males at the most polluted site had a significantly smaller repertoire size than males at the two other sites. They also produced a significantly lower total amount of song during the dawn chorus than the males at a distance of 4 km from the pollution source. Our results, although non-experimental and obtained in field conditions, strongly suggest that heavy metal pollution might affect the expression of singing behaviour. Taking into account that previous studies were not able to detect clear, straightforward differences between the health of great tits at the most polluted site and at 4 km distance from the pollution source, our results suggest that the singing behaviour of great tits may be a useful indicator of environmental stress at the population level.

Analysis of Variance↗
PubMed2004

Increasing allergy potency of Zinnia pollen grains in polluted areas.

There is much evidence that allergic symptoms represent a major health problem in polluted cities. The aim of this research is to elucidate some microscopic effects of air pollutants on pollen structure, proteins, and allergenicity. A scanning electron microscopy study of pollen grains indicated that in polluted areas, airborne particles accumulate on the surface of pollen grains and change the shape and tectum of pollen. Also, many vesicles are released from polluted pollen grains and the pollen material agglomerates on the surface of pollen grains. SDS-PAGE revealed that different proteins exist in mature and immature pollen grains. There were no significant differences between protein bands of polluted and nonpolluted pollen grains, but in polluted pollen, protein content decreases in response to air pollution, causing the release of pollen proteins. The results indicate that mature pollen have more allergenicity than immature pollen. According to the experiments polluted pollen grains are more effective than nonpolluted pollen grains in inducing allergic symptoms. Air pollutants can cause allergic symptoms, but when associated with allergen pollen grains, their allergenicity power is increased.

Air Pollutants↗
PubMed2006

Adverse health effects of outdoor air pollutants.

Much research on the health effects of outdoor air pollution has been published in the last decade. The goal of this review is to concisely summarize a wide range of the recent research on health effects of many types of outdoor air pollution. A review of the health effects of major outdoor air pollutants including particulates, carbon monoxide, sulfur and nitrogen oxides, acid gases, metals, volatile organics, solvents, pesticides, radiation and bioaerosols is presented. Numerous studies have linked atmospheric pollutants to many types of health problems of many body systems including the respiratory, cardiovascular, immunological, hematological, neurological and reproductive/ developmental systems. Some studies have found increases in respiratory and cardiovascular problems at outdoor pollutant levels well below standards set by such agencies as the US EPA and WHO. Air pollution is associated with large increases in medical expenses, morbidity and is estimated to cause about 800,000 annual premature deaths worldwide [Cohen, A.J., Ross Alexander, H., Ostro, B., Pandey, K.D., Kryzanowski, M., Kunzail, N., et al., 2005. The global burden of disease due to outdoor air pollution. J Toxicol Environ Health A. 68: 1-7.]. Further research on the health effects of air pollution and air pollutant abatement methods should be very helpful to physicians, public health officials, industrialists, politicians and the general public.

Air Pollutants↗
PubMed2006

Effects of São Paulo air pollution on the upper airways of mice.

The nose is the first region of the respiratory tract to come in contact with airborne pollutants. Previous studies have shown that the nasal mucosa can be altered in response to air pollution. In this study, we quantified neutral and acidic mucus in three different levels of the nasal cavity of mice exposed to ambient levels of air pollution in the city of São Paulo, Brazil. Two groups of 6-day-old male Swiss mice were placed in two exposure chambers. Mice were maintained in the chambers 24 h/day, 7 days/week for 5 months. The first chamber contained an air filter device (clean chamber; n=20), whereas the second one received ambient air pollution (polluted chamber; n=20). We measured the concentration of PM(2.5), nitrogen dioxide (NO2), and black carbon inside both chambers. The nasal cavity was transversely sectioned at three specific anatomic locations (proximal, medial, and distal levels) and submitted to quantitative analysis of the amounts of neutral and acidic mucosubstances. We observed a 37.85% decrease in NO2, 54.77% decrease in PM(2.5), and 100% decrease in black carbon concentration in the clean chamber compared to the polluted chamber. Significant differences between polluted and clean chambers were observed in the epithelium lining the septum of proximal and medial levels of the nasal mucosa, with an increase in the percentage of acidic mucus in the polluted chamber (P=0.037, proximal level; P=0.023, medial level). We conclude that prolonged exposure to low levels of ambient air pollution from an early age shows evidence of causing secretory changes in the nasal cavity of mice, with increased production of acidic mucosubstances.

Air Pollutants↗
PubMed2005

Winter air pollution and disease parameters in advanced chronic obstructive pulmonary disease panels residing in Denver, Colorado.

BACKGROUND: Ambient pollution might worsen chronic obstructive pulmonary disease (COPD). OBJECTIVE: We explored the associations of pollution to pulmonary function, rescue medication, and symptoms over 2 winters in 2 panels of subjects with advanced COPD in Denver, Colorado. METHODS: Subjects measured lung function and recorded symptoms and rescue medications. Daily ambient pollution concentrations for particulate matter (PM(10) and PM(2.5)), carbon monoxide (CO), and nitrogen dioxide (NO(2)) were obtained for Denver. Estimated effects of pollution on outcomes were derived for the same day and 1 and 2 days after pollution measurements (lags 0, 1, and 2, respectively). RESULTS: Sixteen (mean age, 65.8 years; mean FEV 1 , 42.3% of predicted value) and 18 (mean age, 67.4 years; mean FEV 1 , 39.4% of predicted value) subjects participated in the first and second winters, respectively. There were no differences in demographic or disease characteristics between the 2 panels. In the first winter no detrimental associations were found. In the second winter, however, there were significant detrimental associations of CO in the morning and PM(10), CO, and NO(2) in the evening, increasing medication use at lag 0. Total symptom score increased at lag 0 with NO(2). The concentrations of particulates were increased in the second winter compared with in the first winter, and this winter was colder and more humid. CONCLUSIONS: In the second winter, subjects with severe COPD had worse lung function at lags 0 and 1 and increased rescue medication at lag 0 with increases in ambient air pollution. The effects of pollution varied between the 2 winters, perhaps related to levels of pollution and weather patterns. Significant effects were seen despite ambient pollution levels that conformed to US Environmental Protection Agency standards.

Aged↗
PubMed2004

Pollution loads in urban runoff and sanitary wastewater.

While more attention has been paid in recent years to urban point source pollution control through the establishment of wastewater treatment plants in many developing countries, no considerable planning nor any serious measures have been taken to control urban non-point source pollution (urban stormwater runoff). The present study is a screening analysis to investigate the pollution loads in urban runoff compared to point source loads as a first prerequisite for planning and management of receiving water quality. To compare pollutant loads from point and non-point urban sources, the pollutant load is expressed as the weight of pollutant per hectare area per year (kg/ha.year). Unit loads were estimated in stormwater runoff, raw sanitary wastewater and secondary treatment effluents in Isfahan, Iran. Results indicate that the annual pollution load in urban runoff is lower than the annual pollution load in sanitary wastewater in areas with low precipitation but it is higher in areas with high precipitation. Two options, namely, advanced treatment (in lieu of secondary treatment) of sanitary wastewater and urban runoff quality control systems (such as detention ponds) were investigated as controlling systems for pollution discharges into receiving waters. The results revealed that for Isfahan, as a low precipitation urban area, advanced treatment is a more suitable option, but for high precipitation urban areas, urban surface runoff quality control installations were more effective for suspended solids and oxygen-demanding matter controls, and that advanced treatment is the more effective option for nutrient control.

Cities↗
PubMed2000

Public-health impact of outdoor and traffic-related air pollution: a European assessment.

BACKGROUND: Air pollution contributes to mortality and morbidity. We estimated the impact of outdoor (total) and traffic-related air pollution on public health in Austria, France, and Switzerland. Attributable cases of morbidity and mortality were estimated. METHODS: Epidemiology-based exposure-response functions for a 10 microg/m3 increase in particulate matter (PM10) were used to quantify the effects of air pollution. Cases attributable to air pollution were estimated for mortality (adults > or = 30 years), respiratory and cardiovascular hospital admissions (all ages), incidence of chronic bronchitis (adults > or = 25 years), bronchitis episodes in children (< 15 years), restricted activity days (adults > or = 20 years), and asthma attacks in adults and children. Population exposure (PM10) was modelled for each km2. The traffic-related fraction was estimated based on PM10 emission inventories. FINDINGS: Air pollution caused 6% of total mortality or more than 40,000 attributable cases per year. About half of all mortality caused by air pollution was attributed to motorised traffic, accounting also for: more than 25,000 new cases of chronic bronchitis (adults); more than 290,000 episodes of bronchitis (children); more than 0.5 million asthma attacks; and more than 16 million person-days of restricted activities. INTERPRETATION: This assessment estimates the public-health impacts of current patterns of air pollution. Although individual health risks of air pollution are relatively small, the public-health consequences are considerable. Traffic-related air pollution remains a key target for public-health action in Europe. Our results, which have also been used for economic valuation, should guide decisions on the assessment of environmental health-policy options.

Adolescent↗
PubMed2003

Toxic risk of surface water pollution--six years of experience.

Assessment of an ecological quality of surface water is necessary for effective protection, abatement and successive revitalisation of river ecosystems. This quality is primarily given by biological impact of surface water pollution. Substances contained in pollution are frequently toxic to aquatic organisms. Risk of chronic impact of surface water pollution is very often underestimated due to hidden long time action of pollutants. Proper estimation of the risk is not possible from results of chemical analyses and data of substances' toxicity. Chemical analyses are not able to detect all substances presented in water including the products of reactions between them. In addition, a simultaneous presence of substances can modify their final effect on aquatic organisms. Therefore, a complex method of assessment of toxic risk of surface water pollution based on ecotoxicological approach was developed. The toxic risk of surface water pollution is determined from results of evaluation of toxic risk of organic part and inorganic part of surface water pollution. Resultant degree of toxic risk of total pollution is given by the highest degree detected in any part of the water pollution. Presented method, which is routinely used for monitoring in the Czech part of the Odra river basin, was fully standardised and published in the form of the Czech branch technical norm of water management (TNV) in the year 2000.

Animals↗
PubMedDate not supplied

An assessment of the effects of crude oil pollution on soil properties, germination and growth of maize (Zea mays) using two crude types--Forcados light and Escravos light.

The effect of crude oil pollution on soil properties, germination and height of maize (Zea mays) was investigated under natural environment in three separate pot experiments. Two crude oil types--Forcados light and Escravos light were used. In Experiment 1, the effect of crude oil application on germination using high pollution levels of 5, 15, 25 and 40 mL kg(-1) of soil was assessed. In Experiment 2, the effect of crude oil application on maize plant height using the same pollution levels was assessed. The last experiment (Experiment 3) was used to test for the effects of crude oil application on maize plant height using lower levels of pollution (1.0, 1.5, 2.0 and 2.5 mL kg(-1) of soil). Soil samples were collected before, during and after the experiment and analyzed for some physical and chemical properties. Results obtained showed variation in chemical properties of soil. % organic matter increased from 1.34 to 2.62% in polluted soils. Available P decreased from 15.00 ppm in control to between 7.34 and 5.42 in soils polluted with 'high' levels of crude oil. Statistical analysis of height data showed that crude oil inhibited the growth of maize at high pollution levels. High levels of pollution also inhibited germination and for Escravos light there was no germination at 40 mL kg(-1) soil level of crude oil pollution.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Long-term ambient air pollution levels in four Chinese cities: inter-city and intra-city concentration gradients for epidemiological studies.

The field data collection of an air pollution epidemiologic study was carried out from 1993 to 1996 in four Chinese cities of Lanzhou, Chongqing, Wuhan, and Guangzhou. In each city, an urban district and a suburban district were selected. Ambient concentrations of total suspended particles (TSP), size-fractionated particulate matter including PM2.5, PM2.5-10, and PM10, sulfur dioxide (SO2), and oxides of nitrogen (NOx) were measured in these districts. The results indicate the presence of wide inter-city and intra-city gradients in long-term ambient levels of these measured pollutants. Across the eight districts, the 1993-1996 4-year means of TSP, SO2, and NOx ranged from 198 to 659 microg/m3, from 14.6 to 331 microg/m3, and from 31.5 to 239 microg/m3, respectively, and the 1995-1996 2-year means of PM2.5, PM2.5-10, and PM10 ranged from 51.5 to 142 microg/m3, from 29.2 to 107 microg/m3, and from 80.7 to 232 microg/m3, respectively. These pollution ranges substantially extended the upper end of the pollution ranges of previous air pollution epidemiologic studies conducted in North America and Europe. In each district, significant correlations among the measured pollutants were observed for daily concentrations. However, the gradient patterns in long-term means of different pollutants were different across the eight districts. (e.g., PM2.5-10 and TSP were highest in the Lanzhou urban district, PM2.5 and PM10 were highest in the Guangzhou urban district, SO2 was highest in the Chongqing urban district, and NOx was highest in the Guangzhou urban district). In general, seasonal variations were present in the ambient concentrations with high levels often occurring in winter months. The eight districts may be classified into four district clusters based on integrated levels of all measured pollutants. These features of the ambient air pollution have important implications for epidemiological studies and may provide unique opportunities to study exposure-effects relationships in the four Chinese cities.

Air Pollutants↗
PubMed2005

Monitor-to-monitor temporal correlation of air pollution in the contiguous US.

Numerous studies have reported short-term associations between ambient air pollution concentrations and mortality and morbidity. Particulate matter (PM) was often implicated as the most significant predictor of the health outcomes among the various air pollutants. However, a question remains as to the potential role played by the relative error of exposure estimation associated with each pollutant in defining their relative strengths of association. While most of the recent studies on PM exposure measurements have focused on the temporal correlation between personal exposures and the concentrations observed at ambient air quality monitors (within a few miles from the subjects), there have been few studies that systematically evaluated spatial uniformity of temporal correlation of air pollution within the scale of a city (several tens of miles) for which mortality or morbidity outcomes are aggregated in time-series studies. In this study, spatial uniformity of temporal correlation was examined by computing monitor-to-monitor correlation using available multiple monitors for PM(10) and gaseous criteria pollutants (NO(2), SO(2), CO, and O(3)) in the nationwide data between 1988 and 1997. For each monitor, the median of temporal correlation with other monitors within the Air Quality Control Region (AQCR) was computed. The resulting median monitor-to-monitor correlation was modeled as a function of qualitative site characteristics (i.e., land-use, location-setting, and monitoring-objective) and quantitative information (median separation distance, longitude/latitude or regional indicators) for each pollutant. Generalized additive models (GAM) were used to fit the smooth function of the separation distance and regional variation. The intercepts of the models across pollutants showed the overall rankings in monitor-to-monitor correlation on the average to be: O(3), NO(2), and PM(10), (r approximately 0.6 to 0.8)>CO (r<0.6)>SO(2) (r<0.5). Both the separation distance and regional variation were important predictors of the correlation. For PM(10), for example, the correlation for the monitors along the East Coast was higher by approximately 0.2 than western regions. The qualitative monitor characteristics were often significant predictors of the variation in correlation, but their impacts were not substantial in magnitude for most categories. These results suggest that the apparent regional heterogeneity in PM effect estimates, as well as the differences in the significance of health outcome associations across pollutants, may in part be contributed to by the differences in monitor-to-monitor correlations by region and across pollutants.

Air Pollutants↗