Inhalable Particulate Matter Concentration Research Articles

Influence of “Coal-to-Gas” Policy in the Beijing-Tianjin-Hebei Region and Surrounding Area on the Air Quality

In recent years, extreme weather, such as haze, has occurred frequently; air pollution has been aggravated; and the concentration of inhalable particulate matter in the air has been very high in China, especially in Northern China. The problem of atmospheric environment needs to be solved urgently. Meanwhile, the energy problem pertains to the country’s major strategy. Adjusting the energy structure can not only solve the problem of environmental pollution, but also change the energy pattern of our country. Thus, the “Coal-to-Gas” policy has been implemented. This paper examines the influence of the “Coal-to-Gas” policy on the air quality in the Beijing-Tianjin-Hebei Region, which also has important practical significance for further optimization and control of the policy.

Analysis of the spatial characteristics of inhalable particulate matter concentrations under the influence of a three-dimensional landscape pattern in Xi'an, China

Atmospheric inhalable particulate matter increases the risks of damage to the respiratory system and cardiovascular diseases among residents, and threatens urban health and sustainable development. In this study, a geographically weighted regression model was constructed using spatial statistical quantification methods to explore the spatial variability characteristics of different influencing factors of the distribution of the atmospheric inhalable particulate matter concentration. Based on a visual simulation and redundancy analysis, the spatial distribution characteristics of the atmospheric inhalable particulate matter concentration in the main urban area of Xi'an were revealed. The results of the study are illustrated as daily average situations, and the selected set of urban landscape metrics performed well at explaining the variation in the atmospheric inhalable particulate matter concentration. Furthermore, the degree of building height variability, the connectivity of green space patches, the number of air-polluting enterprises, and the area of residential land had greater impacts than other factors on the PM2.5 concentration in winter. The degree of building clustering, the shape complexity of the green space patches, the elevation and the distance from a motorway, on the other hand, had some influence on the PM10 concentration in winter. From the perspective of the landscape pattern, it was found that the higher the density and area of green space patches were, the more complex the shape and the higher the connectivity were; additionally, the higher the spatial contiguity was, the lower the concentration of inhalable particulate matter in the atmosphere in winter. The concentrations of inhalable particulate matter in winter increased with the average heights, densities, and volumes of the architectural landscape; and increased with the roughness of the underlying surface, the height variation and building clustering. To the best of our knowledge, this study is the first to apply a geographically weighted regression model to the Guanzhong Basin, a heavily polluted region in China, and provides a scientific basis for urban planning, air pollution control, and public health policy formulation, thus promoting the sustainability of the urban environment.

Does underweight amplify the relationship between short-term particulate matter exposure and blood pressure in children and adolescents: a large cross-sectional study in a metropolis of China.

Overweight/obesity modified the effects of ambient particulate matter (PM) exposure on blood pressure (BP). This study aims to assess whether interaction of underweight and short-term PM exposure on BP exists in Chinese children. A cross-sectional analysis including 144,513 children aged 6 to 17years in 2016 Health Promotion Program for Children and Adolescents of Suzhou, China, was performed. Daily concentrations of inhalable PM (PM10) and fine PM (PM2.5) were extracted from air monitoring stations close to students' schools. We applied generalized linear mixed-effects models to estimate the interactions. Estimated changes (95% confidence intervals (CIs)) of systolic BP (SBP), diastolic BP (DBP), and odds ratios (ORs) (95% CIs) for prevalence of HBP were calculated. Significant interactions between PM and underweight on BP and prevalence of high BP (HBP) were observed. For example, at lag 6, the ORs (95% CIs) for HBP by each 10μg/m3 changes of PM2.5 were 1.066 (1.039, 1.093) and 1.036 (1.028, 1.043) among underweight and normal weight subjects, respectively; these values for PM10 were 1.048 (1.031, 1.065) and 1.025 (1.021, 1.030). At lag 5, the increases of SBP for PM2.5 were 0.32 (95% CI 0.22, 0.43) mmHg and 0.23 (95% CI 0.29, 0.26) mmHg, while changes of DBP were 0.27 (95% CI 0.18, 0.35) mmHg and 0.19 (95% CI 0.16, 0.21) mmHg among underweight and normal weight subjects, respectively. Stratified analyses demonstrated that these interactions were only obtained in males. Effects of short-term PM exposure on BP and prevalence of HBP are enhanced in underweight children and adolescents.

Assessing the relationship between surface levels of PM2.5 and PM10 particulate matter impact on COVID-19 in Milan, Italy

The novel coronavirus disease (COVID-19) is a highly pathogenic, transmittable and invasive pneumococcal disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which emerged in December 2019 and January 2020 in Wuhan city, Hubei province, China and fast spread later on the middle of February 2020 in the Northern part of Italy and Europe.This study investigates the correlation between the degree of accelerated diffusion and lethality of COVID-19 and the surface air pollution in Milan metropolitan area, Lombardy region, Italy. Daily average concentrations of inhalable particulate matter (PM) in two size fractions PM2.5, PM10 and maxima PM10 ground level atmospheric pollutants together air quality and climate variables (daily average temperature, relative humidity, wind speed, atmospheric pressure field and Planetary Boundary Layer-PBL height) collected during 1 January–30 April 2020 were analyzed. In spite of being considered primarily transmitted by indoor bioaerosols droplets and infected surfaces, or direct human-to-human personal contacts, it seems that high levels of urban air pollution, weather and specific climate conditions have a significant impact on the increased rates of confirmed COVID-19 Total number, Daily New and Total Deaths cases, possible attributed not only to indoor but also to outdoor airborne bioaerosols distribution. Our analysis demonstrates the strong influence of daily averaged ground levels of particulate matter concentrations, positively associated with average surface air temperature and inversely related to air relative humidity on COVID-19 cases outbreak in Milan. Being a novel pandemic coronavirus (SARS-CoV-2) version, COVID-19 might be ongoing during summer conditions associated with higher temperatures and low humidity levels. Presently is not clear if this protein “spike” of the new coronavirus COVID-19 is involved through attachment mechanisms on indoor or outdoor airborne aerosols in the infectious agent transmission from a reservoir to a susceptible host in some agglomerated urban areas like Milan is.

Variation Characteristics of Mass Concentration of Inhalable Particles in Qingdao, China

The geographical condition of Qingdao, China is relatively special; the transport of various inland pollutants, the emissions of marine aerosol and local pollutants will have an impact on the changes of atmospheric aerosol concentration. By using the stability classification method, trajectory clustering analysis and the NOAA HYSPLIT model, the seasonal distribution characteristics of atmospheric inhalable particulate matter concentration in Qingdao, China and its relationship with meteorological conditions, mixed layer height, and the seasonal characteristics of Qingdao pollutant transport were analyzed. The results show that the variation trends of PM2.5 and PM10 were about the same, and there are obvious seasonal differences, which are high in winter and spring, and low in summer and autumn. The concentration of inhalable particulate matter has a negative correlation with temperature, wind speed and relative humidity. The concentration of inhalable particulate matter is distinct in different relative humidity ranges. When the wind speed is less than 3 - 4 m/s, there are more inhalable particles, while the mass concentration shows obvious reduction with the wind speed more than 4 m/s. There is a significant negative correlation between the mass concentration of pollutants and the daily maximum mixed layer height. The larger the concentration of pollutants, the smaller the thickness of the daily largest mixed layer. Conversely, the smaller the mass concentration of pollutants, the larger the thickness of the daily largest mixed layer. The pollutant transport in Qingdao has obvious seasonal characteristics. The air mass in spring, autumn and winter is mainly medium-long distance transport from Mongolia and southern Russia, and medium-short distance transport from Inner Mongolia and northeast of China. The source of air masses in summer is mainly transported from the eastern and sea areas.

Simulation of the Impact of Urban Forest Scale on PM2.5 and PM10 based on System Dynamics

In the context of ecological civil construction in China, afforestation is highly valued. Planting trees can improve air quality in China’s large cities. However, there is a lack of scientific analysis quantifying the impact urban forest scale has on the air quality, and what scale is advisable. The problem still exists of subjective decision-making in afforestation. Similar studies have rarely analyzed the long-term effect research of urban forests on air improvement. Using as an example, the city of Wuhan, this paper identifies the regularity between particulate matter concentration and adsorption of sample leaves, and establishes a system dynamics model of "economy, energy and atmospheric environment.” By combining this regularity with the model, the long-term impact of forest scale on particulate matter and atmospheric environment was simulated. The results show that if the forest coverage rate reaches at least 30%, the annual average concentrations of inhalable particulate matter (PM10) and fine particulate matter (PM2.5) can both reach the Grade I limit of national Ambient Air Quality Standard by 2050. The current forest cover is 22.9% of the administrative area. Increasing the forest cover by 600 km2 would increase this percentage to 30% of the total area. In the long run (by the year 2050), however, we showed that this increase would only reduce the annual concentration of PM2.5 and PM10 by 1–2%. Therefore, about 90% of the concentration reduction would still rely on the traditional emission reduction measures. More other ecological functions of forests should be considered in afforestation plan.

Climate and air pollution alter incidence of tuberculosis in Beijing, China

PurposeThis study evaluated the possible association between climate and environment and the incidence of tuberculosis and determined the characteristics of tuberculosis in different climatic and air pollution conditions. MethodsData on tuberculosis incidence, climate (i.e., precipitation, atmospheric pressure, relative humidity, temperature, and wind speed), and air quality (inhalable particulate matter, sulfur dioxide, and nitrogen dioxide concentrations) in Beijing from 2004 to 2016 were collected and systematically analyzed based on a structural equation model. ResultsThe tuberculosis incidence was negatively correlated with the concentration of inhalable particulate matter, sulfur dioxide, or nitrogen dioxide. Precipitation, atmospheric pressure, and relative humidity had negative effects on tuberculosis incidence by indirectly lowering the concentrations of inhalable particulate matter and sulfur dioxide. By contrast, wind speed had a significant positive correlation with the incidence of tuberculosis. Temperature and wind speed had positive effects on tuberculosis incidence by improving the concentrations of inhalable particulate matter and sulfur dioxide. ConclusionsClimate and air quality are potential regulators of the incidence of tuberculosis. The improved air quality contributes to the decline of incidence of tuberculosis in Beijing. The impact of climatic indicators on the incidence of tuberculosis was mainly regulated by the environment. Further studies are needed to formulate preventive and regulatory strategies for tuberculosis based on different climatic and air quality conditions.

Distribution of particulate matter and ammonia and physicochemical properties of fine particulate matter in a layer house

High concentrations of particulate matter (PM) and ammonia (NH3) in poultry houses have adverse effects on the health of workers and animals. The present study investigated the distribution of the PM in different size fractions and NH3, as well as analyzing the physicochemical properties of fine particulate matter (PM2.5) in an enclosed layer house. The detection was taken from 5:00 to 21:00 in every 2 h for a 7-d continuous monitoring using a DustTrak II model 8532 aerosol monitor for PM concentrations and a JK40-IV portable gas detector for NH3 concentrations. The concentrations of inhalable particulate matter (PM10), total suspended particles (TSP), and NH3 were significantly higher in the rear of the chicken house compared to the front (P < 0.05). The PM10, TSP, and NH3 concentrations inside the layer house were significantly higher than outside (P < 0.001). The concentrations of PM10 and TSP were both highest at the first feeding time at 7:00. The PM2.5/PM10, PM2.5/TSP, and PM10/TSP concentration ratios at 5:00 were highest with 0.84, 0.62, and 0.74, respectively. Airflow speed showed a significant correlation with other measured microclimatic variables. Organic carbon was the primary constituent of PM2.5 collected from the layer house. It was also observed that mass percentage of elements C and O were both the highest by energy spectrum diagrams of PM2.5. The ultrastructure of PM2.5 revealed that there were mineral particles derived from feed, feces, or the ground and that smoke polymers came from ambient air. In conclusion, air quality was better at the front than at the middle and rear of the layer house. Air quality outside was better than that inside the house. Chicken activities primarily caused the PM10 and TSP concentrations to increase in the chicken house. The main components of PM2.5 in the layer house were organic matter and minerals, which were mostly derived from feed, feces, and ground dust.

Assessment of Inhalable Particulate Matter Associated with a Refinery in Cura&amp;amp;ccedil;ao

Inhalation and atmospheric pollution studies have focused on particulate matter due to correlations and associations with various morbidities and mortalities. This research analyzed ambient concentrations of inhalable particulate matter (PM10) on the island of Curaçao in order to evaluate through comparative literature analysis and recommended public health guidelines the potential health risks. Available hourly, daily and monthly PM10 measurements were accessed from June 2010 through December 2014 from a local air monitoring station in Willemstad. Mean annual concentrations of PM10 (31 - 122 μg/m3) in Curaçao are among the highest reported globally, demonstrating an increasing trend over time and exceed current public health guidelines recommended by local and international agencies. While the epidemiological evidence is inadequate to infer a causal association between health effects and long-term exposures of the measured PM10 concentrations, the results indicate that emissions controls are not adequate for compliance with international exposure standards.

Ambient air pollution and daily hospital admissions for mental disorders in Shanghai, China

Few studies have investigated the associations between ambient air pollution and mental disorders (MDs), especially in developing countries. We conducted a time-series study to explore the associations between six criteria air pollutants and daily hospital admissions for MDs in Shanghai, China, from 2013 to 2015. The MDs data were derived from the Shanghai Health Insurance System. We used over-dispersed, generalized additive models to estimate the associations after controlling for time trend, weather conditions, day of the week, and holidays. In addition, we evaluated the effect of modification by age, sex, and season. A total of 39,143 cases of hospital admissions for MDs were identified during the study period. A 10-μg/m3 increase in 2-day, moving-average concentration of inhalable particulate matter, sulfur dioxide (SO2), and carbon monoxide was significantly associated with increments of 1.27% [95% confidence interval (CI): 0.28%, 2.26%], 6.88% (95% CI, 2.75%, 11.00%), and 0.16% (95% CI: 0.02%, 0.30%) in daily hospital admissions for MDs, respectively. We observed positive but insignificant associations of fine particulate matter, nitrogen dioxide and ozone. The estimated association of SO2 was relatively robust to the adjustment of simultaneous exposure to other pollutants. We found generally stronger associations of air pollutants with MDs in warm seasons than in cool seasons. There were no significant differences in the associations between different sex and age groups. This study suggested that short-term exposure to air pollution, especially to sulfur dioxide, was associated with increased risk of hospital admissions for MDs in Shanghai, China.

Cage Versus Noncage Laying-Hen Housings: Respiratory Exposures

ABSTRACTThe objective of this study was to compare the personal respiratory exposures of poultry workers in three different types of layer housing under commercial production conditions. Workers were randomly assigned to each of conventional cage, enriched cage, and aviary barns in a crossover repeated-measures design for three observation periods over the hens’ lifetime. Inhalable and fine particulate matter (PM) and endotoxin in both size fractions were assessed by personal and area samplers over the work shift. Concentrations of inhalable PM, PM2.5 (PM with an aerodynamic diameter <2.5 μm), and endotoxin in both size fractions were higher in aviary than either the conventional or enriched barns. Geometric means (95% confidence intervals [CIs]) of inhalable PM and endotoxin for the aviary, conventional, and enriched barns were 8.9 (6.8–11.5) mg/m3 and 7517.9 (5403.2–10,460.2) EU/m3, 3.7 (2.8–4.8) mg/m3 and 1655.7 (1144.6–2395.2) EU/m3, 2.4 (1.8–3.3) mg/m3 and 1404.8 (983.3–2007.0) EU/m3, respectively. Area samplers recorded a lower mean inhalable PM concentration and higher PM2.5 concentration than personal samplers. Ammonia concentrations were low throughout three monitoring seasons. These findings show that the aviary barns pose higher respiratory exposures to poultry workers than either conventional or enriched barns.

Emissions of particulate matter from animal houses in the Netherlands

In the Netherlands, emissions from animal houses represent a major source of ambient particulate matter (PM). The objective of the present paper was to provide accurate and up to date concentrations and emission rates of PM10 and PM2.5 for commonly used animal housing systems, under representative inside and outside climate conditions and ventilation rates. We set up a national survey which covered 13 housing systems for poultry, pigs, and dairy cattle, and included 36 farms. In total, 202 24-h measurements were carried out, which included concentrations of inhalable PM, PM10, PM2.5, and CO2, ventilation rate, temperature, and relative humidity. On an animal basis, geometric mean emission rates of PM10 ranged from 2.2 to 12.0 mg h−1 in poultry and from 7.3 to 22.5 mg h−1 in pigs. The mean PM10 emission rate in dairy cattle was 8.5 mg h−1. Geometric mean emission rates of PM2.5 ranged from 0.11 to 2.41 mg h−1 in poultry and from 0.21 to 1.56 mg h−1 in pigs. The mean PM2.5 emission rate in dairy cattle was 1.65 mg h−1. Emissions are also reported per Livestock Unit and Heat Production Unit. PM emission rates increased exponentially with increasing age in broilers and turkeys and increased linearly with increasing age in weaners and fatteners. In laying hens, broiler breeders, sows, and dairy cattle, emission levels were variable throughout the year.

Human health risk assessment of airborne metals to a potentially exposed community: a screening exercise

Exposure to high concentrations of inhalable particulate matter (PM) is a known human health risk, depending on the chemical composition of the PM inhaled. Mogale City (Gauteng) is known for having several sources of airborne PM, however, less is known about the metals in the airborne PM. The aim of this study was to determine the metals in measured PM at Kagiso, Mogale City. An independent PM10 monitor was installed at the municipality’s existing monitoring site. This monitor continuously monitored PM10 between 23 August and 9 October 2013 and simultaneously sampled particles below 20 μm in diameter onto a glass fibre filter. This filter was replaced once towards the middle of the monitoring period. These two filters were chemically analysed to determine their metal content (30 metals) by the South African Bureau of Standards accredited laboratory at the Council for Scientific and Industrial Research by means of Inductively Coupled Plasma Spectroscopy (ICPS) based on the US EPA Method IO-3.1. To provide an estimate of possible health risk, the metal concentrations were used in a screening US-EPA human health risk assessment (HHRA). Since the analysed metals were reportedly below the detection limit, three hypothetical exposure scenarios (S) based on US-EPA recommendations were created for the HHRA. In S1, concentrations were considered to be the same as the detection limit for each metal; S2 assumed concentrations to be 50% of the detection limit; and S3 put concentrations at 10% of the detection limit. Potential risks (should pollution worsen) of developing respiratory and neurological effects were identified depending on the hypothetical scenarios. Continuous long-term monitoring and chemical characterisation are necessary to confirm these preliminary findings.

Inhalable desert dust, urban emissions, and potentially biotoxic metals in urban Saharan–Sahelian air

Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan–Sahelian country (Bamako, Mali) between September 2012 and July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 – 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory response, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara–Sahel region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure.

A Survey of Particulate Matter on California Dairy Farms

Over the past 30 yr, individual California dairy operations have grown in size; however, little is known about the distribution and determinants of particulate matter (PM) concentrations on these dairies. Elevated exposure to PM is associated with respiratory and cardiovascular health effects, particularly in occupational settings. The purpose of this study was to quantify the concentrations of PM and all inhalable PM (0-100 µm) on California dairies. Samplers were placed at various locations (e.g., milking parlor, grain storage area, drylot corral, and freestall barns) on 13 different dairies to collect PM and all inhalable PM during the 2008 summer months. The PM and all inhalable PM concentrations varied between different areas on a dairy and from dairy to dairy. Geometric mean concentrations for PM and inhalable PM were 24 µg m (range, 2-116 µg m) and 332 μg m (range, 74-1690 µg m). A key variable for explaining variation in PM concentrations with a mixed effects model was regional background ambient concentrations of PM No significant differences were observed in mean concentrations between upwind and downwind fence line concentrations (adjusted geometric mean ratio [AGMR] = 0.7; 95% CI, 0.4-1.3), although significant differences were found between upwind and central location mean values (AGMR = 0.5; 95% CI, 0.3-0.8; < 0.01). These results indicate dairy PM sources and, thus, elevated occupational exposure. Covariates, such as the age of the dairy and number of cows in the freestall barn and drylot corral, were important variables in explaining PM concentration variability. Levels of PM were lower compared with dairies in other U.S. states and other countries.

Time-series Analysis of Association Between Gaseous Air Pollutants and Daily Mortality in Urban Residents in Tianjin

PP-30-034 Background/Aims: Numerous epidemiological studies have reported the association between ambient pollutants in North American, European, and Asian cities. However, few studies explored the effects of air pollutants on daily mortality in Tianjin city. The aim is to study the association between sulfur dioxide and nitrogen dioxide and daily mortality in urban population in Tianjin. Methods: We collected daily concentration of inhalable particulate matter, sulfur dioxide and nitrogen dioxide, daily mean temperature and relative humidity, and daily cause-specific death counts. We used generalized additive models to explore the relationship between sulfur dioxide and nitrogen dioxide and daily mortality, after adjusting the effects of long-term and seasonal trend, and weather conditions, and analyzed the potential effect of particulate matter and model parameters on relative risk estimates. Results: Daily concentrations of SO2 and NO2 were significantly associated with daily nonaccidental and cardiovascular mortality, and not associated with daily respiratory mortality. An increase of 10 μg/m3 in SO2 was associated with 0.56% (95% CI: 0.23%–0.89%) nonaccidental morality and 0.49% (0.06%–0.93%) cardiovascular morality. An increase of 10 μg/m3 in NO2 was associated with 0.94% (95% CI: 0.17%–1.70%) nonaccidental morality and 1.29% (0.29%–2.30%) cardiovascular morality. Conclusion: The findings suggest that exposure to SO2 and NO2 was significantly associated with daily cardiovascular and respiratory mortality in urban population in Tianjin.

Atmospheric pollution and the prevalence of asthma: study among schoolchildren of 2 areas in Rio de Janeiro, Brazil

Air pollutants have been associated with the exacerbation of respiratory diseases. They may intensify the inflammatory allergic response and airways reactivity to inhaled allergens. However, it is still not clear if air pollution contributes to the increased prevalence of asthma. To investigate if different levels of air pollution exposure can be related to differences in the prevalence of asthma. The International Study of Asthma and Allergies in Childhood (ISAAC) protocol was used to determine and compare the prevalence of asthma among schoolchildren in 2 cities of the metropolitan region of Rio de Janeiro, Brazil, Duque de Caxias (DC) and Seropédica (SR), which have different levels of atmospheric pollution. The research involved 4,064 students aged 13 to 14 years from 49 schools in DC and 1,129 from 17 schools in SR. Air pollution was evaluated by the concentration of inhalable particulate matter (PM10). ISAAC's written questionnaire was answered by 4,040 students aged 13 to 14 years in DC and 1,080 in SR. Between 1998 and 2000, the PM10 annual arithmetic mean was 124 microg/m3 in DC and 35 microg/m3 in SR (acceptable level is up to 50 microg/m3). The prevalence of wheezing ever was 35.1% in DC and 29.9% in SR (P = .001), and the prevalence of wheezing in the last 12 months was 19.0% in DC and 15.0% in SR (P = .002). In DC, 14.5% of the adolescents presented 1 to 3 crises of wheezing in the last year, whereas in SR only 11.0% presented 1 to 3 crises (P = .003). In this study, the prevalence of asthma in adolescents was directly related to atmospheric pollution.

Ambient Air Quality and Occurrence of Multiple Sclerosis Relapse

Infectious viruses and bacteria can trigger multiple sclerosis (MS) exacerbations. Seasonally changing concentrations of ambient air pollutants are known to predispose to transmissible infections, to induce systemic immune responses and to enhance existing peripheral inflammation. Ambient air quality and monthly MS relapse occurrence in south-western Finland were compared by multivariate logistic regression. The odds ratio of the risk of a relapse onset was over fourfold (4.143, p < 0.001) when the concentration of inhalable particulate matter (PM₁₀) was at the highest quartile. Inhalable airborne particulate matter concentrations were connected to relapse occurrence. Poor air quality may enhance the seasonal changes in MS relapse occurrence by an increased susceptibility to transmissible infections.

The influence of local and regional sources on the concentration of inhalable particulate matter in southeastern Michigan

During June, July and August 1981, General Motors Research Laboratories collected daily fine (FPM = diameter < 2.5 μm) and coarse (CPM = ⩾ 2.5 μm, ⩽ 15 μm) particulate samples at four sites in southeastern Michigan. Dichotomous air samplers were located at a downtown Detroit site (DSC), a heavily industrialized site in Dearborn (RR), a suburban downwind site in Warren (TC), and an upwind site in Ann Arbor (AA) which behaved like a rural site. Analyses of the spatial variations of the various particulate components revealed the following results. (1) At all four sites the FPM was dominated by regional influences rather than local sources. The site in the industrial sector, RR, had the largest impact of local sources, but even at this site the local influences appeared to be smaller than the regional ones. (2) The regional influences were most pronounced on the sulfate (SO 2− 4) levels which accounted for the largest fraction (40–50 %) of the FPM. Evidence suggests that much of the observed SO 2− 4 was transported into the southeastern Michigan study area and was formed primarily via photochemically initiated reactions. (3) Organic carbon (OC) compounds were the second most abundant FPM species accounting for 20–40 % of the mass. OC seems to be controlled by both local and regional organic carbon influences. Vehicular emissions and possibly secondary reactions appear to affect the OC concentrations at the four sites. (4) Elemental carbon (EC), a relatively minor FPM species, appears to be dominated at DSC, RR and TC by local emissions. The EC levels at AA appear to be representative of the regional background as they were similar to the levels observed in rural areas far removed from local sources. (5) The CPM was dominated by local sources. At RR, however, the crustal-like material could only account for 18% of the CPM. This indicates that other local, noncrustal sources dominated the CPM levels at RR.