Ambient particulate matter and health effects: publication bias in studies of short-term associations

BACKGROUND: Time-series studies have shown short-term temporal associations between low levels of ambient particulate air pollution and adverse health effects. It is not known whether or to what extent this literature is affected by publication bias. METHODS: We obtained effect estimates from time-series studies published up to January 2002. These were summarized and examined for funnel plot asymmetry. We compared summary estimates between single-city and prospective multicity studies. Using 1 multicity study, we examined the sensitivity of summary estimates to alternative lag selection policies. RESULTS: We found evidence for publication bias among single-city studies of daily mortality, hospital admissions for chronic obstructive lung disease (COPD), and incidence of cough symptom, but not for studies of lung function. Statistical correction for this bias reduced summary relative risk estimates for a 10 microg/m increment of particulate matter less than 10 microm aerodynamic diameter (PM10) as follows: daily mortality from 1.006 to 1.005 and admissions for COPD from 1.013 to 1.011; and odds ratio for cough from 1.025 to 1.015. Analysis of results from a large multicity study suggested that selection of positive estimates from a range of lags could increase summary estimates for PM10 and daily mortality by up to 130% above those based on nondirectional approaches. CONCLUSION: We conclude that publication bias is present in single-city time-series studies of ambient particles. However, after correcting for publication bias statistically, associations between particles and adverse health effects remained positive and precisely estimated. Differential selection of positive lags may also inflate estimates.     

Multipollutant exposures and health responses to particulate matter.

Epidemiological methods provide opportunities to study interactions of pollutants in complex environments. During the study of health and the environment and the evaluation of particulate matter in Tucson, we found that type, location, and temporality of particulate matter exposures were critical with respect to the various interactions that related to health effects. Indoor particulate matter interacted with other components of particulate matter found in tobacco smoke, as evidenced by lung function. The interaction of environmental tobacco smoke with indoor formaldehyde caused various symptoms. Other interactions occurred between indoor and outdoor forms of particulate matter, which caused symptoms in some of the subjects.     

Estimation of personal exposures to particulate matter and metals in boiler overhaul work

OBJECTIVE: We sought to develop an algorithm and estimate unmeasured exposures to particulate matter (PM) and metals in an epidemiologic study of boilermakers. METHODS: The algorithm was based on limited measurements and workers' task and time activity patterns. Half of the measurements were used to develop exposure estimates for unmeasured person days. The other half was used for method validation. RESULTS: The validation demonstrated good approximations of actual exposures with differences less than 5% for PM and vanadium (V). Average estimated exposures to PM (mg/m3) and V (microg/m3) were significantly higher for workers doing boiler repair than utility work (0.36 vs. 0.09 for PM and 5.99 vs. 0.38 for V). CONCLUSIONS: This algorithm provided reasonably accurate exposure indices for our epidemiologic study in this population. It also is likely applicable to similar exposure scenarios in other studies.     

Characterization of fine particulate matter in Ohio: indoor, outdoor, and personal exposures

Ambient, indoor, and personal PM2.5 concentrations were assessed based on an exhaustive study of PM2.5 performed in Ohio from 1999 to 2000. Locations in Columbus, one in an urban corridor and the other in a suburban area were involved. A third rural location in Athens, Ohio, was also established. At all three locations, elementary schools were utilized to determine outdoor, indoor, and personal PM2.5 concentrations for fourth and fifth grade students using filter-based measurements. Three groups of 30 students each were used for personal sampling at each school. Continuous ambient PM2.5 mass concentrations were also measured with tapered element oscillating microbalances (TEOMs). At all three sites, personal and indoor PM2.5 concentrations exceeded outdoor levels. This trend is consistent on all week days and most evident in the spring as compared to fall and winter. The ambient PM2.5 concentrations were similar among the three sites, suggesting the existence of a common regional source influence. At all the three sites, larger variations were found in personal and indoor PM2.5 than ambient levels. The strongest correlations were found between indoor and personal concentrations, indicating that personal PM2.5 exposures were significantly affected by indoor PM2.5 than by ambient PM2.5. This was further confirmed by the indoor to outdoor (I/O) ratios of PM2.5 concentrations, which were greater when school was in session than non-school days when the students were absent.     

Factors affecting the association between ambient concentrations and personal exposures to particles and gases

Results from air pollution exposure assessment studies suggest that ambient fine particles [particulate matter with aerodynamic diameter相似文献   

Impact of personal and ambient-level exposures to nitrogen dioxide and particulate matter on cardiovascular function

This work explored the association between nitrogen dioxide (NO₂) and PM_2.5 components with changes in cardiovascular function in an adult non-smoking cohort. The cohort consisted of 65 volunteers participating in the US EPA's Detroit Exposure and Aerosol Research Study (DEARS) and a University of Michigan cardiovascular sub-study. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), brachial artery diameter (BAD), brachial artery flow-mediated dilatation (FMD) and nitroglycerin-mediated arterial dilatation (NMD) were collected by in-home examinations. A maximum of 336 daily environmental and health effect observations were obtained. Daily potassium air concentrations were associated with significant decreases in DBP (?0.0447 mmHg/ng/m³ ± 0.0132, p = 0.0016, lag day 0) among participants compliant with the personal monitoring protocol. Personal NO₂ exposures resulted in significant changes in BAD (e.g., 0.0041 mm/ppb ± 0.0019, p = 0.0353, lag day 1) and FMD (0.0612 ± 0.0235, p = 0.0103, lag day 0) among other findings.     

Monitoring of 1-min personal particulate matter exposures in relation to voice-recorded time-activity data.

Recent studies on the association between exposures to airborne particulate matter (PM) and disease have identified short-term peaks in PM exposures as posing especial health threats. Lightweight personal instruments are needed to characterize short-term exposures to PM and to identify the most important sources of high PM excursions. In this study, we measured exposure to fine PM using a small personal nephelometer (pDR; MIE, Inc) to investigate the utility of this instrument in identifying activities and microenvironments most associated with high PM exposures and the magnitude and duration of peaks in PM exposures. Ten adult volunteers wore a pDR recording PM concentrations at 1-min time intervals for 1 week each. PM concentrations were measured by the pDR in units of microg/m(3) based on light scatter. The use of a time-stamped voice recorder enabled activity and location to be continuously documented in real time. In addition, a small, inexpensive light intensity logger was affixed to the pDR to evaluate the potential of this instrument to assist in verifying wearer- recorded data. For each person, patterns of PM exposure were remarkably consistent over daily activities and showed large excursions associated with specific indoor and outdoor microenvironments and activities, such as cooking. When the magnitude and duration of excursions in PM were analyzed, we found that high PM levels occurred in relatively few of the minutes measured but comprised a substantial fraction of the total exposure to PM. Fifteen-minute averaged PM levels were found to be as much as 10 times the daily average. When the data were analyzed with a generalized estimating equation model to account for effects of autocorrelation and clustering, PM exposure was significantly higher during subject-reported events including barbeque, yard work, being near pets or construction activities, cooking, and environmental tobacco smoke exposure, as compared with periods with no pollution events. When light intensity data were explored to determine whether these loggers could be of potential use in establishing or verifying indoor vs outdoor location for future PM studies, we found that personal light intensity measurements differed among indoor, outdoor, and in-car environments (P<0.001). Overlap between measured values implies that light intensity cannot be used to absolutely predict location; however, a sudden increase or decrease in light intensity was highly associated with participant report of location change between indoors and outdoors. This study demonstrates the utility of the pDR in identifying patterns of personal exposures to particulate matter and especially in registering the magnitude and duration of excursions in PM in relation to location and activity.     

Adverse cardiovascular effects with acute particulate matter and ozone exposures: interstrain variation in mice

OBJECTIVES: Increased ambient particulate matter (PM) levels are associated with cardiovascular morbidity and mortality, as shown by numerous epidemiology studies. Few studies have investigated the role of copollutants, such as ozone, in this association. Furthermore, the mechanisms by which PM affects cardiac function remain uncertain. We hypothesized that PM and O(3) induce adverse cardiovascular effects in mice and that these effects are strain dependent. STUDY DESIGN: After implanting radiotelemeters to measure heart rate (HR) and HR variability (HRV) parameters, we exposed C57Bl/6J (B6), C3H/HeJ (HeJ), and C3H/HeOuJ (OuJ) inbred mouse strains to three different daily exposures of filtered air (FA), carbon black particles (CB), or O(3) and CB sequentially [O(3)CB; for CB, 536 +/- 24 microg/m(3); for O(3), 584 +/- 35 ppb (mean +/- SE)]. RESULTS: We observed significant changes in HR and HRV in all strains due to O(3)CB exposure, but not due to sequential FA and CB exposure (FACB). The data suggest that primarily acute HR and HRV effects occur during O(3)CB exposure, especially in HeJ and OuJ mice. For example, HeJ and OuJ mice demonstrated dramatic increases in HRV parameters associated with marked brady-cardia during O(3)CB exposure. In contrast, depressed HR responses occurred in B6 mice without detectable changes in HRV parameters. CONCLUSIONS: These findings demonstrate that important interstrain differences exist with respect to PM- and O(3)-induced cardiac effects. This interstrain variation suggests that genetic factors may modulate HR regulation in response to and recuperation from acute copollutant exposures.     

Workgroup report: workshop on source apportionment of particulate matter health effects--intercomparison of results and implications

Although the association between exposure to ambient fine particulate matter with aerodynamic diameter < 2.5 microm (PM2.5) and human mortality is well established, the most responsible particle types/sources are not yet certain. In May 2003, the U.S. Environmental Protection Agency's Particulate Matter Centers Program sponsored the Workshop on the Source Apportionment of PM Health Effects. The goal was to evaluate the consistency of the various source apportionment methods in assessing source contributions to daily PM2.5 mass-mortality associations. Seven research institutions, using varying methods, participated in the estimation of source apportionments of PM2.5 mass samples collected in Washington, DC, and Phoenix, Arizona, USA. Apportionments were evaluated for their respective associations with mortality using Poisson regressions, allowing a comparative assessment of the extent to which variations in the apportionments contributed to variability in the source-specific mortality results. The various research groups generally identified the same major source types, each with similar elemental makeups. Intergroup correlation analyses indicated that soil-, sulfate-, residual oil-, and salt-associated mass were most unambiguously identified by various methods, whereas vegetative burning and traffic were less consistent. Aggregate source-specific mortality relative risk (RR) estimate confidence intervals overlapped each other, but the sulfate-related PM2.5 component was most consistently significant across analyses in these cities. Analyses indicated that source types were a significant predictor of RR, whereas apportionment group differences were not. Variations in the source apportionments added only some 15% to the mortality regression uncertainties. These results provide supportive evidence that existing PM2.5 source apportionment methods can be used to derive reliable insights into the source components that contribute to PM2.5 health effects.     

PM_(2.5)个体暴露连续监测方法

目的整合滤膜称重法和光散射法测定PM_(2.5)优越性,建立更加准确的PM_(2.5)个体暴露连续监测方法。方法采用滤膜称重法和光散射法同时测定个体PM_(2.5)暴露浓度,以滤膜称重法与光散法测定结果的比值作为校正系数,修正光散射法测定值,获得PM_(2.5)个体暴露实时浓度。结果测定时间为3、10、30和60 min时方法检出限(LOD)分别4.6、4.0、3.9和3.7μg/m~3;对不同浓度环境空气平行测定的精密度(RSD)范围为2.1%~9.5%;与微量振荡天平法(TEOM)测定的实时浓度(30min时间加权平均浓度)间具有良好的相关关系,Pearson r=0.934(P0.001,n=233),配对t检验结果表明两种方法结果间差异无统计学意义(P=0.957);实验室连续24 h监测中,30%(3/10)的监测检测到零点漂移,漂移值范围为-5~-3μg/m~3;连续5 d的现场监测中,7.5%(31/412)的监测检测到零点漂移,其中大部分的漂移值在-3~3μg/m~3,零点漂移方向和大小不受环境PM_(2.5)浓度影响。结论该方法结合了光散射法及重量法的优点,可以获得较为准确的PM_(2.5)个体实时暴露浓度,能够满足PM_(2.5)个体暴露监测的要求。     

Semi-continuous speciation analyses for ambient air particulate matter: an urgent need for health effects studies

One of the most urgent needs for future progress in reducing the substantial impacts of ambient air particulate matter (PM) on human health is to determine which of its components are having the greatest effects. The EPA's Speciation Trends Network (STN) has been operating since 2000. It generates 24-h average fine PM component concentrations for sulfate and nitrate ions, elemental and organic carbon (EC/OC), and many elements on an every third or sixth day basis for one or a few sites in most large US cities. To date, a small number of research studies, summarized in this paper, have used available STN and other supplemental data to identify and quantify the influences of specific components or source-related mixtures on measures of health-related impacts. These pioneering studies have demonstrated the potential utility of using such data in analyses that can provide a sound basis for guiding future research and control activities on those PM sources that have the greatest public health relevance. Unfortunately, the STN data collection methods used are expensive, and data have therefore been too sparse for studies of short-term health effects, where semi-continuous data, or at least daily 24-h concentration data are needed, as well as for regional concentration distributions that are needed for definitive analyses. Furthermore, because of cost considerations, there is virtually no prospect of collecting the data needed by the health researchers for more definitive analyses as long as there is continued reliance on current FRM sampling and analysis methodologies. At the second EPA-HEI Workshop on "Air Quality and Health Researchers Working Together" in RTP, NC on 16 and 17 April 2008, many participants concluded that it was both desirable, and possibly technically and economically feasible, to re-equip the STN sites with an automated system of semi-continuous monitors for sulfate, nitrate, EC, OC, and semi-continuous multistage PM samplers for non-volatile elements, providing continuous records of PM components with an averaging time of approximately 6 h for both thoracic coarse mode PM, fine PM, and perhaps ultrafine PM as well. The availability of such data would greatly accelerate the accumulation of knowledge on PM component exposure-response relationships that would provide a sound basis more targeted air quality standards and pollution control measures.     

Measurement of area and personal breathing zone concentrations of diesel particulate matter (DPM) during oil and gas extraction operations,including hydraulic fracturing

Diesel engines serve many purposes in modern oil and gas extraction activities. Diesel particulate matter (DPM) emitted from diesel engines is a complex aerosol that may cause adverse health effects depending on exposure dose and duration. This study reports on personal breathing zone (PBZ) and area measurements for DPM (expressed as elemental carbon) during oil and gas extraction operations including drilling, completions (which includes hydraulic fracturing), and servicing work.

Researchers at the National Institute for Occupational Safety and Health (NIOSH) collected 104 full-shift air samples (49 PBZ and 55 area) in Colorado, North Dakota, Texas, and New Mexico during a four-year period from 2008–2012. The arithmetic mean (AM) of the full shift TWA PBZ samples was 10 µg/m³; measurements ranged from 0.1–52 µg/m³. The geometric mean (GM) for the PBZ samples was 7 µg/m³. The AM of the TWA area measurements was 17 µg/m³ and ranged from 0.1–68 µg/m³. The GM for the area measurements was 9.5 µg/m³. Differences between the GMs of the PBZ samples and area samples were not statistically different (P > 0.05).

Neither the Occupational Safety and Health Administration (OSHA), NIOSH, nor the American Conference of Governmental Industrial Hygienists (ACGIH) have established occupational exposure limits (OEL) for DPM. However, the State of California, Department of Health Services lists a time-weighted average (TWA) OEL for DPM as elemental carbon (EC) exposure of 20 µg/m³. Five of 49 (10.2%) PBZ TWA measurements exceeded the 20 µg/m³ EC criterion. These measurements were collected on Sandmover and Transfer Belt (T-belt) Operators, Blender and Chemical Truck Operators, and Water Transfer Operators during hydraulic fracturing operations.

Recommendations to minimize DPM exposures include elimination (locating diesel-driven pumps away from well sites), substitution, (use of alternative fuels), engineering controls using advanced emission control technologies, administrative controls (configuration of well sites), hazard communication, and worker training.     

大气颗粒物对人体皮肤健康影响的研究进展

近年来我国大气污染问题日益严重,国内外大量研究表明,大气污染与许多健康效应直接或间接相关。已有流行病学研究证实,大气颗粒物污染与皮肤疾病的发病率密切相关。该文从氧化应激与炎症反应、芳香烃受体(Ah R)的活化、皮肤表面微生物的影响,就现有大气颗粒物对皮肤健康影响的流行病学及毒理学研究进行综述。     

Exposure to ambient and nonambient components of particulate matter: a comparison of health effects

BACKGROUND: Numerous epidemiologic studies report associations between outdoor concentrations of particles and adverse health effects. Because personal exposure to particles is frequently dominated by exposure to nonambient particles (those originating from indoor sources), we present an approach to evaluate the relative impacts of ambient and nonambient exposures. METHODS: We developed separate estimates of exposures to ambient and nonambient particles of different size ranges (PM2.5, PM10-2.5 and PM10) based on time-activity data and the use of particle sulfate measurements as a tracer for indoor infiltration of ambient particles. To illustrate the application of these estimates, associations between cardiopulmonary health outcomes and the estimated exposures were compared with associations computed using measurements of personal exposures and outdoor concentrations for a repeated-measures panel study of 16 patients with chronic obstructive pulmonary disease conducted in the summer of 1998 in Vancouver. RESULTS: Total personal fine particle exposures were dominated by exposures to nonambient particles, which were not correlated with ambient fine particle exposures or ambient concentrations. Although total and nonambient particle exposures were not associated with any of the health outcomes, ambient exposures (and to a lesser extent ambient concentrations) were associated with decreased lung function, decreased systolic blood pressure, increased heart rate, and increased supraventricular ectopic heartbeats. Measures of heart rate variability showed less consistent relationships among the various exposure metrics. CONCLUSIONS: These results demonstrate the usefulness of separating total personal particle exposures into their ambient and nonambient components. The results support previous epidemiologic findings using ambient concentrations by demonstrating an association between health outcomes and ambient (outdoor origin) particle exposures but not with nonambient (indoor origin) particle exposures.     

Invited commentary: heterogeneity of particulate matter health risks

Ambient particulate matter varies in composition and toxicity; therefore, some heterogeneity in risk per unit mass can be anticipated. In this issue of the Journal (Am J Epidemiol 2007;166:880-888), Dominici et al. explore temporal and spatial effect modification of particulate matter potency with the goal of gaining insights about how differences in the mixture may affect toxicity of the particulate matter, and they propose that it may be a useful tool in assessing the net impact of regulatory activity. Their approach is fresh and creative and yields provocative results. Such assessments will, of course, be constrained by limited power to detect the expected small degree of effect modification, as well as an abundance of possible explanations for observed differences in risk per unit mass. The utility for accountability assessment is further limited because regulatory actions impacting particulate matter levels do not necessarily target the most toxic species within the mixture and may confer benefits by reducing population exposure to particles and components of lesser toxicity. Used cautiously, however, this new methodology may provide a complementary approach to more direct assessments in shedding light on the characteristics of ambient particulate matter predictive of health effects.     

空气细颗粒物与呼吸系统的健康损害

空气细颗粒物(PM 2.5)是重要的环境空气污染物,主要来源于工业生产、汽车尾气和城市建设等人为活动.随着我国经济的高速发展,越来越严重的空气颗粒物污染可引起一系列健康危害,汇总国内外相关研究内容显示,长期接触高浓度的空气细颗粒可引起成人和儿童肺功能下降,增加慢性阻塞性肺病的发作,表现为慢阻肺的人院率和死亡率升高.人群流行病学研究提示空气细颗粒物可能增加儿童哮喘的发病和发作,并与成人哮喘急性发作有关.空气细颗粒导致慢阻肺和哮喘的机制仍不十分清楚,可能与颗粒物及组分造成的呼吸道氧化损伤、炎性反应、粘液大量分泌,以及直接对小气道壁的损伤有关,详细机制有待深入研究.