PM2.5 and mortality in long-term prospective cohort studies: cause-effect or statistical associations?

Concentrations of ambient PM2.5 (particulate matter <2.5 microm in aerodynamic diameter) were associated with increased mortality in two prospective cohort studies. In this paper, I assess whether the weight of the evidence supports a causal association. I assumed the study population in each city to have the same exposure; therefore, these are ecologic studies because exposure is at the group level. Health outcome and confounding data are at the individual level. Ambient PM concentrations are inadequate surrogates for personal exposure because they are at the group level and comprise only a small proportion of personal exposure, they change over time, and they constitute only a small proportion of a life span. The strength of association and exposure-response relationships cannot be determined because the ecologic group-level risks of PM2.5 are overestimated 150- to 300-fold based on an analogy with individual-level exposure to inhaled cigarette smoke. Risk estimates may also be high because of confounding from factors such as physical activity and lung function. The evidence is not coherent because the stronger associations are expected to be with morbidity, but instead are with mortality. For example, PM2.5 was associated with mortality but not with measurable reductions in lung function. Biological plausibility is lacking because lifetime exposure of rats to combustion products at concentrations two to three orders of magnitude higher than air pollution levels cause lung overloading but no consistent reduction in survival. Criteria for quantitative risk assessment are not met so the data are not useful for setting air quality standards. The weight of evidence suggests there is no substantive basis for concluding that a cause-effect relationship exists between long-term ambient PM2.5 and increased mortality.     

Detection of transmembrane helical segments at the nucleotide level in eukaryotic membrane protein genes

This article presents a review on the association between certain lifestyle characteristics and the risk for lung cancer in humans, using information derived primarily from epidemiological studies. Emphasis will be placed on more recently identified risk factors such as exposure to indoor air pollutants, psychosocial and behavioral influences, diet preferences, and fat intake. More traditional lifestyle factors such as cigarette smoking, occupation, and exposure to outdoor air pollutants will not be reviewed since their association with an increased risk for human lung cancer has been relatively well characterized and extensively reported. Evidence to date suggests that the indoor environment, life's events, and food choices may play a potentially important, albeit varying, role in the etiology of human lung cancer.     

Effect of measurement error on epidemiological studies of environmental and occupational exposures

Random error (misclassification) in exposure measurements usually biases a relative risk, regression coefficient, or other effect measure towards the null value (no association). The most important exception is Berkson type error, which causes little or no bias. Berkson type error arises, in particular, due to use of group average exposure in place of individual values. Random error in exposure measurements, Berkson or otherwise, reduces the power of a study, making it more likely that real associations are not detected. Random error in confounding variables compromises the control of their effect, leaving residual confounding. Random error in a variable that modifies the effect of exposure on health--for example, an indicator of susceptibility--tends to diminish the observed modification of effect, but error in the exposure can create a supurious appearance of modification. Methods are available to correct for bias (but not generally power loss) due to measurement error, if information on the magnitude and type of error is available. These methods can be complicated to use, however, and should be used cautiously as "correction" can magnify confounding if it is present.     

Effects of air quality on chronic respiratory symptoms adjusted for allergy among preadolescent children

The aim of this study was to assess the respiratory effects of outdoor air pollution after correcting for allergy and indoor air quality. The respiratory health survey targeted 1,129 schoolchildren, 9 yrs of age, attending schools in Krakow located in city areas differing in outdoor air pollution levels. Chronic phlegm as a unique symptom was related neither to allergy nor to indoor variables, but was associated with the outdoor air pollution level (odds ratio (OR): 4.2; 95% confidence interval (CI): 1.1-16.9). The same relationship has been confirmed for the self-reported local sources of industrial air pollution in the area of residence (OR: 4.2; 95% CI: 1.5-11.7). Hay fever appeared to be related to outdoor air pollution level (OR: 1.43; 95% CI: 1.1-2.0) and self-reported heavy traffic (OR: 1.3; 95% CI: 1.0-1.7). In the total sample, wheezing was connected exclusively to allergy and parental atopy, while attacks of dyspnoea with wheezing and asthma diagnosed by physician only were associated with allergy. Since the effect of outdoor pollutants on chronic cough and wheezing (odds ratio: 1.85; 95% confidence interval: 1.03-3.33) was only shown to be significant in the subsample of children without allergy and parental atopy, it may be postulated that either allergy is predisposing to respiratory reactions, or outdoor air pollution is coinvolved in an allergization process of the preadolescent children. Consequently, allergy should be considered as an important confound in epidemiological studies on the respiratory effects of air pollution.     

Long-term inhalable particles and other air pollutants related to mortality in nonsmokers

Long-term ambient concentrations of inhalable particles less than 10 microm in diameter (PM10) (1973- 1992) and other air pollutants-total suspended sulfates, sulfur dioxide, ozone (O3), and nitrogen dioxide-were related to 1977-1992 mortality in a cohort of 6,338 nonsmoking California Seventh-day Adventists. In both sexes, PM10 showed a strong association with mortality for any mention of nonmalignant respiratory disease on the death certificate, adjusting for a wide range of potentially confounding factors, including occupational and indoor sources of air pollutants. The adjusted relative risk (RR) for this cause of death as associated with an interquartile range (IQR) difference of 43 d/yr when PM10 exceeded 100 microg/m3 was 1.18 (95% confidence interval [CI]: 1.02, 1.36). In males, PM10 showed a strong association with lung cancer deaths-RR for an IQR was 2.38 (95% CI: 1.42, 3.97). Ozone showed an even stronger association with lung cancer mortality for males with an RR of 4.19 (95% CI: 1.81, 9.69) for the IQR difference of 551 h/yr when O3 exceeded 100 parts per billion. Sulfur dioxide showed strong associations with lung cancer mortality for both sexes. Other pollutants showed weak or no association with mortality.     

Personal sampling of particles in adults: relation among personal, indoor, and outdoor air concentrations

To investigate the validity of outdoor particulate matter with a 50% cutoff diameter of 10-microm (PM10) concentrations as a measure of exposure in time series studies, the association between personal and outdoor concentrations, within subjects, over time was investigated. Repeated measurements of personal, indoor, and outdoor PM10 were conducted among 37 nonsmoking, 50- to 70-year-old adults, living in Amsterdam, Netherlands, 1994. Regression analyses were conducted for each subject separately, and the distribution of the individual regression and correlation coefficients was investigated. Furthermore, the extent to which differences among personal, indoor, and outdoor concentrations could be explained was studied. The median Pearson's R between personal and outdoor concentrations was 0.50. Excluding days with exposure to environmental tobacco smoke (ETS) improved the correlation to a median R of 0.71. The estimated cross-sectional correlations were lower, 0.34 and 0.50, respectively. Outdoor concentrations (mean, 42 microg/m3) exceeded indoor concentrations (mean, 35 microg/m3) but underestimated personal exposures (mean, 62 microg/m3). The major part of the difference between personal and outdoor concentrations could be attributed to exposure to ETS, living along a busy road, and time spent in a vehicle. The results show a reasonably high correlation between personal and outdoor PM10 within individuals, providing support for the use of ambient PM10 concentrations as a measure of exposure in epidemiologic studies linking the day-to-day variation in particulate matter air pollution to the day-to-day variation in health endpoints such as mortality, hospital admissions, respiratory symptoms, and lung function.     

空调循环水处理的分析与建议

空调循环冷却水很容易受到外界的污染,使循环冷却系统结垢、腐蚀以及微生物大量繁殖,以致寿命减少。本文研究采用软化法并结合排污,投加阻垢分散剂等方法除垢;用药剂法、表面涂耐腐蚀层等方法来防腐;用增设旁流水等方法来去除微生物。处理后冷却水水质良好。     

掘进巷道火灾时期压风自救系统的作用规律

基于建立的掘进巷道和压风自救系统三维数值模型,研究了掘进巷道火灾时期压风自救系统对巷道环境的作用规律,重点分析了不同火灾位置、压风口位置对掘进巷道内风流状态、烟气分布及安全区域的影响。结果表明：当压风口处于火灾上风流而受到烟流滚退影响时,压风口射流较大幅度降低巷道内烟气浓度;火灾位于巷道前部时,安全区域主要分布于火灾下风流;火灾位于巷道后部时,安全区域主要分布于火灾上风流;风筒与压风口同侧时,火灾位置并非影响压风口附近区域风流分布和烟气分布的关键因素,而压风口位置是影响巷道风流分布和烟气分布的关键因素;当风筒与压风口布置在异侧时,压风口附近安全区域所占体积较大,更利于人员避难。     

Cytogenetic biomonitoring in traffic police workers: micronucleus test in peripheral blood lymphocytes

Atmospheric pollution represents a relevant environmental hazard which has been associated with considerable excess mortality, morbidity, and increased rates of respiratory diseases in humans. To date, more than 3,000 environmental chemical compounds have been identified in the ambient atmosphere, including a variety of mutagenic and/or carcinogenic agents, such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and heterocyclic compounds. Positive associations between cytogenetic markers and airborne levels of PAHs have been reported by experimental and human studies. Traffic has been implicated as the major determinant for the concentration of PAHs and, therefore, for the genotoxic activity of urban air. A biomonitoring study has been conducted in 82 italian traffic police workers exposed to air pollutants and 34 control subjects (matched by age, gender, and smoking habits) not exposed to traffic pollutants. The aim of this study was to assess the cytogenetic effects, such as micronucleus frequency in peripheral blood lymphocytes, and to estimate the association with individual exposure to PAH. Statistical analysis of the frequency of micronuclei in binucleated cells showed higher mean levels in referent subjects (4.03%) than in traffic police officers (3.73%). Smoking showed no effect on the frequency of micronuclei. The study failed to detect any association between micronucleus frequency and individual level of benzo(a)pyrene, considered a marker of exposure to PAHs. These findings indicate that exposure to urban air pollutants does not result in increased levels of micronuclei in peripheral white blood cells.     

Biliary tract complications in laparoscopic cholecystectomy. A multicenter study of 148 biliary tract injuries in 26,440 operations

BACKGROUND: Several ecologic analyses have shown significant positive associations between mean indoor radon concentrations and risk of leukemia at all ages (acute myeloid leukemia and chronic lymphocytic leukemia) and for children (all leukemia, acute myeloid leukemia, and acute lymphoblastic leukemia [ALL]). As part of an age-matched, case-control study of childhood ALL in the United States, we investigated the association between the incidence of ALL in children under age 15 years and indoor radon exposure. METHODS: Radon detectors were placed in current and previous homes of subjects where they resided for 6 months or longer. Children were included in analyses if radon measurements covered 70% or more of the 5-year period prior to diagnosis for case subjects (or from birth for case subjects under age 5 years) and the corresponding reference dates for control subjects. Radon levels could be estimated for 97% of the exposure period for the eligible 505 case subjects and 443 control subjects. RESULTS: Mean radon concentration was lower for case subjects (65.4 becquerels per cubic meter [Bqm(-3)]) than for control subjects (79.1 Bqm(-3)). For categories less than 37, 37-73, 74-147, and 148 or more Bqm(-3) of radon exposure, relative risks based on matched case-control pairs were 1.00, 1.22, 0.82, and 1.02, respectively, and were similar to results from an unmatched analysis. There was no association between ALL and radon exposure within subgroups defined by categories of age, income, birth order, birth weight, sex, type of residence, magnetic field exposure, parental age at the subject's birth, parental occupation, or parental smoking habits. CONCLUSIONS: In contrast to prior ecologic studies, the results from this analytic study provide no evidence for an association between indoor radon exposure and childhood ALL.     

Nutrient utilization by sheep and performance and carcass characteristics of steers fed crab waste-straw silage

Exacerbations of asthma have been associated with exposure to ozone or particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10). We postulated in this study that the association of summertime air pollution (i.e. ozone and PM10) with acute respiratory symptoms, medication use and peak expiratory flow differs among patients grouped according to asthma severity. During the summer of 1995, effects of ambient air pollution on these parameters were studied in a panel of 60 nonsmoking patients with intermittent to severe persistent asthma. These patients were recruited from our Pulmonary Out-patient Clinic. Subgroup analysis was performed on the degree of hyperresponsiveness and lung steroid use before the start of the study, as indictors for the severity of asthma. Associations of the parameters studied with ozone, PM10, nitrogen dioxide (NO2), sulphur dioxide (SO2) and black smoke were evaluated using time series analysis. Several episodes with increased summertime air pollution occurred during the 96 day study period. Eight hour average ozone concentrations exceeded the World Health Organization (WHO) Air Quality Guidelines (120 microg x m(-3)) on 16 occasions. Daily mean levels of PM10 were moderately elevated (range 16-98 microg x m(-3)). Levels of the other measured pollutants were low. There was a consistent, positive association of the prevalence of shortness of breath (maximal relative risk (RRmax) 1.18) with ozone, PM10, black smoke and NO2. In addition, bronchodilator use was associated with both ozone and PM10 levels (RRmax 1.16). Stratification by airway hyperresponsiveness and steroid use did not affect the magnitude of the observed associations. No associations with peak expiratory flow measurements were found. We conclude that the severity of asthma is not an indicator for the sensitivity to air pollution.     

An association between air pollution and mortality in six U.S. cities

BACKGROUND: Recent studies have reported associations between particulate air pollution and daily mortality rates. Population-based, cross-sectional studies of metropolitan areas in the United States have also found associations between particulate air pollution and annual mortality rates, but these studies have been criticized, in part because they did not directly control for cigarette smoking and other health risks. METHODS: In this prospective cohort study, we estimated the effects of air pollution on mortality, while controlling for individual risk factors. Survival analysis, including Cox proportional-hazards regression modeling, was conducted with data from a 14-to-16-year mortality follow-up of 8111 adults in six U.S. cities. RESULTS: Mortality rates were most strongly associated with cigarette smoking. After adjusting for smoking and other risk factors, we observed statistically significant and robust associations between air pollution and mortality. The adjusted mortality-rate ratio for the most polluted of the cities as compared with the least polluted was 1.26 (95 percent confidence interval, 1.08 to 1.47). Air pollution was positively associated with death from lung cancer and cardiopulmonary disease but not with death from other causes considered together. Mortality was most strongly associated with air pollution with fine particulates, including sulfates. CONCLUSIONS: Although the effects of other, unmeasured risk factors cannot be excluded with certainty, these results suggest that fine-particulate air pollution, or a more complex pollution mixture associated with fine particulate matter, contributes to excess mortality in certain U.S. cities.     

Assessment of ecologic regression in the study of lung cancer and indoor radon

Ecologic regression studies conducted to assess the cancer risk of indoor radon to the general population are subject to methodological limitations, and they have given seemingly contradictory results. The authors use simulations to examine the effects of two major methodological problems that affect these studies: measurement error and misspecification of the risk model. In a simulation study of the effect of measurement error caused by the sampling process used to estimate radon exposure for a geographic unit, both the effect of radon and the standard error of the effect estimate were underestimated, with greater bias for smaller sample sizes. In another simulation study, which addressed the consequences of uncontrolled confounding by cigarette smoking, even small negative correlations between county geometric mean annual radon exposure and the proportion of smokers resulted in negative average estimates of the radon effect. A third study considered consequences of using simple linear ecologic models when the true underlying model relation between lung cancer and radon exposure is nonlinear. These examples quantify potential biases and demonstrate the limitations of estimating risks from ecologic studies of lung cancer and indoor radon.     

The broken Kirschner wire as a complication of transarticular fixation of the neck of the radius in children (author''s transl)

A portable personal air pollution sampler was used to measure the exposure of twenty children to respirable particulates, sulfur dioxide, and nitrogen dioxide over a 24-hour period. Particulate exposures were significantly higher among children who lived with one or more smokers, and exceeded the primary air quality standard in nineteen of the twenty subjects. To a large extent, an individual's respirable particulate load appears to be determined by exposure to indoor rather than outdoor pollutants.     

建筑环境中有机磷酸酯污染特征和控制技术研究进展

有机磷酸酯（Organophosphate esters, OPEs）作为一类阻燃剂和增塑剂,在建筑材料和室内装修材料中广泛使用。由于该类物质主要以物理添加而非化学键合的方式加入到材料中,因此易在使用过程中进入环境。研究表明OPEs普遍存在于室内环境中,并且浓度较高,人体长期暴露在高浓度OPEs的室内环境中,可能存在一定的健康风险。本文在综述了常见OPEs的性质、应用和生物毒性的基础上,总结了其在建筑环境中的污染特征、环境行为和暴露水平,介绍了建筑环境中OPEs的源汇特性、控制技术与人体暴露风险,并对未来研究方向进行了展望。      

Risk in cleaning: chemical and physical exposure

Cleaning is a large enterprise involving a large fraction of the workforce worldwide. A broad spectrum of cleaning agents has been developed to facilitate dust and dirt removal, for disinfection and surface maintenance. The cleaning agents are used in large quantities throughout the world. Although a complex pattern of exposure to cleaning agents and resulting health problems, such as allergies and asthma, are reported among cleaners, only a few surveys of this type of product have been performed. This paper gives a broad introduction to cleaning agents and the impact of cleaning on cleaners, occupants of indoor environments, and the quality of cleaning. Cleaning agents are usually grouped into different product categories according to their technical functions and the purpose of their use (e.g. disinfectants and surface care products). The paper also indicates the adverse health and comfort effects associated with the use of these agents in connection with the cleaning process. The paper identifies disinfectants as the most hazardous group of cleaning agents. Cleaning agents contain evaporative and non-evaporative substances. The major toxicologically significant constituents of the former are volatile organic compounds (VOCs), defined as substances with boiling points in the range of 0 degree C to about 400 degrees C. Although laboratory emission testing has shown many VOCs with quite different time-concentration profiles, few field studies have been carried out measuring the exposure of cleaners. However, both field studies and emission testing indicate that the use of cleaning agents results in a temporal increase in the overall VOC level. This increase may occur during the cleaning process and thus it can enhance the probability of increased short-term exposure of the cleaners. However, the increased levels can also be present after the cleaning and result in an overall increased VOC level that can possibly affect the indoor air quality (IAQ) perceived by occupants. The variety and duration of the emissions depend inter alia on the use of fragrances and high boiling VOCs. Some building materials appear to increase their VOC emission through wet cleaning and thus may affect the IAQ. Particles and dirt contain a great variety of both volatile and non-volatile substances, including allergens. While the volatile fraction can consist of more than 200 different VOCs including formaldehyde, the non-volatile fraction can contain considerable amounts (> 0.5%) of fatty acid salts and tensides (e.g. linear alkyl benzene sulphonates). The level of these substances can be high immediately after the cleaning process, but few studies have been conducted concerning this problem. The substances partly originate from the use of cleaning agents. Both types are suspected to be airway irritants. Cleaning activities generate dust, mostly by resuspension, but other occupant activities may also resuspend dust over longer periods of time. Personal sampling of VOCs and airborne dust gives higher results than stationary sampling. International bodies have proposed air sampling strategies. A variety of field sampling techniques for VOC and surface particle sampling is listed.     

Urban air pollution and emergency admissions for asthma in four European cities: the APHEA Project

BACKGROUND: A study was undertaken to assess the combined association between urban air pollution and emergency admissions for asthma during the years 1986-92 in Barcelona, Helsinki, Paris and London. METHODS: Daily counts were made of asthma admissions and visits to the emergency room in adults (age range 15-64 years) and children (< 15 years). Covariates were short term fluctuations in temperature and humidity, viral epidemics, day of the week effects, and seasonal and secular trends. Estimates from all the cities were obtained for the entire period and separately by warm or cold seasons using Poisson time-series regression models. Combined associations were estimated using meta-analysis techniques. RESULTS: Daily admissions for asthma in adults increased significantly with increasing ambient levels of nitrogen dioxide (NO2) (relative risk (RR) per 50 micrograms/m3 increase 1.029, 95% CI 1.003 to 1.055) and non-significantly with particles measured as black smoke (RR 1.021, 95% CI 0.985 to 1.059). The association between asthma admissions and ozone (O3) was heterogeneous among cities. In children, daily admissions increased significantly with sulphur dioxide (SO2) (RR 1.075, 95% CI 1.026 to 1.126) and non-significantly with black smoke (RR 1.030, 95% CI 0.979 to 1.084) and NO2, though the latter only in cold seasons (RR 1.080, 95% CI 1.025 to 1.140). No association was observed for O3. The associations between asthma admissions and NO2 in adults and SO2 in children were independent of black smoke. CONCLUSIONS: The evidence of an association between air pollution at current urban levels and emergency room visits for asthma has been extended to Europe. In addition to particles, NO2 and SO2--by themselves or as a constituent of a pollution mixture--may be important in asthma exacerbations in European cities.