Air Pollution in Road Tunnels

As a part of a study of pollution of the air by motor vehicles, measurements have been made in two London road tunnels during periods of high traffic density. The concentrations of smoke and polycyclic hydrocarbons found there are much higher than the average values in Central London, but they are of the same order of magnitude as those occurring during temperature inversions on winter evenings when smoke from coal fires accumulates at a low level.

An attempt has been made to relate the concentration of each pollutant to the type and amount of traffic. Both diesel and petrol vehicles make some contribution to the amounts of smoke and polycyclic hydrocarbons found in the tunnels, but in the case of smoke, fluoranthene, 1: 2-benzpyrene, pyrene, and 3: 4-benzpyrene, the concentrations appear to be more closely related to the density of diesel traffic than to that of petrol traffic. The concentrations of lead and carbon monoxide have also been determined, and these are very closely related to the density of petrol traffic. During the morning and evening rush hours the mean concentration of carbon monoxide was just over 100 p.p.m. and peak values up to 500 p.p.m. were recorded at times. Oxides of nitrogen were determined in some of the experiments and there was always much more nitric oxide than nitrogen dioxide. Eye irritation was experienced but its cause was not investigated.

The concentration of pollution in the tunnels does not appear to be high enough to create any special hazards for short-term exposures. The amosphere at peak periods may become very dirty and unpleasant and the concentration of carbon monoxide would be sufficient to produce some effect over a period of several hours' continuous exposure. The total emission of pollution from road vehicles must still be small in comparison with that from coal fires, but the effect of traffic on the concentration of smoke, polycyclic hydrocarbons, carbon monoxide, and lead in the air of city streets deserves continued study.

     

Diesel engine exhaust and lung cancer: an unproven association.

The risk of lung cancer associated with diesel exhaust has been calculated from 14 case-control or cohort studies. We evaluated the findings from these studies to determine whether there is sufficient evidence to implicate diesel exhaust as a human lung carcinogen. Four studies found increased risks associated with long-term exposure, although two of the four studies were based on the same cohort of railroad workers. Six studies were inconclusive due to missing information on smoking habits, internal inconsistencies, or inadequate characterization of diesel exposure. Four studies found no statistically significant associations. It can be concluded that short-term exposure to diesel engine exhaust (< 20 years) does not have a causative role in human lung cancer. There is statistical but not causal evidence that long-term exposure to diesel exhaust (> 20 years) increases the risk of lung cancer for locomotive engineers, brakemen, and diesel engine mechanics. There is inconsistent evidence on the effects of long-term exposure to diesel exhaust in the trucking industry. There is no evidence for a joint effect of diesel exhaust and cigarette smoking on lung cancer risk. Using common criteria for determining causal associations, the epidemiologic evidence is insufficient to establish diesel engine exhaust as a human lung carcinogen.     

Allergic susceptibility associated with diesel exhaust particle exposure: clear as mud

Exposure to elevated levels of particulate air pollution from motor vehicles is frequently associated with increased morbidity and mortality from cardiovascular conditions, lung cancer, and nonmalignant respiratory illnesses (e.g., asthma, bronchitis, respiratory tract infections). It appears, however, that less attention has been paid to the potential role of road traffic fumes in the induction of allergic conditions. Laboratory studies in humans and animals have shown that particulate toxic pollutants-particularly diesel exhaust particulates-can enhance allergic inflammation and can induce allergic immune responses. Most of these immune responses are mediated by the carbon core of diesel exhaust particulates. Polyaromatic hydrocarbons (e.g., anthracene, fluoranthene, pyrene, phenanthrene) are major chemical components of diesel exhaust particulates, and they have enhanced the production of immunoglobulin E. Although several large epidemiological studies have demonstrated a strong association between exposure to motor vehicle traffic emissions and allergic symptoms and reduced lung function, the evidence for the development of allergic sensitization from diesel exhaust particulates is less abundant than for the aforementioned associations. Recent comparisons of the prevalence of hay fever, as well as positive skin-prick tests, between citizens of former West and East Germany and between Hong Kong and China civilians, have demonstrated marked differences. Crucial variations in the level of particulate air pollution from motor vehicles in these countries may account for the observed increased prevalence of atopy. Although road-traffic pollution from automobile exhausts may be a risk factor for atopic sensitization, the evidence in support of this view remains conflictive. Some investigators have reported a clear association between the prevalence of allergy and road-traffic-related air pollution, whereas such a difference was not observed in other studies. Most discrepancies have been related to important variations in study design and methodology. In addition, inasmuch as exposure to ambient particles differs substantially in worldwide urban environments, perhaps qualitative-rather than quantitative-variations in particulate air pollution at different locations account for differences in the prevalence and/or severity of respiratory allergies.     

Combustion of diesel fuel from a toxicological perspective

Summary Since the use of diesel engines is still increasing, the contribution of their incomplete combustion products to air pollution is becoming ever more important. The presence of irritating and genotoxic substances in both the gas phase and the particulate phase constituents is considered to have significant health implications. The quantity of soot particles and the particle-associated organics emitted from the tail pipe of a diesel-powered vehicle depend primarily on the engine type and combustion conditions but also on fuel properties. The quantity of soot particles in the emissions is determined by the balance between the rate of formation and subsequent oxidation. Organics are adsorbed onto carbon cores in the cylinder, in the exhaust system, in the atmosphere and even on the filter during sample collection. Diesel fuel contains polycyclic aromatic hydrocarbons (PAHs) and some alkyl derivatives. Both groups of compounds may survive the combustion process. PAHs are formed by the combustion of crankcase oil or may be resuspended from engine and/or exhaust deposits. The conversion of parent PAHs to oxygenated and nitrated PAHs in the combustion chamber or in the exhaust system is related to the vast amount of excess combustion air that is supplied to the engine and the high combustion temperature. Whether the occurrence of these derivatives is characteristic for the composition of diesel engine exhaust remains to be ascertained. After the emission of the particles, their properties may change because of atmospheric processes such as aging and resuspension. The particle-associated organics may also be subject to (photo)chemical conversions or the components may change during sampling and analysis. Measurement of emissions of incomplete combustion products as determined on a chassis dynamometer provides knowledge of the chemical composition of the particle-associated organics. This knowledge is useful as a basis for a toxicological evaluation of the health hazards of diesel engine emissions.     

Lung clearance of inhaled particles after exposure to carbon black generated from a resuspension system

A system to resuspend carbon black particles for providing submicron aerosols for inhalation exposure studies has been developed. The effect of continuous exposure to carbonaceous material (as a surrogate for the carbonaceous particles in diesel exhaust) on the pulmonary clearance of inhaled diesel tracer particles was studied in male Fischer 344 rats. Submicron carbon black particles with a mass median aerodynamic diameter (MMAD) of 0.22 micron and a size distribution similar to that of exhaust particles from a GM 5.7-liter diesel engine were successfully generated and administered to test animals at a nominal concentration of 6 mg/m3 for 20 hr/day, 7 days/week, for periods lasting 1 to 11 weeks. Immediately after the carbon black exposure, test animals were administered 14C-tagged diesel particles for 45 min in a nose-only chamber. The pulmonary retention of inhaled radioactive tracer particles was determined at preselected time intervals. Based upon the data collected up to 1 year postexposure, prolonged exposure to carbon black particles exhibits a similar inhibitory effect on pulmonary clearance as does prolonged exposure to diesel exhaust with a comparable particulate dose. This observation indicates that the excessive accumulation of carbonaceous material may be the predominant factor affecting lung clearance.     

A tale of two diesels

Two different samples of diesel exhaust particles (DEP) have been used by toxicologists interested primarily in cancer/genotoxicity or noncancer--such as pulmonary inflammation and asthma exacerbation--health end points. These are, respectively, a standard reference material, SRM 2975, from a heavy-duty diesel engine, and a sample collected by researchers at the Japanese National Institute for Environmental Studies from an automobile diesel engine. In this issue of Environmental Health Perspectives companion papers appear, by David DeMarini and co-workers and by Pramila Singh and co-workers, characterizing these samples and contrasting their Salmonella mutagenicity and pulmonary toxicity in mice. This commentary is a plea from an atmospheric chemist for more cooperation among toxicologists, analytical chemists, atmospheric chemists, and automotive and combustion engineers to provide a comprehensive assessment of health risks to humans exposed to contemporary diesel emissions and for greater quantities and more diverse types of DEP and ambient samples (i.e., SRMs) that can be shared and exhaustively characterized. This needs to be a continuing process as diesel engines, fuels, and exhaust components evolve in response to control regulations.     

Epidemiologic evidence for asthma and exposure to air toxics: linkages between occupational,indoor, and community air pollution research

Outdoor ambient air pollutant exposures in communities are relevant to the acute exacerbation and possibly the onset of asthma. However, the complexity of pollutant mixtures and etiologic heterogeneity of asthma has made it difficult to identify causal components in those mixtures. Occupational exposures associated with asthma may yield clues to causal components in ambient air pollution because such exposures are often identifiable as single-chemical agents (e.g., metal compounds). However, translating occupational to community exposure-response relationships is limited. Of the air toxics found to cause occupational asthma, only formaldehyde has been frequently investigated in epidemiologic studies of allergic respiratory responses to indoor air, where general consistency can be shown despite lower ambient exposures. The specific volatile organic compounds (VOCs) identified in association with occupational asthma are generally not the same as those in studies showing respiratory effects of VOC mixtures on nonoccupational adult and pediatric asthma. In addition, experimental evidence indicates that airborne polycyclic aromatic hydrocarbon (PAH) exposures linked to diesel exhaust particles (DEPs) have proinflammatory effects on airways, but there is insufficient supporting evidence from the occupational literature of effects of DEPs on asthma or lung function. In contrast, nonoccupational epidemiologic studies have frequently shown associations between allergic responses or asthma with exposures to ambient air pollutant mixtures with PAH components, including black smoke, high home or school traffic density (particularly truck traffic), and environmental tobacco smoke. Other particle-phase and gaseous co-pollutants are likely causal in these associations as well. Epidemiologic research on the relationship of both asthma onset and exacerbation to air pollution is needed to disentangle effects of air toxics from monitored criteria air pollutants such as particle mass. Community studies should focus on air toxics expected to have adverse respiratory effects based on biological mechanisms, particularly irritant and immunological pathways to asthma onset and exacerbation.     

Field measurement of diesel particulate matter emissions

A primary means to reduce environmental levels of diesel particulate matter (DPM) exposure to miners is to reduce the amount of DPM emission from the engine. A quick and economic method to estimate engine particulate emission levels has been developed. The method relies on the measurement of pressure increase across a filter element that is briefly used to collect a DPM sample directly from the engine exhaust. The method has been refined with the inclusion of an annular aqueous denuder to the tube which permits dry filter samples to be obtained without addition of dilution air. Tailpipe filter samples may then be directly collected in hot and water-supersaturated exhaust gas flows from water bath-cooled coal mine engines without the need for dilution air. Measurement of a differential pressure (DP) increase with time has been related to the mass of elemental carbon (EC) on the filter. Results for laboratory and field measurements of the method showed agreement between DP increase and EC collected on the filter with R(2) values >0.86. The relative standard deviation from replicate samples of DP and EC was 0.16 and 0.11, respectively. The method may also have applications beyond mining, where qualitative evaluation of engine emissions is desirable to determine if engine or control technology maintenance may be required.     

Studies of self-pollution in diesel school buses: methodological issues

Considerable interest has focused on levels of exhaust emissions in the cabins of diesel-powered school buses and their possible adverse health effects. Significantly different policy and engineering issues would be raised if compelling evidence found that inc-cabin contamination was due to self-pollution from bus emissions, rather than ambient pollution, neighboring vehicles, and/or re-entrained road dust. We identified 19 reports from 11 studies that measured diesel exhaust particulate in the cabins of 58 school bus of various type. Studies were evaluated in light of their experimental design, their data quality, and their capacity to quantify self-pollution. Only one study had a true experimental design, comparing the same buses with and without emission controls, while four others used intentional tracers to quantify tail pipe and/or crankcase emissions. Although definitive data are still lacking, these studies suggest that currently available control technologies can nearly eliminate particulate self-pollution inside diesel school buses.     

作业场所柴油机废气颗粒物浓度水平的调查

随着柴油机在现代工业中的广泛应用，接触柴油机废气的人群也日益增多，柴油机废气由气体和颗粒物两部分组成，对人体健康可造成损害和影响。     

Bronchoalveolar inflammation after exposure to diesel exhaust: comparison between unfiltered and particle trap filtered exhaust

OBJECTIVES: Air pollution particulates have been identified as having adverse effects on respiratory health. The present study was undertaken to further clarify the effects of diesel exhaust on bronchoalveolar cells and soluble components in normal healthy subjects. The study was also designed to evaluate whether a ceramic particle trap at the end of the tail pipe, from an idling engine, would reduce indices of airway inflammation. METHODS: The study comprised three exposures in all 10 healthy never smoking subjects; air, diluted diesel exhaust, and diluted diesel exhaust filtered with a ceramic particle trap. The exposures were given for 1 hour in randomised order about 3 weeks apart. The diesel exhaust exposure apperatus has previously been carefully developed and evaluated. Bronchoalveolar lavage was performed 24 hours after exposures and the lavage fluids from the bronchial and bronchoalveolar region were analysed for cells and soluble components. RESULTS: The particle trap reduced the mean steady state number of particles by 50%, but the concentrations of the other measured compounds were almost unchanged. It was found that diesel exhaust caused an increase in neutrophils in airway lavage, together with an adverse influence on the phagocytosis by alveolar macrophages in vitro. Furthermore, the diesel exhaust was found to be able to induce a migration of alveolar macrophages into the airspaces, together with reduction in CD3+CD25+ cells. (CD = cluster of differentiation) The use of the specific ceramic particle trap at the end of the tail pipe was not sufficient to completely abolish these effects when interacting with the exhaust from an idling vehicle. CONCLUSIONS: The current study showed that exposure to diesel exhaust may induce neutrophil and alveolar macrophage recruitment into the airways and suppress alveolar macrophage function. The particle trap did not cause significant reduction of effects induced by diesel exhaust compared with unfiltered diesel exhaust. Further studies are warranted to evaluate more efficient treatment devices to reduce adverse reactions to diesel exhaust in the airways.

 

     

Air pollution by 3,4-benzo(a)pyrene in mines using self-propelled equipment with diesel motors

The study was designed to analyse air pollution by 3,4-benz(a)pyrene released together with exhaust gases in 3 underground mines where self-propelled machines with diesel engines are used. Concentration levels for 3,4-BP have been identified in air, dust, sweeping away and scraping off the walls of the mine working surface. It is demonstrated that in a great number of samples 3,4-BP concentration exceeds MAC. A technique for 3,4-BP air sampling and analysis has been studied by means of liquid chromatography with ultraviolet detection. Hygienic recommendations on decreasing 3,4-BP release into the mine air are set forth.     

Chemical content and estimated sources of fine fraction of particulate matter collected in Krakow

The monitored level of pollution remains high in Krakow, Poland. Alerts regarding increased levels of pollution, which advise asthmatics, the elderly, and children to limit their exposure to open air, continue to be issued on numerous days. In this work, seasonal variations in PM2.5 (particulate matter containing particles with aerodynamic diameter no higher than 2.5 μm) concentrations are shown. An increasing trend is reported, which is enhanced during the colder seasons. The mean PM2.5 concentrations in Krakow exceeded the target value of 25 μg/m³ specified for 2015 in the spring, autumn, and winter seasons. For this reason, particulate matter pollution is of special concern. Elemental concentrations as well as the presence of black carbon (BC) and black smoke (BS) in PM2.5 samples were determined. Seasonal variations of Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Br, Rb, Sr, and Pb concentrations were observed whereas V, Cr, Ni, BC, and BS concentrations did not significantly change with the time of year. Seven factors were identified by the positive matrix factorization (PMF) technique, and one was non-identified. They were attributed to the following sources of pollution: steel industry, traffic (diesel exhaust), traffic (gasoline exhaust, brake wear), road dust, construction dust, combustion (biomass, coal), and non-ferrous metallurgical industry. The last, non-identified source, could be attributed to secondary aerosols. It is worth to mention that combustion shows significant seasonal variations with a high impact in winter. The reported results of the completed studies may significantly aid in solving air quality issues in the city by highlighting major sources of air pollution.     

Exposures to diesel exhaust in the International Brotherhood of Teamsters, 1950-1990

A prior case-control study found a positive, monotonic exposure-response relationship between exposure to diesel exhaust and lung cancer among decedents of the Central States Conference of the International Brotherhood of Teamsters. In response to critiques of the Teamsters' exposure estimates by the Health Effects Institute's Diesel Epidemiology Panel, historical exposures and associated uncertainties are investigated here. Historic diesel exhaust exposures are predicted as a function of heavy-duty diesel truck emissions, increasing use of diesel engines, and occupational elemental carbon (EC) measurements taken during the late 1980s and early 1990s. EC from diesel and nondiesel sources is distinguished in light of recent studies indicating a substantial contribution of gasoline vehicles to ambient EC. Monte Carlo sampling is used to characterize exposure distributions. The methodology used in this article-a probabilistic model for historical exposure assessment-is novel.     

Diesel exhaust exposure and lung cancer: a case--control study

The presence of polyaromatic hydrocarbons in the particulate phase of diesel engine exhaust has raised questions concerning potential carcinogenicity of diesel exhaust exposure. A case-control study was conducted of 502 male lung cancer cases and 502 controls without tobacco-related diseases to investigate the association of occupational diesel exhaust exposure and lung cancer. Diesel exhaust exposure was appraised by job title. The results show no association between diesel exhaust exposure and risk of lung cancer. They do, however, show the strong association between smoking and lung cancer and as such highlight the importance of smoking information in studies of occupational effect on lung cancer risk.     

Evaluation of emission characteristics and compliance of emission standards for in-use petrol driven vehicles in Delhi

The tail pipe CO (carbon monoxide) and HC (hydrocarbon) emission characteristics of in-use petrol driven vehicles were evaluated between November 1996 through September 1997 in Delhi. A total of 4300 vehicles were checked at CRRI Pollution Checking Centre. Approximately 90% of the total vehicles meet the prescribed CO emission standards even without following routine I/M practices. The age of the vehicles appeared to have influence on the emission characteristics. The non-compliance level was found to be higher for older vehicles. Insignificant correlation was observed between CO and HC emissions for all categories of in-use petrol driven vehicles. The emission reduction (gain) in CO and HC emissions was observed for two wheelers equipped with four-stroke engines and four wheelers fitted with catalytic converters over their respective conventional vehicles. The observed high compliance levels indicate that existing tail pipe emission standards are lenient and need to be reviewed. The emission standards are proposed for different categories of in-use petrol driven vehicles.     

Analysing the causes of chronic cough: relation to diesel exhaust, ozone, nitrogen oxides, sulphur oxides and other environmental factors

Air pollution remains a leading cause of many respiratory diseases including chronic cough. Although episodes of incidental, dramatic air pollution are relatively rare, current levels of exposure of pollutants in industrialized and developing countries such as total articles, diesel exhaust particles and common cigarette smoke may be responsible for the development of chronic cough both in children and adults. The present study analyses the effects of common environmental factors as potential causes of chronic cough. Different PubMed-based researches were performed that related the term cough to various environmental factors. There is some evidence that chronic inhalation of diesel can lead to the development of cough. For long-term exposure to nitrogen dioxide (NO2), children were found to exhibit increased incidences of chronic cough and decreased lung function parameters. Although a number of studies did not show that outdoor pollution directly causes the development of asthma, they have demonstrated that high levels pollutants and their interaction with sunlight produce ozone (O3) and that repeated exposure to it can lead to chronic cough. In summary, next to the well-known air pollutants which also include particulate matter and sulphur dioxide, a number of other indoor and outdoor pollutants have been demonstrated to cause chronic cough and therefore, environmental factors have to be taken into account as potential initiators of both adult and pediatric chronic cough.