Vehicle Emission Levels Research Articles

Environmental risk factors and allergic bronchial asthma

The prevalence of allergic respiratory diseases such as bronchial asthma has increased in recent years, especially in industrialized countries. A change in the genetic predisposition is an unlikely cause of the increase in allergic diseases because genetic changes in a population require several generations. Consequently, this increase may be explained by changes in environmental factors, including indoor and outdoor air pollution. Over the past two decades, there has been increasing interest in studies of air pollution and its effects on human health. Although the role played by outdoor pollutants in allergic sensitization of the airways has yet to be clarified, a body of evidence suggests that urbanization, with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases observed in most industrialized countries, and there is considerable evidence that asthmatic persons are at increased risk of developing asthma exacerbations with exposure to ozone, nitrogen dioxide, sulphur dioxide and inhalable particulate matter. However, it is not easy to evaluate the impact of air pollution on the timing of asthma exacerbations and on the prevalence of asthma in general. As concentrations of airborne allergens and air pollutants are frequently increased contemporaneously, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of allergic respiratory allergy and bronchial asthma. Pollinosis is frequently used to study the interrelationship between air pollution and respiratory allergy. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc) can affect both components (biological and chemical) of this interaction. By attaching to the surface of pollen grains and of plant-derived particles of paucimicronic size, pollutants could modify not only the morphology of these antigen-carrying agents but also their allergenic potential. In addition, by inducing airway inflammation, which increases airway permeability, pollutants overcome the mucosal barrier and could be able to "prime" allergen-induced responses. There are also observations that a thunderstorm occurring during pollen season can induce severe asthma attacks in pollinosis patients. After rupture by thunderstorm, pollen grains may release part of their cytoplasmic content, including inhalable, allergen-carrying paucimicronic particles.

Measuring and Modeling Emission Effects for Toll Facilities

At conventional pay tolls, vehicles joining a queue must come to a stop and undergo several stop-and-go cycles until payment is completed. As a result, emissions increase because of excessive delays, queuing, and speed change cycles for approaching traffic. The main objective of this research is to quantify traffic and emission impacts of toll facilities in urban corridors. As a result of experimental measurements of traffic and emissions, the impact of traffic and emission performance of conventional and electronic toll facilities is presented. The approach attempts to explain the interaction between toll system operational variables (traffic demand, service time, and service type) and system performance variables (stops, queue length, and emissions). The experimental data for validating the numerical traffic model were gathered on pay tolls located in three main corridors that access the city of Lisbon, Portugal. The emissions model is based on real-world onboard measurements of vehicle emissions. With the appropriate speed profiles of vehicles in pay tolls, onboard emission measurements were carried out to quantify the relationships between vehicle dynamics and emissions. The main conclusion of this work is that there are two different types of stop-and-go driving cycles for vehicles joining the queue at a conventional toll booth: short and long. The length of each cycle depends on the expected queue length at the toll booth and the frequency of each cycle directly affects the level of vehicle emissions. The greatest percentage of emissions for a vehicle that stops at a pay toll is due to its final acceleration back to cruise speed after leaving the pay toll.

Measuring and Modeling Emission Effects for Toll Facilities

At conventional pay tolls, vehicles joining a queue must come to a stop and undergo several stop-and-go cycles until payment is completed. As a result, emissions increase because of excessive delays, queuing, and speed change cycles for approaching traffic. The main objective of this research is to quantify traffic and emission impacts of toll facilities in urban corridors. As a result of experimental measurements of traffic and emissions, the impact of traffic and emission performance of conventional and electronic toll facilities is presented. The approach attempts to explain the interaction between toll system operational variables (traffic demand, service time, and service type) and system performance variables (stops, queue length, and emissions). The experimental data for validating the numerical traffic model were gathered on pay tolls located in three main corridors that access the city of Lisbon, Portugal. The emissions model is based on real-world onboard measurements of vehicle emissions. With the appropriate speed profiles of vehicles in pay tolls, onboard emission measurements were carried out to quantify the relationships between vehicle dynamics and emissions. The main conclusion of this work is that there are two different types of stop-and-go driving cycles for vehicles joining the queue at a conventional toll booth: short and long. The length of each cycle depends on the expected queue length at the toll booth and the frequency of each cycle directly affects the level of vehicle emissions. The greatest percentage of emissions for a vehicle that stops at a pay toll is due to its final acceleration back to cruise speed after leaving the pay toll.

ACUTE RESPIRATORY HEALTH EFFECTS OF AIR POLLUTION ON ASTHMATIC CHILDREN IN US INNER CITIES

ISEE-57 Introduction: Asthmatic children living in inner-city communities are a particularly vulnerable subgroup, both because of their underlying airways disease and their exposure to relatively high levels of motor vehicle emissions. Objective: To investigate the association between short-term fluctuations in outdoor air pollution concentrations and pulmonary function and respiratory symptoms among inner-city asthmatic children. Methods: Between August 1998 and July 2001, 937 moderate-to-severe asthmatic children (age 5–12 years) living in seven US urban communities performed two-week epochs of twice-daily home pulmonary function testing every six months for two years. Every two months, the parent completed a standardized telephone interview about asthma symptoms. Daily measurements of the concentration of PM2.5, O3, NO2, SO2, and CO during the period of health data collection were obtained from the EPA’s Aerometric Information Retrieval System database. The relationship of lung function and symptoms to fluctuations in air pollutant concentrations were analyzed by time-series analysis using mixed effects models. Results: Almost all air pollutant concentrations measured in the study communities were below the National Ambient Air Quality Standards. In single-pollutant models, all five pollutants examined were associated with reduced FEV1 and increased frequency of missing school due to asthma. The concentrations of SO2, NO2, and CO were also associated with increased asthma symptoms. In three-pollutant models including O3, PM2.5, and CO as a surrogate for motor vehicle emissions, all three pollutants were independently associated with reduced lung function, and O3 and CO were associated with increased symptoms. In these models, increases in O3 and CO were independently associated with missing one or more school days due to asthma per 2 weeks (for 20 ppb increase in O3: OR = 1.88, 95% CI 1.47–2.42; for 1.0 ppm increase in CO: OR = 1.76, 95% CI 1.25–2.48). Conclusion: Among inner-city asthmatic children, short-term increases in air pollutant concentrations were associated with adverse health outcomes including reduced pulmonary function, respiratory symptoms, and missed school days related to asthma. Although the observed associations cannot be attributed with certainty to individual pollutants, the associations with CO, likely acting as a surrogate for other pollutants, suggests that one or more components of motor vehicle emissions may be causing excess morbidity among this vulnerable population.

Outdoor air pollution, climatic changes and allergic bronchial asthma.

Both the prevalence and severity of respiratory allergic diseases such as bronchial asthma have increased in recent years. Among the factors implicated in this "epidemic" are indoor and outdoor airborne pollutants. Urbanisation with its high levels of vehicle emissions and Westernised lifestyle parallels the increase in respiratory allergy in most industrialised countries, and people who live in urban areas tend to be more affected by the disease than those of rural areas. In atopic subjects, exposure to air pollution increases airway responsiveness to aeroallergens. Pollen is a good model with which to study the interrelationship between air pollution and respiratory allergic diseases. Biological aerosols carrying antigenic proteins, such as pollen grains or plant-derived paucimicronic components, can produce allergic symptoms. By adhering to the surface of these airborne allergenic agents, air pollutants could modify their antigenic properties. Several factors influence this interaction, i.e., type of air pollutant, plant species, nutrient balance, climatic factors, degree of airway sensitisation and hyperresponsiveness of exposed subjects. However, the airway mucosal damage and the impaired mucociliary clearance induced by air pollution may facilitate the penetration and the access of inhaled allergens to the cells of the immune system, and so promote airway sensitisation. As a consequence, an enhanced immunoglobulin E-mediated response to aeroallergens and enhanced airway inflammation favoured by air pollution could account for the increasing prevalence of allergic respiratory diseases in urban areas.

Environmental urban factors (air pollution and allergens) and the rising trends in allergic respiratory diseases.

Respiratory allergic diseases such as rhinitis and bronchial asthma appear to be increasing worldwide, affecting in particular subjects living in urban areas, and the reasons for this increase are still largely unknown. Although the role played by air pollution has yet to be clarified, a body of evidence suggests that urbanization, with its high levels of vehicle emissions and a westernised lifestyle are linked to the rising frequency of these diseases observed in most industrialized countries. Laboratory studies confirm the epidemiological evidence that inhalation of some pollutants, either individually or in combination, adversely affect lung function in asthmatics. Air pollutants may not only increase the frequency and intensity of symptoms in already allergic patients but may promote airway sensitization to airborne allergens in predisposed subjects. By attaching to the surface of pollen grains and of plant-derived paucimicronic particles, pollutants can modify the morphology of these antigen-carrying agents and alter their allergenic potential. In addition, by inducing airway inflammation, pollutants may overcome the mucosal barrier and so "prime" allergen-induced responses. In other words airway mucosal damage and impaired mucociliary clearance induced by air pollution may facilitate the access of inhaled allergens to the cells of the immune system.

The role of outdoor air pollution and climatic changes on the rising trends in respiratory allergy

Evidence suggests that allergic respiratory diseases such as hay fever and bronchial asthma have become more common world-wide in the last two decades, and the reasons for this increase are still largely unknown. A major responsible factor could be outdoor air pollution, derived from cars and other vehicles. Studies have demonstrated that urbanization and high levels of vehicle emissions and westernized lifestyle is correlated with the increasing frequency of pollen-induced respiratory allergy. People who live in urban areas tend to be more affected by pollen-induced respiratory allergy than those from of rural areas. Pollen allergy has been one of the most frequent models used to study the interrelationship between air pollution and respiratory allergic diseases. Pollen grains or plant-derived paucimicronic components carry allergens that can produce allergic symptoms. They may also interact with air pollution (particulate matter, ozone) in producing these effects. There is evidence that air pollutants may promote airway sensitization by modulating the allergenicity of airborne allergens. Furthermore, airway mucosal damage and impaired mucociliary clearance induced by air pollution may facilitate the access of inhaled allergens to the cells of the immune system. In addition, vegetation reacts with air pollution and environmental conditions and influence the plant allergenicity. Several factors influence this interaction, including type of air pollutants, plant species, nutrient balance, climatic factors, degree of airway sensitization and hyperresponsiveness of exposed subjects.

Drivers' familiarity with urban route network layout in Amman, Jordan

Abstract Advanced traveler information systems (ATISs) have attracted a considerable amount of attention in recent years. By providing drivers with traffic information, these information systems are likely to help in reducing travel time, traffic-related congestion and consequently lead to reduced levels of vehicle emissions. With the presence of in-car navigation and communication systems, the ATIS can benefit commuters as well as unfamiliar drivers. However, in the absence of in-car navigation systems – the case in most developing countries, familiar drivers are likely to use these information systems more effectively and hence are likely to make well-informed route-diversion and other travel-oriented decisions. This paper is devoted to developing driver familiarity models to identify the factors that influence drivers' familiarity with the urban route network layout. A number of non-linear familiarity models are developed and coefficients are estimated. Estimation results indicate that travel characteristics such as familiarity with one alternative route, residence leaving times, travel time to job location and the presence of young children have a profound impact on the driver's level of familiarity. Separate familiarity models for male and female drivers are also specified and estimated. When subjected to the same set of predictors, the familiarity of male drivers turned out to be more responsive than the familiarity of female drivers. This result could reflect, among other things, the fact that male drivers have more frequent and diverse activity stops that expose them to different sections of the transportation network layout.

Will new technology be sufficient to solve the problem of air pollution caused by Swedish road transport?

In this article, levels of future specific vehicle emissions and the energy efficiency required to match long-term environmental targets are estimated. The possibility of reaching these targets is also evaluated. It appears to be possible to achieve sufficiently large reductions in both nitrogen oxide (NO x ) and non-methane volatile organic compound (NMVOC) emission to meet long-term Swedish environmental requirements even with continuing transport growth. Combining sufficiently large carbon dioxide reductions with transport growth seems to be more difficult and would require major breakthroughs regarding drive systems, materials and vehicle construction. Such technological developments cannot, however, be entirely ruled out.

The sources and behaviour of tropospheric anthropogenic volatile hydrocarbons

Abstract A review of literature regarding tropospheric anthropogenic volatile hydrocarbons is undertaken in order to assess trends in concentrations and the behaviour of these compounds in the troposphere. The impact of control legislation on vehicle emission levels is discussed. The volatile hydrocarbon composition of ambient air will usually reflect the location of sources, with high concentrations corresponding with urban and industrial areas. Once present in air volatile hydrocarbons perform important roles in oxidant and secondary aerosol formation. The impact upon the health of humans from exposure to tropospheric volatile hydrocarbons, especially aromatic compounds, is also an area of great importance. Volatile hydrocarbons are removed from tropospheric circulation by reaction and deposition processes.

Factors influencing vehicle idle emissions. Statistical analysis of New York State data

Research report: During 1972-76, the New York State Dept. of Environmental Conservation operated a voluntary idle emissions test program for vehicles throughout the state. About 25,000 vehicles were inspected. Statistical data collected from the program are discussed. Statistical analyses indicate that model year, manufacturer, number of cylinders, and vehicle age influence a vehicle's emission levels. (7 graphs, 11 references, 1 table)

Benefit-cost analysis of automotive emission reductions

This study examines the optimum automotive emission control levels within a marginal benefit-cost framework. We assume that benefits consist of market and nonmarket components. Cost of control is estimated from historical and projected data as published in the literature. The results of the analyses indicate that even with a high estimate of benefits, the economically optimal vehicle emission levels are strikingly less severe than those required by the 1970 Clean Air Act.