Airborne pollutant

As an exercise, let s adapt this model of the analytical approach to a real problem. For our example, we will use the determination of the sources of airborne pollutant particles. A description of the problem can be found in the following article ... 

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

National Research Council, "Human exposure assessment for airborne pollutants advances and opportunities," National Academy Press, Washington, DC, 1991. 

Winegar, E. D., and Keith, L.H., "Sampling and Analysis of Airborne Pollutants." Lewis Publishers, Boca Raton, FL, 1993. 

Except for fine particulate matter (0.2 /xm or less), which may remain airborne for long periods of time, and gases such as carbon monoxide, which do not react readily, most airborne pollutants are eventually removed from the atmosphere by sedimentation, reaction, or dry or wet deposition. 

P. J. Lioy, Human Exposure Assessment for Airborne Pollutants, National Academy Press, Washington, D.C.(1991). 

Provision and use of appropriate health surveillance, e.g. for signs of dermatitis, asthma, effects of specific solvent exposures. Full use of any spray booth, enclosure, exhaust ventilation or dilution systems, and automatic handling equipment. (The efficiency of all local exhaust ventilation and other control systems should be maintained, and checked by testing.) Where appropriate, atmospheric monitoring of airborne pollution levels. 

The parameters about which the least is known are the diffusion parameters and Og, which govern diffusion transport of pollutants within a plume. These parameters are not monitored by meteorological stations and must always be approximated through indirect methods. Figure 4 illustrates the role each of these parameters has on the transport of airborne pollutants. 

Chapter 5 describes simplified methods of estimating airborne pollutant concentration distributions associated with stationary emission sources. There are sophisticated models available to predict and to assist in evaluating the impact of pollutants on the environment and to sensitive receptors such as populated areas. In this chapter we will explore the basic principles behind dispersion models and then apply a simplified model that has been developed by EPA to analyzing air dispersion problems. There are practice and study problems at the end of this chapter. A screening model for air dispersion impact assessments called SCREEN, developed by USEPA is highlighted in this chapter, and the reader is provided with details on how to download the software and apply it. 

Figure 1. Role of meteorological parameters in transport of airborne pollution.

The running of a cool airflow under a warm wind is another cause of temperature inversion. As a rule, the presence of an inversion implies a highly stable atmosphere one in which vertical air movements is rapidly damped out. In such a situation, fog and airborne pollutants collect, being unable to move freely or be dissipated by convection. 

Additional dispersal problems may occur when the prevailing wind occurs perpendicular to the valley or hill ridgeline. This may lead to speed up and turbulence over the valley or it may simply reduce the effect of airflow carrying away airborne pollutants. 

The gaseous emissions from the FCC unit are CO, NOj, particulates, and SOj. All are either locally or nationally regulated. Table 10-7 shows the current allowable limits of the EPA New Source Performance Standards (NSPS) for the emissions of these airborne pollutants. NSPS levels can be triggered by one of the following conditions ... 

Experimental exposure of several agricultural crops to ambient levels of acidic pollutants has not established measurable yield responses although foliar damage has been observed. Complex interactions with other airborne pollutants, particularly ozone, makes it difficult to exactly establish the damages that may be attributed to acidic deposition 14), It has not been possible to establish any critical level of acidic deposition in relation to crop damages. 

Implications to Humans. Acidic precipitation has not been observed with concentrations that pose a concern to human exposure. The acidic airborne pollutants in the particulate or gaseous forms such as the oxides of sulphur and of nitrogen, and the associated photochemical oxidant ozone, are inhaled. This may lead to the irritation of the respiratory tract, and subsequently to impaired lung function, aggravated asthma and bronchitis. 

Long-Range Transport of Airborne Pollutants, Research and Monitoring Coordinating Conunittee, Canada LRTAP Assessment, Atmospheric Environment Service, Environment Canada, Downsview, Ontario, 1990,7 Volumes. 

Agricultural crops, effect of acidification, 52 Agricultural productivity, biocides-net productivity relationship, 307-308 Agricultural technologies, changes, 311,313 Airborne contaminants, description, 135 Airborne pollutant, definition, 135 Air pollutants, classifications, 66 Air pollution effects, 166,167r scope, 21-22 sources, 165-166 state, 4... 

Although selection of the appropriate analysis techniques is often very problem specific, the basic elements of human health risk analysis are few, as presented in Figure 1. The figure shows that the aggregate risk to human health from exposure to an airborne pollutant results from two factors (1) the spread of the primary agent (and/or its... 

Because the significance of exposure has only been considered over the past few years, there is not as wide a selection of exposure models available as that for fate models. The latter have been applied for several decades to the calculation of ambient exposure levels compared with some standard values. Papers illustrative of human exposure assessments in this symposium include one on airborne pollutant exposure assessments by Anderson (2), a generic approach to estimating exposure in risk studies by Fiksel (5), and a derivation of pollutant limit values in soil or water based on acceptable doses to humans by Rosenblatt, Small and Kainz (6). 

Bronchial asthma is defined as a chronic inflammatory disease of the lungs it affects an estimated 9 to 12 million individuals in the U.S. Furthermore, its prevalence has been increasing in recent years. Asthma is characterized by reversible airway obstruction (in particular, bronchospasm), airway inflammation, and increased airway responsiveness to a variety of bronchoactive stimuli. Many factors may induce an asthmatic attack, including allergens respiratory infections hyperventilation cold air exercise various drugs and chemicals emotional upset and airborne pollutants (smog, cigarette smoke). 

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