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Cross the alveolar membrane and trace your route out of the body through the nose

It has a sampler inlet criterion that is similar functionally equivalent to TPM but, as shown in table 10. Air Pollutants Pollutants can be dispersed in air at normal ambient temperatures and pressures in gaseous, liquid and solid forms.

The latter two represent suspensions of particles in air and were given the generic term aerosols by Gibbs 1924 on the basis of analogy to the term hydrosol, used to describe dispersed systems in water. Gases and vapours, which are present as discrete molecules, form true solutions in air.

Particles consisting of moderate to high vapour pressure materials tend to evaporate rapidly, because those small enough to remain suspended in air for more than a few minutes i. Some materials with relatively low vapour pressures can have appreciable fractions in both vapour and aerosol forms simultaneously. Gases and vapours Once dispersed in air, contaminant gases and vapours generally form mixtures so dilute that their physical properties such as density, viscosity, enthalpy and so on are indistinguishable from those of clean air.

Such mixtures may be considered to follow ideal gas law relationships. There is no practical difference between a gas and a vapour except that the latter is generally considered to be the gaseous phase of a substance that can exist as a solid or liquid at room temperature.

  • Allergic response Allergic responses involve the phenomenon known as sensitization;
  • The adverse reaction upon exposure to an irritating air contaminant is, however, an objective measurement, in contrast to subjective experiences like symptoms of different origin.

While dispersed in air, all molecules of a given compound are essentially equivalent in their size and probabilities of capture by ambient surfaces, respiratory tract surfaces and contaminant collectors or samplers.

Aerosols Aerosols, being dispersions of solid or liquid particles in air, have the very significant additional variable of particle size. Size affects particle motion and, hence, the probabilities of physical phenomena such as coagulation, dispersion, sedimentation, impaction onto surfaces, interfacial phenomena and light-scattering properties.

It is not possible to characterize a given particle by a single size parameter. For example, a particle's aerodynamic properties depend on density and shape as well as linear dimensions, and the effective size for light scattering is dependent on refractive index and shape.

In some special cases, all of the particles are essentially the same in size. Such aerosols are considered to be monodisperse. Examples are natural pollens and some laboratory-generated aerosols. More typically, aerosols are composed of particles of many different sizes and hence are called heterodisperse or polydisperse.

Different aerosols have different degrees of size dispersion. It is, therefore, necessary to specify at least two parameters in characterizing aerosol size: Particles generated by a single source or process generally have diameters following a log-normal distribution; that is, the logarithms of their individual diameters have a Gaussian distribution.

In this case, the measure of dispersion is the geometric standard deviation, which is the ratio of the 84. When more than one source of particles is significant, the resulting mixed aerosol will usually not follow a single log-normal distribution, and it may be necessary to describe it by the sum of several distributions. Particle characteristics There are many properties of particles other than their linear size that can greatly influence their airborne behaviour and their effects on the environment and health.

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For spherical particles, the surface varies as the square of the diameter. However, for an aerosol of given mass concentration, the total aerosol surface increases with decreasing particle size. For non-spherical or aggregate particles, and for particles with internal cracks or pores, the ratio of surface to volume can be much greater than for spheres.

Particle volume varies as the cube of the diameter; therefore, the few largest particles in an aerosol tend to dominate its volume or mass concentration. A particle's shape affects its aerodynamic drag as well as its surface area and therefore its motion and deposition probabilities.

A particle's velocity in response to gravitational or inertial forces increases as the square root of its density. The diameter of a unit-density sphere having the same terminal settling velocity as the particle under consideration is equal to its aerodynamic diameter. Terminal settling velocity is the equilibrium velocity of a particle that is falling under the influence of gravity and fluid resistance.

Aerodynamic diameter is determined by the actual particle size, the particle density and an aerodynamic shape factor. Types of aerosols Aerosols are generally classified in terms of their processes of formation.

Although the following classification is neither precise nor comprehensive, it is commonly used and accepted in the industrial hygiene and air pollution fields.

An aerosol formed by mechanical subdivision of bulk material into airborne fines having the same chemical composition. An aerosol of solid particles formed by condensation of vapours formed by combustion or sublimation at elevated temperatures.

The primary particles are generally very small less than 0.

Pathogens Cross Protective Barriers to Colonize the Host

They may be chemically identical to the parent material, or may be composed of an oxidation product such as metal oxide. Since they may be formed in high number concentrations, they often rapidly coagulate, forming aggregate clusters of low overall density. An aerosol formed by condensation of combustion products, generally of organic materials. The particles are generally liquid droplets with diameters less than 0.

A droplet aerosol formed by mechanical shearing of a bulk liquid, for example, by atomization, nebulization, bubbling or spraying. An aqueous aerosol formed by condensation of water vapour on atmospheric nuclei at high relative humidities. A popular term for a pollution aerosol derived from a combination of smoke and fog.

It is now commonly used for any atmospheric pollution mixture. A submicrometer-sized aerosol of hygroscopic particles that take up water vapour at relatively low relative humidities. Aitken or condensation nuclei CN.

  • However, when distributed by the blood circulation to various organs, they can damage them or cause general poisoning and have systemic effects;
  • On the other hand, the chest wall tends to expand at lung volumes 1 to 2 litres above the FRC level.

Very small atmospheric particles mostly smaller than 0. A term given to the particles in the ambient atmosphere ranging from 0. These particles generally are spherical having liquid surfacesand form by coagulation and condensation of smaller particles that derive from gaseous precursors. Being too large for rapid coagulation and too small for effective sedimentation, they tend to accumulate in the ambient air.

Ambient air particles larger than about 2. Biological Responses of the Respiratory System to Air Pollutants Responses to air pollutants range from nuisance to tissue necrosis and death, from generalized systemic effects to highly specific attacks on single tissues.

Host and environmental factors serve to modify the effects of inhaled chemicals, and the ultimate response is the result of their interaction. The main host factors are: The environmental factors include the concentration, stability and physicochemical properties of the agent in the exposure environment and the duration, frequency and route of exposure.

  • The pathogenic bacteria and parasites that infect these epithelial surfaces have specific mechanisms for overcoming these host cleaning mechanisms;
  • Compounds that can cause parenchymal damage are considered toxic chemicals;
  • Viruses that infect animal cells generally use cell-surface receptor molecules that are either very abundant such as sialic- acid -containing oligosaccharides, which are used by the influenza virus or uniquely found on those cell types in which the virus can replicate such as the nerve growth factor receptor, the nicotinic acetylcholine receptor , or the cell-cell adhesion protein N-CAM , all of which are used by the rabies virus to specifically infect neurons;
  • The pathogen is a relatively passive participant, usually providing a trigger to initiate the invasion process, but not contributing any metabolic energy.

Acute and chronic exposures to a chemical may result in different pathological manifestations. Any organ can respond in only a limited number of ways, and there are numerous diagnostic labels for the resultant diseases. The following sections discuss the broad types of responses of the respiratory system which may occur following exposure to environmental pollutants.

Irritant response Irritants produce a pattern of generalized, non-specific tissue inflammation, and destruction may result at the area cross the alveolar membrane and trace your route out of the body through the nose contaminant contact.

Some irritants produce no systemic effect because the irritant response is much greater than any systemic effect, while some also have significant systemic effects following absorption-for example, hydrogen sulphide absorbed via the lungs.

At high concentrations, irritants may cause a burning sensation in the nose and throat and usually also in the eyespain in the chest and coughing producing inflammation of the mucosa tracheitis, bronchitis. Examples of irritants are gases such as chlorine, fluorine, sulphur dioxide, phosgene and oxides of nitrogen; mists of acids or alkali; fumes of cadmium; dusts of zinc chloride and vanadium pentoxide.

High concentrations of chemical irritants may also penetrate deep into the lungs and cause lung oedema the alveoli are filled with liquid or inflammation chemical pneumonitis. Exposure to irritants may result in death if critical organs are severely damaged.

On the other hand, the damage may be reversible, or it may result in permanent loss of some degree of function, such as impaired gas-exchange capacity. Fibrotic response A number of dusts lead to the development of a group of chronic lung disorders termed pneumoconioses.

This general term encompasses many fibrotic conditions of the lung, that is, diseases characterized by scar formation in the interstitial connective tissue.

Pneumoconioses are due to the inhalation and subsequent selective retention of certain dusts in the alveoli, from which they are subject to interstitial sequestration. Pneumoconioses are characterized by specific fibrotic lesions, which differ in type and pattern according to the dust involved. For example, silicosis, due to the deposition of crystalline-free silica, is characterized by a nodular type of fibrosis, while a diffuse fibrosis is found in asbestosis, due to asbestos-fibre exposure.

Certain dusts, such as iron oxide, produce only altered radiology siderosis with no functional impairment, while the effects of others range from a minimal disability to death. Allergic response Allergic responses involve the phenomenon known as sensitization. Initial exposure to an allergen results in the induction of antibody formation; subsequent exposure of the now "sensitized" individual results in an immune response-that is, an antibody-antigen reaction the antigen is the allergen in combination with an endogenous protein.

This immune reaction may occur immediately following exposure to the allergen, or it may be a delayed response. The primary respiratory allergic reactions are bronchial asthma, reactions in the upper respiratory tract which involve the release of histamine or histamine-like mediators following immune reactions in the mucosa, and a type of pneumonitis lung inflammation known as extrinsic allergic alveolitis.

In addition to these local reactions, a systemic allergic reaction anaphylactic shock may follow exposure to some chemical allergens. Infectious response Infectious agents can cause tuberculosis, anthrax, ornithosis, brucellosis, histoplasmosis, Legionnaires' disease and so on. Carcinogenic response Cancer is a general term for a group of related diseases characterized by the uncontrolled growth of tissues. Its development is due to a complex process of interacting multiple factors in the host and the environment.

One of the great difficulties in attempting to relate exposure to a specific agent to cancer development in humans is the long latent period, typically from 15 to 40 years, between onset of exposure and disease manifestation.

Examples of air pollutants that can produce cancer of the lungs are arsenic and its compounds, chromates, silica, particles containing polycyclic aromatic hydrocarbons and certain nickel-bearing dusts. Asbestos fibres can cause bronchial cancer and mesothelioma of the pleura and peritoneum.

Deposited radioactive particles may expose lung tissue to high local doses of ionizing radiation and be the cause of cancer. Systemic response Many environmental chemicals produce a generalized systemic disease due to their effects upon a number of target sites.

Lungs are not only the target for many harmful agents but the site of entry of toxic substances which pass through the lungs into the bloodstream without any damage to the lungs. However, when distributed by the blood circulation to various organs, they can damage them or cause general poisoning and have systemic effects. This role of the lungs in occupational pathology is not the subject of this article.

However, the effect of finely dispersed particulates fumes of several metal oxides which are often associated with an acute systemic syndrome known as metal fume fever should be mentioned. However, the aim of the measurements has to be clear before the examination, in order to interpret the results correctly. In this article we will discuss lung function examination with special regard to the occupational field. It is important to remember the limitations in different lung function measurements.

This is due to the fact that chronic effects occur years after the dust is inhaled and deposited in the lungs. On the other hand, acute temporary effects of organic and inorganic dust, as well as mould, welding fumes and motor exhaust, are well suited to study.

This is due to the fact that the irritative effect of these dusts will occur after a few hours of exposure. Acute or chronic lung function effects also may be discernible in cases of exposure to concentrations of irritating gases nitrogen dioxide, aldehydes, acids and acid chlorides in the vicinity of well documented exposure limit values, especially if the effect is potentiated by particulate air contamination.

Lung function measurements have to be safe for the examined subjects, and the lung function equipment has to be safe for the examiner. A summary of the specific requirements for different kinds of lung function equipment are available e.