Aerosols Mists or Dusts

Depending on the concentration of agent aerosols, the effects begin to appear 30 seconds to 2 minutes after initial exposure. 

Typically, there is a latent period with no visible effects between the time of exposure and the sudden onset of symptoms. This latency can range from 1 minutes to 18 hours and is affected by factors such as the amount of agent involved, the amount of skin surface in contact with the agent, and previous exposure to materials that chap or dry the skin (e.g., organic solvents such as gasoline or alcohols). Moist, sweaty areas of the body are more susceptible to percutaneous penetration by solid nerve agents. 

Another key factor is the part of the body that is exposed to the agent. It takes more time for the agent to penetrate areas of the body that are covered by thicker and tougher skin. The regions of the body that allow the fastest percutaneous penetration are the groin, head, and neck. The least susceptible body regions are the hands, feet, front of the knee, and outside of the elbow. 

---

Confined Explosions. In situations where the vapors are confined within a building, vessel, or other such enclosure, flammable materials with flash points below the temperature within the enclosure may have the potential for an explosion. Similarly, in confined situations, combustible materials, regardless of temperature, can pose a potential for explosion if dispersed as an aerosol, mist, or dust. 

Airborne partieulate matter may eomprise liquid (aerosols, mists or fogs) or solids (dust, fumes). Refer to Figure 5.2. Some eauses of dust and aerosol formation are listed in Table 4.3. In either ease dispersion, by spraying or fragmentation, will result in a eonsiderable inerease in the surfaee area of the ehemieal. This inereases the reaetivity, e.g. to render some ehemieals pyrophorie, explosive or prone to spontaneous eombustion it also inereases the ease of entry into the body. The behaviour of an airborne partiele depends upon its size (e.g. equivalent diameter), shape and density. The effeet of partiele diameter on terminal settling veloeity is shown in Table 4.4. As a result ... 

Airborne particulate matter may comprise liquid (aerosols, mists or fogs) or solids (dust, fumes). Refer to Figure 4.2. In either case dispersion, by spraying or fragmentation, will... 

For aerosols of nonvolatile liquid and powdery compounds, the concentration of the mist or dust atmosphere must be expressed in terms of milligrams per liter or milligrams per cubic meter (mg/m3) of air. With advances in biotechnology, many pharmacological testing techniques are based on specific receptor bindings, in which the ratio of the number of molecules to those of the receptors are considered, in... 

Inhalation in the form of an aerosol (p. 12), a gas, or a mist permits drugs to be applied to the bronchial mucosa and, to a lesser extent, to the alveolar membranes. This route is chosen for drugs intended to affect bronchial smooth muscle or the consistency of bronchial mucus. Furthermore, gaseous or volatile agents can be administered by inhalation with the goal of alveolar absorption and systemic effects (e.g inhalational anesthetics, p. 218). Aerosols are formed when a drug solution or micron-ized powder is converted into a mist or dust, respectively. 

Acute inhalation toxicity can be conducted in an exposure chamber. It is recommended, but not required, that nose-only or head-only exposure be used for aerosol studies to minimize oral exposures due to animals licking compound off their fur. For nongaseous pesticides, introduction of the sample in the form of mist or dust becomes a necessity. The animals are exposed for 4 hr and then transferred to other containers for observations for at least 14 d. The median lethal concentration obtained is referred to as inhalation LC30 (Anonymous, 1998). 

Aerosol A fine aerial suspension of liquid, fog or mist or solid, dust, fume or smoke particles sufficiently small in size to be stable. 

AEROSOLS, aerocolloids, or aerodispersed systems are collections of tiny particles suspended in gases. They include clouds of suspended matter ranging from haze and smoke to dusts and mists, fogs, or sprays. The science and technology of aerosols matured rapidly in the twentieth century as a result of the increasing interest in their chemistry and physics. 

The principle of all aerosols is that a liquefied gas in a pressurised container will provide a constant pressure while the container is being emptied. The essential components of an aerosol beside the container itself are the product, propellant, and valve assembly. The valve is designed to dispense the product in the required manner while maintaining both the product and propellant hermetically sealed until the product is expended. The fact that the product is sealed in the container and protected from air and other outside contaminants has obvious advantages in the field of pharmaceuticals. The intimate mixture of propellant and product in a true aerosol results in a rapid expansion of the propellant as it leaves the valve orifice. This breaks up the product into small particles giving a fine mist, coarse spray, foam, or dust according to the nature and relative quantity of the product and the propellant and the type of valve. 

The following table gives threshold limit values for a number of substances that may be encountered in the atmosphere of a chemical laboratory or industrial facility. All values refer to the concentration in air at 25 °C and normal atmospheric pressure. Data for gases are given in parts per million by volume (ppm). Values for liquids refer to mists or aerosols, and those for solids to dusts or fumes both are stated in mass concentration (mg/m ). A C preceding a value indicates a ceiling limit, which should not be exceeded even for very brief periods because of acute toxic effects of... 

Very small pieces of solid or liquid matter, such as particles of soot, dust, aerosols, fumes, or mists, past climate analogs... 

Inhalation—Taking gases, vapors, dust, smoke, fumes, aerosols, and/or mists into the body by breathing in. 

Aerosols are systems in which there exists a condensed phase of one material (solid or liquid) that is dispersed in a gaseous phase and that has dimensions that fall into the colloidal range. There are two subclasses of aerosols depending on whether the dispersed phase is a liquid or a solid. There cannot be, of course, a dispersion of one gas in another. Where the dispersed phase is a liquid, the system is commonly referred to as a mist or a fog. For solid aerosols, one may commonly refer to a dust or smoke. Each class of aerosol has its own characteristics of formation and stabilization and will be discussed briefly below. 

Airborne radioactive material—Any radioactive material dispersed in the air in the form of dust, fumes, mists, aerosols, vapors, or gases. 

In the laboratory you may form mists or aerosols when a bottle of chemical is opened, when the contents of an open bottle are shaken, when chemicals are poured into other vessels, or when a chemical is spilled and hits a solid surface. Fumes are a colloidal suspension of solid or liquid particles. Grinding a metal can generate fiimes when the metal gets hot enough to vaporize but then quickly cools and recondenses to a solid in the form of tiny small particles. Fuming sulfuric acid and fuming nitric acid produce clouds of these acids over the surfaces of the liquids. Dusts are solid particles suspended... 

Aerosol A dispersion of itucroscopic solid or liquid particles in air. Solid aerosols are classified as dust, fume or smoke. Liquid aerosols are considered either mist or fog. 

INHALATION The breathing in of an airborne substance, such as a GAS, FUME, MIST, VAPOR, DUST, OR AEROSOL. 

An aerosol is a suspension of solid or liquid particles in a gas such as air. Smoke, fumes and dusts are airborne suspensions of solid particles, i.e. solid aerosols. Mists and fogs are airborne suspensions of liquid particles, i.e. liquid aerosols. 

---