Airborne contaminants aerosols

Among the major potential hazards affecting working environment are chemical (airborne contaminants), biological, and physical hazards,. ir contaminants are commonly classified as either particulate contaminants or gas and vapor contaminants. Common particulate contaminants include dusts, fumes, mists, aerosols, and fibers. 

Chapter 4 described methods for limiting the time of exposure to weapons of mass destruction that utilize no explosives (e.g., aerosol delivery) or use of conventional explosives (e.g., dirty bomb). The basic procedure is to leave the contaminated area as quickly as possible, enter a nearby building to shelter against airborne contamination, remove soiled articles of clothing, and wash all exposed body parts (including the mouth and hair) as soon as possible. In Chapter 4, the time factor is applied primarily to limit the chances of potential future health effects. In this section, the time factor is applied after a nuclear explosion to prevent serious bodily harm and death. 

Plutonium is so toxic that processing and fabrication are always done in sealed cells or glove boxes, but accidental dispersions of aerosol occur from time to time. Following combustion of Pu metal chips in a production area at Rocky Flats, Colorado, in 1964, airborne contamination was widespread. Alpha tracks from individual particles caught on membrane filters were detected on nuclear film, and the Pu content, and hence the particle size, was deduced (Fig. 5.2, curve E). The activity median diameter was 0.3 /urn (Mann Kirchner, 1967). The same method, used during normal operations in a production area at Los Alamos, gave activity median diameters in the range 0.15 to 0.65 /urn (Moss et al., 1961). However, when a spill occurred, followed by clean-up operations, the Pu particles were found to be associated with inert dust particles of mass median diameter 7 /urn. 

Airborne contaminants existing in a laboratory have a variety of sources, but they are generally a mixture of particles generated within the laboratory itself and those already present in the air that is drawn into the room. The contaminants are normally in gaseous or particulate form, but liquids in form of aerosol can also occur. 

Cupitt (1980), however, considered the loss of 1,2-dichloroethane from the atmosphere by dissolution into rain drops or adsorption onto aerosols insignificant compared with loss from chemical degradation based on mathematical calculations. Since 1,1-dichloroethane has higher volatility and lower aqueous solubility than the 1,2-isomer, physical removal of 1,1 -dichloroethane from the atmosphere would be even less likely to be important (EPA 1985). Pellizzari et al. (1979) measured actual concentrations of airborne contaminants in the vicinity of known emission sources of 1,1-dichloroethane, making aerial transport the logical source of downwind concentrations. 

A third study evaluated S04 and exposure to 24 children (ages were not provided) living in Uniontown, Pennsylvania (Suh et al. 1992). This study did not focus on ammonia exposure per se, but on other airborne contaminant concentrations in aerosols found outdoors, indoors, and by personal monitors. It sought to determine how personal exposures to these aerosols correlated with indoor and outdoor concentrations. Ammonia concentrations were measured in order to assess their potential for neutralizing found in aerosols. Ammonia was found to be in highest concentrations near the children (detected by the personal monitors), followed by indoor concentrations, and were minimal outdoors. It was proposed that a large proportion of the found in indoor aerosols are neutralized by NH3, and thus would lower the children s exposure to acid aerosols. The authors noted that more research is needed to fully model the influence of factors, including NH3, on indoor acid aerosol exposure. 

The present purpose is to set down some guidelines for assessing the dry flux of acidic airborne contaminants to natural surfaces, and to discuss their limitations. For now, this dry flux will be taken to include all turbulent transfer of aerosol not associated with rainfall the reason for the subtlety will become apparent later. The matter will be considered in the light of three questions (a) how much acidic aerosol is present in air,... 

Particulates Particulates include dusts, fumes, smoke, aerosols, and mists. Particulates also have classifications by size and chemical makeup. Shape can also be important. For example, some particulates have long, thin, fibrous shapes. Others may be spherical and have a fairly imiform cross-section. Figure 25-5 (Chapter 25) provides size characteristics of some airborne contaminants. 

The potential for cross contamination exists during concrete decontamination, as many of the removal techniques are dusty or wet and therefore have a high potenial for contamination of other clean surfaces. As noted above, the slower, better controlled techniques, such as shot blasting, tend to minimize cross contamination while the cruder large surface techniques, such as grinding or hydroblasting, generate the most waste and the most airborne particulate/aerosol. 

A reasonable face velocity for airflow at the front of the hood is about 100 fpm (feet/minute) ( 20%). This airflow velocity alone is not a defining criterion for adequate hood performance. Containment of airborne contaminants is the essential and primary function of the hood as pictured in Figure 7.1.3.3. Hood effectiveness is its ability to capture and contain airborne chemicals within its boundaries. Several factors are interrelated in achieving this containment. In addition to face velocity, other equally important factors that contribute to containing airborne chemicals include what is in the hood, how you carry out operations, and the design of the hood. Thus, the mild draft of the face velocity ideally minimizes any aerosols or gases from escaping from the hood into the lab but the three other factors also have a marked influence on a hood s performance... 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Sihcone contamination has been impHcated as a cause of failure in telephone switching systems and other devices that contain relay switch contacts (507). Analysis of airborne particulates near telephone switching stations showed the presence of siUcones at these locations. Where the indoor use of sihcones is intentionally minimised, outdoor levels were found to be higher than inside concentrations (508). Samples of particulates taken at two New Jersey office buildings revealed sihcone levels that were considerably higher indoors than outdoors. In these cases, indoor sihcone aerosols are beheved to be generated primarily by photocopiers, which use sihcone fuser oils. 

Industrial environments expose individuals to a plethora of airborne chemical compounds in the form of vapors, aerosols, or biphasic mixtures of both. These atmospheric contaminants primarily interface with two body surfaces the respiratory tract and the skin. Between these two routes of systemic exposure to airborne chemicals (inhalation and transdermal absorption) the respiratory tract has the larger surface area and a much greater percentage of this surface exposed to the ambient environment. Or dinary work clothing generally restricts skin exposures to the arms, neck, and head, and special protective clothing ensembles further limit or totally eliminate skin exposures, but breathing exposes much of the airway to contaminants. 

Airborne inorganic acids exist in the industrial environment in the form of both vapors and particulates. This study was undertaken to answer a need for a simple sampling and analytical method for monitoring both vaporous and aerosol acid contaminants quantitatively. 

Airborne inorganic acids exist in the workplace environment as both vapors and particulates. To monitor for the common inorganic acids, a single, non-liquid sampling device to collect both vaporous and aerosol contaminants quantitatively, and an analytical method to determine these acids in a single sample was desired. 

While less hazardous than powders, potent compounds in solution may also become airborne and therefore lead to worker exposure. Operations that have the potential to create aerosols, such as sampling, sample preparation, sample transfers and purifications, should only be performed with appropriate engineering controls in place. It is important to clean surfaces that may have become contaminated during the... 

Ocular Effects. Effects on the eyes due to direct contact of the eyes with airborne mists, dusts, or aerosols or chromium compounds are described in Section 2.2.3.2. An extensive epidemiological survey was conducted of housewives who lived in an area of Tokyo, Japan, in which contamination from chromium slag at a construction site was discovered in 1973. The housewives included in the study were those who lived in the area from 1978 to 1988, and controls included housewives who lived in uncontaminated areas. Questionnaires, physical examinations, and clinical tests were conducted annually. Higher incidences of subjective complaints of eye irritation were reported by the exposed population than the control population in the early years of the survey, but in later years the difference between the two groups became progressively less (Greater Tokyo Bureau of Hygiene 1989). 

World Health Organization (WHO) identify Biosafety Levels 1,2, 3, and 4 and in the United Kingdom the Advisory Committee on Dangerous Pathogens (ACDP) categorizes Laboratory Containment Levels 1, 2, 3, and 4 (4-6). All share the same objective to identify biosafety or laboratory containment levels that minimize the risk to the laboratory worker, to the outside community, and to the environment. At Biosafety/Laboratory Containment Level 2, exposure risks to the laboratory worker arise mainly from contact through a contaminated work environment. As the risk of airborne infection increases, Biosafety/ Laboratory Containment Level 3 provides facilities to prevent aerosol transmission. Additional safeguards to protect the outside community and the environment are found at Biosafety/Laboratory Containment Level 4, which is... 

Atmospheric conditions and particle size determine the persistence of aerosolized toxin in the environment. Temperature and humidity extremes facilitate toxin degradation, and smaller particles dissipate more quickly into the atmosphere. Studies estimate that aerosolized toxin would decay between less than 1 and 4% per minute. At a 1% decay rate, insubstantial amounts of toxin would remain after 2 days (36). Although botulinum toxin can penetrate mucosal surfaces, it cannot penetrate intact skin. If a release were recognized or announced, and authorities anticipated potential airborne exposure, people could protect themselves by covering their mouths and noses with clothing, such as underwear, shirts, scarfs, or handkerchiefs. In addition, after exposure, washing with soap and water would decontaminate clothing, and a 0.1% hypochlorite bleach solution would be effective on contaminated objects and surfaces (36). 

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