Cigarettes background

The most detailed observations of extinction by the atmospheric particles responsible for the blue suns and moons widely observed in September 1950 were made by Wilson (1951). Subsequently, his and other data were thoroughly analyzed by Penndorf (1953). More recently, Porch et al. (1973) concluded on the basis of observations made at remote locations that bluing is a rather common property of the background (i.e., nonurban) aerosol. An elementary discussion of the blue moon, together with instructions on how to demonstrate one with cigarette smoke, was given by Bohren and Brown (1981). 

Combustion processes. Combustion is still a major source of these substances. PCDDs and PCDFs have been found in exhaust gases from a wide variety of combustion processes - from cigarette smoke to emissions by fossil fuel power plants. Stringent controls have been introduced on waste incinerators in the UK and several other countries. It is likely now that most formerly significant sources have been controlled, leaving diffuse combustion sources, e.g. bonfires and car exhausts, as major contributors to the environmental background. 

Ethylene oxide is a gas at room temperature and pressure therefore, inhalation is the primary route of exposure. Dermal exposures may occur to liquid ethylene oxide that exists at temperatures below 11°C however, rapid evaporation minimizes the opportunity for absorption. Background exposures to ethylene oxide occur due to its presence in cigarette smoke and automobile exhaust as well as its conversion from ethylene normally present in the body as the result of metabolic processes and the consumption of plants where it is a natural hormone. 

Because propane exists as a gas at normal temperature and pressure, exposure generally occurs by inhalation (trace amounts of propane have been measured in air expired by humans). Typical background concentrations detected at ground level in major US cities range from 0.050 to 0.4 ppm. It is possible to spill liquid propane from a pressurized tank, causing frostbite on skin contact due to rapid evaporation and loss of heat. Propane has also been detected in cigarette smoke ( 0.83 mg per cigarette). 

It is necessary to give some background into how this sort of testing is done. Cigarettes are smoked on a machine under the industry standard conditions mentioned in part one of this case study, and the smoke condensate is collected on a filter in the smoke machine. The filter is then placed in solvent, and the chemicals to be tested are extracted by the solvent. Most of the solvent is then removed, and an internal standard chemical is added. The sample is then diluted to a specified volume. 

Variations in peak shape and location between the measurements taken at 10 and 180 min after the introduction of cigarette smoke to an experimental chamber are presented in Fig. 6 [53]. It can be seen that during the latter measurement, the ETS peak is still clearly distinguishable from the background environmental aerosol spectrum and its location is shifted towards a larger size compared with the initial location. 

Some patients, mainly those with FLD, may evolve to a chronic obstmctive lung disease (25,26). The reason for these different outcomes (fibrosis vs. emphysema) is unknown, but it may be related with the characteristics in the inhaled antigen, the type of exposure, cigarette smoking status, and the genetic background. 

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