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Evaluation and Control of Internal Radiation Exposures on the Basis of Committed Dose Equivalent
Published in Kenneth L. Miller, of Radiation Protection Programs, 2020
The ALI values for the inhalation of radionuclides in the form of radioactive particulates assume an activity median aerodynamic diameter (AMAD) of 1 μm and a geometric standard deviation of 4.5 or less for the aerosol. A total of 63% of the inhaled activity of this aerosol is expected to deposit in the three regions of the respiratory tract. Values are listed for various chemical compound forms of the radionuclide, which are designated as Class D, Class W, or Class Y and which correspond to half-clearance times, respectively, of 0.5, 50, and 500 days from certain compartments within the pulmonary region of the respiratory tract. The ALI value of inhalation when divided by the volume of 2400 m3 of air inhaled by Reference Man during 1 year of occupational exposure (calculated from a breathing rate of 1.2 m3 hr–1, 40 hr per week for 50 weeks per year) yields the DAC. This derived quantity has the same application as the previous MPC given in ICRP Publication 2 and NCRP Report 22.
Application and In-Use Testing of Hepa Filters
Published in Thomas A. Barber, Control of Particulate Matter Contamination in Healthcare Manufacturing, 1999
It is apparent from the data that the different substitute liquids do give concentrations that vary over a wide range, as would be expected based on their different physical properties; the droplet generation process is affected by both liquid viscosity and surface tension. More importantly, photometric reactions to the various substitute liquids do not seem to correspond to their concentrations in μg/L. The photometer used to collect the data in. Table 13.7 was calibrated against a DOP aerosol. Aerosol photometers utilize the forward light scattering principle as discussed earlier. The light scattered forward is a function of the aerosol diameter, and the aerosol of these substitute liquids may differ in aerosol mass median aerodynamic diameter from DOP. Thus, the aerosol photometer readings would not be expected to relate accurately with the actual gravimetric reading unless the photometer was calibrated initially against the particular aerosol. Refractive index differences between the oils shown in Table 13.5 are not great enough to cause significant differences in sizing. When using a substitute liquid for DOP. the variation in concentration must be considered. Also, the photometer and generator may be calibrated together using the actual substitute liquid to ensure accurate test results. Interestingly, Emery 3004 appears to elicit a stronger response from a photometer than DOP with 85 μg/L, giving a 125 percent response. This suggests that smaller quantities of Emery material may be used in testing.
Human health risk assessment of Tire and Road Wear Particles (TRWP) in air
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Marisa L. Kreider, Ken M. Unice, Julie M. Panko
Because the respiratory tract structure of animal models differs from the respiratory tract of humans, the dose of inhaled particles delivered to the human lung may differ from that delivered to the rat lung given the same external concentration of particulate. In order to scale an exposure concentration (external concentration) for particulate to determine a screening value applicable to humans, this difference needs to be considered. The U.S. EPA has developed a model for particulate matter to determine the regional deposited dose ratio (RDDR) between humans and a variety of animal models, including rat, mouse, and hamster, as part of their guidance for determining reference concentrations (RfCs) (U.S. EPA 2002). Using this model, one can input particulate characteristics, such as mass median aerodynamic diameter (MMAD) and geometric standard deviation of the MMAD to determine the RDDR. The RDDR is then used, according to Equation 2, to determine the human equivalent NOAEC (NOAECHEC).
Impact of power level and refill liquid composition on the aerosol output and particle size distribution generated by a new-generation e-cigarette device
Published in Aerosol Science and Technology, 2018
Jérémie Pourchez, Sandrine Parisse, Gwendoline Sarry, Sophie Perinel-Ragey, Jean-Michel Vergnon, Anthony Clotagatide, Nathalie Prévôt
A new trend emerging in the ENDS users (called “vapers”) community consists of using variable voltage/wattage ENDS associated with regulated mods (i.e., modified parts in the frame of the concept of rebuildable atomizers) to apply high energy. Recently, a study underlined specific features when “vaping” at high voltage (Farsalinos et al. 2016). High-power ENDS can deliver high levels of aerosol nicotine (Farsalinos et al. 2016). This newer technology of ENDS can generate at high voltage aerosol nicotine in a much wider range of concentrations (2.72–10.61 mg of nicotine/20 puffs) than older ENDS devices using cartomizers (1.01–3.01 mg of nicotine/20 puffs) but also tobacco cigarettes (1.76–2.20 mg of nicotine/cigarette). Thus, high-power ENDS could be a promising technology to raise nicotine absorption and plasma nicotine levels. To relate exposure to biological effects (such as nicotine absorption), it is crucial to assess the deposition pattern of inhaled particles (Pichelstorfer et al. 2016). Many parameters are needed (e.g., aerodynamic diameter, composition of the particles, composition of the vapor phase, parameters of the mixture such as vapor pressure, surface tension, activity coefficient, etc.) to obtain a proper description of the deposition of the dynamic aerosols in the respiratory tract. In particular, the accurate determination of the particle size distribution is essential to predict aerosol deposition (Sosnowski and Kramek-Romanowska 2016). However, aerodynamic features of the aerosol generated by high-power ENDS remain poorly known. Against this background, this work describes the impact of power level and refill liquid composition on aerosol features generated by recent high-power ENDS. Aerosol features were assessed in terms of Mass Median Aerodynamic Diameter (MMAD), Count Median Aerodynamic Diameter (CMAD), and aerosol output (i.e., the mass of airborne refill liquid per volume of aerosol generated by the ENDS). The purpose of this work is to remedy the lack of studies addressing: The impact of the aerosol dilution ratio (from 0 to 6) prior to particle size distribution measurement.The effects of two propylene glycol (PG)/vegetable glycerin (VG) ratios (80% + 20% vs. 20% + 80%) on particle size distribution and aerosol output.The influence of the power level of the battery (from 7 W to 22 W) on particle size distribution and aerosol output.