A Simple and Disposable Sampler for Inhalable Aerosol

The state-of-the-art for personal sampling for inhalable aerosol hazards is constrained by issues of sampler cost and complexity; these issues have limited the adoption and use of some samplers by practicing hygienists. Thus, despite the known health effects of inhalable aerosol hazards, personal exposures are routinely assessed for only a small fraction of the at-risk workforce. To address the limitations of current technologies for inhalable aerosol sampling, a disposable inhalable aerosol sampler was developed and evaluated in the laboratory. The new sampler is designed to be less expensive and simpler to use than existing technologies. The sampler incorporates a lightweight internal capsule fused to the sampling filter. This capsule-filter assembly allows for the inclusion of particles deposited on the internal walls and inlet, thus minimizing the need to wash or wipe the interior sampling cassette when conducting gravimetric analyses. Sampling efficiency and wall losses were tested in a low-velocity wind tunnel with particles ranging from 9.5 to 89.5 μm. The results were compared to the proposed low-velocity inhalability criterion as well as published data on the IOM sampler. Filter weight stability and time-to-equilibrium were evaluated as these factors affect the practicality of a design. Preliminary testing of the new sampler showed good agreement with both the IOM and the proposed low-velocity inhalability curve. The capsule and filter assemblies reached equilibrium within 25h of manufacturing when conditioned at elevated temperatures. After reaching equilibrium, the capsule-filter assemblies were stable within 0.01mg.

Endotoxin deposits on the inner surfaces of closed-face cassettes during bioaerosol sampling: a field investigation at composting facilities

A set of 270 bioaerosol samples was taken from 15 composting facilities using polystyrene closed-face filter cassettes (CFCs). The objective was to measure the quantity of endotoxin deposits on the inner surfaces of the cassettes (sometimes referred to as 'wall deposits'). The results show that endotoxins are deposited on the inner surfaces of the CFCs through sampling and/or handling of samples. The quantity of endotoxins measured on inner surfaces range between 0.05 (the limit of detection of the method) and 3100 endotoxin units per cassette. The deposits can represent a large and variable percentage of the endotoxins sampled. More than a third of the samples presented a percentage of inner surface deposits >40% of the total quantity of endotoxins collected (filter + inner surfaces). Omitting these inner surface deposits in the analytical process lead to measurement errors relative to sampling all particles entering the CFC sampler, corresponding to a developing consensus on matching the inhalable particulate sampling convention. The result would be underestimated exposures and could affect the decision as to whether or not a result is acceptable in comparison to airborne concentration limits defined in terms of the inhalability convention. The results of this study suggest including the endotoxins deposited on the inner surfaces of CFCs during analysis. Further researches are necessary to investigate endotoxin deposits on the inner cassette surfaces in other working sectors.

Some Ultrastructural Changes Induced in Resistant and Susceptible Soybean Roots Following Infection by Rotylenchulus reniformis

A developmental electron microscopic study of the parasitism of Rolylenchulus reniforrnis in resistant 'Peking' and susceptible 'Lee' soybeans was made during a 21-day period under controlled conditions. Within 2 days of inoculation, the nematode had penetrated the cortical cells to the endodermis where it inserted its stylet, secreted and initiated syncytial formation and cell hypertrophy. Syncytia primarily involved pericycle tissues and, to a lesser extent, xylem parenchyma and endodermis. When identifiable, the cell into which the nematode stylet was inserted to initiate syncytial development was endodermal. Susceptible tissues exhibited two basic phases of development during this infection period: (i) an initial phase represented by partial cell wail lysis and separation; and (ii) an anabolic phase, characterized by organelle proliferation and development accompanied by secondary wall deposits, which provided nutrition for sessile female development. The resistant or hypersensitive reaction (HR) lacked the anabolic phase found in the susceptible reaction, and was characterized by an extension and usually accelerated type of Iysis found in the first phase of the syncytial development. The HR was usually very evident 4 days after inoculation, and could be identified by an almost complete lysis of the cell walls and cytoplasm. The possibility that the initial cell of the developing syncytium or "prosyncyte" may influence a susceptible or resistant reaction is discussed. Successive stages of cell wall dissolution and the deposition of secondary cell walls are described.