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At least 19 recordsLinked to original sources
PubMed1996

[A study on the control of air toxic chemicals in workplace for bakelite manufacturing and casting].

Air concentrations of phenol, formaldehyde and ammonia related to the contents of free phenol, formaldehyde in raw material, and solidifying agent-urotropine in bakelite. Due to the solubility of phenol and formaldehyde, in the manufacture process, water was added to lower contents of phenol and formaldehyde in bakelite, and content of urotropine was reduced in bakelite sand presceription to lower air concentrations of phenol, formaldehyde and ammonia. As contents of phenol and formaldehyde in bakelite reduced to 4.9% and 0.037% from 6.32% and 0.062%, respectively, air concentrations of phenol, formaldehyde and ammonia lowered to 0.61 mg/m3, 0.69 mg/m3, and 5.1 mg/m3 from 2.94 mg/m3, 1.72 mg/m3, and 12.9 mg/m3, respectively, and incidence rate of skin disease in the employees of the workplace decreased to zero from 80.2%. It is recommended that a hygienic standard for allowable concentration of mixed toxic chemicals in the workplace air for bakelite manufacturing be formulated as soon as possible.

Air Pollutants, Occupational↗
PubMed2005

Occupational exposure to airborne asbestos from phenolic molding material (Bakelite) during sanding, drilling, and related activities.

In this study, a historical phenolic (Bakelite) molding material, BMMA-5353, was tested to determine the airborne concentrations of asbestos fibers released during four different activities (sawing, sanding, drilling, and cleanup of dust generated from these activities). Each activity was performed for 30 min, often in triplicate. The primary objective for testing BMMA-5353 was to quantitatively determine the airborne concentration of asbestos fibers, if any, in the breathing zone of workers. Uses of this product typically did not include sawing or sanding, but it may have been drilled occasionally. For this reason, only small quantities were sawed, sanded, and drilled in this simulation study. Personal (n = 40), area (n = 80), and background/clearance (n = 88) air samples were collected during each activity and analyzed for total fiber concentrations using phase contrast microscopy (PCM) and, for asbestos fiber counts, transmission electron microscopy (TEM). The raw PCM-total fiber concentrations were adjusted based on TEM analyses that reported the fraction of asbestos fibers, to derive a PCM-asbestos concentration that would enable calculation of an 8-hour time-weighted average (TWA). The estimated 8-hour TWAs ranged from 0.006 to 0.08 fibers per cubic centimeter using a variety of worker exposure scenarios. Therefore, assuming an exposure scenario in which a worker uses power tools to cut and sand products molded from BMMA-5353 and similar products in the manner evaluated in this study, airborne asbestos concentrations should not exceed current or historical occupational exposure limits.

Asbestos↗
PubMed2002

[Extraction and gas chromatographic analysis of residual trimethylamine(TMA) in the bakelite-type macromolecule complex material].

A method for the determination of residual TMA in the bakelite-type macromolecule complex material has been established. The whole process includes sample pretreatment, TMA extraction and GC analysis. After the samples have been pretreated, the TMA in them was extracted at (38 +/- 2) degrees C for 16 hours. Then the content of TMA in the liquid can be determined directly. From the experimental results we can conclude that the whole method is cheap, simple and accurate. It meets the requirement of microanalysis and can be used to determine real samples.

Air Pollutants↗
PubMedDate not supplied

Can the AAPM Task Group 21 protocol lead to optimum ion chamber designs?

The recently published AAPM Task Group 21 protocol for high-energy dosimetry is complicated in that it requires the physicist to obtain the values of about a dozen different physical variables by looking them up in tables or graphs. This should be compared with the procedure of earlier protocols using the concept of a single multiplier C lambda. We have investigated how the physical principles outlined in the improved AAPM protocol could be utilized for the redesign of the therapy-level ion chambers in such a way that one can reduce the number of factors that need to be looked up in tables or graphs for the calibration of high-energy teletherapy photon beams. In our analysis presented in this paper we found that one such design could be for an ion chamber having a wall acrylic or Bakelite of a thickness not exceeding 0.1 g/cm2 and having an inner diameter of 6 mm, and used in conjunction with a cobalt-60 buildup cap of thickness 0.35 g/cm2 made of acrylic, Bakelite, or Tufnol. If a chamber of such a design is used in a water phantom, the dosimetry practically reduces to the simplicity of the former protocols of depending on a single value of energy-dependent multiplier to be obtained from a table. With the above design parameters, it becomes possible to eliminate the explicit need to incorporate the factors Pwall, Prepl, Awall, beta wall, and the variable alpha, representing the fraction of ionization due to electrons from the wall material of the chamber.

Animals↗