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Biomedical subjects

P J Middendorf

Publications and source records attributed to P J Middendorf.

8 recordsLinked to original sources
PubMed1984

Kidney dialysis: ambient formaldehyde levels.

Ambient levels of formaldehyde in kidney dialysis units were discussed. Five kidney dialysis clinics were surveyed and air sampling was performed in all major work areas. Formaldehyde levels were found to be below the TLV of 1.0 part per million (ppm) in all samples and the mean ambient level was below 0.5 ppm. Feasible engineering controls that would further reduce or eliminate potential employee exposures were identified.

Air Pollutants, Occupational↗
PubMed1983

Noise exposure: action level criteria as a predictor of permissible exposure level criteria.

The adoption of the OSHA noise amendment has made it necessary to make two different noise exposure measurements. These are the employee's exposure with reference to the action level criteria, which requires a threshold of 80 dBA, and the employee's exposure with reference to the permissible exposure limit, which employs a 90 dBA threshold. In addition to the time constraints involved in measuring employee exposure in relation to two different thresholds, many organizations will not have access to equipment capable of performing these separate tasks simultaneously. Based on 242 simultaneous exposure measurements of both the action level and the permissible exposure level criteria, this paper describes a method which uses one noise exposure criteria measurement to predict an employee's exposure at the other.

Humans↗
PubMedDate not supplied

Evaluation and field calibration of the Miniram PDM-3 aerosol monitor for measuring respirable and total coal dust.

The MIE Miniram PDM-3 is a real-time aerosol dust monitor designed to measure dust based on Mie scattering. It has an optional in-line filter that, when attached to a constant flow air sampling pump, allows a gravimetric air sample to be collected from the same air stream that passes through the Miniram sensing chamber. This study compared real-time Miniram digital respirable and total dust readings with concentrations from an in-line 5 microns polyvinyl chloride filter connected to a constant flow pump and with results from traditional respirable and total dust samples. Area samples were collected at three coal-fired power generating facilities over a 2-month period. Traditional respirable dust concentrations ranged from 0.04 to 10.8 mg/m3. In the monitored range of concentrations the Miniram respirable concentrations and the in-line respirable dust concentrations were not significantly different (p > or = 0.05), nor were the Miniram in-line filter concentrations and the side-by-side respirable dust concentrations significantly different (p > or = 0.05). However, the Miniram respirable concentrations and the traditional respirable concentrations were significantly different (p = 0.02). The Statistical Analysis System (SAS) procedure CALIS, which meets the statistical requirements for developing calibration lines for two variables each measured with error, is used to develop field calibration curves for the comparisons between direct-reading instrument concentrations and concentrations from traditional National Institute for Occupational Safety and Health methods for total and respirable dust.

Aerosols↗
PubMedDate not supplied

Performance of electronic flow rate meters used for calibration of air sampling pumps.

Electronic flow rate meters (EFRMs) have been used by industrial hygienists for more than 20 years and are useful because they reduce the time required to calibrate air sampling pumps. This study compared the variability of the traditional bubble burette meter with electronic flow meters and simultaneously compared several EFRMs under different calibration conditions. The flow rates of air sampling pumps were set using a standard bubble burette meter at flow rates of 2 or 50 mL/min using two pressure drops, 2 inches water and 10 inches water. Four airflow rate meters (Bios DryCal, A.P. Buck mini-Buck, MSA Accuflow, and Sensidyne Gilibrator) were concurrently compared at each of the pump flow rate and pressure drop combinations. Results indicated that the standard bubble burette method is more variable than the EFRMs and that the flow rates given by the EFRMs were significantly different (p<0.0001) at both the high and low flow rates. Although the calibrators gave significantly different flow rates, the difference was within the acceptable air sampling pump error of +/- 5%.

Air Pollution↗
PubMedDate not supplied

Occupational exposure to nitrous oxide in dental operatories.

Occupational exposures to nitrous oxide (N(2)0) were measured in numerous dental operatories. In all cases, the National Institute of Occupational Safety and Health (NIOSH) recommended time-weighted average (for one operation) of 25 ppm was exceeded by wide margins (NIOSH considers 50 ppm to be attainable in dental operatories). However, a new risk assessment is necessary to determine appropriate exposure limits. Many of the operatories were not equipped with scavenging systems and none of them used a scavenging device in combination with a local exhaust ventilation system. Scavenging devices and local exhaust ventilation should be used to control nitrous oxide exposures. Leaks in N(2)0 delivery systems, which were found to be commonplace, should also be controlled. Research and development efforts are needed to improve upon the already existing scavenging devices, and provision for local exhaust ventilation needs to be included in the design of dental operatories.

Air Pollutants, Occupational↗
PubMedDate not supplied

Control of nitrous oxide exposures in dental operatories using local exhaust ventilation: a pilot study.

An experimental portable local exhaust ventilation system was installed in three dental operatories where nitrous oxide was used routinely. Standard methods of exhaust ventilation design used in industry to control exposures to toxic airborne substances were applied to the dental operatory setting. The concentration of nitrous oxide in the dentists' breathing zones was measured before and after installation to determine the efficiency of the system in reducing occupational exposures. Results indicate that placement of the exhaust opening and exhaust air flow rate are important in determining the degree of control achieved. After the system had been installed in one operatory, peak exposures declined from over 600 parts per million (ppm) to less than 70 ppm: the time-weighted average exposure was below the NIOSH recommended level of 25 ppm. A permanently installed local exhaust ventilation system modeled after the portable one used in this pilot study may be feasible for most operatories and should not interfere with dental procedures. The results suggest that nitrous oxide exposures can be greatly reduced if dental operatories are equipped with local exhaust ventilation.

Air Pollutants, Occupational↗
PubMedDate not supplied

Formaldehyde vaporization in the hatcher and the effect on tracheal epithelium of the chick.

Chicken embryos were exposed to formaldehyde vapors in the hatcher during the final 3 days of incubation. Measured formaldehyde levels approached 130 ppm. Tracheas collected at hatch and 5 days post-hatch were evaluated for functional and morphologic changes. Tracheal cilia motility was reduced in formaldehyde-exposed chicks. Scanning electron microscopy revealed blunted cilia and blebs occurring in the cilia surfaces. At 5 days of age, excessive tracheal mucus was present. Sloughing of the tracheal epithelium was visible by light microscopy.

Analysis of Variance↗