Howard E. Ayer

The interrelationships of selected asbestos exposure indices.

Based on the assumption that the biological effect of asbestos is related to the concentration of respirable fibers, an index was developed which yields the concentration in numbers of asbestos fibers visible under 430 X phase-contrast illumination. Data are presented relating this index to overall dustiness as measured by impinger counts and to absolute fiber concentration and distribution as measured by electron microscopy. The relation between count estimates and gravimetric measures of total dust and chrysotile asbestos deduced from magnesium analyses are given for gross and respirable samples. These relations are developed for use in operations in the manufacture of asbestos textile, friction, cement, and insulation products. The most convenient, practical, and direct index of asbestos fiber exposure proved to be the concentration of fibers longer than 5 microns counted on membrane filters at 430 X phase-contrast illumination.

Measurement of Dust Exposures in the Asbestos Textile Industry

Abstract Data obtained from environmental surveys of nine asbestos textile mills, which represent the baseline for the textile segment of the Public Health Service epidemiological study of asbestos processing industries, are presented. From these data concentration ranges are derived which yield significant differences between typical sample groups. Variance ratio tests of different methods of counting and analysis were made and count weight ratios based on magnesium analyses for asbestos were calculated.

The proposed ACGIH mass limits for quartz: review and evaluation.

Abstract Dust measurements should give results related closely to the health hazard, be simple, reproducible, and inexpensive. Measurement of total airborne mass concentration or, preferably, respirable mass concentration is simpler, cheaper and gives more reproducible results than the impinger. Comparative sampling indicates that a respirable dust limit of 10/(% Respirable Quartz + 2) mg/m3 would be equivalent to the present impinger TLV. A total dust limit proposed is: 30/(% Quartz + 2) mg/m3. Either mass limit permits personal sampling techniques to be used. Quartz analyses are made on the respirable fraction for the respirable limit, and on total dust for the total dust limit. Until safety of present quartz limits is demonstrated, the limits should be used conservatively.

Size-selective gravimetric sampling in dusty industries.

Abstract Size-selective gravimetric sampling was conducted along with sampling by impinger for dust in 22 foundries. Three-hour personal samples were taken with a 10-mm cyclone to remove nonrespirable dust, and with a polyvinyl chloride membrane filter to collect a dust sample for weighing. Respirable free silica was determined on samples passing a horizontal elutriator. The evaluation of the potential silicosis hazard by a gravimetric limit was not inconsistent with judgment of the hazard based on impinger samples and the present ACGIH Threshold Limit Value. Size-selective gravimetric sampling is recommended as an alternative to impinger sampling.

Exposure to fibers in the manufacture of fibrous glass.

Abstract As part of its study of health hazards associated with the manufacture and processing of fibrous materials, the Bureau of Occupational Safety and Health is conducting a cohort analysis of past workers in the fibrous glass industry. Environmental surveys to estimate the degree of exposure of fibrous glass workers to fibers that are respirable indicated that the exposure had been negligible. Present average concentrations of fibers in air are low, as is the total airborne glass concentration. Concentration ranges and averages in glass fiber insulation and glass textile fiber manufacturing are compared with those existing in other mineral industries for potential health implications.

Sampling Methods for Oil Mist in Industry

Abstract Satisfactory reproducibility, sensitivity and efficiency were found in samples for oil mist concentration taken by either the electrostatic precipitator or by glass fiber filters. Membrane filters and standard laboratory filter papers were unsuitable. Determination of size frequency distributions by stage weights from a commercial cascade impactor gave most promise as a routine field sampling method; membrane filter sheet was used on the impactor slides as a collecting reservoir. Microscopic methods for size frequency distribution were more tedious and the collection of suitable samples was more difficult. Light scattering photometers give the most convenient and accurate size frequency distribution where concentration is not too high.

Association of Disability and Selected Occupational Hazards

Subjective evaluations by a panel of industrial hygienists were used to classify occupational groups by degree of exposure to airborne particulates, irritant gases, organic vapors, and temperature extremes. These were compared with grouped proportionate morbidity ratios for the occupations for each of 75 disease conditions, using disability awards made by the Social Security Administration. Chi-square tests of the resulting tables showed a number of significant differences. The most important of these appeared to be a strong association of particulate exposure and excess disability from emphysema. No such association was found for particulate exposure and excess disability from lung cancer.

Some Observations of Noise at Airports and in the Surrounding Community

Abstract Results of noise surveys performed at two major airports are presented, including (a) measurement of operational noise in the working areas and evaluation of potential danger to hearing, (b) audiometric data from airport employees, and (c) determination of noise in nearby residential areas. Potentially harmful noise levels were found at ground run-up, taxi, and take-off operations and in the area of engine test-cell facilities. Both jet and propeller aircraft produced annoyance noise levels in the residential areas, with jet noise being the greater problem.