Jeremiah R. Lynch

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.

A rationale and framework for establishing the quality of human exposure assessments

Exposure assessments, performed as input to an evaluation of potential human health risk, are an element of risk assessment. Risk assessment results feed governmental and corporate risk management decisions, which seek to balance the estimated potential human health risks with other factors. Risk managers presume that the risk information provided to them is scientifically valid and accurate. Government agencies have begun to apply a system known as good laboratory practices (GLP) to ensure adequate data quality on animal studies, which are often the first step in the health-effects evaluation of risk assessment. This paper explores a rationale and framework for establishing the quality of human exposure assessments and proposes a set of good exposure assessment practices (GEAP). The components of the proposed GEAP include the writing of a study protocol before conducting the study, consideration of available resources, specification of an exposure model, a study design (including sampling and analytical methods and data analysis), quality assurance, archiving, communications, and a statement of overall uncertainty in exposure estimates. The GEAP concept is offered as a starting point for developing a consensus among the community of exposure assessors regarding a minimum standard for good practices. If a consensus on GEAP can be reached and applied, exposure assessments would have improved scientific bases, interpretability, and utility.

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.

Characterization and Solubility of Metals Associated with Asbestos Fibers

Abstract A series of uniform samples representing blends from different sources and types of asbestos were analyzed for nickel, chromium, cobalt and manganese. The bulk samples and the less than 10-micron size fractions were analyzed separately. The metals soluble in bovine serum were determined for the less than 10-micron fractions. Free silica content was also determined. The degree of solubility of the same metal varied considerably by source and type of asbestos. Chrysotile had greater amounts of nickel and chromium whereas Amosite was higher in manganese. Crocidalite had the lowest metal content.

Exposure to Metals in the Manufacture of Asbestos Textile Products

Abstract Asbestos textile workers processing chrysotile were exposed, in the past, to significant airborne levels of nickel, chromium, and manganese. Limited studies indicate that other metals were also involved. It is likely that the phenomenon shown in asbestos textile manufacturing is also true in other asbestos mining, milling, and processing operations. Sufficient evidence is presented in this study to indicate that the role of metals in the etiology of disease associated with asbestos inhalation should not be ignored. It is no longer tenable to look only for asbestos fibers or bodies in biological tissue and by their presence assume a cause and effect relationship with the disease.

Source and Identification of Respirable Fibers

Abstract Fibrous bodies with an iron-containing coating have been found in the lungs of persons coming to autopsy in a number of urban hospitals, the number of fibrous bodies varying greatly with approximately 4 to 6% of the persons examined showing numerous bodies. Because these findings raise questions with regard to the possibility that asbestos is a factor in increased lung cancer, questions concerning the nature, source, and significance of these bodies are discussed in the light of research needed to find answers.

An industrial hygiene methodology developed in support of a retrospective morbidity case-control study.

An industrial hygiene methodology that was developed in support of an epidemiologic case-control study is described. This study was conducted to investigate a potentially increased incidence of colorectal cancer among employees who worked at a unit that manufactured polypropylene by a heavy diluent process. Retrospective epidemiologic case-control studies typically have exposure assessment problems because industrial hygiene monitoring data are often not available. Misleading job titles are another problem that can provide a poor framework for estimating exposures. In addition, a job title-based exposure assessment assumes individual work patterns are not important in assessing worker exposures, although this is contradictory to industrial hygiene experience. The design of the case-control study provided an innovative industrial hygiene approach to circumvent these typical exposure estimating problems. The industrial hygiene methodology of the case-control study included assessing historical exposures, developing an exposure estimating matrix, selecting candidate etiologic agents based on a joint toxicologic and industrial hygiene review, administering a work activity questionnaire, calculating exposure scores, and conducting a statistical analysis. The study design also provided an additional exposure measurement independent of the toxicologic and industrial hygiene review. This provided an opportunity to compare the likelihood of exposure misclassification and, as expected, showed that a more detailed exposure estimate resulted in less misclassification.

Evaluation of Size-Selective Presamplers: I. Theoretical Cyclone and Elutriator Relationships

Relationships of airborne dust concentrations measured by cyclone and elutriator size-selective presamplers are presented. Cyclone efficiency is assumed to fallow the Los Alamos criterion, and that of the elutriator the British Medical Research Council criterion. Cyclone-elutriator ratios are given for log-normally distributed aerosols with a count median diameter range of 0.1 to 11.0 microns and a mass median diameter range of 0.2 to 16 microns for geometric standard deviations of 1.1 to 3.0. For usual heterogeneous industrial dust clouds, the ratio is 0.81 ± 0.11. For these same dust clouds the cyclone passes from 2% to 75% of the total dust, and the elutriator from 4% to 81%.

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.

Techniques for the Detection, Identification and Analysis of Fibers

Applicability and limitations of the techniques used for the detection, identification, and analysis of mineral fibers are discussed with particular emphasis as to the problem of evaluating health hazards resulting from exposure to fibers and the discovery of the mechanisms of the diseases involved.