Elsevier

Human Pathology

Volume 39, Issue 3, March 2008, Pages 307-315
Human Pathology

Perspectives in pathology
Twenty-five years of fiber analysis: what have we learned?

https://doi.org/10.1016/j.humpath.2007.07.005Get rights and content

Summary

Asbestos exposure has resulted in a variety of diseases, including asbestosis, carcinoma of the lung (LC), pleural plaques, and malignant mesothelioma (MM). We hypothesized that there have been significant changes in the mineral fiber content of lung tissue from individuals with these diseases over the past 25 years. Asbestos content was measured in lung tissue samples from 819 individuals using light microscopy (to measure asbestos body concentrations) and scanning electron microscopy (to measure types and concentrations of mineral fibers). Cases were divided chronologically according to those occurring in the first half (group 1) versus those occurring in the second half (group 2). The study included 419 cases of MM, 206 cases of asbestosis, and 340 cases of LC. The median asbestos body count (in asbestos bodies per gram) decreased from group 1 to group 2 for each disease: MM, 480 to 350; asbestosis, 24 700 to 19 200; and LC, 1600 to 174 (reference range, 0-20). A similar trend was observed for fiber counts by scanning electron microscopy. Amosite was the most frequently detected asbestos fiber type and decreased in frequency of detection and median concentration from group 1 to group 2. Crocidolite showed an increased detection frequency from group 1 to group 2 across all 3 disease categories. The decrease in asbestos body and amosite concentrations over time is consistent with the banning of asbestos from insulation products in 1972. The source for the increased detection of crocidolite was not identified and needs further investigation.

Introduction

Asbestos has resulted in a variety of benign and malignant disorders among exposed individuals, including asbestosis, carcinoma of the lung (LC), parietal pleural plaques (PPP), and malignant mesothelioma (MM) of the pleura and peritoneum [1], [2], [3]. Analysis of the mineral fiber content of lung samples has provided useful information for understanding the relationship between asbestos exposure and the various asbestos-related diseases [4], [5]. Since the establishment of a permissible exposure level in the workplace by the Occupational Safety and Health Administration in 1972, there have been progressively stringent standards for work place exposure, from 5 fibers per milliliter in 1972 to 0.1 fiber per milliliter in 1993 [6]. We hypothesized that the effect of these regulations upon workplace exposures would be reflected in changes in lung fiber burdens in the various asbestos-related diseases over time.

We have had the opportunity over the past 25 years to study in one laboratory using a single methodology more than 800 individual cases of mesothelioma, asbestosis, and lung cancer. Because of the litigious nature of asbestos-related diseases, most of these cases (approximately 60%) have come from medical-legal referrals. The purpose of the present study is to investigate trends in fiber type and concentrations over time by disease category and to correlate these findings with demographic data and information regarding occupational or paraoccupational exposure. The authors are not aware of similar studies of temporal trends of asbestos fiber content in the medical literature.

Section snippets

Materials and methods

The database included more than 1000 cases for which lung fiber burden analysis had been performed between August 1980 and August 2005. Among these were 421 cases of MM, 340 cases of LC, and 206 cases of asbestosis. Fifty-four of the asbestosis cases also had mesothelioma, and 91 had lung cancer (hence, there is overlap between the asbestosis category and the other two). Each of these diagnostic categories was then arranged chronologically so that the first half comprised group 1 and the second

Results

Exposure information was available in 679 cases (Table 1). Shipbuilding and insulation dominated the industries associated with these 3 asbestos-related diseases, although there was a noticeable decline in the contribution from insulators and shipyard workers from group 1 to group 2. More cases were observed in the molten metal (steel mill, aluminum refinery, iron foundry) and construction industries in group 2 than in group 1. Pipe fitters/welders dominated the occupational categories, and

Discussion

The present study involves a large database of cases for which lung fiber burden analyses were performed by one laboratory over two and a half decades. The main finding of our study is that there has been a decrease in asbestos content over time for a variety of asbestos parameters and across all disease categories. Amosite is the most frequently detected fiber type in all 3 disease categories, and the concentration and frequency of detection of this fiber type have decreased over time. This

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