Asthma in the Workplace PDF

Preface

Interest in occupationally induced lung diseases has been focused chiefly on dust-induced disorders since the earliest description of miners' lung disease by both Agricola and Paracelsus in the middle of the 16th century. It is therefore not surprising that contemporary textbooks of occupational lung disease have emphasized ailments that, until recently, were very common in industrialized countries and could be detected by progressive radiological changes, permanent loss of pulmonary function, and unique structural histological characteristics. In industrialized countries, the ‘‘picture'' has changed in recent years with the significant reduction in dustinduced lung diseases (e.g., silicosis, asbestosis) because of efficient environmental control. However, the effect of asbestos exposure can still be seen from the steady increase in mesothelioma and bronchial carcinoma. On the other hand, the frequency of occupational asthma has increased with a recent plateau and is now the most prevalent occupational lung disease in these countries (see Chapter 14). Although occupational asthma was recognized as early as the 18th century by Ramazzini, its importance as a significant hazard in the workplace was not widely appreciated until the spurt in industrial technology after World War II. The literature concerning workplace asthma has steadily increased since the great impetus given by Professor Jack Pepys, who can be considered the father of occupational asthma and to whom this book is dedicated. Specialists have recognized that asthma may now be one of the most common work-related respiratory diseases. Recent journal reviews, book chapters, monographs, and Web sites also document the proliferation in the number of specific causes of occupational asthma.

Asthma in the workplace is a complex entity that is not equivalent to new onset occupational asthma as defined in the first chapter of the book. The chapter on definitions (Chapter 1) has been revised to account for the fact that approximately 10% of asthmatic subjects note that the workplace worsens their asthma symptoms. A proportion develop new onset occupational asthma, defined as ‘‘asthma caused by the workplace,'' whereas many others are affected by work-exacerbated asthma. The diagnosis of occupational asthma is often difficult because of multiple causality in many occupational environments, the variability of symptoms and patterns of latephase asthmatic reactions, the requirements for special diagnostic procedures, and the unpredictability of onset and persistence of symptoms. Outbreaks of occupational asthma in specific work settings are ideal, mini-epidemiological paradigms of nonoccupational asthma. Such outbreaks provide excellent opportunities for investigating the source, the characteristics of the emission-dispersion cycles, and the health impact of inciting agents. Environmental sampling for monitoring the concentration of both chemicals and proteins is available in many occupational situations where work-related asthma has occurred (see Chapters 11-13). The ready access to such integrated data in a defined setting provides an ideal milieu and investigational model for further advancement of knowledge about the pathophysiological pathways and natural history of asthma.

These expanded opportunities have attracted the collaborative interests of allergists, immunologists, pulmonologists, immunotoxicologists, occupational health specialists, aerosol scientists, hygienists, and epidemiologists. In addition, the economic and social hardships imposed on workers who have refractory symptoms associated with occupational asthma require consultation with medicolegal experts. These interactions have clearly established that the features of occupational asthma are unique and often at odds with medical dogma derived from the surveillance, diagnosis, and prevention of mineral dust-induced lung disorders. Combined with the recent upsurge of scientific interest and literature in the pathophysiology of asthma in the general population, these considerations convinced us that a textbook dealing with occupational asthma was overdue. The enthusiastic response to publication of the first and second editions and the number of literature citations attributed to it have more than justified preparation of a third edition.

As is the case with most new fields of health-related expertise, discovery and research in workplace-related asthma have continued at a rapid pace and have served as the impetus for this updated and revised edition. In addition, coverage of several specific areas of interest that had not yet clearly evolved prior to publication of the first and second editions has been either added or expanded.

Because new advances in workplace-related asthma are international in scope, the coalition of editors and individual contributors in this book is a reflection of this orientation. The common goal of this cooperative effort was to prepare an authoritative, educational resource for primary care physicians, occupational health specialists, allergists, and pulmonologists. A reference book of this type was considered particularly germane for primary care providers because current mandates for early detection and reporting of occupational asthma require that these physicians develop skills that lead to early recognition of this disease. To this end, special emphasis has been given to an algorithm of clinical diagnosis, immunological evaluation, and physiological methods of evaluation (see Chapters 7-10) as a practical guide for primary care physicians. Special chapters on medicolegal aspects, compensation, assessment of disability, prevention, and surveillance (Chapters 14 and 15) address the social outcomes of workers disabled by asthma and should serve as useful reference sources for occupational health physicians, workers' compensation administrators, private insurers, attorneys, adjudicators, and legislators. The chapters concerning epidemiology and disease entities have been prepared to provide sufficient in-depth information for occupational health and other medical subspecialists primarily concerned with asthma in the workplace. Although occupational asthma represents the core of this book, this third edition includes new chapters on asthma exacerbated at work and asthma-like syndromes, with all conditions being grouped under the general theme of ‘‘asthma in the workplace.'' Conditions that share clinical, functional, or immunological features to workplace asthma (chronic obstructive pulmonary disease due to occupational exposure, hypersensivity pneumonitis, building-related illnesses) are covered in specific chapters (Chapters 28-30). The relationship of conditions frequently associated with workplace asthma is reviewed in Chapters 31 and 32 (‘‘Upper Airways Involvement'' and ‘‘Occupational Urticaria'').

Part I, ‘‘General Considerations,'' contains chapters on definitions, historical background, epidemiology, genetics, pathophysiology, and animal models.

Part II, ‘‘Assessment and Management,'' includes chapters that delineate the basic guidelines for clinical and objective evaluation, environmental monitoring, and prevention of occupational asthma. Medicolegal aspects and surveillance strategies are also discussed in this section.

Part III, ‘‘Specific Agents Causing Occupational Asthma with a Latency Period,'' provides detailed information about specific agents (including a variety of high- and low-molecular-weight agents) that induce asthma or asthma-like diseases.

Part IV, ‘‘Specific Disease Entities and Variants,'' covers other types of workrelated asthma conditions, e.g., irritant-induced asthma, asthma exacerbated at work and asthma-like syndromes. Chronic airflow obstruction due to occupational exposure, hypersensitivity pneumonitis, and building-related illnesses are also covered in this part of the book.

The book also contains a compendium, in particular a table that lists the major protein and chemical inducers of occupational asthma, the type of workplaces or occupations in which these occur, pertinent immunological and physiological evidence, and key literature references.

In a sense, the preparation of individual chapters by multiple authors and the endeavor that the authors have put forth in this third edition is similar to meta-analyses that compare different published health-related data pertaining to a given research question. As often occurs with meta-analyses, agreement at times is incomplete. Above all, the authors and editors have attempted to balance opposing views as objectively as possible. In most cases, this balancing process was successful in arriving at editorial consensus. Where this was not possible, the data appear with the caveat that a controversy exists and resolution is not possible, because definitive data are either not yet available or under investigation. These critical assessments have been rewarding educational experiences for the editors and authors. We hope that this joint effort will not only provide pragmatic information for current clinical applications, but also serve as a foundation for significant new research information that will most assuredly advance the discipline during this new millennium.