Preventing Illness and Injury in the Workplace

3. Health Hazard Identification 42, 42 43 45 45 48 49 52 52 54 . 62 . 63 TABLES 3-1. The Ten Leading Work-Related Diseases and Injuries: united States, 1982 . 43 3-2. some Occupational cancer Hazards . 46 3-3. Neurologic Effects of Occupational Toxins . 50 3-4. Substances for Which NIOSH Has Recommended Exposure Limits to Prevent Skin Disorders ● . 51 3-5. Workplace Agents That Induce skin Disorders . 51 3-6. Industries at Highest Risk for occupational Skin Diseases 52 3-7. General Classification of Tests Available to Determine Properties Related to Carcinogenicity. 56. 3-8. Advantages and Disadvantages of Case-Control and Cohort Studies . 59 Health Hazard Identification Since work occupies a central place in most Traditionally, physicians and groups of work- lives, it is not surprising that it is related to many ers have been the sources of information leading afflictions, nor that in one form or another it con- to the association of particular hazards with dis- tributes to diseases of every system of the body. ease. “Factory fever” (typhus), “mad hatters” (vic- tims of mercury poisoning), and “wrist drop” (lead Some diseases are relatively easily linked to poisoning) were related to workplace exposures workplace conditions, either because the diseases through observation. Recent years have seen in- themselves are distinct or relatively rare, or be- creasing importance being given to epidemiology— cause the particular workplace conditions differ the study of the distribution of diseases—and greatly from ordinary conditions of daily life. toxicology— the study of the dangerous proper- Other diseases are associated with either the work- ties of substances—in identifying workplace place or other activities, or with both; pinning hazards. down causes and preventive strategies of those diseases is more complicated. Case reports from doctors, workers, and em- Occupational diseases have been recognized for ployers can be valuable sources of information centuries, although definitions of disease and ill on hazards and serve to generate hypotheses for health have changed over time. Society—less will- larger studies. But inadequacies in the training of ing to accept adverse effects of any kind and physicians, both those who practice occupational knowing that much disease is preventable—no medicine and those in general practice, limit iden- longer believes poor health to be a necessary con- tification hazards through case reports. comitant of work. Epidemiology relies on observations or sugges- While attention often focuses on new hazards, tions of possible associations between exposures and in identifying and preventing more subtle, or behaviors and disease for hypothesis genera- previously unnoticed effects, professionals in oc- tion. It has limitations in the kinds and magni- cupational safety and health also continue to deal tudes of effects it can detect, but it can provide with many cases of well-known occupational dis- the most convincing evidence of associations be- eases. The still-frequent occurrence of many of tween exposures and behaviors and health. The these older diseases represents a failure to use strengths of epidemiology still remain to be ex- already available knowledge. ploited, and much remains to be learned about diseases and syndromes that are widespread in the Health hazards include those identified as pres- population. ent in the workplace, those present but unidentified, and new hazards, not yet introduced there. Toxicology can garner useful information about The identified hazards include exposures to phys- the possible effects of substances, but large tox- ical agents such as radiation and noise, and ex- icologic studies are expensive, require years to posures to some substances, including chemicals, complete, and produce information that is some- metals, minerals, and vegetable dusts. Present, times difficult to apply to human exposures. Mak- unidentified hazards may be many or few. Con- ing risk assessments from animal data involves tinued observation of workers and testing of sub- both technical problems and assumptions. Al- stances are necessary to determine what exposures though continued attention to toxicology and risk are hazardous. Testing of new substances should assessment may reduce technical controversies, reduce the number of hazards introduced un- the assumptions about the predictive value of knowingly into the workplace. various tests are likely to remain in dispute. 41 42 . Preventing Illness and Injury in the Workplace Epidemiology and toxicology have not been the Occupational health surveillance is the source of panacea for solving workplace health problems both great promise and great controversy. It can be that some envisioned. The limitations of both used to identify the causes of occupational illness, argue for a continuing role for occupational medi- setting the stage for preventing further illness. But cine in hazard recognition as well as treating there are practical difficulties in implementing sys- workers. That role can be enhanced during the tems that will be statistically useful, concerns about education of physicians. company liabilities after discovering a possible rela- tionship, and concerns that efforts will be made to Computerized information about workplace ex- substitute surveillance activities for preventive ef- posures and workers’ health forms the basis for sur- forts and installation of appropriate controls. veillance systems that aim to identify health hazards. OCCUPATIONAL DISEASE Some diseases are always or nearly always to other human activities. In other words, work- caused by conditions at work. These diseases rep- place exposures c ause workers to suffer an in- resent relatively easy cases for health and safety creased incidence of disease, even though these professionals because they can be readily linked diseases also regu arly occur in the general pop- to particular working conditions. In general, iden- ulation. tification of workplace hazards is facilitated by: For example, most lung cancer occurs in smok- ● conditions at work that differ greatly from ers, and it is accepted that there is a causal rela- the normal conditions of daily life, and tionship between cigarettes and lung cancer. Some ● the presence of distinctive or very rare dis- substances encountered in the workplace are also eases in these exposed workers. known lung carcinogens because they increase the occurrence of lung cancer in nonsmokers as well Examples from the early part of this century are as in smokers. In addition, smoking and other car- the occurrence of “phossy jaw” among phosphor- cinogens may also act together to cause cancer. us match workers, the diseases of radium dial However, deciding which exposure(s) caused lung painters, and “wrist drop” caused by lead poison- cancer in a particular smoking worker is a diffi- ing among adult workers. More recently, meso- cult task. thelioma and liver angiosarcoma both occur so rarely in the nonexposed population that when Hazards that increase the incidence of common cases were observed among asbestos and vinyl diseases can be best identified using the techniques chloride workers, respectively, questions of oc- of epidemiology. But even after studies have cupational causation were immediately raised and shown a link between exposures and increased dis- relatively quickly answered. ease incidence for a group of workers, it often remains impossible to determine, for any individ- But relationships between work and diseases are ual worker, that his or her disease was caused by not always so clear-cut. In fact, it is probably occupational exposures. more frequent that working conditions directly cause or contribute to diseases that are also related MAJOR CLASSES OF OCCUPATIONAL DISEASES Occupational diseases have been recognized as Ramazzini, the 18th-century physician often called such for centuries. References to almost all classes the father of occupational medicine. Since then, and types of diseases appear in the works of the definition of disease in general has changed, —. — Ch. 3—Health Hazard Identification ● 43 ——— as has the perception of work-relatedness. Society Leading” work-related diseases, the list includes is less willing to accept adverse effects of any kind. nearly all categories of health effects that have Because so much disease is known to be pre- ever been linked to workplace conditions. ventable, poor health is no longer taken as a con- Six of the categories of diseases listed by NIOSH comitant of certain occupations. Our increasing are discussed in this chapter. Traumatic injuries ability to detect subtle effects allows us to broaden are the subject of the next chapter, and noise- our efforts in prevention. induced hearing loss is discussed in chapter 8. The There is something seductive about new risks, reader is referred to the recent textbooks by Levy and a tendency to focus on new hazards. Al- and Wegman (269) and Rem, et al. (396), for de- though in one sense occupational health is deal- tails of disease and hazard identification. ing with new and ever-subtler effects, the old diseases are still around, in greater numbers than is generally perceived. In 1979, an estimated 84,000 Respiratory Disorders active workers suffered from acute byssinosis and The lungs and other parts of the respiratory at least 35,000 employed or retired workers were tract come in contact with all manner of airborne disabled from cotton dust-related disease. In 1978, materials in the workplace. Gases, vapors, fumes, an estimated

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