Are rat results from intratracheal instillation of 19 granular dusts a reliable basis for predicting cancer risk?

We analyzed the so-called "19-dust-studies" (19-DS) that reported lifetime lung tumor occurrence in female rats following repetitive, short-term intratracheal instillation (ITI) of 19 different insoluble dusts. In the 19-DS, lung instillation of up to 120mg/rat of granular, biopersistent, low-specific-toxicity particles (GBP) caused about half of the rats to develop lung tumors, but the relevance of these data to deriving exposure limits for GBP is uncertain. Specific drawbacks to using the 19-DS for risk assessment include: (1) Delivery, via ITI, of a worker's estimated lifetime lung dose causes "lung overload" in rats, and is not equivalent to lifetime inhalation exposure; (2) The response of rats to insoluble-particle "lung overload" is stereotyped and unique to that species; (3) The 19-DS did not include low-dose studies, and the dose-response showed saturation at the high levels; (4) When the lung-overload threshold is exceeded, rats develop lung tumors from ongoing inflammation (as opposed to particle-specific toxicity); that is, the dramatically increased dose-delivery rate evokes mechanisms not relevant to gradual exposure; and (5) workers historically exposed to potentially lung-overloading burdens of inhaled dust (e.g., coal workers, underground miners using diesel equipment) do not exhibit an established lung-cancer excess. Our critical review of the data from the 19-DS suggests that the reported results for GBP are not a reliable basis for predicting human lung cancer risk, e.g., for the typical inhaled-dose conditions for which worker exposure limits to GBP are promulgated.

Health and productivity: a role for occupational health professionals.

The impressive economic gains achieved by many nations within the past decade have been attributed primarily to improvements in productivity from technological changes. The resultant low unemployment levels, however, emphasize the importance of human capital in the success of any enterprise. Concurrently, some economists have proposed an alternative economic view regarding the relationship between health and income, postulating that improvements in the health of the nation's population have a substantial effect on its economic viability. Such a view directly pertains to occupational health professionals, who are often charged with promoting the health of the worker. Although studies relating the beneficial impact of occupational health on productivity and human performance are limited, some efforts have shown impressive effects, as measured primarily by reduced absenteeism. The prompt, assertive management of occupational injuries and illnesses and their treatment have been well documented. Illnesses not considered traditional occupational ailments, such as migraine headaches, allergic disorders, infectious diseases, and depression, offer opportunities for occupational health professionals to ensure an accurate diagnosis and proper treatment for minimizing the impact on work performance. Considerable opportunities exist for occupational health professionals to demonstrate the importance of certain services to productivity.

Occupational ingestion of P-32: the value of monitoring techniques to determine dose. A case report.

The purpose of this article is to described the analytical methods used to assess the internal dose from a P-32-labeled compound that was inadvertently ingested. Bioassay data, using the International Commission on Radiation Protection (ICRP)-30 model, enabled the calculation of internal dose. Whole body counting (WBC) and urinary measurement with liquid scintillation counting were utilized to estimate the amount of radioactive material deposited in body organs. This metabolic model assumes that 80% of the material ingested is absorbed through the gastrointestinal tract because P-32 is soluble. The time of the intake, a critical variable in this method, was estimated on the basis of urine contamination of clothing. Twenty-four-hour urine sampling over a 6-week period, coupled with daily WBC over the same period, was performed. Because P-32 does not emit photons, WBC relied on measuring the bremsstrahlung radiation produced as a result of interaction of beta radiation with the body's tissues. A P-32-spiked phantom was used as a control. Over the 6-week monitoring period, urinary results indicated an ingestion of 560 microCi of P-32, whereas WBC estimated on intake of 580 microCi. An assessment of the laboratory where the accident occurred indicated that approximately 600 microCi of radioactive phosphorous was missing. The total effective dose equivalent was estimated at 4.8 rem (48 mSv). On the basis of this study, the ICRP model appears to fit the data obtained from urine measurements and WBC. No symptoms were noted from the ingestion of 580 microCi. The committed organ doses were well within the occupational nonstochastic limits of 50 (0.5 Sv) permitted by the Nuclear Regulatory Commission. These results were confirmed by NUREG/CR-4884 and commercial software (CINDY). This report confirms the value of using the ICRP-30 model with urinary measurements and WBC to estimate the dose received as a result of ingestion of radioactive P-32.

Hodgkin's disease, work, and the environment. A review.

Hodgkin's disease (HD), a lymphoma with an annual incidence in the United States of approximately 7500 cases, primarily affects the lymph nodes, spleen, and liver. The point of this article is to critically review the literature regarding the purported relationships between HD, certain occupations, and exposure to chemical agents. Attention will also be focused on recent advances in molecular genetics in the etiology of this ailment. A MEDLINE search was conducted to assess case-control and mortality evaluations that investigated links between HD and certain occupations and exposure to designated hazards. A review of citations in the Silver Platter Occupational and Environmental Medicine CD-ROM database was also conducted to ensure that all pertinent reports were obtained. Of the industries evaluated, woodworking showed the most consistent link between an increased risk of HD (relative risk, 1.8 to 7.2), but not all studies conducted showed positive associations. Although certain chemicals (ie, chlorophenols, pesticides) were reported as risks, no chemical was consistently and unambiguously linked with HD. Recent investigative work, however, points to a major etiological role for the Epstein-Barr virus (EBV), genetic fragments of which have been noted in Reed-Sternberg cells, the classic malignant cells of HD. The occupation most consistently associated with HD appears to be woodworking, although no specific chemical has been consistently linked with this lymphoma. The most persuasive evidence regarding the cause of HD arises from recent studies, including epidemiological, clinical, and genetic studies, that point to a major role by the EBV.

Prevalence of small lung opacities in populations unexposed to dusts. A literature analysis.

OBJECTIVES: Despite the wide use of the International Labor Organization (ILO) system for reading chest radiographs, little information is available regarding the prevalence of abnormalities in populations unexposed to dusts. Prevalence studies of radiographic changes consistent with dust inhalation, as classified by the system, would be more meaningful if there were better understanding regarding the extent of abnormalities in unexposed populations. DESIGN: To determine small opacity prevalence in unexposed populations, a review of articles published since 1970 that used the ILO system to classify radiographs of the unexposed, either as subjects or control subjects, was performed. Criteria for inclusion in this review included ascertainment of the lack of exposure of subjects to occupational dusts, and independent reading of radiographs by at least two readers certified in the ILO system (B readers) or experienced in its use. A total of eight published articles presenting data on nine study populations were included in this study. RESULTS: The prevalence of small opacities graded 1/0 or greater varied widely, with a range from 0.21 to 11.7%. A meta-analysis of the published data yielded a population prevalence of 5.3% (95% confidence interval [CI] = 2.9 to 7.7%). The prevalence was significantly greater in Europe than in North America (Europe, 11.3%; 95% CI = 10.1 to 12.5%; North America, 1.6%; 95% CI = 0.6 to 2.6%). A subset of the studies contained information on gender that showed greater prevalence of lung opacities in male subjects than female subjects (male subjects, 5.5%; 95% CI = 3.4 to 7.6%; female subjects, 3.5%; 95% CI = 1.3 to 5.8%). Based on estimated age information, the studies were divided into two strata (mean age < 50 years vs > or = 50 years). The age-specific pooled prevalence was higher in the studies with mean age > or = 50 years than studies with mean age < 50 years in both Europe (11.7% vs 9.6%) and North America (2.3% vs 0.6%). Prevalence of lung opacities remained significantly higher in Europe and North America in each age stratum. The large difference in the prevalence between Europe and North America could not be explained on the basis of age, gender, or smoking history, although available age and smoking data are less robust. CONCLUSIONS: These results indicate that a background level of opacities consistent with the radiographic appearance of pneumoconiosis exists in populations considered to be free of occupational dust exposure. Environmental and unaccounted occupational exposures, as well as reader variability, all may play a role in the determination of small opacity prevalence in these subjects and may explain the large differences between Europe and North America. Thorough ascertainments of occupational and environmental exposures are essential to determine the true significance of opacities in populations who are not exposed to dust.

Emergency response to environmental toxic incidents: the role of the occupational physician.

A survey of accidental environmental releases of hazardous chemicals conducted by the Agency for Toxic Substances and Disease Registry indicates that fixed facility events accounted for 77% of the episodes whereas 23% of the releases were related to transportation activities, such as loading or unloading materials. In nearly all the events (88%) only one chemical was released. Volatile organic compounds, chlorine, herbicides, acids and ammonia were the most common substances involved. In nearly one out of six reported events, an injury occurred. To prepare for emergencies associated with the accidental release of hazardous materials, the federal government, industry and professional organizations including the medical community have all been involved. In the United States, the Superfund Amendment Reauthorization Act (SARA) Title III passed in 1986 addresses the need to establish local emergency planning committees, to report and collect data, and a number of other matters. Professional societies, including the Joint Commission for the Accreditation of Health Care Organizations, the American College of Occupational and Environmental Medicine (ACOEM), and the American Industrial Hygiene Association, have all attempted to ensure proper education and training of those professionals called to assist in such emergencies. The occupational physician can assume numerous roles in the challenge related to emergency response, by becoming familiar with computerized information available to promptly determine the type of hazard released and its appropriate antidote, advising on the proper personal protective equipment, awareness of secondary contamination and participation on local emergency planning committees among many others. Emergency release of hazardous materials continues to occur with a frequency in the United States that deserves active vigilance and planning.

Preserving confidentiality in occupational medical practice.

The United States does not have a uniform law regarding medical confidentiality. However, codes of conduct from the American Medical Association, the American College of Occupational and Environmental Medicine and the International Commission of Occupational Health, as well as relevant parts of the Americans with Disabilities Act and the Occupational Safety and Health Act of 1970, can help physicians make informed decisions about requests for medical information. Such activities include preplacement and fitness-for-work evaluations medical surveillance examinations (including drug testing) and evaluation of symptoms and treatment of injuries that may be work-related. The patient should be the one to decide whether and when to release medical records to employers, unless overruled by public health risks or laws.

Bronchiolitis obliterans from exposure to incinerator fly ash.

Inhalation of toxic substances in the workplace can result in a variety of respiratory disorders. One relatively rare sequela of the inhalation of toxic fumes is bronchiolitis obliterans, a condition characterized by fibrosis and narrowing of the small airways. Several substances have been reported to cause bronchiolitis obliterans, including ammonia, chlorine, hydrogen fluoride, hydrogen sulfide, nitrogen dioxide, ozone, phosgene, and other irritant fumes. Little has been reported on the pulmonary effects of fly ash produced by the incineration of coal and oil. We report a case of bronchiolitis obliterans with a component of partially reversible airway obstruction in a 39-year-old male occupationally exposed to incinerator fly ash.

Challenges and opportunities in occupational medicine.

Recent position papers of the American College of Physicians and the Institute of Medicine have emphasized the role of primary care physicians in occupational medicine. Although opportunities for physicians to become certified in occupational medicine have expanded, shortages in the specialty are likely to persist throughout the 1990s. To help acquaint osteopathic physicians with some of the challenges facing the specialty of occupational medicine, this article addresses the extent of occupational illnesses, health-related policies in the workplace, the delivery of occupational medical services, and graduate medical education.

Confined space hazards: combined exposure to styrene, fiberglass, and silica.

Work in confined spaces continues to present hazards to workers. The magnitude of this problem was recently addressed by the Occupational Safety and Health Administration in its Final Rule for "Permit-Required Control Spaces for General Industry" (29 CFR Parts 1910). Although illness and injury are typically due to asphyxiation, explosion, and drowning, toxic exposures also are an important risk. We describe herein four workers engaged in erosion-proofing enclosed chemical tanks with minimal ventilation and no respiratory protection. They were exposed to styrene-based solvents, styrene-based resins, silica, and fiberglass dust. Each experienced acute neurological effects and bronchitis. One worker developed a life-threatening pneumonia that resulted in numerous complications. The severity of the illness, which would likely not have otherwise occurred, resulted from impaired lung defense mechanisms due to the combined exposures. Several studies support the association of styrene exposure and respiratory illness that may be compounded by co-exposure to fiberglass in unique circumstances. To prevent the hazards of confined space, recommended procedures should be followed, including those established by the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration.

The academic occupational physician as consultant. A 10-year perspective.

The academic community has long served the private sector in a consultant capacity in engineering and in the sciences. With respect to occupational medicine, physicians, when working for industry, have generally practiced in a health care setting. Within the past 10 years, however, the business sector has placed more attention on the health implications of its operations as a result of regulations, liability, and rising health care costs. These issues, which go beyond traditional clinical responsibilities, have furthered the need for businesses to receive strategic medical advice to effectively operate and to maintain a competitive edge. One particular business sector, the chemical industry, has been challenged seriously because of legitimate as well as perceived health risks associated with the production and use of its products. This paper describes the professional experiences over a 10-year period (1983 to 1993) of an occupational physician working as a consultant to an international chemical company. Services have related to epidemiology, health policy, toxicology, plant oversight as well as serving as a health advisor on matters involving the relation between business and health. An academic affiliation with an occupational medicine residency program has facilitated access to related occupational health professionals to assist in problem solving and research. Opportunities for consulting in occupational medicine will depend upon the nature of the organization as well as the personal and professional characteristics of the physician. Requests for these types of services, however, are likely to expand in the near future, primarily as a result of wider awareness of the implications of work on health, increased litigation, and government regulations.

Environmental health in the journals.

The environmental health aspects of general medical practice have attracted the attention of many professional organizations in the past few years, including the American College of Physicians, the Institute of Medicine, and the American College of Occupational Medicine. To assess the degree of emphasis placed on environmental health issues in professional journals, a survey of representative specialty and general medical journals was conducted through a Medline literature search. Over the past 15-year period (1976-1990) specialty journals demonstrated a dramatic and consistent increase in published articles that were indexed under the headings environmental pollution, environmental pollutants, and environmental cancer. General medical journals also demonstrated continued increases in the rate of published articles addressing these environmental health topics. Within the environmental categories, air pollution, especially that due to dusts, was the most heavily indexed topic, followed by water pollution, especially that due to chemical contamination. This study supports the notion that environmental health issues are assuming more importance in general medical practice, especially within the specialty of occupational medicine.