++
KEY POINTS
-
Occupational toxicology is the application of the principles and methodology of toxicology toward chemical and biological hazards encountered at work.
-
In occupational environments, exposure is often used as a surrogate for dose.
-
Occupational exposure limits do not correspond to the level of exposure below which the probability of impairing the health of the exposed workers is acceptable.
-
Diseases arising in occupational environments involve exposure primarily through inhalation, ingestion, or dermal absorption.
++
Occupational toxicology applies the principles and methodology of toxicology toward understanding and managing chemical and biological hazards encountered at work. As new hazards arise with the emergence of new technologies, occupational toxicologists must be prepared to assess the risks and protect the health of workers. Because the work environment can present exposures to complex mixtures, the occupational toxicologist must also recognize those that are particularly hazardous when occurring in combination.
++
It is often difficult to establish a causal link between a worker’s illness and job. First, the clinical manifestations of occupationally induced diseases are often indistinguishable from those arising from nonoccupational causes. Second, there may be a protracted but biologically predictable latent interval between exposure and the expression of disease. Third, diseases of occupational origin may be multifactorial with other environmental factors or personal risk factors contributing to the disease process. Nevertheless, studies have repeatedly shown that the dose of toxicant is a strong predictor of the likelihood, severity, and type of health effect.
+++
WORKPLACES, EXPOSURES, AND STANDARDS
+++
The Nature of the Workforce
++
The world’s labor force totals 3.45 billion people, with approximately 31.3% engaged in agricultural production. In industrialized nations, workers have transitioned from jobs in heavy industry and agriculture toward jobs in the service sector and high-technology industries. Some manufacturing jobs have moved to less developed countries with less stringent worker health protection. The presence of children in the workforce has important ramifications on body burdens, disease latency, toxicokinetics, and biotransformation of toxicants.
++
Dose is typically defined as the amount of toxicant that reaches a target tissue over a defined time span. In occupational environments, exposure is often used as a proxy for dose. The response to a chemical depends on host factors and dose. Figure 34–1 illustrates the pathway from exposure to subclinical disease or to adverse health effect and that shows there are important modifying factors (contemporaneous exposures, genetic and epigenetic susceptibility, age, gender, nutritional status, and behavioral factors) that can influence whether a worker remains healthy, develops subclinical disease that is repaired, or progresses to frank illness. Also, dose is a function of exposure concentration, exposure duration, and exposure frequency. Workplace health protection and surveillance programs (shown in blue) can reduce exposures, disrupt the exposure-dose pathway, or identify internalized dose and early effects before irreparable disease develops, thereby ensuring a safe workplace ...