Environmental and Occupational Diseases

I

Introduction

Environmental and Occupational Diseases, illnesses caused by exposure to disease-causing agents in the environment, as opposed to illnesses related primarily to an individual's genetic makeup or to immunological malfunctions. In everyday use, the term environmental disease is confined to noninfectious diseases and to diseases caused largely by exposures beyond the immediate control of the individual; the latter restriction eliminates diseases related to personal habits such as smoking or to the use or abuse of medications or drugs such as alcohol. Occupational disease, a major category of environmental disease, refers to illness resulting from job-related exposures. See Disease.

Historically, awareness of environmental diseases began with the recognition of occupational illnesses, because exposures are usually more intense in work settings than in the general environment and therefore can more readily produce overt illnesses. Examples include silicosis, a lung disease of miners, industrial workers, and potters exposed to silica dust; scrotal skin cancer in chimney sweeps exposed to soot; neurological disease in potters exposed to lead glazes; and bone disease in workers exposed to phosphorus in the manufacture of matches. Many such diseases first gained public attention during the Industrial Revolution in the 19th century.

II

Causes

Environmental diseases are caused by chemical agents, radiation, and physical hazards. The effects of exposure, in both natural and work settings, are greatly influenced by the exposure routes: primarily air pollution and water pollution, contaminated food, and direct contact with toxins. Synergistic effects—two or more toxic exposures acting together—are also important, as illustrated by the greatly increased risk of lung cancer in asbestos workers who smoke cigarettes. The potential interaction of multiple hazardous chemicals at toxic waste dumps poses a current public health problem that is of unknown dimensions.

A

Chemicals

Industrial society has introduced or increased human exposure to thousands of chemicals in the environment. Examples are inorganic materials such as lead, mercury, arsenic, cadmium, and asbestos, and organic substances such as polychlorinated biphenyls (PCBs), vinyl chloride, and the pesticide DDT. Of particular concern is the delayed potential for these chemicals to produce cancer, as in the cases of lung cancer and mesothelioma caused by asbestos, liver cancer caused by vinyl chloride, and leukemia caused by benzene. Minamata disease, caused by food contaminated with mercury, and Yusho disease, from food contaminated with chlorinated furans, are examples of acute toxic illnesses occurring in nonoccupational settings.

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The full toxic potential of most environmental chemicals has not been completely tested. The extent and frequency of an illness are related to the dose of toxin, in degrees depending on the toxin. For chronic or delayed effects such as cancer or adverse reproductive effects, no “safe” dose threshold may exist below which disease is not produced. Thus, the cancer-producing potential of ubiquitous environmental contaminants such as DDT or the PCBs remains undefined.

B

Radiation

Ionizing and nonionizing radiation can produce both acute and chronic health effects, depending on dose levels. The effects of nonionizing radiation at lower dose levels are uncertain at present. Ionizing radiation at high doses causes both acute disease and delayed effects such as cancer. Victims include workers exposed to various occupational use of X rays or radioactive materials. Although the disease-producing potential of ionizing radiation at low doses is also uncertain, an increase in chromosome damage has been observed in workers in nuclear shipyards. See Radiation Effects, Biological.

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