PRINCIPLES OF TOXICOLOGY

GLOSSARY 561
eczema A superficial inflammatory process involving primarily the epidermis; characterized early
by redness, itching, minute papules and vesicles, weeping of the skin, oozing, and crusting, and
later by scaling, lichenification, and often pigmentation.
ED50 The dose of a particular substance that elicits an observable response in 50 percent of the test
subjects.
edema The presence of abnormally large amounts of fluid in intercellular spaces within a tissue.
electrophile A chemical compound or group that is attracted to electrons and tends to accept
electrons.
elimination The removal of a chemical substance from the body. The rate of elimination depends
on the nature of the chemical and the mechanisms that are used to remove the chemical from the
organism. Examples of mechanisms include expiration from the lungs, excretion by the kidneys
by way of the urinary system, excretion in the sweat or saliva, and chemical alteration by the
organism and subsequent excretion by any of these mechanisms. See excretion.
emphysema Literally, an inflation or puffing up; a condition of the lung characterized by an increase,
beyond the normal, in the size of air spaces distal to the terminal bronchiolus.
encephalopathy Any degenerative disease of the brain.
endoplasmic reticulum An ultramicroscopic organelle of nearly all cells of higher plants and
animals, consisting of a more or less continuous system of membrane-bound cavities that ramify
throughout the cell cytoplasm.
endothelial Pertaining to the layer of flat cells lining blood and lymphatic vessels.
endotoxin A toxin produced by certain bacteria and released on destruction of the bacterial cell.
engineering control A method of controlling exposures to contaminants by modifying the source
or reducing the quantity of contaminants released into the environment.
enterohepatic circulation The recurrent cycle in which the bile salts and other substances excreted
by the liver pass through the intestinal mucosa and become reabsorbed by the hepatic cells, and
then are reexcreted.
environmental toxicology That branch of toxicology that deals with exposure of biologic tissue
(more specifically, human life) to chemicals that are basically contaminants of the biologic
environment, or of food, or of water. It is the study of the causes, conditions, effects, and limits of
safe exposure to such chemicals.
eosinophil A structural cell or histologic element readily stained by eosin; especially, a granular
leukocyte containing a nucleus usually with two lobes connected by a slender thread of chromatin,
and having cytoplasm containing coarse, round granules that are uniform in size.
epidemic Spreading rapidly and extensively by infection and affecting many individuals in an area
or a population at the same time: an epidemic outbreak of influenza.
epidermal tumor A tumors arising from the skin (dermal) epithelial layer.
epidermis The outermost and nonvascular layer of skin. It derives from embryonic ectoderm.
epistaxis Nosebleed.
epithelioma Any tumor developing in the epithelium, which is the kind of tissue that covers internal
and external surfaces of the body.
epoxide An organic compound containing a reactive group comprising a ring formed by an O
oxygen atom joined to two carbon atoms, having the structure at right.
erethism Excessive irritability or sensitivity to stimulation, particularly with reference to the sexual
organs, but including any body parts. Also a psychic disturbance marked by irritability, emotional
instability, depression, shyness, and fatigue, which are observed in chronic mercury poisoning.
erythema The redness of the skin produced by congestion of the capillaries.
erythropoiesis The production of erythrocytes (red blood cells).