PRINCIPLES OF TOXICOLOGY

568 GLOSSARY
oral route The entry of a chemical into the body by way of the gastrointestinal tract. Although
absorption to some extent takes place throughout the tract, the majority of the absorption takes
place in the area of the villi of the small intestine.
organic acid Any acid, the radical of which is a carbon derivative; a compound in which a
hydrocarbon radical is joined to COOH (carboxylic acid) or to SO3H (sulfonic acid).
organochlorine pesticides These compounds are extremely stable and persistent in the environment.
They are efficiently absorbed by ingestion, and act on the central nervous system to stimulate or
depress it. Signs and symptoms of toxicity vary with the specific chemical. In general, mild
poisoning cases cause symptoms such as dizziness, nausea, abdominal pain, and vomiting. In
chronic poisoning, weight loss and loss of appetite, temporary deafness, and disorientation can
occur.
organophosphate pesticides These are irreversible inhibitors of cholinesterase, thus allowing
accumulating of acetylcholine at nerve endings. They are rapidly absorbed into the body by
ingestion, through intact skin, including the eye, and by inhalation. Poisoning symptoms range
from headache, fatigue, dizziness, vomiting, and cramps in mild cases, to the rapid onset of
unconsciousness, local or generalized seizure, and other manifestations of a cholinergic crisis in
severe cases.
osteomalacia A condition of softening of the bones characterized by pain, tenderness, loss of weight,
and muscular weakness.
osteoporosis Abnormal rarefaction of bone, seen most commonly in the elderly.
osteosclerosis Hardening or abnormal density of bone.
ototoxic Having a toxic effect on the structures of the ear, especially on its nerve supply.
pancytopenia A form of anemia in which the capacity of the bone marrow to generate red blood
cells is defective. This anemia may be caused by bone marrow disease or exposure to toxic agents,
such as radiation, chemicals, or drugs.
paraffin A class of aliphatic hydrocarbons characterized by a straight or branched carbon chain afid
having the generic formula CnH2n+2; also called alkane.
paranoid schizophrenia A psychotic state characterized by delusions of grandeur or persecution,
often accompanied by hallucinations.
parasympathetic Craniosacral division of the autonomic nervous system. These cholinergic nerves
are associated with normal body functions (e.g., smooth muscle in blood vessels, salivary glands,
and GI tract).
paresthesia (also paraesthesia) A skin sensation, such as burning, prickling, itching, or tingling,
with no apparent physical cause.
Parkinsonism A group of neurologic disorders characterized by hypokinesia, tremor, and muscular
rigidity.
PEL See permissible exposure limit.
percutaneous absorption The transfer of a chemical from the outer surface of the skin through the
horny layer (dead cells), through the epidermis, and into the systemic circulation. A variety of
factors, such as pH, extent of ionization, molecular size, and water and lipid solubility govern
transfer of chemicals through the skin.
perinatal toxicology The study of toxic responses to occupationally or environmentally encountered
substances during a woman’s exposure to those substances from the time of conception through
the neonatal period.
peripheral neuritis Inflammation of the nerve ending or of terminal nerves.
permissible exposure limit (PEL) A measure of the toxicity of a substance, established by the U.S.
Department of Labor, Occupational Safety and Health Administration (OSHA); an 8-h, timeweighted
average (TWA) limit of exposure is most commonly used. The limit is commonly
expressed as the concentration of a substance per unit of air volume (mg/m 3 , ppm, fibers/cm 3 , etc.)