PRINCIPLES OF TOXICOLOGY

pernicious anemia The progressive, megaloblastic anemia resulting from lack of vitamin B12,
sometimes accompanied by degeneration of the postier an lateral columns of the spinal cord.
peroxidase Any of a group of enzymes that occur especially in plant cells and catalyze the oxidation
of a substance by a peroxide.
personal protective equipment Any devices worn by individuals as protection against hazards in
the environment or the workplace, including respirators, gloves, goggles, and earmuffs.
pesticide Any substance used to destroy or inhibit the action of plant or animal pests. See carbamate;
organochlorine pesticides; organophosphate pesticides.
petechiae Tiny, nonraised, perfectly round, purplish red spots caused by intradermal or submucosal
hemorrhaging.
pH A value taken to represent the acidity or alkalinity of an aqueous solution. It is defined as the
logarithm of the reciprocal of the hydrogen-ion concentration of a solution:
pH = ln 1
[H + ]
GLOSSARY 569
pharmacokinetics The field of study concerned with the techniques used to quantify the absorption,
distribution, metabolism, and excretion of drugs or chemicals in animals, as a function of time.
pharmacology The unified study of the properties of chemical agents (drugs) and living organisms
and all aspects of their interactions. An expansive science encompassing areas of interest germane
to many other disciplines.
phenothiazine A green, tasteless compound with the formula C12H9NS, prepared by fusing diphenylamine
with sulfur; also, a group of tranquilizers resembling phenothiazine in molecular structure.
phocomelia A developmental anomaly characterized by the absence of the proximal portion of a
limb or limbs, such that hands or feet are attached to the trunk of the body by a single small,
irregularly shaped bone.
phospholipase Any enzyme that catalyzes the hydrolysis of a phospholipid.
photophobia Abnormal sensitivity, usually of the eyes, to light.
photosensitivity reactions Undesirable reactions in the skin of persons exposed to certain chemicals
when the skin is also exposed to sunlight (in some cases, to artificial light). Dermatologic lesions
form, which vary from sunburn-like responses to edematous, vesiculated lesions or bullae.
phototoxicity Capacity of a chemical to (nonimmunlogically) sensitize the skin to a light-induced
reaction.
pilosebaceous units Relating to the hair follicles and sebaceous glands.
pK The acidic dissociation constant of a compound; the pH of an aqueous solution of an acid or base
at which equal concentrations of each are present, at the point at which dissociation is half-complete.
The negative logarithm of the ionization constant Ka.
pneumoconiosis Accumulation of dusts in the lungs and the tissue reaction to the presence of such
dust.
pneumonitis Inflammation of lung tissue.
point mutation An alteration in a single nucleotide pair in the DNA molecule, usually leading to a
change in only one biochemical function.
poison The term used to describe those materials or chemicals that are distinctly harmful to the body.
polymorphism The occurrence of different genetic forms or types of a protein that produce
phenotypically distinct populations.
polymorphonuclear Having a nucleus deeply lobed or so divided as to appear to be multiple.
polyneuritis Inflammation of several nerves simultaneously, as in lead palsy.
polyneuropathy A disease involving several nerves.