Hazard Assessment and Contaminated Sites - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 560

Dermal Of the skin, through or by the skin.
Dose A stated quantity or concentration of a contaminant to which an organism
is exposed over a continuous or intermittent duration of exposure. It is most com-
monly expressed as the amount of test contaminant per unit weight of test animal
(e.g., mg/kg bw ).
The applied dose is the amount of contaminant in contact with the primary
absorption boundaries (e.g., skin, lungs, and gastrointestinal tract) and available for
absorption The absorbed dose is the amount crossing a specific absorption barrier
(e.g., the exchange boundaries of skin, lung, and digestive tract) through uptake
processes. The amount of the contaminant available for interaction by any partic-
ular organ or cell is termed the delivered dose of that organ or cell (EPA 1992, p.
22933). The systemic dose is the dose to which the whole, or extensive parts, of
the body is exposed. The absorbed dose may not be the systemic dose as contami-
nants absorbed in the digestive tract may be removed by the liver and not enter the
systemic circulation.
Dosage A general term comprising the dose, its frequency and the duration of
dosing. Dosage is properly applied to any rate or ratio involving a dose. Dosages
often involve the dimension of time (e.g., mg/kg bw /day), but the meaning is not
restricted to this relationship (Hayes 1991 ).
Dose-response Assessment Determination of the relationship between the magni-
tude of the dose or level of exposure to a contaminant and the incidence or severity
of the associated adverse effect (IEH 1999 ).
Dose-response relationship The correlative association existing between the dose
administered and the response (effect) or spectrum of responses that is obtained. The
concept expressed by this term is indispensable to the identification, evaluation, and
interpretation of most pharmacological and toxicological responses to contaminants.
The basic assumptions which underlie and support the concept are: (a) the observed
response is a function of the concentration at a site, (b) the concentration at a site
is a function of the dose, and (c) response and dose are causally related (Eaton
and Klaassen 1996 ). The existence of a dose-response relationship for a particular
biological or toxicological response (effect) provides a defensible conclusion that
the response is a result of exposure to a known contaminant.
Endpoint An observable or measurable biological event used as an indicator of
the effect of a contaminant on a biological system (cell, organism, organ etc.).
Environmental health Those aspects of human health determined by physical,
chemical, biological and social factors in the environment. Environmental health
practice covers the assessment, correction, control and prevention of environmental
factors that can adversely affect health, as well as the enhancement of those aspects
of the environment that can improve human health.
Environmental monitoring The monitoring of the concentration of contaminants
in the physical environment of air, water, soil and food.