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IUPAC Glossary of Terms Used in Toxicology - Terms Starting with D

death rate
Estimate of the proportion of a population which dies during a specified period. The numerator is the number of persons dying during the period; the denominator is the size of the population, usually estimated as the mid-year population. The death rate in a population is generally calculated by the formula:

10n (Number of deaths during a specified period) / (Number of persons at risk of dying during the period)
where n is usually either 3 or 5 giving rates per 1 000 or per 100 000 people in the population studied.

Note 1: This rate is an estimate of the person-time death rate, the death rate per 10n person-years: usually n = 3. If the rate is low, it is also a good estimate of the cumulative death rate.
Note 2: This term is sometimes described as the crude death rate

decipol
Unit of perceived air quality: air on mountains or the sea has a decipol = 0.01; city air with moderate air pollution has a decipol = 0.05- 0.03; acceptable indoor air quality has decipol = 1.4 (for 80% satisfaction).

decompensation
Explicit pathophysiological changes following compensation for adverse effects.

decontamination
Process of rendering harmless (by neutralization, elimination, removal etc.) a potentially toxic substance in the natural environment, laboratory areas, the workplace, other indoor areas, clothes, food, water, sewage etc.

defoliant
Substance used for removal of leaves by its toxic action on living plants.

dehydrogenase
Enzyme which catalyses oxidation of compounds by removing hydrogen.

delayed effect
latent effect
Consequence occurring after a latent period following the end of exposure to a toxic substance or other harmful environmental factor.

de minimis risk
See risk de minimis

denaturation
  1. Addition of methanol, acetone or other suitable chemical(s) to alcohol to make it unfit for drinking.
  2. Change in molecular structure of proteins so that they cannot function normally, often caused by splitting of hydrogen bonds following exposure to reactive substances or heat.

denitrification
Reduction of nitrates to nitrites, nitrogen oxides or dinitrogen (N2) catalysed by facultative aerobic soil bacteria under anaerobic conditions.

dental fluorosis
Tooth enamel malformations due to excessive fluoride exposure during dental development.

deoxyribonucleic acid, DNA
Constituent of chromosomes which stores the hereditary information of an organism in the form of a sequence of purine and pyrimidine bases: this information relates to the synthesis of proteins and hence it is a determinant of all physical and functional activities of the cell, and consequently of the whole organism.

deoxyribonucleic acid (DNA) cloning
Replication of DNA sequences ligated into a suitable vector in an appropriate host organism.
See deoxyribonucleic acid
[9]

deoxyribonucleic acid (DNA) repair
Restoration of the molecular structure of DNA after it has been damaged by a chemical or physical agent: this may involve direct DNA damage reversal, base excision repair, nucleotide excision repair, mismatch repair, or double-strand break repair

deoxyribonucleic acid (DNA) sequencing
Determining the order of base pairs in a DNA molecule.
See deoxyribonucleic acid
After [9]

dependence
  1. A psychic craving for a drug or other substance which may or may not be accompanied by a physical dependency.
  2. Reliance on a drug or other substance to maintain health.

depilatory
Substance causing loss of hair.

deposition
  1. Process by which a substance arrives at a particular organ or tissue site, for example the deposition of particles on the ciliated epithelium of the bronchial airways.
  2. Process by which a substance sediments out of the atmosphere or water and settles in a certain place.

dermal
cutaneous
Pertaining to the skin.

dermal irritation
Skin reaction resulting from a single or multiple exposure to a physical or chemical entity at the same site, characterized by the presence of inflammation; it may result in cell death.

dermatitis
Inflammation of the skin: contact dermatitis is due to local exposure and may be caused by irritation, allergy or infection.

descriptive epidemiology
Study of the occurrence of disease or other health-related characteristics in populations, including general observations concerning the relationship of disease to basic characteristics such as age, sex, race, occupation, and social class; it may also be concerned with geographic location. The major characteristics in descriptive epidemiology can be classified under the headings: individuals, time and place.

desensitization
Suppression of sensitivity of an organism to an allergen to which the organism has been exposed previously.

desiccant
  1. Drying agent.
  2. In agriculture, a substance used for drying up plants and facilitating their mechanical harvesting.

desorption
Opposite of adsorption; a decrease in the amount of adsorbed substance.

desquamation
Shedding of an outer layer of skin in scales or shreds.

deterministic
Term applied to health effects, the severity of which varies with the dose and for which a threshold is believed to exist.

deterministic effect
deterministic process
Phenomenon committed to a particular outcome determined by fundamental physical principles.
See also stochastic effect
[2]

detoxification
detoxication
  1. Process, or processes, of chemical modification which make a toxic molecule less toxic.
  2. Treatment of patients suffering from poisoning in such a way as to promote physiological processes which reduce the probability or severity of adverse effects.

detriment
Estimated measure of the expected harm or loss associated with an adverse event, usually in a manner chosen to facilitate meaningful addition over different events. It is generally the integrated product of arbitrary values of risk and hazard and is often expressed in terms such as costs in US dollars, loss in expected years of life or loss in productivity, and is needed for numerical exercises such as cost-benefit analysis.

developmental toxicity
Adverse effects on the developing organism (including structural abnormality, altered growth, or functional deficiency or death) resulting from exposure through conception, gestation (including organogenesis), and postnatally up to the time of sexual maturation.

diaphoresis
Profuse perspiration.

diaphoretic
sudorific
Substance that causes sweating.

diarrheic shellfish poisoning, DSP
diarrheal shellfish poisoning
Serious illness which is a consequence of consumption of bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing a group of high molecular weight polyethers such as okadaic acid, dinophysis toxins, pectenotoxins, and yessotoxin; gastroenteritis develops shortly after ingestion and generally lasts 1-2 days.

diffusion
Spontaneous differential movement of components in a system.
Note: In molecular terms, the driving force for diffusion is random thermal motion. In thermodynamic terms, the driving force is a gradient of chemical potential.
[2]

diffusion coefficient, D
Proportionality constant D, relating the flux (flux density) of amount No Entry of entities B, Jn,B, to their concentration gradient
Jn= –D grad cB
After [2]

dimercaprol
2,3-dimercaptopropan-1-ol
See 2,3-bis(sulfanyl)propan-1-ol

diploid
Chromosome state in which the chromosomes are present in homologous pairs.
Note: Normal human somatic (non-reproductive) cells are diploid (they have 46 chromosomes), whereas reproductive cells, with 23 chromosomes, are haploid.

discharge
See emission

discharge (effluent, emission) standard or release limit
Maximum amount of a pollutant released from a given source to a specified medium which is acceptable under specified circumstances.

discontinuous effect
See intermittent effect

discordance (genetic)
antonym concordance
Any difference in a character between individuals due to genetic differences such as may occur in dizygotic twins, or between matched pairs in a case cohort study.

disease
Literally, dis-ease, lack of ease; pathological condition that presents a group of symptoms peculiar to it and which establishes the condition as an abnormal entity different from other normal or pathological body states.

discontinuous effect
See intermittent effect

dispersion (in environmental chemistry)
Dilution of a pollutant by spreading in the atmosphere or water due to diffusion or turbulent action.

disposition
  1. Natural tendency shown by an individual or group of individuals, including any tendency to acquisition of specific diseases, often due to hereditary factors.
  2. Total of the processes of absorption of a chemical into the circulatory systems, distribution throughout the body, biotransformation, and excretion.
    [2]

dissipation
Reduction in the amount of a pesticide or other compound which has been applied to plants, soil etc. (used when it is not clear whether this is by mineralization degradation, binding, or leaching).

distributed source
See area source

distribution
  1. Apportionment of a solute between two phases. The term partition or extraction may also be used in this sense where appropriate.
    [2]
  2. Dispersal of a substance and its derivatives throughout the natural environment or throughout an organism.
    [2]
  3. Final location(s) of a substance within an organism after dispersal.

distribution constant
See partition ratio

distribution volume
Theoretical volume of a body compartment throughout which a substance is calculated to be distributed.
[2]

2,3-disulfanyl-1-propanol
See 2,3-bis(sulfanyl)propan-1-ol

diuresis
Excretion of urine, especially in excess.

diuretic
micturitic
Agent which increases urine production.

DNA adduct
See adduct, deoxyribonucleic acid

DNA amplification
See gene amplification, deoxyribonucleic acid

DNA cloning
See deoxyribonucleic acid cloning

DNA repair
See deoxyribonucleic acid repair

DNA sequencing
See deoxyribonucleic acid sequencing

dominant
Allele which expresses its phenotypic effect when present in either the homozygous or the heterozygous state.
After [9]

dominant half life
Half life of a fraction of a substance in a specific organ or compartment if it defines approximately the overall clearance rate for that substance at a specific time point.
[2]

dominant lethal mutation
Genetic change occurring in a germ cell which does not cause dysfunction of the gamete but which is lethal to the fertilized egg or developing embryo which develops from it.
Note: Induction of a dominant lethal event after exposure to a chemical substance (dominant lethal test) indicates that the substance has affected germinal tissue of the test species.

dosage (of a substance)
Dose divided by product of mass of organism and time of dose.
Note: Often expressed as mg (kg body weight)-1 day-1 and may be used as a synonym for dose.
[2]

dose

dose-effect
Relation between dose and the magnitude of a measured biological change.
[2]

dose-effect curve
Graph of the relation between dose and the magnitude of the biological change produced measured in appropriate units.

dose-effect relationship
Association between dose and the resulting magnitude of a continuously graded change, either in an individual or in a population.
[2]

dose-response curve
Graph of the relation between dose and the proportion of individuals in a population responding with a defined biological effect.
[2]

dose-response relationship
Association between dose and the incidence of a defined biological effect in an exposed population usually expressed as percentage.
[2]

Draize test
Evaluation of materials for their potential to cause dermal or ocular irritation and corrosion following local exposure; generally using the rabbit model (almost exclusively the New Zealand White) although other animal species have been used.

drug
medicine
pharmaceutical
Any substance which when absorbed into a living organism may modify one or more of its functions.
Note: The term is generally accepted for a substance taken for a therapeutic purpose, but is also commonly used for abused substances.

duplicate portion sampling method (diet/food)
duplicate diet study
Study in which test persons consume their ordinary diet but, for each meal, they prepare for subsequent analysis a duplicate portion of all food as prepared, served and consumed.

duplicate (replicate) samples (in chemistry)
Two (or multiple) samples taken under the same or comparable conditions.

dysarthria
Imperfect articulation of speech due to neuromuscular damage.

dysfunction
Abnormal, impaired, or incomplete functioning of an organism, organ, tissue or cell.

dysplasia
Abnormal development of an organ or tissue identified by morphological examination.

dyspnea
Difficult or labored breathing.