A measure of how poisonous a substance is, usually caused by enzyme inhibition
If biological reactions controlled by proteins and enzymes
cannot take place then the affected cells may malfunction
Specificity
A measure of differing toxicities of a substance on different organisms
A specific substance is very toxic to some organisms but much less toxic to ohers
Persistance
A measure of the rate at which a material breaks down
and therefore the length of time it remains in the
environment
Does not apply to elements that cannot
break down under normal environmental
conditions - non degradable
CFCs and DDT are good examples
of persistent chemicals - they can
take decades to break down
Biodegradability
The ease with which a material is broken
down by living organisms, usually bacteria
Mobility
A measure of how easily a material
moves through the environment
Highly mobile pollutants can travel longer distances,
causing problems over larger areas, although they
may also be diluted and become less locally harmful
Solubility
The ease with which the
molecules of a material separate
and disperse into a liquid
These materials are very mobile in the
hydrosphere - lakes, rivers, oceans, etc
Liposolubility - A measure of how easily a substance
dissolves in fats and oils
These materials (e.g. PCBs, mecury, lead,
organochlorine insecticides) be stored for
long periods of time in living organism
Bioaccumulation
The increase in concentration of a substance in living tissue
Chronic exposure to small doses over long
periods of time may result in bioaccumulation.
This occurs most often with liposolubles.
Biomagnification
The progressive bioaccumulation of a material along a food chain
Synergism
The process where the presence of two
materials produces a greater effect that
the sum of their individual effects
Synergism is difficult to predict and although there are some
known examples (zinc and cadmium) it is impossible to test
out all possible combinations to which we are exposed
Mutagenicity
A mutagen is a material that can
cause changes in DNA structure
If gametes are affected then babies
produced may have birth abnormalities that
could be passed on to future generations
Carcinogenicity
A carcinogen is a mutagen that causes body cells to
start to multiply in an uncontrolled way (cancer)
Teratogenicity
A substance that interferes with gene function
in a growing embryo so that a non-inherited
birth abnormality is produced
Primary/Secondary
Primary pollutants are pollutants released from direct human
activity e.g. carbon dioxide from burning fossil fuels
Secondary pollutants are pollutants produced
through chemical reactions between primary
pollutants e.g. PANs