ABC of Safety in the Biological Sciences
Chemical Safety Information - Glossary
- An acute hazard
is one to which a single exposure may cause harm, but
which is unlikely to lead to permanent damage.
- Allergic contact dermatitis is
a type of skin hypersensitivity. Its onset may be delayed by
several days to as much as several years, for weaker
sensitizers. Once sensitized, fresh exposure to the sensitizing
material can trigger itching and dermatitis within a few hours.
- The Ames Test is used to assess
whether a chemical might be a carcinogen. It assumes that
carcinogens possess mutagenic activity, and uses bacteria and
mammalian microsomes to determine whether a chemical is a
mutagen. Approximately 85% of known carcinogens are mutagens.
The Ames test, therefore, is a helpful but not perfect predictor
of carcinogenic potential.
- Argyria or
argyrism is an irreversible blueish-black
discolouration of the skin, mucous membranes or internal organs
caused by ingestion of, or contact with, various silver
- The auto-ignition temperature
of a chemical is the lowest temperature at which the material
will ignite without an external source of ignition.
- The breakthrough
time is the time taken in standard tests for permeation
of a chemical through a protective barrier (such as a rubber
glove) to be detected.
- A carcinogen is a chemical known or
believed to cause cancer in humans. The number of known
carcinogens is comparatively small, but many more chemicals are
suspected to be carcinogenic. A partial list of known and
suspected carcinogens is held at
- The CAS Registry number is a
unique number assigned to a chemical; by the Chemical Abstracts
- A chronic hazard is a chemical
which has the potential to cause long-term damage to health,
often as a consequence of repeated or prolonged exposure to it.
- Chrysiasis is the development
of a blue-grey pigmentation in skin and mucous membranes. May be
caused by exposure to gold compounds.
- COSHH (the Control of Substances
Hazardous to Health). The COSHH regulations
impose a number of obligations on employers; the object of the
regulations is to promote safe working with potentially
- A cutaneous hazard is a
chemical which may cause harm to the skin, such as defatting,
irritation, skin rashes or dermatitis.
- ED50: (Effective
is the amount of material required to
produce a specified effect in 50% of an animal population. (See
qualification in the definition of LD50).
- Embryotoxins retard the growth
or affect the development of the unborn child. In serious cases
they can cause deformities or death. Mercury compounds and
certain heavy metals, aflatoxin, formamide and radiation are
- Etiologic agents: microscopic
organisms such as bacteria or viruses, which can cause disease.
Hazard codes - see UN hazard
A hematopoietic agent is a
chemical which interfers with the blood system by decreasing the
oxygen-carrying ability of haemoglobin. This can lead to
cyanosis and unconsiousness. Carbon monoxide is one such agent,
familiar to smokers.
A hepatotoxin is a chemical
capable of causing liver damage.
HSE The Health and Safety
Executive. The HSE web site can be reached through
www.open.gov.uk/hse/hsehome.htm. The HSE is responsible for
proposing and enforcing safety regulations throughout UK
industry and academia. Publications are available on a wide
variety of safety-related issues.
Hypoxia is a condition defined
by a low supply of oxygen.
IARC International Agency
for Research in Cancer. The IARC home page is at
IOSH Institute for Occupational
Safety and Health. IOSH has its home page at
An Irritant is a chemical which
may cause reversible inflammation on contact.
LC50: (Lethal Concentration
50) is the concentration of a chemical which kills
50% of a sample population. This measure is generally used when
exposure to a chemical is through the animal breathing it in,
while the LD50 is the measure generally used when exposure is by
swallowing, through skin contact, or by injection. (See also
is the dose of a chemical which kills 50%
of a sample population. In full reporting, the dose, treatment
and observation period should be given. Further, LD50, LC50,
ED50 and similar figures are strictly only comparable when the
age, sex and nutritional state of the animals is specified.
Nevertheless, such values are widely reported and used as an
effective measure of the potential toxicity of chemicals. (See
LDLO Lethal Dose
Median Lethal Dose (MDL): see
The MEL (Maximum Exposure
Limit) is the maximum permitted concentration of a
chemical to which a worker may be exposed over an extended
period of time. Typically, MELs are quoted in ppm for an 8-hour
reference period, though shorter periods may be quoted for some
materials. MELs are, in many countries, enforceable by law. A
list of chemicals for which MELs are defined in the UK is held
is an agent
that changes the hereditary genetic material which is a part of
every living cell. Such a mutation is probably an early step in
the sequence of events that ultimately leads to the development
NIOSH National Institute for
Occupational Safety and Health. The NIOSH home page is at
A Nephrotoxin is a chemical
which may cause kidney damage. Common examples include antimony
compounds, dimethyl sulphoxide, dimethylformamide and
A Neurotoxin is a chemical
whose primary action is on the CNS (Central Nervous System).
Many neurotoxins, such as some mercury compounds, are highly
toxic, and must only be used unbder carefully-controlled
OEL (Occupational Exposure
Limit) A (generally legally-enforcable) limit on
the amount or concentration of a chemical to which workers may
PEL: Permissible Exposure
Peroxidizable materials can
form peroxides in storage, generally when in contact with the
air. These peroxides present their most serious risk when the
peroxide-contaminated material is heated or distilled, but they
may also be sensitive to mechanical shock. The quantity of
peroxides in a sample may be determined using a simple peroxide
Photoallergic contact dermatitis
is a skin condition brought on by exposure to light following
skin contact with certain types of chemicals, such as
PPM parts per million.
Pyrophoric materials ignite
spontaneously in air. Since a wide variety of chemicals will
burn if heated sufficiently, it is usual to define a pyrophoric
material as one which will ignite spontaneously at temperatures
below about 45 C.
A reproductive toxin, such as
vinyl chloride or PCBs, is a chemical which may cause birth
defects or sterility.
Risk phrases, coded in the form
R34, R61 etc are now included in MSDS sheets for chemicals
purchased in the UK. A list of the meaning of these codes is
A substance's RTECS number is
an identification number set by the US Registry of Toxic Effects
of Chemical Substances. For further information, connect to the
RTECS home page at
A Sensitizer is a chemical
which may lead to the development of allergic reactions after
Term Exposure Limit)
is the maximum
permissible concentration of a material, generally expressed in
ppm in air, for a defined short period of time (typically 5
minutes). These values, which may differ from country to
country, are often backed up by regulation and therefore may be
Systemic poisons have an effect
which is remote from the site of entry into the body.
A teratogen is a chemical which
may cause genetic mutations or malformations in the developing
is the maximum permissible concentration of a material,
generally expressed in parts per million in air for some defined
period of time (often 8 hours). These values, which may differ
from country to country, are often backed up by regulation and
therefore may be legally enforceable.
TSCA Acronym for Toxic
Substances Control Act.
TWA (Time Weighted Average)
This term is used in the specification of Occupational
Exposure Limits (OELs) to define the average concentration of a
chemical to which it is permissible to expose a worker over a
period of time, typically 8 hours.
UN Hazard codes
- The flash point
of a chemical is the lowest temperature at which a flame
will propagate through the vapour of a combustible material to
the liquid surface. It should be noted that the source of
ignition need not be an open flame, but could equally be, for
example, the surface of a hot plate, or a steam pipe.
A vesicant is a chemical which,
if it can escape from the vein, causes extensive tissue damage,
with vesicle formation or blistering.
VOCs Volatile Organic
- Class 1 Explosive
- Class 2 Gases
- Class 3.1 Flammable liquids, flash point below -18C
- Class 3.2 Flammable liquids, flash point between -18C
- Class 3.3 Flammable liquids, flash point between 23C and
- Class 4.1 Flammable solids
- Class 5.1 Oxidizing agents
- Class 5.2 Organic peroxides
- Class 6.1 Poisonous substances
- Class 7 Radioactive substances
- Class 8 Corrosive substances
- Class 9 Miscellaneous dangerous substances
- NR Non-regulated
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