The
definition of a carcinogen is simply 'A
substance that causes
cancer or is
believed to
cause cancer'.
This definition is somewhat
ambiguous when it comes to assesing the risk of working with substances, as the 'belief' clause means full
safety measures should be taken even if the
risk is
unproven.
There are also different means of categorising carcinogens according to the risk they present. For instance the current
American Conference of Governmental Industrial Hygienists (
ACGIH) uses the following :-
A1 - Confirmed Human Carcinogen: The agent is carcinogenic to humans based on the weight of evidence from
epidemiological studies of, or convincing clinical evidence in, exposed humans.
A2 - Suspected Human Carcinogen: The agent is carcinogenic in experimental animals at dose levels, by route(s) of administration, at site(s), of
histologic type(s), or by mechanism(s) that are considered relevant to worker exposure. Available
epidemiological studies are conflicting or insufficient to confirm an increased risk of cancer in exposed
humans.
A3 - Animal Carcinogen: The agent is carcinogenic in experimental animals at a relatively high dose, by route(s) of administration, at site(s) of histologic type(s), or by mechanism(s) that are not considered relevant to worker exposure. Available epidemiological studies do not confirm an increased risk of cancer in exposed humans. Available evidence suggests that the agent is not likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure.
A4 - Not Classifiable as a Human Carcinogen: There is inadequate data on which to classify the agent in terms of its carcinogenicity in humans and/or animals.
A5 - Not Suspected as a Human Carcinogen: The agent is not suspected to be a human carcinogen on the basis of properly conducted epidemiological studies in humans.
As you can see the hazard and risk of working with a substance, with regards to it's carcenogenic properties, can be ranked from 'high' to 'none'. If you are working with a material that does not come with relevant hazard
data, you should ask your employer to obtain it, and use all necessary safety
protocols.
In the USA the
OSHA -
Occupational Health and Safety Administration produces a paper the '
Hazardous Communications
standard 1910.1200' to define the action
employers should take to protect
employees from any
risk due to
exposure. The most relevant sections of this document, with respect to carcinogens are as follows :-
(d)(4)
Chemical manufacturers,
importers and employers evaluating chemicals shall treat the following sources as establishing that a chemical is a carcinogen or potential carcinogen for hazard communication purposes:
(d)(4)(i)
National Toxicology Program (
NTP), "Annual Report on Carcinogens" (latest edition);
(d)(4)(ii)
International Agency for Research on Cancer (
IARC) "Monographs" (latest editions); or
(d)(4)(iii)
29 CFR part 1910, subpart Z, Toxic and Hazardous Substances,
Occupational Safety and Health Administration.
Note: The "Registry of Toxic Effects of Chemical Substances" published by the
National Institute for Occupational Safety and Health indicates whether a chemical has been found by NTP or IARC to be a potential carcinogen.
(d)(5)
The chemical manufacturer, importer or employer shall determine the hazards of
mixtures of chemicals as follows:
(d)(5)(i)
If a mixture has been tested as a
whole to determine its hazards, the results of such testing shall be used to determine whether the mixture is hazardous;
..1910.1200(d)(5)(ii)
(d)(5)(ii)
If a mixture has not been tested as a whole to determine whether the mixture is a health hazard, the mixture shall be assumed to present the same health hazards as do the components which comprise one percent (by
weight or
volume) or greater of the mixture, except that the mixture shall be assumed to present a carcinogenic hazard if it contains a component in
concentrations of 0.1
percent or greater which is considered to be a carcinogen under paragraph (d)(4) of this section