Combined Actions and Interactions of Chemicals in Mixtures

4.6 Approaches currently used by regulatory agencies in Denmark
4.6.1 Danish Working Environment Authority
When several substances are present at the same time at the work place, they may
have an over-all intensifying (synergistic) or weakening (antagonistic) effect, or the
interaction may be additive. Limited information and data are available (in the
literature) and the Danish Working Environment Authority requires the following
procedure in controlling combined exposure:
If no specific information on the interaction of the substances is available, at least
an aggregate (additive) effect should be considered. The following formula is used
when calculating the aggregate effect:
C1 / GV1 + C2 / GV2 + C3 / GV3 + … + Cn / GVn
Where C is the concentration in the air of the respective substances, and GV is the
corresponding exposure limit values. A fraction sum of 1 corresponds to the
exposure limit value for the aggregate effect/combination of substances.
This formula is not normally applied to combination of benzene and
tetrachloromethane, and lead and sulphuric acid (At-Guideline C.0.1 2000).
4.6.2 The Danish Environmental Protection Agency
In the harmonized EU-regulation for classification and labelling the classification
of preparations (chemical mixtures) is based on the classification of the single
chemical substance where the content of the substances classified for the same
harmful effect (acute toxicity and irritation) are summarised i.e. the preparations
are classified in accordance with the principle of additivity of similar effects.
Furthermore substances and preparations (mixtures) may be classified as corrosive
due to their physical-chemical properties on the basis of the pH value and the
acidic or basic capacity.
With respect to classification and labelling for other specific effects such as
sensitizing effects, reproductive, mutagenic and carcinogenic effect the
classifications depends on specific concentration limits of the single substances and
thus no addition of contents is made.
For some substances i.e. oil- and coal derived substances where each substance
comprises of a great amount of constituents a specific amount of a specific
indicator have been chosen (e.g. the content of benzene, 1,3-butadiene,
benzo[a]pyrene and the DMSO extractable fraction) to decide whether the complex
substance should be classified as carcinogenic or not.
With respect to harmful effects in connection with aspiration risk to the lung after
ingestion, the oil-/coal- derived substance (or preparation) is classified according to
physical-chemical properties with regard to its flow rate and viscosity.
In the guidelines for regulation of air emission the regulation is mainly based on
the tolerable outdoor air concentrations for the single substances (Danish EPA
2002). However, some considerations have been made in connection with
simultaneous emission of multiple substances and from an operational point of
view the following is recommended:
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