Toxicology of Industrial Compounds

344 TOXICOLOGY OF SURFACTANTS
problem of labelling chemical products with respect to their toxicological
properties has to be addressed. Different national or international
regulations, e.g. the EG directive 67/548 within the European Community,
dictate that these products are labelled ‘irritating’ or ‘corrosive’ whenever
exactly defined effects are observed in appropriate tests. With consumer
protection in mind, exceedingly stringent test procedures have been
established. These conditions frequently result in an unfavourable
classification especially for surfactants. When interpreting data from such
studies, it is important to consider that unrealistic conditions of exposure
were involved.
Since anionic surfactants are the class with the greatest economic
importance, they are the best studied. No general statement is possible with
regard to a classification of the various groups of anionic surfactants in
order of their skin compatibility, since within each class of substances
significant differences exist in their effect on skin depending on the
respective structure. Opdyke et al. (1965), for example, found a decrease in
the skin irritation potential of different alkyl ether sulphates with
increasing level of ethoxylation. The effect of the alkyl chain length of
anionic surfactants was examined in different test models for soaps, alkyl
sulphates, alkyl sulphonates, alkylbenzene sulphonates as well as alphaolefin
sulphonates (Kästner, 1980). As shown in Table 24.1, it could be
established in all cases that compounds with a saturated side chain of 10–
12 C atoms exert the largest effect, or rather, have the highest potential for
damage. When the results of skin compatibility tests for the most
important classes of anionic surfactants are summarized, it becomes
evident that the undiluted products have to be regarded as strongly
irritating substances. Even at concentrations of 10 per cent moderate to
strong effects have to be expected. However, at concentrations less than 1
per cent, which is the range corresponding to typical use levels in
detergents, only minimal irritation is observed.
Nonionic surfactants have a good skin compatibility at normal use
levels. Although studies with alcohol ethoxylates were reported in which a
strong irritant effect was observed (Grupp et al., 1960), these studies used
concentrations far above the usual exposure levels of consumers.
Independent of their structure, cationic surfactants cause severe skin
damage in high concentrations, while typical application levels are
generally tolerated well.
Mucous membrane compatibility
When talking about mucous membrane compatibility one has to consider
not only the mucous membranes of the eye. In addition, the mucous
membranes in the mouth, upper and lower gastrointestinal tract as well as
the urogenital tract have to be considered. In general, the effects of