Toxicology of Industrial Compounds

346 TOXICOLOGY OF SURFACTANTS
nonionic>anionic>cationic surfactants (Draize and Kelley, 1952; Hazleton,
1952; Grant, 1962).
Sensitization
Aside from acute irritation, chemical substances can cause allergies after
contact with the skin or a mucous membrane. The development of an
allergy is dependent on certain preconditions. An essential factor is the
individual disposition which is predominantly genetically determined. An
additional important point is the extent of damage to the tissue at the point
of contact of the chemical substance (inflammation), which promotes
sensitization. In addition, the sensitization potential of a substance is of
decisive importance. For products with low molecular weights, this
potential is dependent on their chemical properties. Small molecules are by
themselves not able to trigger a reaction of the immune system. They
become immunologically active only after binding to endogeneous
proteins. Since the majority of the surfactants can only form weak and
reversible bindings via hydrophobic and electrostatic interactions, this
prerequisite is not fulfilled.
Once the organism is sensitized towards a certain chemical, renewed
contact with trace amounts of this material can provoke allergic reactions,
which especially affect the skin and respiratory tract. Typical symptoms are
itching, eczema, exanthema, rhinitis and bronchial asthma.
Anionic surfactants and surfactant containing products were tested for
sensitizing properties by numerous laboratories (Götte, 1967; Kästner,
1980; Siwak et al., 1982) without detecting any significant increase in risk.
The same holds true for nonionic surfactants (Siwak et al., 1982). Some
cationic surfactants, which are able to form stable complexes by the
formation of ion pairs with anionic groups of proteins, proved to be
allergenic (Schallreuter and Wood, 1986).
Toxicokinetics
Percutaneous absorption
The most important exposure of humans occurs through the skin with the
use of cosmetics and toiletries. The skin comes in contact with surfactants
also during dishwashing or when washing hands. Since these products are
used over a long period of time, possible long-term effects must be
evaluated. Measurement of percutaneous absorption of surfactants is
important because it provides data for the toxicologist concerning the
amount of surfactants which could enter the body through the skin in the
most unfavourable case. Together with other toxicological information,