Entry into the marine environment
Surfactants (also called surface active agents
or wetting agents) are organic chemicals that reduce
surface tension in water and other liquids. The
most familiar use for surfactants are soaps, laundry
detergents, dishwashing liquids and shampoos. Other
important uses are in the many industrial applications
for surfactants in lubricants, emulsion polymerisation,
textile processing, mining flocculates, petroleum
recovery, wastewater treatment and many other products
and processes. Surfactants are also used as dispersants
after oil spills.
There are hundreds of compounds that can be used
as surfactants and are usually classified by their
ionic behaviour in solutions: anionic, cationic,
non-ionic or amphoteric (zwiterionic). Each surfactant
class has its own specific properties.
There are many sources of surfactants that are
discharged into natural waters. Industrial sources
include textile, surfactants and detergent formulation.
Surfactants are also used in laundries and households
and are therefore found in discharges from sewage
treatment works. They also have agricultural applications
in pesticides, dilutants and dispersants (McNeely
et al 1979).
Surfactants are compounds composed of both hydrophilic
and hydrophobic or lipophobic groups. In view of
their dual hydrophilic and hydrophobic nature, surfactants
tend to concentrate at the interfaces of aqueous
mixtures; the hydrophilic part of the surfactant
orients itself towards the aqueous phase and the
hydrophobic parts orients itself away from the aqueous
phase into the second phase.
The hydrophobic part of a surfactant molecule is
generally derived from a hydrocarbon containing
8 to 20 carbon atoms (e.g. fatty acids, paraffins,
olefins, alkylbenzenes). The hydrophilic portion
may either ionise in aqueous solutions (cationic,
anionic) or remain un-ionise (non-ionic). Surfactants
and surfactant mixtures may also be amphoteric or
zwitterionic (CCME 1992).
The table below gives some examples of major commercial
and industrial surfactants.
Nonylphenol and its ethoxylates (NPEs) are one
of the types of surfactants causing concern. The
primary source of nonylphenolic compounds in the
aquatic environment is due to the incomplete degradation
of NPE (nonylphenol ethoxylate) surfactants during
sewage treatment, and therefore it is unlikely to
be present in the aquatic environment in the absence
of other NPE degradation by-products (such as nonylphenol
mono- and diethoylates (NP1EO and NP2EO) and nonylphenoxy
carboxylic acids (NPEC)).
Some examples of major commercial and industrial
surfactants (from CCME 1992)
and domestic examples
linear alkylbenzene sulphonate (LABS); sodium
lauryl sulphate; sodium lauryl ether sulphates
sulphonates; linosulphonates; naphthalene sulphonates,
branched alkylbenzene sulphonates; linear alkylbenzene
sulphonates; alcohol sulphates
chloride; benzalkonium chloride
ammonium compounds; amine compounds
dimethylamine oxide; coco diethanol-amide alcohol
ethoxylates; linear primary alcohol polyethoxylate
ethoxylates; alcohol ethoxylates; EO/PO polyol
block polymers; polyethylene glycol esters;
fatty acid alkanolamides
Recorded levels in the marine
Concentrations of nonylphenol in surface waters
vary widely but locally high concentrations (sometimes
in excess of 100 µg l-1) have
been reported, especially in areas receiving industrial
and sewage discharges. Higher concentrations (several
mg kg-1) have been detected in sediments,
although much of this is unlikely to be bioavailable
(Whitehouse et al 1998a).
Fate and behaviour in the marine
In view of their hydrophilic nature, surfactants
tend to be water soluble to some degree. Depending
on the specific chemicals, solubility varies from
very soluble (e.g. some anionic surfactants) to
insoluble (e.g. some cationic surfactants) (Lewis
and Wee 1983) .
Anionic surfactant are not appreciably sorbed by
inorganic solids. On the other hand, cationic surfactants
are strongly sorbed by solids, particularly clays.
Significant sorption of anionic and non-ionic surfactants
has been observed in activated sludge and organic
river sediments. Depending on the nature of their
hydrophobic moieties, non-ionic surfactants may
be sorbed onto surfaces. Some surfactants have been
found to alter the sorption to surfaces of coexisting
chemical species, such as metals (CCME 1992).
In general, surfactants in modern day use are considered
to be biodegradable under conditions of efficient
sewage treatment, The rates of degradation depend
partially on the chemical structure. Surfactants
containing linear hydrophobes are generally more
biodegraded than those containing branched hydrophobes.
Nonylphenol and some of its ethoxylates are not
readily degraded during sewage treatment (CCME 1992).
Because of the hundreds of compounds that can be
used as surfactants and because the toxicity (and
potential to be present in sediment) and bioaccumulation
potential will vary according to the type of surfactant,
an assessment is not possible here.
Effects in the marine environment
Toxicity to marine organisms
An exhaustive literature review on the toxicity
of surfactants to marine organisms has not been
carried out for the purposes of this profile. The
information provided in this section is taken from
existing review documents for one surfactant (nonylphenol)
as an example (Whitehouse et al 1998a). The
most sensitive groups of organisms have been identified.
Whitehouse et al (1998a and 1998b) reviewed
data on the saltwater toxicity of nonylphenol and
octylphenol. By way of an example, their conclusions
for nonylphenol are presented below.
The authors reported that, in acute studies with
saltwater species, the mysid shrimp Mysidopsis
bahia was the most sensitive species, where
a 96 hour LC50 of 43 µg l-1
was reported. Corresponding 96 hour LC50s values
for fish were higher, ranging from 135 µg l-1
for fathead minnow Pimephales promelas to
3,000 µg l-1 for cod Gadus
morhua. Nonylphenol was generally toxic to algae
at concentrations greater than 500 µg l-1
although the lowest 96 hour EC50 (for growth) was
27 µg l-1 in the
marine diatom, Skeletonema costatum.
Some toxicity data for sediment-dwelling organisms
were also presented (although it relates to freshwater
organisms). Whitehouse et al (1998) found
nonylphenol dosed into sediment would not be readily
bioavailable. Much higher levels of nonylphenol
were required in sediment than in water to cause
adverse effects to the sensitive midge larvae Chironomus
Whitehouse et al (1998a) also investigated
data on the endocrine disrupting effects of nonylphenol.
While no data were available for saltwater organisms,
nonylphenol concentrations of 20 µg l-1
and greater were found to cause effects related
With regard to bioaccumulation, Whitehouse et
al (1998a) found bioaccumulation factors for
aquatic organisms to be around 300. However, much
higher values were found for algae (but this may
have been due to adsorption) and when radio-labelled
nonylphenol was used.
Potential effects on interest
features of European marine sites
Potential effects include:
- toxicity of nonylphenol and octylphenol to algae,
invertebrates and fish at concentrations above
the respective EQSs of 1 microg l-1
(annual average) and 2.5 microg l-1
(maximum allowable concentration) for nonylphenol
and 1 microg l-1 (annual average) and
2.5 microg l-1 (maximum allowable concentration)
for octylphenol in the water column;
- accumulation of nonylphenol in sediments though
bioavailability is considered to be low;
- nonylphenol has been found to have endocrine
disrupting effects in freshwater organisms at
concentrations of 20 microg l-1.