Entry into the marine environment
'Phthalates' is the generic name given to esters
of 1,2-benzenedicarboxylic acid. Although some 27
phthalate esters are manufactured, only a limited
number are produced in large quantities.
A review by Lewis et al (1998) identified
a number of phthalates of particular interest in
terms of their environmental fate and behaviour
or because they were on the High Production Volume
Chemicals List from the EC:
- dimethyl phthalate (DMP);
- diethyl phthalate (DEP);
- two isomers of dibutyl phthalate (DBPs);
- di-iso-butyl phthalate (DIBP) and di-n-butyl
- butylbenzyl phthalate (BBP);
- dicyclohexyl phthalate (DCHP) and three isomers
of dioctyl phthalate (DOP);
- di-n-octyl phthalate (DNOP), di-iso-octyl phthalate
(DIOP) and di-2-ethylhexyl phthalate (DEHP)
Phthalates are esters of 1,2-benzoldicarbonic acid
(ortho-phthalic acid). The chemical structure of
phthalates can be characterised by a planar aromatic
ring with two slightly mobile side chains. For phthalates,
in general, side chains are mainly alkyl groups
with a secondary role played by allyl, benzyl, phenyl,
cycloalkyl and alkoxy groups. With alkyl phthalates,
a further distinction can be made between branched
and unbranched side chains.
In the early 1980s, annual, world-wide production
of phthalate esters was estimated to be 20 million
tonnes (Schmitzer et al, 1988), although
it may now be closer to 5 million tonnes (Lewis
et al 1998). The total consumption of phthalate
esters in the UK was estimated to be 122,000 tonnes
in 1989, of which 54% was DEHP and DIOP (Brooke
et al 1991).
Phthalates esters are manufactured world-wide on
a large scale, being mainly produced for use as
plasticisers in resins and polymers, especially
as a softener in PVC (87% of the total production
of phthalates is used for this purpose).
Phthalate esters are widely distributed in the
environment because of their properties and their
common usage as plasticisers. Potential sources
by which phthalates may enter the aquatic environment
are widely thought to be through:
release via wastewater from production and processing
activities, including losses during phthalate ester
synthesis, resin and plasticiser compounding, fabrication
of PVC into products, and during the production
of adhesives and coatings;
release from use and disposal of materials containing
phthalate esters, including losses of plasticiser
during the lifetime of products or during incineration
or landfilling of refuse and other waste.
Recorded levels in the marine
Phthalates can be considered to be ubiquitous in
the environment and there are many studies which
have investigated and reported environmental concentrations
of these substances. While a few studies have been
carried out in the last few years, the majority
of available studies are between 10 and 20 years
old. Lewis et al (1998) have collated a number
of these studies which are summarised below.
It should be noted that contamination during collection
and analysis can lead to spurious results and recorded
environmental levels where due precautions have
not been taken may well be in error.
Data on the concentrations of phthalate esters
in environmental samples mainly focus on levels
of DEHP, reflecting its predominant usage. Reported
levels of DEHP in water samples from rivers in the
UK, Sweden, USA and the Netherlands are all within
the range 0.3 - 1.6 µg l-1(Fatoki
and Vernon 1990), with levels in coastal, marine
and estuarine waters between <2 ng l-1
and 335 ng l-1. DOPs are the
most hydrophobic of the phthalate esters on the
HPVCs List and have been detected in river-bed sediments
at concentrations between 0.1 - 1,700 mg kg-1,
depending on whether the samples were collected
from clean or contaminated sites. For example, contaminated
sediment collected from the Mersey Estuary contained
up to 1,700 mg kg-1 of DEHP (Preston
and Al-Omran 1986). It is likely that residues of
DOPs accumulating in sediments will persist and
that such sediments are a significant sink for those
long side-chain or highly branched side-chain phthalate
Sewage sludge is known to contain relatively high
concentrations of phthalate esters (12-1,250 mg kg-1;
Shelton et al 1984), the predominant component
being DEHP which accumulates on sludge solids because
of its hydrophobicity. The disposal of sewage sludge
to marine waters was an indirect route of phthalate
esters entering the environment, although the discharge
of sewage sludge to marine waters is a practise
which has been phased out under the Urban Waste
Water Treatment Directive (December 1998). The use
of sewage sludge as a soil conditioner in agriculture
is also a potential indirect route of phthalate
esters to the environment (Rogers 1987, Crathorne
et al 1989, Fairbanks et al 1985).
Fate and behaviour in the marine
Since some phthalate esters have low water solubility
and high octanol partition coefficient, they can
become concentrated in suspended matter and sediment.
Lewis et al (1998) reviewed data on the
fate and behaviour of phthalate esters. The authors
concluded that, in general, the substances have
low water solubilities and the majority are liquids
at ambient temperatures, with melting points below
0oC, although DMP and DCHP have melting
points of 5.5 and 63oC respectively.
Boiling points are 200OC and above.
The behaviour of phthalate esters in the environment
varies, depending on the individual ester. In general,
the larger the alkyl side-chain or degree of branching,
the more persistent the compound.
The most important aquatic degradation process
for phthalate esters is biodegradation. Short side-chain
phthalate esters, such as DMP, DEP and DBPs, are
all likely to degrade quickly in aerobic surface
waters. The longer chain PEs, such as DOPs, are
likely to be more persistent, particularly as they
will partition more strongly to sediments and so
may be less available to microbial degradation.
It is, therefore, probable that residues of DOPs
in anaerobic sediments will tend to persist for
Phthalate esters show a wide range of affinities
for partitioning to particulate materials in the
aquatic environment. Apart from DMP and DEP, all
other phthalate esters considered by Lewis et
al (1998) show significant partitioning to suspended
solids and sediments. The transport of DOPs, DBPs,
and BBP in the aquatic environment is strongly influenced
by their association with suspended sediments and
other detritus, as is their fate during sewage or
effluent treatment processes. Log Koc for the phthalate
esters increase in the order DMP<DEP<BBP<DNBP<DEHP<DNOP
and cover a wide range of hydrophobicities. DMP
has the lowest affinity for partitioning to particulate
materials and has the highest water solubility.
Partitioning tendency increases with side-chain
length, with DNOP having the greatest affinity for
suspended, particulate material in natural waters.
Consequently, the long side-chain phthalate esters
that enter the aquatic environment in effluent streams
are likely to show significant association with
suspended particulate material and sediments or
with particulates and sewage sludge during treatment
processes. In particular, longer chain phthalates
(e.g. DOPs) show a strong affinity for sewage sludge
which may reduce the likelihood of high concentrations
occurring in the effluent.
Phthalate esters have generally low volatility
(vapour pressures in the range 0.02 - 1.9 m Pa)
which decrease with increasing length of the alcohol
side-chain of the ester. Henry's
Law constants range between 10-8 and
10-5 atm m3 mol-1,
indicating that phthalate esters will tend to volatilise
from water, either not at all or very slowly.
DMP and DEP can be regarded as having low propensity
for bioaccumulation, whilst BBP and DBPs have intermediate
tendency. DEHP, DCHP, DNOP and DIOP all have a high
affinity for sediments or for partitioning to biota.
Effects on the marine environment
Toxicity to marine organisms
An exhaustive literature review on the toxicity
of phthalates 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 (Lewis et al 1998). The
most sensitive groups of organisms have been identified.
The toxicity of phthalates to saltwater organisms
varies, depending on the ester considered. Esters,
in general, appear to be of moderate to low toxicity
to aquatic organisms. However, greatest sensitivity
is exhibited when exposed to short side chain phthalate
esters, such as DBP and BBP.
For algae, respective EC50 (growth) and LC50 values
of 54 and 125 mg l-1 have been reported
for the diatom Gymnodinium breve following
96 hours exposure to DMP (Wilson et al 1978),
while 96 hour EC50s of 26.1 and 29.8 mg l-1
have been reported for Skeletonema costatum
on the basis of chlorophyll a and cell number respectively
(Suggat and Foote 1981, cited in Staples 1997).
For DEP, respective EC50 (growth) and LC50 values
of 3 and 33 mg l-1 have been reported
for the diatom Gymnodinium breve following
96 hours exposure (Wilson et al 1978).
For DBPs, the limited available data suggest that
saltwater algae are sensitive with 96 hour EC50
(growth) and LC50 values reported for the diatom
Gymnodinium breve ranging from 0.0034 - 0.2
and 0.002 - 0.6 mg l-1 respectively (Wilson
et al 1978). However, a single 96 hour EC50
(growth rate) of 31,000 mg l-1 DEHP has
been reported for the alga Gymnodinium breve
indicating low acute toxicity.
The available data suggest that DMP is of moderate
acute toxicity to crustacean species, with a 96
hour LC50 of 68.6 mg l-1 reported
for the mysid shrimp Mysidopsis bahia following
exposure to a measured concentration (Adams et
al 1995 and Suggat and Foote 1981, cited in
Staples 1997). This value is supported by a 96 hour
LC50 of 62 mg l-1 reported by Linden
et al (1979) for the copepod Nitocra spinipes.
DEP also appears to be of moderate acute toxicity
to saltwater crustaceans, with a 96 hour LC50 of
10.3 mg l-1 (measured concentration)
reported by Adams et al (1995) for the mysid
shrimp Mysidopsis bahia. Of somewhat lower
sensitivity is the brine shrimp Artemia salina
with a 72 hour LOEC (hatching) of 50 mg l-1
reported by Sugawara (1974). In this study, a corresponding
NOEC of 20 mg l-1 was reported.
However, greater sensitivity is exhibited by saltwater
invertebrates when exposed to DNBP and BBP.
24 hour LC50s of 5.6 and 8.9 mg l-1
for DNBP have been reported for the brine shrimp
Artemia salina exposed to nominal concentrations
in two separate studies (Hudson and Bagshaw 1978
and Hudson et al 1981). A lower 96 hour LC50
of 0.5 mg l-1 has been reported
for the mysid shrimp Mysidopsis bahia following
exposure to measured concentrations (Adams et
For BBP, a 96 hour LC50 of 0.9 mg l-1
has been reported by Gledhill et al (1980)
for the shrimp Mysidopsis bahia with a corresponding
NOEC of 0.4 mg l-1 measured
in this study. A further 96 hour NOEC of >0.9
mg l-1 has been reported in a similar
study (Adams et al 1995).
In studies conducted on the copepod Nitocra
spinipes and the mysid shrimp Mysidopsis
bahia no effects were observed below the maximum
water solubility of DEHP. L(E)C50 values for each
of these species were reported to be >0.37 and
>300 mg l-1 respectively following
96 hours exposure (Linden et al 1979 and
Adams et al 1995).
For saltwater fish, reliable 96 hour LC50s of 0.51,
3 and 0.55 mg l-1 BBP have
been reported for shiner perch Cymatogaster
aggregata, sheepshead minnow Cyprinodon variegates
and English sole Parophrys vetulus respectively
(Ozretich et al 1983; Gledhill et al
1980 and Randell et al 1983).
The limited available data for DMP suggest that
it is of moderate acute toxicity to saltwater fish,
with 96 hour LC50s of 29 and 58 mg l-1
reported in two separate studies for the sheepshead
minnow Cyprinodon variegates (Adams et
al 1995 and Heitmuller et al 1981). However,
a lower 96 hour LC50 of 107 mg l-1
(nominal concentration only) has been reported for
the bleak Alburnus alburnus (Linden et
al 1979), indicating a possible lower toxicity
to this species.
It is difficult to assess the toxicity of DBPs
to saltwater fish from the limited data available.
In a 96 hour study, no mortality of sheepshead minnow
Cyprinodon variegatus was observed at 0.6 mg l-1,
the highest concentration tested (Adams et al
1995). This is supported by the results of a long-term
study conducted on the eggs and larvae of a cyprinid
Rivulus marmoratus. In this study, 2-4 week
NOEC and LOEC values of 1 and 2 mg l-1
were reported respectively, on the basis of a decrease
in egg fertility and embryo viability.
A 96 hour NOEC (survival) of 550 mg l-1
has been reported for DEHP by Heitmuller et al
(1981) for sheepshead minnow Cyprinodon variegatus.
However, it is not possible to interpret this value
as it is well above the solubility limit of DEHP.
Similarly, no mortality was observed in the same
species following exposure to the highest concentration
tested (0.17 mg l-1) (Adams et al
Sediment dwelling organisms
Some information on the toxicity of phthalate esters
to sediment dwelling organisms is available. However,
these are for freshwater organisms.
Given the low water solubility of DEHP and its
high octanol-water partition coefficient, it is
likely that this compound will readily adsorb to
suspended solids and sediments in the natural environment.
Streufert et al (1980) found that in a flow-through
study utilising DEHP concentrations of 0.36 mg l-1
over sand and 0.24 mg l-1 over
hydrosoil, no effects were observed on the larvae
of Chironomus plumosus over a 35 day
exposure period. Adsorption of the dissolved fraction
to the sand/hydrosoil may have reduced bioavailability
and hence toxicity. This observation is supported
by the results of the following sediment studies.
In a study utilising spiked river sediments, a NOEC
of >10,000 mg kg-1 (survival, development
and emergence) was measured for larvae of the midge
Chironomus riparius (Brown et al 1996).
The authors found that this value was seventeen
times greater than the highest concentrations measured
in contaminated sediments in the natural environment.
These results are supported by the findings of Call
et al (1997) who found that spiked sediment
concentrations of 3,306 and 3,247 mg kg-1
(dry weight) caused no adverse effects on survival
or growth of the midge Chironomus tentans
or scud Hyallela azteca respectively, over
a period of 10 days.
In a study conducted by Wennberg et al (1997),
a concentration of 600 mg kg-1 (spiked
sediments) was found to cause no adverse effects
on hatching success or tadpole survival in the moor
frog Rana arvalis over a 29 day period.
Lewis et al (1998) derived EQSs for the
protection of saltwater life for a range of phthalate
esters (see table below).
Proposed EQSs for the protection of saltwater
life for phthalates (µg
l-1) (from Lewis et al 1998)
Maximum allowable concentration
1 Tentative standard
2 Total DBPs (DIBP; DNBP)
3 DOPs (DEHP, DIOP, DNOP)
4 Insufficient data to derive standards
Bioaccumulation of phthalate esters does not appear
to be significant. Wofford et al (1981) exposed
the oyster Crassostrea virginica, brown shrimp
Pennies aztecus and sheepshead minnow Cyprinodon
variegatus to concentrations of 0.1 and 0.5 mg l-1
(DEHP). Bioaccumulation did not vary significantly
among the three species, with reported BCFs ranging
from 6.9 (oyster) to 16.6 (shrimp), although exposure
was for 1 day only. In longer term studies, Brown
and Thompson (1982) recorded an average BCF of 2,496
for mussels (total soft tissues), following 28 days
exposure to concentrations of 0.004 and 0.042 mg l-1.
No apparent adverse effects on the mussels were
observed, and accumulated residues were rapidly
eliminated following transfer to clean seawater
(half-life = 3.5 days). It should be noted that,
since the BCFs were based on 14C levels,
the values might also include metabolites of DEHP.
Wofford et al (1981) determined BCFs for
the brown shrimp Pennies aztecus and sheepshead
minnow Cyprinodon variegatus for other phthalate
esters, but found them to be low (<50).
Potential effects on the interest
features of European marine sites
Potential effects include:
- toxicity of phthalates at concentrations above
the relevant EQSs in the water column;
- accumulation in sediments of long side-chain
or highly branched side-chain phthalate esters
(e.g. DOPs) posing a significant hazard to sediment
- phthalate esters have been identified as a group
of substances causing endocrine disruption and
a precautionary approach should be adopted in
the control of these substances.