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Abstract

The effect of cationic surfactants as fabric softening agents on water pollution is discussed. The softening agents are shown to be moderately persistant and very toxic in an aquatic environment. It is concluded that Dutch waters are critically contaminated with cationic surfactants.
Chemosphere, Vol. 24, No.5, pp. 629-639, 1992 0045-6535/92 $5.00 + 0.00
Printed in Great Britain Pergamon Press plc
ECOTOXICOLOGICAL RISK EVALUATION OF THE CATIONIC
FABRIC SOFTENER DTDMAC. HI.
RISK ASSESSMENT
Kees van Lceuwen ~, Carla Roghair b, Ton de Nijs b and Jodi de Greef ~
"Directorate-General for Environmental Protection,
P.O. Box 450, 2260 MB Leidschendam, The Netherlands
bNational Institute of Public Health and Environmental Protection,
P.O. Box 1, 3720 BA Bilthoven, The Netherlands
ABSTRACT
The use of cationic surfactants in the Netherlands (about 2500 tonnes as active
ingredient on an annual basis) poses a serious risk to a wide variety of aquatic ecosystems.
On the basis of ecotoxicological studies with ditallow-dimethyl-ammoniumchloride
(DTDMAC), the most important fabric softener, a maximum permissible risk level of 50 ~tg/1
and a negligible risk level of 0.5 ~tg/l have been derived. In 1990, concentrations of 6 - 25
~tg/1 were measured in the rivers Rhine, Meuse and Scheldt. Model predictions, confirmed by
measurements in Germany and The Netherlands, show that in approximately 30 to 40% of
the surface waters considerably higher DTDMAC are expected to occur. On the basis of this
risk evaluation, which was discussed in the Dutch Parliament in spring 1990, the Netherlands
Association of Detergent Industries agreed to replace DTDMAC by chemicals of lower
environmental concern within a period of two years. Already by the end of 1990 almost all
DTDMAC had been replaced by readily biodegradable substitutes. However, in June 1991,
DTDMAC was detected in the rivers Rhine, Meuse and Scheldt at concentrations between 12
and 34 ~tg/l, which indicates that other than only national measures are required to reduce the
large-scale pollution of surface waters with DTDMAC.
KEYWORDS Surfactant; quaternary ammonium compounds; toxicity; fate
INTRODUCTION
Tile cationic suffactants used in fabric softeners are mainly quaternary ammonium
compounds such as distearyl-dimethyl-ammoniumchloride (DSDMAC), ditallow-dimethyl-
ammoniumchloride (DTDMAC), hardened ditallow-dimethyl-ammoniumchloride and cetyl-
629
630
trimethyl-ammoniumchloride. These technical-grade products may contain impurities such
as mono- and trialkyl ammonium compounds [1]. The cationic surfactants chiefly used in
fabric softeners are DSDMAC and DTDMAC. In the Netherlands about 2500 tonnes of these
surface-active agents are used every year. The bulk of it is discharged into sewage water, of
which over 90% is purified in sewage treatment plants (STPs).
Owing to their strong adsorption onto minerals and organic matter, cationic surfactants
are eliminated from the water phase. It is estimated that in STPs about 90% settles in the
active sludge [1,2]. In laboratory tests the substances decompose; however, their rate of
decomposition greatly depends on the presence of sediment. Probably none of the compounds
is truly persistent, but their degradation is likely to be slow in surface water, where the
concentrations are generally lower than those used in laboratory biodegradation tests. Studies
with similar cationic surfactants have led to the conclusion that degradation will probably fail
to occur in surface water which is hardly contaminated by waste water, i.e. surface water
which has not been adapted [1]. No data are available on their anaerobic degradation in
aquatic sediments.
In order to reduce the uncertainties in effects assessments for these quaternary
ammonium compounds reported in earlier studies [1,2], additional research has been carrried
out at the National Institute of Public Health and Environmental Protection, focusing on
DTDMAC as representative of this group of chemicals. This additional research was the
outcome of risk management discussions between the Netherlands Association of Detergent
Industries and the Minister of Housing, Physical Planning and the Environment.
The present paper summarizes this additional research into (a) the modelling of
concentrations of cationic surfactants in effluents of STPs and surface waters in the
Netherlands, (b) the chemical analyses of DTDMAC in effluents, sewage sludge and surface
waters, and (c) the ecotoxicological effects of DTDMAC.
MATERIAL AND METHODS
Environmental concentrations of DTDMAC.
The prediction of cationic surfactant concentrations is based on a recent study of the
dilution of effluents from STPs in surface waters in the Netherlands [3]. In this study dilution
factors are calculated for 467 STPs, which have been used to predict the concentrations of
cationic surfactants in effluents of STPs and in surface water at distances of 100 and 1000
metres downstream from the discharge points [4]. It was assumed that the annual use of
DTDMAC in the Netherlands is 2000 tonnes and that the elimination rate of DTDMAC in
STPs is 90% [2]. Apart from predicting environmental concentrations of DTDMAC, some
actual measurements of D'I'DMAC in effluents and surface waters were carried out using
HPLC as analytical technique.
Ecotoxicological studies
Additional ecotoxicological research was carried out with DTDMAC. The product,
provided by Proctor and Gamble, consisted of 77% DTDMAC, 1.7% monotallow trimethyl
ammonium chloride (MTFMAC) and 13.3% isopropanol solution in water. M'ITMAC is a
contaminant which is considerably more toxic than DTDMAC but which degrades more
rapidly [1]. The experiments were carried out in coarsely filtered (50 ~tm) surface water with
a suspended matter content of approximately 1-4 mg/1. This is an important detail because
the presence of suspended matter in surface water may reduce the toxicity of DTDMAC [2].
The experiments were carried out with the stickleback
(Gasterosteus aculeatus),
midge larvae
(Chironomus riparius),
the snail
Lymnaea stagnalis,
the green alga
Scenedesmus pannonicus
and bacteria
(Photobacterium phosphoreum
and nitrifying bacteria). The tests with P.
phosphoreum
(the Microtox test) were carried out in salt water as well as in an isotonic
sucrose freshwater solution. Details of these aquatic toxicological studies are given in Roghair
et al. [5].
631
RESULTS AND DISCUSSION
Concentrations of DTDMAC in surface waters
The calculated dilution factors are shown in Table I. The extensive evaluation of De
Nijs and De Greef [3] shows that in approximately 10% of the STP effluents in Dutch surface
waters there is little or no dilution of treated effluent. For approximately 20-30% of the
effluents tile dilution factor is less than 5, while in the remaining 70-80% the dilution factor
is greater than 5. From this study it may be concluded that higher dilution factors can only
be expected for the major rivers.
Table I - Median dilution factors (DF) for effluents from 467 sewage treatment plants in The
Netherlands in various types of surface waters. The median values have been calculated at
100 m and 1000 m from the discharge points [3].
Water Type Dilution factor at Fractions DF <5 at
100 m 1000 m 100m 1000m
polder water 5 6 0.53 0.47
boezem water 7 13 0.44 0.13
canal 18 25 0.22 0.20
major river 1830 1830 0.00 0.00
river 28 50 0.19 0.06
tributary/pond 6 6 0.48 0.46
632
The median cationic surfactant concentration in effluents has been estimated at 255
p.g/l (Fig. 1). The average estimated influent concentration at an elimination efficiency of
90% is higher, i.e. 2550 ~g/1. These estimations correspond well to the actual concentrations
of 1400-3100 Ixg/1 which have been found in STP-influents in Great Britain and Belgium [2].
Concentrations ranging from 375 to 4300 Ixg/1 were measured in STP-influents at Bilthoven
and at Hazerswoude (The Netherlands). The predicted STP-effluent concentrations appear to
correspond reasonably well to measured data. According to recent analyses concentrations of
50 ~tg/1 have been found in effluents of STPs in Germany; in Belgium concentrations of 45
Ixg/l have been measured [2], while in the Netherlands DTDMAC has been detected in STP-
effluents at concentrations ranging from 11 to 55 ~tg/1. On the basis of these few mea-
surements it can be concluded that the actual elimination efficiency due to adsorption and
(bio)degradation in STPs is greater than 90% and even likely to be between 90-99%. In our
calculations, however, an elimination rate of 90% was assumed.
The predicted environmental concentrations for cationic surfactants in the surface
waters of the Netherlands are shown in Fig. 2. A few comments must be made. Firstly, it
should be noted that these figures stand for total concentrations, i.e. no distinction has been
made between the dissolved and the adsorbed fractions. Secondly, it is assumed that STP-
effluents are continuously discharged and that in most surface waters in the Netherlands
transverse mixing is not completed at distances of 1000 metres from the points of discharge
[3]. Thirdly, degradation and sedimentation in surface water have not been taken into account
nor have initial concentrations of cationic surfactants (i.e. the concentration of cationic sur-
factants already present in surface waters was assumed to be 0 ~tg/1). Finally, it was assumed
that 100% of the cationic surfactants used in The Netherlands is discharged into STPs via
domestic waste water.
A comparison of these concentrations with those determined by Kappeler [6] in
Germany at 30 points along the Rhine and its tributaries, where he found concentrations of
4-92 ~tg/l, shows that our model calculations closely correspond to his measured data. In
larger bodies of water Kappeler found concentrations of less than 15 I.tg/1. These values, too,
come very close to the concentrations measured in the major rivers of The Netherlands (Table
II). Surprisingly, all DTDMAC concentrations measured in 1991 appear to be higher than the
ones measured in 1990. This cannot be explained by the lower discharges of the larger rivers.
Concentrations in suspended matter, sewage sludge and aquatic sediments
Besides cationic surfactant concentrations in surface waters, it is also possible to
calculate cationic surfactant concentrations in suspended matter, sewage sludge and aquatic
sediments, using the equilibrium-partitioning theory for sediment or suspended matter and
water [7]. The sediment-water partition coefficient (K~) required for these calculations can
be derived from the experimental data obtained by Klotz [8] for the river Main (Germany):
K,w =
8.5
X 10 4
l/kg. Assuming this, as well as a STP-effluent concentration of 100/xg/1
633
(dissolved) and a suspended matter content of 30 mg/1, a cationic surfactant concentration of
approximately 8.5 g/kg (dry matter) can be calculated for suspended matter and sewage
sludge.
180
(D
"6
=E
z
Legenda
160 ~ tributary
river
140 major river
120 ~ canal
I~ boezem
100 polder
80 Med: 255jug/I
6O
4O
0
40 93 123 162 214 283 373 492 650 858
Concentration [/ug/I]
Fig. 1. Histogram of predicted DTDMAC concentrations in effluents of sewage treatment
plants in The Netherlands, calculated after [3,4].
120
0
E
100
80
60
40
20
Legenda
tributary
river
major river [~
canal
boezem
polder
0.00 0.01
0.02 0.05
0.14 0.41 1.18 3.4 10.0 28.9 84.0 244
707
Concentration [jug/I]
Fig. 2. Histogram of predicted DTDMAC concentrations in surface waters in The Netherlands
1000 m downstream of sewage treatment plants, calculated after [3,4].
634
Assuming a concentration of 10 ~tg/1 (dissolved) in surface water, a cationic surfactant
concentration of 570 mg/kg can be calculated for aquatic sediments. It should be noted that
the partition coefficient may vary with the composition of the suspended matter.
Measured data for cationic surfactants in sewage sludge have recently become
available. In the STP of Koblenz (Germany) DSDMAC concentrations varying from 8.9 to
9.2 g/kg have been measured [9]. These values closely correspond to the above calculated
concentrations in sewage sludge.
Table II - Measured DTDMAC concentrations in surface waters in The Netherlands.
Location Concentration (~tg/1)
March 1990 April 1990 June 1991
Eysden (Meuse) 17 25 25
Lobith (Rhine) 6 6 21
Nieuwegein (Lek) 7 7 12
Keizersveer (Meuse) 5 4 16
Bath (Scheldt) 6 - 34
Zandvlietsluis (Scheldt) 2 - 5
Ecotoxicity of
DTDMAC
The results of the ecotoxicological study done by Roghair et al. [5] combined with the
results of [2] and [10] are shown in Table III. It should be noted that the no observed effect
concentrations (NOECs) are nominal concentrations which have been corrected for the
DTDMAC content of the technical-grade product. The table also shows the values used for
the ecotoxicological risk assessment, which methods are briefly explained below. The results
show that the algae species (M.
aeruginosa, S. capricornutum and N. seminulum)
are the most
sensitive and the bacteria the least sensitive. The differences in toxicity to the fish species G.
aculeatus
and
P. promelas,
the midge larva
C. riparius,
the crustacean
D. magna
and the
water snail
L. stagnalis
are very small. This small difference in sensitivity among the species
is the most notable result.
All the tests done with surface water (Table III, sets A and B) produced higher NOEC
values than the tests done with standard water without sediment (set C). This can easily be
explained by the adsorption of cationic surfactants to suspended matter which results in a
reduced biological availability. The same has been observed in a study by Lewis and Wee
[10] who demonstrated a variation in toxicity to algae of 200-2600 vtg/l due to varying
amounts of suspended matter in the water, as well as by Pittinger et al. [11]. Therefore, by
carrying out research with surface water containing suspended matter, the reduced biological
availability is accounted for. In this way the possible reduction in toxicity of cationic
surfactants by anionic surfactants [1] is also taken into account.
The results of the tests with the midge larva
C. riparius
closely correspond to the
results of tests carried out with the same organism by Pittinger et al. [11]. They found a
NOEC of 0.45 mg/l for DSDMAC in spring water.
Ecotoxicological risk assessment
The data presented in Table III were used to calculate the maximum permissible risk
level and the negligible risk level for DTDMAC according to five different risk assessment
methods. The results of these calculations are shown in Table IV.
The risk assessment methodologies and management philosophies for the protection
of man and the environment in The Netherlands have been published in the national policy
document "Premises for Risk Management" [13]. The objective for the so-called general
635
environmental quality is to offer protection to 95% of the species in ecosystems. This
percentage has been arbitrarily chosen and implies that 5% of the species may suffer
detrimental effects at this maximum permissible risk level. The negligible risk level is set at
1% of the maximum permissible risk level. Furthermore it is assumed that by protecting the
structure of ecosystems (i.e. the qualitative and quantitative distribution of species) their
functional characteristics will also be safeguarded [13].
Method 1. This method is used in Germany and has been applied for the ecotoxicolo-
gical risk assessment of linear alkylbenzene sulphonate [14]. The method is simple and
basically entails applying a safety factor of 10 to the lowest NOEC. It is also used by the US
EPA to calculate "concern levels" [15], i.e. concentrations of substances in the environment
which if exceeded would mean an unacceptable risk to the aquatic environment.
Table III - NOEC values (rag/l) used to calculate maximum permissible risk levels and
negligible risk levels for DTDMAC according to various risk assessment methods a. The data
derived from Roghair et al. [5] are nominal concentrations expressed as the active ingredient
and indicated by an asterisk (*). The remaining data are taken from [2] and [10].
Species Set A Set B Set C
Gasterosteus aculeatus
0.58* - -
Pimephales promelas c
0.23 0.23 0.053
Chironomus riparius
1.03" 1.03" -
Daphnia magna c
0.38 0.38 -
Lymnaea stagnalis
0.25* 0.25* -
Scenedesmus pannonicus
0.58* 0.58* -
Selenastrum capricornutum
0.71 d - 0.020 b
Microcystis aeruginosa
0.21 d 0.2U 0.017 b
Navicula seminulum
- - 0.023 b
Photobacterium phosphoreum
4.27* - -
Nitrifying bacteria 2.31" 2.31" -
"Set A was used for the maximum permissible risk level and negligible risk level calculations
using methods 1, 2 and 3. Set B was used for risk assessment method 4 as described in [12].
Set C was used for the risk assessment according to method 2 [7].
bNOEC values for algae were obtained from the EC50 values devided by a factor 3.
¢NOECs are based on measured concentrations of DTDMAC in water. The test with D.
magna
was carried out with DSDMAC.
O~his is an algistatic concentration. The actual NOEC value is therefore lower.
Table IV - Maximum permissible risk levels (MPRs) and negligible risk levels (NRs) for
DTDMAC calculated using the data in Table III. NR is 1% Of MPR [13]. Values are given
in ~tg/l and represent "total" concentration of DTDMAC in surface water.
Method MPR NR
[1] Hansen/U.S.EPA [14,15]
[2] Van Der Kooy et al. [7]"
[3] Van Straalen and Denneman [16]
[4] Van De Meent et al. [12] b
[5] Van De Meent et al. [12] b
21
16
63
27-100
18-90
0.21
0.16
0.63
0.27-1.0
0.18-0.9
636
'A suspended matter content of 30 mg/l, a K~ of 8.5 x 104 l/kg and a correction factor of 0.8
for combined toxicity were used. As dissolved concentrations were not determined in the
tests with algae, the lowest NOEC from the study was divided by 3 for the calculations.
~"he interval represents the confidence interval of the calculated 95% protection level of the
species. The upper limit.is the median value. The lowest value represents the lower limit of
the 95% confidence interval.
Method 2. This method is used by the Dutch Ministery of Transport and Public Works.
It is applied to the lowest NOEC (expressed as dissolved concentration) obtained from
experiments carried out with at least the following group of species: fish, crustacea, molluscs
and algae. If nominal concentrations rather than measured concentrations are given the NOEC
should be corrected for this. The combined toxicity of similar substances should also be taken
into account. The "dissolved" concentrations in water are then converted to "total"
concentrations (dissolved + adsorbed), assuming a suspended matter concentration in surface
water of 30 mg/1 and an experimental or estimated sediment-water partition coefficient [7].
The following methods (3, 4 and 5) are used by the National Institute of Public Health
and Environmental Protection [12].
Method 3. This is the Van Straalen and Denneman method [16], which was also
reviewed by the Health Council [17] and proposed in Premises for Risk Management [13].
According to this method the 95% protection level for species is calculated on the basis of
a random sample, i.e. a limited number of tested species, on the assumption that the dis-
tribution of species sensitivity can be described by a log-logistic distribution.
Method 4. This is Van Straalen and Denneman's method as modified by Van de
Meent et al. [12]. In this method the 95% protection level of the species is calculated using
Baysian statistics. This method, which is described in more detail in [12], also provides an
estimate of the confidence limits of the 95% protection level. This interval is bounded by the
50% (median) value which represents the most likely estimate of the 95% species protection
level. The lower limit represents the lower value of the 95% confidence interval of the 95%
species protection level.
Method 5. This method is described in detail in [12]. It differs from method 4 only
in that the input data are selected as follows:
- if more than one toxicity study is done with the same species and different
toxicological parameters, the lowest NOEC is used;
-
if several toxicity studies are done with the same species and the same toxicological
parameters, the geometric average of these values is used;
- the lowest NOEC for each taxonomic group (fish, insects, crustaeea, mollusca, green
algae, blue-green algae and bacteria, etc.) is used.
Remarks on the calculations
The previous publication on cationic surfactants [1] promised to provide further details
on various aspects of ecotoxicological risk assessment of fabric softeners. Since then a great
deal of methodological research has been done in this area and has been reported [12 and 18].
However, a number of studies are still in progress in the Netherlands, e.g. at the RIVM, as
well as in an international context such as the OECD (Organisation for Economic Co-
operation and Development). The OECD has recently organised a workshop on this subject
[19]. It is therefore that several methods have been used for the ecotoxicological risk assess-
ment of cationic surfactants.
The results of the various risk calculations for cationic surfactants are remarkably
consistent, despite the uncertainties in determining toxicity and the different statistical
approaches. Nevertheless it is worth noting certain reservations regarding the test results and
the calculations.
The first concerns the test results with Photobacterium phosphoreum. In tests with this
species the toxicological response is measured by the inhibition of light emission [20]. The
test, carried out using freeze-dried bacteria which are reanimated just before the test, is quick.
637
That's why it is often used. However, the bacterium is by nature a salt-water species. In our
study the test was therefore also carried out with isotonic sucrose solutions in water. As the
solubility of DTDMAC in distilled water is between 1 and 10 mg/1 and the NOEC according
to this experiment is 4.27 mg/1, it is possible that the Microtox experiment (in a 2% NaC1
solution or isotone sucrose solution) with a technical-grade DTDMAC may have been carried
out close to its saturation point. The test results, however, correspond closely to the results
of the degradation test done by Ventullo and Larson [21]. They found an inhibition of glucose
breakdown by heterotrophic bacteria at DTDMAC concentrations of i mg/l and higher. If the
NOEC for P. phosphoreum is not included in the calculations in methods 3 and 4, the
maximum permissible risk level and the negligible risk level will be slightly higher. Using
the method developed by Van Straalen and Denneman [16], the maximum permissible risk
level would increase from 63 to 80 ~tg/1. More relevant are the data published by Tubbing and
Admiraal [22] on the inhibition of bacterial and phytoplankton metabolic activity in the lower
Rhine by DTDMAC. Thymidine incorporation studies with bacteria and DTDMAC led to
EC10 values of circa 10 ~tg/1 for DTDMAC. They concluded that a total concentration of
circa 10 ~tg/l DTDMAC measured in the Rhine is likely to have biological consequences
In order to apply method 2, tests must be carried out with at least the following taxa:
algae, crustaceans, molluscs and fish. This requirement has not been met, as long-term tests
are available only for fish and algae. To allow for this, an additional safety factor would have
to be introduced. We did not introduce such a factor in the above risk assessment.
Furthermore, the experiments with algae are based on the total concentrations instead of the
concentrations of dissolved material. If a correction is made for this according to [7], the
maximum permissible risk level must be divided by a factor 3, as algae in these tests reach
densities corresponding to approximately 30 mg/l (dry matter). However, this correction will
depend on the species. The result is a maximum permissible risk level of 16 ~tg/1 and a
negligible risk level of 0.16 ~tg/1.
With regard to method 5 it should be noted that a further reduction of the available
data to obtain the lowest NOEC per group of organisms may affect the assumption that the
species sensitivity has a log-logistic distribution. However, a comparison of data sets B and
C shows that the consequences of this are likely to be theoretical rather than practical. This
is also shown by the differences between the maximum permissible risk levels and the
negligible risk levels calculated with methods 4 and 5.
Finally, applying the extrapolation methods which are described in detail in the OECD
report of the workshop on the extrapolation of laboratory aquatic toxicity data to the real
environment [19], i.e. the methods which are based on a lognormal, log-logistic or log-
triangular distribution of sensitivities between species, similar results are obtained.
CONCLUSIONS
The ecotoxicological risk assessment of the cationic surfactant DTDMAC carried out
with 5 different risk assessment methods results in a maximum permissible risk level between
16 and 100 ~tg/1. This variation is small and equivalent to the variation which has been
observed in the reproducibility of toxicological experiments. Method 2 gives the lowest
maximum permissible risk level (16 ~tg/1) and negligible risk level (0.16 ~tg/1), although data
for crustaceans and molluscs are not available. In principle, the lowest values could be used.
However, as all risk assessment methods have advantages as well as disadvantages, and as
some of the toxicity of the technical-grade DTDMAC is due to its contamination with
MTTMAC, it is proposed that the mathematical average of these values, i.e. 50 p~g/1, is used.
The corresponding negligible risk level would be 0.5 ~g/1. Very recently some additional
information on fate and effects has become available [23].
From the toxicity data and the measured concentrations of cationic surfactants in
surface water currently available for Germany and The Netherlands (2-90 p.g/l), it may be
concluded that the negligible risk level is exceeded in almost all surface waters. On the basis
of our calculations and measurements available at the time of this assessment, the maximum
permissible risk level is likely to be exceeded in some 20% - 30% of surface waters in the
638
Netherlands (Fig. 2). The other measurements and calculations for the effluents of STPs,
sewage sludge, suspended matter and aquatic sediments indicate that high levels of cationic
surfactants can be found in the environment. The research results have been discussed with
the Netherlands Association of Detergent Industries and have fortunately resulted in an almost
immediate replacement of DTDMAC by readily biodegradable substitutes in fabric softeners.
Despite this quick replacement of DTDMAC in The Netherlands, this action has so
far not resulted in a noticeable reduction of DTDMAC concentrations in the aquatic
environment, which indicates that other than only national measures are required to reduce
this contamination.
Acknowledgements
The authors wish to thank Dr. P. van Zoonen of the Organic Chemistry Laboratory of
the RIVM for the analysis of cationic surfactants in the aquatic environment. They also thank
Hans Schoon (post-graduate student at the Free University of Amsterdam) and Ab Buijze for
their contribution to the ecotoxicological research of DTDMAC. Thanks are also due to Drs.
M. van der Gaag (Ministry of Transport and Public Works) for his comments and suggestions
regarding the risk calculations.
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23. Versteeg, D.J., T.C.J. Feijtel, C.E. Cowan, T.E. Ward and R.A. Rapaport. Environmental
risk assessment of DTDMAC in the Netherlands. Chemospere (this issue).
(Received in Germany 9 December 1991)
... Tile cationic suffactants used in fabric softeners are mainly quaternary ammonium compounds such as distearyl-dimethyl-ammoniumchloride (DSDMAC), ditallow-dimethylammoniumchloride (DTDMAC), hardened ditallow-dimethyl-ammoniumchloride and cetyl-trimethyl-ammoniumchloride. These technical-grade products may contain impurities such as mono-and trialkyl ammonium compounds [1]. The cationic surfactants chiefly used in fabric softeners are DSDMAC and DTDMAC. ...
... Owing to their strong adsorption onto minerals and organic matter, cationic surfactants are eliminated from the water phase. It is estimated that in STPs about 90% settles in the active sludge [1,2]. In laboratory tests the substances decompose; however, their rate of decomposition greatly depends on the presence of sediment. ...
... Probably none of the compounds is truly persistent, but their degradation is likely to be slow in surface water, where the concentrations are generally lower than those used in laboratory biodegradation tests. Studies with similar cationic surfactants have led to the conclusion that degradation will probably fail to occur in surface water which is hardly contaminated by waste water, i.e. surface water which has not been adapted [1]. No data are available on their anaerobic degradation in aquatic sediments. ...
Article
The use of cationic surfactants in the Netherlands (about 2500 tonnes as active ingredient on an annual basis) poses a serious risk to a wide variety of aquatic ecosystems. On the basis of ecotoxicological studies with ditallow-dimethyl-ammoniumchloride (DTDMAC), the most important fabric softener, a maximum permissible risk level of 50 μg/l and a negligible risk level of 0.5 μg/l have been derived. In 1990, concentrations of 6 – 25 μg/l were measured in the rivers Rhine, Meuse and Scheldt. Model predictions, confirmed by measurements in Germany and The Netherlands, show that in approximately 30 to 40% of the surface waters considerably higher DTDMAC are expected to occur. On the basis of this risk evaluation, which was discussed in the Dutch Parliament in spring 1990, the Netherlands Association of Detergent Industries agreed to replace DTDMAC by chemicals of lower environmental concern within a period of two years. Already by the end of 1990 almost all DTDMAC had been replaced by readily biodegradable substitutes. However, in June 1991, DTDMAC was detected in the rivers Rhine, Meuse and Scheldt at concentrations between 12 and 34 μg/l, which indicates that other than only national measures are required to reduce the large-scale pollution of surface waters with DTDMAC.
Article
In a recently published annex to the National Environmental Policy Plan of the Netherlands (1989), attention was paid to ecotoxicological effects assessment. The proposed procedure was based on the advice of the Health Council of the Netherlands (1989) on risk assessment of toxic chemicals for ecosystems. The various extrapolation methods described by the Health Council are critically discussed in this paper. The extrapolation method of Van Straalen and Denneman (1989) is evaluated for eight chemicals and 11 aquatic species. Conclusions are drawn about the quality and quantity of the ecotoxicological data needed for aquatic effects assessment. For the soil—a compartment that is often at risk—ecotoxicological effects assessment is not possible because suitable ecotoxicological test methods still have to be developed.
Article
For alkylbenzene sulfonate (LAS), a quality objective of 12-25 μg/l has been deduced from the NOEC (No Observed Effect Concentration) data. Taking into consideration the actual data, 20-30 μg/l, measured in the Ruhr river, it is clear that the LAS values were occasionally in excess of those laid down in the quality objective for this water way. It can be clearly shown that this compound and its behaviour in the field must be carefully monitored and there is now a great need for taking action concerning LAS.
Article
For the risk assessment of substances the dilution of effluent from the majority of waste water treatment plants in The Netherlands has been estimated. The results of this study have been applied in the risk evaluation of ditallow dimethyl ammonium chloride (DTDMAC) to estimate exposure concentrations in the surface waters.The information from a national database has been combined with a dilution model to estimate dilution factors at these waste facilities.The surface water system in The Netherlands is for an extensive part made up by polders. The results of the model show that the median dilution factor in The Netherlands is about 30. However, the distribution of the dilution factor varies from 1 for polder waters up to 100,000 in the River Rhine. In 20 percent of the cases the dilution factor is less than 5, mostly in the narrow polder waters and small tributaries.Application of the dilution factors in the case of DTDMAC results in a medium exposure concentration of 3 μg/l but it ranges from 0.01 up to 250 μg/l, showing the importance to consider the large variation of the dilution factor. Risk assessment of substances applying medium or average values will result in an under-estimation in about 50 percent of the cases of the concentration in the aquatic environment.
Article
The bioavailability of sediment-sorbed and soluble fractions of three surfactants were compared in egg hatchability and partial life cycle chronic bioassays with the midge Chironomus riparius. The chemicals tested were linear alkyl (dodecyl) benzene sulfonate (LAS), dodecyl trimethyl ammonium chloride (TMAC) and distearyl dimethyl ammonium chloride (DSDMAC). Midge eggs exposed to ranges of surfactant concentrations in water were monitored for hatching success and posthatch survival. No significant reductions in egg hatching were observed at the highest concentrations tested: 18.9 mg/L LAS, 21.5 mg/L DSDMAC and 15.4 mg/L TMAC. Newly hatched larvae were more sensitive than eggs; respective 72-h LC50 concentrations (48-h for TMAC) were 2.2, 11.3 and 14.6 mg/L. In partial life cycle chronic bioassays in sediment/water test systems, percentages of winged adults emerging after continuous exposure of larvae and pupae to doses of each surfactant were determined. Exposure concentrations in sediment, interstitial water and overlying water were monitored by 14C liquid scintillation counting. Lowest observed effect concentrations (LOECs) of sediment-spiked surfactants were 319 to 993 μg/g (dry weight) LAS, 876 to 2,708 μg/g DSDMAC and >3,084 μg/g TMAC (highest concentration tested). Corresponding no observed effect concentrations (NOECs) were 319 μg/g LAS, 876 μg/g DSDMAC and 3,084 μg/g TMAC. The NOECs are approximately 100, 1,000 and 10,000 times greater than respective NOECs of the solubilized materials, and exceed levels of these materials measured in the environment. The results indicated that adsorption onto sediment significantly mitigates surfactant bioavailability to Chironomus.
Article
The first comprehensive evaluation of the environmental safety of three similar cationic surfactants to aquatic life is reported. Toxicity tests were conducted that exposed freshwater and marine species, representing three trophic levels, to the dialkyl dimethyl ammonium compounds. The studies were conducted in a high-quality laboratory water and in river waters that were used to model realistic receiving streams. Most current laboratory test methods for the assessment of chemical effects on aquatic life do not consider the physical and chemical properties of the test material in surface waters. This safety assessment shows that these considerations are important in developing realistic conclusions about the ecological safety of cationic surfactants. In tests using river water, acute and chronic toxicities and bioconcentration were considerably less than those in corresponding tests conducted in filtered laboratory waters. This reduction in toxicity and/or uptake was attributable to the aqueous insolubility of the surfactants, strong adsorption to natural solids and tendency to form chemical complexes with anionic substances. The mean ratio of the concentration of anionic to cationic surfactants in municipal sewage treatment plant effluent is 4:1. Safety margins were calculated for daphnids and fathead minnows using the ratio of the no observed effect concentration, determined from chronic toxicity tests, to mean measured surface water concentrations. Safety margins for fish and daphnids were 7 and 11, respectively, for a river having a low wastewater effluent dilution factor of 10. For a river with a higher dilution factor of 150, the values were 115 (fish) and 190 (daphnids). Projected safety margins for marine invertebrates and fish were several orders of magnitude greater than those for freshwater species. Based on available information and expected usage levels, the projected environmental impact of these surfactants on aquatic life is minimal.
Article
In a recently published annex to the National Environmental Policy Plan of the Netherlands (1989), attention was paid to ecotoxicological effects assessment. The proposed procedure was based on the advice of the Health Council of the Netherlands (1989) on risk assessment of toxic chemicals for ecosystems. The various extrapolation methods described by the Health Council are critically discussed in this paper. The extrapolation method of Van Straalen and Denneman (1989) is evaluated for eight chemicals and 11 aquatic species. Conclusions are drawn about the quality and quantity of the ecotoxicological data needed for aquatic effects assessment. For the soil—a compartment that is often at risk—ecotoxicological effects assessment is not possible because suitable ecotoxicological test methods still have to be developed.
Article
The environmental safety of the cationic surfactant, ditallow dimethyl ammonium chloride (DTDMAC), has been determined from usage rates and fate data from The Netherlands and standard, well accepted assessment techniques. An environmental concentration model was developed using DTDMAC tonnages for 1990, actual per capita waste flow, and measured removal rates in wastewater treatment plants. This model incorporated a state of the art dilution model, instream removal and background DTDMAC concentrations. Based on this model, the 90th percentile river concentration of DTDMAC below wastewater treatment plant outfalls was estimated as 0.021 mg/L (i.e., 90% of Dutch surface waters receiving wastewater effluents have environmental concentrations less than 0.021 mg/L). This estimated concentration agrees well with the maximum measured DTDMAC concentrations in Dutch surface waters. Toxicity values for the risk assessment were derived from a study which used an environmentally relevant dosing system (i.e., effluent from an activated sludge treatment system) to measure commercial DTDMAC toxicity. Based on chronic toxicity data for and from this study, a no effect level of 4.53 mg/L was determined for use in the risk assessment. Thus, the DTDMAC safety factor for aquatic organisms is 215 (4.53/0.021). It is concluded that DTDMAC poses a low risk to aquatic life based on testing of sensitive species and environmental concentrations predicted by state-of-the-art assessment methods.
Article
The acute and (semi-) chronic toxicity of ditallow dimethyl ammonium chloride (DTDMAC) to several aquatic organisms was determined in surface water. The acute toxicity (96-h LC50) for the stickleback Gasterosteus aculeatus, the midge larva Chironomus riparius and the pond snail Lymnaea stagnalis was 4.5, 9.2 and 18 mg/l respectively. The NOECs determined in (semi-) chronic toxicity experiments with the same species were 0.75, 1.3 and 0.32 mg/l respectively. The NOEC for the green alga Scenedesmus pannonicus, the bacterium Photobacterium phosphoreum (Microtox) and nitrifying bacteria was 0.75, 5.6 and 3 mg/l, respectively. From these results it can be concluded that DTDMAC is a rather toxic chemical and differences in species susceptibility to DTDMAC are small.