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EC number: 201-557-4
CAS number: 84-74-2
The study (Hüls 1994) established NOEC and LOEC values for DIBP
concerning long-term effects on daphnia magna.
DBP foraquatic invertebrates
Kuhn et al.(1989)
McCarthy and Whitmore (1985)
1.05 (21 dEC50)
De Foe et al.(1990)
0.54 (7 dEC50)
Yoshioka et al.(1986)
Thurén and Woin (1991)
The IPCS document
some other long-term toxicity studies with aquatic
invertebrates. The effect concentrations in these tests were all larger
In order to facilitate comparison of the results, the following data
were included in Table 1 on the substances listed according to substance
The 24 h EC0 and the 24 h EC50 (referred to the nominal value) for the
acute Daphnia test.
The NOEC as referred to the nominal value and, in addition, the minimum
value of the test concentration range, the dilution ratio, the
most sensitive parameter and the type of vessel used in the 21 d Daphnia
From data on the NOEC and the dilution ratios, it was possible to
identify the lowest concentration tested where an effect of the
substance could be observed.
Table 2 lists the substances according to their harmful effects (as
referred to the nominal value) beginning with the most toxic. The
minimum value was also given.
Table 2 reveals a higher toxicity of phthalates with increasing alkyl
chain length. In comparison with phthalic acid diethyl ester, the NOEC
of phthalic acid diallyl ester was 4 times lower; it was 13 times lower
in the case of phthalic acid dibutyl ester.
Table 3 shows the nominal concentrations obtained for the 24 h EC50 and
the 21 d NOEC by substance groups. The nominal concentrations had to be
given as no results of chemical analysis were available for the 24 h
EC50. For each tested substance, the statistically confirmed 24h EC50
and NOEC values were related to each other whereby a substance
concentration of NOEC = l was used.
The study tested the effects of 73 substances on daphnia magna. Only
those related to DBP are documented here.
DBP was substantially more toxic to Palaemonetes larvae than DMP (Figure
2). At 10 and 50 ppm DBP, there was 100°70 mortality in 3 to 4 days.
However, at these nominal concentrations, fine droplets of DBP were
observed to coalesce from the medium
and remain in suspension or migrate to the surface. Larvae encountering
such droplets might become coated and thus receive a greater than
expected dose of DBP. Control survival was significantly lower, 51%,
than in the DMP experiment, indicating inter-hatch variability in the
viability of the larvae. At exposure concentrations of 100, 500 and 1000
ppb survival was 45, 64 and 41%, respectively.
A highly significant decrease in survival resulted from exposure to DMP
and DBP (Table II). However, as indicated above, mortalities observed at
10 and 50 ppm DBP may not have been due to chemical toxicity of
phthalate in solution. When data from these 2 DBP concentrations are
excluded then DBP exposure did not have a significant effect on larval
survival (p > F = 0.4).
Larvae exposed to DBP showed the same intermolt pattern as those exposed
to low concentrations of DMP. There was some suggestion of molt
desynchronization for animals exposed to 1 ppm DBP. This effect was not
as obvious as that seen in animals exposed to the highest concentrations
of DMP. No effect was apparent until after the first zoeal molt (i.e.,
after day 4). In no case was there evidence for any phthalate of a
dose-dependent change in the stage structure of zoeal development.
Duration of larval development
The mean duration of zoeal development of larvae exposed to the 3
phthalates is shown in Figure 4. At DMP concentrations between 100 ppb
and 10 ppm, the mean duration of development from hatching to the first
postlarval instar was slightly less than that for the controls. At 100
ppm DMP, the mean duration of zoeal development was nearly twice as long
as that of the controls. The effects of DBP and DEHP on developmental
rate were more variable. Exposure concentrations of 100 and 500 ppb DBP
resulted in mean developmental rates lower and higher, respectively,
than the control rate. However, at 1 ppm DBP, developmental rate was the
same as that of the controls. There was little variation from control
values in the developmental rate of larvae exposed to any concentration
The regression analysis of the molting rate data is shown in Table III.
Once again, exposure data for each phthalate ester were analyzed
separately. Each hatch was considered a block. Larvae exposed to DMP
showed highly significant differences in response to both treatment and
hatch of the larvae. The interaction of the treatment and source of
larvae (block) was significant.
Animals exposed to DBP showed no significant difference in response due
either to treatment or hatch. The interaction of treatment and hatch was
significant, suggesting that the differences observed were due to the
extreme variability of different exposure groups. The correlation for
this data was poor (r= 0.304), suggesting that uncontrolled factors, not
DBP exposure, produced the significant
differences among groups.
The effects of three phthalic acid esters, dimethyl phthalate (DMP),
di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) on
survival and development rate of larvae of the grass shrimp
Palaemonetespugio were investigated. Only 100 ppm DMP and 10 to 50 ppm
DBP were acutely toxic to the larvae.
In the acute mortality test (range-finding test), all D. magna were dead
after 48 h of exposure to nominal concentrations of 7.5
and 10.0 mg/L DBP. At the lower doses of 3.0, 1.0 and 0.5 mg/L DBP and
in controls, all animals survived, except for one individual at 3.0
mg/L. The LC50 (lethal concentration to 50% of the test population) is
between 3.0 and 7.5 mg/L DBP. Although a probit analysis cannot be
performed, because this procedure requires two responses that are
between 0 and 100% mortality, a nonparametric analysis was developed for
steep dose-response bioassays (Schmoyer, Beauchamp and McCarthy,
manuscript in preparation). The LC50 was estimated using this method and
was equal to 5.2 mg/L, with 95% confidence limits of 4.7 and 5.6
Temperature, DO and pH remained relatively constant throughout each test
and across all concentrations (Table 2). The measured concentrations of
DBP in the freshly prepared solutions (before animals were added) were
fairly close to the nominal doses; however, after 24 h, the
concentrations dropped by about one-third (Table 2).
The results of the filtration experiment designed to determine the
fraction of DBP bound to the suspended particulates in the food
demonstrated that only 2.5% (*0.2%) of the DBP was bound to the
suspended particulate matter.
Survival of D. magna exposed to DBP exceeded 80% in all concentrations
except 1.8 and 3.2 mg/L and in the carrier-free control. The reason for
the poor survival (and poor reproduction) of the control group is not
clear. By the end of the experiment (day 16),
70% of the D. magna were alive at 1.8 mg/L and 18% were alive at 3.2
mg/L DBP (Fig. 1 and Table 3).
The number of young produced per surviving adult at each dose is
indicated in Table 3. Reproduction in D. magna was stimulated at low
levels and inhibited at higher concentrations of DBP. Exposure to 0.056
to 0.56 mg/L DBP increased the total numbers of young produced.
Reproduction was significantly impaired at 1.8 mg/L, compared with that
at either the 0.56 mg/L dose or the carrier control. Although eggs were
occasionally observed in the brood sacs of animals exposed to a dose of
3.2 mg/L DBP, no viable
young were produced. If the no observed effect concentration (NOEC) and
the lowest observed effect concentration (LOEC) are assumed to reflect
only inhibition of reproduction (as opposed to the apparent stimulation
observed at moderate doses), then the NOEC for DBP is 0.56 mg/L and the
LOEC is 1.8 mg/L (nominal concentrations).
Since the animals exposed to DBP were cultured individually, information
was obtained on the effect of DBP on the total number of broods (as
defined by appearance of eggs in the brood sac, rather than by release
of viable young) and on the number of days and number of molts required
to achieve reproductive maturity (primiparous instar). DBP had
relatively little effect on any of these
parameters, although the highest dose did result in a significant
decrease in the total number of broods and in the instar at which eggs
were first observed in the brood sac (primiparous instar, Table 4).
The toxicities of di-n-butyl phthalate (DBP) and di-n-octyl phthalate
(DOP) were assessed by measuring the effect of exposure to these
compounds on the fecundity of Daphnia magna and on the hatching and
survival of the early life stages of the fathead minnow Pimephales
promelas. Only the effects on Daphnia magna concerning DBP are
Geometric mean maximum acceptable toxicant concentrations (GM-MATC) were
determined for all 14 phthalate esters except DUP (Table 3), where no
effects on survival or reproduction were observed even at the highest
measured concentration (0.059 mg/L). The GM-MATC values ranged from
0.042 mg/L for DINP to 38.4 mg/L for DEP (Table 4). For DMP, DEHP, 71
lP, and DTDP, survival was the most sensitive end point. For the other
10 phthalate esters, survival and reproduction were equally sensitive.
Test-to-test variation in control daphnid reproduction (mean offspring
per adult female) ranged from 56 to 116; however, it meets ASTM E-I193
minimum criteria for an acceptable test. Variation between replicate
test chambers and treatment levels was much less than between tests and
allowed for sufficient statistical power to evaluate potential
reproductive effects. Test-to-test variation in control offspring
reproduction is of secondary importance relative to variation between
replicates and treatment levels.
The GM-MATC tended to decrease as the molecular weight and alkyl chain
length increased, up to a chain length of 4 to 6 carbon atoms. This
trend has been reported for acute toxicity studies for these same esters
with multiple species. One might expect, a priori, that toxicity would
increase and the water solubility decrease as the alkyl chain length
increases. This does not appear to be true. Phthalate
esters with alkyl chain lengths >= 6 carbon atoms have measured water
solubility values in the range of 0.09 to 1.2 mg/L, and they do not
decrease linearly with alkyl chain length. This is possibly due to
micelle formation. Phthalate ester molecules have both a polar and a
nonpolar group that lends itself to the formation of micelles. Micelles
are formed, due to coalescence of the test chemical, when the critical
micelle concentration is exceeded. This results in the formation of
microdroplets of pure chemical that are entrained in water during the
preparation of solutions for water solubility measurements
and toxicity tests. As a result, operationally defined water solubility
values are obtained since the standard phase separation techniques do
not provide separation of the micelles/microdroplets from the water
solution. This explains the lack of correlation between water solubility
and alkyl chain length and suggests that exposure concentrations used in
the present test, a well as in other previously reported toxicity
tests, may be greater than the “true” water solubility of the test
A comparison between the acute LC50 value and the GMMATC
(acute-to-chronic ratio; ACR) was possible for two of the 14 phthalate
esters. The ACR values for DEP and DBP were calculated using acute LC50
values previously reported. The values were very small, 2.2 and 2.3,
respectively. It was not possible to calculate ACRs for phthalate esters
with a molecular weight greater than DBP because
these phthalate esters were not acutely toxic at concentrations
approximating their aqueous solubility.
Chronic toxicity studies were performed with commercial phthalate esters
and Daphnia magna (14 phthalates) and rainbow trout (Oncorhynchus
mykiss) (six phthalates). Only the experiments on the daphnia magna
concerning DBP are documented here.
Measured effect concentrations [mg/l]:NOEC (10d): 0.10 (Gammarus pulex)NOEC (16d): 0.56 (Daphnia magna)NOEC (21d): 1.00 (Daphnia magna)EC50 (7d): 0.54 (Dugesia japonica)EC50 (21d): 1.05 ((Daphnia magna)For the chemical safety assessment the most sensitive endpoint has been chosen:
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