TOXICITY OF THE ANTISAPSTAIN FUNGICIDES, DDAC AND IPBC ...

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
57
4.5
TOXICITY OF THE ANTISAPSTAIN FUNGICIDES,
DDAC AND IPBC, TO FISHES AND
AQUATIC INVERTEBRATES
by Anthony P. Farrell
and Christopher J. Kennedy
Simon Fraser University, Burnaby, B.C.
The lumber industry in western Canada relies heavily on the use of antisapstain products to prevent
the growth of moulds and fungi on lumber for export. Sawmills on the Fraser River predominantly
utilize formulations containing didecyl dimethyl ammonium chloride (DDAC) and 3-iodo-2-propynyl
butyl carbamate (IPBC) as active ingredients. In 1996, approximately 155 tonnes of DDAC and 11
tonnes of IPBC were used. Whereas the proprietary literature on the toxicity of both of these compounds
to aquatic organisms has been reviewed (Hendersen 1992a, b; Envirochem 1992), information
contained in the refereed literature is very limited. At the beginning of the Fraser River Action
Plan (FRAP), Canadian water quality guidelines for either chemical had not been established due to
the lack of sufficient data.
In the absence of water quality guidelines, the regulatory limits for DDAC and IPBC in stormwater runoff
from mill sites were set by the provincial government at 700 ppb and 120 ppb, respectively, using acute
lethality data for rainbow trout (Government of British Columbia 1990). However, the adequacy of these
regulatory levels needs to be evaluated, because other ecologically relevant species of fish and invertebrates
may be more sensitive, and synergistic effects could occur in the presence of both chemicals.
The aim of the present research program was to generate baseline aquatic toxicity data for DDAC and IPBC
for use in the development of ambient water quality guidelines and for assessing potential impacts of these
chemicals in the lower Fraser River. The test organisms used were fishes and aquatic invertebrates that either
were relevant to the Fraser River or could be used for broader comparison with standard test organisms.
Troysan Polyphase P-100, containing 97 per cent IPBC, and Bardac 2280, containing 80 per cent DDAC,
were used either singly or in a 1:8 mixture for the toxicity tests.

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
MATERIALS AND METHODS
Information on the fish and aquatic invertebrate species used in this study, their holding and testing conditions,
and the methodologies are summarized in Farrell and Kennedy (1999). Acute lethality studies were
performed, as well as acute sublethal studies that measured indicators of stress (biochemical and physiological
changes in tissues) and indicators of performance (swimming speed and disease resistance) (Adams
1990; Schreck 1990).
Bardac 2280 (Lonza Inc., Fair Lawn, NJ) contained 80–82 per cent DDAC, as the principal active ingredient,
10 per cent ethanol, 7–10 per cent water and

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
mill effluent (Howard
1975; McLeay and Brown
1979) and 2-(thiocyanomethylthio)
benzothiazole
(TCMTB) (Nikl and
Farrell 1993). In contrast,
the resistance of juvenile
trout to a disease challenge
by Vibrio anguillarum was
significantly improved
with exposure to 50 and
100 per cent of the 96-h
LC 50 value for Bardac (data
not shown).
The acute toxicity of
Bardac to invertebrate species
(48-h LC 50 ) varied by
about 30-fold, from 37
ppb for Daphnia magna to
972 ppb for Neomysis
mercedis (Table 1).
Polyphase P-100 Toxicity
The acute toxicity of Polyphase
P-100 (referred to as
Polyphase for the rest of
this chapter) to the fish
species (96-h LC ) varied
50
by 30-fold, from 95 ppb
for coho smolts to 1,900
ppb for coho embryos (Table
2; concentrations based
on active ingredient are
97% of the numbers
quoted). Juvenile rainbow
trout and coho smolts
showed a similar sensitivity
to Polyphase, but starry
flounder were almost four
times more tolerant of
Polyphase.
Table 1. Acute toxicity of Bardac 2280 to fishes and aquatic invertebrates.
TEST SPECIES EXPOSURE
DURATION
Fishes:
Coho
96-h
embryo (4-day old)
Coho
96-h
eyed-embryo (42-day old)
Coho
96-h
alevin (67-day old)
Coho
96-h
alevin (76-day old)
Coho
96-h
alevin (86-day old)
Coho
96-h
swim-up fry (104-day old)
Coho
96-h
smolt (10-month old)
Rainbow trout
96-h
juvenile
Starry Flounder
96-h
juvenile
Fathead minnow
96-h
(7-day old)
White sturgeon
96-h
fry (42-day old)
Invertebrates:
Hyalella azteca
48-h
Daphnia magna
Mysidopsis bahia
Neomysis mercedis
59
48-h
48-h
48-h
NOEC
150 ppb
600 ppb
320 ppb
320 ppb
400 ppb
420ppb
500 ppb
200 ppb
1,500 ppb
50 ppb
1 ppb
75 ppb
30 ppb
20 ppb
420 ppb
LC 50
(95% CI)
570 ppb
(400–920)
1,100 ppb
(600–1,200)
420 ppb
(320–560)
390 ppb
(350–430)
460 ppb
(430–580)
490 ppb
(460–540)
950 ppb
(810–1,100)
410 ppb
(330–510)
2,000 ppb
(1,500–2,200)
330 ppb
(300–500)
2.5 ppb
(1–10)
110 ppb
(93–120)
37 ppb
(28–48)
39 ppb
(20–40)
972 ppb
(720–1,100)
LC 100
1,200 ppb
1,200 ppb
560 ppb
560 ppb
560 ppb
560 ppb
1,200 ppb
500 ppb
2,200 ppb
500 ppb
10 ppb
240 ppb
75 ppb
40 ppb
1,400 ppb
Concentrations are reported as nominal concentrations of Bardac 2280.
Age of coho salmon is in days or months post-fertilisation.
LC 50 values and 95% confidence intervals (CI) were calculated using probit analysis, based on the
pooled data set for a given test organism. There was no mortality observed in any fish control groups.
Mortality in invertebrate control groups was rare and never exceeded 10% in a given test, in which
case, the adjusted mortality was calculated according to Abbott’s formula. LC 100 is the lowest test
concentration at which 100% mortality was observed.
NOEC (no observable effects concentration) is the highest test concentration at which mortality was
identical to the control. If no test concentration resulted in zero mortality, then the NOEC is reported
as less than the lowest concentration tested.
Twenty-four-hour sublethal exposures to 25, 50 and 100 per cent of the 96-h LC 50 concentrations did not
elicit a strong primary stress response in either rainbow trout or starry flounder. The plasma variables were
unchanged in rainbow trout and only leucocrit levels in starry flounder decreased significantly after exposure
to 100 per cent of the LC 50 concentration for Polyphase (Farrell and Kennedy 1999).
The acute toxicity of Polyphase to the invertebrate species (48-h LC 50 ) varied by 70-fold, from 40 ppb for
D. magna to 2,920 ppb for N. mercedis (Table 2).

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
Toxicity of a Polyphase P-100 and Bardac 2280 Mixture
The acute toxicity of a 1:8 v/v mixture of Polyphase and Bardac to the fish species (96-h LC ) varied 3-fold,
50
from 430 ppb for juvenile coho to 1,280 ppb for juvenile starry flounder (Table 3). The acute toxicity (48h)
of this mixture for the invertebrate species
varied by 30-fold, from 26 ppb for
H. azteca to 770 ppb for N. mercedis. The
additive indices for fish acute toxicity indicated
that Polyphase and Bardac were
marginally, but consistently, less than additive
for rainbow trout and coho, and
marginally additive for flounder. For the
invertebrates, Polyphase and Bardac were
less than additive for D. magna, marginally
more than additive for N.
mercedis, and considerably more than
additive for H. azteca.
Twenty four-hour sublethal exposure to
the mixture caused little change in most
of the measured stress variables, even at
the 96-h LC 50 value (Farrell and Kennedy
1999). However, plasma cortisol levels in
rainbow trout were significantly elevated
in a concentration-dependent manner (a
primary stress response), beginning with
the lowest concentration tested. Juvenile
starry flounder responded at 100 per cent
of the 96-h LC 50 value with elevated
plasma glucose and decreased leucocrit,
both of which indicate a secondary stress
response. However, plasma lactate was significantly
decreased at all concentrations
tested, a response that indicates an anaesthetic/analgesic
action.
DISCUSSION
This study provided new information on
the acute lethal and sublethal toxicity of
Bardac and Polyphase to species common
to the Fraser River and to selected standardized
test species (e.g. rainbow trout
and D. magna). More discussion of the
component study results are available in
recently published papers by Wood et al.
(1996), Bennett and Farrell (1998), and
Farrell et al. (1998a,b). These studies have
allowed for a better assessment of the tox-
Figure 1. A comparison of the concentration-response
relationships for Bardac 2280 alone, Polyphase P-100 alone and
a mixture containing 8 parts Bardac 2280 and 1 part Polyphase
P-100. Each line represents one test organism and connects the
concentration causing no mortality with the concentration
producing 100% mortality. In general, the gradient of these lines
is steep, indicating a narrow concentration range over which the
chemical is acutely toxic. For comparison, fishes are presented with
solid lines and invertebrates with broken lines.
Abbreviations: RBT = rainbow trout; FH = fathead minnow; E = coho salmon
embryo; A = coho salmon alevin; F = coho salmon fry; S = coho salmon smolt; SF
= starry flounder; D = Daphnia magna; H = Hyalella azteca; N = Neomysis
mercedis; M = Mysidopsis bahia.
60
��

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
icity of these antisapstains
in the Fraser River than
would be possible with
the standard testing utilized
in the chemical registration
process (see
Szenasy et al. 1999).
Table 2. Acute toxicity of Polyphase P-100 to fishes and aquatic invertebrates.
TEST SPECIES
61
EXPOSURE
DURATION
NOEC
LC 50
(95% CI)
Fishes:
Coho
96-h

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
and fishes (Cooper
1988). However,
we have either
identified some of
the more sensitive
aquatic organisms,
or Bardac is one of
the more acutely
toxic quaternary
ammonium compounds.
For Polyphase, again
there is consistency
between our
acute toxicity data
and the proprietary
information.
Henderson (1992b)
reported LC 50 values
for rainbow
trout that ranged
Table 3. Acute (96-h exposure) toxicity of a mixture (1:8) of Polyphase P-100 and
Bardac 2280 to fishes and invertebrates.
TEST SPECIES EXPOSURE
DURATION
Fishes:
Coho
96-h
alevin (53-day old)
Coho
96-h
juvenile (7-month old)
Rainbow trout
96-h
juvenile
Starry Flounder
96-h
juvenile
Invertebrates:
Hyalella azteca
48-h
Daphnia magna
Neomysis mercedis
48-h
48-h
from 67 ppb IPBC for a 24-h flow-through bioassay to 310 ppb IPBC for an unspecified bioassay. In our
study, after converting to active ingredient concentrations, juvenile rainbow trout and coho fry had 96-h
LC 50 values of 97 and 126 ppb, respectively. Henderson (1992b) also reported that rainbow trout were
about two times more sensitive to IPBC than bluegill sunfish. We found that rainbow trout (and coho
salmon) were almost four times more sensitive to IPBC than starry flounder. Invertebrates represented the
most sensitive species (D. magna; LC 50 value of 39 ppb) and the most tolerant species (N. mercedis; LC 50
value of 2,832 ppb). In contrast to our findings, Henderson (1992b) reported a 48-h LC 50 value for D.
magna (645 ppb) that was almost 15 times higher than the value obtained here.
The minimum data requirements for setting Canadian water quality guidelines for both chemicals are met
with the proprietary data and this study (Environment Canada 1998; 1999). The recommended interim
guidelines were set at 1.5 and 1.9 ppb for DDAC and IPBC, respectively.
It is important to discuss the relevance of acute toxicity testing on standard test organisms, upon which the
guidelines are based, to the toxicity potentially experienced by species living in the Fraser and its specific
receiving environment conditions. The following discussion focuses on potential toxicity impacts of stormwater
discharges on resident species, including considerations of the influence of receiving environment conditions
and the significance of sublethal exposure.
Relevant Species
The test species that were relevant to the lower Fraser River and its estuary included N. mercedis, starry
flounder, juvenile coho salmon and juvenile white sturgeon. Under the present regulatory limit of 700 ppb
DDAC for stormwater discharge and using 50 per cent lethality as the measure of a deleterious effect, the
most tolerant of the invertebrate or fish species we tested (i.e. adult N. mercedis and juvenile starry flounder)
are presumably protected as dilution would further reduce exposure concentrations. However, since these
animals were collected in the estuarine area of the Fraser River, where they normally live and breed, it could
be argued that our testing used only a selected sub-population already exposed to, and tolerant of, numerous
toxicants that potentially included DDAC.
62
NOEC
320 ppb
320 ppb
320 ppb
700 ppb
14 ppb
1,500 ppb
72 ppb
160 ppb
1,400 ppb
ADDITIVE
INDEX (95% CI)
-0.37
(-0.39 to -0.33)
-0.27
(-0.33 to -0.17)
-0.38
(-0.52 to -0.24)
0.06
7.47
(8.34 to 29.4)
-1.77
(-2.32 to -1.37)
0.37
(0.20 to 0.39)
Nominal concentrations of the formulation (8 parts Bardac 2280 and 1 part Polyphase P-100) are presented.
Nominal concentrations of the active ingredients can be calculated using 0.71 times the formulation concentration
for DDAC and 0.065 times the formulation concentration for IPBC.

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
Our studies suggest that, if exposed for sufficient time at the 700 ppb level, juvenile coho, and especially
juvenile white sturgeon, would not be adequately protected by the regulatory limit for DDAC. It is important,
therefore, to determine the likelihood of their exposure to DDAC and at what levels (see Szenasy et al.
1999). It is also salient to evaluate whether or not the higher sensitivity of these species is characteristic of
other aquatic organisms that were not tested here, but nonetheless at risk of DDAC exposure.
The extreme sensitivity of 40-day-old juvenile white sturgeon found in our study is of particular concern.
While recent testing done at another lab has found the sensitivity of white sturgeon to be similar to rainbow
trout (TRS 1997), that lab tested 80-day-old juveniles, and it may be that sturgeon could be more vulnerable
at the very early life stages. The water quality characteristics also likely differed between the two test
locations. In addition, both the TRS (1997) and our study utilized a Sacramento River, rather than a Fraser
River, fish stock, which makes their applicability less certain. Unfortunately, this problem will not be
alleviated soon because there is no immediate supply of fertilized Fraser white sturgeon eggs. Once a supply
is developed, toxicity tests should be done in another independent lab to investigate the range of toxicity
shown at several ages, including the ages tested so far. Of equal importance, there is an urgent need to
describe the ecology of white sturgeon in the Fraser River to identify their probability of exposure, particularly
to the early life stages. White sturgeon populations in the Fraser River have been reduced dramatically
through over-harvesting. Their recovery depends on eliminating contaminant stress as well as harvesting,
which is already banned.
Under the present regulatory limit of 120 ppb IPBC and using 50 per cent lethality as the measure of a
deleterious effect, the most tolerant of the invertebrate or fish species we tested (i.e. N. mercedis and juvenile
starry flounder) appear to be protected. Protection of juvenile coho, if exposed for sufficient time at this
level, would be marginal.
Measured IPBC concentrations in stormwater runoff from sawmills on the lower Fraser River have ranged
from non-detectable to as high as 370 ppb, whereas DDAC has been measured at levels as high as 6,000
ppb (Envirochem 1992). However, recent improvements in the handling of treated lumber have reduced
the concentrations in stormwater runoff to levels consistently at or below the effluent guidelines (Environment
Canada 1997). The likelihood of biota being exposed to these guideline levels, which are in the range
of the LC 50 values, depends on the extent of dilution, degradation and adsorption onto particulate matter in
the plume as it mixes with river water. These factors are discussed below.
Relevance of Laboratory Toxicity to the Field
When extrapolating toxicity data obtained in dechlorinated municipal tap water to conditions in actual
river water, it is important that specific differences in water quality are assessed. In the case of the Fraser
River, especially in the lower estuarine reaches, the temperature, salinity and turbidity are highly variable.
Furthermore the mixing of a stormwater discharge is dependent on river flow and tidal cycles, both of which
vary considerably. Ideally, toxicity testing could be undertaken in mesocosms (see Culp et al. 1999) containing
some of the more sensitive species in conditions more like the river. Unfortunately, the mesocosm
approach is at an early stage of development and was not applied in this study. The following discussion,
then, focuses on the potential influence of salinity, temperature and suspended sediments on acute toxicity
levels that can be suggested based on the study presented here.
In the case of salinity, no significant change in toxicity to Bardac was observed with coho smolts. LC 50 values
were 950, 950 and 850 ppb for seawater salinities of 0, 15, and 30‰, respectively. It is also noteworthy
that the two euryhaline species (starry flounder and N. mercedis) which were tested in salt water had the
highest tolerance to Bardac of the fish and invertebrates tested. These observations suggest that species that
can adjust to variable salinity regimes may be relatively tolerant to this compound.
63

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
Different species were tested at different acclimation temperatures, but no experiments specifically examined
the effect of temperature. Therefore, comments on the possible confounding effect of temperature are
not possible. However, all of the test temperatures used were relevant to water temperatures in the lower
Fraser River, except for the tests at 25 o C on Hyalella and Mysidopsis.
With regard to a possible confounding effect from the suspended sediment in the river, it is well established
that quaternary ammonium halides strongly adsorb to sediments. Lewis and Wee (1983), Lewis (1991),
Versteeg and Shorter (1992), and Szenasy et al. (1999) all demonstrated that DDAC was quickly adsorbed
to particulate matter in the Fraser River. While DDAC shows strong sorption properties, it is not known if
DDAC attached to particles can be toxic without first being released into solution. In a study by Qiao and
Farrell (1996) using Fraser River sediment, adsorption to sediment increased the uptake of hydrophobic
biphenyls across fish gills. The fact that DDAC has both hydrophilic and hydrophobic properties points to
the need to perform similar uptake experiments with DDAC.
While DDAC is highly adsorptive, IPBC is much less so. The observations in the Fraser River (Szenasy et al.
1999) suggest that IPBC is not adsorbed quickly to sediments in the immediate mixing zone. However, it
was detected in sediments of the Fraser, which suggests adsorption does occur over time. The first observation
indicates that the laboratory toxicity information is generally applicable to the immediate mixing zone,
while the second points to the need for sediment-bound toxicity testing.
Relevance of Acute Lethality For Deriving Water Quality Criteria
Acute toxicity tests are the first and often the only types of toxicity tests performed on new compounds.
Thus, acute toxicity values represent a large and useful comparative database from which water quality
guidelines are typically set. Similarly, our above predictions about protection of relevant Fraser River aquatic
organisms were based on the assumption that acute toxicity data are useful in this regard. Some of the work
performed here allows us to examine this assumption.
The relevance of acute lethality levels to the receiving environment hinges on the extent of the mixing zone
likely to have concentrations near these levels and the duration of time that these levels are maintained. In
the Fraser estuary, mixing of near shore discharges is strongly influenced by river flow rate and tidal stage.
Furthermore, many of the stormwater discharges from sawmills enter the river at the shore so the plume
tends to hug the shoreline, especially on an ebb tide (Hodgins et al. 1998). As many juvenile stages of fishes
and invertebrates utilize the near shore zone in the river, it is important to know these mixing characteristics
before the acute lethality data can be assessed. On the other hand, Szenasy et al. (1999), found that DDAC
concentrations declined even faster than the dilution rate and were below the detection limit (10 ppb) less
than 10 m downstream of the outfall.
Another aspect of acute lethality is the steepness of its onset. We consistently discovered unusually steep
concentration-response relationships for Bardac with fish and aquatic invertebrates (Fig. 1). The same occurred
for Polyphase with fish, but not with invertebrates. This steep concentration-response relationship is
in keeping with the more general finding for quaternary ammonium halides (Cooper 1988). One of the
implications of this relationship is that the concentrations for the NOEC and 100 per cent mortality were
rarely more than an order of magnitude apart. Thus, a 10-fold dilution from the LC 50 value would easily
prevent acute lethality and it also suggests that sublethal toxicity is less likely.
Novel information on the sublethal toxicity of antisapstains was generated in this study. The sublethal
exposure period was limited to 24 hours to better simulate a stormwater runoff situation. Test concentrations
were set at a proportion of the 96-h LC 50 value to assist comparisons. In general, a primary stress
response was not observed in either rainbow trout or starry flounder at an exposure concentration lower
than 50 per cent of the 96-h LC 50 value. Likewise, in unspecified studies with bluegill sunfish, coho
salmon, Daphnia magna and a mysid shrimp, the reported NOEC was always within 50 per cent of the
64

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
LC 50 value for DDAC (unpublished data, Springborn Laboratories, Inc.; as quoted in Henderson 1992a).
In view of these results, acute toxicity endpoints may be a reasonable starting point for the development of
water quality guidelines for short exposures to antisapstain fungicides. However, at this time we do not
know what a relevant exposure period might be. The precise nature, extent and timing of the sublethal
response will depend on the mechanism of action for the chemical, of which we know little for these
antisapstain fungicides in aquatic organisms (Johnston et al. 1997).
The likelihood of aquatic organisms being challenged by only DDAC or IPBC in the Fraser River is unlikely.
There are many other toxicants, pathogens and water quality conditions that collectively tax the
overall tolerance of these organisms, perhaps increasing their sensitivity to DDAC and IPBC. Also, there are
various antisapstain formulations in use that incorporate both IPBC and DDAC (Henderson 1992b). For
example, the formulation NP-2 contains a 1:7 mixture of the two antisapstain compounds IPBC and
DDAC. The present study provided new information on the interactions of a mixture of IPBC and DDAC.
While additive toxicity indices for fish species deviated very little from a simple additive effect of IPBC and
DDAC, the findings for the invertebrate species varied considerably and were less predictable. For instance,
the combined effects of IPBC and DDAC on N. mercedis were nearly additive, but simple addition would
overestimate by more than two-fold the toxicity of the mixture to D. magna. In contrast, simple addition
would underestimate by 16-fold the acute toxicity of the mixture to H. azteca. Of further concern were the
sublethal stress effects that were revealed with the mixture but not with the individual chemicals. A primary
stress response (elevated cortisol) occurred in rainbow trout at a much lower concentration of Bardac when
it was mixed with Polyphase. Also, the lowered plasma lactate in starry flounder when exposed to the
mixture is a concern. These observations suggest that sublethal effects of mixtures of antisapstain chemicals
cannot be predicted from acute toxicity data, especially when the dose-response curves are so steep. The
possibility exists that either chemical could interact with any of the many other toxicants found in the river
to elicit a sublethal response.
CONCLUSIONS AND RECOMMENDATIONS
The acute toxicity of the DDAC and IPBC formulations selected for our tests were quite variable, but both
chemicals were in the same general range. The acute toxicity of Bardac 2280 to fish species (96-h LC ) 50
varied by about ten-fold, from 330 ppb for fathead minnows to 2,000 ppb for starry flounder, with the
exception of very young white sturgeon fry, which were even more sensitive. The acute toxicity of Bardac to
invertebrate species (48-h LC ) varied by about 30-fold, from 37 ppb for Daphnia magna to 972 ppb for
50
Neomysis mercedis. The acute toxicity of Polyphase P-100 to the fish species (96-h LC ) varied by 30-fold,
50
from 95 ppb for coho smolts to 1,900 ppb for coho embryos. The acute toxicity of Polyphase to the
invertebrate species (48-h LC ) varied by 70-fold, from 40 ppb for D. magna to 2,920 ppb for N. mercedis.
50
While the toxicities overlap for the most part, DDAC appears to be slightly more toxic to invertebrates than
IPBC and the reverse is true for fish except for sturgeon. Only one of the species tested, H. azteca, showed
any significant synergistic effect when exposed to a mixture of both chemicals in a ratio similar to one of the
most common formulations used in the Fraser Basin.
This new toxicity information, along with the recently developed interim Canadian water quality guidelines,
should be used to re-evaluate the present effluent guidelines, which were established in the early ’90s,
and to develop ambient site-specific water quality objectives for the lower Fraser River. However, a significant
knowledge gap hampering the application of the new information and guidelines to these ends is the
lack of data on toxicity of DDAC after it is adsorbed to suspended sediments and subsequently maintained
in suspension. To date, most studies have examined toxicity after sediments have settled to the bottom of
the test chamber. This condition would not be representative of the Fraser River where much of the fine
sediment load remains in suspension.
65

4.5 TOXICITY OF DDAC AND IPBC TO FISHES AND AQUATIC INVERTEBRATES
Based on the general inadequacies of predicting impacts of specific chemicals in our rivers with standardized
species and laboratory conditions, it is recommended that research on the use of mesocosms be initiated.
Mesocosms could be set up to use river water and intermittent injection of runoff to mimic the real world
(see Culp et al. 1999). This approach would require the development of a laboratory infrastructure to
supply ecologically relevant species for testing.
ACKNOWLEDGEMENTS
The technical support of Anthony Wood, Eric Stockner, Blair Johnston, Joanne Scherba and Keith Tierney
during this project was invaluable. The test chemicals used in this study were kindly donated by Kop-Coat
Inc., Pittsburgh, PA (Troysan Polyphase P-100) and Lonza Inc., Fair Lawn, NJ (Bardac 2280).
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