The
toxicity of ammonia to early life stages
of rainbow trout (Salmo gairdneri) was
examined in hard fresh water (Solbe &
Shurben, 2003). When exposure began
within 24 h of fertilisation and
proceeded for 73 days, severe mortality
(> 70%) occurred, particularly among the
eggs, at concentrations of unionised
ammonia as low as 0.027 mg NH3/L. When
exposure did not start until the
eyed-egg stage (c. 24 days) only 40% of
the eggs, yolk-sac fry and fry (but
especially the fry) died at 0.27 mg
NH3/L. No NOEC value was derived in the
study since effects were observed at the
lowest exposure concentration of 0.027
mg NH3/L. However, data on the
concentration–response curve for similar
effects in other fish have been
evaluated, and these indicate 2–3 times
difference in exposure concentration for
a 50 per cent reduction in survival
(from the controls) in such an early
life stage test. Hence, a NOEC of 0.0135
mg NH3/L is estimated. The finding that
eggs are specifically sensitive
contradicts to the findings from e.g.,
Rice & Bailey (1980), Brinkman et al.
(2009). Furthermore, the NOEC/LOEC
refers to the calculated NH3
concentrations and not to the total
ammonia concentration in the solution.
Since the NH3 and NH4+ will be in a
mainly pH driven equilibrium (see read
across justifaction), the share of NH3
is overestimating the toxicity of total
ammonia in the system. However, the
result from Solbe & Shurben (2003) was
used for the risk assessment as key
value for conservative reasons. The NOEC
values obtained from other studies were
higher and hence less protective.
Therefore, the NOEC estimation for this
study is considered to be conservative
and protective. This NOEC estimation
follows the argumentation layed out in
the SNIFFER Report SC040038/SR2
(Proposed EQS for water Framework
Directive Annex VIII substaces; ammonia
(un-ionized) 2007, published by the UK
Environment Agency).
Further
studies are available and are listed for
completeness:
Juvenile
channel catfish (L. punctatus) were
exposed to 12 ammonia concentrations
ranging from 48-2048mg un-ionized
NH3-N/L for 31 days. On a wet weight
basis, growth was reduced by 50% at 517
ug/L un-ionized NH3-N and no growth
occurred at 967 ug/L un-ionized NH3-N
and higher. Above 500 ug/L un-ionized
NH3-N, there was increasing damage to
the dorsal and pectoral fins. The
overall NOEC for the growth and weight
was < 48 ug un-ionized NH3-N/L. This
concentration corresponds to < 58 µg
NH3/L
In the
40 day flow-through ELS-study with
Lepomis cyanellus reported by McCormick
et al. (1984) the hatching success was
unaffected by exposure to un-ionised
ammonia concentrations from control
through 0.91 mg NH3/L (P>0.05). The mean
hatching success for all treatments, as
measured by numbers of normal live
larvae produced, was 73 % of the
original embryos in the samples.
However, by 3-4 days post-hatching 87 %
(46 of 53-- one complete replicate was
lost due to procedural error) of the
surviving larvae in the highest exposure
concentration (0.91 mg NH3/L) had
developed recognisable deformities.
Observed deformities were various
degrees of curvature of the spine and/or
pericardial oedema. Deformities among
the larvae in all lower exposure
concentrations were 1-3 %. The 10 days
following hatching are a most critical
period, when larval fish must make the
transition from endogenous to exogenous
feeding (Toetz, 1966). Mortalities
during this period were extensive and
reached 100 % in both replicates of the
highest ammonia concentration. Once the
conversion to feeding on live brine
shrimp nauplii was accomplished,
mortality rates were reduced but not
eliminated. These results indicate that
the maximum no observed adverse effect
concentration, based on growth
inhibition, is 0.22 mg NH3/L and the
minimum adverse effect concentration is
0.49 mg NH3/L.
Rice
and Baily (1980) exposed pink salmon
(Oncorhynchus gorbuscha) alevins exposed
to concentrations of unionized ammonia
ranging between 0 and 4 mg/L (Rice &
Bailey, 1980). The highest exposure
concentration of ammonia caused
significant decreases in weight of
exposed fry in all three exposure
groups. At 2.4 mg/L un-ionized ammonia,
the groups held for 40 days and 61 days
were significantly smaller in length and
weight and at 1.2 mg/L un-ionized
ammonia there was no significant
difference. The NOEC was therefore
concluded to be 1.2 mg/L un-ionised NH3.
Effects were consistently more adverse
for groups held 61 days.
Fertilised
rainbow trout eggs were exposed to 0.05,
0.10, 0.19, 0.28, and 0.37 mg NH3-N/L
for periods of either 25 or 33 days
followed by 42 days post hatch
observations. Egg mortality was not
affected in either run by any of the
ammonia concentrations. Growth and
development of rainbow trout sac fry are
inhibited by long-term exposures to
concentrations of ammonia as low as 0.05
mg NH3-N/L (Burkalter & Kaya, 1977). The
results were reported based on NH3 -N.
The concentration of 0.05 mg NH3 -N/L
corresponds to a concentration of 0.0608
mg NH3/L.
Brinkman
et al (2009) performed a 90-d ammonia
toxicity test for early life stage
rainbow trout Oncorhynchus mykiss using
newly fertilized eggs from a wild strain
of fish. The toxicity test was conducted
at a pH of 7.75 and temperature of
11.4°C .Hatch success and survival of
sac fry were not affected by ammonia
exposure. Survival, growth, and biomass
of swim-up fry were significantly
reduced at an ammonia-nitrogen (NH3-N)
concentration of 16.8 mg NH3-N/L of
water but were unaffected by exposures
to 7.44 mg NH3-N/L or lower
concentrations. The chronic toxicity
value was 11.2 mg NH3-N/L, and the EC20
(concentration estimated to cause a 20%
reduction in organism performance
compared with the control) based on
biomass at test termination was 7.72 mg
NH3-N/L. Development of sac fry to the
swim-up stage was retarded by ammonia,
but fry exposed to 7.44 mg NH3-N/L or
lower concentrations appeared to recover
by the end of the test. Histological
analysis of the gills of exposed fry did
not detect any gill pathology. Applying
the conversion factor for the conversion
of NH3-N to NH3, the overall NOEC of
5.36 mg NH3-N/L corresponds to 6.52 mg
NH3/L.
Fairchild
et al. (2005) performed 28 day growth
tests with three fish species: Fathead
Minnow (Pimephales promelas), Colorado
Pikeminnow (Ptychocheilus lucius) and
Razorback Sucker (Xyrauchen texanus).
Toxicity testing was conducted using
methods modified from USEPA (1994).
Tests were initiated 2 d after swim-up
when fish were feeding exogenously
(fathead minnow, 4-d post-hatch;
Colorado pikeminnow, 8-d post-hatch;
razorback sucker, 9-d post-hatch) (i.e.,
similar developmental stages). Fish were
exposed for 28 d in daily static renewal
studies. One-liter test containers were
maintained at constant temperature
(20°C) in CERC well water under a 16-h
light:8-h dark photoperiod. Thirty fish
were exposed to each of five nominal
test concentrations (0, 2.5, 5, 10, and
15 mg/L total ammonia as N; 10 fish per
beaker; n = 3 replicate beakers). Test
solutions were renewed on a daily basis.
The test results were based on measured
concentrations. Endpoints were survival
and growth. The NOEC for Fathead Minnow
(Pimephales promelas), Colorado
Pikeminnow (Ptychocheilus lucius) and
Razorback Sucker (Xyrauchen texanus)
were 0.31, 0.29 and 0.53 mg NH3-N/L.
Applying the conversion factor from
NH3-N to NH3, the NOEC for Fathead
Minnow (Pimephales promelas), Colorado
Pikeminnow (Ptychocheilus lucius) and
Razorback Sucker (Xyrauchen texanus) of
0.31, 0.29 and 0.53 mg NH3-N/L
correspond to 0.377, 0.340 and 0.644 mg
NH3/L, respectively.
All
further studies listed above support that
the NOEC of 0.0135 mg NH3/L is
conservative.
