Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

971 ∀ 633 mg/kg, respectively. Significant mortalities were noted at concentrations of 2000
mg/kg. These data are consistent with those reported in the Eco-SSL document (U.S.
Environmental Protection Agency, 2005b) for the same species of earthworm.
Nursita et al. (2005) found no mortality and no adverse effects on reproduction (i.e.,
number of juveniles) of the collembolan Proisotoma minuta exposed for 42 days to 300, 750,
1500, or 3000 mg Pb/kg as Pb-nitrate in an acidic (pH = 4.88) sandy loam soil. It was noted that
the soils were allowed to equilibrate for 4 weeks after adding the Pb-nitrate before the organisms
were added. The observation of no effect at 3000 mg/kg is consistent with that of Sandifer and
Hopkin (1996). Sandifer and Hopkin (1996) determined a NOEC (no-observed-effect
concentration) and LOEC (lowest-observed-effect concentration) for collembolan reproduction
of 2000 and 5000 mg/kg, respectively. (A MATC [maximum-acceptable-threshold
concentration] of 3162 mg/kg was used to develop the Eco-SSL).
The remaining 14 toxicity endpoints that were not used to develop the Eco-SSL for
invertebrates are presented in Table AX7-1.3.6. None of these endpoints was considered eligible
for Eco-SSL derivation.
Lock and Janssen (2002) exposed the potworm Enchytraeus albidus to Pb, as Pb-nitrate.
The 21-day LC50 was 4530 mg/kg, and the 42-day EC50 for juvenile reproduction was
320 mg/kg. The F1 generation was then grown to maturity in the same concentration soil and
subsequently used in a reproduction test. The EC50 for the F1 generation (394 mg/kg) was
similar to that of the P generation. The authors concluded that the two-generation assay did not
increase the sensitivity of the test (Lock and Janssen, 2002). None of the 18 toxicity endpoints
evaluated in detail during development of the Eco-SSLs used this species. The LC50 reported for
the potworm was higher than reported for nematodes and similar to that reported for the
earthworm. The EC50 for reproduction was lower than reported for the earthworm or collembola.
Recent work by Bongers et al. (2004) cautioned against attributing all toxicity observed in
a spiked-soil toxicity test to Pb. They found that the counterion may also contribute to the
toxicity of Pb in the springtail Folsomia candida. This may have implications on the
interpretation of the Eco-SSL data, because the toxicity of the counterion (nitrate) was not taken
into account during Eco-SSL development. Percolation (removal of the counterion) had no
statistically significant effect on Pb-chloride toxicity (LC50 = 2900 mg/kg for both nonpercolated
and percolated soil; EC50 for reproduction = 1900 mg/kg or 2400 mg/kg for
AX7-83