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

solution and minimal translocation of Pb from roots to shoots (Påhlsson, 1989). Although many
laboratory toxicity studies have reported effects on plants, there are few reports of phytotoxicity
from Pb exposure under field conditions. For example, Leita et al. (1989) and Sieghardt (1990)
reported high concentrations of Pb and other metals in soil and vegetation collected around
mining areas in Europe, with no toxicity symptoms observed in plants or fruit.
The literature search completed for the terrestrial plant Eco-SSL development identified
439 papers for detailed review, of which 28 met the minimum criteria (U.S. Environmental
Protection Agency, 2005a). Thirty ecotoxicological endpoints were gleaned from these 28
papers and were further evaluated; most of those evaluated growth (biomass), which was
considered the most sensitive and ecologically relevant endpoint (U.S. Environmental Protection
Agency, 2005b). Five of the endpoints, representing four species tested under three different
combinations of pH and organic matter content, were used to develop the Eco-SSL of 120 mg/kg
(115 mg/kg rounded to two significant digits) (Table AX7-1.3.1).
Table AX7-1.3.1. Plant Toxicity Data Used to Develop the Eco-SSL
Plant Species Soil pH
AX7-62
% Organic
Matter
Toxicity
Parameter
Pb in Soil
(mg/kg dw)
Loblolly pine (Pinus taeda) 4 2.5 MATC * (growth) 144
Red maple (Acer rubrum) 4 2.5 MATC (growth) 144
Berseem clover
(Trifolium alexandrium)
6.3 0.94 MATC (growth) 316
Berseem clover 6.7 3.11 MATC (growth) 141
Rye grass (Lolium rigidum) 5.6 0.1 MATC (growth) 22
Geometric Mean 115
*MATC = Maximum Acceptable Threshold Concentration, or the geometric mean of the NOAEC
(no-observed-adverse-effect concentration) and LOAEC (lowest-observed-adverse-effect concentration).
Source: U.S. Environmental Protection Agency (2005b).
The 25 ecotoxicological endpoints that were not used to develop the Eco-SSL for plants
are presented in Table AX7-1.3.2. The first six endpoints were considered eligible for Eco-SSL
derivation but were not used; the remainder did not meet all of the requirements to be considered
for inclusion in the Eco-SSL derivation process.