Chromium - The Risk Assessment Information System

Eco-SSL values for trivalent chromium
were derived for avian and mammalian
wildlife. Eco-SSL values for hexavalent
chromium were derived for mammalian
wildlife. Data were insufficient to
derive Eco-SSLs for plants or soil
invertebrates. The Eco-SSLs for
trivalent chromium range from 26 mg/kg
dry weight (dw) for birds to 34 mg/kg
dw for mammals. The Eco-SSL for
hexavalent chromium for mammals is
equal to 130 mg/kg dw. The Eco-SSL
values are lower than the 50 th percentile
of reported background concentrations
for both eastern and western U.S. soils
(Figure 2.1). Background
concentrations reported for many metals
in U.S. soils are described in Attachment
Conc (mg/kg dw)
1-4 of the Eco-SSL guidance (U.S. EPA, 2003).
140
120
100
3.0 ECO-SSL FOR TERRESTRIAL PLANTS
Eco-SSL for Chromium 3
April 2008
80
60
40
20
0
East West
Figure 2.1 Typical Background
Concentrations of
Chromium in U.S. Soils
Of the papers identified from the literature search process, 150 were selected for acquisition for
further review. Of those papers acquired, 11 met all 11 Study Acceptance Criteria (U.S. EPA,
2003; Attachment 3-1). Each of these papers were reviewed and the studies were scored
according to the Eco-SSL guidance (U.S. EPA, 2003; Attachment 3-2). Thirteen studies
received an Evaluation Score greater than ten. These studies are listed in Table 3.1. An Eco-
SSL for terrestrial plants could not be calculated from these studies as the endpoints are not
acceptable for Eco-SSL derivation (U.S. EPA, 2003). The endpoints are either unbounded
values, or EC 50 values (concentration adversely affecting 50% of the test population) or values
that could not be determined.
4.0 ECO-SSL FOR SOIL INVERTEBRATES
Maximum
95th
75th
50th
25th
5th Percentile
Of the papers identified from the literature search process, 31 were selected for acquisition for
further review. Of those papers acquired, 4 met all 11 Study Acceptance Criteria (U.S. EPA,
2003; Attachment 3-1). Each of these papers were reviewed and the studies were scored
according to the Eco-SSL guidance (U.S. EPA, 2003; Attachment 3-2). Two studies received an
Evaluation Score greater than ten. These studies are listed in Table 4.1. There are only two
studies eligible for Eco-SSL derivation. At least three studies are required to derive an Eco-SSL
for soil invertebrates (U.S. EPA, 2003; Attachment 3-2). An Eco-SSL for soil invertebrates
could not be calculated for chromium.