Dm. Proctor et al., HEALTH-BASED SOIL ACTION LEVELS FOR TRIVALENT AND HEXAVALENT CHROMIUM- A COMPARISON WITH STATE AND FEDERAL-STANDARDS, Journal of soil contamination, 6(6), 1997, pp. 595-648
As part of the Brownfields initiatives being enacted at both the state
and federal levels, environmental regulatory agencies are developing
health-based screening or action levels to facilitate the reclamation
of unused industrial properties. By the end of 1997, approximately 90%
of the states will have either adopted federal values or developed th
eir own non-site-specific action levels. These standards can be applie
d as default cleanup levels, or alternative remediation standards may
be developed based on a site-specific risk assessment. A state and fed
eral survey of cleanup levels for hexavalent and trivalent chromium [C
r(VI) and Cr(lll)] indicated a general concurrence of approaches (i.e.
, most states are using the USEPA standard risk assessment model with
upper-bound estimates of exposure and USEPA toxicity criteria), althou
gh the proposed values vary by as much as 5 orders of magnitude. To un
derstand the variability and uncertainty in these levels, the USEPA So
il Screening Level (SSL) (1996a) equations were calculated for Cr(lll)
and Cr(VI) by Monte Carlo analysis to develop probability density fun
ctions of health-based action levels (HBALs) for residential and indus
trial land uses. The lowest HBALs were developed for Cr(VI) for the in
halation of particulates pathway (residential = 892 mg/kg; non-residen
tial = 105 mg/kg); therefore, states and regions that do not consider
this pathway may have cleanup standards for Cr(Vi) that are not adequa
tely protective of public health. It was determined that Cr(lll) HBALs
are not necessary (lowest value calculated was 178, 000 mg/kg fora re
sidential site) due to the very low toxicity of Cr(lll). HBALs for the
protection of groundwater are extremely variable, and a tiered approa
ch similar to that developed by the USEPA for the SSL framework, which
allows for incorporation of some site-specific information, is most a
ppropriate.