Risk management criteria for metals at BLM mining sites

36 Pages·1996·6.1 MB·English

by  Ford, Karl L

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United States Department of the Interior ag. 210
Bureau of Land Management
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RISK MANAGEMENT CRITERIA
FOR METALS
AT BLM MINING SITES
Karl L. Ford, Ph.D.
Bureau of Land Management
National Applied Resource Sciences Center
Denver, CO
Technical Note 390 (revised)
December 1996
BLM Library
Denver Federal Center
BLM/RS/ST-97/001+1703 Bidg. 50, OC-521
P.O. Box 25047
Denver, CO 80225
ACKNOWLEDGEMENT
Portions of this work were supported by
Dynamac Corporation under contract to the
Bureau of Land Management.
HUMAN HEALTH RISK MANAGEMENT CRITERIA
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RISK MANAGEMENT CRITERIA FOR METALS
AT BLM MINING SITES
Karl L. Ford, Ph.D.
National Applied Resource Sciences Center, Denver, CO
INTRODUCTION
Mining activities have influenced the environment RMC designed to protect human receptors for the
of Public Lands throughout the West. Tailings from metals of concern were developed using available
ore mills have contributed large amounts of heavy toxicity data and standard U.S. Environmental Pro-
metals into air, water, stream sediments, and soils. tection Agency (EPA) exposure assumptions. RMC
Uncontrolled migration of metal-laden mine tail- designed to protect wildlife receptors for the met-
ings via dust entrainment and erosion continues to als of concern were developed using toxicity val-
present potentially adverse risks to human health ues and wildlife intake assumptions reported in the
and wildlife. Recreational demands are increasing current ecotoxicology literature. Ingestion of soil,
on areas where acute and prolonged exposure to sediment, and plants is assumed to be the predomi-
relatively high metal concentrations in soils, sedi- nant source of metal exposure for wildlife recep-
ments, and surface waters is occurring. In some tors.
locations, avian and aquatic kills have been re-
ported. The contaminants of concern and metal contami-
nation migration pathways were identified from
To address these issues, BLM has developed ac- historical information and site visits. Potential re-
ceptable multimedia criteria for the chemicals of
ceptors, receptor exposure routes, and exposure
concern (heavy metals) as they relate to recreational scenarios were identified from on-site visits and
use and wildlife habitat on BLM lands. The pri- discussions with BLM personnel. Representative
mary objective of this report is to establish risk wildlife receptors at risk were chosen using a num-
management criteria (RMC) for human health and ber of criteria, including likelihood of inhabitation
wildlife. Risk management criteria provide numeri- and availability of data.
cal action levels for metals in environmental me-
dia. RMC are designed (1) to assist land managers Risk management criteria should be used by the
in making natural resource decisions and (2) to land manager as a cautionary signal that potential
support ecosystem management. Ecosystem man- health hazards are present and that natural resource
agement is defined as the skillful use of ecological, management or remedial actions are indicated.
economic, social, and managerial principles in man- Furthermore, these criteria may be used as target
aging ecosystems to produce, restore, or sustain cleanup levels if remedial action is undertaken.
ecosystem integrity and desired conditions, uses,
products, or values and services over the long term.
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HUMAN HEALTH RISK MANAGEMENT CRITERIA
A wide range of possible exposure scenarios was 100,000 chance that they would develop any type
examined to represent potential human exposures of cancer in a lifetime as a result of contact with
that might occur on BLM lands. Table 1 provides the metals of concern on BLM lands. A hazard
an overview of the potential human receptors con- index of 1.0 means that the dose of noncancer met-
sidered and the media to which they are assumed als assumed to be received on BLM lands by any of
to be exposed. All exposure factors are presented the receptors in a medium is lower than, or the
in Appendix A. For the most part, the exposure same as, a dose that would not result in any ad-
assumptions used in the calculation of human verse noncancer health effects.
health RMC are those provided in EPA guidance
documents. The risk and hazard levels are consistent with EPA
guidance. The concept behind the RMC is that
The equations for the calculations of the human people will not experience adverse health effects
RMC in soil, sediment, groundwater, surface wa- from metal contamination on BLM lands during
ter, and fish are presented in Appendix A. The their lifetimes if exposure is limited to soil, sedi-
RMC correspond to a generally recognized accept- ments, and waters with concentrations at or less
able level of health risk, specifically an excess can- than the RMC. To calculate this chance, EPA’s
cer risk of 1.0E-05 or a noncancer hazard index of conservative interpretations of cancer data have
1.0. An excess cancer risk of 1.0E-05 means that been used; therefore, the likelihood that this risk
for an individual exposed at these RMC under the has been underestimated is very low.
described exposure conditions, there is only a 1 in
TABLE 1. Human Health Receptors, Media and Exposure Routes
Medium/Exposure Routes
RECEPTOR "Groundwater Surface Water | Sediments Surface Soils Fish
ingestion ingestion ingestion ingestion | inhalation | ingestion
Worker
Contaminant of Concern Selection those factors which have been empirically deter-
mined, such as the number of liters of water an
The contaminant of concern (COC) selection pro- adult drinks in a day, the average rate of inhalation
cesses utilized previous work at mining sites. The of dust, or the average number of years spent in
selection processes in these investigations were sci- one residence. However, several site-specific ex-
entifically rigorous and in accordance with EPA risk posure assumptions have been developed in this
assessment guidance. Therefore, the COCs for report, in addition to the standard EPA assump-
these investigations were combined to form the tions, to provide estimates as closely resembling
COC list for this effort. The COCs for the human probable exposures on BLM property as possible.
health RMC are antimony, arsenic, cadmium, cop-
per, lead, manganese, mercury, nickel, selenium, The residential scenario was developed because
silver, and zinc. there are residential properties adjacent to BLM
land. Contamination may migrate from the BLM
Lead RMC for the resident were determined from tracts to adjoining residential property. All resi-
EPA’s Integrated Exposure Uptake Biokinetic dential scenario exposure assumptions were ob-
Model. This model calculates acceptable lead ex- tained directly from EPA guidance. A variety of
posure via ingestion of soil, drinking water, and recreational exposure scenarios on BLM lands were
food, and via inhalation of air, using 10 ug Pb/dl as also considered, including camping, swimming,
an acceptable blood lead concentration for 95% of boating, and ATV driving. The BLM-specific as-
the exposed child population. Lead criteria for sumptions were made for the recreational expo-
other human receptors were based on available EPA sure scenarios in consultation with BLM field of-
regulation and guidance. fices. Table 2 presents the human health RMC. In
the case of metals posing both cancer and
Exposure Scenarios noncancer threats to health, the lower (more pro-
tective) concentration was selected as the risk man-
The human exposure scenarios were developed to agement criterion.
provide realistic estimates of the types and extent
of exposure which individuals might experience The RMC have been divided by 11 metals and by
to the COCs in the water, soils, and sediments on “n” media that receptors are exposed to (Table 1)
BLM property. Such exposures might occur to to account for multiple chemical and media expo-
individuals living on properties adjacent to BLM sures. This ensures that the cumulative effects of
lands; to individuals who use BLM lands for camp- all the metals and all of the media are considered.
ing, boating, or all-terrain-vehicle (ATV) driving; Therefore, as long as people are not exposed to
or to individuals who work on BLM lands. EPA metals concentrations exceeding the RMC, they
has published a number of standard exposure as- are not expected to experience adverse effects.
sumptions that are consistently used to estimate