79    INDUSTRIAL WASTES AND SOIL LEAD
CONCENTRATIONS AS A BASIS FOR REMEDIAL OR
OTHER ACTION
Bobby G. Wixson, Professor
Akbar Ghazifard, Graduate Research Assistant
Environmental Research Center
University of Missouri-Rolla
Rolla, Missouri 65401
Brian E. Davies, Professor
School of Environmental Science
University of Bradford
Bradford, W. Yorkshire, England BD7 1DP
INTRODUCTION
The valuable aspects and beneficial utilization of lead are well known, along with the potential
health hazards which may be associated with elevated concentrations of lead in air, water, soil or
foods. Lead contamination may occur in many different ways or through diverse pathways. Constant
monitoring is required to control undue exposure and to prevent lead poisoning. Recently lead has
become one of the major concerns in hazardous or toxic wastes associated with uncontrolled dumping. Workable guidelines are needed to determine the level of remedial action needed to clean up such
sites.
At the present time the U.S. has not established interim guidelines for lead in soil. Previous research
has shown that the removal of persistent substances, such as lead from soil, may be very expensive.
Therefore, tentative guidelines need to be realistic, environmentally safe and protective of human
health. One needs to know how clean is clean in order that remedial action at identified lead contaminated sites may proceed as soon as possible.
In the absence of acceptable guidelines such action may be confusing, expensive, and questionable.
Suggested protective measures from other countries have been evaluated and provisional guidelines
may be recommended based on scientific data, projected end land use, and other parameters noted
during an on-site-specific evaluation for the protection of the population at risk.
EXISTING GUIDELINES
In an attempt to determine the normal range of lead in soils, non-selective and statistical
approaches have been used by Shacklette et al.1 with later studies by Shacklette and Boerngen2 which
indicated a mean soil lead concentration of 16 /ig/g with the 99.7% upper limit of 103 /ig/g. Davies3
and Davies and Paveley4 found that the average soil lead content for old lead mining areas in England
and Wales were 42 to 106 /tg/g. Research by Davies and Wixson5 in Madison County, Missouri, an old
base metal mining district, found that the mean soil lead content for background population was 50 to
178 /ig/g. Research findings suggest that any soil containing more than 120 /ig Pb/g can be considered
as contaminated (above background) but not necessarily presenting a biological hazard until a much
higher critical concentration is reached.
The question of what might comprise a critical soil concentration has been addressed by several
different countries and research groups.
The British Department of the Environment (DOE) has proposed guidelines for the redevelopment
of lands which may have been chemically contaminated. Based on research, health impacts historical
information, and listing of contaminants most likely to present hazards to human health, the British
DOE has proposed the concept of "trigger concentrations" of 500 /ig/g lead for gardens and allotments and 2,000 ^g/g lead for parks, fields, and open spaces. Sites below these values could be
regarded as presenting no additional risk to a critical group.6 However, these recommendations are
787