The Relationship between Residential Lead Exposures and Elevated Blood Lead Levels in a Rural Mining Community

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Abstract

An 80-year history of lead mining in rural northeastern Oklahoma has resulted in widespread coverage of residential areas with mine waste from wind-blown dispersion of mined materials and deliberate use of tailings in construction and road maintenance. For this study, environmental samples (soil, dust, paint, water) were collected with standardized techniques from a population-based random sample of 245 residences as part of a blood lead screening project. Nearly 50 percent of study homes contained lead-based paint. Lead in floor dust exceeded the U.S. Department of Housing and Urban Development (HUD) standard in approximately 10 percent of the homes, and in over 20 percent, yard soils had lead levels above the U.S. Environmental Protection Agency (U.S. EPA) standard. Multivariate analysis of environmental and blood lead data found that four variables were independently associated with elevated blood lead levels: floor dust (odds ratio [OR] = 8.1, and confidence interval [CI] = 1.8, 37.8); yard soil (OR = 6.4 , and CI = 1.4, 30.7); interior paint (OR = 3.0, and CI = 1.2, 7.8); and location of residence (OR = 3.4, and CI = 1.3, 8.8). These data demonstrate that effective residential remediation strategies must address paint, dust, and yard soils. The environmental assessment also found that nearly 20 percent of homes outside the mining area had contaminated soil, indicating that soil remediation efforts will have to extend beyond the current boundaries of the Superfund site.

Introduction

The relatively high prevalence of elevated blood lead levels in children is a major environmental health problem in the United States [1]. Although the prevalence has been dropping, elevated blood lead levels are still a major problem, with 4.4 percent of children one to five years of age, or 890,000, having blood lead levels greater than or equal to 10 micrograms per deciliter ([micro]g/dL) [1-4]. Elevated blood lead levels pose a particular threat to young children (less than seven years of age) by impairing the development of neurological systems, resulting in reduced cognitive development [5-10]. This condition appears to be irreversible [11,12]. The long-term cost to society for lead-based childhood impairments is estimated to be 6.9 billion dollars per year [13].

There are many potential sources of lead exposure in the environment. Lead-based paint is most often cited as the primary source of lead exposure for children in the United States since it is present in over 60 percent of homes built before 1979 and 80 percent of homes built before 1959 [14]. Children can be exposed to lead-based paint directly, from ingestion of paint chips (pica), or, more importantly indirectly, through ingestion of dust from deteriorated paint [15,16]. Although lead-based paint was banned for residential use in 1978, there remain approximately 77 million structures with lead-based paint, 14 million of which contain paint in unsound condition, and 3.8 million of which are occupied by young children [14].

Other important sources of lead exposure in the United States are soil and dust with soil origins. Soil can become contaminated with lead via deteriorating paint or lead-containing gasoline; however, in many small towns and rural areas throughout the country, significant quantities of lead in the soil derive from the historical mining and smelting of lead, zinc, silver, and other metals. Ultimately, the identification of the primary sources of lead and their relative contributions to elevated blood lead levels are important for developing effective primary lead-poisoning prevention strategies. Previous research has focused primarily on urban communities, where paint and resulting dust were the primary sources of lead. Communities affected by mining may require different prevention strategies, depending on the relative contribution of lead sources. Several studies have shown a positive relationship between mining activities, high soil lead concentrations, and elevated blood lead levels in children [17-21]. Du st has also been shown to be a significant contributor to elevated blood lead levels in children in mining communities and urban areas [22-25].

The site of the current study is the tri-state mining region of northeast Oklahoma, southeast Kansas, and southwest Missouri, which was the world's largest producer of lead and zinc between 1850 and 1950 [26]. Lead mining began in eastern Missouri in the early 1700s, spread westward, and was a well-developed industry by the early 1800s [27]. Commercial mining in Oklahoma began in 1891 and continued until the early 1970s, when environmental concerns and reduced yields resulted in the collapse of the industry. The legacy of these mines in Oklahoma is approximately 45 million cubic yards of …