Academic journal article Environmental Health Perspectives

Investigating Childhood Leukemia in Churchill County, Nevada

Academic journal article Environmental Health Perspectives

Investigating Childhood Leukemia in Churchill County, Nevada

Article excerpt

BACKGROUND. Sixteen children diagnosed with acute leukemia between 1997 and 2002 lived in Churchill County, Nevada, at the time of or before their illness. Considering the county population and statewide cancer rate, fewer than two cases would be expected.

OBJECTIVES. In March 2001, the Centers for Disease Control and Prevention led federal, state, and local agencies in a cross-sectional, case-comparison study to determine if ongoing environmental exposures posed a health risk to residents and to compare levels of contaminants in environmental and biologic samples collected from participating families.

METHODS. Surveys with more than 500 variables were administered to 205 people in 69 families. Blood, urine, and cheek cell samples were collected and analyzed for 139 chemicals, eight viral markers, and several genetic polymorphisms. Air, water, soil, and dust samples were collected from almost 80 homes to measure more than 200 chemicals.

RESULTS. The scope of this cancer cluster investigation exceeded any previous study of pediatric leukemia. Nonetheless, no exposure consistent with leukemia risk was identified. Overall, tungsten and arsenic levels in urine and water samples were significantly higher than national comparison values; however, levels were similar among case and comparison groups.

CONCLUSIONS. Although the cases in this cancer cluster may in fact have a common etiology, their small number and the length of time between diagnosis and our exposure assessment lessen the ability to find an association between leukemia and environmental exposures. Given the limitations of individual cancer cluster investigations, it may prove more efficient to pool laboratory and questionnaire data from similar leukemia clusters.

KEY WORDS: ALL, AML, Churchill County, cancer cluster, environment, Fallon, leukemia, tungsten. Environ Health Perspect 115:151-157 (2007). doi:10.1289/ehp.9022 available via http://dx.doi.org/ [Online 30 November 2006]

Introduction

Acute lymphocytic leukemia (ALL) is the most commonly diagnosed pediatric cancer in the United States (American Cancer Society 2005; Linet et al. 1999; Sandler and Ross 1997). Established risk factors such as ionizing radiation and prenatal exposure to volatile organic compounds (VOCs) do not explain most ALL diagnoses (Belson et al. 2006; Greaves 1997; Linet and Cartwright 1996). For the most part, clustering of children diagnosed with ALL has been attributed to chance (Boyle et al. 1996; Caldwell 1990; Caldwell and Heath 1976). However, when a county of 26,000 people incurred more than a dozen leukemia diagnoses during a 4-year period in which fewer than two cases were expected, an investigation seemed warranted [Nevada State Health Division (NSHD) 2001; Steinmaus et al. 2004).

Potential environmental exposures. The city of Fallon (population 8,000) is the only urban center in Churchill County, Nevada. The Naval Air Station-Fallon (NAS Fallon) contributes an additional 3,000 residents to the city's population. The local community identified four major areas of concern related to environmental exposures. A pipeline runs through downtown Fallon, delivering a continuous supply of JP-8 jet fuel to the base. Both municipal and NAS water supplies have historically reported naturally occurring arsenic levels that exceed U.S. Environmental Protection Agency (U.S. EPA) standards (Welch and Lico 1998; Welch et al. 1989). Fallon is also a center for melon and alfalfa production, and agricultural pesticides are applied to fields surrounding the city. Two facilities related to tungsten refining and use are located in Churchill County: An administrative center and laboratory are in downtown Fallon, and a tungsten carbide processing plant is 11 miles north of Fallon [Agency for Toxic Substances and Disease Registry (ATSDR) 2003].

Initial identification of the cluster. In July 2000, an astute local health care provider notified state health officials that several Churchill County children had recently been diagnosed with leukemia. …

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