Academic journal article Environmental Health Perspectives

Cadmium Exposure and Cancer Mortality in a Prospective Cohort: The Strong Heart Study

Academic journal article Environmental Health Perspectives

Cadmium Exposure and Cancer Mortality in a Prospective Cohort: The Strong Heart Study

Article excerpt

Introduction

Cadmium (Cd) is a widespread metal that is highly toxic to humans. Cd pollution in soil, air, and water is ubiquitous because of Cd use in industrial products (e.g., batteries, coatings, plastic stabilizers), contamination of phosphate fertilizers, and release from motor vehicle fuel combustion and tire wear (Agency for Toxic Substances and Disease Registry 2011). Soil contamination is a major health problem because grains and leafy and root vegetables bioconcentrate Cd, resulting in major sources of Cd exposure through diet and smoking.

Cd is classified as a human carcinogen by the International Agency for Research on Cancer (IARC 1993). Cd exposure has been associated with lung cancer incidence in a population living in a Cd-polluted area (Nawrot et al. 2006) and with lung cancer

incidence and mortality in occupationally exposed populations (Jarup et al. 1998; Park et al. 2012). In experimental models, Cd acts as an endocrine disruptor (Martin et al. 2002; Siewit et al. 2010), supporting the hypothesis that this metal can potentially induce the development of hormonedependent tumors in humans, including those of the breast, uterus, and prostate (Akesson et al. 2008; Benbrahim-Tallaa et al. 2009; Bertin and Averbeck 2006). In occupationally exposed women, Cd has been associated with increased breast cancer incidence (Pollan and Gustavsson 1999) and breast cancer mortality (Cantor et al. 1995). In other studies, however, occupational Cd exposure was not associated with breast cancer incidence or mortality (Jarup et al. 1998; Kauppinen et al. 2003). Some evidence also suggests that occupational Cd exposure may be a risk factor for kidney (Il'yasova and Schwartz 2005) and pancreatic cancers (Schwartz and Reis 2000).

Less is known about the carcinogenicity of Cd at low-to-moderate levels of exposure. In the Third National Health and Nutrition Examination Survey (NHANES) (19881994), urinary Cd (U-Cd) was associated with total cancer mortality over a period of 13.5 years of follow-up (Adams et al. 2012). In men, Cd was associated with cancers of the lung and pancreas and with non-Hodgkin lymphoma, but not with prostate cancer; whereas in women, Cd was associated with cancers of the lung, ovaries, and uterus and with leukemia, but not with breast cancer (Adams et al. 2012). Cd exposure, however, has been associated with breast cancer in women from general populations in Sweden (Julin et al. 2012a) and the United States (Gallagher et al. 2010; McElroy et al. 2006) and with endometrial cancer (Akesson et al. 2008).

Cancer is the second leading cause of death in American Indians (Centers for Disease Control and Prevention 2013). During 1999-2008, cancer death rates declined by > 1% per year in every American ethnic/racial group with the exception of American Indians (Siegel et al. 2012). Few studies, however, have evaluated the cancer burden and its determinants in this population. The main objective of the present study was to evaluate the association of U-Cd concentrations with overall and site-specific cancer mortality in American Indian adults who participated in the Strong Heart Study (SHS) during 1989-1991 and were followed through 2008. In the present study, we assume that U-Cd is a biomarker of long-term Cd exposure (Jarup and Akesson 2009). In addition to diet and smoking, other sources of Cd exposure for American Indian populations include living in the vicinity of industrial sites and mining areas (Moon et al. 1986; Schmitt et al. 2006), surface dust in jewelry-making homes (Gonzales et al. 2004), and small-scale motor vehicle repair (Yassin and Martonik 2004).

Methods

Study population. From 1989 through 1991, men and women 45-75 years of age from 13 American Indian communities were invited to participate in the SHS. In Arizona and Oklahoma, every eligible person was invited; whereas in North and South Dakota, a cluster sampling technique was used (Lee et al. …

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