Academic journal article Environmental Health Perspectives

Rice Consumption and Squamous Cell Carcinoma of the Skin in a United States Population

Academic journal article Environmental Health Perspectives

Rice Consumption and Squamous Cell Carcinoma of the Skin in a United States Population

Article excerpt

Introduction

The potential human health risk posed by arsenic (As)-contaminated rice consumption has recently emerged as a threat to food safety (Zhu et al. 2008). Arsenic is a known human carcinogen (IARC 1987; Straif et al. 2009) that can naturally occur in groundwater used to irrigate paddy field soils supporting rice crops (Meharg and Rahman 2003). The high As content in rice is due to its uptake via a silicon transport system with an affinity for inorganic As (iAs) (Ma et al. 2008; Mitani et al. 2009). Inorganic forms of As, arsenate (AsV) and arsenite (AsIII), are generally considered to exhibit a higher degree of acute human toxicity and carcinogenicity than organic arsenical compounds, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) (Straif et al. 2009). However, some animal studies suggest trivalent forms of methylated arsenic species may be at least as toxic as arsenite (Styblo et al. 2000). Rice also may contain DMA, which is excreted through the kidneys (Gilbert-Diamond et al. 2011); and urinary DMA concentrations have been associated with an increased risk of skin lesions in Bangladesh (Ahsan et al. 2007; Kile et al. 2011; Lindberg et al. 2008), Taiwan (Yu et al. 2000), Mexico (Valenzuela et al. 2005), and China (Zhang et al. 2014). Arsenobetaine, an unmetabolized form of arsenic found in fish and seafood, is considered nontoxic (Francesconi et al. 2002).

Cutaneous squamous cell carcinoma (SCC) is a common keratinocyte cancer (KC), with increasing incidence rates reported in the United States (Glass and Hoover 1989; Karagas et al. 2006; Karia et al. 2013; Kwa et al. 1992), and carries considerable morbidity and health care costs (Rogers et al. 2010; Rogers et al. 2015). Ultraviolet light, fair skin pigmentation, male gender, and elderly age are primary risk factors for SCC (Karagas et al. 2006); however, environmental exposure to As through contaminated drinking water is known to manifest KCs and arsenical skin lesions (e.g., hyperpigmentation, hypopigmentation, keratosis, melanosis), even at relatively low water As concentrations (Karagas et al. 2015). Recent evidence from Bangladesh suggests that rice containing As may contribute to the occurrence of these lesions (Melkonian et al. 2013).

Rice is a staple food throughout the world, including the United States where rice consumption has increased in recent years (Batres-Marquez et al. 2009). Numerous studies have indicated that rice consumption contributes to dietary As intake and internal As dose (Cleland et al. 2009; Davis et al. 2012; Gilbert-Diamond et al. 2011). However, limited epidemiologic research exists on the potential oncogenic role of rice consumption. Therefore, as part of a U.S. population-based case-control study, we sought to investigate the association between the frequency of rice consumption in relation to urinary arsenic concentrations and incident SCC. We further assessed whether any observed association between rice consumption and SCC was modified by household tap water As concentrations.

Methods

Study Population

The New Hampshire Skin Cancer Study population and methods have been described in detail elsewhere (Karagas et al. 1998; Karagas et al. 1999; Karagas et al. 2006; Karagas et al. 2010). Briefly, histologically confirmed, incident SCC cases were identified through active surveillance of dermatology and pathology laboratories throughout the state of New Hampshire, United States. We selected SCC cases diagnosed between July 2007 and July 2009. Controls were chosen from lists of New Hampshire residents obtained from the New Hampshire Department of Transportation (<65 y of age) and Medicare enrollment lists (>65 y of age), and frequency-matched to the age (25-34, 35-44, 45-54, 55-64, 65-69, and 70-74 y) and gender distribution of cases. To be eligible, participants were required to be residents of New Hampshire, 25-74 y of age at the time of diagnosis, speak English, and have a listed telephone number. …

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