Toenails as a biomarker of exposure to arsenic: A review

Abstract

This systematic review summarizes the current evidence related to the reliability of toenail total arsenic concentrations (thereafter "arsenic") as a biomarker of long-term exposure. Specifically, we reviewed literature on consistency of repeated measures over time, association with other biomarkers and metal concentrations, factors influencing concentrations, and associations with health effects. We identified 129 papers containing quantitative original data on arsenic in toenail samples covering populations from 29 different countries. We observed geographic differences in toenail arsenic concentrations, with highest median or mean concentrations in Asian countries. Arsenic-contaminated drinking water, occupational exposure or living in specific industrial areas were associated with an increased toenail arsenic content. The effects of other potential determinants and sources of arsenic exposure including diet, gender and age on the concentrations in toenails need further investigations. Toenail arsenic was correlated with the concentrations in hair and fingernails, and with urine arsenic mainly among highly exposed populations with a toenail mean or median ≥1 μg/g. Overall, there is a growing body of evidence suggesting that arsenic content from a single toenail sample may reflect long-term internal dose-exposure. Toenail arsenic can serve as a reliable measure of toxic inorganic arsenic exposure in chronic disease research, particularly promising for cancer and cardiovascular conditions.

Keywords: Arsenic; Biomarker; Biomonitoring; Exposure; Toenail.

Figure 1:

Arsenic concentrations (arithmetic mean or median, μg/g) in human toenails (1993 – 2017). The green circles and red crosses refer to the minimum and maximum values of toenail arsenic in population subgroups assessed in the reviewed study. The empty rhombus refers to the overall value of toenail arsenic reported in the reviewed study. The number within brackets refers to the overall size of the study population, and when this information is not available (n.a.). The studies are sorted by country, year, and first author’s name. UK = United Kingdom; USA = United States of America.

Figure 2:

Median arsenic content natural log transformed in toenails according to country based on the reported arithmetic mean/median value. The colors from yellow to red refer to the log-transformed median toenail arsenic concentrations calculated using the overall mean/median value reported in the included studies. The mean toenail arsenic concentrations were available for Australia (Swab - coastal Plain) (Hinwood et al., 2008), Bangladesh (Sirajdikhan and Pabna regions; Marua in Jessore; Dutpatila and Vultie in Chuadanga; Bheramara in Kushtia; Chowkoli in Naogaon; Communities served by Dhaka Community Hospital; Achintanagar in Jhenaidah) (Ali et al., 2010; Breton et al., 2007a; 2007b; Hasibuzzaman et al., 2017; Hossain et al., 2012; Huda et al., 2014; Karim et al., 2013, 2010; Kato et al., 2013; Lin et al., 2017; McCarty et al., 2007; Pan et al., 2013; Rahman et al., 2017; Rakib et al., 2013; Rodrigues et al., 2015; Seow et al., 2012; Tauheed et al., 2017), Cambodia (Sambour, Preak Chrov, Prey Veng, Chang Kaoh and Kampong Toul in Kandal; Mekong River basin) (Chanpiwat et al., 2015; Phan et al., 2011), Canada (Nova Scotia; Québec) (Dummer et al., 2015; Gagnon et al., 2016; Lampron-Goulet et al., 2017; McIver et al., 2015), China (Inner Mongolia; Ba Men region) (Mumford et al., 2007; Otto et al., 2007; Schmitt et al., 2005; Wade et al., 2015), Czech Republic (City of Prague) (Rakovic et al., 1997), India (West Bengal; 20 km south of Calcutta) (Maity et al., 2012; Nath et al., 2008), Iraq (Communities served by Fallujah Central Hospital)(Al-Sabbak et al., 2012), Korea (Seoul; Kyunggido) (Lee et al., 2016), Malaysia (Saat et al., 2013), Mexico (Comarca Lagunera) (Gonzalez-Cortes et al., 2017), Pakistan (Lahore and Sargodha of Punjab province; Northern Frozen Mountainous; Lower Himalyian Wet Mountainous; Alluvial Riverine; Low lying zone) (Alamdar et al., 2016; Subhani et al., 2015), Poland (Gdansk; Southwestern part of Poland) (Lewińska et al., 2007; Raińska et al., 2007, 2005), Portugal (Panasqueira Mine Area) (Coelho et al., 2014, 2012), Qatar (Kuiper et al., 2014), Spain (Mediterranean coast) (Amaral et al., 2012), Taiwan (Meicheng, and Meifu Village in Lanyang Basin) (Chiou et al., 1997), Thailand (Ron Phibul District, Nakhon Sri Thammarat Province) (Hinhumpatch et al., 2013; Intarasunanont et al., 2012; Phookphan et al., 2017), Uganda (Kilembe mine located 10 km of Kasese town) (Mwesigye et al., 2016), United Kingdom (Nottingham area) (Watts et al., 2009), United States of America (Arizona; 11 states; Across US; Michigan; Massachusetts; New Hampshire; Arizona; Nevada; Maine; New Mexico) (Beamer et al., 2016; Burgess et al., 2014; Calderon et al., 2013; Cottingham et al., 2013; Farzan et al., 2015, 2016, 2017; Garland et al., 1993; Grashow et al., 2014b; Gruber et al., 2012; Josyula et al., 2006; Karagas et al., 2012; Lesseur et al., 2012; MacIntosh et al., 1997; Nichols et al., 1998; Nygaard et al., 2017; Slotnick et al., 2008b, 2005; Wasserman et al., 2014; Wong et al., 2014, 2015; Yager et al., 2016), and Vietnam (Nghia Lo village) (Sanders et al., 2014). For the following countries the mean toenail arsenic concentrations were not available, thus the median concentrations were used: Brazil (São Paulo City) (Aguiar and Saiki, 2001), Finland (Michaud et al., 2004), and France (Goullé et al., 2009).