Table 2.

Studies (Author year) reporting association of toenail essential trace metals to personal characteristics and non-dietary exposures.

Metal	Personal characteristics					Non-dietary lifestyle & social factors			Other environmental exposures
	Age	Sex	Ethnicity	BMI	Reproductive factors	Physical activity	Tobacco use	Socloecon/Educative level	Water	Residential exposure	Dust/Air	Occupational Exposure →	Time since exp
CO	▼ Rakovic 1997	♂ Rakovic 1997 Slotnick 2005 Sureda 2017				▴ ♀ Sureda 2017			▴ Ndilila 2014 ▼ Chanpiwat 2015	▴ Chanpiwat 2015	▴ Ndilila 2014	▴ Sabbioni 1994 ∅ Menezes 2004a Rakovic 1997 Rainska 2005, 2007
Cu	∅ Slotnick 2005 Reis 2015	♀ Rakovic 1997							▴ McKenzie 1978 Ndilila 2014 Reis 2015 Chanpiwat 2015	▴ Ndilila 2014 Chanpiwat 2015 Mohmand 2015	▴ Ndilila (soil)	▴ Menezes 2004a Rainska 2005
	▼ Rakovic 1997	∅ Masironi 1976 McKenzie 1978 Reis 2015								∅ Reis 2015	∅ Reis 2015
Fe	▼ Rakovic 1997	∅ Rakovic 1997 Sureda 2017		▲ Garland 1996	▼ Garland 1996 Age first birth	▴ ♀-♂ Sureda 2017 Sureda 2017			▴ Chanpiwat 2015	▴ Rakovic 1997 Rainska 2007 Were 2009		▴ Rakovic 1997
Mn	▲ Laohaudomchok 2011 Coelho 2014		▲ White Laotiaudomchok 2011 Mordukovitch 2012		▲ Rodrigues 2015 Parity		▲ Coelho 2014	▲ Rodrigues 2015	▲ Chanpiwat 2015 Rodrigues 2015 Ntihabose 2017	▲ Rakovic 1997 Coelho 2012 Coelho 2014 Sanders 2014 Chanpiwat 2015	▲ Reis 2015	▲ Menezes 2004b Laohaudomchok 2011 Coelho 2012,2014 Grashow 2014 Hassani 2016 Ward 2017	→7–12 m →7–9 m →7–12 m
	∅ Grashow 2014 Ward 2017	∅ Masironi 1976 Reis 2015		∅ Ward 2017			∅ Wongwit 2004 Grashow 2014 Ward 2017			∅ Reis 2015	∅ Hassani 2016	∅ Rakovic 1997 Raińska 2005
	▼ Masironi 1976 Slotnick 2005 Reis 2015	♀ Rakovic 1997 Coelho 2014					▼ Rakovic 1997
Mo	∅ Nouri 2008 ▼ Rakovic 1997	♀ Rakovic 1997							▲ Chanpiwat 2015	▲ Nouri 2008	▲ Rakovic 1997	▲ Rakovic 1997 ∅ Rainska 2005
Se	▲ Slotnick 2005 Rayman 2015	♂ Park 2011	▲ White Kristal 2014 Everson 2017♀	▲ Park 2011	▲ Van Noord 1993 Parity Hunter 1990b Age menarche			▲ Xun 2010b, 2011 Colangelo 2014 Rayman 2015	▲ Emmanuelle 2012	▲ Morris 1983 Hunter 1990a Yoshizawa 1998 Michaud 2002 Morris 2006 Xun 2010b, Xun 2011 Park 2011, Emmanuelle 2012 Ndilila 2014 Colangelo 2014 Hashemian 2017
	∅ Swanson 1990 Vanl Veer 1990 Alfthan 1992 Ovaskainen 1993 Van der Brandt 1993b Kardinaal 1997 Lipsky 2004 Satia 2006 Morris 2001,2006 Xun 2010a Colangelo 2014 Kristal 2014 Everson 2017 Hashemian 2017	∅ Satia 2006 Sureda 2017	∅ Satia 2006	∅ Hunter 1990a Ovaskainen 1993 Van der Brandt 1993b Kardinaal 1997 Lipsky 2004 Morris 2006 Satia 2006 Colangelo 2014 Kristal 2014 Hashemian 2017	∅ Krogh 2003 Menopausal status	∅ Satia 2006 Xun 2010a Hashemian 2017 Sureda 2017	∅ Ovaskainen 1993 Virtanen 1996 Lipsky 2004 Everson 2017			∅ Coelho 2014		∅ Coelho 2014
	▼ Hunter 1990a Garland 1995 Żukowska 2009 Park 2011 Park K 2016 Jang 2017	♀ Swanson 1990 Van der Brandt 1993b Baskett 2001 Morris 2001,2006 Raińska 2007 Żukowska 2009 Xun 2010a, b Lee 2016	▼ Afroamerican Xun 2010a, 2011 Colangelo 2014 Kristal 2014	▼ Żukowska 2009 Xun 2010a Vinceti 2015			▼ Hunter 1990a,b Swanson 1990 Van der Brandt 1993b Van Noord 1993 Garland 1995 Virtanen 1996 Kardinaal 1997 Ghadirian 2000 Krogh 2003 Morris 2001,2006 Satia 2006 Żukowska 2009 Park 2011 Xun 2010a,b,2011 Emmanuelle 2012 Colangelo 2014	▼ Everson 2017
V	▼ Masironi 1976 Rakovic 1997 Slotnick 2005	∅ Masironi 1976 ♀ Rakovic 1997 Slotnick 2005								∅ Raińska 2007		∅ Menezes 2004a Raińska 2005
Zn	▲ Garland 1996 Martin Moreno 2003 Park JS 2016	♂ Campos 2008 Gonzalez 2008				▲ Park JS ♀ 2016 Sureda 2017	▲ Campos 2008	▲ Park JS 2016		▲ Wilhelm 1991 Nouri 2008 Were 2009 Ndilila 2014 Mohmand 2015	▲ Raińska 2005 Ndilila 2014	▲ McKenzie 1979
	∅ Nouri 2008 Campos 2008 Gonzalez 2008 Hashemian 2017	∅ McKenzie 1978 Rakovic 1997 Przybylowicz 2012 Park JS 2016 Hashemian 2017 Meramat 2017 Sureda 2017	∅ Gonzalez 2008	∅ Vinceti 2015 Park JS 2016 Hashemian 2017		∅ Hashemian 2017	∅ Martin Moreno 2003 Park JS 2016	∅ Hashemian 2017	∅ McKenzie 1978 Chanpiwat 2015			∅ Rakovic 1997 Raińska 2005
	▼ Rakovic 1997 Coelho 2014	♀ Bergomi 2002 Raińska 2007 Lee 2016	▼ Afroamencan Park JS 2016					▼ Martin Moreno 2003

▲ : Positive; ∅: No association; ▼: Negative; BMI: body max index; Socioecon: socioeconomic; exp: exposure; ♀: women; ♂: men.