Table 1.

Overview of included studies. As detailed in Figure 1, 59 peer-reviewed scientific articles met the criteria for inclusion in this systematic review, and here we provide key metadata for each of these studies. Additional details are in the Supplemental Materials, including a list of all the included articles.

Regions	Countries	Metals Analyzed	Studies	Sample Type and Size	Sample Area
Oceania	Australia	As, Cd, Pb, Cr	1	-Well water (n = 372)	-Recycling site -Residential area
Africa	Ghana	As, Cd, Pb, Cr, Hg	5	-Soil (n = 716) -water (borehole, stream, spring, tap well) (n = 240)	-Recycling site -Around recycling site -Abandoned recycling site -Dumping recycling site -Free recycling site
	Nigeria	As, Cd, Pb, Cr	4	-Soil (top, middle, deep) (n = 633) -water (tap, well) (n = 132)
Asia	China	As, Cd, Pb, Cr, Hg, MeHg, T-Hg	42	-Soil (top, middle, deep, farmland, forest) (n = 4060) -Water (well, drinking, pond, fresh) (n = 505) -Sediment (dust, river) (n = 1055)	-Recycling site -Around recycling site -Abandoned recycling site -Dumping recycling site -Free recycling site -Residential area
	India	As, Cd, Pb, Cr, Hg	2	-Soil (n = 165) -Well water (n = 50)
	Japan	Cd, Pb	1	-Soil farmland soil (n = 40)
	Pakistan	Pb	1	-Soil (n = 3)
	Philippines	Pb	1	-Soil (n = 56)
	Thailand	Pb, Cr	2	-Soil (n = 75) -Water (n = 48)
	Vietnam	Cd, Pb	1	-Sediment (dust) (n = 48) -Soil (n = 48)
South America	Uruguay	Pb	1	-Soil (40)	-Residential area
Total	-	-	62 *	-	-

* In Table 1 the total of studies is 62 instead of 59 because 2 studies were both conducted in 2 different countries, thus duplicating a study for 2 countries.