Table 2.

Exposure routes and analysis of biological samples as biomarkers in assessing toxic metal exposure.

Study area	Subject	Exposure route	Sample	Analysis subject	Reference
Iraq	Smokers	Smoking: inhalation	Urine	Cr, Cd, Pb	[26]
Pakistan	Chromite mining workers	Air: dermal contact, inhalation and ingestion	Blood & Urine	Cr, Cd, Pb, Mn, Zn	[8]
Thailand	Electronic waste workers	Air: dermal contact, inhalation and ingestion	Blood & Urine	Cd, Mn, Pb	[27]
Pakistan	Lather tanning workers	Air: dermal contact, inhalation and ingestion	Urine	Cr, Cd, Ni, Cu, Zn, Pb	[28]
Nigeria	E-waste workers	Air: dermal contact, inhalation and ingestion	Blood	Blood malondialdehyde, Catalase, Superoxide Dismutase and Glutathione Peroxide	[29]
Pakistan	Adult and children	Air and food: dust exposure, drinking water and food.	Toenail	Cr, Mn, Co, Ni, Cu, Zn, Cd, Pb.	[30]
Qatar	Immigrant Farm workers	Air, food intake: inhalation and ingestion	Toenail	As, Ba, Cd, Cu, Mn, Mo, Pb, Se,	[31]
United States	Welders	Air: inhalation	Toenail	Pb, Mn, Cd, Ni, As	[32]
China	E-Waste employees	Air: dermal contact, inhalation and ingestion	Blood	Pb, Cd, Cr, Ni	[33]
France	Welders	Air: dermal contact, inhalation and ingestion	Blood	DNA gene polymorphisms (GSTM1, GSTT1)	[34]
Italy	Cr plating workers	Air: dermal contact, inhalation and ingestion	Urine	Cr	[35]
Germany	Incinerator	Air: dermal contact, inhalation and ingestion	Urine	Cd, Ni	[36]