Table 1.

Metal used in the industrial processes at the companies

Companies	Al	Cu	Cr	Ni	Pb	Zn
1	+	+	+	+	–	–
2	+	+	+	+	+	–
3	+	+	–	–	–	+
4	–	+	+	+	–	+
5	+	+	–	–	–	+

(+): Presence of the metal, (−): Absence of the metal