Chemical similarities lead to interesting phenomena. Arsenic is under phosphorus in the periodic table. Arsenates, then, are like to be found mixed with phosphates. So, adding phosphate to cleaning materials means that arsenic also is likely added.

The connection between phorphorus and arsenic is quite widely recognized.

Is is not surprising that gallium [local] is a byproduct of aluminum production, and germanium occurs in very small amounts in nearly all silicates.