Form my experience RoHS contaminants (such as lead) do not creep into processes randomly. These materials are either part of the manufacturing process or they are impurities in raw materials. ABS manufacture and non-lead based paints don't normally have these types of materials as contaminants. Sabotage could theoretically happen, but other than that I really could not see this being process where toxic materials could be introduced in a significant quantity. I have been involved in manufacturing in Asia, Europe and the US over the last 22 years in both design and quality assurance. China is major market for my process chemicals, and I have been in sites ranging from solar to HDD to MEMS to plastics. I have never seen a process excursion that could allow toxic material to be introduced at a significant level occur randomly (again, sabotage is a real possibility, but that can happen with any product in any country; just ask Tesla).