Two issues, and really not meaning to trivialize your question in any way:

a) Chinese boiled corn is tasteless and really quite awful -- it's boiled for hours, and what little flavour it had died a long, long time ago.

b) In terms of 'food safety' in China, there are much bigger fish to fry. I can't relate whether there are some trace plastics residual on the corn, but I'm sure any visitor to China will have to deal with far worse, on a daily basis, such as re-used 'gutter oil', heavy metal toxicity, aflotoxin etc. Having said all that, we try not to worry too much, and eat away!

tb