One major problem with studies such as these, IMO, is that the foods aren't categorized for source. Milk in Connecticut may have very different foreign ingredients then in my state of Missouri, and etc.
There is also the new GMO fears and they are poorly addressed, again IMO. GMO's are most often labeled as unnatural and there fore possibly harmful, but this isn't the true threat. GMO's are more often then not modified to be chemical resistant as a way to improve crop production. The fact that they can withstand herbicides for instance means they are more heavily treated with them and therefor have a better chance of transferring them into a diet.
The bottom line is we may be ingesting chemicals that would normally harm us because new modified plants can no longer act as the mine canary.