This program is mandated by Section 5 of the Toxics Substances Control Act (TSCA). The New Chemicals Program functions as a gatekeeper which can identify conditions-up to and including a ban on production-to be placed on the use of a new chemical before it is entered into commerce.
Currently, the newest version is MS Word 2010. Same with all the other different MS applications (PowerPoint, Excel, etc.)
Although you can open Word 2016 and 2013 .docx or .docm files in earlier versions of Word, you might not be able to change some items that were created by using the new or enhanced features in Word 2016 or 2013.