In short, there is no environmental difference between a device labeled TMPxxx-G4, LMxxx-G4, HDCxxxx-G4 or any of those devices having a -E4 as the suffix instead.
Historically, G4 and E4 suffixes meant that the devices were rated to be "Green" or "Lead Free." However, as time has passed, all devices have been pushed to these new "Green" or "Lead Free" standards, but the part numbers have remained available so that customers have had a consistent orderable part number.
To check on the "Green" status of a part, you can put your part number into the search at the following link:
For definitions of E4 and G4 suffixes, please refer to the following links: