An E170 flight crew on final approach was informed by a Flight Attendant of a strong burning plastic odor. Emergency equipment was called and CFR investigated the aircraft after a safe landing and taxi to its gate.

Narrative

We were passing through 6;000' on approach when we got a chime from the flight attendants who reported that there was a strong smell of plastic burning in the cabin; with the strongest presence of it in the back of the cabin. Apparently it began passing through 10;000 feet. There was no smoke in the cabin and there was no apparent cause of the odor. We were already joining the final approach; and were number two for the runway; not expecting delays. As a precaution; I contacted the Approach Controller and informed him of the situation. I did not declare an emergency; but I did request emergency equipment to be standing by in case the condition deteriorated. I don't know whether ATC declared an emergency for us.After landing the First Officer contacted the flight attendants to get a progress report. They informed us that the smell went away; and that there was a popped circuit breaker in the aft galley -- the inboard coffee maker; which was deferred. At no point was the smell strongly present in the flight deck. I smelled a hint of it during the approach; but the First Officer could not detect it. We passed the update on to ATC and; followed by the emergency equipment; we continued to the gate. Upon arriving at the gate; we asked the passengers to remain seated while I investigated the cabin. I observed no smells or apparent sources; and with the consent of the Fire Marshal we deplaned. The Fire Marshal then conducted a further inspection of the cabin and found nothing.There were some clues as to what may have caused the smell; though there was no obvious explanation. First; there was the coffee maker circuit breaker. However; that coffee maker was deferred; and was not used; and; according to Maintenance Control; the circuit breaker may have been pulled by Maintenance; but not collared. The Flight Attendant did not observe it pop; nor did she remember if it was popped prior to flight. Second; passing through about 20;000 feet; we had a Bleed 2 Fail message; which we were able to clear by running the QRH procedure. If there was an issue that affected the bleed; which primarily feeds Pack 2; it might explain why the smell was mostly present in the cabin. Finally; something that occurred to me at writing of this report; this airplane had a history of the cabin gasper fan circuit breaker tripping in the prior weeks; and was deferred for a time. If I recall correctly; it was causing a smell in the cabin. I passed this information to Maintenance as soon as it occurred to me. I believe continuing a steady approach into our destination airport was the best course of action; though perhaps we should have considered donning oxygen masks. My emphasis was on getting the aircraft on the ground safely.