Police said the explosion was caused by a box of firecrackers left in the bin in Jiaokou, between Foshan and Guangzhou.
The blast occurred at about noon yesterday on the corner of Fangxing Road and Fangcun Road West.
Police investigating the case said they did not think the explosion was intentional.
Mainland cities are on a high state of alert after a series of violent attacks that the authorities have blamed on Muslim separatists from Xinjiang .
Six people were injured after a knifeman attacked people at a Guangzhou railway station last month. One suspect was arrested, although a source close to police said at the time that three others had fled the scene.
Police said yesterday's explosion happened when the sanitation worker walked past the bin. She sustained injuries to both hands and was taken to hospital, where her condition was stable.
Authorities cordoned off the area around the bus terminal after the explosion and carried out a search. Police found two abandoned suitcases, but no other fireworks or explosives.
Another cleaner told the Guangzhou Daily she was metres from the scene of the blast. "The explosion was very loud, so I walked over to take a look," the cleaner said. "[The sanitation worker's] face was covered in blood, as were her hands."
The cleaner said the injured worker, who was in her 50s, could not open her eyes after the blast.
One witness said the explosion caused limited damage to the bin and surrounding area.