There is a new Canon Advisory on the new Canon T4i stating that a batch with a serial number containing a “1” for its sixth digit have been manufactured with too much zinc bis in their rubber grip. Not only will these rubber grips turn white, but they may cause an allergic reaction.
Here is what Canon has to say via Canon USA
The front rubber grips of some EOS REBEL T4i units produced in certain lots during the sixteen-day period between May 31st through June 15th, 2012 may turn white after a short period of time. We have determined after inquiry with the rubber manufacturer and analysis, that the substance zinc bis (N,N’-dimethyldithiocarbamate) is what causes the rubber surface to turn white.
Zinc bis is not used in the production of this product. However, the quantity of rubber accelerator used in the affected production lots was slightly higher than usual. As a result the rubber grips may turn white due to a chemical reaction with the rubber accelerator and other substances. High temperature and high humidity may contribute to this condition. Zinc bis (N,N’-dimethyldithiocarbamate), which becomes deposited on the rubber surface, is created as a result of this chemical reaction.
You can use the serial number to check whether your camera is affected by this phenomenon. If the sixth digit of the serial number is “1” please follow the procedure below. If the sixth digit of the serial number is “2” or higher, your camera is not affected.
Caution on Use
The amount of zinc bis (N,N’-dimethyldithiocarbamate) detected during our testing was minimal. While Canon has not received any reports of injury or allergic reactions, depending on one’s health and physical condition, in rare cases when this substance comes into contact with skin, allergic skin reactions* may develop. In addition, if eyes are rubbed after contact with the substance, symptoms, such as red eyes, may develop.
As a precautionary measure, thoroughly wash your hands with water if they have come in contact with the rubber grips that have turned white. (If any medical symptoms develop, please consult your physician immediately.)
*Please note that the occurrence of allergic skin reactions depend on the target substance, length of contact with the target substance, one’s
health and physical conditions, and sensitivity of one’s skin structure, and not everyone will be affected by allergic symptoms.
Preparations are underway to provide free repair service for affected cameras by replacement of the rubber grips. Once this repair service is available (ETA of mid July 2012), we will post an update on our web site and also notify registered users via email. Please register your EOS Rebel T4i, so that we can inform you via email when the free repair service will commence.
This information is for residents of the United States and Puerto Rico only. If you do not reside in the USA or Puerto Rico, please contact the Canon Customer Support Center in your region.
Be sure to read more about it on Canon USA.