Food Safety Focus (84th Issue, July 2013) – Food Incident Highlight
Heavy Metals in Lime-preserved Eggs
Last month, the media reported that industrial copper sulphate, which might contain heavy metals as contaminants, was being used as an additive to speed up production of lime-preserved eggs (also known as "thousand-year eggs") in Mainland China. The incident has raised public concerns.
Copper is an essential micronutrient. In the Mainland, copper sulphate is a permitted processing aid that can be used to substitute lead oxide in the production of lime-preserved eggs in order to reduce the level of lead present in the final products. Excessive chronic exposure to lead can cause damages to kidneys and the central nervous system.