Preserved eggs are also called preserved eggs. It is a traditional egg product of Han nationality. The taste is fresh, smooth and refreshing, and the color, fragrance and taste are all good. The main raw materials for making preserved eggs are quicklime, soda ash, salt, black tea and plant ash. Preserved eggs may have evolved from salted duck eggs recorded in the Northern Wei Dynasty. In the seventeenth year of Emperor Xiaozong of Ming Dynasty, namely 1504, the book Zhuyushan House Miscellaneous Department clearly recorded the origin of preserved eggs. Heavy metals such as lead or copper are often added to the dipping solution to solidify protein in the traditional preserved egg pickling process.

When processing preserved eggs, soda ash, lime, salt and lead powder are mixed in a certain proportion, and mud and bran are added to wrap the preserved eggs outside the duck eggs. Two weeks later, the delicious preserved eggs are ready. Yellow lead powder is lead oxide, which can make preserved eggs produce beautiful patterns, but with yellow lead powder, preserved eggs will be polluted by lead. According to national regulations, the lead content of preserved eggs should not exceed 3 mg per1000 g. Preserved eggs that meet this standard are also called lead-free preserved eggs. Therefore, lead-free preserved eggs do not mean lead-free, but the lead content is lower than the national standard.

Chinese medicine believes that children's body changes from yin to yang, and their metabolism is extremely strong. After being absorbed by children, trace lead in "lead-free" eggs will remain in tissues such as liver, lung, kidney, brain and red blood cells, and will also lead to the loss of calcium in bones and teeth. Regular consumption of so-called lead-free preserved eggs can lead to skeletal and dental dysplasia, anorexia and gastroenteritis in children. It will also affect intellectual development.

Lead-free preserved eggs only contain less lead than the specified standard, but they still contain lead. Although preserved eggs are delicious and nutritious, children are in a vigorous development stage and have obvious harmful reactions to lead. It's best to eat less or not.