Is sodium metabisulfite harmful?

Sodium metabisulfite is quite common in our daily life. It is a kind of food additive. We often see preservatives or fresh-keeping agents in the food we buy. These contain sodium metabisulfite, but we rarely open them. Sodium metabisulfite has many functions. It can be used as a preservative and bleaching agent in our daily life. When used as a preservative, it can keep the food fresh. When used as a bleaching agent, it can bleach items. So it is harmless to our human body to use them appropriately, but it is harmful if we eat them. Let's analyze it below:

Generally speaking, sodium metabisulfite will decompose into sulfur dioxide in the air. This compound residue will strongly irritate the human respiratory tract and gastric mucosa, causing coughing and asthma. Moreover, sodium metabisulfite is easily soluble in water and produces sulfurous acid, an acidic substance that can corrode the intestines. In addition, because sodium metabisulfite is artificially synthesized, its purity cannot reach 100%, and there will be some heavy metal residues, such as lead, chromium, etc. Long-term consumption may cause excessive heavy metal content.

When sodium metabisulfite is used as a bleaching agent, it is limited to fumigation and cannot be used for bleaching by direct contact with objects such as soaking. Sodium metabisulfite can cause damage to the liver and kidneys in the human body. In severe cases, it can cause acute poisoning and even death. In daily life, buyers can make simple judgments based on the color, smell, etc. of food. When buying water chestnuts, you can check whether the color of the skin is too bright. If so, you can smell whether it has a pungent smell (if it is a fruit, you can peel off the skin and smell it). If it has a pungent smell, it may have been soaked in chemicals. When used as a bleaching agent for bamboo shoots, bean curd sticks, biscuits, vermicelli and noodles, the maximum usage of sodium metabisulfite is calculated based on the residual sulfur dioxide content. The limit for vermicelli and noodles is 0.1 grams of residual sulfur dioxide per kilogram.

Sodium metabisulfite is not generally considered to be directly carcinogenic. However, long-term consumption will affect our body and immune function and may induce cancer.