Since it can sterilize, it will naturally have certain toxicity. If a small amount of chlorine bleach is swallowed, it will irritate the esophagus, mouth and throat and cause vomiting. But the residual chlorine in tap water is far from that dose. At present, the International Center for Research on Cancer lists chlorine as the "third category" in the "classification of carcinogens", that is, "there is not enough information to determine whether the substance is a human carcinogen".
Animal experiments and human experiments with water directly treated with chlorine show high safety. For example, in a human trial published in 1982, no adverse reactions were observed at a dose of 0.34 mg/kg body weight. This dose is the highest dose used in the experiment, so it is not clear how high the dose will cause adverse reactions. However, it is much higher than the chlorine that people may take in their diet.
The World Health Organization's standard for residual chlorine in tap water is based on animal experiments. In animal experiments, the "undetectable adverse reaction dose" is per kilogram of body weight15mg per day. With a safety factor of 100, the "daily tolerance" of human body is 0.15mg per kilogram of body weight per day. Assuming that all this chlorine comes from drinking water, the allowable content of tap water is 5 mg per liter.
Usually, the residual chlorine content in tap water is below per liter 1 mg, which is far lower than the standard of 5 mg per liter by the World Health Organization. Chlorine has a pungent smell. When the chlorine content in water exceeds 2 mg per liter, most people can smell it. As for other forms of chlorine in water, most people's "taste threshold" is also lower than 5 mg per liter, and sensitive people can even taste chlorine with a chlorine content of 0.3 mg per liter.
In other words, as long as you don't smell or taste chlorine in the water-an unpleasant pungent smell, you don't have to worry about the problem of residual chlorine. Even if there is a little residual chlorine in it, it will be mainly decomposed into chloride ion, chlorate and oxygen during cooking. The former two will not evaporate, and the latter will not affect health. It is a bit alarmist to worry that chlorine is "smeared on food".