Chlorine Toxicity
Chlorine toxicity is the harm that too much chlorine does to living things like plants and seeds.
Think of it this way
Salt poured into a glass of water spreads through the whole glass. A small pinch makes the water a bit salty but still fine to drink. Too much salt fills every part of the water and makes it harmful. Chlorine works the same way in soil — a little is safe, but too much poisons the space around plant roots.
Explaining chlorine toxicity by grade level
Chlorine is found in pool water and tap water. A little bit is safe. But too much chlorine can hurt plants. If you soak seeds in strong chlorine water, they may not grow at all.