As the saying goes, "pig iron is rotten, take it home and wait for death." What does this mean?

This proverb is unknown to many people now, but it was a household name in ancient times, and everyone knew it. Now in our home, some rubbish will be sold and won't stay at home. Sometimes people who buy scrap iron will go door to door, buy waste products and materials, and everything. What are old household appliances, old mobile phones and old plastics? Buy old things as long as they can be sold.

It wasn't like this in ancient times. There wasn't so much scrap iron. Even if there are buried in graves, there are buried objects that have already rotted and deteriorated, or iron, lead, copper, swords and spears used by ancient warriors, which are accidentally dug up and kept at home as treasures, or played with every day, inadvertently causing some bacteria and heavy metals to enter the human body, causing various strange diseases and eventually dying. Ancient people didn't have scientific knowledge and thought it was unlucky and possessed by ghosts, so it would be unlucky to advise people never to take those rubbish home. This is scientific.

It is rare to see scrap metal now. Modern people seldom hear this sentence. If there is anything unwanted at home, someone will buy it and no one will throw it away. They don't stay at home and touch every day. However, some people are exposed to some waste products because of ignorance, and they are infected with leukemia or other incurable diseases. Therefore, we should pay special attention not to dismantle waste materials casually. In particular, some electronic and electrical products contain some heavy metal radiation, and there is basically no cure for infected people, especially curious children. We must look after them and keep them away from those waste materials and scrap iron to protect our health.

So this sentence still applies today, explain it to the children more.