How can you be sure? How can you get the information to know whether or not your children's toys, your medicines, your electic equipment, wall paint, food, and everything else you consume or use is safe?

You can't. So... abstain from everything? Make everything yourself - how will you have time with a job? Will you know the food you grow is safe and that your ground isn't polluted with things you can't test for at home? How about the equipment used to make that food - is the metal in that plow made of lead? Is the engine on the tractor safe?

Your due diligence is only possible because other people - usually with specialized education and/or experience - have made laws and standards to keep you safe. You don't have to personally check everything.

There are markings that certify that some things are safe according to some standards. You are not in a situation to know what actually is safe or to be able to test it (really, you are not; if you think you are, go talk to your nearest electrical engineer, chemist, or molecular biologist who will provide you several examples of the limitations of your knowledge and abilities). Therefore, trusting those certifications is important, and companies that falsify them must be punished so they stop doing so. It’s not complicated and that’s the whole point of the procedure (and the fine).