Treating a city's water supply to remove any bacteria and impurities as clean and hygenic water supplies benefits the public/society.
True, some stretching exercises can be harmful, even if performed correctly.
There are many stretching exercises that can cause you problems. The most sensitive spots on your body are your neck, your back, and your knees. The most common stretching technique is to bend over and touch your toes (even doctors will tell you to do this at times). Doing that will cause tension in your lower back which may be bad going forward.
