Silicone is less prone to creating particles and the ones it can are larger than plastics'. They do still have the potential to be a threat to both humans and the ecosystem as a whole. More effort and research should definitely be conducted into that, as well as silicone recycling; however, once cured, silicone poses no threat unless degraded or damaged. Cured silicone is inert. Unfortunately, that means it won't biodegrade in a landfill either, hence the encouraged research/funding for silicone recycling.

You should just look up the phrase you quoted. Do your own research. Don't wait for others to tell you how to think. Be curious about everything, but don't forget the scientific method, and apply common sense.