If there is any group we should be most cautious about when it comes to the unknown long-term risks it's children because they have the longest term that they'll be stuck dealing with it. For a 60 or 70 year old when we talk "long-term effects" we're talking 10-20 years. When we're talking about potential long-term effects for a 10 year old it's an entire lifetime - 50, 60, 70, even 80 years of unknown physical and financial burden. I'm not a parent but it seems perfectly reasonable to me that parents would be very troubled by that kind of potential downside no matter how remote or unknown or unquantifiable the possibility.