Genesis once bubbled...
There IS evidence that bone necrosis can be caused by DCS-related insults to the circulation in the bones. But does the average diver suffer DCS? Is there a sub-clinical level of injury that is happening to virtually everyone, or even some statistically significant portion of the diving population? There is no SCIENTIFIC evidence that there is.
Is Scuba unique? Only in the fact that it is equipment-intensive. Is it particularly "deadly"? No. Not even compared to swimming in your backyard pool - five times as many school-age children die every year in swimming pools as all persons who die diving annually!
Risk assessment is a good thing, and it is also part and parcel of being a parent. I applaud those who consider - carefully - such factors. But the hype and harpie crowd, IMHO, has no seat at this table.
But people who use statistics in a misleading way are welcome?
Using total number of accidents instead of accident rate is a favorite way of twisting statistics to overstate or understate a point. Compare the accident rate of scuba with the accident rate of swimming, and you'll find swimming is a safer sport.
As for scuba being unique, you're convieniently omitting the pressure thing. True, the exposure is for much less time than that experienced by commercial divers, but we're talking about children who are still growing. As you correctly point out, there are no scientific studies correlating bone necrosis or other physiological trauma in children to exposure to a hyperbaric environment. But the lack of data only means that we don't know, not that exposure to a hyperbaric environment causes no harm. While some people think it's OK to take the attitude of "ask forgiveness, not permission" in gray areas such as this, I think that's a somewhat unethical attitude to take when it applies to letting 8-10 year olds dive.
Finally, with regards to sub-clinical DCS, I guess it depends on your definition of sub-clinical. Technically, any DCS that causes tissue damage cannot be sub-clinical, since the damage itself is a symptom of bubble formation. The question is to what extent are divers either unaware of the damage, or do they ignore the damage or attribute the effects of the damage to something other than DCS. Regardless of the definition, bubble formation causes a host of insults to the human body (refer to chapter 10.4 of Bennett and Elliott's Physiology and Medicine of Diving), so it's incorrect to say there is no scientific evidence supporting damage caused by sub-clinical DCS.
Alan