Within The Last Year, Four Boys In Our Soccer Club

Within the last year, four boys in our soccer club have had their appendix removed in the ER. All boys are 12 years of age and play at a very competitive level. Although I have found these cases to be most prevalent in this age group, it seems too strange to be a coincidence. All of them practice on artificial turf, with crumb rubber, about 3 times per week. I am concerned there is some environmental factor or some other common denominator that we should be evaluating. Is there any evidence that ingested crumb rubber or repetitive soccer related movements would contribute to the high volume of appendix related illness in our club?