Hmm, I guess it doesn't seem too unreasonable that these rubber pellets are toxic in some way. They need to hook up with someone with a statistics background to determine whether these numbers are really significant.
Also, has anyone heard of FB players with issues? Goalies wear long sleeve shirts, but maybe they are breathing the stuff in at a much higher rate since they make saves on the ground. It's pretty crazy to see the clouds of pellets kicked up when a player slides, especially in slo mo.
Is it time for organic turf fill? Oh that is called grass. If there really is a link, what else can be used as the pellet material? I know there are a lot of grass purists out there, but there are a lot of places where turf really extends the season (Pacific NW included obviously). Schools and municipalities in these regions would still likely consider a less toxic version of turf for their recreational needs because it's just not as easy to have a nice grass turf like in the south.