Tritium has a half life of about 12.33 years, which means it looses half its energy every 12.33 years via beta decay (-e). Beta has more energy than alpha (which is heavier and can be stopped by a sheet of paper), thus tritium could penetrated deeper below the skin (although it is stopped by a few centimeters of wood). Unless both the glass dial and the glass receptacle on the markers break there should not be a need to worry. However you may wish to read more on the matter to appease your concern.