I frequently make dashi using dashi sachets (love the Yamaki brand; looks like tea bags) and dried kombu. This makes a delicious dashi broth with many uses. But are there any known health hazards? Particularly, I wonder about: (1) The smoke flavors in the dashi sachets -- are these smoke flavors, whether from real smoked bonito or some manufactured flavor, carcinogenic? And (2), I recently saw at the store that a Shirakiku brand pack of dried kombu had one of those stickers, "this product contains chemicals known to the state of California to cause cancer." I'd appreciate any insights.