They can enter your blood stream (via breathing/ingesting) and once in your bloodstream they can enter cells and mutate your dna, which can cause cancer/birth defects/ reproductive harm
The effect differs. It could produce a different amino acid in the sequence because the corresponding codon has changed. It could also prevent the production of the originally intended sequence by changing one of the amino acids of a "start" codon (aka AUG) or extend the protein's sequence by modifying a "stop" codon (UAA, UAG, UGA or UGG), producing a new protein that might be useless or have different effects on the cell.
Not sure what the following is, but I think it could be less carbon in the soil
