Complex sentence: Thus, the lethal dose for a 68 kg (150 pound) person would be about 136 micrograms, or roughly equivalent to the weight of a couple of grains of ordinary (fine) table salt (NaCl).
Split into simpler sentences: Thus, the lethal dose for a 68 kg (150 pound) person would be about 136 micrograms. That is roughly equivalent to the weight of a couple of grains of ordinary (fine) table salt (NaCl).