I would ask him whether he is really sure that $20,000 less is worth putting his health at risk. Many people are not aware of the risks that are involved in being in contact with toxic waste. But, in general, anything that is considered "toxic" will have a negative effect on the health of organisms. Moreover, this negative impact can sometimes be difficult to see until many years have passed. Therefore, I would tell him that I do not think that $20,000 is worth risking his future health.