The issues happen in the separation process. The mercury gold amalgam is burned in the fireplace. cyanide is used in the bleaching process. The old watchmaking trade journals have a lot of articles on this. The process is known as water gilding and it is really efficient. Back in the day the poorer folk would live upstairs. So the poor would suffer from the effects. It is said that to this day at the inversion level in the Swiss valleys there is a bathtub ring of mercury contamination. Who knows what the effects in the amazon rain forest are.
Some of the bi products of waterguilding are also neural toxins. Can kill instantly. The other use and why mercury is banned in most places in one of the byproducts is used for blasting caps and shell primers. (according to the trade journal.)