This depends on how deep the hole is dug, for the out house. If it's dug too deep then the contents may seep into the water level and end up in a near by lake.
no
contamination of groundwater
yes
Hiv
cough
yes
Yes, galvanized steel can leach zinc into the soil, which may pose a risk to the environment depending on the concentration and exposure levels.
Yes, mercury can evaporate at high temperatures and pose a risk to human health if inhaled or absorbed through the skin.
Vitamins A and D
Yes
The practice known as universal precautions makes the assumption that those bodily fluids pose a risk for transmission of HIV.
possibly because of the chemicals