Studies suggest that arsenic, chromium, copper, nickel and zinc are unlikely to cause problems for plant, animal, or human health, primarily because they are not found in high concentrations in MSW compost and/or are not readily taken up by plants.
Arsenic-- Arsenic, while toxic to animals and humans, is not readily taken up by plants and thus, is unlikely to pose a problem.
Chromium -- Chromium occurs only in trace amounts in MSW composts. In addition, most of the chromium in MSW composts occurs in a form not readily taken up by plants.
Copper -- Long-term field studies show very little increase in the copper content of crops even with substantial additions of MSW compost. The organic material in the compost binds the copper and reduces its availability to plants.
Nickel -- Nickel concentrations are generally low in MSW composts. Thus nickel, although toxic to plants, is unlikely to decrease plant growth when compost is applied.
Zinc -- Although applications of sewage sludge have caused toxicity to plants due to zinc, MSW composts contain much lower concentrations of zinc than does sludge. Zinc in MSW compost is unlikely to injure crops and may, in fact, be beneficial in regions deficient in zinc.