However, like other trace elements, boron is more likely to be deficient in soils than to cause toxicity. Most boron in MSW compost is water soluble and sufficient leaching of the compost prior to application may eliminate the problem of toxicity. In addition, greenhouse experiments have found that the addition of mineral fertilizers will decrease the uptake of boron by plants. Thus, fertilization could also be used to reduce toxicity to plants. Elements of Concern for Animal and Human Health Cadmium, lead, and mercury can be harmful to animals and humans at relatively low concentrations and thus, should receive close scrutiny in relation to the application of MSW composts to agricultural soil.
Tobacco is of particular concern.
When tobacco is burned and inhaled, much more of the cadmium is taken up by the human body than would be if eaten. For this reason, MSW composts containing more cadmium than is found in average soils should probably not be applied to land on which tobacco is grown. Based on the limited data available, MSW composts should also probably be avoided in mushroom cultivation. In addition, uptake of cadmium by spinach and other leafy crops should be investigated further, since they are known to accumulate cadmium. Studies have shown that MSW compost applications may result in crop tissue concentrations that exceed this value.