Why should sewage sludge not be used as a soil builder or fertilizer supplement for crops if it has not been properly tested?

Using sewage sludge that has not been properly tested as a soil builder or fertilizer supplement for crops poses significant health risks, particularly because it may contain higher levels of toxic metals, which can accumulate in vegetation. When these metals are taken up by plants, they can then enter the food chain, affecting not only the crops themselves but also the animals and humans that consume them. This contamination can lead to various health issues, including bioaccumulation of toxic substances in the body, which can have serious long-term effects.

Proper testing of sewage sludge is essential to ensure it meets safety standards for agricultural use, particularly for crops intended for human consumption. Without such testing, there is no way to ascertain the levels of heavy metals or harmful pathogens, which could pose a risk to public health. Thus, avoiding the use of inadequately tested sewage sludge protects both the environment and the food supply from potential contaminants.