Wastewater can come from a variety of sources like homes, businesses, industries, runoff from roads, lawns and fields and is treated by municipal wastewater treatment facilities (Product, cornell). The solid material that remains after the treatment of wastewater is known as sludge (charac, cornell). Sludge can be employed in many different ways, it can be used as a soil additive or growing medium, sent to a composting facility, incinerated or landfilled (Char, cornell).

Biosolids are derived primarily from a combination of primary, secondary, and tertiary sewage sludges. Biosolids do not contain the coarse grit and screenings removed from raw wastewater during preliminary treatment steps or ash generated from incineration of sewage
When biosolids are applied to the land, pathogens that may be present in the biosolids can be deposited on plants, either directly from application operations or indirectly by vectors. Virus transport from soil to plants has been suggested as a possible route of exposure, but no definitive research has shown this to occur (Straub et al.1993). Planting restrictions are applied on biosolids-amended fields to ensure that contamination of plants is minimized until die-off of any residual pathogens have occurred and risks are reduced.

Potential bacterial and viral pathogens carried by animals that could be contracted by humans include tuberculosis, salmonella, lysteria, campylobacter, rotovirus, and toxoplasmosis. More than 50 animals can carry Cryptosporidium. Rats and mice in particular are vectors for serious illnesses—for example, rodents may drink treated wastewater containing Salmonella from a local waterway, and the Salmonella could be transferred to chickens that eat rodent droppings incidentally, which then transfer the pathogen to humans through eggs (Kinde et al. 1996).
Inanimate objects (such as crops, soil, equipment, and the shoes or clothing of workers) may be contaminated with infectious organisms that can be transported from sites of biosolids application. Restricting the harvesting of crops until natural die-off of remaining pathogens occurs, combined