This document summarizes regulations for biosolids from wastewater treatment under Title 40 of the Code of Federal Regulations (CFR) Part 503. Biosolids must meet pollution concentration limits for heavy metals, as well as pathogen and vector attraction reduction requirements. There are two pathogen reduction classifications - Class A requires eliminating measurable pathogens, while Class B significantly reduces pathogens. Various treatment processes can achieve Class A or B, such as composting or digestion. Vector attraction reduction aims to eliminate pathogens, destroy their food source, and prevent regrowth. Biosolids meeting all standards are considered Exceptional Quality.