W4170 research committee

By Trung Le, Northwest Biosolids Research Committee and Brown & Caldwell

On November 15, 2018, the Environmental Protection Agency (EPA)’s Office of Inspector General (OIG) released a divisive report titled “EPA Unable to Assess the Impact of Hundreds of Unregulated Pollutants in Land-Applied Biosolids on Human Health and the Environment”. This report assessed that the EPA lacked the data and risk assessment tools to appropriately determine the safety of 352 pollutants found in biosolids. Those of which, 61 pollutants are designated as acutely hazardous, hazardous, or a priority pollutant under other federal environmental laws or programs. The 2018 OIG report claimed that an additional 291 “unlisted” pollutants were not addressed by the EPA.

Since the release of the OIG report, a wave of scientific rebuttals from various regional and national research communities as well as EPA agencies have pushed back on those claims. The latest of these rebuttals was issued by the United States Department of Agriculture (USDA)’s W4170 Multi-State Research Committee, a consortium of research universities, agencies, and industry experts with over 45-years of biosolids research history. This same committee and its predecessors largely produced the research that facilitated the EPA’s biosolids management regulations codified under 40 CFR Part 503. The W4170 authors include heavyweights such as Nicholas Basta, PhD (Ohio State University); Ian Pepper, PhD (University of Arizona); Linda S. Lee, PhD (Purdue University); and Greg Kester (California Association of Sanitation Agencies). This committee has long garnered support for their works by organizations such as NACWA, WEF, CASA, NEBRA, etc.

oig response

The W4170 rebuttal examines the 2018 OIG report criticisms of hazardous and “unlisted” pollutants broadly in the categories of antibiotics/antimicrobials, pathogens, pharmaceuticals and personal care products, pesticides, metals, dioxins, and brominated flame retardants. The main conclusions backed by extensive scientific review state that the 2018 OIG report did not focus on concentrations where many sources of human exposure far exceed that of the presence in biosolids. Many of these pollutants in biosolids are typically below soil background levels or well below risk-based levels. Aligning with EPA’s Office of Water characterization the 2018 OIG report as “alarmist and biased”, the W4170 rebuttal concludes that the statements made by the OIG are inaccurate. However, the W4170 rebuttal did acknowledge that several chemicals listed by the 2018 OIG report will require further study. Although the W4170 rebuttal is a lengthy 50 pages, it provides a concise yet comprehensive response to the concerns of the 2018 OIG Report and is worth a peruse though. 


  • The original 2018 OIG Report can be found here.
  • The W4170 OIG rebuttal can be found here.
  • Updated WEF information on biosolids can be here.
  • Information on WEF’s current priority with COVID-19 can be found here
  • Research Short Story - Allegations Against Land Application: Facts and Myths (includes links to related BioFest 2019 presentations) can be found here.