United States
Environmental Protection
\r ^1 # ^Agency
Office of Water
EPA 822-F-18-002
May 2018
2013 and 2015 Biosolids Biennial Reviews
Summary
Biosolids are nutrient-rich organic materials that are
the product of treated domestic sewage sludge from
a wastewater treatment facility. The Clean Water
Act (CWA) requires EPA to review federal biosolids
(sewage sludge) standards every two years to
identify additional toxic pollutants that occur in
biosolids and set regulations for those pollutants if
sufficient scientific evidence shows they may harm
human health or the environment. To meet this
requirement, EPA has published online the 2013 and
2015 Biosolids Biennial Reviews. Based on the
results of the reviews, EPA has not identified
additional toxic pollutants in biosolids for regulation.
Background
In 1993, EPA promulgated Standards for the Use or
Disposal of Sewage Sludge (found in Code of Federal
Regulations (CFR) Title 40 Part 503), which resulted
in numeric standards for 10 metals and operational
standards for microbial organisms.
Additionally, the CWA requires EPA to review
existing sewage sludge standards at least every two
years (i.e., biennial review). The purpose of such
reviews is to identify additional toxic pollutants, and
promulgate regulations, if needed, for those
pollutants consistent with the requirements set forth
in the CWA.
In fulfilling the commitment for completing Biennial
Reviews 2005-2015, EPA searched publicly available
published literature to capture available information
on occurrence, fate and transport, and human
health or ecological effects for pollutants that may
occur in U.S. biosolids to assess the availability and
sufficiency of the data for conducting risk
assessments.
To inform the risk assessments of pollutants in
biosolids, EPA typically uses models that require the
following information:
1)	Human health and ecological toxicity values
(e.g., studies that are adequate for evaluating
hazards following acute or chronic exposure);
2)	Adequate data on pollutant concentrations in
U.S. biosolids based on a suitable analytical
methodology for detecting and quantifying
pollutant concentrations (data are
considered adequate when sufficient details
are provided regarding sampling, handling,
and analysis); and
3)	Fate and transport data for these pollutants.
The Agency assesses whether data for
pollutants are sufficient to conduct human
health and ecological risk assessments, and
revisits previously identified pollutants when
literature searches of bibliographic databases
reveal newer data.
Results of the 2013 and 2015 Reviews
The Agency searched the literature from August
2011 through December 2015, comprising the 2013
and 2015 Biennial Reviews.
2013
For the 2013 Biennial Review, 77 new articles were
identified as providing relevant information for
pollutants that may occur in U.S. biosolids. Review of
these articles identified 35 new chemicals and six
new microbial pollutants in biosolids. Thirteen of the
newly identified chemicals are perfluoroalkyl
substances (PFAS). No new human health toxicity
data were identified in either the 35 new chemicals
or for chemicals identified in previous biennial

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reviews. However, EPA is currently aware of new
information for PFAS and assessment of these
chemicals is ongoing. Ecological toxicity values were
found for one chemical (triclosan) identified in a
previous biennial review. New physical-chemical
properties (log Kow and half-life) were identified for
22 chemicals; 18 new chemicals identified in the
2013 Biennial Review and four chemicals previously
identified in biosolids. New bioaccumulation factors
were identified for 5 previously identified chemicals.
2015
For the 2015 Biennial Review, 46 new articles were
identified as providing relevant information for
pollutants that may occur in U.S. biosolids. Review of
these articles identified 29 new chemicals in
biosolids. Human health toxicity values were found
for eight new chemicals (2,3,5-trichlorophenol and
seven nitrosamines) and one chemical
(carbamazepine) identified in a previous biennial
review. Ecological toxicity values were found for one
chemical newly identified in biosolids
(decamethylcyclopentasiloxane), but not for other
chemicals previously found in biosolids. New
physical-chemical properties were identified for 11
chemicals, and new bioaccumulation factors for
aquatic organisms were identified for one chemical.
Conclusions
The available data for many of the chemicals and
microbial pollutants identified are not sufficient at
this time to evaluate risk using current biosolids
modeling tools. EPA will continue to evaluate
available toxicological information for PFAS
identified in 2013. The EPA's Office of Pesticide
Programs plans to complete a draft risk assessment
for triclosan in late 2018. The Federal Drug
Administration and EPA have been closely
collaborating on scientific and regulatory issues
related to triclosan to ensure government-wide
consistency in the regulation of this chemical.
At this time, EPA has not identified any additional
toxic pollutants for potential regulation during the
2013 and 2015 biennial review process. The Agency
will continue to assess the availability of sufficient
information for these and other pollutants identified
during the biennial review activities pursuant to
Clean Water Act section 405(d)(2)(C).
Where can I find more information?
To view the biennial review summaries and get more
information about EPA's Biosolids Program, visit
EPA's Biosolids website at: https://epa.gov/biosolids.
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