U.S. SEWAGE SLUDGE STANDARDS NEED
NEW SCIENTIFIC BASIS
U.S. Environmental Protection Agency's standards that
govern using treated sewage sludge on soil are based on
outdated science, says a new report from the National
Academies' National Research Council. The agency should
update its standards using improved methods for assessing
health risks, and should further study whether treated
sewage sludge causes health problems for workers who apply
it to land and for residents who live nearby, added the
committee that wrote the report. More rigorous enforcement
of the standards is needed as well.
a 1993 Clean Water Act rule, sewage sludge can be applied
to land if it is sufficiently treated to limit concentrations
of certain chemicals and reduce disease-causing pathogens.
Sewage sludge that meets these standards is referred to
as biosolids. Depending on the extent of treatment, biosolids
may be applied as a fertilizer where there is limited
public exposure to it, such as farms and forests, or on
sites with more public contact such as parks, golf courses,
lawns, and home gardens. Since 1992, when a ban on ocean
dumping was instituted, applying biosolids to land has
reduced the amount of sewage sludge that would otherwise
need to be buried in landfills or incinerated. About 5.6
million tons of sewage sludge are used or disposed of
each year in the United States, and 60 percent of that
is used for land application.
for assessing the health risks posed by exposure to chemicals
have evolved substantially since the 1993 biosolids rule
was established. In addition, EPA used an unreliable 1988
survey to identify hazardous chemicals in sewage sludge
when it set the standards, and other chemicals have since
been found to be of potential concern. A new survey and
revised risk assessments are needed, the committee said.
The revised risk assessments also should reflect the potential
for regional variations in climate, water flow, and biosolids
characteristics, and should be designed to protect individuals
against realistic maximum exposures.
report Biosolids Applied to Land: Advancing Standards
and Practices is available for sale at www.nap.edu/catalog/10426.html?onpi_newsdoc070202
and the press release announcing the report is available
(Source: River Info).