|Dr. David Lewis, et.al.
University of Georgia
Columns::October 7, 2002
An ill wind
Researchers link human illness to sludge fertilizer
By Kim Carlyle
Burning eyes, burning lungs, skin rashes and other symptoms of illness
have been found in a study of residents living near land fertilized with
Class B biosolids, a byproduct of the human-waste treatment process.
The study, the first reporting this link to be published in a medical journal,
was co-authored by David Lewis, a UGA research microbiologist also
affiliated with the U.S. Environmental Protection Agency’s National Exposure
Research Laboratory; David Gattie, assistant professor of agricultural
engineering in UGA’s College of Agriculture and Environmental Sciences;
Marc Novak, a research technician with UGA’s School of Marine Sciences;
Susan Sanchez, assistant professor of veterinary medicine at UGA; and
Charles Pumphrey, a physician from Prime Care of Sun City in Menifee,
Calif. The research was published earlier this year in the British medical
journal BMC Public Health.
Researchers found that affected residents lived within approximately one kilometer (0.6 miles) of land-
application sites and that they generally complained of irritation after exposure to winds blowing from treated
fields. Staphylococcus aureus infections, which commonly accompany diaper rash, were found in the skin and
respiratory tracts of some individuals. Approximately 25 percent of the individuals surveyed were infected, and
The 54 individuals surveyed lived near 10 land-application sites in Alabama, California, Florida, New Hampshire,
Ohio, Ontario, Pennsylvania and Texas. S. aureus is commonly found in the lower human colon and tends to
invade irritated or inflamed tissue.
“The EPA did not consider S. aureus to be a significant public health risk even though it is a leading cause of
hospital-acquired infections and is commonly found in sewage,” says Lewis. “When approving sludge for use as
a fertilizer, EPA looked at chemical and pathogen risks separately, without considering that certain chemicals
could increase the risk of infection.”
Chemicals such as lime, which is added during sludge processing, can irritate the
skin and respiratory tract and make people more susceptible to infection, according
to Lewis. Another article by Lewis and Gattie dealing with pathogen risks from sludge
was recently published in the American Chemical Society journal Environmental
Science and Technology.
Approximately 60 percent of an estimated 5.6 million tons of dry sludge is used or
disposed of annually in the United States. Though modern treatment can eliminate
more than 95 percent of the pathogens, enough remain in the concentrated Class B
sludge that leaves treatment plants to pose a health risk, according to Lewis and Gattie.
In an independent report released almost simultaneously with the Lewis and Gattie article, the National
Research Council of the National Academy of Sciences concluded that there may be public health risks from
using processed sewage sludge as a commercial fertilizer.
The NAS report, “Biosolids Applied to Land: Advancing Standards and Practices,”
cites growing allegations that exposure to Class B sludge, the most common form,
is causing illnesses and sporadic deaths among residents. The report concludes
that certain types of exposure, such as inhalation of sludge particles, “were not
adequately evaluated” previously and no work has been done on risks from mixtures
of pathogens and chemicals found in sludge. In 1989, an EPA study found 25
groups of pathogens in sludge, including bacteria such as E. coli and salmonella;
viruses, including hepatitis A; intestinal worms; harmful protozoa; and fungus.
Sludge also includes traces of household chemicals poured down drains, detergents
from washing machines, heavy metals from industry, synthetic hormones from birth
control pills, pesticides, and dioxins, a group of compounds that have been linked to cancer.
Fertilization of land with processed sewage sludge, or “biosolids,” has become common practice in western
Europe, the United States and Canada. Local governments, however, are increasingly restricting or banning the
practice as residents have reported adverse health effects.
“Most people are not aware this is going on in the United States,” says Gattie. “Most people don’t realize that a
concentrated sludge of waste products is being processed into a cheap commercial fertilizer and applied to
fields near our homes. ‘Biosolids’ does not connote ‘sewage’ to most people.” Gattie notes this practice became
more common after ocean dumping of sewage was prohibited.
A High-Level Disinfection Standard for Land-Applied Sewage Sludges (Biosolids)
David K. Gattie1 and David L. Lewis 2
1Department of Biological and Agricultural Engineering, and 2Department of Marine Sciences, University of
Georgia, Athens, Georgia, USA
Complaints associated with land-applied sewage sludges primarily involve irritation of the skin,
mucous membranes, and the respiratory tract accompanied by opportunistic infections. Volatile
emissions and organic dusts appear to be the main source of irritation. Occasionally, chronic gastrointestinal
problems are reported by affected residents who have private wells. To prevent acute
health effects, we recommend that the current system of classifying sludges based on indicator
pathogen levels (Class A and Class B) be replaced with a single high-level disinfection standard and
that methods used to treat sludges be improved to reduce levels of irritant chemicals, especially
endotoxins. A national opinion survey of individuals impacted by or concerned about the safety of
land-application practices indicated that most did not consider the practice inherently unsafe but
that they lacked confidence in research supported by federal and state agencies. Key words:
biosolids, sewage sludge. Environ Health Perspect 112:126-131 (2004). doi:10.1289/ehp.6207
available via http://dx.doi.org/ [Online 17 November 2003]
Interactions of pathogens and irritant chemicals in land-applied sewage sludges
David L Lewis1 ,2 , David K Gattie3 , Marc E Novak2 , Susan Sanchez4 and Charles Pumphrey5
1US Environmental Protection Agency, National Exposure Research Laboratory, Athens, GA, USA
2Departments of Marine Sciences University of Georgia, Athens, GA, USA
3Biological & Agricultural Engineering University of Georgia, Athens, GA, USA
4Medical Microbiology University of Georgia, Athens, GA, USA
5Prime Care of Sun City, Menifee, CA
BMC Public Health 2002, 2:11 doi:10.1186/1471-2458-2-11
Affected residents lived within approximately 1 km of land application sites and generally complained of irritation
(e.g., skin rashes and burning of the eyes, throat, and lungs) after exposure to winds blowing from treated
fields. A prevalence of Staphylococcus aureus infections of the skin and respiratory tract was found.
Approximately 1 in 4 of 54 individuals were infected, including 2 mortalities (septicaemia, pneumonia). This
result was consistent with the prevalence of S. aureus infections accompanying diaper rashes in which the
organism, which is commonly found in the lower human colon, tends to invade irritated or inflamed tissue.
EPA SLUDGE MAGIC AT EPA