EPA OFFICE OF RESEARCH AND DEVELOPMENT EPA/625/R/92/013 Revised July 2003
Control of Pathogens and Vector Attractions
Pathogen Equivalency Committee, included:
Robert Bastian, Bob Brobst, Mark Meckes, James E. Smith Jr., Joseph Farrell (a consultant) Reviewed by John Walker
1.2 This regulation ----was issued under the authority of the CWA as amended in 1977, and the 1976 RCRA . For most
sewage sludge, the new regulation replaces part 257.
Chapter 2 Sewage Sludge Pathogens
As mentioned in Chapter 1, one concern is the potential effect of some human pathogens on animals. Enteric viruses
can cross species lines, and animal life, particularly warm blooded animals, can be affected if they are exposed to some
of the pathogens found in sewage sludge.
[Documents show neither] Domestic animals [or humans] are protected by site restrictions which limit grazing on
sludge amended land [or harvesting food crops, especially since grass can not be harvested for 1 year]
How could [human] exposure to these pathogens occur?
- If improperly treated sewage sludge was illegally applied to land or placed on a surface disposal site, humans and
animals could be exposed to pathogens directly by coming into contact with the sewage sludge, or indirectly by
consuming drinking water or food contaminated by sewage sludge pathogens. Insects, birds, rodents, and even
farm workers could contribute to these exposure routes by transporting sewage sludge and sewage sludge
pathogens away from the site. Potential routes of exposure include:
- . Touching the sewage sludge.
- . Walking through an area - such as a field, forest, or reclamation area - shortly after sewage sludge application.
- . Handling soil from fields where sewage sludge has been applied.
- Inhaling microbes that become airborne (via aerosols, dust, etc.) during sewage sludge spreading or by strong
winds, plowing, or cultivating the soil after application.
- Consumption of pathogen-contaminated crops grown on sewage sludge-amended soil or of other food products
that have been contaminated by contact with these crops or field workers, etc.
- Consumption of pathogen-contaminated milk or other food products from animals contaminated by grazing in
pastures or fed crops grown on sewage sludge-amended fields.
- Ingestion of drinking water or recreational waters contaminated by runoff from nearby land application sites or by
organisms from sewage sludge migrating into ground-water aquifers.
- Consumption of inadequately cooked or uncooked pathogen-contaminated fish from water contaminated by
runoff from a nearby sewage sludge application site.
- Contact with sewage sludge or pathogens transported away from the land application or surface disposal site by
rodents, insects, or other vectors, including grazing animals or pets.
- Handling soil from fields where sewage sludge has been applied
- Handling soil or food from home gardens where sewage sludge has been applied
- Inhaling dust**
- Walking through fields where sewage sludge has been applied*
- Consumption of crops from fields on which sewage sludge has been applied
- Consumption of milk or animal products from animals grazed on fields where sewage sludge has been
- Ingestion of water contaminated by runoff from fields where sewage sludge has been applied
- Ingestion of inadequately cooked fish from water contaminated by runoff from fields where sewage sludge has
- Contact with vectors which have been in contact with sewage sludge [flies, dogs, cats, cattle, horses, etc.]
- workers exposed to Class B biosolids might benefit from several additional precautions. For example, dust masks
should be worn for the spreading of dry materials, and workers should wash their hands carefully after working
with sewage sludge or biosolids.
Other recommended practices for workers handling biosolids or sewage sludge include:
- Wash hands before eating, drinking, smoking or using the restroom.
- Use gloves when touching biosolids or sewage sludge or surfaces exposed to biosolids or sewage sludge.
- Remove excess sewage sludge or biosolids from shoes prior to entering an enclosed vehicle.
- Keep wounds covered with clean, dry bandages.
- If contact with biosolids or sewage sludge occurs, wash contact area thoroughly with soap and water.
What is a bioaerosol?
- Bioaerosols are airborne water droplets containing microorganisms. These may include pathogenic
microorganisms. Bioaerosols are a potential public health concern with regard to Class B biosolids because if
pathogens are contained in the biosolids, they may become airborne and infect workers or the public through
direct inhalation or through contact after settling on clothing or tools. It has been found that aerosolization of
protozoa and helminths is unlikely, but bacteria or bacterial components (endotoxin) and viruses may become
airborne and disperse from an application source depending on local meteorological and topographical conditions.
- Pathogens may become airborne via the spray of liquid biosolids from a splash plate or high-pressure hose, or in
fine particulate dissemination as dewatered biosolids are applied or incorporated. While high-pressure spray
applications may result in some aerosolization of pathogens, this type of equipment is generally used on large,
remote sites such as forests, where the impact on the public is minimal.
What is Aspergillus fumigatus? A. fumigatus is not covered in the Part 503.
- In general, it has been found that concentrations of [airborne] A. fumigatus drop to background
levels within 500-1000 feet of site activity.
- Aspergillus fumigatus is a pathogenic fungus which is found in decaying organic matter such as
sewage sludge, leaves, or wood. Because the fungus is heat resistant, and because sewage sludge
composting facilities often use wood chips as a bulking agent, A, fumigatus has been associated with
composting. Inhalation of A fumigatus spores may result in allergenic effects including irritation of the
mucous membranes and asthma. However, A, fumigatus is a secondary, or opportunistic pathogen,
and infection from A. fumigatus ("Aspergillosis") is limited to debilitated or immune-compromised
§ 503.9 General definitions.
(j) Feed crops are crops produced
primarily for consumption by animals.
(k) Fiber crops are crops such as flax and
(l) Food crops are crops consumed by
humans. These include, but are not
limited to, fruits, vegetables, and tobacco.
§ 503.32(b)(5) Site restrictions.
(iv) Food crops, feed crops, and fiber
crops shall not be harvested for 30 days
after application of sewage sludge.
(v) Animals shall not be grazed on the
land for 30 days after application of
(vi) Turf grown on land where sewage
sludge is applied shall not be harvested
for one year after application of the
sewage sludge when the harvested turf is
placed on either land with a high potential
for public exposure or a lawn, unless
otherwise specified by the permitting