United States
                  Environmental Protection
                  Agency
Office of Health and
Environmental Assessment
Washington DC 20460
                  Research and Development
EPA/600/S6-88/010 Dec. 1988
&EPA         Project  Summary
                  Qualitative Pathogen  Risk
                  Assessment for Ocean  Disposal
                  of Municipal  Sludge
                   This  document focuses  on
                  microbial contaminants of municipal
                  wastewater sludges that have been
                  actually or potentially implicated in
                  producing  human  illness; it
                  summarizes available  data on the
                  occurrence, transport and fate of
                  these  pathogens in  the  marine
                  environment;  and describes the
                  possible  hazards  to human health
                  associated with  the  disposal of
                  sludges  In open ocean  waters.
                  Following  the presentation of
                  background information, a  dis-
                  cussion  of risks  associated  with
                  ocean disposal  of sludge are
                  presented. The scope of the risk
                  assessment Is restricted, therefore,
                  to pathogens present in municipal
                  sludge discharged at the open ocean
                  dump sites.
                   Because of a limited number of
                  studies on the pollution of marine
                  environments by sludge disposal, it
                  is difficult to assess these risks. It is
                  known that pathogens can persist in
                  sediments for an extended period of
                  time and that animals (for example,
                  rock crabs) dwelling at a dump site
                  can  pick up  these organisms and
                  move away from the site. It is also
                  known  that  sludge-impacted
                  sediments can  drift  long distances
                  from point of discharge.  Whether
                  these  sediments (and their
                  associated pathogens) can reach
                  coastal environments does not seem
                  likely under normal conditions, but in
                  the event of storms and quakes it is a
 distinct possibility. It is logical  to
 assume that this pollution is  less
 likely to happen when a sludge  is
 disposed at the 106-mile site than at
 the New York Bight or  Philadelphia
 dump sites, because of the distances
 involved.
  Predictions on viral and bacterial
 decay following  ocean  disposal  of
 sludge will require information on the
 vertical and horizontal movement  of
 discharged sludge as well as on the
 survival  of pathogens attached  to
 sludge  particles. The  latter
 information is not currently available.
 Studies  on how far  aerosols  can
 travel and  how long pathogens can
 survive in them are also incomplete.
 Obviously,  consumption  of  seafood
 (from in and around a dump site) is
 riskier  to  health  than  swimming
 because of the bioconcentration  of
 pathogens  by filter feeders.
  This Project Summary was devel-
 oped by EPA's Environmental Criteria
 and Assessment Office,  Cincinnati,
 OH, to announce key findings of the
 research  project that is  fully
 documented in a separate report  of
 the same  title (see Project Report
 ordering information at back).
 Introduction
  Ocean  disposal of domestic sewage
 and sludge has been carried out off the
 coast of the United States since the New
 York Bight  site opened in 1924.
 Discharge of waste at sites  such as the

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New York  Bight (to be closed in  1988),
the Philadelphia  dump  site (closed in
1980), the  Puerto Rico Trench dump site
(closed) and the 106-mile deep  water
ocean waste disposal  site in  the mid-
Atlantic  Bight (which  opened  in  March
1986 on a five-year interim basis) has
generally  been accomplished   from
barges.  The amount of sludge dumped
into the ocean by U.S. municipalities and
industries in the 1970s was estimated to
be 5x106 wet metric tons/year.
  Human  exposure  to  pathogenic
microorganisms  from  ocean-disposed
sludge  may occur  through  primary
contact recreation such  as  bathing,
scuba and skin diving,  water skiing, and
during  occupational  activities such  as
commercial  and  military diving
operations. In addition, ingestion of raw
or partially  cooked seafood  that has
become contaminated  may be harmful.
Bivalve  mollusks such as  oysters  and
clams are  of particular concern because
they feed  by filtering  particulate matter,
including microbes contained  in  large
volumes  of seawater.  Inhalation  of
contaminated dust  or  aerosol  droplets
containing  pathogens  from sewage is
also a potential exposure route.


Sludge Characteristics and
Disposal Methods
   Ocean   disposal  of  sludge  is
accomplished by construction of offshore
sewage outfalls or by barging  the waste
several miles offshore and discharging it
at a designated dump  site.  Because
offshore outfalls  have been   shown to
release  high concentrations of bacteria
and  viruses into marine  waters, the
principal method of ocean disposal is to
dump sludge into a barge, tow the barge
to a disposal site, open disk valves fixed
in the  bottom  of specially constructed
holding tanks in the hull of the  barge.and
allow  the  sludge to drift away. Sludge
may be dumped from a moving  barge
(line dump, which results in the greatest
dispersal)  or from a  stationary  barge
(spot dump).
   The New York Bight dump site  began
receiving municipal sludge in  1924 and
will cease  operations in 1988. The site is
a coastal ocean area at the apex of New
Jersey and Long Island situated roughly
12 miles (19.2 km) equidistant from the
shores of  New York and new  Jersey at
the entrance to the Hudson Canyon. The
sludge dumping area occupies 100 km2
at  latitude 40 25'04"N  and  longitude
73°44'53"W. Depth at the dump  site is
 ~30 m, and bottom temperature  ranges
from 9.8-12.3°C  in the summer.  During
1965-1970, the average annual input  of
sludge to  the  New York Bight  was
3.2x109 kg.
   Fecal  coliforms  have been isolated
from New York  Bight bottom sediments
in concentrations as high as 2.3x104/100
m€, and coliform bacteria have also been
found in crabs, lobsters and scallops that
inhabit the area. Acanthamoeba protozoa
and  human  enteroviruses  such  as
coxsackie  B3  and  B5  (<108/kg  of
sediment) and echo 1 and 7 (<182/kg)
have  been identified in  surface water,
sediment and crabs collected from this
dump site.  However,  no evidence exists
that sewage sludge disposal at the New
York Bight  dump site increases the risk
of  swimming-associated disease at any
New Jersey,  New York  City  or  Long
Island  beaches.  Moreover,  Clostridium
perfringens spore densities in the water
column or bottom sediments indicate that
dumped sludge does not reach the shore
in  significant  quantities  anywhere along
the Bight.
   The  Philadelphia  sewage sludge
dump  site  is a  172-km2  area located
-70  km east of Ocean  City, MD,  at
roughly 23°23'N  and 74°15'W. The site,
which  lies  over the continental shelf  in
waters 40-60  m  deep,  received sludge
from Philadelphia, PA, and Camden, NJ,
from  1973 until  its closing  in  1980.
Between  1973 and 1977,  2.8x109 kg  of
sludge was deposited there.
   Changes in the benthic environment in
the vicinity  of  the Philadelphia site during
and  after  its  operation  have  included
accumulation  of metals  and other toxics
in organisms and sediment, alterations in
community structure, changes  in abun-
dance of various species, increased rates
of  mortality of the ocean quahog (Mica
islandica) and the appearance of sludge
beds,  sewage bacteria  (total  coliforms,
fecal  coliforms  and fecal  streptococci),
pathogenic protozoa (Acanthamoeba),
human enteroviruses (coxsackie B3 and
B5, echo  1  and 9  and  polio 2)  and
diseases in crabs.
   The 106-mile  deep water site off the
New Jersey coast was used primarily for
disposal of  >5x106  metric tons  of
chemical wastes from 1961-1978. Only
~4x105  metric  tons of   sludge  were
dumped  at the 106-mile  site before
1978,  but  in  1984 EPA designated the
area  as  a permissible  sewage sludge
disposal  site on  a five-year  interim
basis.  Furthermore, as  of March  1986
permittees  using  nearshore sites  may
dispose of wastes at the  106-mile  site.
It is expected that ~ 7x106 metric tons of
New York/New Jersey sewage currently
being  dumped  at  the   12-mile
site will be  discharged  at the 106-mi
site.
   The Puerto Rico Trench  dump  si
was  used primarily for  pharmaceutic
wastes and is now closed for dumping.

Pathogens of Concern
   Processed  sewage  wastes  mi
contain residual  pathogens,  such  <
viruses, bacteria, cysts of protozoa ar
ova  of  helminths.  However,  mo
outbreaks of  sewage-related disea:
have been attributed to  the  use of rs
sewage, raw sludge or night soil on fo(
crops  consumed   raw,   and  I
contamination of  drinking water  fro
septic  tanks or by  consumption of rz
shellfish from  sewage-polluted water
The principal pathogens found in sewa<
can be divided into four groups: bacteri
protozoa, helminths and viruses. Sewat
treatment practices reduce the number
the four groups of pathogens, but there
evidence to  indicate that  effluents  ar
sludges contain detectable amounts. Tl
amounts  and  variety  of  pathogei
present in sewage  vary from communi
to community  and are dependent  up<
urbanization, season, population densil
ratio of children to adults and  the sanita
habits of the  community.

Exposure  Pathways
   Potential pathways of enteric pathog<
transport in  the marine environment a
illustrated in  Figure 1.
   Field studies at the New York  Big
and Philadelphia dump sites have shov
that fecal indicator bacteria  and  vii
pathogens occur in surface  waters ai
accumulate  in sediments. Crabs in tl
vicinity of these sludge  disposal  sit
have  been  shown to contain  humi
enteroviruses.  Such contamination  m;
occur through intake of sediment mater
during feeding  and  by  ingestion
infected fish and  shellfish. Shellfish a
filter feeders and  tend  to accumula
bacteria  and  viruses at  much  high
concentrations than  the surroundii
water.  It is possible that pathogens m
be passed through several species in t
marine food  chain.
   Contact with pathogens  may  al
result from bathing or diving  in pollut
marine waters. Although  ocean  dur
sites are located offshore, currents,  wir
storms and dredging activity can result
resuspension   and  transport
contaminated  sediments  to  nearshc
locations that may pose a potential risk
human health.
   Aerosols generated during disposal)
sludge and  by wave action or dredgi

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Sea water
 Dredging
                     Aerosols
Ocean Disposed
    Sludge
                    Sediments
                                         Seawater
                                        Crabs and Other
                                           Crustacea^
                                               1i
                                                           Polycheate Worms
                                                                 1
                                                                Fish
Figure 1.    Potential pathways of enteric pathogen transport in the marine environment.
activity  may transport bacteria and
viruses as far as 160 km from the ocean
by winds.


Persistence of Pathogens in
the Marine Environment
   The survival of fecal indicator bacteria
and viruses in marine waters has
received a great deal  of attention.
Numerous studies have been conducted
on the factors controlling the survival of
specific bacteria  pathogens, protozoa
and helminths.
   Sunlight  and temperature appear to
be  the  dominant  factors  controlling
survival  of  coliform  bacteria in  marine
waters,but  salinity also plays  a role.
Temperature  is critical  to viral survival,
and  sunlight  may be  important but its
influence has not been studied exten-
sively. Persistence of these pathogens in
sediments and in mollusks appears to be
prolonged; however, no previous studies
have been  conducted on  survival  of
sludge-associated  microorganisms in
the marine environment. Field studies at
the Philadelphia dump site suggest that
sludge accumulated in sediments may
greatly prolong  or cause the growth of
fecal indicator bacteria.
   Bacterial and viral survival in water
follows an exponential curve, so that the
probability of a bacterium  dying in  a
given time interval is  independent of its
age.  Time  for 90%  inactivation  of
coliform bacteria is  considerably faster
for seawater  (0.6-8  hours)  than for
freshwater (20-115 hours).  Inactivation
                     time decreases  sharply with  increasing
                     temperature.  In  warm climates  with
                     sewage temperatures  of  25-30"C,
                      >99%  reduction in indicator bacteria
                     concentration  may  be  expected  in  10-
                     15 days.
                        Enteric viruses have been reported to
                     survive  from  2-130  days  in seawater in
                     laboratory  studies.  Time  for 90%
                     inactivation has  been  estimated to be
                     between 15 and 70 hours.
                        Survival of amoeba  cysts in water is
                     primarily dependent upon temperature.
                     At 25QC,  Entamoeba histolytica  may
                     survive  for 7-20 days; survival time at
                     5°C  may  be  >1 month.  Sewage
                     treatment  may  remove  52-93%  of
                     Giardia cysts.
                        Laboratory  experiments   have
                     determined that 97% of Ascaris eggs are
                     killed after two days in seawater. Ascaris
                     eggs are  considerably hardier than
                     Trichuris, hookworm or Entrobius eggs,
                     but somewhat less resistant than Taenia
                     eggs. Hookworm eggs can survive in
                     sludge  at 27°C for <43  days,  but in
                     seawater their  survival  is  <5 hours
                     compared  to >30  hours  for Ascaris
                     eggs. Helminth  eggs tend  to settle in
                     seawater and accumulate  in  bottom
                     sediments.
                        In  estuary water  >80%  of fecal
                     indicator bacteria are directly  associated
                     with suspended  sediments, and  this
                     association  appears to  prolong their
                     survival in  the  aquatic  environment.
                     Several recent field  studies indicate that,
                     on a  volume basis, greater numbers of
                     coliforms and bacterial  pathogens occur
in  bottom sediments than in overlying
water.  Coliform  bacteria  have  been
detected  in areas of sludge  disposal at
both the Philadelphia and New York Bight
dump sites; at the Philadelphia location,
the microbes survived s 4 years after the
last sludge was dumped.  Fecal indicator
bacteria with  multiple  drug  resistance
were found 30 months after cessation of
sludge dumping.
   Field studies  have documented  the
occurrence  of  enteroviruses  and
rotaviruses in marine  sediments, and
laboratory studies  have  demonstrated
that virus adsorption  to   sediments
prolongs  survival time in  marine waters.
Enteroviruses  were  isolated  from
sediments taken from  the Philadelphia
sewage sludge dump  site  17  months
after dumping  stopped,  but tests  for
viruses were negative 24 and 36 months
after the site's closure.

Infective Dose for
Microorganisms
   Estimation  of minimum  infectious
doses  (MIDs) for various pathogens in
polluted  marine  water,   food  and
sediments  is  difficult  because  of
uncertainties in the immune status  of
host, assay technique, sensitivity of host,
virulence of pathogen, use of upper 95%
confidence limit,  route  of  exposure,
choice  of dose-response model, syn-
ergism/antagonism, dietary consider-
ations and distribution of subjects among
doses and number  used. In  addition,  it
should  be realized that infection does not
necessarily mean disease.

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   In many studies, small  numbers of
viruses (as few as 1 or 2 tissue culture
plaque-forming units),  primarily vaccine
strains, have produced  infection in
human subjects.  The  infective  dose of
protozoan cysts such as Giardia lamblia
and  Entamoeba  by  the oral  route
appears to be as low as between 1  and
10 cysts. Essentially one helminth  egg
can  be considered to be infectious,
although  symptoms may  be  dose
related.
   MIDs for bacteria are generally higher
than those for viruses and parasites.  The
number of ingested bacteria required to
cause  illness appears to range from
102-108,  although   recent  studies
suggest that the  infective  dose  for
Salmonella may be  <10 organisms.
Virulence of the particular type and strain
of microorganism and  host factors may
play roles  in determining the actual
number of microbes  required to  cause
infection.
         Qualitative Risk Assessment
           Because  of  a limited  number of
         studies  on  the pollution  of marine
         environments  by sludge disposal, it is
         difficult to  assess the risks.  It is  known
         that pathogens can persist in sediments
         for an extended period of time and that
         animals (for example,  rock  crabs)
         dwelling at a dump  site can  pick  up
         these  organisms and move away from
         the  site. It is also  known that sludge-
         impacted  sediments can  drift  long
         distances from  the point of discharge.
         Whether  these sediments  and  their
         associated pathogens can reach coastal
         environments does not seem likely under
         normal conditions, but in the event of
         storms and  quakes  it  is a distinct
         possibility. It  is logical  to assume that
         this pollution  is less likely to happen
         when  sludge  is disposed at  the 106-
         mile site than at the New York Bight or
         Philadelphia dump sites because  of the
         distances involved.
   Predictions on  viral and bacteria
decay following ocean disposal of sludgi
will require information on  the  vertica
and horizontal movement of discharge!
sludge as well as  on the  survival  o
pathogens attached  to  sludge particles
The  latter information  is not currently
available. Studies on  how far  aerosol:
can travel and how  long pathogens cai
survive  in them  are also  incomplete
Consumption  of seafood from  in am
around a dump site  is riskier to healtl
than  swimming  because   of  the
bioconcentration  of  pathogens  by filte
feeders.
   In  summary,  with  what  little
information is  available, it is only  possible
to speculate on the occurrence of humar
health risks from pathogens  in municipa
sludge  disposed in the ocean.  More
research is needed in order to develop «
definitive risk assessment methodology.
    This Project Summary was prepared by staff of the Environmental Criteria and
     Assessment Office, Cincinnati, OH 45268.
    Larry Fradkin is the EPA Project Officer (see below).
    The Complete report entitled "Qualitative Pathogen Risk Assessment for Ocean
     Disposal of Municipal Sludge,"  (Order No. PB 89-126 593/AS; Cost: $21.95,
     subject to change) will be available only from:
             National Technical Information Service
             5285 Port Royal Road
             Springfield, VA 22161
             Telephone: 703-487-4650
    The EPA Project Officer can be contacted at:
             Environmental Criteria and Assessment Office
             U.S. Environmental Protection Agency
             Cincinnati, OH 45268
 United States
 Environmental Protection
 Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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