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From: "Edo McGowan" <edo_mcgowan@hotmail.com>
To: Assemblymember.nava@assembly.ca.gov, Assemblymember.benoit@assembly.ca.gov, Assemblymember.
Evans@assembly.ca.gov, Assemblymember.keene@assembly.ca.gov, assemblymember.niello@assembly.ca.gov,
Assemblymember.Ruskin@assembly.ca.gov
CC: Assemblymember.Huffman@assembly.ca.gov, Assemblymember.dymally@assembly.ca.gov, Assemblymember.
hancock@assembly.ca.gov
Subject: Sewage and public health---risk of disease transmission and food-borne disease
Date: Mon, 11 Dec 2006 03:13:06 +0000
To: Assembly Joint Committee on Emergency Services, etc.
To: Assembly Committee on Environmental Safety and Toxic Materials
To: Assembly Committee on Health
To: Assembly Committee on Natural Resources
Fm: Dr Edo McGowan
Re: 1:> Sewage effluent and the outbreak of food borne illness
2:> Sewage plants and aerosols of pathogens
I WOULD LIKE A DIRECT AND OPEN DISCUSSION ON THE TWO ISSUES NOTED BELOW WITH COMMITTEE STAFF.
THIS EMAIL AND ITS CONTENTS IMPACT ALL OF THE ABOVE COMMITTEES AND LISTED MEMBERS.
When talking of preparedness, security, natural resources, health, and environmental safety, the ability to thwart the
transmission of disease and pollution is critical. There are non-pharmacological approaches to disease transmission
that warrant additional consideration. During an epidemic, the sewer plant is recipient of the human waste that contains
high loads of pathogens, antibiotics and disinfectants. Viruses like SARS and bird flu are examples of fecally transmitted
airborne pathogens that are easily spread by sewage and sewer aerosols. The ability of currently designed and
operated sewer works to effectively deal with these issues is quite limited. The ability of currently licensed sewer plant
operators to understand these implications is also limited and there is no testing or requirement within state regulations
to require sewer plant operators to understand these issues. Thus sewer plants represent a hereto under appreciated
mechanism for the spread of disease.
Sewage and the relationship to food-borne illness
The health hazards associated with pathogens in sewage effluent have been well reported in the peer reviewed
literature. Dozens of known enteric pathogens may be present in the treated wastewater. Sewer plants are not designed
to properly treat incoming toxins, pharmaceuticals, or pathogens. In fact, sewer plants offer a medium for the mixing of
pathogens that might otherwise seldom come together. Antibiotic resistance amongst incoming pathogens is rapidly
advanced by genetic exchange and mixing with toxins and pharmaceuticals in sewer plants. The sewer plant augments
this sharing of genetic material conferring resistance and virulence. Emerging infectious diseases are increasing, and at
least one new enteric pathogen has been discovered every year over the past decade. Current wastewater standards
do not consider these newly emerging pathogens. Thus irrigation of salad crops with treated wastewater constitutes an
ongoing risk such as now done in the Salinas Valley. Title-22 of the State of California and Part 503 of the federal
regulations are failing to protect public health. Until these deficiencies are corrected, we will see continuing spread of
food-borne illness and a crippling of California’s agriculture.
Several newer scientific and medical papers in peer reviewed journals discuss these issues. But existing and now badly
antiquated standards continue in their failure to recognize this. The recent papers by CA kinney of the USGS
demonstrate that both antibiotic resistant pathogens and levels of pharmaceuticals that are able to maintain resistance
are found in discharged wastewater. Kummerer out of Germany has been writing extensively about this for several years
now. Kate Brown out of New Mexico also reiterates this. Amy Pruden out of Colorado notes that free DNA is abundant in
wastewater and its re-uptake will confer antibiotic resistance. Higgins and Murthy out of Water Environment Research
Foundation write on the failure of standard lab tests to note viable but non-culturable (VBNC). Thus these all point to the
fact that the standards now fail to adequately protect the population. Thus if there is use of wastewater for irrigation or
infiltration of wastewater into areas where ag wells can pull this water and thus irrigate, the issue is one that can no
longer be ignored or see regulators throwing up their hands saying the system is complying with standards. We can
always exceed bad standards at the state level.
Of the issues that your committees might review, the failure of standards might be high on the list. Additionally, EPA has
steadfastly refused to look at antibiotic resistance, although there are recent indications that it has finally initiated such a
review. Those familiar with EPA feel, however, that this review will be cooked and that it will be set up to skew data in
favor of continued neglect and promotion of the current failing standards. In a Feb 2005 FOIA request, yet to be
adequately answered, my group asked how EPA was coming on its investigation of antibiotic resistance. The results are
noted below and demonstrate that as of the beginning of this year little progress had been made---this in spite of the
NAS/NRC report of 2002 directing EPA to undertake such a study.
Unfortunately, the principal agency responsible for this area (US-EPA) has included no pathogen risk assessment within
the controlling regulations. Standards set for health have been set for a mere pittance of toxins that are found in
wastewater. Additionally, pathogens are assumed to be controlled by technology based standards, but not through
actual health risk assessments. This concept of technology based controls has been turned on its ear by the recent
Higgins & Murthy paper although others had for a considerable time remarked on this issue without result. Marker or
indicator organisms employed in these tests are of limited usefulness, especially when considering the rapid emergence
of new pathogens, transfer of genetic information conferring virulence, and antibiotic resistance and VBNC states. The
lack of or limited usefulness of contained data within and upon which the regulations are set is pointed out within the
NAS/NRC 2002 report on land applied sewage sludge. Much of these data also apply to released effluent and thus
irrigation with reclaimed sewer wastewater. In essence, the 2002 NAS/NRC report indicated that the data were old and
had fallen considerably behind the advancement of pathogens. In addition, the NAS/NRC, in that report, commented on
the lack of data on off-site movement as well as antibiotic resistance. Consequently compliance with these regulations
does not assure protection of public health.
This then brings into question the current paradigm on infection and its dose response to a certain load of a particular
pathogen, i.e., ID and LD 50s. Lateral transfer of mobile genetic elements conferring resistance is not considered in this
old paradigm. With the prodigious capacity for the gut bacteria to multiply, once the lateral transfer has taken place,
very small original numbers---well below the old paradigms can be multiplied into impressive numbers. Since viruses and
phages are also involved, their capacity to multiply, which dwarfs that of bacteria, must also be included. Thus there is a
need for a new paradigm; unfortunately, the regulatory community seems not to recognize this. When one considers the
multiplication within sewer plants and also within their byproducts, disbursement into the environment, the transfer to
background organisms, hence to man and his animals, then the remultiplication within commensals of the gut, the
emerging picture is worrisome.
Thus the use of the old paradigm such as ID-50 without considering the impact of the above is essentially a meaningless
exercise that grossly under represents reality. The issue of food borne disease is now a hot topic. The residuals or
adverse sequelae and morbidity of some of these pathogens are well demonstrated and frankly frightening. Once
ingested, the plasmids may be transferred to normal flora, and subsequently to pathogenic bacteria found in humans or
animals, making later treatment with particular antibiotics ineffective. Also one must consider transfer of genetic
information from these organisms to more robust organisms as highlighted by Sjolund et al. (2005) [1] indicating that
resistance in the normal flora, which may last up to four-years, might contribute to increased resistance in higher-grade
pathogens through interspecies transfer.
These authors go on to note that since populations of the normal biota are large, this affords the chance for multiple
and different resistant variants to develop. This thus enhances the risk for spread to populations of pathogens.
Furthermore, there is crossed resistance. For example, vancomycin resistance may be maintained by using macrolides
[2].
Walsh (2003) [3] notes that resistance to antibiotics is not a matter of IF but one of WHEN. In the case below, the pre-op
patients were free of colonization with resistant bacteria. But what would be the result if there had been inadvertent
acquisition of resistance from environmental contamination such as through sewage effluent used for irrigation?
Schentag, et al. (2003), in Walsh, followed surgical patients with the subsequent results. Pre-op nasal cultures found
Staphylococcus aureus 100% antibiotic susceptible. Pre-op prophylactic antibiotics were administered. Following
surgery, cephalosporin was administered. Ninety percent of the patients went home at post-op day 2 without infectious
complications. Nasal bacteria counts on these patients had dropped from 105 to 103, [what unit?] but were now a mix of
sensitive, borderline, and resistant Staphylococcus sp. By comparison, prior to surgery, all of the patients’
Staphylococcus samples had been susceptible to antibiotics. For the patients remaining in the hospital and who were
switched on post-op day 5 to a second generation cephalosporin (ceftazidine), showed bacterial counts up 1000-fold
when assayed on post-op day 7 and most of these were methicillin resistant Staphylococcus aureus (MRSA). These
patients were switched to a 2-week course of vancomycin. Cultures from those remaining in the hospital on day 21,
revealed vancomycin resistant enterococcus (VRE) and candida. Vancomycin resistant enterococci infections can
produce mortality rates of between 42 and 81%.
The EPA has never done a health risk assessment on pathogens. It has, however, relied on a number of mathematical
models and these all have serious flaws. Accordingly I feel that whatever conclusions have been drawn from, for
example, Gale’s paper on microbial risk assessment, upon which EPA relies, would understate the risks as the decay
curves would be confounded by the above. Further, at least in the U.S. the constant reapplication of sewage sludge or
irrigation with reclaimed or infiltrated effluent, especially the common practice when speaking of land applied biosolids
that greatly exceed agronomic needs---i.e., sludge dumping and not true agriculture---would vastly corrupt the estimates
made by Gale. This concern is shared by CA Kinney of the USGS. Additionally, these materials are not easily confined
to the areas where ther are applied as the Sugar Creek study [4] amply demonstrates. The Sugar Creek study is thus
applicable to release of "treated" sewer wastewater into local drainages.
Thus, in the case of Gale's work upon which EPA has relied, there is in essence no risk assessment, merely an elegant
argument that may appeal to the unenlightened and that tends to promote the concept that sewage plants actually work
to protect the public health.
The tragic issue here is that pathogens do not respond to what is politically correct or to technically expedient quick fixes.
2. Sewer plants, aerosols, and the transmission of disease
In discussing non-pharmacologic approaches to infection control, please consider the following. There is a need to look
at alternatives to current sewer plant technology. As currently designed, sewer plants are major generators of aerosols.
These plants receive vast numbers of pathogens and thus during times of an epidemic, the human waste is collected,
mixed and then discharged into the environment.
Thus, the average sewer treatment plant represents an increased, but unnecessary risk to both human and
environmental health. These increased risks accrue to the discharge of partially treated effluent, the application of
heavily contaminated sludge to land and generation of aerosols, all with an accompanying release of pathogens
Below are some abstracts for your consideration and attached is a draft policy paper. From these one might be able to
estimate distances of aerosol drift for a bacterium, or virus, such as influenza (see table below). Many of the spherical
bacteria are about 1 micrometer (uM) in diameter, which is about a hundred times the size of the virus that causes
poliomyelitis.
The November issue of the CDC’s journal Emerging Infectious Disease discusses aerosol drift of and transmission of
Influenza A virus---see below.
Of the three modes of transmission for these viruses---aerosols have not been adequately discussed. Nonetheless,
there is now reasonably strong evidence that aerosol transmission is a critical component of an expanding epidemic and
thus its evolution into a pandemic. To the extent that sewer plants would augment this, I feel that this is an unstudied but
potentially significant flaw in overall infection control and preparedness.
In the recent past, opinion held that large-droplet transmission was the predominant mode of transmission. As a
consequence and the short fallout distances experienced by large-droplets, distant transmissions were often not
included in risk analyses. For example, Tellier notes that the Canadian Pandemic Influenza Plan and the US DHHS
Pandemic Plan did not consider aerosols, merely large-droplet transmission. Nonetheless, these positions fail to
recognize knowledge collected over the recent past showing that aerosols are critical. As Tellier indicates, the relevant
chapters of many more current reference books refer to aerosol transmission.
In dong work as a grad student at Davis we demonstrated tissue damage from drifting propanil at 50 miles from its
release point. Later as a post-doc, I did fellowship research work in hospital settings and as first assist on surgical teams
using CO2 lasers for removal of Papillomavirus. Through this work I was able to demonstrate that standardized
protective devices for virus aerosols were inadequate and that these were not only unsafe but gave a false sense of
security.
By definition, an aerosol is able to remain in suspension for prolonged periods because of its low settling velocity. For
spherical particles of unit density the settling time for a 3-M fall is noted in the table below. From this, considering the
size of both bacteria and viruses, it will be noted that aerosol movement is potentially considerable.
TABLE
Assumptions: 5 mpg average wind speed, laminar flow. The assumptions would be upset within an urban setting with
buildings, up-currents, and turbulence from traffic. Adapted from Tellier.
Particle Diameter………………..Settling Time………..Distance at wind speed 5 mph
100 uM……………………………….10 sec…………………..44 ft
20 uM…………………………………4 minutes……………….1780 feet
10 uM………………………………….17 minutes……………..7480 feet (1.4 miles)
5 uM……………………………………62 minutes……………approx 5 miles
< 3uM………………………………….These essentially will not settle.
The median diameters at which particles exhibit aerosol behavior also corresponds to the size range that will reach the
deepest recesses of the respiratory tract.
While keeping in mind the material below in the abstracts discussing drift from sewer plants and then the idea of drift
distance for a bacterium or smaller particle, the issue of sewer plant aerosol generation is worrisome. Since sewer works
also provide the opportunity for numerous organisms to be brought into close proximity with each-other, there is ample
and well documented opportunity for genetic exchange. Thus sewer plants, as currently designed and operated, are
generators of disease and not, as myth would lead one to believe, providing treatment that reduces disease.
+++++++++++++++++++++++++
Review of Aerosol Transmission of Influenza A Virus
Raymond Tellier*† commentcomment
*Hospital for Sick Children, Toronto, Ontario, Canada; and †University of Toronto, Toronto, Ontario, Canada
Suggested citation for this article
Abstract
In theory, influenza viruses can be transmitted through aerosols, large droplets, or direct contact with secretions (or
fomites). These 3 modes are not mutually exclusive. Published findings that support the occurrence of aerosol
transmission were reviewed to assess the importance of this mode of transmission. Published evidence indicates that
aerosol transmission of influenza can be an important mode of transmission, which has obvious implications for
pandemic influenza planning and in particular for recommendations about the use of N95 respirators as part of personal
protective equipment.
++++++++++++++++++++++++
Comparative investigation of airborne culturable microorganisms in sewage treatment plants.
Haas DU,
Reinthaler FF,
Wust G,
Posch J,
Ruckenbauer G,
Marth E.
The present study investigated emissions and emmissions of airborne microorganisms (mesophilic bacteria, Escherichia
coli, molds, Aspergillus fumigatus, thermophilic actinomycetes/bacilli) in sewage treatment plants. For the aerobiological
investigations three sewage treatment facilities with an activated-sludge process, capacities between 2000 and 28,000
PE and different cleaning steps were selected. The measurements of microorganism emission were conducted in the
area of the intake (screen), in the area of biological treatment (activated sludge tank) and at a distance of 10 m from the
activated sludge tanks. In order to determine the emmission, additional measurements were conducted leeward of the
plant at a distance of 200 m. Samples were taken using four parallel six-stage Andersen 1 AFCM volumetric samplers. In
the area of the intake counts for bacteria were 7.4 x 10(2) CFU/m3 (median), for thermophilic actinomycetes 1.8 x 10(1)
CFU/m3, for thermophilic bacilli 7.1 x 10(1) CFU/m3, for molds 2.4 x 10(3) CFU/m3 and for Aspergillus fumigatus 1.8 x 10
(1) CFU/m3. Only isolated airborne coliform recoveries, i.e. E. coli, were detected. In the area of the activated sludge
tank, in the adjoining area (10 m) and in the vicinity of the plants (200 m), the counts for all microorganism groups
investigated corresponded to natural conditions. The results show that the counts of culturable aerogenic
microorganisms in and in the immediate surrounding of the sewage plants investigated are low. Although the possibility
of an infection through inhalation cannot be ruled out, the direct contact with sewage is much more critical.
PMID: 12096685 [PubMed - indexed for MEDLINE]
Comparison of coliphage and bacterial aerosols at a wastewater spray irrigation site.
Bausum HT,
Schaub SA,
Kenyon KF,
Small MJ.
Microbiological aerosols were measured on a spray irrigation site at Fort Huachuca, Ariz. Indigenous bacteria and tracer
bacteriophage were sampled from sprays of chlorinated and unchlorinated secondary-treatment wastewaters during day
and night periods. Aerosol dispersal and downwind migration were determined. Bacterial and coliphage f2 aerosols were
sampled by using Andersen viable type stacked-sieve and high-volume electrostatic precipitator samplers. Bacterial
standard plate counts averaged 2.4 x 10(5) colony-forming units per ml in unchlorinated effluents. Bacterial aerosols
reached 500 bacteria per m3 at 152 m downwind and 10,500 bacteria per m3 at 46m. Seeded coliphage f2 averaged
4.0 x 10(5) plaque-forming units per ml in the effluent and were detected 563 m downwind. Downwind microbial aerosol
levels were somewhat enhanced by nighttime conditions. The median aerodynamic particle size of the microbial aerosols
was approximately 5.0 micrometer. Chlorination reduced wastewater bacterial levels 99.97% and reduced aerosol
concentrations to near background levels; coliphage f2 was reduced only 95.4% in the chlorinated effluent and was
readily measured 137 m downwind. Microbiological source strength an meteorological data were used in conjunction
with a dispersion model to generate mathematical predictions of aerosol strength at various sampler locations. The
mean calculated survival of aerosolized bacteria (standard plate count) in the range 46 to 76 m downwind was 5.2%,
and that of coliphage f2 was 4.3 %.
PMID: 7055376 [PubMed - indexed for MEDLINE
Emission of microorganisms from sewage treatment plants depending upon construction differences of single structural
parts]
Eikmann T,
Schroder S,
Pieler J,
Bahr H,
Einbrodt HJ.
In order to examine the influence exerted by the differing design of individual water treatment plant units on the emission
rate of micro-organisms and the associated degree of exposure to which plant personnel is subjected, measurements
were taken at three different types of treatment plants. Measurements were made using "Biotest" RCS Air Samplers.
The total count of colonies was determined by means of Agar Strips GK-A (tryptic soy agar). Enterobacteriaceae were
quantitatively ascertained using Agar Strips C (MacConkey agar), particular attention being paid to the determination of
the coliform bacteria as faeces indicators. Agar Strips S (mannitol salt agar) were used to measure the count of
staphylococci using Agar Strips HS (rosa Bengal streptomycin agar). Before taking measurements, the prevailing
climatic conditions were recorded. It could be ascertained that the enclosure of the inflow area (screw conveyor pump
station and aerated grit removal tank) lead to a considerable increase in the concentration of microorganisms in the air
within the housing. The values dropped however, when adequate ventilation was provided. Differing oxygen in the
activated sludge tanks - finebubble aeration at the tank bottom or the blowing in of air via centrifugal blowers - lead to
large variations in the emission rates. However, the less the waste water is agitated, the lower the emission rates. In the
case of fine-bubble aeration, rates which are also normally to be found in the "non-burdened" outside air were even
recorded close to the aeration tank. In cases of centrifugal blower, the aeration tank should be covered with a shield.
With this type of aeration the waste water is emitted radially towards the walls of the tank. The use of a sprinkler unit on
an aeration tank equipped with centrifugal blower - to avoid foam formation on the surface of the water - does not lead
to an increase in the already high emission rate. An increase in air pollution through mould fungi from waste water
treatment plants could not be found. In conclusion, it can be said that different individual plant unit designs have a large
influence on the concentration of micro-organisms in the ambient air of places of work of waste water treatment plant
personnel. Emission rates can be limited to such a degree that, even in the immediate vicinity of the plant units, a
decrease of micro-organism concentrations can be attained as comparable to the area outside the treatment plant.
Evaluation of the environmental impact of microbial aerosols generated by wastewater treatment plants utilizing different
aeration systems.
Brandi G,
Sisti M,
Amagliani G.
Using three sampler devices (SAS, Andersen Six-Stages and All Glass Impinger), the environmental impact of bacterial
and fungal aerosols generated by municipal wastewater treatment plants operating with different methods of sludge
oxygenation were evaluated. The highest microbial concentrations were recovered above the tanks (2247 cfu m-3) and
in downwind positions (1425 cfu m-3), where a linear correlation (P < 0.05) was found between the quantity of sewage
treated and the entities of microbial aerosol dispersion. Moreover, an exponential increase (P < 0.05) in the bacteria
recovered from the air occurred at increasing times of treatment. However, after long-term plant operation, high
bacterial and fungal concentrations were found in almost all of the sites around the plant. Coliforms, enterococci,
Escherichia coli and staphylococci were almost always recovered in downwind positions. Considerable fractions (20-
40%) of sampled bacteria were able to penetrate the final stages of the Andersen apparatus and thus, are likely to be
able to penetrate the lungs. The plant operating with a fine bubble diffused air system instead was found to generate
rather low concentrations of bacteria and fungi; moreover, staphylococci and indicator micro-organisms were almost
absent. Finally, salmonellae, Shigella, Pseudomonas aeruginosa and Aeromonas spp. were not detected in either of the
plants. The results indicate a remarkable dispersion of airborne bacteria and fungi from tanks in which oxygen is
supplied via a mechanical agitation of sludge, and suggest the need to convert them to diffused aeration systems which
pose a lesser hazard for human health.
PMID: 10792545 [PubMed - indexed for MEDLINE]
Site-related airborne biological hazard and seasonal variations in two wastewater treatment plants.
Fracchia L,
Pietronave S,
Rinaldi M,
Giovanna Martinotti M.
Results of a study conducted to assess the degree of airborne bacterial contamination generated by two wastewater
treatment plants (WWTP) with different treatment systems and evaluate the dispersion of potential pathogens, have
been described. Aerosols samples were collected in summer and winter with an agar impact sampler from several plant
sites. External upwind and downwind controls were also examined. Total colony-forming counts of mesophilic and
thermophilic bacteria, actinomycetes and streptomycetes, Gram-negatives, coliforms and sulfite-reducers were
determined. Selective media were used in order to detect pathogenic bacteria. The lowest concentrations of mesophilic
and thermophilic bacteria were 8 and 28 CFU/m(3) in plants A and B respectively, the highest >40,000 CFU/m(3) in both
plants. Strains of Escherichia coli, Clostridium perfringens, Staphylococcus aureus and Enterococcus spp. were isolated
in some sites of the two plants. Salmonella spp., Yersinia enterocolitica and Legionella spp. were never detected. The
activities involving nebulization and mechanical aeration of wastewaters and the sewage inflows have proved to be of
greatest potential risk. In both plants, we found a statistically significant dependence of bacterial contamination on the
season for many of the analyzed parameters but a clear seasonal trend could not be observed.
PMID: 16678881 [PubMed - indexed for MEDLINE]
Related Links
[Exposure assessment to harmful agents in workplaces in sewage plant workers] [Med Pr. 2005] PMID: 16218135
Assessment of bioaerosols and inhalable dust exposure in Swiss sawmills. [Ann Occup Hyg. 2005] PMID: 15699057
Exposure to bioaerosols in a municipal sewage treatment plant. [Ann Agric Environ Med. 2003] PMID: 14677919
Bioaerosol sampling by a personal rotating cup sampler CIP 10-M. [J Environ Monit. 2006] PMID: 16395458
Workers' exposure to airborne bacteria and endotoxins at industrial wastewater treatment plants. [Am Ind Hyg Assoc J.
1994] PMID: 7992797
See all Related Articles...
Response to FOIA by EPA
My group in Feb of 2005 had requested, via Freedom of Information Act, certain data from the U.S. EPA on their
progress dealing with biosolids and resistance. In providing us answers to this request, EPA delayed its response for
about 6 months and then merely directed us to a section of the NERL’s website, which contained no usable information.
This site was (www.epa.gov/nerlesd1/chemistry/pharma/fq.htm#disposal), as evidenced by the following search results.
Similar results were found for other EPA web addresses. It is now Dec 2006 and there has been no other communication
from EPA. It would be difficult for EPA to both regulate sewage as a source of antibiotic resistance and augmented
virulence while at the same time promoting the land application of sewage byproducts for crops, especially those eaten
raw such as salad crops irrigated with reclaimed wastewater.
We did a key word search and the results are noted below.
Results of Searching the "Environmental Sciences" Area of EPA's Web Site
No matches found for transposon; 1402 files searched
No matches found for antibiotic resistance + biosolids; 1402 files searched.
No matches found for antimicrobial resistance + biosolids; 1402 files searched
No matches found for virulent pathogens + biosolids; 1402 files searched.
No matches found for plasmids + biosolids; 1402 files searched.
No matches found for mobile genetic elements; 1402 files searched.
No matches found for high level disinfection + biosolids; 1402 files searched.
Results of Searching EPA's Entire Web Site
We have searched the entire EPA site and found the following results. You may also return to searching for the same
terms within Environmental Sciences.
No matches found for high level disinfection + biosolids; 494732 files searched.
No matches found for plasmids + biosolids; 494732 files searched.
No matches found for transposons + biosolids; 494732 files searched.
No matches found for mobile genetic elements + biosolids; 494732 files searched.
No matches found for virulent pathogens + biosolids; 494732 files searched.
No matches found for antibiotic resistance + biosolids; 494732 files searched.
No matches found for antimicrobial resistance + biosolids; 494732 files searched.
Results of Searching the "Exposure Research" Area of EPA's Web Site
We have searched the area of EPA's site related to Exposure Research and found the following results. You may also
search for the same terms across EPA's entire site.
No matches found for prions + biosolids; 3352 files searched.
Results of Searching EPA's Entire Web Site
We have searched the entire EPA site and found the following results. You may also return to searching for the same
terms within Exposure Research.
No matches found for prions + biosolids; 530969 files searched.
+++++++++++++++++++++++++++=
Please feel free to contact me via return email.
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