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> **UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

**WASHINGTON D.C. 20460**

> **OFFICE OF THE ADMINISTRATOR**
>
> **SCIENCE ADVISORY BOARD**

October 1, 2008

EPA-SAB-09-001

The Honorable Stephen L. Johnson

Administrator

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Washington, D.C. 20460

> Subject: Consultation on EPA's Proposed Aircraft Drinking Water Rule
> (ADWR)

Dear Administrator Johnson:

EPA is responsible for developing and implementing the National Primary
Drinking Water Regulations (NPDWRs) for all public water systems.
Existing NPDWRs were designed for traditional, stationary public water
systems, not mobile aircraft water systems that are operationally
different. EPA's Office of Ground Water and Drinking Water requested
that the Science Advisory Board (SAB) Drinking Water Committee
(hereafter, the Committee) provide consultative advice on EPA's Proposed
Aircraft Drinking Water Rule (ADWR). EPA is proposing a rule that seeks
to protect passengers against pathogens by requiring development and
implementation of aircraft water system operation and maintenance. These
requirements include routine sampling for total coliforms and *E. coli*.
There remain technical issues regarding the sampling for total coliform
bacteria/*E. coli*, and these comprise the charge questions for the
Committee.

The proposed ADWR requires sampling each aircraft. EPA requested
comments on whether: (1) statistical sampling could replace sampling
water from every aircraft, and (2) hot water taps should be sampled in
aircraft galleys, if the galleys have no cold water taps (and if the
temperature of the hot water should be recorded).

On July 24, 2008, the Committee met via teleconference. With regard to
the first charge question, a majority of the Committee members (listed
in Enclosure 1) were not in favor of statistical sampling of aircraft
for drinking water quality at this time. Currently available information
on contamination was generally considered too sparse to interpret the
results for the whole fleet. Several members thought that information
gathered during implementation of this rule might allow such sampling in
the future, by providing information on how to stratify the samples,
e.g., by type of aircraft or by routes traveled by the aircraft
especially internationally.

Suggestions as to what types of information could be collected to
provide a basis for statistical sampling are in the members' individual
comments (Enclosure 2).

The second charge question generated a discussion of the effects of
water temperature and holding time, given that the current test is for
total coliform/*E. coli* bacteria that are unlikely to survive at a
temperature at which coffee can be brewed. It was noted that the
sampling of hot water has not been accepted as a legitimate type of
sample for coliform bacterial analysis. The members' preference was to
sample cold water taps; they were concerned that the hot water taps in
the galleys would produce false negative results. The members had
several suggestions for the situation where only hot water taps are
available in galleys; these are provided in the enclosed, individual
comments. For example, since the water from the galleys and the
lavatories has the same source, a second sample from the lavatory could
be more scientifically justified. Another suggestion was that the hot
water tap might be sampled after the heating element had been off for an
extended period of time. Again, several members expressed the
expectation that data from the initial years of sampling might be used
to make a more informed decision on this issue in the future.

The Committee would like to thank the presenters from EPA's Office of
Water for providing their expertise, perspectives, and insights. Their
contributions greatly increased our understanding of the Agency's
proposed rule and current information regarding safe drinking water on
aircraft. Written, individual responses to the charge questions were
provided by several Committee members, which are enclosed.

> Sincerely,

***/Signed/***

> Joan Rose, Chair
>
> SAB Drinking Water Committee

Enclosures

Enclosure 1

**U.S. Environmental Protection Agency**

**Science Advisory Board**

**Drinking Water Committee**

**CHAIR**

**Dr. Joan B. Rose**, Professor and Homer Nowlin Chair for Water
Research, Department of Fisheries and Wildlife, Michigan State
University, East Lansing, MI

**OTHER SAB MEMBERS**

**Dr. Mark Borchardt**, Director, Public Health Microbiology Laboratory,
Marshfield Clinic Research Foundation, Marshfield, WI

**Dr. John (Jack) Colford**, Professor, Division of Public Health,
Biology & Epidemiology, School of Public Health, University of
California, Berkeley, CA

**Dr. Penelope Fenner-Crisp**, Independent Consultant, Independent
Consultant, North Garden, VA

**Dr. Stanley B. Grant**, Professor, Department of Chemical Engineering,
School of Engineering, University of California, Irvine, Irvine, CA

**Dr. Jeffrey Griffiths**, Associate Professor, Public Health and Family
Medicine, School of Medicine, Tufts University, Boston, MA

**Dr. Gary King**, Professor of Microbial Biology, Department of
Biological Sciences, Louisiana State University, Baton Rouge, LA, USA

**Dr. Joseph R. Landolph, Jr.**, Associate Professor, Molecular
Microbiology and Immunology and Pathology, Keck School of Medicine and
Associate Professor of Molecular Pharmacology and Pharmaceutical
Science, School of Pharmacy, University of Southern California, Los
Angeles, CA

**Dr. Desmond F. Lawler**, Bob R. Dorsey Professor of Engineering,
Department of Civil, Architectural and Environmental Engineering,
University of Texas, Austin, TX

**Dr. Christine Owen**, Water Quality Assurance Officer, Tampa Bay
Water, Clearwater, FL

**Dr. Richard Sakaji**, Manager, Planning and Analysis for Water
Quality, East Bay Municipal Utility District, Oakland, CA, USA

**Dr. Gary Sayler**, Beaman Distinguished Professor, Joint Institute for
Biological Sciences, Oak Ridge National Laboratory, University of
Tennessee, Knoxville, TN

**Dr. David Sedlak**, Professor, Department of Civil and Environmental
Engineering, University of California-Berkeley, Berkeley, CA

**Dr. Gina Solomon**, Senior Scientist, Health and Environment Program,
Natural Resources Defense Council, San Francisco, CA

**Dr. Laura Steinberg**, Professor, Department of Environmental and
Civil Engineering, Southern Methodist University, Dallas, TX

**Ms. Susan Teefy**, Principal Engineer, Water Quality and Treatment
Solutions, Inc., Castro Valley, CA

**SCIENCE ADVISORY BOARD STAFF**

Dr. Resha M. Putzrath, Designated Federal Officer, 1200 Pennsylvania
Avenue, Washington, DC, Phone: 202-343-9978, Fax: 202-233-0643,
(putzrath.resha@epa.gov)

Enclosure 2

Comments from Individual Committee Members

Name Page

Dr. Joseph R. Landolph, Jr. 6

Dr. Desmond F. Lawler 9

Dr. Stanley B. Grant 12

Dr. Richard Sakaji 14

Dr. Gary Sayler 18

Comments from: Dr. Joseph R. Landolph, Jr.

Response to the EPA's Charge Questions Regarding the Proposed Aircraft
Drinking Water Rule and Statistical Sampling

**[1. Statistical Sampling:]{.underline}** **[EPA asks for SAB's
recommendation on (1) the use of]{.underline}**

statistical sampling methodologies, specifically on what type of
monitoring scheme would allow a statistical sample to be representative
of the whole fleet, and whether such methodologies, if allowed, should
only be used in conjunction with onboard or other supplemental treatment
such as adding a disinfectant or ultraviolet light?

Ideally, the best thing to do would be to sample each and every
airplane. I understand from the public meeting teleconference that there
are over 7,000 aircraft public water systems (Mr. Richard Naylor, EPA).
Sampling all of these systems would be a huge job, almost certainly
prohibitively expensive and time-consuming. Therefore, in my opinion,
statistical sampling is a necessary first step to obtain a picture of
the frequency of the contamination, in a rapid, cost-effective, and
efficient manner. At the same time, statistical sampling can be tricky,
because microbial contamination is distributed with Poisson statistics.
Hence, sampling only certain aircraft can the microbiologist to miss
bacterial contamination, particularly low levels of contamination, in
certain airplanes. Therefore, such sampling represents a lower bound to
the true frequency of the contamination, but it does give a rapid
estimate of the magnitude of the problem of microbial contamination of
aircraft drinking water systems. I have personal experience testing
newly filtered cell culture media for bacterial contamination. At low
levels of contamination, if you sample only every tenth bottle, you can
easily miss low levels of microbial contamination.

Therefore, to begin with, I recommend testing every tenth or even every
twentieth airplane to obtain data on microbial contamination, to
determine how serious the problem of contamination of aircraft water is
among the airlines. Once EPA obtains this data, then they would have a
better idea of what to do. Their preliminary data indicates that this
frequency is somewhere around 2%. If there is reproducible frequent
contamination of the water systems of many airlines, then I would
recommend utilizing in conjunction with statistical sampling, other
supplemental treatment, such as adding a disinfectant or ultraviolet
light, to cleanse the water of those aircraft that were found by testing
to have microbial contamination in their water systems. In this case,
draining the water systems of the aircraft, flushing and decontaminating
these systems with chlorine solutions, then draining this water and
rinsing the system with clean U. S. drinking water would be recommended.
Then, I could recommend finally adding back U. S. drinking water with a
1 ppm or 2 ppm chlorine residual, to maintain sterility of the water in
the airplane. Hence, I recommend that statistical sampling be used, but
in conjunctions with adding disinfectant or ultraviolet light treatment
to the drinking water on those aircraft that have contaminated drinking
water

I project that EPA would not have too many serious problems with water
on aircraft from the NATO European countries. However, water from some
Asian countries, from some African countries, and even from some Eastern
European countries, would likely not be as pure as that from the U. S.,
and would likely need to be treated or better, purged, the system
decontaminated with chlorine and rinsed, and fresh U. S. chlorinated
water added. We know a large amount about chlorination as a
disinfectant. Chlorination is inexpensive, effective and relatively
safe, except for DBPs in the treated water. Where microbial
contamination of drinking water is detected on aircraft, the water on
these aircraft should be flushed out, and the water systems should be
decontaminated with chlorine solutions. The water system should be
flushed again with drinking water from the U. S. with a chlorine
residual, and then the airlines should add back U. S. water in these
aircraft with chlorine, leaving a chlorine residual (1 or 2 ppm). This
would probably be the best way to maintain quality of the aircraft water
in terms of minimization of microbial contamination.

It should be made mandatory that each aircraft have a chlorine residual
in the drinking water system it contains. This would help to minimize
problems with microbial contamination.

Secondly, perhaps it might be wise to pick say three large airlines that
fly frequently to the U. S., one from say China, one from an African
country, and one from an Eastern European country, do some detailed
statistical testing on their water systems, and see what is needed to
bring these airline into compliance. This could be done on a voluntary
basis with the cooperation of these airlines. Then, this procedure could
be replicated on all the other airlines once it was established. This
would be a microbiology research project.

I understand from our public teleconference meeting on this topic that
inspection of airline water systems occurs once every five years. This
is not frequently enough. I recommend the rules on this topic be changed
so that the airlines are required to inspect their water systems once
per year, and that this inspection include testing for microbial
contamination.

**[(2) If allowed, what should be the statistical sample occurrence
triggers for total coliform and /or E. coli/fecal coliforms that would
require follow-up action in the entire fleet and what should the
follow-up action entail?]{.underline}**

If one in twenty aircraft (5%) had drinking water that was contaminated
with total coliforms and/or E. coli/fecal coliforms, this certainly
should be a trigger that would require follow-up action in the entire
fleet. Follow-up action should entail draining the water systems,
decontaminating the aircraft water supply system with high
concentrations of chlorine, flushing out the high levels of chlorine,
and adding back U. S. drinking water with a 1 ppm or 2 ppm residual of
chlorine to the system. This should happen with all aircraft in the
fleet. Once EPA established a baseline on the statistics of
contamination, sampling one in twenty aircraft, then EPA could take more
stringent action to reduce this frequency of contamination.

**[2. Temperature of Sample Taps]{.underline}**: **[EPA asks for SAB's
recommendations on (1) whether sampling should only be limited to cold
taps when they are available; and (2) if a cold tap is not available in
the galley, should the air carrier measure and provide sample
temperature to EPA to provide some indication of whether the temperature
achieved is high enough to alter the microbiology
results.]{.underline}**

**[Response]{.underline}**: (1) In my opinion, sampling should always be
limited to cold taps when they are available, to enhance the sensitivity
of detecting micro-organisms. This would be the best way to sample the
water to detect micro-organisms. If possible, the temperature of the
water in the tap should also be measured and recorded along with the
sample taken.

\(2\) If a cold tap is not available in the galley, then my opinion
would be that yes, the air carrier should still measure and provide the
temperature of the sample to the EPA to provide some indication of
whether the temperature achieved is high enough to alter the
microbiology results. This would help out, but of course, the best way
to do things to maximize the sensitivity of detection of micro-organisms
in the sample would be to take a sample from a cold tap when this is
available. I am uncomfortable in sampling hot taps, because obviously,
the high temperature will kill many of the organisms. In this case, when
only a hot tap is available, EPA should work with the carrier to see if
EPA can tap into the water system ahead of the heating elements and take
a sample, if this is possible. The next best thing would be to have the
air carrier sample only when the water has been turned off for some
time, and the temperature has reached room temperature, and then to
sample this water. This would help to maximize the sensitivity of
detecting micro-organisms.

However, given the time, effort, and expense of this microbial
contaminant testing program, I would recommend first sampling all the
aircraft that have cold taps, and compiling the statistics from these.
Once the cold water sampling and testing has been done, and acted upon,
then hot taps can be sampled, but as a second priority.

**Comments from: Dr. Desmond F. Lawler**

Response to the EPA's Charge Questions Regarding the Proposed Aircraft
Drinking Water Rule and Statistical Sampling

**[1. Statistical Sampling:]{.underline}** **[EPA asks for SAB's
recommendation on (1) the use of]{.underline}**

statistical sampling methodologies, specifically on what type of
monitoring scheme would allow a statistical sample to be representative
of the whole fleet, and whether such methodologies, if allowed, should
only be used in conjunction with onboard or other supplemental treatment
such as adding as disinfectant or ultraviolet light?

This question, taken from p. 19330 of the Federal Register Notice (73,
69, April 9, 2008) is in the context of sampling requirements to exhibit
compliance the proposed rules, not to determine the extent of drinking
water contamination under the existing (or non-existent) rules. In that
context, the question is whether sampling a representative sample of
aircraft of a given fleet could be used to show that the entire fleet is
in compliance. As pointed out in the FR notice, the inverse of this
condition would also be true---that is, if the results of a statistical
sampling method were negative, it would have to be taken that the entire
fleet was out of compliance, and all planes in the fleet would have to
undergo corrective action.

I should note at the outset that I am not an expert on statistical
methods and am willing to accept the judgment of others that are more
expert in this area than I am. While I have had graduate courses in
statistics and use statistical analysis in evaluating research data, I
am not in a position to comment knowledgeably on the potential for the
statistical methods to ensure the public health. With that *caveat*, I
offer the following ideas.

In the absence of supplemental treatment, I do not believe that a
statistically-based method of sampling some portion of the fleet would
be satisfactory. Each plane has its own system and its own history at
any given moment, and the potential for contamination on one plane is
independent of that potential on another. Even though the proposed rule
requires only occasional sampling of every plane, it does require it of
every plane, and that requirement would appear to provide both a better
protection of the public health and a more defensible position for both
the EPA and the industry itself in showing that they are making every
reasonable effort to protect the public health by the provision of safe
drinking water on every plane.

My concern has two bases. First, the data provided in the FR notice from
the sampling that has been done suggests a far higher incidence of
coliform-positive results than is typically found in public drinking
water supplies. In municipal distribution systems, a coliform-positive
result is rare, certainly far less than the 2.6 to 15.1% found in the
various studies shown. The exact causes of this are unknown, but the
extensive handling of the water between the public water supply and the
aircraft taps includes many points where contamination and loss of
disinfectant residual are possible.

Second, since the water in an aircraft can often be a blend of waters
from different public water supplies, the water chemistry of the blend
with respect to the carrying of a disinfectant residual might be very
different than any of the blended sources. Specifically, I am concerned
about the real possibility that one source might have a free chlorine
residual and another might have a chloramine residual. Any water with a
chloramine residual also has a free ammonia concentration, and that
ammonia will react with the free chlorine from the other source;
depending on the relative volumes of water from the two sources and the
concentration of free chlorine in one and free ammonia in the other, it
is quite possible that the residual will be destroyed by the well-known
"breakpoint" reaction. Such a blended water would have no disinfectant
to ward off coliform or other biological contamination. A biofilm
created under these conditions might be able to withstand subsequent
periods of a chlorine or chloramine residual.

I can believe that a statistically-based sampling program to show the
provision of safe drinking water could be developed to account for the
first of my concerns, since the handling steps are similar everywhere.
But the specific history of a particular plane with respect to its
taking on water from different sources would greatly influence the
second possibility, and that this individuality makes a
statistically-based program unlikely to succeed in all cases.

On the other hand, I do believe that if UV systems were installed on
every plane, that a statistically-based system could be reasonable.
Although I still believe that sampling of every plane on a regulated
schedule (as currently proposed) would be better, the uniformity of
on-board treatment would reduce the independence of each aircraft in
terms of the likelihood of contamination on the drinking water.

Other notes:

1.  I believe that UV should be required on every commercial aircraft
    holding more than some number (perhaps 50) people.

2.  I do not think that it is reasonable to require a residual
    disinfectant; the chemistry is too complex to think that this could
    be done well by relatively untrained people. In the end, it would
    appear cheaper to insist on UV treatment for additional protection
    than that provided by the water suppliers.

**[2. Temperature of Sample Taps]{.underline}**: **[EPA asks for SAB's
recommendations on (1) whether sampling should only be limited to cold
taps when they are available; and (2) if a cold tap is not available in
the galley, should the air carrier measure and provide sample
temperature to EPA to provide some indication of whether the temperature
achieved is high enough to alter the microbiology
results.]{.underline}**

I believe the answer should be yes to both of these questions. My
understanding is that coliforms are inactivated at a temperature well
below the range that is used for making coffee or tea, and in that case,
the issue is only whether a reasonable temperature range is achieved
prior to any use of the water (at least with respect to coliform
bacteria).

It should be noted, however, that relying on a self-report by the
airline holds some risk. Whereas the coliform testing would be done by
an independent laboratory, these temperature readings would necessarily
be done by the airline personnel. The greatest protection comes from the
fact that it is in the best interest of the airlines to have good
customer service, and in this case that means sufficiently high
temperatures to make hot coffee. In turn, that would intrinsically mean
sufficiently high temperatures to inactivate coliforms. Nevertheless, I
believe requiring temperature measurement on the same schedule as the
sampling should be done.

**Comments from: Dr. Stanley B. Grant**

Final Response to the EPA's Charge Questions Regarding the Proposed
Aircraft Drinking Water Rule and Statistical Sampling

**[1. Statistical Sampling:]{.underline}** **[EPA asks for SAB's
recommendation on:]{.underline}**

**[(1) the use of statistical sampling methodologies, specifically on
what type of monitoring scheme would allow a statistical sample to be
representative of the whole fleet, and whether such methodologies, if
allowed, should only be used in conjunction with onboard or other
supplemental treatment such as adding as disinfectant or ultraviolet
light?]{.underline}**

If the current draft of the ADWR is implemented, a large database will
be quickly obtained on the water quality aircraft drinking water
supplies. These data should be analyzed to determine if positive
coliform samples are associated with particular airplane drinking water
systems, flight routes, water blending practices, etc. These data may
also shed light on the degree to which aircraft water systems can be
treated as a statistically homogeneous population, for which
representative statistical sampling designs can be formulated. However,
given the unique history of each aircraft's drinking water system
(source water used, topping off procedures, frequency of disinfection)
it would be prudent to test all aircraft drinking water systems several
times per year until the question of statistical homogeneity can be
addressed.

**[(2) If allowed, what should be the statistical sample occurrence
triggers for total coliform and /or E. coli/fecal coliforms that would
require follow-up action in the entire fleet and what should the
follow-up action entail?]{.underline}**

It is hard for me to conceive of a situation where, for example, the
log-mean total coliform concentration of the entire fleet would suddenly
shift up, thus triggering a follow-up action for the entire fleet. As
noted above, I believe that the current draft ADWR makes sense: all
aircraft drinking water systems should be tested several times per year
so that bad actors can be identified and remedied.

**[2. Temperature of Sample Taps]{.underline}**: **[EPA asks for SAB's
recommendations on (1) whether sampling should only be limited to cold
taps when they are available; and (2) if a cold tap is not available in
the galley, should the air carrier measure and provide sample
temperature to EPA to provide some indication of whether the temperature
achieved is high enough to alter the microbiology
results.]{.underline}**

Heat treatment of water kills most enteric bacteria and viruses provided
that the water temperatures exceed 65 degrees C. However, a study[^1] of
bacterial survival in drinking water found that "at 13 of the 14
tourist-oriented hotels in four countries, water from the hot water tap
did not reach temperatures of 65 degrees". The authors of this study
concluded that "food and water that are too hot to touch may still be
contaminated with bacterial enteropathogens."

Based on the aforementioned study and other similar studies, one can
envision a scenario in which a human health risk might be posed by
drinking water from the hot water tap, provided that the water
distribution system on the plane was contaminated, and the water in the
hot water tap did not achieve and sustain a temperature of at least 65
degrees C. It is important to note that in such a scenario,
contamination of the aircraft drinking water distribution system would
be evident by sampling the coldwater tap.

Based on the above discussion, I recommend that the coldwater tap be
sampled preferentially, as currently recommended in the EPA technical
guidance document for the ADWR. If only hot water taps are available on
a particular airplane, or in the forward galley, water samples from the
hot water tap should be collected and analyzed for total coliform.
Ideally, this sampling would take place after the heating element for
the hot water tap was turned off for some time, and the water flowing
out of the tap was at room temperature. In all cases, EPA should require
measurement and reporting of water temperature and chlorine residual at
the time of sampling, together with the location of the sampling point
within the water distribution system (e.g., rear lavatory, front galley,
cold tap, hot tap...). Such information will be extremely useful for
identifying risk factors for contamination of drinking water aboard
aircraft, and the associated human health risk.

**Comments from: Dr. Richard Sakaji**

**EPA asks for SAB\'s recommendation on: (l) the use of statistical
sampling methodologies, specifically on what type of monitoring scheme
would allow a statistical sample to be representative of the whole
fleet, and whether such methodologies, if allowed should only be used in
conjunction with on board or other supplemental treatment such as adding
a disinfectant or ultraviolet light; and (2) if allowed, what should be
the statistical sample occurrence triggers for total coliform and/or E.
coli/fecal coliform that would require follow-up action in the entire
fleet, and what should the follow-up action entail.**

The idea of relating the frequency of monitoring to the frequency with
which the water system is flushed and cleaned makes sense from a
relative risk standpoint. As the introduction to the rule states, the
aircraft water systems are storage reservoirs or distribution systems,
but are unlike any typical noncommunity water system (NCWS). Unlike
their "fixed" counterparts, which receive water from a single source,
the source water for aircraft can vary markedly over the course of a
day, week, month, or even year. An aircraft may take water from several
different, surface or ground water sources within a given day, as
aircraft move from airport to airport (some regulated; some not),
depending on their flight schedules. Since no two aircraft fly the
identical route and board water from the same locations, it would not be
appropriate to assume that the microbiological water quality on any two
aircraft would be identical. Therefore, the population is not homogenous
and no single aircraft's water system should be considered
representative of the overall population.

Randomly selecting aircraft as being representative of the whole fleet
would hardly be considered adequate, unless the number sampled was
determined *apriori* considering, at a minimum, the variability in the
population, the variability in the analytical method, and the level of
confidence desired in the final result. Generally, the greater the
variability and the higher the confidence level, the greater the number
of samples that will be required to have confidence the program is
meeting its objectives.

Under a random sampling program, if the objective remains to have each
aircraft sampled annually, then the level of monitoring would be
consistent with the minimum sampling allowed in noncommunity water
systems under the current TCR. However, there are specific terms and
conditions that must be met in order to allow this minimum sampling and
there are indications that these conditions will become more restrictive
under the revised TCR currently being negotiated.

If the purpose of the monitoring program is to ensure compliance with
the TCR objectives, then one should consider some of the discussions
taking place in the current FACA negotiations for revising the current
TCR. The draft AIP has TC+ (initial sample and followup) being used as a
treatment technique which triggers an "assessment." TC is no longer
being used as an MCL, but a treatment technique, triggering an
assessment and remedial action (e.g., flushing boosting disinfection;
similar to what is proposed in the ADWR). Public notification is
required only if the followup monitoring and assessments are not carried
out. The more serious and recognized acute problem is with E. coli or
fecal coliforms, which triggers almost immediate public notice.

The agreement in principle (AIP) for the TCR has annual sampling as a
minimum, but only under specific conditions. Otherwise minimum sampling
for each noncommunity water system is quarterly. Also, the monitoring
frequency is increased following certain TC and EC "hit" combinations
and not allowed to return to reduced monitoring until several criteria
are met. Following a coliform "hit" a noncommunity could be forced into
monthly monitoring, which, for airlines could present a problem for
individual aircraft. If the monitoring and assessments are not
identical, then, from a risk management standpoint, there will be a
difference in the risk management level between the TNCWS and the
aircraft.

A random sampling program for a fleet of aircraft would probably not be
likely to detect water systems with a TC+. Based on an annual sampling,
the odds of selecting the aircraft to sample that would be TC+ would be
very small. While the frequency of the TC+ was a sizeable percentage in
the preliminary work conducted under the AOC, as the frequency of TC+
decreases, the odds of selecting or finding the aircraft that is TC+
becomes slimmer and the number of samples collected to be fairly
confident the samples are representative would increase exponentially.
Adding the confounding factor of aircraft water system maintenance only
decreases the likelihood of finding a TC+. This does not preclude the
possibility that aircraft water systems may not be safe, but that the
sampling program, due to frequency is masking the problem.

I would recommend against developing a monitoring program based on a
random statistical sampling of the whole fleet. This would be the same
as using a random statistical sampling of all noncommunity water systems
to determine that each water system in the population was in compliance
with the TCR. Like each noncommunity water system, each aircraft should
be considered an independent entity and not representative of the
population.

The intent of the ADWR seems to have each aircraft's water system
sampled at least once a year, but does not specify when the system is to
be sampled. Specific time of sampling appears to be designated in the
sampling plan. Once a year is probably a minimum sampling frequency, but
one should consider what the objective of the monitoring program might
be. For a variety of reasons sampling should be conducted on aircraft
closest to their next cleaning, in fact, those aircraft that are closest
to their next water system cleaning and disinfection are those that
should be sampled.

If the objective of the monitoring program is to ensure the safety of
the aircraft water system, by monitoring the microbiological water
quality, then the monitoring program should focus on the efficacy of the
maintenance practices, i.e., the samples should not be random, but
should be collected just prior to maintenance (systematic). This will
ensure the cleaning and maintenance intervals are sufficient to prevent
a TC positive. It is my opinion that a systematic sampling approach
would provide much more protection of aircraft water supplies than a
random sampling program and could easily be tied to aircraft maintenance
schedules.

Aircraft undergoing a level B, C, or D maintenance may not fly for 24
hours or more; collecting a TC sample before the system is emptied and
cleaned would provide an indication whether the maintenance practices
are adequate to maintain the microbiological quality of the water
system. If the sample comes back positive, the plane will not be taking
on passengers or crew and will be easily accessible for a repeat sample
(unlike trying to track an aircraft that is in service and has had a TC
or EC positive). Once that sample comes back clean the plane can be
released. If the water system sample is still positive the aircraft
water system can be recleaned and sampled (from a risk management stand
point the USEPA can consider releasing the aircraft after the resample
\[only on a TC+\]), since the resample will occur after water system has
been cleaned and disinfected. This will provide strong economic
incentive for airlines to pay attention to the maintenance of the
aircraft water systems, as they cannot afford to have aircraft "down"
any longer than necessary. If the sample is EC positive (first sample),
then a risk management choice must be made as to whether the aircraft
should be released. If the second sample comes up TC+ a similar risk
management decision will have to be made.

If the water system showed signs of E. coli or fecal contamination while
undergoing maintenance, there would still be time to reclean and
disinfect the system (and resample) before returning the aircraft to
flight status. Overall, a systematic sampling program tied to the
maintenance schedule would not only provide quantitative information on
the efficacy of the water system maintenance schedule, but would
minimize down time on the aircraft reducing the economic impact on the
airlines, reduce public notification, and public exposure (and adverse
public reaction). Given the airlines have minimal or no "spare"
aircraft, this will encourage them to develop a flushing and
disinfection program that will minimize maintenance downtime and reduce
public exposure and probably push them toward on board treatment
systems.

Another recommendation that could help is to have airlines check to make
sure there is a chlorine residual in the water being boarded. The
airlines should probably consider only boarding water that contains a
chlorine residual. If the chlorine residual is below detection, the
airline has a choice of boarding the water or not. Lack of a chlorine
residual increases the potential for microbiological issues. A plane
that boards water without a chlorine residual should be allowed to
continue in service, like a distribution system reservoir, but the
airline should consider itself at risk. However, as was discussed in the
telecom, one SAB member made a point about mixing chloraminated and
chlorinated drinking water. I support his statements regarding the
mixing of a free and combined chlorine residual without regard to the
different chemistries.

**EPA asks for SAB\'s recommendation on: (1) whether sampling should
only be limited to cold taps when they are available; and (2) if a cold
tap is not available in the galley, should the air carrier measure and
provide the sample temperature to EPA to provide some indication of
whether the temperature achieved is high enough to alter the
microbiological results.**

What is the purpose of sampling? If it is to characterize the water in
the system (tanks and lines), then sampling from the cooler tap would be
more appropriate, since coliforms are inactivated at warmer
temperatures, leading to false negatives.

If there are two separate water systems (fore and aft), these systems
should be sampled separately and considered to be independent systems.
This should not be an issue if the tanks are interconnected, as
discussed during the teleconference. Some provision in the rule should
make sure that, if water systems are not interconnected that they are
each sampled during routine monitoring.

When collecting samples from the galley with in-line filters, the lines
should be well flushed before the sample is collected. The POU device
study done a number of years back indicated a flush of bacteria from
carbon filters after sitting for overnight. Granted these in-line
filters probably will not adsorb organics, as the carbon filters will,
and will therefore not provide a growth medium for bacteria (not
necessarily pathogenic). Nevertheless, bacteria can collect and
concentrate on the filters and potentially migrate through them, since
the filters are not absolute filters. To minimize the impact it might be
advisable to "flush" the system out by running the tap to waste for
10-15 minutes while preparing an aircraft for flight status after a
layover.

Another issue is the collection point for the sample. While the SAB was
asked about sampling the hot or cold tap, there is the issue of location
with respect to the lavatory collection point. A lavatory sample may
represent a very different risk management paradigm than a sample
collected from a traditional NCWS, in which a sample is not usually
collected from a lavatory. Collection of the sample from the lavatory
might increase the odds of a false positive. If the risk management
paradigm is to ensure the quality of water delivered from the storage
tank through the distribution system to the faucet, then the sample
should be free from potential contamination from an external source.
While the sampling technique in the guidance manual calls for the use of
an alcohol or disinfectant swab, I wonder how effective this is relative
to flaming a tap? Is it possible for airborne bacteria to cross
contaminate the sample? The TCR sampling protocols recognize the need to
remove aerators before collecting a sample, something that is not noted
in the ADWR guidance (this will increase the complexity of sample
collection in an operational aircraft). External contamination would not
be representative of the storage tank and distribution system, and could
lead to public notification or aircraft shutdowns. This would argue for
or support the collection of samples tied to the aircraft maintenance
cycle which would allow the sample to be collected from the underdrain,
reducing potential cross contamination from the lavatory, where the
likelihood of fecal contamination is higher.

One point that was not discussed in the teleconference was whether most
of the positive TC, FC, or EC samples from the mandated sampling program
were from the lavatory or galley. I recommend the EPA attempt to harvest
this information from their AOC monitoring.

**Comments from: Dr. Gary Sayler**

**SAB consultation on ADWR, Fed. Reg. 73 (69):19321-19348. April 9,
2008**

General comments

The Fed Reg proposed rule is well presented, generally clear, and
technically appears well though out given that there have been no
reported significant scale, disease outbreaks for passengers consuming
potable water made available by the aircraft industry during flight.
There will always be concern out the safety of water supplies made
available to the air traveling public and in particular for equipment
traveling to foreign destination. The proposed rule is a step in the
right direct to reduce risk to the air passenger of exposure to
potential pathogens in the on board potable water supply and
distribution system.

The proposed rule continues the use of conventional and some archaic
measurement protocols of the presence of total coliform (TC) bacteria to
trigger further monitoring for fecal coliforms and E. coli, along with
flushing and disinfection of the potable water system, to reduce
exposure risk to the air traveling public by either eliminating the
apparent contamination or consumption of the affected water.

> Consideration of continued and future development of more modern
> measurement protocols that could be multiplexed to provide
> quantitative information of the presence of both indicator organisms
> and specific pathogens should be considered. Such tools may also
> provide microbial source and dissemination tracking capability should
> and invent occur.
>
> Greater thought to requirements for on board point source disinfection
> using for example UV disinfection or filtration technology is
> encouraged.

The proposed monitoring and sampling plan is inversely related to the
frequency of routine flushing and disinfection maintenance schedule for
the aircraft. Sampling from the water system for TC analysis following
this maintenance is not permitted before 72 hr. This appears to be an
acceptable approach to provide the minimal level of protection for the
air traveling public. However, important information not reported of the
volume range of the of water supple in individual aircraft model as well
as on board residence time and time domain for replacement, refill or
topoff would be useful in fully assessing the sampling and monitoring
plans.

Background data provided to support the rule development and drive the
AOC is quite useful and provides a range from 2.8% to 15% of the
potential plane that may be out of compliance at anyone time. This is a
rather broad range and 15% reported TC positive (based on 2004 data)
certainly appears higher than anticipated. This is also more than double
that for the next highest reported estimate. More recent EPA and ATA
analysis of less than 3% TC positive would appear to be more consistent
with general DW findings.

Useful information not reported relates to variation. For routine
sampling and monitoring were replicated sampling measurements made (not
just repeat samples after a positive outcome) and, if so, what were the
results even if not done for all flights examined? Were the individual
test replicated to determine internal variation of the methods (or what
is the historical variability of the TC test)? Further statistical
sampling designs are dependent on such data along with any new dating
from continuous AOC driven monitoring. Have any TC, FC, or EC data been
obtained that indicates source water in the major contributor to
positive results rather than the equipment or contract services?

**Charge question responses.**

**Charge 1 Statistical Sampling of fleet rather than all individual
aircraft.**

*At the present time there does not appear to be a scientific rationale
for use of statistical sub-sampling of the fleet for a representative
lot (sub-population) of aircraft rather than sampling the whole at least
once a year.*

This conclusion is drawn largely from the complex heterogeneity of the
aircraft and flight routes (water sources) involved. While statistical
sub-sampling for microbiological quality control is widely used in
industry (food, pharmaceutical, cosmetics, etc.), it appears that such
product lots are much more representative of a more homogenous product
as a whole. For example, it is much clearer that sub-sampling from a lot
of ground beef is sufficiently representative that each individual
ground beef patty or consumer sized retail product is not required.
Contamination of the lot forces a total recall of all product of that
lot. In the case of the ATA, what constitutes a lot, the whole industry
fleet or the fleet of a given airline? Response to the event would be to
either demand prohibition of potable water consumption and/or forced
flushing and disinfection maintenance for all; resulting in the majority
of conforming airplanes (perhaps as many as 97% based on current data)
suffering the same fate as the guilty. Sub-sampling for microbiological
quality control is not like sub-sampling for airframe stress fractures
or missing engine mounting pins.

There are excellent reviews and designs of statistically based
microbiological sampling plans and discussions of statistical analysis
of the data for foods water and consumer products. A particularly good
HACCP example (albeit foods) is:

> Susanne Dahms (2004). *Microbiological sampling plans-Statistical
> aspects.*
>
> Mitt. Lebensm. Hyg. 95, 32-44.
>
> (See also <http://www.fao.org/docrep/w6419e/w6419e04.htm> and
>
> US EPA final report contract 668-D4-0091, Data Quality Objectives and
> Statistical Design Support for Development of Monitoring Protocol for
> Recreational Waters. 8/24/99)

**Charge 2 Should sampling be limited to cold taps and if not available
in the galley should the temperature of the tap be reported to EPA?**

*Sampling should be limited to cold taps without requirement of hot tap
sampling or temperature reporting to the EPA*

There appears no justification for hot tap sampling as it appears that
that heating by and large occurs at point of use. Heating itself if,
even insufficient to pasteurize the sample, will induce a severe time
dependent thermal stress that will seriously effect the cultivation and
enumeration protocol resulting in false negative qualitative responses.
Basically, the stressed organisms will not reproducibly grow or perform
within the current test time frame of response for accurate TC or FC
tests.

In lieu of hot tap sampling a second cold tap sampling should be
included for more accurate evaluation (reproducibility) of the
monitoring protocol.

[^1]: Bandres, J.C., Mathewson, J.J., DuPont, J.L. 1988 Heat
    susceptibility of bacterial enteropathogens. Implications for the
    prevention of travelers' diarrhea" *Arch Intern. Med*.
    **148**:2261-2263.