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Environmental Protection
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Inhalation Exposure to Contaminants
From a Water Distribution System
INTRODUCTION
When contaminants are present, various studies have shown that a number of activities involving the
use of drinking water potentially can release harmful amounts of volatile contaminants or generate
aerosols that contain contaminants. Showering and the use of ultrasonic humidifiers have been shown
to produce substantial quantities of aerosols. Ultrasonic humidifiers, which create a cool mist by means
of ultrasonic vibration, can release larger amounts of both microorganisms and dissolved minerals
than steam vaporizers. Volatile contaminants can also be inhaled during showering. During a
contamination incident in a water distribution system, individuals engaged in showering or humidifier
use could potentially inhale large quantities of contaminated aerosol particles or volatile chemicals. To
address this concern a software capability was developed to allow the system-wide quantification of
potential adverse health effects associated with inhalation exposure during showering and during the
use of ultrasonic humidifiers. This capability has been incorporated into the consequence estimation
module (CEM) of the U.S. Environmental Protection Agency's (EPA's) Threat Ensemble Vulnerability
Assessment, Sensor Placement Optimization Tool (TEVA-SPOT) (See Figure 1). This advancement
represents a major step forward in the capability to quantitatively assess the consequences from
inhalation exposures associated with the use of contaminated drinking water.
APPROACH
Drinking water distribution systems (WDS) can be
contaminated either intentionally or unintentionally. WDS
contamination has the potential to cause adverse health
effects in the population and numerous studies have
considered such ingestion consequences. The potential also
exists for short-term inhalation exposures to elevated air
concentrations of contaminants during a contamination
incident. Various domestic uses of water can release volatile
contaminants or generate contaminated aerosols. The
largest inhalation exposures to volatile contaminants in
water result from showering (Hines, SA, et al., 2013). The
EPA's Homeland Security Research Program (HSRP)
conducted a screening-level assessment of the relative
potential for inhalation exposure to aerosol-borne
contaminants associated with common water uses and
found that ultrasonic and cool mist (impeller) humidifiers and
showering produce the highest exposure doses (Hines, SA,
et al., 2013). (Cool mist (impeller) humidifiers were found to Figure 1. TEVA-SPOT's "About
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ingestion exposures, potential inhalation exposures during a water distribution system contamination
incident have received little attention.
A flexible, extensible analytical framework was developed to quantify the consequences of
contamination incidents (Davis et al., 2014). It relies on the use of theTEVA-SPOT software for situations
in which substantial system-specific information is available. This technical brief outlines modifications
to TEVA-SPOT that were made to enable modeling of the system-wide adverse human health effects
associated with inhalation exposure to microbial and chemical contaminants. Both volatile and non-
volatile chemical contaminants are considered in the model. Various studies have examined the
inhalation of volatile chemicals and aerosols produced by showering and the use of humidifiers.
However, the results of these studies have not been used to assess system-wide health effects during
a contamination incident.
The TEVA-SPOT analysis framework was expanded to determine these inhalation-related
consequences. To determine the inhalation-related adverse effects requires estimating the quantity of
contaminant that is inhaled by individuals who use water from the WDS. Obtaining such an estimate
requires estimating the water and air concentrations of the contaminant at the locations where exposures
occur and accounting for the behavior of the individuals at those locations.
Exposures during a contamination incident may occur over a short period of time and the timing of the
actual exposures is important because of the changing contaminant concentration in the water.
Consequently, the incorporation of an inhalation showering pathway into the analytical framework of
TEVA-SPOT required the development of a timing model for showering and the use of statistical models
for frequency and duration of showering incidents. Data on humidifier use is much less developed than
for showering. Therefore, a more simplified behavior model was developed for humidifiers to allow
sensitivity analyses to be carried out to determine how the parameters describing humidifier use
influence potential system-wide consequences. Additionally, TEVA-SPOT's CEM was expanded to
allow the user to easily perform Monte Carlo analyses (e.g., for uncertainty and sensitivity analyses).
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FEATURES OF APPROACH
The capability to estimate exposure, dose, and
consequences associated with inhalation during
showering and ultrasonic humidifier use was
incorporated into the CEM of TEVA-SPOT. A five
step process is used for assessing inhalation
exposures and determining consequences. First,
TEVA-SPOT estimates contaminant concentrations
in water at points of water use throughout the WDS
during the contamination incident (see Figure 2
which shows water concentrations of a contaminant
versus time at two different receptor locations in a
WDS during a contamination incident). Next, TEVA-
SPOT accounts for the behavior of individuals using
water from the system. In step 3, TEVA-SPOT
estimates the air concentrations of contaminants at
points of exposure at the time when individuals are
using water. In step 4, TEVA-SPOT estimates
potential inhalation doses for individuals. Finally, in
step 5, TEVA-SPOT determines the statistics for
water system-wide consequences.
ess
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Time after Injection (h)
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Figure 2. Illustration of temporal nature of
contaminant concentrations at two different
receptor locations in a WDS during a
contamination incident.
A capability was added to TEVA-SPOT to account for the behavior of individuals associated with
showering and ultrasonic humidifier use. Figure 3 shows a probability density function for daily starting
times for showering incidents developed using data collected by time-use surveys (ATUS, 2013).
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0.1"
0.1"
0.05
0
6
12
18
24
Time (h)
Figure 3. Probability density function
for the starting times of single, daily
showering incidents developed with
time-use data collected by the U.S.
Census Bureau.
*2, exit shower
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Time (min)
Figure 4. Showering inhalation model
accounts for the time variability of air
concentration of a contaminant during
showering.
The plot in Figure 3 shows starting times for single showering incidents (i.e., a person takes only
one shower each day). Models were also developed and incorporated into TEVA-SPOT that
estimate air concentrations of contaminants at points of exposure when contaminated water is being
used. Figure 4 illustrates how the air concentration of a contaminant varies with time during
showering and after the shower is turned off.
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These various models were incorporated into TEVA-SPOT to allow inhalation doses to be estimated
for individuals. Statistics for water system-wide consequence can then be determined. Figure 5 is a
screen capture of TEVA-SPOT's new exposure pathway module - inhalation from showering. On
the left side of the panel the user enters parameter values and inputs (i.e., dose levels) for
determining consequences based on dose level; the right side of the panel (if selected) has
parameter inputs that are used to obtain dose response (i.e., some defined health effect end point)
based consequences. The screen capture shows example parameter inputs for a volatile chemical.
I A>\ Edit Health Impacts Analysis Parameters
Contaminant
Name Chemical
Type Chemical/Toxin
-
Select Defaults...
Average Body Mass (kg) 70.0
Ingestion Inhalation - Showering Inhalation - Humidifier
f7] Calculate Inhalation - Showering
Dose Calculation Parameters
0.012
2.0
Dose Calculation Method Transfer Efficiency
Breathing Rate (mA3/rnin)
Shower Volume (mA3)
Time in shower after off (rnin) 2.0
Average Transfer Efficiency
Water Flow Rate (L/min)
Air Exchange Rate (l/min)
0.8
9.0
0.2
Timing Model Fixed
One Shower Per Day:
Time 1
6.5
Time 2
21.5
Probability 1 0.7
Probability 2 0.3
Two Showers Per Day:
Time 1	6.5
Duration Model Probabilistic ^
Showering Frequencies
One/day 0.6 Two/day 0.18 None/day 0.22
Probabilistic Iterations 1000
Random Number Seed 1
Thresholds
Dose
Response
¦4,0.001,0.01,0.1,1.0,10.0,100. C
Edit
fyj Calculate Dose-Response
Dose Response Method
Dose-Response calculation method Probit
LD50 / ID50 0.001
Beta
1.0E7
Disease Progression Parameters
Latency Time (hrs) 1
Fatality Time (hrs) 1
Fatality Rate 1.0
Worst-case Results
Number of worst-case fatality scenarios to save 1
Number of worst-case dosage scenarios to save 0
Edit
Use one server per node
OK
Cancel
Figure 5. Screen capture from TEVA-SPOT's CEM showing example parameter
inputs for a volatile chemical.
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FURTHER DEVELOPMENT
The TEVA-SPOT analysis framework is flexible and readily extended, so, if desired, it can
accommodate future enhancements related to improved network models, improved models for the
behavior of individuals, and the consideration of additional sources of microbial and volatile and
non-volatile chemical contaminants.
FOR MORE INFORMATION
TEVA-SPOT is an open source software program composed of software modules. TEVA-SPOT
uses EPANET (Rossman, 2000) to simulate contaminant transport in a water distribution system.
TEVA-SPOT can be obtained from EPA website (http://www.epa.gov/nhsrc/index.htm). The intended
audience for this tool is water utilities and those supporting water utilities interested in assessing
population-based consequences from inhalation of microbial and volatile and non-volatile chemical
contaminants from drinking water.
To learn more contact Robert Janke (ianke.robert@epa.gov) or visit our website
(http://openwateranalytics.github.io/epanet-rtx/index.html) for underlying TEVA-SPOT and EPANET
modules' source code.
If you have difficulty accessing this PDF document, please contact Kathy Nickel
(Nickel.Kathy@epa.gov) or Amelia McCall (McCall.Amelia@epa.gov) for assistance.
REFERENCES
American Time Use Survey (ATUS). American Time Use Survey User's Guide: Understanding
ATUS 2002 to 2012, Bureau of Labor Statistics, June 2013.
Davis, MJ, Janke, R, and Magnuson, ML. A framework for estimating the adverse health effects of contamination
incidents in water distribution systems and its application. Risk Analysis, 34(3): 498-513, March 2014.
Hines, SA, et al Stephanie A. Hines, Daniel J. Chappie, Robert A. Lordo, Brian D. Miller, Robert J. Janke, H. Alan
Lindquist, Kim R. Fox, Hiba S. Ernst, Sarah C. Taft. Assessment of relative potential for Legionella species or
surrogates inhalation exposure from common water uses. Water Research, 56:203-213, December, 2013.
Rossman LA. EPANET 2 Users Manual. Cincinnati, OH, U.S. EPA, Office of Research and Development, National
Risk Management Research Laboratory, Report No. EPA/600/R00/057, September 2000.
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Disclaimer
The U.S. Environmental Protection Agency through its Office of Research and Development funded,
managed, and collaborated in the research described here. This technical brief has been subjected to the
Agency's review and has been approved for publication. Note that approval does not signify that the contents
necessarily reflect the views of the Agency. Mention of trade names, products, or services does not convey
official EPA approval, endorsement, or recommendation. Work at Argonne National Laboratory was
sponsored by the EPA under interagency agreement through U.S. Department of Energy Contract DE-AC02-
06CH11357.
U.S. EPA's Homeland Security Research Program (HSRP) develops products based on
scientific research and technology evaluations. Our products and expertise are widely used
in preventing, preparing for, and recovering from public health and environmental
emergencies that arise from terrorist attacks or natural disasters. Our research and products
address biological, radiological, or chemical contaminants that could affect indoor areas,
outdoor areas, or water infrastructure. HSRP provides these products, technical assistance,
and expertise to support EPA's roles and responsibilities under the National Response
Framework, statutory requirements, and Homeland Security Presidential Directives.
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