Formation of Chloroform and Other
Chlorinated Byproducts by Chlorination of
Triclosan-Containing Antibacterial Products
Introduction
E. Matthew Fiss, Krista L. Rule & Peter J. Vikesland
 mg  A  FQ  TC  MWCF  YCF  IR  F  ED  T
 
Inhalation al Exposure 
MWTric  V
 yr 
Virginia Polytechnic Institute and State University
Laboratory Experiments
OH
Cl
Triclosan-free soaps
Triclosan containing soaps
Time = 0 min
Time = 1 min
0.6
0.4
0.2
O
Cl
OH
OH
Cl
Cl
B
O
O
Cl
Cl
Cl
Cl
Cl
Cl
Cl
HO
OH
C
D
Cl
Cl
O
Cl
Cl
Cl
Cl
Cl
HO
E
CHCl3
Cl
Cl
Materials and Methods
General laboratory procedures, as described in the
literature (3,4), were adhered to throughout all laboratory
experiments. Free chlorine concentrations were measured
by the DPD-FAS titrimetric method and pH was measured
using a Fisher scientific model 60 pH meter.
Laboratory Experiments. To eliminate potential bias, all
products to be tested (both triclosan-containing and
triclosan-free, some in duplicate, as shown in Figure 2)
were double-blinded and code-keys were kept confidential
until completion of all experiments.
Product
Analysis.
Triclosan,
chlorophenol,
and chlorophenoxy-phenol
formation was analyzed
using solid-phase extraction
followed by derivatization
with
pentafluorobenzyl
bromide
and
GC-MS
analysis (3).
Chloroform Figure 2: A variety of common triclosancontaining and triclosan-free personal
concentrations
were care products were purchased for
experimental use.
quantified via GC-ECD.
Field Experiments. Experiments were run at the tap using
waters from Atlanta, GA and Danville, VA distribution
systems. Waters were augmented with various soap
products after allowing for sufficient time for temperature
and disinfectant concentration equilibration. Samples were
quenched at various times and transported to the lab for
byproduct quantification.
0.0
III
VI
II
IV
VII
IX
XII
0.4
Triclosan-free soaps
Triclosan containing soaps
Chloroform
DCP
TCP
0.3
0.2
0.1
0.0
III
VI
II
IV
VII
IX
XII
Byproduct yields (defined as moles of compound X
Soap Number
Figure 3: Triclosan concentration prior to chlorine
produced/moles triclosan consumed) were assessed Figure 4: Experimental yields of chloroform,
addition and after 1 minute of reaction time. No
for these same soap solutions. Chloroform yields 2,4-dichlorophenol, and 2,4,6-trichlorophenol
additional triclosan was consumed after the first
ranged from 0-0.36 mole/mole and in general, the after exposure of a given soap to free
minute. Conditions: [HOCl]i = 2.0 mg/L as Cl2,
chlorine for one minute. Conditions: [HOCl]i
[NaHCO3] = 2 mM, [Soap] = 0.25 g/L, pH = 7.0, T
chloroform yields inversely correlate with the = 2.0 mg/L as Cl2, [NaHCO3] = 2 mM, [Soap]
o
= 40 C. Error bars reflect the standard deviation
= 0.25 g/L, pH = 7.0, T = 40 oC.
chlorophenol
yields,
as
shown
in
Figure
4.
The
only
of triplicate samples.
triclosan-containing solution that failed to produce detectable amounts of chloroform (Soap IV) was also the only solution for
which intermediate chlorophenoxy-phenols were detected.
Soap Number
To better understand how product yield varies with soap identity, an additional set of experiments was conducted to quantify
chloroform formation for all sixteen unknown soap solutions. Chloroform formation over 1 minute of reaction time was quantified
while the temperature was varied from 40 to 30 oC and the free chlorine concentration was varied from 4.0 to 2.0 mg/L as Cl2
(Figure 5). The decrease in chloroform yield with a decrease in
T ric lo s a n -fre e s o a p s
T ric lo s a n c o n ta in in g s o a p s
2
0
0
free chlorine concentration, for any given soap, suggests that
variations in the free chlorine to triclosan ratio can significantly
c)
affect product yields. Overall, the variability in the product yields
150
is likely due in large part to variations in the free chlorine to
triclosan ratio, as well as the chlorine demand exerted by other
ingredients in the soaps. A reagent-spike experiment was
100
conducted to validate the dependence of product formation on
the free chlorine to triclosan ratio. As expected, chloroform
50
yields are smallest and chlorophenol yields are highest at low
free chlorine to triclosan ratios. Conversely, the opposite is the
case for samples with high free chlorine to triclosan ratios. This
0
III
V I V III X
XI XV
II
IV
V
V II IX
X II X III X IV X V I X V II
supports the hypothesis that increased chlorine demand exerted
Soap N um ber
by higher triclosan concentrations affects the triclosan
Figure 5: Chloroform produced after 1 minute of reaction time. Conditions:
chlorination product yields.
When ample free chlorine is
[NaHCO3] = 2 mM, pH = 7.0. Free chlorine concentrations are given in mg/L as
present, triclosan is readily degraded to produce chloroform and
Cl2. Error bars reflect the standard deviation of triplicate samples.
intermediate concentrations diminish.
[H O C l] i = 4 .0 m g /L , T e m p = 4 0 o C
[H O C l] i = 4 .0 m g /L , T e m p = 3 0 o C
[H O C l] i = 2 .0 m g /L , T e m p = 4 0 o C
[H O C l] i = 1 .0 m g /L , T e m p = 4 0 o C
C h lo ro fo rm (  g /L )
A
Cl
Triclosan concentrations ranged from 1.14 to 3.48 mg
triclosan/g product in the triclosan-containing PCPs
tested. Triclosan and free-chlorine concentrations were
monitored in several soap solutions over time to
examine how reaction rates were affected by elevated
temperatures. As shown in Figure 3, reactions were
extremely fast, and over half (and in 3 of 5 cases, all) of
the total triclosan consumption occurred within the first
minute of reaction time.
Yield
0.8
Triclosan (mg/L)
Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is a
widely used antibacterial agent found in many personal
hygiene products (hand soap, dish soap, body wash,
toothpaste, etc) because it exhibits antibacterial as well as
antifungal and antiviral properties (1). The widespread
presence of triclosan in PCPs means that the typical
American uses ~5 mg of triclosan each day (2). This
usage introduces a unique
potential for high levels of
triclosan to come into
contact with drinking water
disinfectants, such as free
chlorine, at the tap. Our
prior studies have shown
that pure triclosan readily
reacts with free chlorine to
form products, as shown in Figure 1: Reaction pathway for triclosan
Figure 1, via pH dependent decomposition when chlorinated. A) 5,6dichloro-2-(2,4-dichlorophenoxy)phenol,
second-order
reactions B) 4,5-dichloro-2-(2,4under
conditions dichlorophenoxy)phenol, C) 4,5,6representative of drinking trichloro-2-(2,4-dichlorophenoxy)phenol,
D) 2,4-dichlorophenol, E) 2,4,6water (3,4). This research trichlorophenol, F) chloroform
was performed in an effort to characterize the reactivity of
triclosan under higher temperature conditions simulating
household use of antimicrobial products and to estimate
the health risk associated with byproduct exposures.
Field Experiments
Field experiments were conducted in which tap water from Atlanta, GA and Danville, VA were augmented with products VI
(control), VII, IX, and XII. Atlanta tap water had an average free chlorine concentration of 1.0 mg/L as Cl2, a pH of 6.35, and a
temperature of 33 oC while Danville water maintained a 1.6 mg/L free chlorine residual with an average pH of 7.22 and a
temperature of 38 oC. In Atlanta experiments, there was a minimal loss of triclosan from soaps IX and XII, but complete
consumption for soap VII. In contrast, triclosan was completely consumed for all Danville experiments. All three chlorophenoxyphenol intermediates were detected in Atlanta water, only one dichlorinated intermediate was detected in Danville (Soap IX). In
contrast, chlorophenol yields were considerably higher in Danville water than in Atlanta samples. Additionally, significant
quantities of chloroform above the baseline level of 72.5 μg/L were produced in Danville while experiments in Atlanta water
resulted in little chloroform formation above the baseline level of 37.6 μg/L. The variations in results as compared to laboratory
experiments were attributed to chlorine demand from other dissolved constituents in the tap water (i.e. copper, iron, etc.).
References
1. Jones, R; Jampani, H; Newman, J; Lee, A. Triclosan: A review in effectiveness and safety in health care settings. Am. Jour. Infect. Control 2000, 28, 184-196.
2. McAvoy, D; Schatowitz, B; Jacob, M; Hauk, A; Eckhoff, W. Measurement of triclosan in wastewater treatment systems. Envir. Tox. Chem. 2002, 21, 1323-1329.
3. Rule, K; Ebbett, V; Vikesland, P. Formation of chloroform and chlorinated organics by free-chlorine-mediated oxidation of triclosan. ES&T, 2005, 39, 3176-3185.
4. Vikesland, P., et al. Triclosan Reactivity in Chlorinated and Chloraminated Waters. 2006, Denver, CO: American Water Works Association Research Foundation.
5. Soap and Detergent Association. Exposure and risk screening methods for consumer product ingredients. 2005.
where A = amount of soap used (12.0 g body wash and 1.7
g liquid soap per use), FQ = frequency (1.07 and 8 uses
per day for body wash and liquid soap, respectively), IR =
inhalation rate (546 L/hr), F = respirable fraction (0.257),
ED = exposure duration (10 min for showers, 1 min for
washing hands), T = time correlation factor (365 days/year),
V = effective breathing air space (2000 L), and MWCF and
MWTric are the molecular weights of chloroform and
triclosan, respectively. Using chloroform yields ranging
from 0.07-0.29 (the
100
140
Yield = 0.07 mol CF / mol triclosan
low end and overall
Yield = 0.29 mol CF / mol triclosan
120
average
yields
of
80
100
those
observed
60
experimentally), total
80
chloroform exposure
60
40
was found to range
40
from 7.5-31.1 mg/year.
20
20
Comparatively, for tap
waters with chloroform
0
0
0
20
40
60
80 100 120 140
levels at the MCL of
Chloroform in tap water (g/L)
80 μg/L, a person’s Figure 6: Estimated consumer exposure to
overall exposure could chloroform produced by the degradation of
increase by 15-40%, if antibacterial soap as predicted using the
modified model.
Solid lines illustrate the
the chloroform yields percentage of exposure resulting from the
from soap use is within antimicrobial soap use under average- and lowchloroform yield conditions, as compared to tap
the
tested
range water with between 0 and 150 g/L chloroform.
(Figure 6).
Even Dashed lines represent the total chloroform
exposure of an individual.
under conditions
where chloroform production is limited (i.e. low free
chlorine to triclosan ratios), the formation of and exposure
to chlorophenol and chlorophenoxy-phenol byproducts
may be a potential health concern.
Total Chloroform Exposure (mg/yr)
This research was performed to quantify byproduct
formation resulting from the chlorination of antibacterial
personal care products (PCPs) under conditions found in
real-world situations. Simple exposure modeling was used
to estimate an individual’s exposure to chloroform resulting
from normal PCP use.
To assess the potential health significance of these results
since chloroform can be produced in some conditions at
levels in excess of the US EPA MCL for drinking water, a
simple exposure model was utilized to estimate the
potential increase in a person’s chloroform exposure
resulting from antibacterial soap use. A model developed
by the Soap and Detergent Association (6) was modified
and used to estimate a person’s inhalational exposure:
Estimated exposure due to triclosancontaining soap use (% of total exposure)
Abstract
Potential Health Significance
Conclusions
•Triclosan from antibacterial soap is oxidized when exposed
to free chlorine, and chlorinated triclosan intermediates and
chlorophenols were detected in measurable concentrations.
•When antibacterial products are exposed to free chlorine in
conditions commonly observed when bathing and washing
dishes, chloroform can be produced at levels well above the
MCL.
•The actual concentrations of byproducts formed is largely a
function of the water chemistry, the conditions at the tap,
and the reactivity of other constituents in the soap.
•Antibacterial soap use may significantly increase an
individual’s exposure to byproducts such as chloroform,
thereby potentially increasing the risk to the person’s health.
Acknowledgments
Funding for this reseach was provided by the American
Water Works Association Research Foundation.