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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

Draft

Triclosan

Residential Exposure & Illustrative Risk Assessment

Office of Pesticide Programs

Antimicrobials Division

U.S. Environmental Protection Agency

Date: May 4, 2011
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Table of Contents

List of Tables .............................................................................................................................2

List of Figures............................................................................................................................2

EXECUTIVE SUMMARY .......................................................................................................4

1.0 INTRODUCTION ........................................................................................................6

1.1 Purpose.............................................................................................................................6

1.2 Chemical Identification....................................................................................................6

1.3 Physical/Chemical Properties ..........................................................................................6

2.0 USE INFORMATION..................................................................................................7

3.0 SUMMARY OF TOXICITY DATA............................................................................7

4.0 RESIDENTIAL AGGREGATE EXPOSURE & RISK ASSESSMENT.....................7

4.1 Summary of Registered Uses.....................................................................................7

4.2 Residential Handler Exposures..................................................................................7

4.3 Residential Post-application Exposures.....................................................................8

4.3.1 NHANES Data for Triclosan.....................................................................................8

4.3.1.1 Pharmacokinetics of Triclosan................................................................................10

4.3.1.2 Uncertainties Associated with the Dose Conversion..............................................11

4.3.2 Aggregate Risks Using NHANES ...........................................................................12

4.3.2.1 Children (6 years) to Adults.....................................................................................12

4.3.2.2 Infants ......................................................................................................................26

5.0 REFERENCES ...........................................................................................................33

List of Tables

Table 1.1. Physical/Chemical Properties of Triclosan........................................................ 6

Table 4.1. Aggregate Exposure and Risk for Triclosan (2007-2008 NHANES).............. 18

Table 4.2. Female-Specific Aggregate Exposure and Risk for Triclosan Using Geigy 

(1981) Mean and 95th%tile Urinary Volumes (2007-2008 NHANES) ........................... 19

Table 4.3. Incidental Oral Exposure and MOE for Infants Mouthing Triclosan-Treated 

Objects such as Toys......................................................................................................... 29

Table 4.4. Short- and Intermediate-term (and Long-term) Incidental Oral Post-application 

Exposures and MOEs for Infant Hand-to-mouth from Contacting Triclosan-contaminated 

House Dust........................................................................................................................ 31

Table 4.5. Aggregate Exposure and Risks for Infants 6 to 12 Month Olds...................... 32

List of Figures

Figure 1.1. Molecular Structure of Triclosan...................................................................... 6

Figure 4.1. Triclosan Excretion in Urine (taken from Sandborgh-Englund (2006)) ........ 11

Figure 4.2. Geigy Mean Urine Volume Dose Estimation: Estimated Arithmetic Mean 

(95% Confidence Interval) Triclosan Dose, by Demographic Group and NHANES 

Survey Cycle..................................................................................................................... 20

Figure 4.3. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 95th

Percentile (95% Confidence Interval) Triclosan Dose, by Demographic Group and 

NHANES Survey Cycle.................................................................................................... 21

Figure 4.4. Geigy Mean Urine Volume Dose Estimation: Estimated 95th Percentile (95% 

Confidence Interval) Triclosan Dose, by Demographic Group and NHANES Survey 

Cycle ................................................................................................................................. 22
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Figure 4.5. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 95th

Percentile (95% Confidence Interval) Triclosan Dose, by Demographic Group and 

NHANES Survey Cycle.................................................................................................... 23

Figure 4.6. Geigy Mean Urine Volume Dose Estimation: Estimated 99th Percentile (95% 

Confidence Interval) Triclosan Dose, by Demographic Group and NHANES Survey 

Cycle ................................................................................................................................. 24

Figure 4.7. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 99th

Percentile (95% Confidence Interval) Triclosan Dose, by Demographic Group and 

NHANES Survey Cycle.................................................................................................... 25
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EXECUTIVE SUMMARY 

The recently released National Health and Nutrition Examination Surveys

(NHANES) biological monitoring data on triclosan has been presented in this draft 

document to illustrate the new exposure information in context with the recently available 

toxicity data on triclosan that forms the basis of one of the case studies in the upcoming 

Science Advisory Panel (SAP) Integrated Approaches to Testing and Assessment 

Strategies: Use of New Computational and Molecular Tools. This draft document is not 

part of the SAP consultation. This draft assessment has been conducted to provide the 

general public with an update of the latest information on triclosan. 

In 2008 EPA developed a Reregistration Eligibility Decision (RED) document for 

triclosan. The 2008 RED assessment addressed the potential risks resulting from the uses

of EPA-registered triclosan in occupational settings and general population risks from all 

uses. In part, the 2008 exposure and risk assessment was based on the NHANES 

biological monitoring data from the 2003-2004 survey. Based on available data at that 

time, the Agency concluded that total exposure to triclosan from all sources did not 

present risks of concern for human health. The Agency also acknowledged scientific 

literature suggesting potential endocrine effects of triclosan and committed to examining 

the endocrine interactions of triclosan further. In addition, as new data became available 

on human exposure, that data would also be considered as well in any update to the 2008 

assessment. The EPA’s Registration Review of triclosan is scheduled to begin in 2013.

Since 2008, the Agency, in collaboration with the Office of Research and 

Development’s National Health and Environmental Effects Research Laboratory, 

conducted additional research investigations into the potential endocrine effects of 

triclosan, with an interest in identifying adverse outcome pathways that would facilitate 

characterization of precursor events for human health risk assessment. These research 

efforts have involved investigation of triclosan’s effect on the estrogen, androgen, and 

thyroid hormone systems using in vitro and in vivo testing methodologies consistent with 

the Agency’s goal under the Endocrine Disruptor Screening Program (EDSP) to screen 

pesticides, commercial chemicals, and environmental contaminants for their potential to 

disrupt the endocrine system. Research results on triclosan to date have identified 

precursor events involving the effect of triclosan on the thyroid hormone system that 

form the basis for the Agency’s proposal of an adverse outcome pathway for triclosan 

that will be presented to the FIFRA Scientific Advisory Panel in May of 2011. The case 

study document is available on the EPA’s public docket at regulations.gov using docket 

number EPA–HQ–OPP–2011–0284.

Toxicity studies that form the basis of the oral endpoint used in this draft risk 

assessment are: 

• Zorrilla, LM, Gibson EK, Jeffay SC, Crofton KM, Setzer WR, Cooper RL, Stoker 

TE. (2009) The effects of triclosan on puberty and thyroid hormones in male 

Wistar rats. Toxicol. Sci. 107 (1): 56-64.

• Stoker, T.E., Gibson, E.K., Zorrilla, L.M. (2010) Triclosan exposure modulates 
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estrogen-dependent responses in the female Wistar rat. Toxicol. Sci. 177(1):45-

53.

In these studies, triclosan (99.5% pure) was administered by oral gavage commencing 

on postnatal day (PND) 21 in both sexes and continuing until PND 41 in the female and 

PND 53 in the male. Males were dosed with triclosan at 3, 30, 100, 200 or 300 

mg/kg/day and the females were dosed with triclosan at 9.375, 37.5, 75 or 150 

mg/kg/day. These male and female pubertal screening protocols examined a variety of 

reproductive endpoints including an in life estimate of pubescence (vaginal opening in 

the female and preputial separation in the male) in addition to measurements of serum 

thyroxine (T4), thyroid stimulating hormone (TSH) and thyroid histology. The lowest 

dose effect observed in all three studies was a decrease in serum T4.

Using the serum T4 decrease as the endpoint, BMD modeling using EPA's Bench 

Mark Dose Software (BMDS) was performed to determine the benchmark dose estimate 

(BMD) and lower limit estimate (BMDL) using the T4 data from these studies. Initial 

statistical modeling demonstrated no significant difference between studies for the effects 

of triclosan on T4. Therefore, benchmark dose modeling was conducted simultaneously 

for three data sets. The bench mark response (BMR) was set at both 10 and 20% using 

an unconstrained Hill estimate to fit the data. Using the 10% BMR, the BMD was 10.37 

mg/kg and the BMDL was 3.47. Using the 20% BMR in the same model, the BMD was 

19.05 mg/kg and the BMDL was 8.07 mg/kg. For a detailed discussion of the 

toxicological effects, bench mark dose, and uncertainty factor selection the reader is 

referred to the background information on the case study (triclosan) being provided for 

the EPA’s Scientific Advisory Panel (SAP) May 2011 meeting

(http://www.epa.gov/scipoly/sap/meetings/2011/052411meeting.html).

The resulting draft aggregate risks presented herein include exposures to both 

EPA- and FDA-regulated uses. The results of the assessment indicate that the exposures 

do not exceed the level-of-concern for effects on the thyroid hormone system based on 

the recent toxicity data used in the case study. 
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1.0 INTRODUCTION

1.1 Purpose

In this draft document, EPA’s Antimicrobials Division (AD) presents the results 

of its review of the potential human health effects of the aggregate residential exposure to 

triclosan (5-chloro-2-(2,4 dichlorophenoxy) phenol). This draft assessment has been

developed to communicate the updated general population monitoring levels of triclosan 

in urine from newly released NHANES data to illustrate these new data in a risk context.

1.2 Chemical Identification

Triclosan (5-Chloro-2-(2,4-dichlorophenoxy)phenol) was first registered with the 

EPA on June 19, 1969. Triclosan is a diphenyl ether derivative. The CAS number is 

3380-34-5 and the molecular structure is provided below in Figure 1.1:

Figure 1.1 Molecular Structure of Triclosan

1.3 Physical/Chemical Properties

Table 1.1 shows physical/chemical characteristics that have been reported for 

triclosan.

Table 1.1 Physical/Chemical Properties of Triclosan

Parameter Triclosan

Molecular Weight 290

Density 1.55E3 kg/m3 at 22  ̊C

Boiling Point Solid

Water Solubility 12 ppm

Vapor Pressure 5.2E-6 mm Hg at 25  ̊C
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2.0 USE INFORMATION

Triclosan is used as a bacteriostat, fungistat, mildewstat, and deodorizer. The 

products containing triclosan as the active ingredient (a.i) are formulated as ready-to-use, 

pelleted/tableted, emulsifiable concentrate, soluble concentrate, and impregnated 

materials. Concentrations of triclosan in these products range widely from 0.69% to 

≥99%. 

The Agency determines potential exposures to handlers of the product by 

identifying exposure scenarios from the various application methods that are plausible, 

given the label uses. Based on a review of product labels, triclosan is the active 

ingredient in products used during manufacturing of textiles and fabrics, plastics, etc. 

Additionally, FDA uses of triclosan include products such as hand soaps, deodorants, and 

toothpaste. Although the FDA uses are out of the scope of EPA’s jurisdiction, exposures 

to these products are included in the overall aggregate assessment and cannot be 

separately presented using the NHANES general population monitoring data. 

3.0 SUMMARY OF TOXICITY DATA

Triclosan has been studied for its effects on the thyroid and estrogen hormone 

systems in experimental animals (Crofton et al., 2007; Zorilla et al., 2009; Stoker et al., 

2010). These data indicate an effect on thyroxine levels in rats through a mechanism 

involving induction of biotransformation enzymes resulting in increased clearance of 

thyroxine from serum, and a potentiating effect on the action of estrogen in the presence 

of triclosan. The assessment herein is based on these recent data. For a detailed 

discussion of the toxicological effects, bench mark dose, and uncertainty factor selection 

the reader is referred to the case study (triclosan) being provided for the EPA’s 

consultation with the Scientific Advisory Panel’s (SAP) Integrated Approaches to Testing 

and Assessment Strategies: Use of New Computational and Molecular Tools May 2011 

meeting http://www.epa.gov/scipoly/sap/meetings/2011/052411meeting.html).

4.0 RESIDENTIAL AGGREGATE EXPOSURE & RISK ASSESSMENT 

4.1 Summary of Registered Uses

There are no EPA registered products containing triclosan that can be applied 

directly by the homeowner. Articles treated with triclosan as a bacteriostat in 

occupational settings (e.g., EPA Reg. No. 70404-5) may have the potential for postapplication residential exposure. Triclosan-treated articles that may routinely be used in 

the residential market include, but are not limited to, material preservative uses in 

mattresses, clothing, bibs, tooth brush bristles, plastic toys, garbage bags, paper, 

playground equipment, sponges, furniture, footwear, etc. 

4.2 Residential Handler Exposures

The paint use was not eligible for re-registration during the RED process. 
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Therefore, in the future there will be no residential handler uses of triclosan products.

4.3 Residential Post-application Exposures

Based on a review of EPA-registered product labels, triclosan is the active 

ingredient in textiles and fabrics (e.g., mattresses and clothing/bibs) and plastic products 

(e.g., toys, cutting boards, etc). Exposures also include those uses where there is the 

possibility of indirect food migration, including paper/pulp use, use in ice-making 

equipment, adhesives, cutting boards, and counter tops as well use in conveyer belts. In 

addition to EPA-regulated uses, the post application assessment also includes an 

aggregate assessment of the FDA uses such as toothpaste, hand soaps, and deodorants. 

This assessment includes both EPA- and FDA-registered uses because of the biological 

monitoring methodology used to collect the samples from the general population does not 

allow us to separate the contribution of individual products to total exposure. 

The National Health and Nutrition Examination Surveys (NHANES) biological 

monitoring data are available for triclosan to assess aggregate exposure and risk. For the 

2008 RED, NHANES data were available for triclosan only for the 2003-2004 survey

cycle. Subsequently, CDC has released the triclosan results for the 2005-2006 and 2007-

2008 survey years. The review below presents a comparison of the three NHANES 

triclosan data sets. 

EPA estimated triclosan exposure using nationally representative biomonitoring 

data available through NHANES. This approach was adopted by EPA because of the 

need to assess aggregate exposure that is expected from co-use of different consumer 

products containing triclosan. The NHANES monitoring data provides the most 

representative measure of aggregate exposures to daily use products. In the case of 

triclosan, population-based biological monitoring data are available to assess the cooccurrence of uses to develop an aggregate exposure assessment for ages 6 years and 

older. The population-based biological monitoring data are the best predictor of 

aggregate exposure because not only are the data triclosan specific, they are also based on 

actual consumer use of the various triclosan products as they co-occur in practice and 

would ostensibly include drinking water exposures as well. 

Although the aggregate exposure/risk assessment presented herein using the 

NHANES data provides a holistic view of the exposure to all triclosan-treated products, it 

does not include exposures to children under the age of 6 years old. Children under the 

age of 6 years exhibit unique activities that do not occur at older ages. Therefore, a 

separate estimate for children under 6 years old has been included. Finally, dermal and 

inhalation route-specific assessments did not change since the 2008 RED and are 

therefore not repeated herein. The reader is referred to the 2008 RED for those 

assessments.

4.3.1 NHANES Data for Triclosan

The National Health and Nutrition Examination Surveys (NHANES) are a series 
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of US national surveys of the health and nutrition status of the non-institutionalized 

civilian population conducted by the Centers for Disease Control and Prevention. As part 

of NHANES, urinary concentrations (μg/L) of triclosan (2,4,4’-trichloro-2’-

hydroxydiphenyl ether) were measured on a random sample of participants of ages 6 and 

over as part of a complex multi-stage, stratified survey that is nationally representative. 

These measurements represent concentrations in spot urine samples. The dose 

(mg/kg/day) corresponding to the urine concentration was not measured or estimated by 

NHANES. The NHANES urinary metabolite concentration data collection efforts were 

not designed to directly determine the dose and CDC has not reported dose estimates for 

triclosan based on NHANES measurement data. The NHANES data can be found on the 

NHANES website: www.cdc.gov/nchs/nhanes.htm NHANES data for triclosan are now 

available for the 2005-2006 and 2007-2008 surveys.

EPA evaluates health effects in terms of toxicity endpoints that represent an 

exposure level in mg or μg per kilogram body weight that is not expected to be associated 

with adverse health effects. The conversion of measured spot urine concentrations to 

daily doses can be difficult because of variable dilution caused by wide fluctuations in 

fluid intake and excretion. Dose calculation is also difficult because there is no way to 

determine from the NHANES data from what route of exposure (i.e., oral, dermal, 

inhalation) and when (i.e., duration and time interval prior to measurement) the exposure 

to triclosan occurred, and because of uncertainty and variability in the absorption, 

distribution, metabolism, and excretion (ADME) parameters. If NHANES collected total 

daily urine excretion for each participant, then that participant’s dose could be more 

accurately estimated by multiplying the triclosan concentration in the urine by the total 

daily urine volume and then dividing by the body weight. However, NHANES only 

collected spot urine samples so that total urine volume was not measured. 

In the absence of total urine volume data, various methods were proposed in the 

2008 RED to estimate the dose from the measured spot urine concentration. The 

methods have been categorized into two main groups: one that uses measured pesticide 

concentrations in urine directly and the other that standardizes urinary concentrations on 

the basis of creatinine, a by-product of metabolism. There is some debate on whether 

creatinine excretion is less variable (i.e., more consistent within an individual) than 

urinary output. Therefore, in 2008 the results of both methods were presented. The dose 

conversion methods used in the 2008 RED are summarized below: 

• Mage et al. (2004, 2007) use the estimated daily creatinine excretion for specific 

individuals based on their anthropometric measurements and demographic 

characteristics (e.g, age, sex, race (Black, non-Hispanic or not), height, weight, 

and obesity (based on the BMI)). The triclosan concentration is divided by the 

creatinine concentration in the urine, multiplied by the estimated daily creatinine 

excretion in μg/day specific to the individual being considered, and divided by the 

body weight. 

• Schafer et al. (2004) use the estimated daily urine excretion in L/day and the 

average body weight for a demographic group; the triclosan concentration is 
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multiplied by the daily urine excretion in L/day, and divided by the average body 

weight. Because the raw data were available in NHANES, actual (measured) 

body weights of subjects were used instead of average body weights as described 

by Schafer et al. (2004). 

• The EPA Office of Research and Development (ORD) does not currently 

recommend any single approach for converting spot urine concentration to a dose. 

However, the approach used by some ORD researchers is to use the estimated 

daily urine excretion in L/kg-day (as opposed to L/day above) for a demographic 

group; the triclosan urinary concentration is multiplied by the estimated daily 

urine excretion in L/kg-day. Two variations of this approach are used. Both 

mean and the 95th%ile urine volumes from Geigy (1981) were used in this 

method.

Detailed procedures and assumptions used in the 2008 RED assessment to convert 

spot urine concentrations into dose to assess the triclosan aggregate risks were provided 

by Cohen (2008). Cohen (2008) provided the dose conversion from spot urine samples 

leaving the correction for the pharmacokinetics of triclosan to be done within the risk 

assessment for the 2008 RED.

The results presented in the 2008 RED indicated that the 3 methods above were 

very similar and that the results of the Geigy (1981) method were the most conservative

(i.e., producing the higher exposure estimates). In this revised assessment, only the 

results using the Geigy (1981) method are presented.

Krishnan et al (2010) published an alternative to the methods described above in 

assessing triclosan by using a biomonitoring equivalent (BE) approach. However, 

Krishnan et al (2010) were not able to include the current toxicological endpoint used

herein for their review of triclosan BEs because it was not available at the time of 

publication. The BE for the BMDL20 of 8.07 mg/kg/day / 30x uncertainty factor is 5.8 

mg/L (or 7.4 mg/g creatinine).

4.3.1.1 Pharmacokinetics of Triclosan 

A correction factor to account for the disposition of triclosan, derived from the 

data of Sandborgh-Englund (2006) was applied to the biological (urine) monitoring data 

provided used in this assessment. Sandborgh-Englund (2006) dosed 10 subjects (5M/5F) 

ranging from 26 to 42 years of age with a single oral dose of 4 mg of triclosan in 

mouthwash solution. Pre-exposure monitoring to establish baseline exposure levels was 

also determined. Results indicate that urinary excretion among individuals is variable for 

triclosan. Urinary excretion ranged from 24 to 83 percent (median of 54 percent) of the 

administered dose of triclosan in urine in 4 days. The data also indicate that the majority 

of urinary excretion occurred within 24 hours as illustrated in Figure 4.1. Therefore, 54 

percent excretion, corrected for baseline exposures, was used by EPA in this assessment 

to convert the urine concentrations from NHANES to a dose using estimated 24 hour 

urine void volumes. The conversion is facilitated by the linear excretion kinetics 
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observed for triclosan in this study. Based on the above, the pharmacokinetic correction 

used to estimate the total triclosan dose (i.e., corrected for triclosan excretion) equals the 

urinary concentration derived dose (mg/kg/day) divided by the median value of the 

triclosan excretion in urine (i.e., 0.54). 

Figure 4.1. Triclosan Excretion in Urine (taken from Sandborgh-Englund 

(2006))

4.3.1.2 Uncertainties Associated with the Dose Conversion

Several uncertainties exist in the aggregate assessment for triclosan that arise from 

using the biological monitoring using spot urine samples from NHANES. Therefore, 

EPA used conservative assumptions to err on the side of overestimating the potential 

dose. The following uncertainties and data limitations are noted for the aggregate 

assessment:

• For simplicity (and lack of data), absorption, distribution, metabolism, and

elimination (ADME) pharmacokinetic parameters are assumed to be similar for

all individuals within the NHANES study and are constant within individuals over 

time. 

• Sandborgh-Englund (2006) reported urinary excretion over 4 days post dose. 

From the graphical presentation of the data (raw data not reported) the profile of 

urinary excretion of triclosan indicates that the results at 24 hours are similar to 

those at 4 days. The urinary excretion half life for triclosan is reported in the text 

of the study (not taken from the graph) as 11 hours.

• The urinary excretion of triclosan presented in Sandborgh-Englund (2006) is 

highly variable (ranging from 24 to 83 percent). The median value reported of 

54% urinary excretion has been used by EPA in the dose estimates. Krishnan 

(2010) indicates that ... “The pharmacokinetic data, specifically plasma 

clearance, obtained from ten volunteers (Sandorgh-Englund et al., 2006) is 

considered to be fairly robust, given the additional support from the literature 

regarding steady-state and inter-individual variability.” 
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• NHANES urinary metabolite concentration data are not collected in a way

amenable to directly determining the dose, and CDC has not reported dose 

estimates for triclosan based on NHANES measurement data. In order to 

determine how sensitive the estimated dose was to urinary excretion volume, one 

of the dose conversion methods (Geigy (1981) 95% urine volume upper bound 

estimate) is used to estimate a 24 hour urinary excretion volume for all 

individuals in the NHANES data set. This is a bounding estimate that leads to an 

overestimate of the estimated dose.

• Dose calculation is also difficult because there is no way to determine from the 

NHANES data from what route of exposure (i.e., oral, dermal, inhalation) and 

when (i.e., duration and time interval prior to measurement) the exposure to 

triclosan occurred. There is no longitudinal sampling for NHANES and no

personal diaries to determine potential sources of exposure and by which route.

However, the unique aspects of triclosan -- short half life in urine and widespread 

daily use of triclosan products – lend themselves to represent a range of short- and

long-term measurements of exposure from a nationally representative population 

sample such as NHANES. The critical assumption for justifying the dose 

estimation approach and that it represents a range of exposure durations is that 

study participants within NHANES are likely to be at steady state with respect to 

their elimination of triclosan in urine. This assumption is bolstered by the 

following:

o A high percentage (~82 percent) of the population has detectable levels of 

triclosan in their urine; given the short half-life, this suggests that exposure 

occurs frequently; and

o Triclosan is found in a number of consumer products that individuals 

would conceivably contact multiple times per day (e.g., hand soap, 

toothpaste, treated textiles/plastics), it seems reasonable to assume 

individuals are at steady-state condition. 

Future refinements to using the NHANES data for assessing triclosan should 

focus on refining these parameters.

4.3.2 Aggregate Risks Using NHANES

4.3.2.1 Children (6 years) to Adults

The NHANES results are believed to be representative of a range of short to 

chronic exposures to children and adults because of the relatively short half-life of 

triclosan in urine (i.e., 11 hours) and the often daily use of triclosan products such as 

hand soaps and tooth paste. The upper range of exposures is important because of the 

uncertainties in converting the spot urine concentrations to a dose; because the 

pharmacokinetic data appears to be highly variable among individuals for triclosan; and 

because the use of triclosan-treated products by the NHANES population is unknown. 

Given the uncertainties in aggregating screening-level single use exposure estimates and 

assumptions on co-occurrence of uses, the NHANES data are viewed to be a reasonable 

data set to use for predicting aggregate risks in a regulatory context.
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Demographic Subgroups:

The aggregate assessment is presented for the age groups and subpopulations

listed below. While the point of departure (PoD) for triclosan is based on thyroid effects 

and would apply to women of childbearing age and young children (birth to age ~6), it is 

recognized that the triclosan RfD may be conservative and not relevant to other 

population subgroups. 

• All age groups;

• Ages 6-11;

• Ages 12-19

• Ages 20-59

• Ages >=60

• Male

• Females

• Mexican-American

• White, non-Hispanic

• Black, non-Hispanic

A separate analysis of the NHANES data set for females is also included using the 

following subgroups:

• Confirmed non-pregnant (females)

• Confirmed pregnant

• Females 13-49

• Females 6-12

• Females 50+

Uncertainties and Limitations in the Aggregate Assessment:

Many assumptions are used at each stage of the development of risk estimates. 

These uncertainties must be acknowledged for transparency so the reader can understand 

the bounding nature of the risk estimates. The uncertainties range from the selection of 

the hazard endpoint to the dose conversion to the reporting and interpretation of the risk 

estimates. Below is an acknowledgement of the identified uncertainties and limitations 

that need to be considered in interpreting the presented exposures and risks:

• The uncertainties of the spot urine to dose conversion are discussed in Section 

4.3.1.2 above. Taken together, these assumptions tend to influence the resulting 

dose estimates to be on the high end.

• The dose levels represent very conservative estimates (e.g., the 24-hour urine 

volume used to estimate dose for one of the two urine-to-dose conversion 

methods presented is at the 95th percentile) and it is unknown if actual individuals

are exposed at the dose levels at the higher percentiles/confidence intervals 
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presented. Because of smaller sample sizes, estimates for demographic subgroups 

are less reliable than estimates for all persons. The CDC National Exposure 

Report (CDC 2009) does not include percentile values above the 95th percentile. 

The estimates and confidence intervals for the 99th percentile reported herein may 

be less reliable than estimates and confidence intervals for the 90th and 95th 

percentiles. The 99th percentiles are reported to illustrate the conservative nature 

of the assessment and the fact that a single dose cannot be ruled out to cause these 

toxicological effects.

• Triclosan spot urine concentrations in NHANES are believed to represent steady 

state exposure based on the short half life, high frequency of detectable triclosan 

in urine, and because triclosan is used in daily use products; however it is 

important to note that the steady-state argument is most likely relevant at the 

central tendency of the reported NHANES data. The steady-state assumption may 

be less likely at both extremes of the overall distribution of urinary triclosan 

levels in NHANES. At the upper end of the distribution it is unknown if the 

person’s behavior/activity leads to higher exposures on a daily basis or if the 

concentrations were influenced by a single event such as swallowing tooth paste 

prior to sampling. In the latter case, the use of the 95th percentile urine volume in 

the dose conversion further exaggerates this flaw in dose conversion (and 

overestimates the dose/risk). Krishnan et al (2010) provides a similar caveat: 

“For short-lived compounds such as triclosan, an exceedance of the 

corresponding BE value in a single urine sample may or may not reflect 

continuing elevated exposure. As demonstrated in the limited available datasets 

and based on the kinetics of urinary elimination, spot urinary concentrations may 

vary substantially both within and across days in an individual. Thus, occasional 

exceedances of the BE value in individuals in cross-sectional studies do not imply 

that adverse health effects are likely to occur...”. The “BE” value is the 

biomonitoring equivalent that can be explained, in-short, as the reference dose 

(RfD) expressed as a back-calculation of the concentration in urine (e.g., mg/L). 

The reader is referred to Krishnan et al (2010), Hays et al (2007 and 2008), and 

LaKind et al (2008) for a more thorough explanation of the BE. It is important to 

note that at the time of the Krishnan et al (2010) publication the toxicological 

endpoint in this assessment was not available to the authors (BE has been 

calculated and presented above in Section 4.3.1). 

• Although the effects seen in the point of departure (PoD) for triclosan were not

measured after a single dose (i.e., the study was designed as a repeat dose testing),

this effect cannot be ruled out for a 1-day dosing. However, a single dose would 

not likely be expected to impact tissue function at environmental exposures due to 

the buffering of thyroid hormone concentrations by homeostatic mechanisms. 

The PoD for this current assessment is considered protective of long-term 

exposures because the effects observed in a short-term dosing study measuring 

thyroid hormone changes are expected to occur within the short-term duration for 

a chemical such as triclosan which is rapidly excreted in the urine (11 hour 

urinary half life, Sandborgh-Englund 2006).
Page 15 of 34

• In general, it is preferable to set a single RfD to cover the whole population, in 

particular for risk management purposes. It is important to ensure that any RfD 

established is adequate to protect children and the embryo/fetus from possible in 

utero effects. While the point of departure (PoD) for triclosan is based on thyroid 

effects and would apply to women of childbearing age and young children (birth 

to age ~6), it is recognized that the triclosan RfD may be conservative and not 

relevant to other population subgroups. Although the PoD for developmental 

thyroid effects was applied to other population subgroups in this illustrative risk 

assessment, those situations did not result in any exposures exceeding the levelof-concern. In situations in which a developmental endpoint is used for the whole 

population and exceedances are found in subgroups for which the endpoint is not 

relevant, it would be important to set a second value based on another nondevelopmental endpoint. Note: Female-specific subpopulations (including 

pregnancy) are also provided herein.

Summary of Results from NHANES 2007-2008:

The NHANES data show that the majority of the US population has detectable 

levels of total (free plus conjugated) triclosan. Detectable levels of triclosan were found 

in 82 percent of the US population in the 2007-2008 survey. 

Table 4.1 provides the arithmetic mean as well as the 95th and 99th percentiles of 

the (1) spot urine concentration to dose conversion prior to correcting for the 54% 

triclosan urinary excretion (in units of μg/kg/day); (2) the pharmacokinetic 54% corrected 

daily dose converted to units of mg/kg/day; and (3) the margin of exposure (MOE). 

Table 4.2 provides the same analysis for the female-specific subpopulations. The Geigy 

(1981) dose conversion methods used in this risk characterization include risk estimates

calculated using both the mean daily urinary excretion volume and the 95th percentile

daily urinary excretion volume. The use of the daily urinary excretion volumes is 

necessary to extrapolate to a daily dose because the NHANES data represent only a 

single spot urine collection sample. The inclusion of the 95th percentile urinary excretion 

volume provides an upper bound estimate as a conservative assumption.

Based on the results at the mean, 95th, and 99th percentiles of the dose (using both 

the mean and 95th percentile daily urinary excretion volumes), the estimated aggregate 

risks from all triclosan uses (EPA and FDA) indicate that the dose levels do not exceed 

the BMDL20 using a target MOE of 30. The MOEs for all of the age groups and 

subpopulations as well as the separate assessment for the female-specific subgroups are 

summarized as follows:

• The mean MOEs range from 1,900 to 4,400 assuming the mean daily urinary 

excretion volume and from 1,200 to 2,700 assuming the 95th percentile

• The MOEs at the 95th percentile of the dose range from 330 to 870 assuming the 

daily 

urinary excretion volume. 

mean daily urinary excretion volume and from 230 to 540 assuming the 95th
Page 16 of 34

percentile

• The MOEs at the 99th percentile of the dose range from 150 to 340 assuming the 

daily urinary excretion volume.

mean daily urinary excretion volume and from 90 to 280 assuming the 95th

percentile daily urinary excretion volume.

The assumptions provided herein leave room for further refinement of the 

estimated dose levels and are not intended to be viewed as a precedent for other 

assessments. In summary, even with the considerable uncertainties in converting spot 

urine concentration to dose and the uncertainties associated with the 99th percentile for 

this data set, the NHANES data as analyzed for triclosan characterizes the draft aggregate 

risk assessment as a conservative bounding estimate that does not exceed the level-ofconcern (i.e., BMDL20 of 8.07 mg/kg/day with an uncertainty factor of 30). 

Comparisons of Aggregate Dose & Risk From NHANES ‘03-‘04, ’05-’06, ’07-‘08 

USEPA (2010) provides an analysis of the NHANES urinary concentrations from 

sample survey years 2003-2004, 2005-2006, and 2007-2007 converted to dose. 

Detectable levels of triclosan were found in 74.6, 80.8, and 81.5 percent of the US 

population in the 2003-2004, 2005-2006, and 2007-2008 surveys, respectively.

The comparisons of the results from the NHANES data sets are graphically 

depicted below in Figures 4.2 through 4.7. The figures illustrate the following:

• Figure 4.2 – Arithmetic mean dose based on the mean daily urinary excretion 

volume;

• Figure 4.3 -- Arithmetic mean dose based on the 95th % daily urinary excretion 

volume;

• Figure 4.4 – 95th percentile dose based on the mean daily urinary excretion 

volume;

• Figure 4.5 – 95th percentile dose based on the 95th % daily urinary excretion 

volume;

• Figure 4.6 – 99th percentile dose based on the mean daily urinary excretion 

volume; and

• Figure 4.7 -- 99th percentile dose based on the 95th % daily urinary excretion 

volume

Each figure contains the following information:

• NHANES dose levels corrected for urinary excretion (i.e., 54% of triclosan is 

excreted in the urine) for survey years 2003-2004, 2005-2006, and 2007-2008;

• Results for the age and demographic groups provided in Section 4.3.2.1 above;

• Error bars for the lower and upper 95th% confidence intervals (CI);

• The level of concern or reference dose (RfD) is depicted as a solid horizontal line 

(i.e., BMDL20 8 mg/kg/day / 30x uncertainty factor = 0.27 mg/kg/day); and

• The 95th percent lower confidence limit of the bench mark dose (i.e., BMDL10 of 

3.5 mg/kg/day) is divided by the 30x uncertainty factor to represent the lower 
Page 17 of 34

limit of the RfD (i.e., 3.5 mg/kg/day / 30x uncertainty factor = 0.12 mg/kg/day). 

This value is depicted as a dotted horizontal line in the figures. 

The results illustrated in the figures indicate that neither the means, 95th, nor the 

99th percentiles or their upper 95th percent confidence intervals of the doses exceed the 

level of concern (i.e., RfD of 0.27 mg/kg/day) for any age or demographic group for any 

of the survey years.

The lower limit of the bench mark dose is not exceeded at the means, 95th, or 99th

percentiles of the doses for any age or demographic group for any of the survey years. 

The upper confidence intervals on the 99th percentile using the mean daily urinary 

excretion volume for any age or demographic group for any of the survey years do not 

exceed the lower limit of the bench mark dose. However, the 2005-2006 NHANES data 

indicate that for two groups the 95th percent upper confidence interval on the 99th

percentile using the mean daily urinary volume to estimate dose is at the lower limit of 

the bench mark dose (i.e., Figure 4.6). Finally, the lower limit of the bench mark dose is 

exceeded by several of the groups for various survey years (i.e., Figure 4.7). The dose 

levels in Figure 4.7 represent a very conservative estimate. The upper confidence limits 

of the 99th percentiles in Figure 4.7 are reported to illustrate the conservative nature of the 

assessment and that those bounding estimates have not exceeded the level-of-concern.
Page 18 of 34

Table 4.1. Aggregate Exposure and Risk for Triclosan (2007-2008 NHANES)

Mean 95th Percentile 99th Percentile

Group

Dose, 

uncorrecte

d 

(μg/kg/day

)†

Dose, 

corrected 

(mg/kg/day)‡

MOE

*

Dose, 

uncorrect

ed 

(ug/kg/da

y)†

Dose, 

corrected 

(mg/kg/da

y)‡

MO

E*

Dose, 

uncorrect

ed 

(ug/kg/da

y)†

Dose, 

corrected 

(mg/kg/da

y)‡

MO

E*

Dose Conversion Method: Geigy (1981) Using the Mean Urinary Volume

All 1.57 0.0029 2755 7.8 0.0144 554 23.9 0.044 180

6-11 1.35 0.0025 3206 7.4 0.0137 584 22.5 0.042 192

12-19 2.04 0.0038 2119 8.8 0.0163 491 29.1 0.054 148

20-59 1.58 0.0029 2731 8.0 0.0148 540 24.4 0.045 177

>= 60 1.30 0.0024 3314 6.8 0.0126 635 15.3 0.028 282

Male 1.57 0.0029 2750 7.8 0.0144 554 21.5 0.040 201

Female 1.56 0.0029 2761 7.5 0.0139 576 25.4 0.047 170

MexicanAmerican 1.85 0.0034 2336 10.1 0.0187 428 25.0 0.046 173

White, NonHispanic 1.40 0.0026 3080 7.3 0.0135 592 21.5 0.040 201

Black, NonHispanic 1.30 0.0024 3313 6.4 0.0119 675 21.2 0.039 203

Dose Conversion Method: Geigy (1981) Using the 95th Percentile Urinary Volume

All 2.44 0.0045 1772 12.0 0.0222 360 36.9 0.068 117

6-11 1.90 0.0035 2270 10.8 0.0200 400 32.8 0.061 132

12-19 3.13 0.0058 1382 13.3 0.0246 325 47.1 0.087 92

20-59 2.49 0.0046 1734 12.9 0.0239 335 37.5 0.069 115

>= 60 2.04 0.0038 2113 10.9 0.0202 396 24.8 0.046 174

Male 2.39 0.0044 1805 12.0 0.0222 360 33.0 0.061 131

Female 2.48 0.0046 1742 12.0 0.0222 360 41.0 0.076 105

MexicanAmerican 2.84 0.0053 1519 15.5 0.0287 279 38.4 0.071 112

White, NonHispanic 2.19 0.0040 1976 11.1 0.0206 389 32.8 0.061 132

Black, NonHispanic 2.04 0.0038 2121 10.4 0.0193 415 32.6 0.060 132

† Dose, uncorrected (ug/kg/day) = NHANES 2007-2008 data set of spot urine sampling converted to dose, but not corrected for 

urinary excretion of triclosan.

‡ Dose, Corrected (mg/kg/day) = (Dose, uncorrected (ug/kg/day) / 0.54 urinary excretion of unconjugated triclosan (i.e., 54%)) /

1000 ug/mg unit conversion

* MOE = BMDL20 (mg/kg/day) / Dose, Corrected (mg/kg/day); where BMDL20 is 8 mg/kg/day; Target MOE = 30.
Page 19 of 34

Table 4.2. Female-Specific Aggregate Exposure and Risk for Triclosan Using Geigy (1981)

Mean and 95th%tile Urinary Volumes (2007-2008 NHANES)

Group

Mean 95th Percentile 99th Percentile

Dose, uncorrected Dose, corrected

MOE

Dose, uncorrected Dose, corrected

MOE

Dose, uncorrected Dose, corrected

(ug/kg/day) (mg/kg/day) (ug/kg/day) (mg/kg/day) (ug/kg/day) (mg/kg/day) MOE

Dose Conversion Method: Geigy (1981) Using the Mean Urinary Volume

Confirmed Non Pregnant (20-44 Year Old Females) 1.8 0.00335 2386 9.6 0.0178 450 29.8 0.0551 145

Confirmed Pregnant (20-44 Year Old Females) 2.3 0.00429 1863 9.5 0.0176 454 9.5 0.0176 454

13-49 Year Old Females 1.9 0.00348 2297 9.5 0.0176 454 29.8 0.0551 145

6-12 Year Old Females 1.8 0.00332 2409 13.2 0.0244 329 22.5 0.0416 192

50 and Above Year Old Females 1.0 0.00180 4432 5.0 0.0092 871 12.8 0.0237 337

Dose Conversion Method: Geigy (1981) Using the 95th Percentile Urinary Volume

Confirmed Non Pregnant (20-44 Year Old Females) 2.9 0.00542 1477 15.5 0.0287 279 48.1 0.0890 90

Confirmed Pregnant (20-44 Year Old Females) 3.7 0.00694 1153 15.4 0.0284 281 15.4 0.0284 281

13-49 Year Old Females 3.0 0.00558 1434 15.4 0.0284 281 48.1 0.0890 90

6-12 Year Old Females 2.5 0.00469 1707 19.2 0.0356 225 32.8 0.0608 132

50 and Above Year Old Females 1.6 0.00292 2743 8.0 0.0148 539 20.7 0.0383 209

† Dose, uncorrected (ug/kg/day) = NHANES 2007-2008 data set of spot urine sampling converted to dose, but not corrected for urinary excretion of triclosan.

‡ Dose, Corrected (mg/kg/day) = (Dose, uncorrected (ug/kg/day) / 0.54 urinary excretion of unconjugated triclosan (i.e., 54%)) / 1000 ug/mg unit conversion

* MOE = BMDL20 (mg/kg/day) / Dose, Corrected (mg/kg/day); where BMDL20 is 8 mg/kg/day; Target MOE = 30.
Page 20 of 34

Figure 4.2. Geigy Mean Urine Volume Dose Estimation: Estimated Arithmetic Mean (95% Confidence Interval) Triclosan Dose, by 

Demographic Group and NHANES Survey Cycle
Page 21 of 34

Figure 4.3. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 95th Percentile (95% Confidence Interval) Triclosan 

Dose, by Demographic Group and NHANES Survey Cycle
Page 22 of 34

Figure 4.4. Geigy Mean Urine Volume Dose Estimation: Estimated 95th Percentile (95% Confidence Interval) Triclosan Dose, by 

Demographic Group and NHANES Survey Cycle
Page 23 of 34

Figure 4.5. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 95th Percentile (95% Confidence Interval) Triclosan Dose, 

by Demographic Group and NHANES Survey Cycle
Page 24 of 34

Figure 4.6. Geigy Mean Urine Volume Dose Estimation: Estimated 99th Percentile (95% Confidence Interval) Triclosan Dose, by 

Demographic Group and NHANES Survey Cycle
Page 25 of 34

Figure 4.7. Geigy Upper Bound Urine Volume Dose Estimation: Estimated 99th Percentile (95% Confidence Interval) Triclosan Dose, 

by Demographic Group and NHANES Survey Cycle
Page 26 of 34

4.3.2.2 Infants

While NHANES data are measured exposures that represent the real world cooccurrence of triclosan-treated products for those age groups which were surveyed, it is 

necessary to use screening-level deterministic assessments and to make assumptions of 

potential co-occurrence of triclosan-treated products for children younger than 6 years old. 

The USEPA (2005), an internally and externally scientific peer reviewed document, 

provides the basis of the age group selection: “This document recommends a set of age 

groupings based on current understanding of differences in lifestage behavior and anatomy 

and physiology that can serve as a starting set for consideration by Agency risk assessors 

and researchers. In specific situations, it is recognized that exposure factors data may not 

be available for many of the recommended age groupings or that a specific age group may 

not need to be the subject of a particular assessment, so flexibility and professional 

judgment are essential in applying these generic age groupings.” One age group was 

selected from this EPA reference to represent behavioral activities of children younger than 

6 years old (i.e., this age group is not sampled by NHANES) that are potentially exposed to 

triclosan-treated products.

Infants in the 6 to 12 month old age group has been selected for this assessment to 

represent the high end of exposure activities of children less than six years old to triclosantreated products. This age group is considered the high end of exposure based on the 

characteristics of behavioral development discussed in Table 2 presented in USEPA (2005) 

and the likelihood of these activities co-occurring. USEPA (2005 – Table 2) indicates that 

this age group includes behaviors where... “Food consumption expands. Children’s floor 

mobility increases (surface contact). Children are increasingly likely to mouth nonfood 

items. Development of personal dust clouds.” These types of behaviors would lend 

themselves to potentially expose children to triclosan-treated products. Characteristics of 

children at this age that potentially exposes children to triclosan that would not have been 

captured by the 6-11 year old age category in NHANES include nursing, increasingly 

likelihood of mouthing nonfood items, and “development of personal dust clouds” as a 

characteristic relevant to inhalation exposure. Note: The dust inhalation assessment is not 

part of the updated aggregate assessment, and therefore, not reproduced herein from the 

2008 RED. The nursing exposure pathway has been updated to include the birth to <1 

month old age group.

The younger age groups recommended by USEPA (2005 – Table 4) such as birth to

<1 month, 1 to <3 months, and 3 to <6 months are less likely to be the high exposure 

groups to triclosan because of less contact with treated objects (not to say there is no 

contact, but the 6 to 12 month age group are “increasingly likely to mouth nonfood items –

Table 2”). The older age groups recommended by USEPA (2005 – Table 4) include 1 to 

<2 years, 2 to <3 years, 3 to <6 years old. These age groups reflect the cessation of nursing 

and a reduction in hand-to-mouth activities. The activities in the older age groups reflect 

decreasing frequency of mouthing of objects, nursing, etc and decreasing potential for cooccurrence (e.g., nursing) in comparison to the 6 to 12 month old age group. 

Infant-specific activities resulting in potential exposures that are not accounted for 

by the 6-11 year old age group in NHANES that are likely to co-occur include: 
Page 27 of 34

• Nursing (i.e., triclosan-contaminated breast milk); 

• Object-to-mouth exposures (e.g., mouthing of plastic items such as toys, combs & 

brushes, playground equipment); 

• Hand-to-mouth exposure (e.g., residues in dust stuck to children’s hands); and

• Inhalation of triclosan-contaminated dust.

Other potential exposure pathways for infants in the 6 to 12 month old age group 

that are captured – and likely overestimated for the 6 to 12 month olds -- by the NHANES 

age groups 6-11 years old include:

• Brushing teeth with triclosan-treated tooth paste;

• Washing hands with triclosan-treated antibacterial soap;

• Exposure to impregnated fabrics and textiles such as clothing/sportswear, blankets, 

mattresses, tooth brush bristles, etc. that may be treated with triclosan;

• Exposure to impregnated polymers and plastics such as food contact surfaces (e.g., 

cutting boards, conveyor belts, counter and table tops).

Infant-specific Exposure Pathways

Nursing

Triclosan has been detected in urine in a substantial portion of the population.

Therefore, mothers that are exposed to triclosan also have the potential to expose their

nursing infants to triclosan-containing breast milk. Dayan (2007) reports a breast milk 

concentration of 35.8 ug of triclosan per kilogram whole breast milk. Limited information is 

available in this study on the actual results of the breast milk sampling. The breast milk was 

obtained “...anonymously after collection by the Mothers Milk Banks for routine purposes”

from 62 mothers from California and Texas. The breast milk concentration ranged from two 

non detect samples up to 2100 ug/kg lipid (as opposed to whole milk). Dayan (2007) does 

not report individual data points but summarizes the data as “...the mean of the 

concentrations in the 5 samples with the highest levels... 1742 ug/kg lipid, corresponding to 

35.8 ug/kg whole breast milk.” Using the same ratio by Dayan (2007) of lipids to whole 

milk, the maximum level reported, 2100 ug/kg lipid, corresponds to 43.2 ug/kg whole breast 

milk.

USEPA’s (2008) Child-specific Exposure Factors Handbook recommends nursing 

ingestion rates. The mean breast milk intake from birth to <1 month old is 510 mL/day and 

for a 6 to 12 month old is 620 mL/day (upper percentiles are estimated as the mean plus two 

standard deviations yielding values of 950 and 1000 mL/day, respectively). 

An infant’s estimated daily dose of triclosan-contaminated breast milk is the product 

of the breast milk concentration multiplied by the daily intake volume. The following 

equation is used to determine the daily dose. 

PDD = 

 BW

BM (concentration) x CF1 x CF2 x SP x BM (intake)

where: 
Page 28 of 34

PDD = potential daily dose (mg/kg/day);

BM (concentration) = Breast milk conc. (ug/kg whole breast milk);

BM (intake) = Breast milk intake (ml/day)

SP = Specific gravity of breast milk (1.03).

CF1 = Conversion factor of 0.001 mg/ug.

CF2 = Conversion factor of 0.001 kg/ml.

BW = body weight of an infant (kg).

Assumptions

• As a bounding estimate, the maximum breast milk concentration in whole breast milk 

from 62 mothers reported by Dayan (2007) is assumed (i.e., 43.2 ug/kg whole breast 

milk).

• The breast milk intake rates from birth to <1 month old and 6 to <12 month old are 

means of 510 and 620 mL/day, respectively (upper percentiles of 950 and 1000 

mL/day, respectively). (USEPA 2008).

• Specific gravity of breast milk 1.03 (KellyMom.com).

• The body weights for birth to <1 month is 4.8 kg and for a 6 to <11 month old is 9.2 

kg (USEPA 2008).

The daily doses of triclosan resulting from nuring for an infant in the birth to <1 month 

old and 6 to 12 months old age groups using the mean milk intake rates are estimated to be 

0.0047 and 0.0030 mg/kg/day, respectively. The corresponding MOEs are 1700 and 2700, 

respectively (i.e., BMDL20 of 8 mg/kg/day / daily dose). The target MOE of 30 indicates no 

risks of concern. 

Object-to-mouth

Plastics and polymers used in toys can be treated with triclosan during the 

manufacturing process. Therefore, children’s post application incidental oral exposures to 

treated toys may occur. 

There is potential for incidental ingestion of triclosan residues when children play 

with and mouth plastic objects such as toys treated with triclosan. To determine incidental 

oral exposure of children mouthing objects such as triclosan-treated plastic used to 

manufacture toys, the following equations were used:

PDD = 

 BW

SR x SE x SA

where: 

PDD = potential daily dose (mg/kg/day);

SR = surface residue (mg/cm2);

SE = saliva extraction efficiency (unitless fraction)

SA = surface area of toy mouthed (cm2

/day)

BW = body weight of an infant (kg).

And

SR = % a.i x W x CF x F

 
Page 29 of 34

where:

SR = surface residue (mg a.i./cm2)

% a.i. = fraction active ingredient in toy by total weight (unitless)

W = weight of toy (g/cm2)

CF = conversion factor (1,000 mg/g)

F = fraction additive available at the surface of the toy (unitless)

Assumptions

• The maximum surface area for mouthing an object is taken from the SHEDs 

Technical Manual’s Appendix G. The maximum surface area is 50 cm2

(http://www.epa.gov/heasd/products/sheds_multimedia/files/SHEDS_Residentialv4_Techman

ual_06-16-2010.Final.pdf)

• Chemical specific leaching data are not available, and therefore, the amount of active 

ingredient at the surface of the plastic object which is assumed to be available for 

mouthing is based on the following assumptions

o The plastic object such as a toy is manufactured from ABS or polystyrene 

plastic; and

o No more than 0.5% of the additive is available on the surface of the plastic 

object each day. 

• The weight of a 50 cm2 toy is 5 g, which is based on data showing that a polyethylene 

highchair sample with a surface area of 12.7 cm2 weighs 1.3072 g (i.e., 0.1 g/cm2).

• The triclosan registered antimicrobial product contains 99% a.i. by weight and is used 

to treat plastic at a rate of 0.5% product by weight of the plastic material; thus, the % 

a.i. in treated plastic is calculated as 0.99 ai weight fraction x 0.5% = 0.5% ai in the 

treated plastic.

• The saliva extraction efficiency is assumed to be 50% (EPA 2001).

• The body weight of a 6 to 11 month old infant is 9 kg (average of the male and female 

body weights rounded to a whole number) (USEPA 2002).

Table 4.3 shows the calculations of the incidental oral exposure and MOE for infants 

mouthing triclosan-treated plastic objects such as toys. The MOE of 1,200 is above the target 

MOE of 30 and is not of concern.

Table 4.3. Incidental Oral Exposure and MOE for Infants Mouthing TriclosanTreated Objects such as Toys

Duration % a.i.

Plastic 

Weight 

(g)

Fraction of 

triclosan 

available on 

plastic 

surface 

Surface 

area 

mouthed 

(cm2)

Residue on 

Surface of 

plastic 

(mg/cm2)

Saliva 

extraction 

efficiency

Exposure a

(mg/kg/day)

MOE 

(Target MOE is 

30) b

ST 0.5% 5 0.5% 50 0.0025 50% 0.0069 1,200

(a ) Potential exposures are expressed as mg/kg/day; equations used to estimate exposure are presented above.

(b) MOE = BMDL20/exposure estimate [Where: BMDL20 = 8 mg/kg/day]. Target MOE = 30. 
Page 30 of 34

Hand-to-mouth Ingestion of House Dust

Children in the 6 to 12 month old age group exhibit hand-to-mouth activities that may 

lead to triclosan exposure that would not be accounted for in the NHANES 6-11 year old 

subpopulation. Residues on hands may result from crawling on floors with triclosancontaminated dust. Hand-to-mouth activities are being assessed for an infant that may ingest 

dust that adheres to their hands that is unique to this age group as another potential pathway 

for aggregate exposure.

The amount of house dust ingested by children or the amount of dust that could 

adhere to a child’s hand was not available for the 2008 triclosan RED. Therefore, in 2008 the 

triclosan assessment was based on soil adherence factors. Ozkaynak (in press) reports 

modeled estimates for dust ingestion rates for children 3 to <6 years old. This new 

publication models the dust ingestion from hand-to-mouth activities and reports a mean of 20 

mg of dust ingested per day (p95 = 74 mg/day and p100 = 649 mg/day). The revised 

trilcosan assessment herein has been updated to use the available information in Ozkaynak 

(in press) to estimate exposure to children from the hand-to-mouth dust ingestion pathway. 

Note: Ozakaynak (in press) “...examined 3 to <6 year-old children only based on high 

frequency of mouthing behaviors for this age group and availability of more adequate 

exposure factor and input data for the SHEDS model than for some of the other age groups.” 

Although this age group is older than the infant age group (6 to 12 month) selected for 

triclosan, the estimates for the 3 to <6 were selected by Ozkaynak (in press) as a high end 

estimate and is used herein as part of the bounding estimate for the 6 to 12 month old age 

group. If the need arises to refine the risks generated for this pathway, the ingestion rate by 

various age groups could be further modeled.

Canosa et al (2007) provides triclosan dust concentrations from 10 private homes in 

Spain. Triclosan concentrations in dust averaged 702 ng/g in the homes (range of 240 to 

2,200 ng/g). The indoor dust samples were collected using a vacuum cleaner with paper dust 

bags. The fraction of dust with particle sizes less than 60 um were collected.

 

To calculate incidental ingestion exposure to triclosan due to hand-to-mouth ingestion 

of dust, the following equation is used: 

PDD = Dust (conc) x IGR x CF1 x CF2

 BW

 

where:

PDD = Potential daily dose (mg/kg/day);

Dust (conc) = Indoor dust concentration (ng triclosan/g house dust);

IGR = Dust ingestion rate (mg of dust/day);

CF1 = Unit conversion factor (0.000001 mg triclosan in dust/ng

triclosan in dust); 

CF2 = Unit conversion factor (0.001 g house dust/mg house dust); and

BW = Body weight (9 kg)
Page 31 of 34

Assumptions

• Ozkaynak (in press) reports modeled estimates of ingestion rates of dust from handto-mouth activities for the 3 to <6 year old age group -- mean of 20 mg/day, p95 of 74 

mg/day, and p100 of 649 mg/day;

• The body weight of a 6 to 11 month old infant is 9 kg (average of the male and female 

body weights rounded to a whole number) (USEPA 2002).

• Canosa et al (2007) provides triclosan dust concentrations from 10 private homes in 

Spain. Triclosan concentrations in dust averaged 702 ng triclosan/g of house dust in 

the homes (range of 240 to 2,200 ng/g).

Results

The calculation of the short- and intermediate-term oral doses (toxicological endpoint 

selected is also protective of the long-term duration) and the oral MOEs are shown in Table 

4.4. The oral MOEs are well above the target MOE of 30. It is important to note that these 

results are intended to be used as a bounding estimate to illustrate that the dust ingestion 

pathway – at any combination of currently available dust concentration and dust ingestion

rates – does not trigger a risk. It is unknown if any individuals exist at the point on the 

distribution estimated by combining the maximum dust concentrations from a sample size 

taken in Spain with the maximum potential dust ingestion rate. 

Table 4.4. Short- and Intermediate-term (and Long-term) Incidental Oral Postapplication Exposures and MOEs for Infant Hand-to-mouth from Contacting 

Triclosan-contaminated House Dust

Exposure Scenario

Triclosan Dust 

Residuea (ng

triclosan/g dust)

Dust Ingestion Rateb

(mg/day)

Daily Dosec

(mg/kg/day) Oral MOEd

Maximum dust concentration

2200

20 (mean) 4.8E-6 1.7E+6

74 (p95) 1.8E-5 4.4E+5

649 (p100) 1.6E-4 5.0E+4

Mean dust concentration

702

20 (mean) !.5E-6 5.2E+6

74 (p95) 5.8E-6 1.4E+6

649 (p100) 5.1E-5 1.6E+5

a Dust residue: maximum concentration of 2200 ng triclosan/g house dust and average of 702 ng triclosan/g of 

house dust (Canosa et al 2007).

b Dust ingestion rate from hand-to-mouth: Ozkaynak (in press) Table II.

c Daily Dose (mg/kg/day) = [(Dust residue, ng/g)*(ingestion rate of house dust)*(conversion factor 0.000001 

mg/ng)*( conversion factor 0.001 g/mg)]/(body weight, 9 kg)]

d MOE = BMDL20 (mg/kg/day) / daily dose(mg/kg/day) [Where BMDL20 = 8 mg/kg/day]. Target MOE = 30.

Infant Aggregate

Aggregate risks for children less than 6 years old have also been considered separately 

from the results of the NHANES-based biological monitoring assessment. Table 4.5 presents 

the aggregate risks for the 6 to 12 month old age group. The aggregate risks presented 

represent the high-end of exposure that may co-occur from the various EPA and FDAregulated triclosan products. The risk (i.e., MOE) estimated for the 6-11 year old 2007-2008 

NHANES age group is used in conjunction with infant-specific exposure activities. The 6-11 
Page 32 of 34

year old age group represents exposures to all of the potential EPA-registered uses such as

textiles and fabrics; plastic products; as well as FDA-regulated soaps and toothpaste. Clearly, 

including exposures to the FDA-regulated soaps and toothpaste for 6-11 year olds is a 

conservative assessment of exposure from these products to 6 to 12 month olds. Future 

refinements to the infant aggregate should focus on this portion of the total exposure. 

The aggregate risks for infants 6 to 12 months old have been estimated by combining 

the mean NHANES estimate with the infant-specific bounding risks. The aggregate MOE,

from the measured mean exposure estimates converted from the 6-11 year old urine 

concentrations in NHANES mathematically combined with the screening-level deterministic 

estimates for nursing, object-to-mouth, and hand-to-mouth, is 610. 

Table 4.5. Aggregate Exposure and Risks for Infants 6 to 12 Month Olds

Scenario Risk (MOE) Representative Pathway

Mean Bounding

2007-2008 NHANES 

6-11 year olds

2,300 NA Exposures inclusive of all triclosantreated products that co-occur in the 

real world for 6-11 year olds 

(excludes infant-specific activities)

Nursing NA 2700 6 to 12 month old infants nursing 

(contaminated breast milk) from 

mothers exposed to triclosan-treated 

products that co-occur in the real 

world

Object-to-mouth NA 1200 Wide range of triclosan-treated 

products such as toys that may be 

mouthed by infants

Hand-to-mouth NA 5.2E+6 Infants mouthing hands that have 

been contaminated by triclosan 

residues in house dust at the mean 

triclosan house dust concentration and 

mean house dust ingestion rate (rate is 

for 3 to <6 year old age group)

Aggregate a

(Total MOE)

610b

(mean + bounding)

Total exposure of a 6-11 year old plus 

infant-specific activity exposures

(a) Aggregate (Total MOE) = 1/((1/MOENHANES) + (1/MOENursing) + (1/MOEObject) + (1/MOEHTM))

(b) Mean Aggregate = Sum of the mean NHANES MOEs plus the bounding MOE estimates from nursing, 

object-to-mouth, and hand-to-mouth.Where BMDL20 of 8 mg/kg/day is used. Target MOE = 30.
Page 33 of 34

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