RESIDENTIAL INDOOR EXPOSURES OF CHILDREN TO
PESTICIDES FOLLOWING LAWN APPLICATIONS
R G Lewis' and M G Nishioka2
'National Exposure Research Laboratory, U.S. Environmental Protection Agency,
Research Triangle Park, NC 27711-2055, USA
2Battelle Memorial Institute, Columbus, OH 43201, USA
ABSTRACT
Methods have been developed to estimate children's residential exposures to pesticide residues
and applied in a small field study of indoor exposures resulting from the intrusion of lawn-applied
herbicide into the home. Sampling methods included size-selective indoor air sampling; wipe
sampling of floors, sills, tables; the polyurethane foam (PUF) roller for dislodgeable carpet
surface residues; and the HVS3 vacuum sampler for floor dust. Personal exposure samples
included hand wipes and morning void urine samples.
Pesticide spray drift was found to result in only a relatively minor increase in indoor pesticide
levels. Post-application air intrusion from closed house ventilation and the opening and closing
of doors and windows increased indoor background levels 6-fold, while track-in by high activity
children and pets, and wearing shoes indoors, increased indoor levels by 37-fold. Indoor 2,4-D
levels were found to increase continually over a one-week period, with the increase in indoor air
levels corresponding to the increased floor dust levels, suggesting resuspension ofhouse dust by
human activity. Similar estimates of non-dietary exposure are obtained from models based on
100 mg dust ingestion and surface contact simulated by the PUF roller.
INTRODUCTION
Pesticides are used inside the home and putside on the lawn or garden. After either application,
they tend to accumulate indoors in air, house dust, upholstery, on surfaces, and also on children's
toys. Pesticides sprayed on the lawn may be tracked indoors, where they can persist for months
or years protected from environmental breakdown, as opposed to days outside on the grass.
Typically, pesticide concentrations in indoor air and house dust are 10-100 times those found in
outdoor air and surface soil. Over the past several years, parallel efforts by the U.S.
Environmental Protection Agency (USEPA) have been underway to assess the potential
exposures small children may receive from pesticide products used in and around the home.
Initial studies [ 1 ] suggested that infants and toddlers may receive proportionately larger exposures
than adults from both the respiratory and dust ingestion routes. Small children are considered
to be the population of highest risk since they spend most of their time indoors. Much of this
time is spent in contact with floors, engaging in mouthing of hands, toys, and other objects.
Since these initial findings, several laboratory and field studies have been undertaken. These
have involved experiments to determine the dislodgeability of pesticides from surfaces (i.e., their
potential for transfer to skin) and investigation of the mechanisms of translocation of pesticide
residues from outdoors to indoors and their redistribution within the indoor environment.
Specialized tools such as the HVS3 vacuum and the PUF roller were developed and evaluated for
determining floor dust loadings and estimating dislodgeable residues [1, 2, 3]. Studies with
human subjects have shown that pesticides are dislodged from surfaces by saliva-moistened skin

-------
(as a mouthing child's would often be) much more efficiently than by dry skin [4],
Track-in of lawn-applied pesticides is of particular interest, since many homeowners use
pesticides for lawn care and may not use them indoors. The presence of insecticides such as
chlorpyrifos and pyrethroids in indoor air and dust suggests primary indoor use, although
migration and track-in from perimeter and foundation treatments may also contribute to indoor
residues. The presence indoors of 2,4-dichlorophenoxyacetic acid (2,4-D), carbaryl and
chlorothalonil, which are applied exclusively outdoors, implies that residues have been
transported from outdoors. Previous studies have shown that walking over treated turf as much
as one week after application resulted in transfer of residues to carpet dust that were proportional
(3-4%) to the dislodgeable residues on the turf [5,6]. Over the past three years, studies have been
conducted at 12 households to determine the extent to which lawn-applied 2,4-D may be tracked
indoors and disbursed throughout the house following both homeowner and professional
applicators lawn treatments.
METHODS
Study homes were single floor with basement (except for one split level), surrounded on all sides
by turf, and carpeted in the main living room and a child's bedroom. Each family consisted of
two adults, two to three school-age children, and one pet (one home had no pets). Sampling
methods included HVS3 vacuum sampling for floor dust residues (2 m2 area); wipes of solid
surfaces such as bare floors, table tops and indoor window sills; dislodgeable residue sampling
of carpet surfaces (wetted PUF roller); and air sampling by particle size. Sampling locations were
selected inside each home, including a frequently-used entry area, a main living area, dining area,
kitchen and child's bedroom that would constitute the primary living areas in any home. Cotton
gauze wipes moistened with 2 mL of 70:30 phosphate bufferracetonitrile were used on indoor
surfaces [5]. A medium volume cascade impactor (12 L/min) was used to collect indoor air
residues during the period of application (ca. 2 h). Windows and doors to the homes were open
at the times of application. For post-application air sampling, four collocated PUF air samplers
[7] and provided with inlets for collection of <20 (im (total aerosol), <10 pm, <2.5 ^m and <1
jim air particles and fine particle filters were operated for 24-h periods (4 L/min). Two
unoccupied model homes were also included to assess the relative importance of spray drift and
post-application aerial intrusion relative to track-in.
2,4-D dimethylamine herbicide was applied at each study home either by homeowners or
professional applicators. Sampling at each home took place over two one-week periods (pre- and
post-application). A 24-h indoor air sample was collected on one day (Day 0) during the pre-
application week and on Days 1 and 3 post-application. A 2-h indoor air sample (cascade
impactor) was taken during the period of lawn application. Wipe sampling of sills, tables, and
bare floors; collection of a carpet surface dislodgeable residue sample; and vacuum sampling of
floors all occurred on Day 7 post-application. Deposition coupons on the lawn were used to
estimate 2,4-D application rates. An integrated air exchange rate measurement was made during
the post-application week. Homeowner treatments were studied during the first year, followed
by professional applications in the second. In the third year of the study, dermal (hand) wipe
samples were obtained with 2-propanol-wetted gauze [8], along with table wipe samples, and
vacuumed floor dust samples on three separate days after the lawn application. First morning
void urine samples were also collected on the morning following each dermal wipe sample, so
as to ascertain whether urinary excretion of 2,4-D could be tied to microenvironmental levels
and/or dermal contaminant levels. The dermal wipe samples and urine samples were collected
from the adult applicator and one resident child.

-------
RESULTS
Indoor air concentrations of 2,4-D increased from non-detectable before lawn treatment to 0.2 to
10 ng/m3(10 jim inlet) after homeowner application, with about 65% of the total particulate 2,4-D
associated with respirable particles (<10 ng/m3). 2,4-D associated with <1 p.m and smaller
particles made up 25-30% of the total mass. Detectable residues of 2,4-D were found on all
surfaces one week after application. The surface concentration gradient followed the occupant
traffic pattern through the house. Post-application floor surface loadings of 2,4-D in the living
areas ranged from 1 to 228 (J.g/m2 on carpeted floors and 0.2 to 20 jig/ni2 on bare floors, compared
to 0 to 0.8 |ig/m2 (median 0.5 |ig/m2) pre-application. About 1% of the 2,4-D in floor dust was
dislodgeable (PUF roller wetted with acetonitrile:phosphate buffer) and potentially available for
dermal contact. 2,4-D residues on window sills and tables followed a similar traffic gradient,
with surface loadings of 0.2 to 20 jig/m2 (none were detectable before application). In homes in
which occupants removed their shoes at the entryway, 2,4-D loadings on floors were typically
an order of magnitude lower than in those in which shoes were worn.
The data presented here in Figure 1 show the indoor floor dust loadings of 2,4-D in ng/m2 for
three representative homes one week after homeowner applications to lawns. Home By was
categorized as a home with high child activity and high pet activity, and Home Zm had high child
activity, but low pet activity. Home Rr had high child and low pet activity, but both adults and
children routinely removed shoes at the door when entering from outside (which was not the case
for Homes By and Zm). Note that the concentration gradients inside the homes generally follow
the traffic patterns through the houses (carpeting accounted for the apparent gradient shift within
Home Rr). 2,4-D floor loadings in participating households in which occupants routinely
removed shoes were typically 10 to 100 times lower than in those in which shoes were worn.
Window sill wipes and air monitoring during spray applications indicated that intrusion of 2,4-D
into the home by spray drift was minor compared to track-in. Table-top loadings were
approximately one-tenth of floor loadings and resulted from deposition of dust resuspended from
the floors by human and pet activity. The same patterns of floor dust distributions were also
observed after professional applications (where the applicator did not enter the house), but post-
application 2,4-D dust loadings in the living rooms of high child/pet activity homes were reduced
by 50-75%.
Indoor air concentrations in ng/m3 of 2,4-D obtained from collocated sampling with PM2 5 and
PM,0 size-selective inlets on Day 3 after homeowner and professional applications were similar
to those found on Day 1 and 25-50% of those found during application. Across all homes, indoor
levels during the application period were only slightly less during homeowner vs. professional
applications. However, mean indoor air levels on Days 1 and 3 after professional application
were about half of those after homeowner application and 2,4-D was associated with ultra-fine
particles (<1 |im), which accounted for about 75% of the total (inverse of what was found with
homeowner treatment). For homeowner applications, only 25% of the indoor air levels could be
attributed to intrusion during spraying; in contrast, in a low activity home where the applicator
did not wear shoes indoors, 100% of the Day 1 air levels were attributable to 2,4-D spray drift.
Post-application air concentrations were roughly proportional to floor dust loadings, supporting
the supposition that resuspension of floor dust is responsible for respirable 2,4-D in indoor air.
The higher 2,4-D air levels were found in homes with active children and pets, and especially
with those where shoes were also worn indoors. Likewise, the homes in which 2,4-D was not

-------
detected in air were those with low levels of activity and/or no shoes worn indoors.
In the third year of the study, biological monitoring was conducted along with more intensive
environmental sampling in four of the study homes. Dust levels were monitored pre-application
and on Days 1,3, and 7 post-application. Figure 2 shows the temporal profile of indoor residues
in a high-activity (Home By).
DISCUSSION
For typical homes, track-in was found to be the most significant route of transport of 2,4-D
residues from the lawn indoors. For high activity homes, transport via an indoor-outdoor dog,
the applicator's shoes, and by children was estimated to account for about 58%, 25%, and 8% of
the indoor residues, respectively. Spray drift and post-application aerial intrusion were minimal
contributors (<1%) except for homes in which outdoor shoes were not worn indoors and which
had low pet activity. Resuspension of floor dust was the primary source of 2,4-D in indoor air,
on table tops, and on window sills.
Relative exposures to 2,4-D via the air route vs. dust ingestion routes could not be accurately
estimated since floor dust sampling was conducted several days after air sampling (except for the
last year). However, since Day 3 air levels were on average higher than Day 1 levels, airborne
2,4-D was probably due primarily to dust resuspension and would be expected to be at similar
or higher levels on Day 7 (when floor dust was collected). Hence for Home By, the average daily
respiratory dose based on PM10 received by children between the ages of 6 months and three years
spending 24 hours indoors (avg. 6.4 m3/d inhalation rate [9]) one week after homeowner
application would have been 68 ng/d, while the average dose received from ingestion of 100 mg
[9] of floor dust from the living room would have been 100 times higher at 6.7 p.g/d. After
professional application, these potential exposures were reduced to 16 ng/d vs. 4.2 fig/d,
respectively. For Home Zm, air and dust route exposures would have been 8.1 ng/d and 2.8 ng/d
after homeowner application and 15 ng/d and 0.6 fig/d, respectively, after professional lawn
treatment. By contrast, in shoes-off home Rr, which had very low post-application dust loadings
and relatively low concentrations of 2,4-D in house dust, ingestion of 100 mg of dust would have
resulted in the intake of only 0.5 fig/d andrespiration to 4.4 ng/d after homeowner treatment. The
mean dust contribution over all homes in the study is estimated to have been about 2 ng/d and
the mean air route contribution 18 ng/d one week after homeowner application compared to 12
ng/d and 1.2 jig/d, respectively, after professional treatment. It should be noted, however, that
this comparison may not be valid for the sum of all participating homes since only half the homes
participated in both phases of the study, which were also conducted in different years. For a 10
kg child, the average total potential dose via the inhalation and non-dietary ingestion routes would
be 0.1 to 0.2 jig/kg/d. This is substantially less than the EPA Reference Dose of 10 fig/kg/d or
the World Health Organization's Acceptable Daily Intake value of300 |ig/kg/d. However, these
reference doses are not necessarily meant for infants and toddlers.
Use of dislodgeable residue data obtained with the PUF roller, combined with frequency of
mouthing activity, may also be used to estimate intake by non-dietary ingestion for comparison
with estimates made from ingestion of 100 mg/d of house dust. Assuming that the floor-to-hand
transfer efficiency was the same as that for the wetted PUF roller, 10 mouthing events (one whole
hand) per hour for 12-h/d [10], and 50% efficiently for removal of 2,4-D by salivation [4],
exposure estimates agree quite well with those obtained on the basis of dust ingestion of 100
mg/d for a 10 kg child.
Additional research is underway in occupied homes and in the USEPA test home to examine fate

-------
and transport of pesticides from indoor applications and determine the potential for human
exposures. House dust has been fractionated by sieving and aerosol suspension into seven
fractions ranging from <4 fim to 500 jim and analyzed to determine the distribution of pesticides
as a function of particle size (concentrations increase with decreasing particle size). The
mechanics of transfer of particles from outdoors to indoors on shoes, from indoor surfaces to dry
and wet skin, and from floors into air by human activity are being investigated. Other studies are
underway to better determine surface-to-skin and skin-to-mouth transfer efficiencies, pesticide
bioavailability from dust, and the relationship of child activity patterns to residential exposures.
Such studies are essential before accurate exposure assessments can be made.
DISCLAIMER
This work has been reviewed in accordance with the U.S. Environmental Protection Agency's
peer and administrative review process and approved for presentation and publication. Mention
of tradenames or commercial products does not constitute endorsement or recommendation for
use.
REFERENCES
1.	Lewis, R G, Fortmann, R C, and Camann, D E. 1994. Evaluation of methods for the
monitoring of the potential exposure of small children to pesticides in the residential
environment Arch. Environ. Contam. Toxicol., Vol. 26, pp 37-46.
2.	ASTM. 1995. ASTM Standard D 5438-94, Standard Practice for Collection of Floor Dust for
Chemical Analysis, West Conshohoken, PA: Annual Book of Standards, Vol. 11.03,
American Society for Testing and Materials.
3.	ASTM. 1998. ASTM Standard D 6333-98, Standard Practice for Collection of Dislodgeable
Residues from Floors, ibid.
4.	Camann, D E, Majumdar, T K, Harding, J C, Ellenson, W D, and Lewis, R G. 1996. Transfer
efficiency of pesticides from carpet to-saliva-moistened hands, in Measurement of Toxic and
Related Air Pollutants: Proceedings of an International Specialty Conference, Publication
VIP-64, Pittsburgh, PA: Air & Waste Management Association, pp 532-540.
5.	Nishioka, M G, Burkholder, H M, Brinkman, MC, Gordon, S M, and R, G. Lewis. 1996.
Measuring transport of lawn-applied herbicide acids from turf to home: correlation of
dislodgeable 2,4-d turf residues with carpet dust and carpet surface residues, Environ. Sci.
Technol. Vol. 30, pp 3313-3320.
6.	Nishioka, M G, Burkholder, H M, Brinkman, MC, and Gordon, S M. 1997. Simulation of
track-in of lawn-applied pesticides from turf to home: comparison of dislodgeable turf
residues with carpet dust and carpet surface residues. U.S. EPA Report EPA600/R-97/108.
7.	ASTM, 1995. ASTM Standard D 4861-94a, Standard Practice for Sampling and Selection of
Analytical Techniques for Pesticides and Polychlorinated Biphenyls in Air, West
Conshohoken, PA: Annual Book of Standards, Vol. 11.03, American Society for Testing and
Materials.
8.	Geno, P W, Camann, D E, Harding, J C, Villalobos, K, and Lewis, R G. 1996. A handwipe
sampling and analysis procedure for the measurement of dermal contact to pesticides. Arch.
Environ. Contam. Toxicol. Vol. 30, pp 132-138.

-------
9.	EPA. 1997a. Exposure Factors Handbook, Report No. EPA/600/P-95/002F: Washington, DC:
U. S. Environmental Protection Agency, Office of Research and Development.
10.	Reed, J K, Jimenez, M, Freeman, N C G, and Lioy, P J 1998. Quantification of children's
hand mouthing activity through a video taping methodology. J. Exp. Anal. Environ. Epidem.
Vol, 9 (in press).

-------
250
hIC
By hiP 125-
S
0.5
228
0.6
188
0,4
117
l l Pm-ap plication, Vacuum
1 1 Post-application, Vacuum
¦¦ Post-application, Wipe
45
¦¦ 25
<01 2 H 1|	1

Entry
Living Room Dining Roam Kitchen* Bedroom
too-]






hiC - high child


74




activity
hie






hiP - high pet
Zm ioP so-






activity
s



35


S - shoes





13
indoors






12 _
o-
t

1

0.4

0,4 | j 0.2 r-i-, NS - no shoes
Entry	Kitchen Living Room Dining Room Bedroom
5,0-i
2.5
oa
07
08
0.5
0.3
0.1
Entry/Hal [* Dining Room*
Bedroom
Living Room
*¦ Traffic Flow
Figure 1. Floor dust loadings in ng/m2 of 2,4-D in three homes one week after application
of 2,4-D to lawn. Rooms marked with an asterisk were not carpeted.
Floor
pg/m2
(floor/table)
1" Rain
PM10
Table
PM10
Pre
Day
Application
Figure 2. Temporal profile of 2,4-D residues inside a high activity home (By) before and after
application of 2,4-D to lawn. Note that 2.5 cm of rain fell 24 h after application.

-------
RESIDENTIAL INDOOR EXPOSURES OF CHILDREN TO
PESTICIDES FOLLOWING LAWN APPLICATIONS
R G Lewis' and M G Nishioka2
'National Exposure Research Laboratory, U.S. Environmental Protection Agency,
Research Triangle Park, NC 27711-2055, USA
2Battelle Memorial Institute, Columbus, OH 43201, USA
ABSTRACT
Methods have been developed to estimate children's residential exposures to pesticide residues
and applied in a small field study of indoor exposures resulting from the intrusion of lawn-applied
herbicide into the home. Sampling methods included size-selective indoor air sampling; wipe
sampling of floors, sills, tables; the polyurethane foam (PUF) roller for dislodgeable carpet
surface residues; and the HVS3 vacuum sampler for floor dust. Personal exposure samples
included hand wipes and morning void urine samples.
Pesticide spray drift was found to result in only a relatively minor increase in indoor pesticide
levels. Post-application air intrusion from closed house ventilation and the opening and closing
of doors and windows increased indoor background levels 6-fold, while track-in by high activity
children and pets, and wearing shoes indoors, increased indoor levels by 37-fold. Indoor 2,4-D
levels were found to increase continually over a one-week period, with the increase in indoor air
levels corresponding to the increased floor dust levels, suggesting resuspension of house dust by
human activity. Similar estimates of non-dietary exposure are obtained from models based on
100 mg dust ingestion and surface contact simulated by the PUF roller.
INTRODUCTION
Pesticides are used inside the home and putside on the lawn or garden. After either application,
they tend to accumulate indoors in air, house dust, upholstery, on surfaces, and also on children's
toys. Pesticides sprayed on the lawn may be tracked indoors, where they can persist for months
or years protected from environmental breakdown, as opposed to days outside on the grass.
Typically, pesticide concentrations in indoor air and house dust are 10-100 times those found in
outdoor air and surface soil. Over the past several years, parallel efforts by the U.S.
Environmental Protection Agency (USEPA) have been underway to assess the potential
exposures small children may receive from pesticide products used in and around the home.
Initial studies [ 1 ] suggested that infants and toddlers may receive proportionately larger exposures
than adults from both the respiratory and dust ingestion routes. Small children are considered
to be the population of highest risk since they spend most of their time indoors. Much of this
time is spent in contact with floors, engaging in mouthing of hands, toys, and other objects.
Since these initial findings, several laboratory and field studies have been undertaken. These
have involved experiments to determine the dislodgeability ofpesticides from surfaces (i.e., their
potential for transfer to skin) and investigation of the mechanisms of translocation of pesticide
residues from outdoors to indoors and their redistribution within the indoor environment.
Specialized tools such as the HVS3 vacuum and the PUF roller were developed and evaluated for
determining floor dust loadings and estimating dislodgeable residues [1,2, 3]. Studies with
human subjects have shown that pesticides are dislodged from surfaces by saliva-moistened skin

-------
(as a mouthing child's would often be) much more efficiently than by dry skin [4],
Track-in of lawn-applied pesticides is of particular interest, since many homeowners use
pesticides for lawn care and may not use them indoors. The presence of insecticides such as
chlorpyrifos and pyrethroids in indoor air and dust suggests primary indoor use, although
migration and track-in from perimeter and foundation treatments may also contribute to indoor
residues. The presence indoors of 2,4-dichlorophenoxyacetic acid (2,4-D), carbaiyl and
chlorothalonil, which are applied exclusively outdoors, implies that residues have been
transported from outdoors. Previous studies have shown that walking over treated turf as much
as one week after application resulted in transfer of residues to carpet dust that were proportional
(3-4%) to the dislodgeable residues on the turf [5,6]. Over the past three years, studies have been
conducted at 12 households to determine the extent to which lawn-applied 2,4-D may be tracked
indoors and disbursed throughout the house following both homeowner and professional
applicators lawn treatments.
METHODS
Study homes were single floor with basement (except for one split level), surrounded on all sides
by turf, and carpeted in the main living room and a child's bedroom. Each family consisted of
two adults, two to three school-age children, and one pet (one home had no pets). Sampling
methods included HVS3 vacuum sampling for floor dust residues (2 m2 area); wipes of solid
surfaces such as bare floors, table tops and indoor window sills; dislodgeable residue sampling
of carpet surfaces (wetted PUF roller); and air sampling by particle size. Sampling locations were
selected inside each home, including a frequently-used entry area, a main living area, dining area,
kitchen and child's bedroom that would constitute the primary living areas in any home. Cotton
gauze wipes moistened with 2 mL of 70:30 phosphate buffer:acetonitrile were used on indoor
surfaces [5], A medium volume cascade impactor (12 L/min) was used to collect indoor air
residues during the period of application (ca. 2 h). Windows and doors to the homes were open
at the times of application. For post-application air sampling, four collocated PUF air samplers
[7] and provided with inlets for collection of <20 jim (total aerosol), <10 fim, <2.5 ^m and <1
Jim air particles and fine particle filters were operated for 24-h periods (4 L/min). Two
unoccupied model homes were also included to assess the relative importance of spray drift and
post-application aerial intrusion relative to track-in.
2,4-D dimethylamine herbicide was applied at each study home either by homeowners or
professional applicators. Sampling at each home took place over two one-week periods (pre- and
post-application). A 24-h indoor air sample was collected on one day (Day 0) during the pre-
application week and on Days 1 and 3 post-application. A 2-h indoor air sample (cascade
impactor) was taken during the period of lawn application. Wipe sampling of sills, tables, and
bare floors; collection of a carpet surface dislodgeable residue sample; and vacuum sampling of
floors all occurred on Day 7 post-application. Deposition coupons on the lawn were used to
estimate 2,4-D application rates. An integrated air exchange rate measurement was made during
the post-application week. Homeowner treatments were studied during the first year, followed
by professional applications in the second. In the third year of the study, dermal (hand) wipe
samples were obtained with 2-propanol-wetted gauze [8], along with table wipe samples, and
vacuumed floor dust samples on three separate days after the lawn application. First morning
void urine samples were also collected on the morning following each dermal wipe sample, so
as to ascertain whether urinary excretion of 2,4-D could be tied to microenvironmental levels
and/or dermal contaminant levels. The dermal wipe samples and urine samples were collected
from the adult applicator and one resident child.

-------
RESULTS
Indoor air concentrations of 2,4-D increased from non-detectable before lawn treatment to 0,2 to
10 ng/m3 (10 |im inlet) after homeowner application, with about 65% of the total particulate 2,4-D
associated with respirable particles (<10 ng/m3). 2,4-D associated with <1 jim and smaller
particles made up 25-30% of the total mass. Detectable residues of 2,4-D were found on all
surfaces one week after application. The surface concentration gradient followed the occupant
traffic pattern through the house. Post-application floor surface loadings of 2,4-D in the living
areas ranged from 1 to 228 p.g/m2 on carpeted floors and 0.2 to 20 ng/m2 on bare floors, compared
to 0 to 0.8 (ig/m2 (median 0.5 fig/m2) pre-application. About 1% of the 2,4-D in floor dust was
dislodgeable (PUF roller wetted with acetonitrile:phosphate buffer) and potentially available for
dermal contact. 2,4-D residues on window sills and tables followed a similar traffic gradient,
with surface loadings of 0.2 to 20 jig/m2 (none were detectable before application). In homes in
which occupants removed their shoes at the entryway, 2,4-D loadings on floors were typically
an order of magnitude lower than in those in which shoes were worn.
The data presented here in Figure 1 show the indoor floor dust loadings of 2,4-D in (ig/m2 for
three representative homes one week after homeowner applications to lawns. Home By was
categorized as a home with high child activity and high pet activity, and Home Zm had high child
activity, but low pet activity. Home Rr had high child and low pet activity, but both adults and
children routinely removed shoes at the door when entering from outside (which was not the case
for Homes By and Zm). Note that the concentration gradients inside the homes generally follow
the traffic patterns through the houses (carpeting accounted for the apparent gradient shift within
Home Rr). 2,4-D floor loadings in participating households in which occupants routinely
removed shoes were typically 10 to 100 times lower than in those in which shoes were worn.
Window sill wipes and air monitoring during spray applications indicated that intrusion of 2,4-D
into the home by spray drift was minor compared to track-in. Table-top loadings were
approximately one-tenth of floor loadings and resulted from deposition of dust resuspended from
the floors by human and pet activity. The same patterns of floor dust distributions were also
observed after professional applications (where the applicator did not enter the house), but post-
application 2,4-D dust loadings in the living rooms of high child/pet activity homes were reduced
by 50-75%.
Indoor air concentrations in ng/m3 of 2,4-D obtained from collocated sampling with PM2 5 and
PM,0 size-selective inlets on Day 3 after homeowner and professional applications were similar
to those found on Day 1 and 25-50% of those found during application. Across all homes, indoor
levels during the application period were only slightly less during homeowner vs. professional
applications. However, mean indoor air levels on Days 1 and 3 after professional application
were about half of those after homeowner application and 2,4-D was associated with ultra-fine
particles (<1 jim), which accounted for about 75% of the total (inverse of what was found with
homeowner treatment). For homeowner applications, only 25% of the indoor air levels could be
attributed to intrusion during spraying; in contrast, in a low activity home where the applicator
did not wear shoes indoors, 100% of the Day 1 air levels were attributable to 2,4-D spray drift.
Post-application air concentrations were roughly proportional to floor dust loadings, supporting
the supposition that resuspension of floor dust is responsible for respirable 2,4-D in indoor air.
The higher 2,4-D air levels were found in homes with active children and pets, and especially
with those where shoes were also worn indoors. Likewise, the homes in which 2,4-D was not

-------
detected in air were those with low levels of activity and/or no shoes worn indoors.
In the third year of the study, biological monitoring was conducted along with more intensive
environmental sampling in four of the study homes. Dust levels were monitored pre-application
and on Days 1,3, and 7 post-application. Figure 2 shows the temporal profile of indoor residues
in a high-activity (Home By).
DISCUSSION
For typical homes, track-in was found to be the most significant route of transport of 2,4-D
residues from the lawn indoors. For high activity homes, transport via an indoor-outdoor dog,
the applicator's shoes, and by children was estimated to account for about 58%, 25%, and 8% of
the indoor residues, respectively. Spray drift and post-application aerial intrusion were minimal
contributors (<1%) except for homes in which outdoor shoes were not worn indoors and which
had low pet activity. Resuspension of floor dust was the primary source of 2,4-D in indoor air,
on table tops, and on window sills.
Relative exposures to 2,4-D via the air route vs. dust ingestion routes could not be accurately
estimated since floor dust sampling was conducted several days after air sampling (except for the
last year). However, since Day 3 air levels were on average higher than Day 1 levels, airborne
2,4-D was probably due primarily to dust resuspension and would be expected to be at similar
or higher levels on Day 7 (when floor dust was collected). Hence for Home By, the average daily
respiratory dose based on PM10 received by children between the ages of 6 months and three years
spending 24 hours indoors (avg. 6.4 m3/d inhalation rate [9]) one week after homeowner
application would have been 68 ng/d, while the average dose received from ingestion of 100 mg
[9] of floor dust from the living room would have been 100 times higher at 6.7 ng/d. After
professional application, these potential exposures were reduced to 16 ng/d vs. 4.2 ng/d,
respectively. For Home Zm, air and dust route exposures would have been 8.1 ng/d and 2.8 jj.g/d
after homeowner application and 15 ng/d and 0.6 pg/d, respectively, after professional lawn
treatment. By contrast, in shoes-off home Rr, which had very low post-application dust loadings
and relatively low concentrations of 2,4-D in house dust, ingestion of 100 mg of dust would have
resulted in the intake of only 0.5 ng/d ancfrespiration to 4.4 ng/d after homeowner treatment. The
mean dust contribution over all homes in the study is estimated to have been about 2 pg/d and
the mean air route contribution 18 ng/d one week after homeowner application compared to 12
ng/d and 1.2 pg/d, respectively, after professional treatment. It should be noted, however, that
this comparison may not be valid for the sum of all participating homes since only half the homes
participated in both phases of the study, which were also conducted in different years. For a 10
kg child, the average total potential dose via the inhalation and non-dietary ingestion routes would
be 0.1 to 0.2 pg/kg/d. This is substantially less than the EPA Reference Dose of 10 jig/kg/d or
the World Health Organization's Acceptable Daily Intake value of300 [ig/kg/d. However, these
reference doses are not necessarily meant for infants and toddlers.
Use of dislodgeable residue data obtained with the PUF roller, combined with frequency of
mouthing activity, may also be used to estimate intake by non-dietary ingestion for comparison
with estimates made from ingestion of 100 mg/d of house dust. Assuming that the floor-to-hand
transfer efficiency was the same as that for the wetted PUF roller, 10 mouthing events (one whole
hand) per hour for 12-h/d [10], and 50% efficiently for removal of 2,4-D by salivation [4],
exposure estimates agree quite well with those obtained on the basis of dust ingestion of 100
mg/d for a 10 kg child.
Additional research is underway in occupied homes and in the USEPA test home to examine fate

-------
and transport of pesticides from indoor applications and determine the potential for human
exposures. House dust has been fractionated by sieving and aerosol suspension into seven
fractions ranging from <4 |im to 500 |im and analyzed to determine the distribution of pesticides
as a function of particle size (concentrations increase with decreasing particle size). The
mechanics of transfer of particles from outdoors to indoors on shoes, from indoor surfaces to dry
and wet skin, and from floors into air by human activity are being investigated. Other studies are
underway to better determine surface-to-skin and skin-to-mouth transfer efficiencies, pesticide
bioavailability from dust, and the relationship of child activity patterns to residential exposures.
Such studies are essential before accurate exposure assessments can be made.
DISCLAIMER
This work has been reviewed in accordance with the U.S. Environmental Protection Agency's
peer and administrative review process and approved for presentation and publication. Mention
of tradenames or commercial products does not constitute endorsement or recommendation for
use.
REFERENCES
1.	Lewis, R G, Fortmann, R C, and Camann, D E. 1994. Evaluation of methods for the
monitoring of the potential exposure of small children to pesticides in the residential
environment. Arch. Environ. Contam. Toxicol., Vol. 26, pp 37-46.
2.	ASTM. 1995. ASTM Standard D 5438-94, Standard Practice for Collection of Floor Dust for
Chemical Analysis, West Conshohoken, PA: Annual Book of Standards, Vol. 11.03,
American Society for Testing and Materials.
3.	ASTM. 1998. ASTM StandardD 6333-98, Standard Practice for Collection of Dislodgeable
Residues from Floors, ibid.
4.	Camann, D E, Majumdar, T K, Harding, J C, Ellenson, W D, and Lewis, R G. 1996. Transfer
efficiency of pesticides from carpet to-saliva-moistened hands, in Measurement of Toxic and
Related Air Pollutants: Proceedings of an International Specialty Conference, Publication
VIP-64, Pittsburgh, PA: Air & Waste Management Association, pp 532-540.
5.	Nishioka, M G, Burkholder, H M, Brinkman, MC, Gordon, S M, and R. G. Lewis. 1996.
Measuring transport of lawn-applied herbicide acids from turf to home: correlation of
dislodgeable 2,4-d turf residues with carpet dust and carpet surface residues, Environ. Sci.
Technol. Vol. 30, pp 3313-3320.
6.	Nishioka, M G, Burkholder, H M, Brinkman, MC, and Gordon, S M. 1997. Simulation of
track-in of lawn-applied pesticides from turf to home: comparison of dislodgeable turf
residues with carpet dust and carpet surface residues. U.S. EPA Report EPA600/R-97/108.
7.	ASTM. 1995. ASTM Standard D 4861-94a, Standard Practice for Sampling and Selection of
Analytical Techniques for Pesticides and Polychlorinated Biphenyls in Air, West
Conshohoken, PA: Annual Book of Standards, Vol. 11.03, American Society for Testing and
Materials.
8.	Gcno, P W, Camann, D E, Harding, J C, Villalobos, K, and Lewis, R G. 1996. A handwipe
sampling and analysis procedure for the measurement of dermal contact to pesticides. Arch.
Environ. Contam. Toxicol Vol. 30, pp 132-138.

-------
9.	EPA. 1997a. Exposure Factors Handbook, Report No. EPA/600/P-95/002F: Washington, DC:
U. S. Environmental Protection Agency, Office of Research and Development.
10.	Reed, J K, Jimenez, M, Freeman, N C G, and Lioy, P J 1998. Quantification of children's
hand mouthing activity through a video taping methodology. J. Exp. Anal Environ. Epidem.
Vol. 9 (in press).

-------
By
Rr
hlC
hIP
S
Zm
h!C
ioP
S
hiC
IoP
NS
250-
12S-
HKH
50-
5.0—
2.5-
228
OS
Entry
74
Entry
188
a6
I i pro-application, Vacuum
I Post-application, Vacuum
Post-application, Wipe
117
0.4
45
<01 2
Living Room Dining Room
Kitchen*
35
1
13
°-*n
12
q.4 r i
Kitchen
0,2
Entry/Hall* Dining Room*
Kitchen*
25
JLEZL
Bodroom
0.2
Living Room Dining Room Bedroom
0.5
Living Room Bedroom
hiC
hiP
NS
high child
activity
high pet
activity
shoes
indoors
no shoes
Traffic Flow
Figure 1.
Floor dust loadings in jig/m2 of 2,4-D in three homes one week after application
of 2,4-D to lawn. Rooms marked with an asterisk were not carpeted.
Floor
ng/m2
(floor/table)
1" Rain
PM10
Table
PM10
Pre
Day
Application
Figure 2. Temporal profile of 2,4-D residues inside a high activity home (By) before and after
application of 2,4-D to lawn. Note that 2.5 cm of rain fell 24 h after application.

-------
TECHNICAL REPORT DATA
NERL-RTP-0-616 (Please read Instructions on the reverse before completing)
1. REPORT NO.
600/A-99/069
3. RECIPIENTS ACCESSION NO.
A. TITLE AND SUBTITLE
Residential Indoor Exposures of Children to Pesticides Following Lawn
Applications
5. REPORT DATE
6 PERFORMING ORGANIZATION CODE
7. AUTHORS
R.G. Lewis and M.G. Nishhioka
e. PERFORMING ORGANIZATION REPORT NO.
9, PERFORMING ORGANIZATION NAME AND ADDRESS
National Exposure Research Laboratory, U.S. EPA, Research Triangle
Park, NC. and Battelle Memorial Institute, Columbus, Ohio
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
National Exposure Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Methods have been developed to estimate children's residential exposures to pesticide residues and applied in a small
field study of indoor exposures resulting from the intrusion of lawn-applied herbicide into the home. Sampling
methods included size-selective indoor air sampling; wipe sampling of floors, sills, tables; the polyurethane foam
(PUF) roller for dislodgeable carpet surface residues; and the HVS3 vacuum sampler for floor dust. Personal
exposure samples included hand wipes and morning void urine samples.
Pesticide spray drift was found to result in only a relatively minor increase in indoor pesticide levels. Post-application
air intrusion from closed house ventilation and the opening and closing of doors and windows increased indoor
background levels 6-fold, while track-in by high activity children and pets, and wearing shoes indoors, increased
indoor levels by 37-fold. Indoor 2,4-D levels were found to increase continually over a one-week period, with the
increase in indoor air levels corresponding to the increased floor dust levels, suggesting resuspension of house dust by
human activity. Similar estimates of non-dietary exposure are obtained from models based on 100 mg ingestion and
surface contact simulated by the PUF roller.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Fleid/Group


-
18. DISTRIBUTION STATEMENT
Release to Public
10. SECURITY CLASS (This Report)
unclassified
21 NO OF PAGES
20. SECURITY CLASS (This Page)
unclassified
22, PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE	forms/admin/techrpt.frm 7/8/99

-------