DISTRIBUTIONS OF RESIDENTIAL ORGANOCHLORINE PESTICIDE RESIDUALS
ALONG THE ARIZONA/MEXICO BORDER
G. Robertson1, M. Lebowitz2, L. Needham3, M.K. O'Rourke2, S. Rogan2, J, Petty4, J.
Huckins4
U.S. Environmental Protection Agency, Las Vegas, NV, USA
2University of Arizona, Tucson, AZ, USA
3National Center for Environmental Health, Centers for Disease Control and Prevention,
Atlanta, GA, USA
4Columbia Environmental Research Center, U.S. Geological Survey, Columbia, MO, USA
ABSTRACT
The use of DDT has been banned for many years in the United States. Mexico began a 10-
year phase out of DDT in 1997. DDT was banned in the U.S. primarily because of its
environmental persistence. Thus, DDT is still found in the outdoor and indoor environment.
We report the results from samples collected in 83 homes in Arizona along the
Arizona/Mexico border. The media sampled included indoor air, floor dust, dermal wipes,
and blood serum. 4,4'-DDT was detected in 62% of the floor dust samples, 19% of the
indoor air samples, and 31% of the dermal wipes. This may be from spray residuals in older
housing stock, recent use of chemicals obtained in Mexico, track-in from outdoor usage, or
other sources. We report on the concentrations found, examine the distributions of
occurrence of DDT analogs in the various media and discuss possible sources of these
occurrences.
INDEX TERMS
DDT, exposure, indoor air, house dust, dermal
Contact author email: robertson.gary@epa.gov
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INTRODUCTION
Although the use of DDT, has largely been eliminated in the USA and many other countries,
residues remain in the environment and are a subject of concern. For example, the Journal
Chemosphere published 97 articles related to DDT from January, 1995 to January, 2002. The
majority of the articles relate to the occurrence of DDT and other organochlorine pesticides in
the outdoor environment (surface water, sediments, soil, fish, and other wildlife). The
remaining articles mainly present results related to human exposure from studies of human
biological specimens such as milk, blood and adipose tissue. One area that has received little
attention is the persistence and levels of DDT and the degradation products DDE and DDD in
the residential environment. (Note: all values reported here are for the 4,4'-DDT, 4,4'-DDE,
and 4,4'-DDD compounds.) In a 1968 study of 16 homes (182 samples) in Colorado the
mean detected values for DDT, DDE, and DDD in urban house dust were respectively 6.90,
4.37, and 1.77 ug/g (Starr, Aldrich, McDougall, et al., 1974). In a 1970-1971 study in the
Bahama Islands, mean house dust concentrations in 15 homes were DDT 122 ug/g, DDE, 3.7
ug/g, and DDD 2.2 ug/g (Davies, Edmundson, and Raffonelli, 1975). This study was prior to
the ban on DDT usage and illustrates the high DDT/DDE ratios that indicate recent
contamination. More recent work summarized the results of pesticide levels in house dust
from seven different exposure studies conducted at various locations across the USA, for a
total of 1040 samples (Camann, Colt, Teitelbaum, et al., 2000). Dust DDT concentration
median values ranged from O.02 to 0.3 ug/g with a 90th percentile range of 0.07 to 3.0 ug/g.
DDE median values were <0.02 to 0.05 ug/g and the 90th percentile range was O.09 to 0.25
ug/g.
The current work reports the DDT, DDE, and DDD levels found in house dust, indoor air, and
dermal wipes for 83 homes in Arizona along the Arizona/Mexico border. The samples were
collected as part of a larger study (Arizona Border Study) that compared exposures of the
border residents to the exposures of the remainder of Arizona (National Human Exposure
Assessment Survey-Arizona (NHEXAS-Arizona)) to a large number of environmental
contaminants. The Arizona border is comprised of three, environmentally quite different
population areas. The Douglas/Naco area is mountainous, with a history of mining and
smelting. The Nogales area is primarily a border crossing, with a large amount of industry on
the Mexican side of the border. The Yuma area is highly agricultural, with a long history of
heavy pesticide use. DDT from Mexico might be used in the border area, since Mexico only
recently started to phase out the use of DDT (Environmental Health Perspectives, 1997).
METHODS
All samples were collected and analyzed using the methods and quality control procedures
specified in the Arizona Border Study Quality Systems Implementation Plan (QSIP) and
Standard Operating Procedures (SOPs). These data will be available at
http://www.epa.gov/heds/defaulthtm by October 2002. Prior to that time they are available
from the authors. The methods are briefly summarized below.
Dermal wipes were collected by having the participant wipe their hands twice with
isopropanol saturated gauze wipes (SOP UA-F-8.1). The wipes were processed by spiking
with surrogate standards, Soxhlet extracted with 10% diethylether/hexane, and cleaned up
using a Florisil solid phase extraction column (BCO-L-12.1). The analysis was performed
using GC/MS in the selected ion monitoring mode with internal standard quantitation (SOP
BCO-L-15.0).
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Floor dust samples were collected by using a vacuum cleaner with a custom sampling head to
vacuum a minimum of three-square meters in each of two rooms. If less than a total of two
grams of fine dust appeared to have been collected, additional area was vacuumed (SOP UA-
F-7.1). The dust was sieved through a 63 micrometer (no. 230) sieve and split into portions
for pesticides and metals analysis (SOP UA-L-12.0). A one gram sample of dust was spiked
with surrogate standard, sonicated with five mL of acetone, and cleaned up using a C-18 solid
phase cartridge (SOP BCO-L-14.0). The extracts were analyzed using GC/MS in the selected
ion monitoring mode with internal standard quantitation (SOP BCO-L-15,0).
Indoor air active samples were collected using a calibrated pump and a URG impactor with a
PM10 cut point and a 25 mm Teflon coated fiberglass filter and a PUF cartridge. The flow
rate was set at four liters per minute for three days (SOP UA-F-3.1). The samples were
processed by spiking the PUF cartridge with a surrogate standard, Soxhlet extracting the filter
and PUF with acetone, concentrating to one mL with Kudema-Danish glassware and cleaned
up using a C-l 8 solid phase extraction cartridge (SOP BCO-L-11). The analysis was
performed using GC/MS in the selected ion monitoring mode with internal standard
quantitation (SOP BCO-L-15.0).
Indoor air passive integrative samples were collected using Semipermeable Membrane
Devices (SPMDs). SPMDs are constructed of low-density layflat polyethylene tubing (86.5
centimeters in length) containing one ml of triolein distributed as a thin film on the inside.
The tubing is heat sealed at each end with a loop for hanging. The SPMDs are suspended
from the ceiling with cotton cord and a pushpin. Four SPMDs were deployed in different
locations in each residence for 30 days and composited for analysis. SPMDs were deployed in
only 53 of the 83 homes (SOP UA-F-27.0). Samples were dialyzed into hexane, subjected to
gel permeation chromatography and column cleanup, and analyzed by gas chromatography
with an electron capture detector (Huckins, Manuweera, and Petty, et al., 1993), (Petty,
Huckins, and Zajicek, 1993), (Petty, Huckins, and Orazio, et al., 1995).
The statistical analyses were performed using SPSS Version 9.0.1.
RESULTS
The dermal wipe, floor dust, and indoor active air samples were collected over a five day
period. The indoor air sample was initiated the first day of the period. The dermal wipes and
floor dust samples were collected at the end of the five days to reduce the potential for
contaminating the air samples with particulates disturbed during floor dust collection. The
frequency of detection of each compound in each media is given in Table 1. The most
frequently detected compound was DDE. The difference in the percent detected between the
active and passive air samplers may well be due to the difference in sampling time.
Table 1. Frequency of detection in environmental media
Dermal Wipes
Floor Dust
Indoor Air Active sampler (Pump)
Indoor Air Passive sampler (SPMD)
Percent detected
DDT
31
62
19
39
DDE
51
77
55
94
ODD
11
18
5
30
of
samples
83
83
83
53
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The concentration distributions of DDT, DDE, and DDD in the various matrices are given in
Table 2. The concentrations of DDT tend to be higher than those of DDE or DDD, even
though DDE was detected in a larger number of samples.
Table 2. Concentration Distribution of samples with detected analytes
Dermal wipes
25th percentile
50th percentile
75th percentile
90th percentile
Mean
Floor dust
25th percentile
50th percentile
75th percentile
90th percentile
Mean
DDT
N=26
0.02
0.045
0.18
0.28
0.102
DDT
N=52
0.052
0.13
0.35
1.29
0.75
DDE IDDD
N=43 N=9
p.oi b.oi
0.02 b.03
p.04 b.05
0.046
0.03
DDE
N=64
0.03
0.05
0.12
0.21
0.05
DDD
N=15
0.03
0.09
0.18
0.21 0.65
0.15 10.16
Units
ug/sample
Units
ug/g
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Indoor air,
active sampler
25th percentile
50th percentile
75th percentile
90th percentile
Mean
Indoor air,
passive sampler
25th percentile
50th percentile
75th percentile
90th percentile
Mean
DDT
N=16
1.12
1.5
3.05
7.86
2.75
DDT
N=21
115
249
720
5200
1000
DDE
N=46
0.4
0.6
0.8
1.56
0.88
DDE
N=50
42
110
202
510
210
DDD
N=4
0.6
1.85
7.67
9.4
3.37
DDD
N=16
10
15
44
530
99
Units
ng/m3
Units
ng/sample
The DDT/DDE ratios for the study samples are summarized in Table 3. The DDT/DDE ratio
is often used as an indicator of the time since the application, with higher ratios indicating
more recent applications.
Table 3. DDT/DDE ratios for study samples
Media
Dermal Wipes
Floor Dust
Indoor Air (active sampler)
Indoor Air (passive sampler)
N
19
48*
15
20
[Minimum [Maximum [Mean
0
0
0
0
2
3
79
16
8
1
3
7
.3
1.6
.4
2
3
1
2
.5
.2
.9
.1
*One outlier value removed.
DISCUSSION
The ratio of DDT to DDE is used as an indicator of the time since the DDT was applied.
Ratios in Alabama agricultural soil have been reported in the range of 0.5 to 1.35 (Earner,
Wideman, Jantunten, et al., 1999). Assuming that DDT was heavily used in Alabama until it
was banned, ratios of 0.5 to 1.35 are indicative of the type of ratio currently expected in
agricultural soil after three decades. A long-term study of DDT in Maine forest soil, where
the last application was in 1967, found ratios changing from approximately 13 in 1967 to 1.2
in 1993 (Dimond and Owen, 1996), which agrees with the Alabama data.
Overall, in the Arizona Border samples, we see a higher percentage of detects with DDE than
DDT indicating normal degradation of DDT to DDE is occurring. However, examination of
the concentration data reveals that the detected values of DDT are generally higher than the
DDE detected concentrations. This may indicate that for some homes the DDT has degraded
to below the limit of detection and thus only the DDE is detected.
The highest DDT concentrations were found in homes with the highest DDT/DDE ratios. Of
the six floor dust samples with DDT concentrations of 1.0 ug/g and greater, four of these had
DDT/DDE ratios greater than four. The highest floor dust sample concentration of 16.6 ug/g
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had a ratio of 9.7 compared to the mean concentration of 0.75 ug/g DDT and a mean
DDT/DDE ratio of 3.2. These values suggest DDT may have been used in the relatively
recent past in some of the subject homes in the Arizona border area. These ratios must be
interpreted with caution, since the reported environmental values show considerable
variability and there is very little data available on the degradation rate of DDT in the indoor
environment.
We also examined the relationship of the age of the home and the occurrence of DDT and
DDE. No significant correlations were found at the 0.05 level using the Pearson correlation.
This was somewhat surprising since one would expect DDT residues to be more prevalent in
housing constructed before the use of DDT was banned. This lack of correlation could be due
to the continued use of DDT or due to infiltration and track in of DDT and DDE residues in
soil in homes built after 1970.
CONCLUSIONS
DDT was found in the floor dust of over 60 percent of 83 homes sampled in a population-
based study along the Arizona/Mexico border. DDT and DDE residues were also found in air
samples and in wipes of resident's hands. Sporadic use of DDT may still persist in the
Arizona border region as seen in the few unusually high values of DDT in dermal wipes, floor
dust, and indoor air samples. This concept is substantiated by the handful of high DDT/DDE
ratios in these same samples.
The presence of DDT and DDE in the indoor air and the dermal wipe samples indicate that
these compounds may be volatilizing and condensing on household surfaces. This is indicated
by the dermal levels which are probably a result of surface contact and the continuing
presence of DDT and DDE in the house dust, which would tend to be depleted through air
exchange if recycling is not occurring. Volatilization rather than particle-bound distribution
is suspected due to the uptake of DDT, DDE, and DDD by the passive air sampler, which
uses vapor phase diffusion through a polyethylene membrane to retain the compounds of
interest. Particle bound material should not pass through the membrane. This is an area of
pesticide behavior in the residential environment that needs further investigation.
The levels of DDT, DDE, and DDD found in house dust in this study are similar those
reported by Camann in seven recent residential studies.(Camann, Colt, Teitelbaum, et al.,
2000). The levels are also similar to those reported in Maine forest soil (Dimond and Owen,
1996) and about an order of magnitude higher than those reported in Alabama agricultural
soil (Harner, Wideman, Jantunten, et. al,3 1999).
Potential sources of DDT, DDE, and DDD in the Arizona border region include: residential
DDT usage prior to the 1977 ban, track-in or infiltration of dust from historical agricultural
use, or from knowing or unknowing use of DDT in recent years. One potential source of
DDT use is the illegal pesticide impregnated chalk products that are occasionally sold at flea
markets and swap meets in Mexico and the U.S. These products lack proper labeling and
may contain a variety of pesticides including DDT. Consumers are instructed to draw chalk
lines on the floor to kill insects that crawl over the pesticide. This product is especially
dangerous because children may mistake it for ordinary chalk and play with it (Federighi and
Brank, 1998).
Future work will include estimating the contribution of the DDT from the residential
environment to the total DDT intake for study participants. Blood serum samples from the
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participants were also analyzed for DDT, DDE, and DDD. Preliminary results from these
analyses have a range of 0.016 to 2.65 ng/mL serum for DDT and a range from nondetect to
93.3 ng/mL for DDE. When the results are finalized, we will determine if the serum levels
are related to the residential levels found.
NOTICE
This work has been funded wholly or in part by the United States Environmental Protection
Agency and has been approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
REFERENCES
Camann, D., Colt, J., Teitelbaum, S., Rudel, R., Hart, R., Gammon, M. 2000, Presented at
SETAC 2000, Nashville, TN.
Dimond, J.B. and Owen, R.B. 1996, Environmental Pollution, 92:227-230.
Environmental Health Perspectives, 105. 1997 Accessed at:
http://ehpnetl.m'ehs.nih.gov/docs/1997/105-8/forum.html#mexico.
Federighi, V., Brank, G. 1998, California Department of Pesticide Regulation News Release
98:31.
Harner, T., Wideman, J.L., Jantunen, L.M.M., Bidleman, T.F., and Parkhurst, W.J. 1999,
Environmental Pollution, 106:323-332.
Huckins, J.N., Manuweera, G.K., Petty, J.D., MacKay, D., Lebo, J.A. 1993. Environ. Sci.
Technol., 27:2489-2496.
Petty, J.D., Huckins, J.N., Orazio, C.E., Lebo, J.A., Poulton, B.C., Gale, R.W., Charbonneau,
C.S., Kaiser, E.M. 1995. Environ. Sci. Technol., 29:2561-2566.
Petty, J.D., Huckins, J.N., and Zajicek, J.L. 1993. Chemosphere, 27:1609-1624.
Starr, H.G., Aldrich, F.D., McDougall, W.D., and Mounce, L.M. 1974, Pesticides Monitoring,
8:209-212.
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NEKL-RTP-HEASD-02-065 TECHNICAL REPORT DATA
1. Report No.
EPA/600/A-02/071
2.
4. Title and Subtitle
DISTRIBUTIONS OF RESIDENTIAL ORGANOCHLORWE PESTICIDE
RESIDUALS ALONG THE ARIZONA/MEXICO BORDER
5, REPORT DATE
SUBMITTED 1/02
6. PERFORMING ORGANIZATION
CODE
7. AUTHOR(S) G. ROBERTSON1, M. LEBOWITZ2, L. NEEDHAM3,
M.K. O'ROURKE2, S. ROGAN2, J. PETTY4, J. HUCKINS4
8. PERFORMING ORGANIZATION
REPORT No.
9.PERFORMING ORGANIZATION NAME AND ADDRESS
UNIVERSITY OF ARIZONA, TUCSON, AZ, USA
3National Center for Environmental Health, Centers for Disease
Control and Prevention, Atlanta, GA, USA
4Columbia Environmental Research Center, U.S. Geological
Survey, Columbia, MO, USA
10. PROGRAM ELEMENT No.
3910,8.2.1,8-25A,APG28,APM29
11. CONTRACT/COOP
DW14937889,68-D-99-003
12.SPONSOMNG AGENCY NAME AND ADDRESS
''U.S. Environmental Protection Agency, Las Vegas, NV, USA
13. TYPE OF REPORT AND PERIOD
COVERED
14.SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
TO BE PRESENTED AT INDOOR AlR 2002, MONTEREY, CA 6/30-7/5/02
* Contact author email: robertson.gary@epa.gov
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TECHNICAL REPORT DATA
16. ABSTRACT
THE USE OF DDT HAS BEEN BANNED FOR MANY YEARS IN THE UNITED STATES. MEXICO BEGAN A
10-YEAR PHASE OUT OF DDT IN 1997. DDT WAS BANNED IN THE U.S. PRIMARILY BECAUSE OF ITS
ENVIRONMENTAL PERSISTENCE. THUS, DDT IS STILL FOUND IN THE OUTDOOR AND INDOOR
ENVIRONMENT. WE REPORT THE RESULTS FROM SAMPLES COLLECTED IN 83 HOMES IN ARIZONA
ALONG THE ARIZONA/MEXICO BORDER. THE MEDIA SAMPLED INCLUDED INDOOR AIR, FLOOR
DUST, DERMAL WIPES, AND BLOOD SERUM. 4,4'-DDT WAS DETECTED IN 62% OF THE FLOOR DUST
SAMPLES, 19% OF THE INDOOR AIR SAMPLES, AND 31 % OF THE DERMAL WIPES. THIS MAY BE
FROM SPRAY RESIDUALS IN OLDER HOUSING STOCK, RECENT USE OF CHEMICALS OBTAINED IN
MEXICO, TRACK-IN FROM OUTDOOR USAGE, OR OTHER SOURCES. WE REPORT ON THE
CONCENTRATIONS FOUND, EXAMINE THE DISTRIBUTIONS OF OCCURRENCE OF DDT ANALOGS IN
THE VARIOUS MEDIA AND DISCUSS POSSIBLE SOURCES OF THESE OCCURRENCES.
17. KEY WORDS AND DOCUMENT ANALYSIS
A. DESCRIPTORS
Arizona, pesticides, DDT, residential exposure
B. IDENTIFIERS / OPEN
ENDED TERMS
C. COSATI
18. DISTRIBUTION STATEMENT
RELEASE TO THE PUBLIC
19. SECURITY CLASS (THIS
REPORT)
UNCLASSIFIED
20. SECURITY CLASS (THIS
PAGE)
UNCLASSIFIED
21. No. OF PAGES
7
22. PRICE
FORM AVAILABLE: NETWORK NEiGHBORHOOD\KNiGHT\GROUPS\HEASDWoRMS\TECH-FoRM-2220-l
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