7
Int. J. Hyg. Environ.-Health 208 (2005) 193–199 Pyrethroids used indoor - ambient monitoring of pyrethroids following a pest control operation Gabriele Leng a,b, , Edith Berger-Preiß c , Karsten Levsen c , Ulrich Ranft d , Dorothee Sugiri d , Wolfgang Hadnagy a , Helga Idel a a Institute of Hygiene, Heinrich-Heine-University Du¨sseldorf, Germany b Bayer Industry Services, SUA-GHA-GSS, Institute of Biomonitoring, Building L 9, 51368 Leverkusen, Germany c Fraunhofer Institute of Toxicology, Aerosol Research, Drug Research and Clinical Inhalation, Hannover, Germany d Medical Institute of Environmental Hygiene, Du¨sseldorf, Germany Received 21 January 2004; received in revised form 11 November 2004; accepted 18 November 2004 Abstract House dust and airborne particles (PM) were sampled before (T1) and 1 day (T2), 4–6 months (T3) as well as 10–12 months (T4) after a pest control operation (PCO). Cyfluthrin was applied in 11, cypermethrin in 1, deltamethrin in three and permethrin in four interiors. The pyrethroid concentrations in house dust and PM were measured by GC/MS with a detection limit for all pyrethroids of 0.5 mg/kg house dust and of 1 ng/m 3 PM for deltamethrin and permethrin and 3 ng/m 3 PM for cyfluthrin and cypermethrin. A general background concentration of permethrin (95th percentile: 5.9 mg/kg) and cyfluthrin (95th percentile: 34.9 mg/kg) in house dust was found. In general, an appropriately performed PCO lead to an increase of pyrethroids in house dust as well as in PM, in some cases up to 1 year after application. One day after the application the cyfluthrin concentration increased significantly from 0.25 (T1) to 33.8 mg/kg house dust (T2) and up to 4.9 ng/m 3 in PM. The permethrin concentration increased significantly from 4.3 to 70 mg/kg in house dust and up to 18.1 ng/m 3 in PM, deltamethrin increased to 54.5 mg/kg and 20.8 ng/m 3 and cypermethrin to 14 mg/kg and 45.7 ng/m 3 . Thereafter a continuous decrease could be observed during the time course of 1 year. After 1 year the permethrin concentration in house dust was still 1/5 of the T2 concentration, whereas for cypermethrin and cyfluthrin only 1/14 and 1/23 of the T2 concentration were found. Deltamethrin was not detected at all after T2. Moreover, the data of this study showed significant, positive correlations between pyrethroids in house dust and in airborne particles especially one day after PCO. r 2005 Elsevier GmbH. All rights reserved. Keywords: Pyrethroids; Indoor pest control operations; House dust; Airborne particles Introduction Synthetic pyrethroids like cyfluthrin, cypermethrin, deltamethrin and permethrin are often used in indoor pest control operations. Since contact to pyrethroids is reported to lead to a variety of symptoms such as ARTICLE IN PRESS www.elsevier.de/ijheh 1438-4639/$ - see front matter r 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijheh.2005.01.016 Corresponding author. Bayer Industry Services, SUA-GHA-GSS, Institute of Biomonitoring, Building L 9, 51368 Leverkusen, Germany. Tel.: +49 214 30 65679; fax: +49 214 30 21307. E-mail address: [email protected] (G. Leng).

Pyrethroids used indoor - ambient monitoring of pyrethroids following a pest control operation

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ARTICLE IN PRESS

Int. J. Hyg. Environ.-Health 208 (2005) 193–199

1438-4639/$ - se

doi:10.1016/j.ijh

�Correspond

Institute of Biom

Tel.: +49 214 3

E-mail addr

www.elsevier.de/ijheh

Pyrethroids used indoor - ambient monitoring of pyrethroids

following a pest control operation

Gabriele Lenga,b,�, Edith Berger-Preißc, Karsten Levsenc, Ulrich Ranftd,Dorothee Sugirid, Wolfgang Hadnagya, Helga Idela

aInstitute of Hygiene, Heinrich-Heine-University Dusseldorf, GermanybBayer Industry Services, SUA-GHA-GSS, Institute of Biomonitoring, Building L 9, 51368 Leverkusen, GermanycFraunhofer Institute of Toxicology, Aerosol Research, Drug Research and Clinical Inhalation, Hannover, GermanydMedical Institute of Environmental Hygiene, Dusseldorf, Germany

Received 21 January 2004; received in revised form 11 November 2004; accepted 18 November 2004

Abstract

House dust and airborne particles (PM) were sampled before (T1) and 1 day (T2), 4–6 months (T3) as well as 10–12months (T4) after a pest control operation (PCO). Cyfluthrin was applied in 11, cypermethrin in 1, deltamethrin inthree and permethrin in four interiors. The pyrethroid concentrations in house dust and PM were measured by GC/MSwith a detection limit for all pyrethroids of 0.5 mg/kg house dust and of 1 ng/m3 PM for deltamethrin and permethrinand 3 ng/m3 PM for cyfluthrin and cypermethrin.

A general background concentration of permethrin (95th percentile: 5.9 mg/kg) and cyfluthrin (95th percentile:34.9 mg/kg) in house dust was found.

In general, an appropriately performed PCO lead to an increase of pyrethroids in house dust as well as in PM, insome cases up to 1 year after application. One day after the application the cyfluthrin concentration increasedsignificantly from 0.25 (T1) to 33.8 mg/kg house dust (T2) and up to 4.9 ng/m3 in PM. The permethrin concentrationincreased significantly from 4.3 to 70 mg/kg in house dust and up to 18.1 ng/m3 in PM, deltamethrin increased to54.5 mg/kg and 20.8 ng/m3 and cypermethrin to 14 mg/kg and 45.7 ng/m3. Thereafter a continuous decrease could beobserved during the time course of 1 year. After 1 year the permethrin concentration in house dust was still 1/5 of theT2 concentration, whereas for cypermethrin and cyfluthrin only 1/14 and 1/23 of the T2 concentration were found.Deltamethrin was not detected at all after T2. Moreover, the data of this study showed significant, positive correlationsbetween pyrethroids in house dust and in airborne particles especially one day after PCO.r 2005 Elsevier GmbH. All rights reserved.

Keywords: Pyrethroids; Indoor pest control operations; House dust; Airborne particles

e front matter r 2005 Elsevier GmbH. All rights reserved.

eh.2005.01.016

ing author. Bayer Industry Services, SUA-GHA-GSS,

onitoring, Building L 9, 51368 Leverkusen, Germany.

0 65679; fax: +49 214 30 21307.

ess: [email protected] (G. Leng).

Introduction

Synthetic pyrethroids like cyfluthrin, cypermethrin,deltamethrin and permethrin are often used in indoorpest control operations. Since contact to pyrethroids isreported to lead to a variety of symptoms such as

ARTICLE IN PRESSG. Leng et al. / Int. J. Hyg. Environ.-Health 208 (2005) 193–199194

headache, dizziness, nausea, irritations of the skin andmucosa, and paresthesia (He et al., 1988; Muller-Mohnssen, 1991; Muller-Mohnssen and Hahn, 1995),an adequate exposure assessment of pyrethroids is ofconsiderable concern. In this context determination ofexternal exposure can contribute to risk assessments ofpyrethroids (Butte and Heinzow, 2002). Pyrethroidconcentrations are mainly determined in house dustsamples (Becker et al., 2002; Butte and Heinzow, 2002;Walker et al., 1999; Berger-Preiß et al., 2002). Dataobtained from such analyses were often used to evaluatethe internal dose or even the appearance of pyrethroidassociated health effects (Stolz et al., 1994). As a limitingvalue for an increased appearance of symptoms 10 mg/kg of the respective pyrethroid in house dust wassuggested (Stolz et al., 1994; Muller-Mohnssen andHahn, 1995). On the other hand, as derived from animalexperiments, values of about 5000 mg/kg were reportedto be harmless to humans (Pauluhn et al., 1996;Pauluhn, 1998). With respect to pyrethroids in air acyfluthrin concentration of 10 mg/m3 is regarded to betolerable (Pauluhn et al., 1996; Pauluhn, 1998).

As one part of an extensive study including ambientand biological monitoring combined with an assessmentof the individual health status after professional pestcontrol operations (PCOs) using a pyrethroid-contain-ing product the present paper focuses on the ambientmonitoring data (Leng et al., 2003; Hadnagy et al.,2003). The main aim was to investigate to which extentan appropriately performed professional PCO with apyrethroid-containing product leads to an increase ofthe external pyrethroid exposure. For the first timereliable data on the concentrations of several pyre-throids in house dust and airborne particles before andup for 1 year after a professionally performed PCOunder field conditions are reported here. Moreover, itwas investigated if there was an association between thepyrethroid concentration in house dust and airborneparticles.

Material and methods

Study description

The indoor PCOs were carried out by professionalpest control operators in 19 interiors (15 privatehousings and four working places) by spot-spraying ofa pyrethroid containing product because of cockroachinfestation.

In 11 interiors (nine private housings and twobakeries/restaurants) Solfac EW 50s (cyfluthrin) wasapplied, in four (three private housings and onerestaurant) KO-Konzentrat 0.4%s (permethrin), inone bakery Microcips (cypermethrin) and in three

private housings Detmol-deltas (deltamethrin). Theduration of effect of the products was about 4 h.Thereafter, the rooms were ventilated (windows wereopened or air conditioning was switched on) for 4 h.

House dust and airborne particles (PM) were sampledbefore PCO (T1) and 1 day (T2), 4–6 months (T3) aswell as 10–12 months (T4) after the PCO. At T3 17 andat T4 only 12 interiors were further investigated becausesome subjects did not want to participate in the studyany more.

Ambient monitoring

Airborne particles (PM, particles with aerodynamicdiameter smaller than 30 mm) were collected on Pallflexfilters, sampling �10 m3 at a rate of 2.6–3 m3/h(sampling device from Derenda). The sampling wascarried out according to VDI guideline 4300, page 1(VDI, 1992).

House dust was collected using a vacuum cleaner(Philips HR 8733), where the usual dust bag wasreplaced by a Soxhlet filter tube. An area of �20 cmwidth from the edge of the floor was exempted from thehouse dust sampling. The samples were analyzed at theFraunhofer-ITEM in Hannover according to the pro-tocol described by Berger-Preiß et al. (2002).

Pallflex filters were extracted three times with 10 mlethyl acetate in an ultrasonic bath. The extracts werecombined, filtered through silanized glass wool andreduced to a final volume of 1 ml by evaporation using arotary evaporator. The extracts were analysed by GC/MS without further clean-up. For the extraction of thehouse dust, a Soxhlet procedure with ethyl acetate (15 h)was used. After extraction, volume reduction andsolvent exchange to n-hexane the extracts were cleanedup on a silica gel mini-column (Merck). The silica gelwas eluted with dichloromethane/n-hexane (30:70).The solvent was changed to ethyl acetate before GC/MS analysis (GC: HP 6890, MS: Hewlett PackardHP-MSD 5973).

GC separation was carried out using a DB5.625column (length: 10–12 m; i.d.: 0.25 mm; df: 0.25 mm, J &W) and a deactivated retention gap (0.5 m length, J &W). Helium as carrier gas was used in constant flowmode. The following temperature programme was used:60 1C (1 min), 6 1C/min up to 270 1C (3 min). The sample(1 ml) was injected on column.

The HP-MSD mass spectrometer fitted with aquadrupole mass filter was used in electron impact(EI) mode (70 eV). The MSD temperatures were asfollows: transferline: 280 1C; ion source: 230 1C; quad-rupole: 150 1C. The MS system was run in the selectedion monitoring (SIM) mode. The following targetand qualifier ions (m/z) were monitored: permethrin(183.1/165.0); cyfluthrin, (206.1/226.0); cypermethrin

ARTICLE IN PRESSG. Leng et al. / Int. J. Hyg. Environ.-Health 208 (2005) 193–199 195

(181.1/209.1); deltamethrin (252.9/209.0). Quantificationof the compounds was achieved by external calibrationcurves using the underlined masses (m/z).

The detection limit (DL) in house dust was 0.5 mg/kgfor all pyrethroids. In the air (measured as airborneparticles), the DL was 1 ng/m3 for deltamethrin andpermethrin and 3 ng/m3 for cyfluthrin and cypermethrin.

Statistical analysis

Univariate distribution was characterized by themedian, mean and 95th percentile, bivariate analyseswas performed using the two-sided Wilcoxon signedrank test. Concentrations below LOD were consideredwith 1

2LOD. Correlation analysis between pyrethroid

concentrations in house dust and in airborne particleswas performed with the Spearman rank correlation testincluding all interiors. The level of significance was setat po0:05:

For all calculations, the SAS software packageversion 6.12 under Windows NT and Open VMS wasused (SAS, 1989).

The study protocol was approved by the ethicalcommittee of the Heinrich-Heine-University ofDusseldorf.

Results

Background concentrations (18 interiors)

Table 1 shows that permethrin was found ubiquitousin house dust and compared to the other pyrethroidsquite often in PM (95th percentiles: 5.9 mg/kg and23 ng/m3). Cypermethrin and deltamethrin was onlyfound sporadically whereas cyfluthrin was found in

Table 1. Background concentrations (before PCO) of pyrethroids

interiors (N ¼ number of samples above detection limit as well as me

were considered as 12

LOD for calculations)

Permethrin Cyfluthri

House dust (mg/kg)

N4LOD 17 10

Median 1.2 0.8

95th percentile 5.9 34.9

PM (ng/m3)

N4LOD 7 2

Median o 1 o 3

95th percentile 23.0 7.3

LOD house dust: 0.5 mg/kg for all pyrethroids.

LOD PM: 3 ng/m3 (cyfluthrin, cypermethrin) and 1 ng/m3 (deltamethrin, per

n.c.: not calculable.

about half of the interiors (95th percentiles: 34.9 mg/kgand 7.3 ng/m3).

Cyfluthrin application (11 interiors)

Before PCO (T1) cyfluthrin was found in five interiorsin house dust with a maximum of 34.9 mg/kg dust(Table 2). One day after the PCO (T2) cyfluthrin wasfound in all interiors. The median cyfluthrin concentra-tion in house dust increased significantly (po0:05) fromT1 (0.25 mg/kg) to T2 (33.8 mg/kg) with the highestvalue being 9120 mg/kg (second highest value: 502 mg/kg). At T3 (4–6 months later), cyfluthrin was still foundin 10 interiors with a median concentration of 4.9 mg/kg, dropping down to 1.5 mg/kg at T4 (10–12 monthslater).

At T1 airborne cyfluthrin was found in two interiors(5.2 and 7.3 ng/m3). At T2 in eight interiors cyfluthrinwas detected with a median of 4.9 ng/m3 (maximumvalue 32.8 ng/m3). At T3 cyfluthrin was found in two(7.7 and 3.6 ng/m3) and at T4 in none interior.

Cypermethrin applications (one interior)

Cypermethrin concentration in house dust and PMincreased from 0.75 mg/kg and 5.5 ng/m3 (T1) to 14 mg/kg and 45.7 ng/m3 (T2), being below the detection limits4–6 months later.

Deltamethrin applications (three interiors)

Before application deltamethrin was not found inhouse dust or PM, whereas 1 day after it was foundeverywhere in house dust and in two housings in PM.The median deltamethrin concentration increased sig-nificantly (po0:05) from T1 to T2 in house dust(median: 54.5 mg/kg; range: 35.3–67.3 mg/kg) as well

in house dust (mg/kg) and in airborne particles (ng/m3) in 18

dian and 95th percentile is shown; values below detection limit

n Cypermethrin Deltamethrin

3 3

o 0.5 o 0.5

3 2.3

1 0

o 3 n.c.

5.5 n.c.

methrin).

ARTICLE IN PRESS

Table 2. Cyfluthrin concentrations in house dust (mg/kg dust) and airborne particles (ng/m3) after Solfac EW 50s application in

11 interiors (N ¼ number of samples above detection limit as well as median, 95th percentile and maximum is shown; values below

detection limit were considered as 12

LOD for calculations)

T1 11 interiors T2 11 interiors T3 11 interiors T4 6 interiors

House dust (mg/kg)

N4LOD 5 11 10 6

Median 0.25 33.8� 4.9 1.5

95th percentile 18.2 4811 31.4 9.1

Maximum 34.9 9120 37.1 9.3

PM (ng/m3)

N4LOD 2 8 2 0

Median n.c. 4.9� n.c. n.c.

95th percentile 6.3 26.9 5.7 n.c.

Maximum 7.3 32.8 7.7 n.c.

LOD cyfluthrin: house dust: 0.5 mg/kg; PM: 3 ng/m3.

n.c.: not calculable.

T1: before PCO; T2: 1 day after the PCO; T3: 4–6 months after the PCO, T4: 10–12 months after the pest control operation (PCO)�po0:05 (T1–T2).

Table 3. Permethrin concentrations in house dust (mg/kg dust) and airborne particles (ng/m3) after KO-concentrate 0.4%s

application in four interiors (N ¼ number of samples above detection limit as well as minimum, median, 95th percentile and

maximum is shown; values below detection limit were considered as 12

LOD)

T1 4 interiors T2 4 interiors T3 4 interiors T4 4 interiors

House dust (mg/kg)

N4LOD 4 4 4 4

Minimum 1.4 32.3 13.0 11.3

Median 4.3 70.0� 28.5 14.2

95th percentile 5.8 119.5 58.3 39.3

Maximum 5.9 127.4 61.0 43.5

PM (ng/m3)

N4LOD 1 4 4 3

Minimum o1 6.5 2.7 o 1

Median n.c. 18.1� 8.9 4.9

95th percentile n.c. 34.0 15.3 20.0

Maximum 3.4 35.3 16.1 22.5

LOD permethrin: house dust: 0.5 mg/kg; PM: 1 ng/m3.

n.c.: not calculable.

T1: before PCO; T2: 1 day after the PCO; T3: 4–6 months after the PCO, T4: 10–12 months after the pest control operation (PCO).�po0:05 (T1–T2).

G. Leng et al. / Int. J. Hyg. Environ.-Health 208 (2005) 193–199196

as in PM (median: 20.8 ng/m3; range: 0.5–378 ng/m3).Later on, only in one interior very low concentrations ofdeltamethrin in house dust were found (0.75 mg/kg) andnothing in PM.

Permethrin applications (four interiors)

Table 3 shows that permethrin was detected in housedust in all four interiors before PCO. The medianpermethrin concentration in house dust raised signifi-cantly from T1 (4.3 mg/kg) to T2 (70 mg/kg) with thehighest concentration being 127.4 mg/kg. Later thepermethrin concentrations (median values) in house

dust dropped to 28.5 mg/kg (T3) and 14.2 mg/kg (T4).Regarding PM, before PCO permethrin was found inone interior (3.4 ng/m3), 1 day after spraying in all ofthem. The permethrin concentration in PM increasedsignificantly to 18.1 ng/m3 (T2). At T3 permethrin wasstill found in all interiors (median: 8.9 ng/m3) and at T4in three of them (median: 4.9 ng/m3).

Correlation analysis

The results of the correlation analysis between thepyrethroid concentrations in house dust and airborneparticles are shown in Table 4. At T2 there was a

ARTICLE IN PRESS

Table 4. Correlation analysis (Spearman) between pyrethroid

concentrations in house dust and in airborne particles (PM);

all interiors are considered

T1 T2 T3 T4

Permethrin

PM

r: �0.146 r: 0.596 r: 0.847 r: 0.399

p: 0.563 p: 0.007 p: 0.0001 p: 0.199

Permethrin

house dust

n: 18 n: 19 n: 17 n: 12

Cyfluthrin

PM

r: 0.408 r: 0.547 r: 0.287 n.c.

p: 0.093 p: 0.019 p: 0.265

Cyfluthrin

house dust

n: 18 n: 18 n: 17

Cypermethrin

PM

r: 0.504 r: 0.542 n.c. n.c.

p: 0.032 p: 0.017Cypermethrin

house dust

n: 18 n: 19

Deltamethrin

PM

n.c. r: 0.524 n.c. n.c.

p: 0.021Deltamethrin

house dust

n: 19

n.c.: not calculable.

T1: before PCO; T2: 1 day after the PCO; T3: 4–6 months after the

PCO; T4: 10–12 months after the pest control operation (PCO).

G. Leng et al. / Int. J. Hyg. Environ.-Health 208 (2005) 193–199 197

significant, positive correlation for all pyrethroids at the5% level. This holds also true for cypermethrin at T1and for permethrin at T3.

Discussion

This study presents for the first time reliable data onthe concentrations of several pyrethroids (cyfluthrin,cypermethrin, deltamethrin, permethrin) in house dustand airborne particles (PM) before and after PCOsunder field conditions with repeated measurements over1 year. Moreover, data regarding background levels ofpyrethroids were obtained in this study.

Background levels of pyrethroids

Permethrin was found in house dust of 17 out of 18interiors (95th percentile: 5.9 mg/kg). Even higherpermethrin background levels were reported by the‘‘Umweltsurvey’’ 1990/92 and 1998 (95th percentiles:10.8 and 14.5 mg/kg respectively), considering Germanhousing (Schulz et al., 1999; Becker et al., 2002). Inthese surveys woollen floor coverings or pest control

operations (private and professional spraying) areregarded as a source for permethrin exposure. In afurther study investigating the permethrin concentrationin house dust in homes with wool carpets a meanpermethrin concentration of 53.7 mg/kg house dust(90th percentile: 129.1 mg/kg) was found (Berger-Preißet al., 2002). In the present study interiors with woollenfloor coverings or pest control operations in the last sixmonths were excluded, which may explain the lowerbackground level. Obviously it seems that besidewoollen floor coverings permethrin occurs ubiquitously.Beside of permethrin, cyfluthrin was also found in abouthalf of the investigated interiors above detection limit(95th percentile: 34.9 mg/kg). The source for this couldbe a formerly performed PCO.

Regarding PM, a low background level was found forpermethrin, cyfluthrin and cypermethrin (95th percen-tiles: 23, 7.3 and 5.5 ng/m3, respectively) with the medianin all cases being below the detection limit. This differsfrom two studies dealing with the permethrin concen-trations in airborne particles of homes with wool carpets(Meierhenrich, 1997; Berger-Preiß et al., 2002). Berger-Preiß et al. (2002) found a mean permethrin concentra-tion of 2.8 ng/m3 (90th percentile: 5.8 ng/m3) whereasMeierhenrich (1997) found permethrin concentrationsbetween 2 and 230 ng/m3.

Pyrethroid concentrations one day after PCO

One day after PCO the pyrethroid concentrations inhouse dust and airborne particles were significantlyhigher than before. In 11 interiors where cyfluthrin wasapplied the median concentration of cyfluthrin was33.8 mg/kg in house dust and 4.9 ng/m3 in PM. In 4interiors permethrin was applied. Here at T2 the medianconcentration of permethrin in house dust was 70 mg/kgand in PM 18.1 ng/m3. After cypermethrin or deltame-thrin application 14 mg/kg and 54.5 mg/kg was found inhouse dust and 45.7 ng/m3 and 20.8 ng/m3 in PMrespectively.

The results of this study can be compared with twoother studies: Berger-Preiß et al. (1997) found directlyafter a controlled spot application permethrin anddeltamethrin concentrations between 150–800 mg/kg(PM: 36 mg/m3) and 50 mg/kg (PM: 2 mg/m3), respec-tively. Two days later the concentrations decreased to100 ng/m3 for permethrin and 5 ng/m3 for deltamethrin.Comparing these results with those of the present study,permethrin concentrations in house dust and PM weremuch lower in our study whereas the deltamethrinconcentration was nearly the same in house dust and fivetimes more in PM.

In the second study a spot application with Solfac EW050s (cyfluthrin) was carried out (Pospischil et al.,1994). Twenty milligram of cyfluthrin was sprayed per

ARTICLE IN PRESSG. Leng et al. / Int. J. Hyg. Environ.-Health 208 (2005) 193–199198

m2 (as company recommendation for the product) andcyfluthrin measurements in house dust were performed 3days later finding 10.4 mg/kg house dust. Directly afterthe application the mean cyfluthrin concentration in PMwas 20.5 mg/m3. Compared to these findings, in ourstudy a comparable amount of cyfluthrin was found inhouse dust but much less in PM, which can be explainedby the later sampling time point. Here again it has to beemphasized that the concentration of pyrethroids inair decreases rapidly after application (Class andKintrup, 1991; Class, 1994).

Pyrethroid concentrations 4–12 months after PCO

Pyrethroids, most of all permethrin, can be measuredin house dust months or even years after application(Berger-Preiß et al., 1997). The elimination half-life ofpermethrin in house dust is about 2 months. Consistentwith this, we also found permethrin even 1 year afterPCO in house dust (median: 14.2 mg/kg) as well as inPM (median: 4.9 ng/m3). Moreover, 1 year after PCOcyfluthrin and cypermethrin were found in six interiors(median: 1.5 mg/kg) and one (1 mg/kg) respectively. Onthe other hand the deltamethrin concentration wasbelow detection limits at T3 and T4.

Correlation analysis

From the practical point of view sampling and samplepreparation of pyrethroids in house dust is much easierthan in airborne particles. Therefore, it was investigatedin this study if there is a correlation between these twomatrices. One day after PCO there was a significantpositive correlation for all pyrethroids. For cyfluthrinand cypermethrin this was also true at T1 and forpermethrin at T3. In contrast, no correlation betweenpermethrin in airborne particles and in house dust inhomes with woollen textile floor coverings were foundby Berger-Preiß et al. (2002). This may be due to areduced release from bound permethrin into the air.Although there is a positive correlation betweenpyrethroids in house dust and PM, it has to beemphasized that the concentrations in airborne particlesare much lower than in house dust.

Conclusion

Our results showed that an appropriately performedPCO leads to an increase of pyrethroids in house dustand airborne particles additionally to a general back-ground level of permethrin and cyfluthrin in house dust.With respect to permethrin and cyfluthrin the levelremained elevated in house dust for 1 year, whereas thelevel of cypermethrin and deltamethrin were negligible,

indicating a lower degradation of permethrin in contrastto the other pyrethroids.

For exposure assessment the determination of pyre-throids in house dust should be further recommended.Nevertheless, it is not useful to claim a limiting value of1 or 10 mg/kg house dust following PCO (Stolz et al.,1994; Muller-Mohnssen and Hahn, 1995), because ourdata showed that this is not reasonable from thepractical point of view. Measurements of PM are onlyuseful up to 1 day after pyrethroid application, later onno pyrethroids are detectable any more. Neither housedust nor PM measurements are adequate to getinformation about the internal burden of the exposedsubjects. For this purpose, biological monitoringshould be performed (Berger-Preiß et al., 2002; Lenget al., 2003).

Acknowledgement

This study was supported by BMBF and IVA (07INR 30 A/B). The authors thank the consultants of thestudy Prof. Altenkirch (Berlin, FRG), Prof. Angerer(Erlangen, FRG), Prof. Jockel (Essen, FRG) Dr. Leist(Frankfurt, FRG), Dr. Lewalter (Leverkusen, FRG)and Dr. Miksche (Leverkusen, FRG) for intensivediscussion.

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