Assessment of indoor exposure to Perchloroethylene - CiteSeerX

JOURNAL OF PREVENTIVE MEDICINE AND HYGIENE 1999; 40: 43-48

Assessment of indoor exposure to Perchloroethylene (PCE) in dry-cleaners’ family members G. AGGAZZOTTI, E. RIGHI, G. FANTUZZI, G. PREDIERI, F. GOBBA Department of Hygiene, Microbiology and Biostatistics, University of Modena and Reggio Emilia

Key words Perchloroethylene • Dry-cleaners’ houses • Biological monitoring

Summary Perchloroethylene (PCE) is present inside private apartments of dry-cleaners at levels significantly higher than those measured in control homes. The aim of the study was to evaluate PCE exposure for dry-cleaners’ family members: indoor air samples were collected in 20 dry-cleaners homes and in 22 control homes. Biological monitoring (alveolar air sampling) was also performed in 26 dry-cleaners, 18 family members and 28 control subjects. PCE levels inside dry-cleaners’ homes appeared significantly higher than those observed in control homes (geom. means: 219

and 4 µg/m3, respectively). PCE values in alveolar air from drycleaners’ family members spending some time daily in their relatives premises resulted not significantly different from those observed in dry-cleaners (geom. means: 3,055 and 4,988 µg/m3, respectively). Family members usually not visiting the premises showed lower values: nevertheless they were significantly higher than those observed in control subjects (geom. means: 306 and 6 µg/m3, respectively). Overall, dry-cleaners’ family members are exposed to PCE at higher levels than the general population.

Introduction

over, clothes subjected to commercial dry-cleaning with PCE can contribute to indoor pollution 18-21. A previous survey in the city of Modena (Northern Italy) assessed occupational and indoor exposure to PCE and potential health effects for dry-cleaners and their family members. Indoor air levels of PCE inside the private apartments of dry-cleaners, all located far away from dry-cleaning shops, were significantly higher than those measured in control homes. Biological monitoring, performed by end-expired (alveolar) air sampling, disclosed significantly higher PCE levels in family members of dry-cleaners than in control subjects 22 23. The aim of the present study was to evaluate the levels and assess the changes over time, if any, in the exposure to PCE for dry-cleaners’ family members. Thus, two years later, another survey was carried out in the homes and in the subjects involved in the earlier study.

Perchloroethylene (PCE) is a chlorinated solvent used in different industrial processes, such as the production of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113), metal degreasing and, mainly, dry-cleaning, where it has replaced trichloroethylene. About 75% of all dry cleaners all over the world use PCE as a cleaning fluid and it is estimated that several million people are employed in dry-cleaning world wide 1. There is evidence for a consistently positive association between occupational exposure to PCE and risk of cancer, even though cohort studies are few: the International Agency for Research on Cancer (IARC) classifies dry-cleaning activity as possibly carcinogenic to humans (Group 2B) and PCE as probably carcinogenic to humans (Group 2A) 1. PCE shows little acute toxicity in humans and experimental animals and few reports have investigated chronic exposure. However impaired sperm quality and fertility in males and an increase in the rate of spontaneous abortions have been observed in occupationally exposed subjects 2-5. Recent studies suggest that occupational chronic low level exposure may also cause early renal disturbance, and subclinical neurological effects, e.g. colour vision loss 6-8. Few studies have dealt with environmental exposure to PCE in the general population. This exposure can occur from many sources: environmental air, drinking water, and fatty foods 9-12. A major source of non occupational exposure to PCE is dry-cleaning itself: individuals living near dry-cleaning premises are exposed to higher levels of PCE than the general population 13-16. Also visiting dry-cleaning premises is an important source of exposure for the general population 17. More-

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Materials and methods In the period 1992-1993 110 dry-cleaning establishments were operating in the city of Modena, Northern Italy. The first survey involved 28 randomly selected shops (∆ = 0.05, power = 0.9), 25 apartments where drycleaners and their family members were living and 29 control homes. All compliant subjects living inside these environments underwent biological monitoring (alveolar air sampling). 22 23. The present study was carried out two years later: according to the owners’ consent, 20 out of the 25 previously investigated dry-cleaners’ homes, and 22 control homes out of 29 which were studied in the first survey, were investigated. All apartments were located far away from dry-cleaners’ establishments.

G. AGGAZZOTTI, E. RIGHI, G. FANTUZZI, ET AL.

Both in the first and second survey the monitoring was performed in the middle of the working week. PCE in ambient air inside the apartments was evaluated both by active sampling, starting at 9 p.m. and lasting at least two hours, and by spot samples, collected in the dining room and/or bedroom within the breathing zone (1.5 m in height) in the evening (9 p.m.) and on the following morning (7 a.m.). At the same times, alveolar air samples were collected from most of the subjects involved in the previous survey: 26 out of 33 dry-cleaners, 18 out of 23 family members living with them and 28 out of 35 subjects living in the control homes were checked for a second time. A detailed questionnaire was prepared to gather information on personal data and occupational and/or leisure activities in order to identify any possible exposure to PCE for all the subjects who were enrolled in the study. The main characteristics of the subjects involved in the study are reported in Table I. The occupational exposure of the dry-cleaners was also evaluated: environmental air sampling was performed by passive dosimeters inside the shops during the same day in which the sampling at home started. Inside dry-cleaners’ and control homes spot samples of ambient air were collected in screw-capped 40-cm3 glass vials equipped with silicone-faced septa. Active sampling was performed using a SIPIN sampling pump (mod SP-1, SIPIN Co, Inc, New York, USA) and air samples were collected using active charcoal tubes at a flow rate of about 200 cm3/min for 2 hours. Alveolar air sampling was performed using 34 cm3 oneway glass tubes fitted with two valves: subjects were asked to breath normally into the tube with open valves and to close the valves at the end of exhalation. In dry cleaning establishments, environmental PCE levels were measured by personal passive dosimeters in the form of personal sampling badges (TK-200 charcoal badge, Zambelli, Italy) which were worn by the drycleaners in the breathing zone. A badge was used during the morning shift and another during the afternoon shift in order to avoid saturation of the charcoal. All samples were analysed by gas chromatography using a gas chromatograph Varian 3400 equipped with a 63 Ni Electron Capture Detector (ECD) connected with a Merck Itaki D 2000 chromatointegrator. Gaschromatographic analysis was performed according to the NIOSH method 24. Spot samples of ambient air and alveolar air samples were analysed by direct injection into the gas chromatograph using a gas-tight syringe (HAMILTON). PCE adsorbed on the charcoal dosimeters (passive and active sampling) was desorbed with 5 ml of carbon disulphide and then diluted in n-pentane before gaschromatographic analysis. The concentrations of PCE as evidenced by passive sampling were expressed as 8 hours Time Weighted Average (8-h TWA) levels. The presence of PCE was confirmed by gas chromatography mass spectrometry (GC-MS), using a Varian 3400 gas chromatograph and a Finnigan Mat SSQ710A mass spectrometer.

Tab. I. Main characteristics of the subjects involved in the study.

Subjects

Dry cleaners Dry cleaners’ family members Control subjects

N.

Gender (%)

Age (years)

M

F

Mean

26 18

21 83

79 17

40 31

24-54 6-53

28

37

63

34

7-66

Range

The external standard method for calibration was chosen, given the well known difficulties in applying the internal standard method to direct gas analysis: the lower limit of detection was 1 µg/m3 of PCE. More detailed information on the analytical method is reported elsewhere 22-23. Regarding to statistical analyses, due to the skewed distribution of the data, non-parametric tests were carried out, including the Wilcoxon rank test for paired observations, Spearman’s rank correlation, Kruskal-Wallis test and Mann-Whitney U test. Analyses were performed using the statistical package SPSS/PC 25.

Results Table II compares the levels of PCE measured by spot sampling inside dry-cleaners’ homes and control homes in survey I and in survey II. In both surveys PCE environmental levels in dry cleaners’ homes resulted significantly higher than those observed in control homes (Mann Whitney U tests: p < 0.001). Moreover, the ranges of PCE levels in ambient air observed in survey I and II resulted very similar, both in dry cleaners’ and control homes, without any statistically significant difference across time (Wilcoxon rank tests for paired samples, p = n.s.). In dry-cleaners’ houses active sampling disclosed PCE values ranging from 10 to 851 µg/m3 (geom. mean: 77 µg/m3; median: 62 µg/m3). These levels resulted highly correlated with the values of PCE as measured by spot sampling in the same environment at 9 p.m. (rs = 0.63, p < 0.005), and at 7 a.m. on the following morning. (rs = 0.68, p < 0.005). Furthermore, no significant differences appeared between PCE levels in dry-cleaners’ houses observed by spot sampling in the evening and on the following morning (geometric means: 242 vs 195 µg/m3, respectively; Wilcoxon rank test for paired samples, p = n.s.). Occupational exposure inside dry-cleaning premises was measured by personal passive sampling and showed values, expressed as 8 h TWA, ranging from 800 to 150,000 µg/m3 (geom. mean: 19,300 µg/m3; median 22,000 µg/m3). These values correlated both with the levels evidenced by active sampling in the corresponding dry cleaners’ homes (rs = 0.73, p < 0.001) but also with spot sampling values measured in the evening and

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PERCHLOROETHYLENE EXPOSURE IN DRY-CLEANERS’ FAMILIES

Tab. II. PCE environmental levels evidenced by spot sampling in dry-cleaners’ and control homes, Modena, Northern Italy.

n.

PCE in ambient air (µg/m3) Geom. mean Median

Min-Max

Mann-Whitney U test

SURVEY I: Dry-cleaners’ homes Control homes

25 29

344 6

300 6

25-9,600 1-56

p < 0.001

SURVEY II: Dry-cleaners’ homes Control homes

20 22

219 4

179 6

9-8,100 1-47

p < 0.001

on the following morning (rs = 0.57, p < 0.05 and rs = 0.58, p < 0.05, respectively). In the control homes, active sampling showed PCE values ranging from 1 to 46 µg/m3 (geom. mean 9.8 µg/m3; median: 11.2 µg/m3); as expected these values were significantly lower than those observed in dry cleaners’ homes (Mann-Whitney U test, p > 0.01). The significant correlation between values from active sampling and spot samples in the evening and in the following morning was also confirmed in this group of homes (rs = 0.94 p < 0.001; rs = 0.96 p < 0.001): similarly, no significant difference was observed between PCE mean values collected in the evening and on the following morning (Wilcoxon rank tests for paired samples, p = n.s.). Regarding to biological monitoring, on the basis of the data collected by the questionnaire, family members of dry-cleaners were divided in two separate groups: subjects who did not usually spend time inside their relatives’ premises, and subjects who used to stay at least one hour daily in the shop. No other occupational or recreational activity related to a possible exposure to PCE was evidenced by the questionnaire in dry cleaners’ family members and in control subjects. Table III summarises PCE in alveolar air samples collected from dry-cleaners, their family members attending dry-cleaners’ shops daily, those not usually attending the shops and control subjects in surveys I and II. In agreement with survey I, the differences among the alveolar air levels in the different groups of subjects were confirmed as statistically significant (KruskallWallis test, p < 0.001). As expected, PCE levels in alveolar air samples collected from dry-cleaners were significantly higher than those measured in samples from family members not attending the premises and from control subjects (Mann Whitney U tests; p < 0.001). However, PCE levels in alveolar air collected from subjects spending one or more hours a day inside the premises were not significantly different from those observed in dry-cleaners (Mann-Whitney U test; p = n.s.). Moreover, even though the concentrations in family members never attending the premises were significantly lower than those observed in dry-cleaners and in family members frequenting the shops, they were significantly higher than those evidenced in control subjects (Mann-Whitney U test; p < 0.001). 45

In agreement with environmental data, the biological monitoring of PCE did not show any significant difference, on the average, between the concentrations measured in surveys I and II within each group (Wilcoxon rank tests for paired samples, p = n.s). Also the mean values of PCE in samples collected in the evening did not result significantly different from those collected on the following morning (Wilcoxon rank tests for paired samples, p = n.s). PCE levels in alveolar air samples collected from drycleaners at home after the working day correlated with the indoor values of PCE inside their own shops (rs = 0.68, p < 0.001 for the evening samples and rs = 0.67, p < 0.001 for the samples collected at home on the following morning). PCE in alveolar air samples from subjects not visiting the premises highly correlated with the indoor values observed in their homes, both in the evening (rs = 0.80, p < 0.05) and on the following morning (rs = 0.96, p < 0.01): the same correlation was evidenced between values of PCE in control subjects and those of ambient air inside control households (rs = 0.61 p < 0.001; rs = 0.76, p < 0.001).

Discussion This study confirmed that PCE inside dry-cleaners’ homes can be detected at levels significantly higher than those measured inside control homes. Moreover, the maintenance of similar ranges of environmental values inside these homes as observed in surveys I and II and in samples collected in the evening and in the following morning, suggests that PCE levels in dry-cleaners’ houses tend to remain at steady high concentrations across time. The evaluation of the exposure over time made by active sampling showed a trend really similar to that observed by spot sampling. This suggests that both measurements are good estimators of PCE exposure. According to Thompson and Evans (1993) the State of New York recommends an average ambient air level of PCE in a residential community not exceeding 250 µg/m3 for adults and 100 µg/m3 for children 26. In Germany the recommended standard value for indoor PCE concentration in residential areas is 100 µg/m3 7. In our


Tab. III. PCE in alveolar air samples collected from dry-cleaners, their family members and control subjects inside their homes, Modena, Northern Italy.

Subjects N. SURVEY I: Dry-cleaners Family members visiting dry-cleaners’ Family members not visiting dry-cleaners’ Control subjects SURVEY II: Dry-cleaners Family members visiting dry-cleaners’ Family members not visiting dry-cleaners’ Control subjects

PCE in alveolar air (µg/m3) Geom. mean Median

Min-Max

33 6

6,561 4,111

6,050 4,400

180-56,000 200-26,000

17

272

325

30-5,400

35

8

7

1-113

26 5

4,988 3,055

5,225 4,445

227-32,185 680-6,110

13

306

200

26-5,040

28

6

6

1-45

study, PCE levels inside control homes were all below these standards suggesting that the general population is not exposed to PCE to a great extent. To be noted, however, that in the 65% of dry-cleaners’ homes investigated indoor PCE levels exceeded the value of 100 µg/m3 recommended in Germany. Biological monitoring confirmed that PCE levels are higher in dry-cleaners’ family members than in the general population. Moreover, in this group of subjects two different sources of exposure were identified. In family members spending time daily inside their relatives’ premises, PCE levels in alveolar air were not statistically different from those observed in dry-cleaners, suggesting that this is their main source of PCE exposure. In family members not usually frequenting their relatives’ premises, the observed correlation between PCE values inside the apartments and in alveolar air samples suggests that indoor PCE levels represent the main source of exposure for these subjects. The relationship between indoor PCE concentrations inside dry-cleaners’ premises and those measured inside their homes indicates that the presence of PCE at home is due to the dry-cleaning activity of one or more members of the family rather than the location of the apartments which were all far from dry-cleaners’ premises. Moreover, information gathered from each subject excluded other forms of exposure. Dry-cleaners could introduce PCE into their apartments in two main ways: via their clothes and via their exhaled air. Freshly dry-cleaned garments can release different amounts of PCE for many hours after processing, depending on the fabric and the dry-cleaning procedure 18-21. A similar pathway can be supposed for the clothes worn by dry-cleaners, which could adsorb PCE inside the workplace and then release it inside their homes. The correlation between PCE in alveolar samples collected from dry-cleaners at home and PCE levels ex-

Kruskal-Wallis test

p < 0.001

p < 0.001

pressed as 8-h TWA observed inside their premises suggests that dry-cleaners could introduce PCE at home also by exhaling it. This way of release could be sufficient to raise the PCE concentration at home. Recently a simulation was carried out using a physiological-based pharmacokinetic (PBPK) model for PCE and taking into account an occupational exposure to levels below 339,000 µg/m3 corresponding to the TLV-TWA occupational guidelines recommended by International Conference of Governmental Industrial Hygienists until 1992: this model suggests that workers’ body burden could explain elevated home levels of PCE 26-27. The potential risk for health related to the PCE exposure for dry-cleaners’ family members is not easy to quantify. Up to now studies have only considered the possibility of exposure to PCE by breast-feeding for dry-cleaners’ infants. Schreiber (1993), using an appropriate PBPK model, calculated that PCE levels in breast milk samples collected from exposed women could range from 857 to 8,440 µg/l determining an increased lifetime cancer risk for their infants ranging from 5.8 x 10-5 to 6 x 10-4 28. Recently the effects of chronic low-level PCE exposure on functions of the Central Nervous System (CNS) were measured by Altman et al. (1995) in 14 subjects neither occupationally exposed, nor dry-cleaners’ relatives, living in the neighbourhood of dry cleaning shops with a mean residential time of 10.6 years 7. The authors found that indoor median value in the neighbourhood of dry-cleaning premises was of 1,360 µg/m3, while in control homes the same value was 1.8 µg/m3. Some CNS functions, such as vigilance, reaction time and visual memory, were significantly impaired in subjects living close to a dry cleaning facility if the exposure lasted for several years: the authors concluded that PCE exposure might affect these functions. Further research could address other potential neurotoxic effects induced by PCE exposure. For instance, we recently identified a significant subclinical dose-related

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colour vision loss in a sample of dry-cleaners occupationally exposed to PCE in the workplace at levels well below the current occupational guidelines recommended by ACGIH (170,000 µg/m3 8-h TLV-TWA) 8 27. As similar PCE levels were found inside some of the homes investigated in this study, it would be of public health interest to assess potential neurotoxic effects in dry-cleaners’ family members.

Conclusions This study suggests that dry-cleaners’ family members

belong to a group at higher risk of PCE exposure than the general population and that that risk tends to be steadily high over time. PCE exposure may result from short stays inside their relatives’ dry-cleaning premises, but mostly from PCE levels in their homes which are higher than those in the general indoor environment. Further research on the potential health effects, for example neurotoxic ones, of PCE exposure should be carried out in these subjects, especially in the chronically ill ones, the elderly, infants and pregnant women who spend the majority of their time inside their homes.

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■ Acknowledgements This work was supported by a grant (n. 796 D.M. 15/9/97) of the Italian Ministry of Labour (Ministero del Lavoro e della Previdenza Sociale – Direzione generale dei rapporti di lavoro). The authors are indebted to the Dry Cleaning Trade Associations and to the owners and employees of the dry-cleaning premises of in the city of Modena who participated in our study. ■ Correspondence: prof.ssa Gabriella Aggazzotti, Department of Hygiene, Microbiology and Biostatistics, University of Modena and Reggio Emilia, via G. Campi 287, 41100 Modena, Italy – Phone +39 059 428301, Fax +39 059 428340.

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