Article pubs.acs.org/est
Risk Assessment of Human Exposure to Bioaccessible Phthalate Esters via Indoor Dust around the Pearl River Delta Yuan Kang,†,‡ Yu Bon Man,‡ Kwai Chung Cheung,‡ and Ming Hung Wong*,‡ †
School of Chemistry & Environment, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, Higher Education Mega Center, Guangzhou 510006, People's Republic of China ‡ Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong, People's Republic of China S Supporting Information *
ABSTRACT: There is limited information on the bioaccessible fractions of phthalate esters in indoor dust in order to estimate human exposure. In the present study, workplace dust and settled house dust samples from Hong Kong, Shenzhen, and Guangzhou, the three major cities scattered around the Pearl River Delta (PRD) were collected. Chemical analyses showed that the phthalates in workplace dust ranged from 144 to 1810 μg/g, with dust from shopping malls containing the highest level, and in home dust ranged from 181 to 9240 μg/g. The most abundant phthalate ester found was bis(2ethylhexyl) phthalate (DEHP) in both workplace dust and home dust, followed by di-n-butyl phthalate (DBP) and di-iso-butyl phthalate (DIBP). Principal Components Analysis (PCA) indicated that indoor dust around PRD showed similar phthalate esters patterns of composition. A significant correlation was observed between total phthalate esters concentrations in home dust and the number of year of house construction (p < 0.05). The oral bioaccessibility of phthalate esters in indoor dust ranged from 10.2% (DEHP) to 32% (DMP). Risk assessment indicated that the dominant exposure routes varied in different phthalate esters exposure profiles and the dermal contact exposure pathway was identified as an important route for indoor DEHP exposure.
1. INTRODUCTION Phthalate esters are used as plasticizers in many household and industrial products including: plastic toys, personal care products, vinyl flooring, foods, polyvinyl chloride (PVC) tubing, and building materials.1,2 Di-(2-ethylhexyl) phthalate (DEHP), due to its low cost, is mainly used in PVC production. Dibutyl phthalate (DBP) and diethyl phthalate (DEP) are extensively used in personal care products, such as pharmaceutical coatings and cosmetics. Benzyl butyl phthalate (BzBP) is ubiquitously used in the production of foamed PVC, which is mostly used in floorings.3 The widespread use of phthalate esters in household and industrial products leads to their ubiquity in the environment. Human exposure to phthalate esters can occur through three major pathways including inhalation, dermal contact, and ingestion including dietary intake and dust ingestion.4,5 A scenario-based exposure model used for the assessment of sources of phthalate exposure among Europeans showed that dermal contact of consumer products was the major source of exposure to dimethyl phthalate (DMP), diethyl phthalate (DEP), and benzyl butyl phthalate (BzBP), whereas dietary intake dominated the source of exposure to di-n-butyl phthalate (DBP), di-iso-butyl phthalate (DIBP), and bis(2-ethylhexyl) phthalate (DEHP).5 However, nondietary intake of indoor dust has also been indentified as a significant exposure pathway for humans due to the high concentration of phthalates in indoor dust.3 © 2012 American Chemical Society
Animal studies showed that prenatal exposure to phthalate esters was associated with various reproductive and developmental effects. Prenatal exposure to DBP reduced fertility, leydig and sertoli cell function, anogenital distance in exposed offspring, and fetal serum testosterone (T) levels.6−8 A positive relationship between the indoor phthalate esters exposure and asthma and allergic symptoms has been observed in humans,9 while a negative relationship between environmental phthalate esters exposure and intelligence has been noted in child behavior.10 Phthalate esters can be easily released into the indoor environment due to the fact that they are not chemically bound to the consumer products. Phthalate esters have been found in indoor environment such as household dust around the world including Denmark,11 Norway,12 Sweden,13 and the U.S.14 However, information about phthalate ester pollution in the indoor environment and the magnitude of human exposure in P.R. China, especially around the Pearl River Delta is limited. In addition, the human exposure to phthalate esters considering the bioaccessibility is seldom reported. The major objectives of this study were (1) to investigate the phthalate esters levels in indoor dust of different workplaces Received: Revised: Accepted: Published: 8422
January 30, 2012 July 11, 2012 July 13, 2012 July 13, 2012 dx.doi.org/10.1021/es300379v | Environ. Sci. Technol. 2012, 46, 8422−8430
Environmental Science & Technology
Article
on the product label, the number of electronic appliances, the number of hours each week the electronic appliances were left on, recent home renovation, and carpet coverage on the floor. 2.2. Sample Extraction and Purification. Samples were spiked with 250 ng of internal standards (acenaphthene-d10, phenanthrene-d10, chrysene-d12, and perylene-d12) and allowed to equilibrate for 3 h at room temperature. Sieved dust samples (0.05−1 g) were extracted with 100 mL acetone/ dichloromethane/n-hexane (1:1:1, v/v/v) in a Soxhlet apparatus for 18 h. The extracts were concentrated to 2 mL. Afterward, the concentrated extract was cleaned up using an activated copper/sodium sulfate anhydrous/florisil column and eluted with 100 mL n-hexane.17 The eluant was concentrated to 1 mL. 2.3. GC/MS Analyses. The sample extracts were analyzed by Agilent Technologies 6890A GC system and 5973C inert Mass Selective Detector (GC-MS) EI with 30 m HP-5MS column (0.25 mm diameter and 0.25 μm film thickness). The following 13 phthalate esters investigated in the present study were as follows: dimthyl phthalate (DMP), diethyl phthalate (DEP), di-n-propyl phthalate (DPRP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DBP), bis(2-methoxyethyl) phthalate (DMEP), di-n-hexyl phthalate (DHP), butyl benzyl phthalate (BBP), di-2-ethylhexyl phthalate (DEHP), dicyclohexyl phthalate (DCHP), di-n-octyl phthalate (DnOP), dinonyl phthalate (DNP), and di-iso-decyl phthalate (DiDP) in the order of retention times. Phthalate esters were confirmed by three criteria: (1) GC retention times matched (±0.05 min) those of standard compounds; (2) qualifier to target ratios (±20%) matched those of standard compounds; and (3) signalto-noise ratio was greater than 3. 2.4. Bioaccessibility of Phthalate Esters Determination in Indoor Dust. The physiologically based in vitro digestion test was performed according to the methods described in Ruby et al.;18 Tang et al.;19 and Kang et al.,20 with slight modification. A 1-h gastric empty time and 4-h small intestinal transit time were selected. Gastric solution used for the test containing 0.25 g of pepsin (Sigma-Aldrich, U.S.), 17.5 g of NaCl, 1 g of citrate, 1 g of malate, 0.85 mL of lactic acid, and 1 mL of acetic acid in 2 L of deionized water was prepared, with pH adjusted to 1.5 with 6 M HCl. 0.4 g of dust was added into 40 mL of gastric solution and the mixture was shaken at 37 °C for 1 h. Afterward, the mixture was centrifuged at 7000 × g for 10 min and the supernatant was filtered through a 0.45 mm glass fiber filter. Then, 30 mL of the original gastric solution was added to suspend the pellets in the centrifuge tube. The thus obtained resuspended dust pellet was added to fresh gastric solution and was modified to small intestinal solution by adjusting the pH to 7.0 with NaHCO3 solution followed by adding 0.2 g of porcine bile extract (Sigma-Aldrich, U.S.) and 0.04 g of porcine pancreatin (Sigma-Aldrich, U.S.). After shaking for 4 h at 37 °C, the mixture was centrifuged at 7000 × g for 10 min and the supernatant was filtered though a 0.45 mm glass fiber filter. The filtrate (gastric and intestinal) was both extracted with 40 mL n-hexane/acetone (3:1, v/v) for 10 min in a 250 mL separatory funnel. Extraction with 40 mL of n-hexane was carried out two more times. All the extracts were combined into one mixture extract, which was dried with 5 g of anhydrous sodium sulfate. The extract was reduced to 2 mL using a rotary evaporator and purified by Florisil cleanup method.17 The solution was then concentrated to 200 μL for phthalate esters analyses. Deuterated PAHs (acenaphthened10, phenanthrene-d10, chrysene-d12, and perylene-d12) were
(workplace dust) from Hong Kong, and of residential homes (home dust) of three major cities, Guangzhou, Shenzhen, and Hong Kong in the Pearl River Delta (PRD); (2) to examine the relationships between phthalate esters pollution in indoor dust and the household attributes; (3) to analyze the bioaccessibility of phthalate esters in indoor dust; and (4) to estimate the human health risks associated with the three exposure pathways via indoor dust.
2. MATERIALS AND METHODS 2.1. Sampling and Preparation. Workplace dust sample collection was described in detail in our previous study.15 Briefly, air-conditioner filter dust samples were collected from 6 types of buildings: commercial offices (n = 20), secondary schools (n = 4), shopping malls (n = 5), hospitals (n = 16), electronic factories (n = 6), and manufacturing plants (n = 4) (Table 1). Workplace dust samples were collected using a Table 1. Detailed Information of the Sampling Sites sampling sites
sample numbers
commercial office secondary school shopping mall hospital electronic factory
20
manufacturing plant
4
house
23
4 5 16 6
detail information about sampling sites located in the commercial building; commercial area; air-conditioner filters dust residential area; air-conditioner filters dust commercial area; air-conditioner filters dust residential area; air-conditioner filters dust assembling electronics equipment such as computer; industrial area; air-conditioner filters dust all producing furniture, toys and textiles; the machine in the plant using diesel for electric power; industrial area; air-conditioner filters dust all samples collected from house floor were distributed in Guangzhou (n = 5); Shenzhen (n = 5); and Hong Kong (n = 13); floor dust
vacuum cleaner (Black & Decker Dustbuster, U.S.) on the air conditioner filter. To avoid cross contamination, the vacuum cleaner bag was changed after each sample collection. Settled home dust samples were collected from house floors by 23 volunteers using vacuum cleaners. These homes were located in Guangzhou (n = 5), Shenzhen (n = 5), and Hong Kong (n = 13) of PRD. The volunteers were recruited through the Internet or random visits. About 20% of all people contacted agreed to dust sampling (n = 23). The dust retained on the airconditioner filter would reflect the indoor air quality and also the properties of indoor dust, because the air conditioner recirculates the air through the filter.16 Therefore, dust samples from air-conditioner filters in different workplaces were collected to examine the potential human health impacts of the workers. Home dust samples were collected from the floor, due to the fact that there was only a limited amount of dust retained in air-conditioner filters in houses, and the preschool children would be affected by playing on the floor. Therefore, floor dust samples were collected from houses. All dust samples were filtered through a stainless-steel sieve ( 0.05), possibly due to the large standard deviations and different sample sizes among different groups. The shopping malls (range: 1070 to 1660 μg/g; geometric mean: 1202 μg/g) and manufacturing plants (range: 385 to 1810 μg/g; geometric mean: 954 μg/g) were more contaminated with phthalate esters compared to other workplaces, which may be due to costume, textile, and plastic toys containing high phthalate esters.30 The costume and toys are sold in the shopping mall, whereas the textile and toys are produced in the manufacturing plants (Table 1). The median of total phthalate esters concentration of secondary schools dust (967 μg/g) was higher than that (500 μg/g) obtained from primary school and daycare center classrooms dust from the floor in Denmark,31 but lower than that (3214 μg/g) obtained from schools classroom floor in Denmark.12 It should be noted that the air filters may retain
IngR = ingestion rate of indoor dust (mg/day). For adults and preschool children, the high dust ingestion rates of 0.11 and 0.2 g/day, respectively, 23 were considered. In addition, the moderate dust ingestion rate of 0.56 × 10−3 g/day and 0.05 g/ day were considered for adults and preschool children, respectively.23 F is the fraction of time spent at workplace or home in a day. A value of 33% was used for time spent in the workplace for adults. For preschool children, 12 h (50%), 8 h (33%), and 4 h (17%) were used for time spent in daycare center, home, and outdoors, respectively. IRinhalation is the inhalation rate (children: 10 m3/day; adults: 20 m3/day).24 SA is the dermal exposure area (children: 2800 cm2, area including face, forearms, and hands; adults: 3300 cm2, area including face, forearms, hands and lower legs).22 AF is the dermal adherence factor (children: 0.2 mg/cm2; adults: 0.2 mg/cm2).22 ABS is the dermal adsorption fraction. There was no available ABS of phthalate esters. European Commission 25 suggested that if appropriate dermal penetration data are available for the rat in vivo and for the rat and human skin in vitro, the in vivo dermal absorption in rats may be adjusted to provide the in vivo 8424
dx.doi.org/10.1021/es300379v | Environ. Sci. Technol. 2012, 46, 8422−8430
Workplace indicated all the different workplace samples tested into one category. LOQ of each phthalate ester was 15 ng/g. ELCF, MANP, HOSP, COMO, SCHL, and SHPM represent electronic factory, manufacturing plant, hospital, commercial office, secondary school, and shopping mall, respectively.
house
workplacea
SHPM
SCHL
COMO
HOSP
MANP
smaller particles from the air and/or sorbing analytes with higher vapor pressures, and therefore the properties of the dust retained by air-conditioners would be different from the floor dust. In addition, the different size fractions of the two types of dust may affect their phthalate ester concentrations. Nevertheless, the relatively high phthalate esters contamination in the schools around the world seems to be a concern. For other workplaces including hospitals, commercial offices and electronic factories, comparisons cannot be made with other countries due to the lack of the relevant studies. Our study indicated that the phthalate esters contamination in these workplaces was similar to that in the secondary schools in the present study, which may be due to that the similar electronic appliances or furniture were decorated in these workplaces such as secondary schools and commercial offices, and similar anthropogenic activities such as printing happened in these work places. 3.2. Phthalate Esters Profiles in Workplace Dust. Figure S2 (Supporting Information) illustrates the phthalate esters profiles observed in different workplaces. DEHP and DBP were the predominant compounds accounting for 54.2− 90.1% and 3.2−27.1% of the total phthalate esters, respectively, followed by DiBP and BBP (Figure S2A−F (Supporting Information). The dominance of DEHP observed in the present study is consistent with other studies.3,13,31 This may indicate that DEHP, with relatively low vapor pressure, is added in a wide range of domestic appliances. The low vapor pressure means that the ratio of DEHP’s concentration in the indoor dust to its gas-phase concentration is greater than that of the more volatile phthalate esters.31,32 On the contrary, DMP and DEP contributed the least proportion to the total phthalate esters in indoor dust possibly due to its relatively high vapor pressure. 3.3. Concentration and Distribution of Phthalate Esters in Home Dust around PRD. The tested phthalate esters except DPRP were found in all home dust samples collected from the three major cities (Table 2). Total phthalate esters varied from 181 to 9240 μg/g with a median of 1360 μg/ g and a geometric mean of 1290 μg/g. The phthalate esters concentrations in home dust obtained from Guangzhou (geometric mean: 2620 μg/g) and Hong Kong (geometric mean: 1570 μg/g) were about 2−4 folds higher than that from Shenzhen (geometric mean: 650 μg/g). The contribution of each phthalate esters to the total concentration is presented in Figure S2G (Supporting Information). DEHP, DBP, and DiBP were the predominant compounds accounting for 56.0−96.5%, 1.72−29.3%, and 0.35−13.4% to the total phthalate esters, respectively. Similar to other studies,11,13,14 DEHP was the most dominant phthalate ester in home dust around PRD. The concentration of DEHP detected in the present study was about 3−5 times higher than that found in home dust from, Albany, U.S. (304 μg/g) and from Beijing, Shanghai, and Qiqihaer, P. R. China (228 μg/ g),14 but about 3 times lower than that from Denmark (3210 μg/g).11 The concentration of DBP in home dust samples observed in the present study was about 2 times higher than that of DiBP, similar to the pattern observed in USA,14 Sweden 13 and Norway.12 DBP concentration detected in the present study was 3−5 times higher than that reported in Denmark (15 μg/g) 30 and USA (13.1 μg/g), but similar to that found in Norway (100 μg/g).12 DiBP concentration obtained in home dust in the present study matched the level obtained in
a
0.40 0.200.62 0.24 0.020.34 0.43 0.073.35 1.33 0.153.67 0.31 0.0525.4 1.49 0.826.35 0.55 0.0225.4 0.05
