Endocrine Disrupting Phthalates in the Singapore Environment

2002 Country Report by: C. Basheer and H.K. Lee.

[1] Introduction

Phthalic acid esters have received attention as potential environmental contamination due to its adverse health effects and endocrine distrupting properties [1]. In 1980s the US Environmental Protection Agency and several other countries classified the commonly occurring phthalates as priority pollutants [2]. Phthalates are widely used in industrial chemicals to soften plastics in products such as medical devices (e.g. ventilator tubing, bags for intravenous solutions), toys, and food packaging materials. Human beings are continuously exposed to many products containing phthalates, for instance, dialysis patients receive large doses of phthalates if PVC tubing is used for treatment [3]. Patients needing blood transfusions are also infused with DEHP since PVC blood bags release significant amounts of DEHP into stored blood. Several studied shows exposure of phthalates have revealed toxic effects on the developing fetus, reproductive system, liver, kidneys, heart, and lungs [4-8]

The solubility of phthalates is lower in water and their K_ow values mean that significant bioconcentration effects can be expected in human and animals. However, only low-level accumulation has been reported, e.g. around 120 for DEHP in the carp and 9.4 for BBP in bluegill sunfish [9]. Phthalates are apparently metabolized by laboratory animals and humans and are excreted in urine. Some phthalates, at high dose levels, have been shown to cause reproductive effects in rats and mice. In human beings, premature breast development in girls and testicular cancer in young men is the most common malignancy [10, 11]. A comprehensive critical review of phthalate bioaccumulation literature is provided by Staples et al [12]. There is not enough information to evaluate or predict the long-term and short-term effects of DEHP to plants, birds or land animals. However long-term accumulation of phthalates does not appear to be a problem in mammals.

National and international pressure is growing for water quality improvement and better management of estuarine and coastal waters. Discharging and dumping of waste containing high level of anthropogenic organic micro pollutants pose a significant treat to many coasts worldwide. It is known that a large portion of phthalates residue reaches the marine environment through sewage discharges, ambient transportation and deposition. Phthalates are used in large quantities especially in developing industrial countries, and world wide production of phthalates was estimated to be approximately 2.7 million metric tones a year [13].

Atmospheric pollution is potentially a serious problem in many regions of the globe with high population densities and rapidly growing economies, such as Singapore. Adverse health effects associated with ambient air pollution have been studied by many researchers in recent years and there is increasing evidence that air pollution contribute to respiratory diseases, and cancer [14]. Phthalates will exist as both a gas and a particle if released to the atmosphere. Phthalates are easily volatilized, and have long residence times, e.g. DEHP is persistent in the atmosphere, and can therefore undergo long range transportation. They have been observed even in remote areas like Antarctica [15].

Deposition and pollution related to airborne chemicals, including phthalates, are not limited by national boundaries. Thus, solutions to the problems caused by contamination require committed international cooperation.

In this study, widespread contamination of phthalates was detected in the marine environment (surface, mid depth, bottom waters), rainwater and the atmosphere in Singapore. Atmospheric concentration was determined using microwave-assisted solvent extraction (MASE). The current survey has been the first step in the identification of the status and trends of phthalates in the Singapore context to acquire a better understanding of transport and deposition processes in a tropical environment such as ours.

[2] Sampling procedure

[2.1] Selection of locations

Sea surface microlayer of samples was collected at 28 locations as shown in Figure 1a. The physical properties of the seawater of first, second sampling schedule are shown in Table 1a, 1b. Additionally, 18 mid-depth, bottom water samples were collected from Northeaster, Southwestern off shores of Singapore between 3 meter and 30 meter depth as shown in Figure 2. The land reclamation, high industrial and busy shipping activities in these areas have resulted in significant stress to the particular region. Both mid depth and bottom water sample were collected using a discreet sampling methodology in conjunction with pre-cleaned (10 liters) Niskin bottles. Throughout the survey a global positioning system (GPS) was used to locate the sampling position, and the conductivity, temperature, pH of the water sampled were measured (Table 1c).

The air samples were collected using an 8-stage MOUDI (micro-orifice uniform deposited impactor) cascade impactor. Seven air samples were collected on the roof of a six-storey building (Department of Chemical & Environmental Engineering, NUS campus).

Rainwater (wet depositions) samples were collected in pre-cleaned glass beakers (more than 0.3 liter at each time) at 14 sampling sites on an event basis around Singapore. The site information is given in Table 1d, and the sample locations are depicted in Figure 1b. The pH and conductivity of the rainwater were measured. Samples were analyzed immediately for phthalates with the recommended UNU procedure (but see Section 3.3).

[2.2] Conditions during sample collection

The characteristics of the seawater samples collected are given in Tables 1a, 1b, 1c. Special care was taken during collection on the respective samples. Glass containers with aluminum-lined/Teflon-capped liner were used and the containers were filled to the top to minimize the headspace, to minimize the volatilization. To prevent possible degradation of analytes, samples were analysed on the same day as collection.

Singapore lies just north of the equator (01’, 109, N and 103’ 38’), as a result of which a uniform temperature, pressure, high humidity and abundant rainfall characterize the climate. The temperature ranges from 28ºC to 33ºC and the mean humidity is 84% throughout the year; the annual rainfall is estimated to be 2333 mm. From December to February the climate conditions are cloudy with frequent afternoon rainfall and from April to May (pre-southwest monsoon season), showers usually occur in the early evenings with thunder. For safety reasons, samples were normally collected during fine weather conditions. Salinities of the samples varied between 28 to 35 ppt; the temperature range was 28^oC to 32^oC, and pH from 7.9 to 8.6.

[3] Analytical Results

[3.1] Summary of results

Eight targeted phthalates are widely distributed in the Singapore environment due to their ubiquitous use as plasticizer compounds and the contaminations have been determined in surface, mid depth, bottom layer of the water column The ambient concentration and pore waters were also analyzed for the level of phthalate contamination. The concentration and distributions are mainly governed by the chemical properties of phthalates and environmental conditions of the coastal water. In general, Singapore marine water temperatures vary between 28ºC and 34ºC, which accelerates the degradation rate.

The overall mean concentration of phthalates varied from nd to 0.133 ± 0.089 mg/L; 0.006 ± 0.003 mg/L to 0.071 ± 0.019 mg/L during at first sampling and second sampling schedule respectively.

Figures for Eastern and Central Straits of Singapore during the first and second sampling schedule (see Table 6a, 6b): (0.002 ± 0.002 – 0.104 ± 0.078 mg/L), (003 ± 0.002 – 0.055 ± 0.028 mg/L); Southern Islands and Western Singapore, (nd-0.122 ± 0.084 mg/L), (0.005 ± 0.003 – 0.064 ± 0.025 mg/L); Northwestern Johor and Western Singapore Straits, (nd –0.055 ± 0.072 mg/L), 0.004 ± 0.001 – 0.048 ± 0.021 mg/L).

Phthalates have low solubilities in water; however they are easily associated with suspended particles and undergo sedimentation. In this study we measured distribution of phthalate concentration in offshore locations at mid depth (the mean concentration ranged between nd-0.095 ± 0.01 mg/L); bottom layer, (nd-0.035 ± 0.001 mg/L) in the Northeastern, Southwestern regions of Singapore. Overall distributions of phthalates in surface, mid depth and bottom water column concentration are shown in Figure 3. The ambient phthalate concentrations in the atmosphere varied between 0.21 and 200.98 ng/m³ and rainwater concentrations varied between nd and 0.043 mg/L. Details of the mean and ranges of concentration in the region-wise distribution of phthalate are given below.

[a] Eastern Straits of Johore between Johore and Singapore

Wide ranges of concentration of eight targeted phthalates were detected in Eastern Straits of Johore, Singapore ranging from nd to 0.361 mg/L at first sampling (June/July) and nd to 107 mg/L at second sampling (November/January). The highest concentration of phthalates; DAllylP, 0.361 mg/L at Sembawang Park; DEP, 0.320 mg/L at off Pulau Tekong; DCHP, 0.148 mg/L and DEHP, 0.148 were detected at Changi locations. The mean and ranges of concentrations for seven locations are shown in the Table below. The Eastern Straits of Johore, Singapore Straits are more heavily contaminated than the other regions; this is probably due to the confined shores, poor current movements (limited opportunities for mixing and thus dilution of pollutants), inputs from the substantial extent of shipbuilding and repairing industries, and the presence of a municipal sewage treatment plant in Changi are the possible sources of phthalates.

In addition to the contributions from shipbuilding and repairing industries at two locations (Sembawang on the Singapore side, and Pasir Gudang, a port on the Malaysian side), and from industrial release, phthalates may also be released from commercial and household discharges. Fish farms from both Malaysia and Singapore are the primary suspected sources of phthalates. However, the Maritime & Port Authority of Singapore already strictly regulates the disposal of plastic materials in the sea. Among the seven locations in this region, Sembawang Park and Changi sites were more heavily contaminated than the others; the lowest amount was recorded in Bedok Jetty, Pasir Ris at first, second sampling schedules (see Tables 3a, 3b).

Summarizing, the concentration ranges of phthalates were:

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.078	0.042	0.016	0.320
DAllylP	0.057	0.047	0.015	0.361
DBP	0.023	0.003	0.008	0.049
DOA	0.005	0.000	0.002	0.009
DCHP	0.063	0.012	0.023	0.148
DEHP	0.053	0.007	0.012	0.148
DPhP	0.026	0.016	0.000	0.074
DnoP	0.006	0.000	0.003	0.013

See the Appendix (Tables 2a, 2b) for details on the site-specific levels of phthalates

[b] Eastern and Central Singapore Straits

In this region, phthalates was detected in the range nd to 0.210 mg/L (Table 3a), nd to 0.093 (Table 3b) at first, second sampling schedule respectively. The Eastern and Central locations in Singapore Straits support activities such as petroleum refineries near the Southern Islands, recreational, tourist activities (East Coast Park, Sentosa Island and Raffles Place) and there are major shipping ports at Port Barani near the World Trade Centre (WTC) and Pasir Panjang port terminal (between Labrador Park and West Coast Park). They are expected to be the major sources of phthalates.

The highest concentration of phthalates were found at: Raffles Place (DEP, 0.210 mg/L; DAllylP, 0.148 mg/L; DEHP, 0.094 mg/L); Marina (DCHP, 0.078 mg/L); World Trade Centre (WTC) (DPhP, 0.090 mg/L). Among the seven locations, the Raffles Place site was more heavily contaminated than the others; the lowest amount was recorded off East Coast Parkway (off ECP) (see Table. 3).

Summarizing, the concentration ranges of phthalates were

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.073	0.030	0.017	0.210
DallylP	0.031	0.020	0.007	0.148
DBP	0.023	0.004	0.008	0.062
DOA	0.003	0.000	0.001	0.004
DCHP	0.045	0.001	0.018	0.078
DEHP	0.036	0.008	0.015	0.094
DPhP	0.038	0.025	0.021	0.090
DnoP	0.005	0.000	0.001	0.010

See the Appendix (Tables 3a, 3b) for details on the site-specific levels of phthalates

[c] Southern Singapore Straits

In this region, phthalates were detected in the range from nd to 0.284 mg/L (see Tables 4a), nd to 0.096 (Tables 4b) at fist and schedule second sampling schedule respectively. The Southern Singapore Straits encompasses many small islands with major petrochemical, chemical industries (Pulau Hantu, Jurong Island, etc). High concentrations of 0.284 mg/L of DEP, 0.170 mg/L of DCHP were detected in this region. Among the seven sites Jurong Island was more heavily polluted than the other sites during first sampling schedule; and Cyrene Reef was the most heavily polluted during the second sampling schedule (see Tables 4a, 4b). Multidisciplinary industries in the locations are the suspected source of phthalate pollution. The lowest concentrations of these compounds were detected at West Coast Park, St John’s Island respectively (Tables 4a, 4b). This is probably due to stricter control of disposal in the recreation places and the hydrodynamics (strong currents) in these regions.

Summarizing, the concentration ranges of phthalates were

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.069	0.038	0.008	0.284
DAllylP	0.036	0.007	0.006	0.079
DBP	0.024	0.009	0.001	0.022
DOA	0.004	0.000	0.001	0.009
DCHP	0.059	0.016	0.002	0.170
DEHP	0.047	0.007	0.005	0.064
DPhP	0.021	0.002	0.000	0.000
DnoP	0.006	0.000	0.001	0.010

See the Appendix (Tables 4a, 4b) for details on the site-specific levels of phthalates

[d] Northwestern Straits of Johore and Western Singapore Straits

In this region, phthalates was detected in the range from nd to 0.199 mg/L (see Tables 5a), nd to 0.095 mg/L (Table 5b) at first, second sampling schedule respectively. In the northwestern part of the Straits of Johore, the waters mainly support recreational and fish farms. There are no major industries on the coast. Some miscellaneous industries do exist on Singapore side (including Kranji Industrial Estate, Raffles Marina (pleasure marine craft industries)) and these are likely to be the main sources of phthalates Relatively higher concentrations of phthalates were recorded at Raffles Lighthouse: DEP, 0.199 mg/L; DBP, 0.067 mg/L; DCHP, 0.082 mg/L; DEHP, 0.074 mg/L respectively. The high amounts of phthalates at the last mentioned site clearly reflect the waste dumping carried out here, as well the presence of the incineration plant here.

There are many small industries around this region. Comparing with the overall distribution around Singapore, these six (except Raffles Lighthouse) locations showed considerably lower concentration levels than elsewhere (see Table 5). Conceivably, the strong current and more extensive exchange of water are the main reasons for this observation.

Summarizing, the concentration ranges of phthalates were

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.048	0.032	0.005	0.199
DAllylP	0.017	0.002	0.004	0.050
DBP	0.020	0.000	0.002	0.067
DOA	0.003	0.000	0.000	0.005
DCHP	0.033	0.001	0.004	0.082
DEHP	0.033	0.004	0.004	0.095
DPhP	0.024	0.003	0.000	0.052
DnoP	0.006	0.000	0.001	0.014

See the Appendix (Tables 5a, 5b) for details on the site-specific levels of phthalates

[e] Offshore samples

Mid depth, bottom layer of seawater was also assessed at the Northeastern, Southwestern offshore locations of Singapore. The sampling locations and characteristics of the water quality are shown in Table 1c. The distribution behavior of phthalates in the surface, mid depth and bottom water layer is shown in Figure 3.

Water solubility is an important parameter that controls the distribution of these chemicals in the marine environment. Contaminations of the higher molecular weight phthalates are higher at mid depth water levels (Tables 7a, 8a), and bottom water samples (Tables 6a, 6b). The concentration ranges detected at mid depth, bottom layer samples were: nd-0.121 mg/L, and nd-0.387 mg/L, respectively. Expectedly, the higher molecular compounds are less soluble due to their hydrophobic properties. Therefore, they are associated with floatable particles and undergo sedimentation more easily. Apart from this, Singapore's tropical climate facilitates the transfer of phthalates from the surface layer to the atmosphere via volatilization. This is the possible reason for the low concentration in surface layer waters.

Mid depth sampling locations of Northeastern and Southwestern Singapore

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.020	0.005	0.014	0.121
DAllylP	0.007	0.005	0.000	0.027
DBP	0.006	0.005	0.006	0.030
DOA	0.002	0.000	0.000	0.007
DCHP	0.095	0.010	0.018	0.308
DEHP	0.016	0.003	0.009	0.085
DPhP	0.000	0.000	0.000	0.000
DnoP	0.003	0.001	0.001	0.012

See the Appendix (Tables 7a-8a) for details on the site-specific levels of phthalates

The Northeastern regions are more heavily polluted than the Southwestern region (see Tables 7a,b, and 8a, 8b) most probably due to poor circulation of tidal water, the presence of a municipal effluent treatment plant, shipbuilding and shipping port activities, and many small scale industries on shore in this region.

Bottom layer sampling locations of Northeastern and Southwestern Singapore

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.011	0.001	0.000	0.048
DAllylP	0.035	0.001	0.005	0.121
DBP	0.007	0.004	0.007	0.030
DOA	0.002	0.000	0.000	0.005
DCHP	0.093	0.055	0.048	0.387
DEHP	0.018	0.006	0.016	0.074
DPhP	0.000	0.000	0.000	0.000
DnoP	0.005	0.002	0.001	0.018

See the Appendix (Tables 7b, 8b) for details on the site-specific levels of phthalates

[f] Air samples

Phthalates are used as plasticizers in a variety of plastics and are emitted in the atmosphere after burning of plastics in fires and in municipal incinerators. The Indonesian forest fires in the past few years have received much attention of the regional and international communities because they contributed a broad range of organic contaminants to the environment [16]. Due to these forest fires, smoke haze episodes have occurred on several prolonged occasions in Singapore and Malaysia, although during the time the present work was carried out, there were no extensive or major haze episodes of the type seen some years ago.

The overall atmospheric phthalate concentrations varied from 0.21-to 200.98 ng/m³. The highest concentrations of 200.98 ng/m³; 197.56 ng/m³ and 100.41 ng/m³ were observed for DBP, DOA and DnoP, respectively. Comparatively lower concentrations of DEP were detected (see Table below).

Summarizing, the concentration ranges of phthalates in air samples were

Concentrations in ng m^3
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	1.34	1.25	0.21	4.36
DAllylP	27.36	14.20	11.72	52.94
DBP	56.68	68.91	1.41	200.98
DOA	38.02	65.60	0.00	197.56
DCHP	5.77	2.22	3.17	10.44
DEHP	2.06	1.22	0.70	4.32
DPhP	6.43	3.76	2.35	12.04
DnoP	36.52	34.95	3.86	100.41

See the Appendix (Table 9) for details on the site-specific levels of phthalates

The more volatile compounds remain longer in gas phase, but distribution is very sensitive to temperature, and therefore the ratio of the concentration in the gas phase and the particle fraction shows a large decrease in winter [17]. This study was the first in Singapore to measure the levels of phthalates in air.

[g] Rainwater

Phthalates either as gas or attached to solid particles, break down relatively quickly (1 or 2 days). The solid particles are thought to be removed from the atmosphere in two to three weeks by various mechanisms, including precipitation, washout by rain and reaction with other chemicals [18, 19]. The small particles have long atmospheric residence time and are eventually deposited by rain or fallout process, consequently facilitating the global distribution of the compounds. DEHP is slightly persistent in the environment.

Table 10 shows the analytical results of the analysis of phthalates in rainwater. The highest amounts of phthalates recorded were 0.046 mg/L (DAllylP) at Redhill-1; 0.022 mg/L (DPhP) at Kent Ridge 3 (on the University campus). The overall concentration varied between nd to 0.046 mg/L. Mean values are given below.

Concentration ranges of phthalates in rainwater were:

Concentrations in mg/L
Analytes	Mean	Standard deviation	Minimum	Maximum
DEP	0.003	0.002	0.000	0.006
DAllylP	0.018	0.016	0.001	0.046
DBP	0.003	0.001	0.002	0.006
DOA	0.001	0.000	0.000	0.002
DCHP	0.012	0.004	0.005	0.019
DEHP	0.008	0.004	0.002	0.018
DPhP	0.003	0.007	0.000	0.022
DnoP	0.001	0.001	0.001	0.002

See the Appendix (Table 10) for details on the site-specific levels of phthalates

Phthalates released to the atmosphere may undergo abiotic degradation or be transported back to the surface by dry or wet deposition. Higher molecular compounds present in the gas phase show high Henry constants and are thus scavenged with high efficiency by fog, cloud or rain droplets [20]. This scavenging ratio is also high for particle-bound compounds [21]. Thus, precipitation is an important route by which airborne phthalates are deposited onto the earth's surface.

[3.2] Summary of Quality Assurance and Control Measurements

All data were subjected to strict quality control procedures, including the analysis of procedural blank and spiked samples with each set of sample analysed. Calibration curves were constructed with a linearity of >0.99. Extraction was performed with 500 mg/L of eight-phthalate mixture spiked into laboratory-prepared seawater (Instant Ocean^Ò sea salt dissolved and made up to a salinity of 32 ppt). Most of the compounds exhibited recoveries of greater than 90%. The recovery results are summarized in Table 11. In addition, carrying out triplicate sampling assessed the errors involved in sampling. Reappearance of phthalates was performed and the data are summarized in Table 12.

[3.3] Problems Encountered

Phthalates pose great analytical challenges since they are ubiquitous and are thus present in many reagents and solvents. Contamination is a major problem in the analysis of phthalates, especially from solvent, GC injection septa and unclean, plastic-containing glassware. By far the most serious contamination problem was with the materials used for GC injection ports (septa). To avoid this contamination 3 to 4 solvent blank runs were performed for every batch of samples analysed. All extraction was performed in acetone- rinsed (several times) glassware.

Although outside the scope of the UNU programme, we took the opportunity to explore various alternative extraction approaches that were more rapid and less time-consuming, and were also compatible to some of the principles of Green Chemistry. These studies are in progress and will be reported in detail elsewhere. We analyzed ambient air samples using microwave-assisted solvent extraction procedure. In this method sample cleanup was a critical step. Initially, we used Florisil and C18 solid-phase extraction (SPE) cartridges for cleanup. DEHP and DAllylP were the interfering analytes. Oasis-HLB SPE cartridges (Waters) were finally used as they gave comparatively better (much less interferences from DEHP and DAllylP results than conventional C18 and Florisil SPE products. Oasis HLB had previously been used phthalate extraction [22]. Special care was taken and at each stage, a blank extraction was performed to check for interferences. Generally, we encountered no major problems in the use of the stipulated procedures in this monitoring programme, except that toluene was used as extraction solvent instead of hexane due to high blank (DEHP peak)

[4] Conclusions

Phthalates in the Singapore environment were monitored in this work. Phthalates are present in the environment but their levels are low due to their extremely low solubility in water and their rapid aerobic degradation. At these levels (up to the limit of their water solubility) they do not have any toxic effects on a wide range of aquatic organisms. However, it is important to point out that as far as the endocrine disrupting properties of chemicals, including phthalates, are concerned, there may not be a "safe" threshold value. Thus it is extremely important that the presence of these chemicals be carefully monitored to assess their potential impact.

The concentrations of phthalates found in this study are lower than those of DEP (0.62 µg/L); DEHP (2.12 µg/L) from Tarragona industrial port, Ebro river of Spain [23]. Work in Italy-Quercianella reported similar levels to those we determined in Singapore: DBP, 0.233 µg/L; DEHP, 0.154 µg/L; and DnoP, 0.335 µg/L [24]. The concentrations detected in the present work are lower than the EPA water quality guidelines values [25], i.e.: maximum 6 µg/L (DEHP) and 0.4 µg/L of (DOA).

The ambient atmospheric concentrations of DEHP detected from our environment are comparable with those found at the Gulf of Mexico, ranging from 0.4 ng/m³ to 2.9 ng/m³ over the North Atlantic [26, 27] and the North Pacific where the average concentrations in air were 1.4 ng/m³ (range 0.3–2.7 ng/m³) [28]. Our values were higher than those determined at the Great Lakes (average of 2 ng/m³ (range 0.5–5 ng m³)) [29].

The environment is a complex system, and it. is difficult to assess the impact of phthalates exclusively to organisms and humans. However, a number of independent studies on a variety of sediment-dwelling organisms have shown that phthalates, at concentrations many times greater than those found in the environment, have no adverse effects [30]. Further work would be needed to obtain more information on these compounds in this regard. While more conclusive data are forthcoming, we must in the meantime undertake the monitoring of these compounds in environments to which human beings and animals are exposed to.

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