Environ. Sci. Technol. 1990, 24, 554-559
Phthalate Esters in the Swedish Atmosphere Anders Thurin*#tand Per Larssonr
Special Analytical Laboratory, Swedish Environmental Protection Agency, S-17 1 85 Solna, Sweden, and Limnology, Institute of Ecology, University of Lund, Box 65, S-221 00 Lund, Sweden
w Levels of dibutyl phthalate (DBP) and bis(Bethylhexy1) phthalate (DEHP) were measured in airborne fallout and in air at 14 localities in Sweden to determine whether their distribution is governed by local or long-range transport processes. The phthalate esters in the airborne fallout, derived from dry and wet deposition, were trapped on silicone-impregnatednets, whereas phthalate esters in the air were collected on polyurethane foam filters. The ubiquity of DBP and DEHP in the airborne fallout and in the air indicates that they are widely distributed in the Swedish atmosphere. The fallout rates and atmospheric concentrations of DBP and DEHP were of similar magnitude, despite the fact that the consumption of DEHP is 10 times that of DBP in Sweden. A detailed study of the emissions from a phthalate ester consuming factory revealed a local fallout gradient. The total deposition of DBP and DEHP to the ground in Sweden was estimated to be 220 tonpyear-l and is of a similar order of magnitude as the emissions. The fallout rates and the levels of phthalate esters in the air were temperature-dependent. In winter when the temperature was low, the atmospheric fallout of phthalate esters was high while their levels in the air were low. High atmospheric concentrations were found in the summer. Introduction Organic compounds in the atmosphere are present in the gaseous and the aerosol phases or are adsorbed to particles. The distribution and atmospheric lifetimes of the pollutants depend largely on their vapor pressure, the particle concentration, and composition (1, 2). In industrial areas the density of particles is high, leading to an increase of particle-associated pollutants (3). One of the dominant deposition mechanisms of persistent organic compounds to the ground is washout by rain (4). Removal of airborne organic pollutants by precipitation occurs due to the scavenging of particles by, and partitioning of organic vapor into rain and snow. The extent of this process depends on the distribution of the organic matter between the gaseous and aerosol phases, particle-size distribution, and Henry's law constant ( 4 ) . For compounds of low solubility, the Henry's law constant H is equal to the ratio of a compounds vapor pressure to its solubility and is strongly influenced by temperature (5). In addition, pollutants may be removed from the atmosphere by deposition of particles to which the compounds are adsorbed (dry deposition). The deposition of a particle-associated pollutant is roughly determined by the size and electric charge of the particle, by its reaction tendency, and by the concentration of the pollutant (6). For many chlorinated hydrocarbon pollutants atmospheric transport is the major route of entry to the terrestrial and aquatic ecosystems. Eisenreich et al. (2) estimated the atmospheric input of PCBs into the Great Lakes to be 60-90'70 of the total input. Toxaphene has been transported from southern U.S. cotton-growing areas to Bermuda (7). The long-range transport of organic Swedish Environmental Protection Agency. *University of Lund. 554
Environ. Sci. Technol., Vol. 24,No. 4, 1990
micropollutants can be illustrated by the various chlorinated hydrocarbons detected in Arctic (8) and Antarctic air (9). PCBs, DDT, BHC isomerides, and chlorinated camphenes are among the pollutants that have also been detected in air and precipitation in Sweden (10-14). The distribution of phthalic acid esters in Norway shows a decreasing gradient from urban locations to areas not influenced by human activities (15). During the last decade, phthalate esters have been one of the most widely produced chemicals in the world (2 million tons per year). Among the phthalate esters, bis(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the most commonly used compounds. They are mainly used as plasticizers in polyvinyl chloride (60% w/w) but are also found in cosmetics, lubricants, floor carpets, tapestry, and other products. Phthalate esters will vaporize from the material at a rate depending on their volatility (16). Phthalate esters are lipophilic and have log 1-octanol/water partition coefficients between 3 and 9 (17) and low vapor pressures (18). They are readily accumulated both by animals (19, 20) and by plants (21). To determine whether the distribution of phthalate esters in Sweden is governed by local or long-range transport processes, phthalate esters in atmospheric fallout and in the air were studied at 14 localities in Sweden. Material and Methods Sampling Techniques and Extraction. Phthalate esters were sampled with a nylon net (mesh size, 200 pm) impregnated with silicone oil (SE-30). The method was identical with that used by Sodergren ( 1 0 , I I ) . Particles originating from airborne fallout as well as lipophilic pollutants and particles present in rainwater will be trapped by the oil, as the water percolates through the net. The screens thus sample substances originating from both dry and wet deposition. Sampling lasted for approximately 3 months. The phthalate esters were extracted from the fallout nets with hexane in Soxhlet extractors (10). The extracts were cleaned-up with fuming concentrated sulfuric acid, which separated the nonpolar material (e.g., PCBs, DDT, toxaphene) into the hexane phase, whereas the sulfuric acid contained the phthalate esters and the silicone oil (22). After the hexane was removed, hydrated sulfuric acid was added to deionize the phthalate esters, and the phthalate esters were retransferred to the solvent by shaking with n-hexane. However, the hexane also contained some silicone oil, which made gas chromatographic detection of the phthalate esters difficult. To separate the phthalate esters from the oil, 2 mL of concentrated acetic acid was added to the 1.0-mL hexane fraction, and the mixture was shaken for 3 min. The upper layer containing the silicone oil was decanted. The hexane and the phthalate esters were separated from the acid by adding 3.0 mL of distilled water. The hexane was transferred to a test tube, dried over sodium sulfate, evaporated under nitrogen to -500 ~ L Land , analyzed for phthalate esters. The levels of phthalate esters in air were determined by passing 300-400 m3 of air through a particle filter
0013-936X/90/0924-0554$02.50/0
0 1990 American Chemical Society
Table I. Levels and Ranges of Phthalate Esters in the Atmosphere and in Precipitation from the United States and Sweden
sampling station
compd
Enewetak Atoll, North Pacific Ocean
DBP DEHP DBP DEHP DBP DEHP DBP DEHP
Portland, OR Great Lakes Sweden
'Median.
n
air concn, mean
17 17
1 5
0.87 1.4 0.37 0.39
16 16
I 0.06-0.94 0.50-5.0 0.50-5.0 0.23-49.9 0.28-77.0
2.0 51 53
range 0.40-1.80 0.32-2.68
precip concn, ng.L-' n mean range
2.0 1.7' 2.0"
6 56 56
31 55 46 2.6 6 6 36b
48b
ref
2.6-12.5 5.3-213 34-61 1.6-3.8 4-10
32 4 2
4-10
this study
3.0-496 8.3-429
Median; concentrations derive from both wet and dry deposition.
(Whatman GF/F) and one or two polyurethane filters connected in series (23). The flow rate was 4.5 m3 of air day-'. Sampling lasted for periods of 3 months. The flow rate of the pumps was checked at the beginning and end of the sampling periods. Compounds adsorbed to the PPF filters were extracted with acetone/hexane in an ultrasonic bath (23). The extract was treated with sulfuric acid and the sulfuric acid phase (containing the phthalate esters) was treated according to the method of Thur6n and Sodergren (22). Glasswares and solvents were treated according to Thur6n ( 2 4 ) to minimize contamination by phthalate esters. Unexposed fallout nets, polyurethane filters, and silicone oil were checked for the presence of the substances, and the field values were corrected. Analysis Methods. A Varian Model 3700 GC with a flame ionization detector (FID), equipped with a 25 m X 0.25 mm (i.d.) fused-silica column (SE-54) was used for the separation and quantification of DBP and DEHP. The samples were injected on-column (25). The chromatographic conditions were: injector temperature 50 "C, detector temperature 260 "C. The oven was programmed from 50 to 150 "C at a rate of 40 "C m i d , held isothermal at 150 "C for 10 min, and from 150 to 250 "C at a rate of 20 "C min-'. Hydrogen was used as the carrier gas (1.5 mL.min-') and nitrogen as makeup gas (50 mlsmin-'). The minimum detectable quantity (MDQ) on the FID (signal/noise ratio 2:l) for DEHP and DBP was 0.05 ng. A Ribermag R10-10c quadropole mass spectrometer (Ruil Malmaison, France) was used for the identification of DBP and DEHP. The gas chromatograph was a Carlo Erba instrument Model 4160, equipped with an all-glass splitless injector and a 25 m X 0.25 mm (i.d.) fused-silica column (SE-54). Helium at an inlet pressure of 0.8 kgcm-2 served as carrier gas. The temperature of the injector was 200 "C, the interface between the gas chromatograph and the ion source 250 "C, and the ion source 175 "C. The oven was programmed from 60 to 240 "C at a rate of 6 "C min-'. The split valve was opened 30 s after injection. The methane reagent gas (0.7 Torr, purity >99.95%) was ionized with electrons at an energy of 70 eV. The extraction efficiency of DBP and DEHP on the PPF filters was tested. Known amounts of the compounds were mixed in 1mL of ethanol. The mixture was injected into the PPF filters and the solvent was evaporated by passing approximately 10 m3 of clean air through the filters. Air was cleaned by a PPF filter connected to the inlet. The filters were treated as above and the amounts adsorbed on the filters were calculated. Sampling Stations. Phthalate esters in the airborne fallout and in the air were studied at 14 stations from the south of Sweden and 1600 km to the north (Figure 1). The stations were chosen so that they would cover a wide range of climatic conditions (from a warm humid climate in the south to an arctic cold high-altitude climate in the north).
-
0
1 , 55'27". 13'22'E
2. 3. 4. 5. 6
200 400 600km
inland
55'55", 14"lO'E 56'112". 15'40'E 56'50". 16'37'E 57041'N. 14'43'E 57047". 13'24'E 7. 58°16". 11'26E 8 58038". 12'26'E 9. 5S039", 17O04'E 10. 60'39". 1PlO'E 11. 6 C i i ' ~ 2. 0 ~ 5 2 ' ~ 12. 63'52", 15'35'E 13. 68'19", 18'52'E 14. 68'25". 18'10E
Figure 1. Location of the 14 stations in Sweden where phthalate esters were determined in airborne fallout and in the air. Sampling was performed during 1 year (1984-1985) in 3-month periods.
The stations are used by the Swedish Institute of Meteorology and Hydrology (SMHI); therefore, meteorological data were available. Sampling was carried out for four consecutive 3-month periods over 1year [periods 1 (October 1984-January 1985), 2 (January-April), 3 (AprilJuly), and 4 (July-October)]. In addition to the national study, airborne, local fallout around a phthalate-consuming factory, located in southern Sweden (Figure l),was followed for 3 months (OctoberDecember 1985). Ten fallout samples were taken at increasing distances (0-15 km) downwind from the smokestack in a northeasterly direction.
Results DEHP and DBP were detected in both airborne fallout and air at every sampling station throughout the study period (Figure 2a,b). The average fallout rates of phthalate esters at the stations were for DBP, 16.8 ,ugm-2.month-1 (quartile deviation, Q = 10.4; Min 1.98, Max 335.5), and for DEHP, 23.8 pgm-2.month-' (Q = 13.5; Min 5.96, Max 195.5). The median concentration of phthalate ester fallout (wet and dry) related to the precipitation volume was estimated to be 36 ng of DBP L-l (Q = 25) and 48 ng of DEHP L-l (Q = 35). In the air the median levels were 1.68 ng of DBP m-3 (Q = 1.5) and 1.95 ng of DEHP m-3 (Q= 1.9) (Table
I).
The fallout rate of DEHP decreased with increasing distance from the smokestack of the phthalate-consuming factory and ranged from 30 to 283 pg of DEHP m-2month-' (Figure 3). High levels of DBP were correlated with high levels of DEHP both in fallout (Rs = 0.69, p < 0.001, Spearman rank correlation) and in air (R, = 0.57, p < 0.001, Spearman rank correlation). Environ. Sci. Technol., Vol. 24, No. 4, 1990 555
200 L
t
100
y.
E
9 0
1 2 3 4 5 6 7 8 9 1011 121314 Station
20
'7
E 10
2 0 1 2 3 4 5 6 7 8 9 1011 121314
Station Flgure 2. (a) Average monthly rates of DBP and DEHP in airborne fallout in Sweden 1984-1985. Period 1. October-December 1984: period 2, January-March 1985: period 3, AprilJune 1985; period 4, July-September 1985. (b) Levels of DBP and DEHP in the atmosphere in Sweden 1984-1985 (nd. not detected).
The fallout of DEHP was negatively correlated with the mean temperatures a t the sampling stations (R, = 0.41, p < 0.005,Spearman rank correlation). The levels of DBP and DEHP in the air were positively correlated to the mean temperatures at the sampling stations [R, = 0.60, p < 0.001 for DBP (Figure 4) and R. = 0.49, p < 0.001 for 556
Environ. Sci. Technol.. VoI.
24, No. 4, 1990
DEHP, Spearman rank correlation]. The fallout rate and concentrations of phthalate esters in air differed significantly between the sampling periods (p < 0.001, Friedman analysis of variance by ranks). The lowest fallout of DBP and DEHP was recorded in period 3 (April-July; Figure 2a), while the lowest concentration
Table 11. Comparison of Fallout Coefficients for DBP and DEHP above and below 0 Oca
DBP
DEHP
n
-15 to 0 O C median fJ
n
20 20
71346 60355
37 37
45243 44645
0 to +15 'C median Q
9667 9619
9398 10539
OQ, quartile deviation. Calculation of fallout coefficients: The concentration of phthalate esters in the airborne fallout (both wet and dry) was divided by the concentration of the compound in the
0
0.2 0.4
1.0
0.6 0.8
2.0 4 . 0 8.0 15.0
Distance (km)
Airborne fallout rates of DEHP. downwind from a phlha!ate-consuming factory in the south of Sweden.
Flgure 3.
.
151
'C
Average--
of DBP in the air f" the different localities as a function of the average ambient temperature. Flgure 4. Levels
. "., . ..' :
0 -15
-10
-5
0 Arerye--
5
--.a1 10
. 15
OC
Flgure 5. Calculated fallout coeffldentsfor DBP as a function of the
average temperature.
of DBP and DEHP in the air was observed during period 1 (Octoher-January; Figure 2b). The fallout coefficients for DBP and DEHP increased with decreasing temperature [R.= 0.72, p < 0.001 for DBP (Figure 5) and R, = 0.68, p < 0.001 for DEHP, Spearman rank correlation]. A t temperatures below zero the mean fallout coefficients for DBP and DEHP were 71 346 and 60355, respectively. At temperatures above zero the mean fallout coefficients were 9667 for DBP and 9619 for DEHP (Table 11). The total fallout of phthalate esters per year in Sweden would amount to -90 metric tons of DBP and 130 metric tons of DEHP, assuming that the stations are representative. The identification of DBP and DEHP was confirmed by GC-MS. The recoveries of phthalate esters added to the PPF filters were for DBP 79% (SD = 12%. n = 6) and for DEHP 117% (SD = 13, n = 6). The background levels of DBP and DEHP from unexposed fallout nets were lo00 ng (SD = 600, n = 6) and 1100 ng (SD = 350, n = 6). respectively. Seventy-five percent of the contamination originated from the silicone oil and -25% from solvents and glassware. Blank values for unexposed PPF filters were
