Organochlorine pesticides in the ambient air of Chiapas, Mexico

Environmental Pollution 140 (2006) 483e491 www.elsevier.com/locate/envpol Organochlorine pesticides in the ambient air of Chiapas, Mexico Henry Alegria a,*, Terry F. Bidleman b, Miguel Salvador Figueroa c b a Chemistry Department, California Lutheran University, 60 West Olsen Road, Thousand Oaks, CA 91360, USA Centre for Atmospheric Research Experiments, Meteorological Service of Canada, 6248 Eighth Line, Egbert, ON L0L 1N0, Canada c Area de Biotecnologia, Facultad de Ciencias Quimicas, University Autonoma de Chiapas, Carretera a Puerto, Madero Km. 2, Tapachula, Chiapas, Mexico Received 26 January 2005; accepted 5 August 2005 Elevated levels of several organochlorine pesticides were found in the ambient air of southern Mexico. Abstract Organochlorine (OC) pesticides were measured in the ambient air of Chiapas, Mexico during 2000e2001. Concentrations of some OC pesticides (DDTs, chlordanes, toxaphene) were elevated compared with levels in the Great Lakes region, while those of other pesticides were not (hexachlorocyclohexanes, dieldrin). While this suggests southern Mexico as a source region for the former group of chemicals, comparably high levels have also been reported in parts of the southern United States, where their suspected sources are soil emissions (DDTs, toxaphene) and termiticide usage (chlordane). Ratios of p,p#-DDT/p,p#-DDE and trans-chlordane/cis-chlordane/trans-nonachlor (TC/CC/TN) in Chiapas suggest a mixture of fresh and weathered sources, while congener profiles of toxaphene suggest emission of old residues from soils. This is supported by air parcel back trajectory analysis, which indicated that air masses over Chiapas at the time of sampling had previously passed over areas of continuing or recent use of some OC pesticides as well as areas of past use. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Organochlorine pesticides; Persistent organic pollutants; Mexico; Air 1. Introduction Despite being banned for years or even decades in Canada, the U.S. and most European countries, many organochlorine (OC) pesticides such as DDT compounds (DDTs), hexachlorocyclohexanes (HCHs), chlordanes, dieldrin and toxaphene continue being detected in the ambient air on regional and continental scales (Jaward et al., 2004; Shen et al., 2004, 2005; Van Drooge et al., 2002). In North America, for example, OC pesticides commonly occur in air and water in the Laurentian Great Lakes on the CanadaeU.S. border (Buehler et al., 2001; Cortes and Hites, 2000; Hoh and Hites, 2004; James et al., 2001; Jantunen and Bidleman, 2003; Marvin et al., 2004; Shen et al., 2004, 2005), in snow and glacial * Corresponding author. Tel.: C1 805 493 3767; fax: C1 805 493 3392. E-mail address: [email protected] (H. Alegria). 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.08.007 ice in western Canada (Blais et al., 1998; Donald et al., 1999) and in the Canadian Arctic air (Halsall, et al., 1998; Hung et al., 2002, 2004). An unresolved question is whether OC pesticides detected in these environments are due to recycling from local soils or originate from areas of current or very recent use. Many OC pesticides are known to persist in the environment long after their application and have also been shown to be susceptible to long-range atmospheric transport. Consequently, both old and new sources may account for the OC pesticides detected in North America. In order to distinguish between these contributions, we have been studying the Central AmericaeMexico region to determine its significance as a source region to North America (Alegria et al., 2000). This region has been characterised by high OC pesticide usage in both agriculture and for disease vector control (Castillo et al., 1997; Leonard, 1990; Mora, 1997). Many OC pesticides continue to be used or were used until just recently. Mexico 484 H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 has historically been a significant consumer of DDT. DDT was used in agriculture and for disease vector control in many parts of the country. Chiapas was the last state in Mexico legally allowed to use DDT for agriculture and was one of the largest users for disease vector control. High levels of DDT and its metabolites have been found in human milk and adipose tissue from the state of Veracruz (Waliszewski et al., 2001). Consumption of DDT in Mexico for both agriculture and public health applications was 8e9 kilotonnes (kt) yearÿ1 in 1971e 1972, declined to 3e4 kt yearÿ1 from 1974 to 1981 and reached a minimum of about 0.5e1 kt yearÿ1 from 1982 to 1984. From 1985 to 1991, DDT use increased to 1.5e 2.5 kt yearÿ1 (Lopez-Carrillo et al., 1996). The use of DDT for public health declined from 1.4 kt in 1993 to less than 0.3 kt in 1999 (NACEC, 2004). Under the North American Regional Action Plan (NARAP), Mexico agreed to phase out DDT by 2002, but reported complete phase-out in 2000 (Anonymous, 2001). In 1997, Mexico restricted the use of chlordanes to urban applications as a termiticide. Under the NARAP for chlordanes, Mexico ended their use in 2003 (Moody, 2003). Toxaphene was legally used in the MexicoeCentral America region until the 1990s (Carvalho et al., 2003; Castillo et al., 1997). Cumulative usage in Mexico (Li and Macdonald, 2005) and Nicaragua (Rodezno, 1997) has been estimated at 71 kt and 79 kt, respectively. This represents approximately 15% of total usage in the U.S., estimated at 490 kt between 1947 and 1986 (Li, 2001). Consequently, the region may represent an important source of atmospheric contamination for North America. In 1995e1996, concentrations of OC pesticides were measured in air at two locations in Belize, Central America, an inland one in Belmopan and a coastal one in Belize City (Alegria et al., 2000). Results indicated that concentrations of some OC pesticides at the inland location were significantly elevated compared to levels measured in the Great Lakes region (e.g. DDTs, dieldrin and aldrin), supporting the hypothesis that Central America is a source region for North America. In addition, the elevated levels of some presumably banned OC pesticides suggests that they are still being used in the Central America region. To investigate further the source region hypothesis, this study was carried out in southern Mexico, historically the largest user of OC pesticides in the region, to measure their concentrations in ambient air. 2. Experimental 2.1. Sampling collection and preparation Air samples were collected from the roof of a private residence (10 m) located about 5 km from Tapachula, Chiapas, a city of approximately 250,000 inhabitants located in an area of large-scale agricultural production in the state of Chiapas (Fig. 1). This residence is fairly new (!10 years old) and was never treated with chlordanes (termiticides), according to the owner. Sampling was carried out for 24 h every 14 days from August 2000 to June 2001. Samples were collected with a high-volume sampler in which w500 m3 air was drawn through a 10-cm diameter glass fibre filter followed by a polyurethane foam (PUF) trap consisting of two 8.0-cm diameter ! 7.5-cm thick plugs. Filters and PUFs were stored in a freezer until analysed. Ambient temperatures during the sampling period ranged from approximately 299 to 308 K (26e35  C). Filters and PUF plugs were soxhlet-extracted together overnight (16 h) with petroleum ether. Prior to extraction, PUF plugs were fortified with a mixture containing 20 ng each of a-HCH-d6, 13C10-heptachlor exo-epoxide (HEPX), 13C10trans-nonachlor (TN) and 13C12-dieldrin, and 100 ng of p,p#DDT-d8 which served as surrogates for assessing method recoveries for each sample. Extracts were concentrated by rotary evaporation, blown down with a gentle stream of nitrogen and exchanged into iso-octane. Extracts were cleaned up and Fig. 1. Sampling location (Tapachula, Chiapas, Mexico). H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 fractionated on a column of neutral Al2O3 (1 g, 6% deactivation with H2O) overlain with 1 cm anhydrous Na2SO4. The column was pre-eluted with 10 mL dichloromethane followed by 10 mL petroleum ether. Extracts were applied in w1 mL isooctane and the column was eluted with 15 mL 5% dichloromethane/petroleum ether. The eluate was concentrated by nitrogen blow-down and solvent-exchanged into isooctane. Volumes were adjusted to w1 mL and 13C10-PCB105 was added as an internal standard just prior to analysis. 2.2. Analysis OC pesticides (except toxaphene) were quantified by gas chromatographyeelectron capture negative ion mass spectrometry (GC-ECNI-MS) on an Agilent 6890GC-5973 MS detector with a DB-5 capillary column (J&W, 60 m ! 0.25 mm i.d., 0.25 mm film thickness). Total toxaphene was quantified on a HewlettePackard 5890 GC-5989B MS Engine, using the same type of column, as the sum of the 7-Cl, 8-Cl, and 9-Cl homologues. The detectors in both instruments were operated in the selective ion-monitoring mode to enhance sensitivity. Specific details for the monitored ions and operating conditions can be found elsewhere (Alegria et al., 2000; Jantunen et al., 2000). 2.3. Quality control Recovery experiments were carried out two ways. First, surrogates were added to PUF plugs prior to extraction. Average recoveries of these surrogates were: a-HCH-d6 56 G 5%, p,p#-DDTd8 102 G 8%, 13C10-HEPX 72 G 12%, 13C10-TN 90 G 5%, 13C12-dieldrin 76 G 4%. Second, six clean PUF plugs were spiked with a mixture containing the target pesticides and treated as samples. Average recoveries for the second method agreed with the first method, being greater than 70% for all pesticides except for a-HCH (60 G 5%). Calibration standards were also routinely run with each batch of samples. Front and back PUF plugs were analysed separately to assess breakthrough of gas-phase OC pesticides. Breakthrough was significant only for a-HCH, g-HCH and heptachlor. aHCH on the back PUF averaged 78% of the front PUF value (42e100%); g-HCH averaged 44% (29e76%); and heptachlor averaged 62% (38e77%). Results for these three pesticides are reported as the sum of both PUF traps. Three field and three laboratory blanks were run. No peaks matching the target compounds were found on blank PUFs, so limits of detection (LOD) for each pesticide were calculated by finding the lowest detectable concentration of the pesticide injected on the analytical instrument (instrumental detection limit, IDL) and calculating the limit of detection as: LOD Z (average IDL) C (3 ! standard deviation). LODs ranged from 0.06 pg mLÿ1 (trans-chlordane) to 7 pg mLÿ1 ( p,p#DDT). These LODs correspond to 0.1e14 pg mÿ3 for a nominal air volume of 500 m3 and a final extract volume of 1000 ml. The quantitation limit for total toxaphene (24 pg mÿ3) was based on the lowest concentration of technical toxaphene standard employed (12 pg mLÿ1). 485 3. Results and discussion 3.1. Air concentrations of pesticides in Chiapas Table 1 gives the concentrations of target OC pesticides in air in Chiapas, Mexico. Because of the wide range of concentrations, both arithmetic (AM) and geometric (GM) means were calculated. GMs were lower than AMs. 3.1.1. DDTs Concentrations of total DDTs, sum of p,p#-DDT C o,p#DDT C p,p#-DDD C o,p#-DDD C p,p#-DDE C o,p#-DDE (SDDT) ranged from 351 to 1548 pg mÿ3, although most values were in the upper range (11 of 18 samples had concentrations above 900 pg mÿ3 and only 2 samples had concentrations below 600 pg mÿ3). AM and GM concentrations were 997 and 927 pg mÿ3, respectively. These high concentrations are typical of other tropical regions with ongoing use of DDTs (Larsson et al., 1995; Ngabe and Bidleman, 1992). The ratio of p,p#-DDT/p,p#-DDE is generally used as an indicator of aging of DDTs. This ratio calculated from mean concentrations was 1.06 based on AM and 1.02 based on GM concentrations; the ratio was O1 for half of the samples (Table 1). Shen et al. (2005) deployed passive air samplers (PAS) across North America during 2000e2001 (see below) and reported ratios of p,p#-DDT/p,p#-DDE Z 0.94 in Tapachula and 1.3 in Chetumal, Mexico, 1.2 in Belmopan, Belize, and 5.8 in Costa Rica. The Mexico and Belize ratios agree well with our results in Tapachula, while the Costa Rica composition indicates a greater input of fresh DDT. Ratios of p,p#DDT/p,p#-DDE in the ambient air of the U.S. and Canada are generally !1, but occasionally exceed 1 (Aulagnier and Poissant, 2005; Cortes and Hites, 2000; Harner et al., 2004; Park et al., 2001; Shen et al., 2005). The p,p#-DDT/p,p#-DDE w1 in Tapachula is consistent with a mixture of contributions from recent usage and old DDT residues. 3.1.2. HCHs Average concentrations of HCHs were: a-HCH AM Z 27 pg mÿ3, GM Z 22 pg mÿ3 and g-HCH AM Z 76 pg mÿ3, GM Z 72 pg mÿ3. The ratios of a-HCH/g-HCH based on AM and GM concentrations were 0.38 and 0.31. This ratio in technical HCH ranges from about 4e8 (Breivik et al., 1999). The much lower a-HCH/g-HCH found here indicates the continued use of lindane (pure g-HCH) in the region. The ratio of ~0.3 found here is consistent with results from a 2000e2001 passive air sampling campaign in the region in which a-HCH/g-HCH Z 0.16 in Tapachula and 0.46 in Chetumal, Mexico, 0.18 in Costa Rica and 0.27 in Belmopan, Belize (Shen et al., 2004). The high proportion of a-HCH on the second PUF trap indicates the possibility that there may have been some breakthrough through both PUF traps and consequently incomplete collection and underestimated air concentrations, which would alter the true ratio of a-HCH/g-HCH. However, the agreement of our ratio of w0.3 with ratios in the region 486 Table 1 Concentrations of OC pesticides in ambient air in Chiapas, 2000e2001 (pg mÿ3) 24 Aug 2000 9 Sep 2000 23 Sep 2000 21 Oct 2000 5 Nov 2000 18 Nov 2000 2 Dec 2000 16 Dec 2000 14 Jan 2001 29 Jan 2001 13 Feb 2001 3 Mar 2001 31 Mar 2001 14 Apr 2001 28 Apr 2001 20 Jun 2001 8 Jul 2001 AM SD GM 44 100 0.44 22 49 0.45 54 59 0.92 27 72 0.38 30 75 0.40 33 94 0.35 62 62 1.00 44 92 0.48 17 136 0.13 11 80 0.14 11 68 0.16 35 82 0.43 29 83 0.35 13 47 0.28 10 44 0.23 7 111 0.06 10 35 0.27 32 75 0.43 27 76 0.38 16 25 0.24 22 72 0.31 147 26 122 154 24 242 38 23 38 92 29 158 42 bd 63 40 19 31 47 24 31 104 26 70 36 4 36 24 bd 21 32 bd 24 66 bd 31 89 bd 32 25 bd 12 34 bd 34 18 3 23 6 bd 7 29 5 33 57 18a 56 43 10a 60 43 14a 38 109 77 4 485 0.89 bd 25 1373 64 726 34 42 184 508 1548 0.71 214 203 4 841 0.88 bd 21 509 42 409 31 34 122 343 981 0.84 31 26 1 157 0.82 bd 25 393 42 496 32 33 136 355 1094 0.72 93 62 3 437 0.59 bd 23 250 56 664 33 39 180 506 1478 0.76 47 36 2 190 0.75 bd 23 144 52 582 33 38 163 450 1318 0.77 25 21 1 137 0.81 bd 19 141 50 509 26 28 139 372 1124 0.73 25 23 1 151 0.81 bd 22 192 46 476 32 33 143 351 1081 0.74 51 38 1 290 0.73 bd 21 462 51 544 32 35 155 446 1263 0.83 23 13 2 114 0.64 bd 11 302 58 619 5 16 202 666 1566 1.08 7 8 bd 60 0.31 bd 5 463 28 368 bd 9 114 428 947 1.16 16 9 bd 81 0.67 bd 6 414 27 396 4 bd 118 540 1085 1.36 19 11 bd 127 0.61 bd 5 379 23 342 3 10 90 374 842 1.09 20 11 bd 152 0.63 bd 5 425 21 330 2 14 96 328 791 0.99 8 5 bd 49 0.63 bd 37 207 16 269 2 bd 69 333 689 1.24 23 37 bd 128 0.68 bd 3 628 17 273 bd bd 68 280 638 1.03 16 38 bd 98 0.70 bd 2 73 8 127 bd bd 36 180 351 1.42 5 3 bd 21 0.71 bd 3 81 9 154 4 bd 41 211 419 1.37 20 12 bd 99 0.61 bd 6 265 32 59 bd bd 105 443 739 2.79 42 35 2a 201 0.69 bd 15 367 36 413 19 28 120 395 997 1.09 51 47 1a 202 0.13 bd 11 296 18 177 15 12 48 118 358 0.49 26 20 2a 140 0.68 bd 10 287 30 370 10 24 109 378 927 1.02 510 382 771 549 562 392 387 405 577 426 562 621 701 431 629 319 360 508 505 126 491 AM, arithmetic mean; GM, geometric mean; bd, below detection, less than IDL. a Calculated from positive samples only. H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 a-HCH g-HCH a-HCH:gHCH Heptachlor Hept-epoxide transChlordane cis-Chlordane trans-Nonachlor cis-Nonachlor S Chlordanes TC:CC Aldrin Dieldrin Endosulfan-I o,p#-DDE p,p#-DDE o,p#-DDD p,p#-DDD o,p#-DDT p,p#-DDT S DDT p,p#-DDT: p,p#-DDE Toxaphene 10 Aug 2000 487 H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 3.1.5. Endosulfan-I AM and GM concentrations of endosulfan-I were 367 and 287 pg mÿ3. Samples 1, 2 and 15 showed higher levels, reflecting a pulsed input due to usage nearby at or close to the time of sampling. Endosulfan is still used in Mexico, including the Chiapas region. It has been found in surface waters in the state (Hernandez-Romero et al., 2004). The generally high concentrations measured during the entire sampling period are indicative of the quantities used in the region. 3.1.6. Dieldrin and aldrin Dieldrin was detected in all samples, but at very low levels, averaging AM Z 15 pg mÿ3 GM Z 10 pg mÿ3. Dieldrin is 4000 3000 2000 Air Sample 1000 0 5 6000 4 2 6 1 0 38 3.1.4. Toxaphene Total toxaphene AM and GM concentrations were 505 and 491 pg mÿ3. Toxaphene is a complex mixture of several hundred compounds (Hainzl et al., 1994). In addition to quantifying total toxaphene as the sum of the Cl7, Cl8, and Cl9 homologues, 3 4000 2000 Toxaphene } 3.1.3. Chlordanes The AM and GM concentrations of total chlordanes, sum of heptachlor C HEPX C TC C CC C TN C CN (S chlordanes), were 201 and 140 pg mÿ3, respectively. In the environment, TC degrades more rapidly than CC (Eitzer et al., 2001), and a ratio of TC/CC !1 is generally taken to be indicative of aged chlordanes (Bidleman et al., 2002). In the technical chlordane used in the United States, the proportions of TC/ CC were reported as 1.00/0.85 by one laboratory (Jantunen et al., 2000) and 1.00/1.05 by another (Mattina et al., 1999). The relative liquid phase vapour pressures of TC/CC at 25  C are 1.00/0.72 (Hinckley et al., 1990). Multiplying the technical chlordane composition by the relative volatility of the components gives the relative proportions of TC/CC expected in technical chlordane vapour: 1.00/0.61 or 1.00/0.76, depending on which set of technical chlordane compositional values is used. The proportions in ambient air from the AM and GM concentrations measured in this study were 1.00/.0.75 and 1.00/0.68 (Table 1). The ratio of TC/CC in air is quite similar to the expected vapour composition, indicating fresh chlordanes. Similarly, the ratio of TN/TC in technical chlordane is reported as 0.42 (Jantunen et al., 2000) and 0.76 (Mattina et al., 1999), the ratio of TN/TC vapour pressures is 0.57 (Hinckley et al., 1990), and the predicted ratio of TN/TC in vapour-phase technical chlordane is 0.24e0.43. Ratios of TN/TC in air from the AM and GM concentrations in Table 1 are 0.63 and 0.53, which suggests a slight enrichment of TN. This was also found by Eitzer et al. (2003), who measured higher than expected TN proportions in air above soils containing weathered chlordane residues. Heptachlor was detected in all samples, with AM and GM concentrations of 57 and 43 pg mÿ3. Concentrations showed considerable variability, ranging from 6 to 154 pg mÿ3. Heptachlor and Schlordane concentrations were closely correlated (r2 Z 0.68), not surprisingly since heptachlor is a component of technical chlordane. The metabolite HEPX was quantifiable in 10 samples with AM and GM concentrations of 18 and 14 pg mÿ3, excluding samples below detection. the profiles of octachlorobornane congeners in air were compared with that of technical toxaphene. Fig. 2 shows typical results. The six peaks labelled in Fig. 2 are mixtures of several co-eluting components as shown by multidimensional GC investigations of technical toxaphene and air samples collected near Lake Ontario (Shoeib et al., 2000). Prominent components of these peaks are the following congeners, identified using single congener standards (Bidleman and Leone, 2004b) and designated by AndrewseVetter nomenclature (Andrews and Vetter, 1995; Vetter and Oehme, 2000): 1 Z B8-1413, 2 Z B8-1412, 3 Z B8-531, 4 Z B8-1414 C B8-1945, 5 Z B8806 C B8-809, 6 Z B8-2229 C unknown component. Peaks 3 and 5 are depleted in the air samples when compared to the technical mixture. This same pattern has been seen in air and soils in the southern United States (Bidleman and Leone, 2004b; Bidleman et al., 2004; Harner, 1999; Jantunen et al., 2000) and indicates that the toxaphene is from weathered residues and not from fresh sources. Toxaphene has been reported in Nicaraguan cotton field soils (Carvalho et al., 2003) at concentrations similar to those in the southern United States (Bidleman and Leone, 2004a, b), suggesting soils in the region are potential sources of toxaphene in ambient air. Abundance reported by Shen et al. (2004) noted above supports our hypothesis of continued use of lindane in the study region. Waite (2001) reported air concentrations of lindane ranging from !100e2700 pg mÿ3 at a control site in the Canadian Prairies 2 km from a canola field that had been planted with lindane-treated seeds. The control site had not been planted with lindane-treated seeds, so the air concentrations are thought to represent background air concentrations for the region during the canola-growing season. The mean levels at our study site (103 pg mÿ3) agreed with the lower end of the range, supporting our hypothesis of continued use of lindane in the study region. 40 42 44 46 48 Minutes Fig. 2. Chromatographic profiles of octachlorobornanes in Chiapas air and technical toxaphene. Major components of the indicated peaks are: 1, B8-1413; 2, B8-1412; 3, B8-531; 4, B8-1414 C B8-1945; 5, B8-806 C B8-809; 6, B8-2229 C unknown component. 488 H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 legally banned in Mexico and all neighbouring countries, which explains the low levels in this study. Aldrin was below detection in all samples. Aldrin is also banned in Mexico and surrounding countries. 3.2. Potential sources of pesticides In an effort to determine the potential sources of pesticides measured in air in Chiapas, air parcel back trajectories were calculated (at several altitudes) using the U.S. National Atmospheric and Oceanic Administration (NOAA) Hysplit4 model. The predominant airflow directions were from the E-NE (passing through Guatemala, Honduras, El Salvador, and sometimes other areas of southern Mexico and Nicaragua) and SE (blowing from the coast but having usually passed through Guatemala and Honduras). Some of the air masses were tracked back to the southern United States and Cuba. No clear relationships emerged to indicate a predominant source direction for the OC pesticides. The fact that air parcels for all samples passed through southern Mexico and, in most cases, parts of Central America before arriving at Tapachula makes it difficult to distinguish between local/regional sources and distant transport on the basis of air pathways alone. As noted earlier, the p,p#-DDT/p,p#-DDE ratio w1 and the relatively high p,p#DDT concentrations suggest a combination of current usage and re-emission sources, TC/CC ratios indicate current usage and/or unweathered termiticide emissions, while elevated TN proportions and toxaphene congener profiles are consistent with soil emissions. It is likely that the pesticides measured in this study represented a mixture of fresh and weathered sources. This may reflect the fact that air masses travelled over regions where OC pesticides are still being used and emitted from weathered sources (Central America and southern Mexico) as well as regions where only weathered sources (southern United States) are expected. Our results are thus consistent with both regional and longer-range atmospheric transport. A confounding factor in trying to determine sources of pesticides measured in air is their unauthorised use in the region. In personal conversations with farmers in the state, we ascertained that DDT and toxaphene were being used in agriculture despite official bans. Sources were variously ascribed to existing stockpiles and purchase across the border in Guatemala. We caution that we did not carry out a formal, scientific survey of farmers, but simply spoke with several farmers encountered while travelling near Tapachula. In addition, it was unclear after conversations with public health workers whether DDT was still being used in 2000e2001. 3.3. Comparison to other studies and regions Table 2 compares levels of selected pesticides in Chiapas with other measurements in potential source and receptor regions. In 1995e1996, OC pesticide concentrations were measured in Belize, Central America, (Alegria et al., 2000). Interestingly, there are marked, statistically significant differences (unpaired t-tests at 95% confidence interval using Excel software) between Chiapas and Belize even though the spatial distance between sampling sites is not very large (w500 km) (Table 2). Whereas in Belize levels of dieldrin and aldrin were greatly elevated (AMs of 775 pg mÿ3 and 657 pg mÿ3, respectively in Belmopan), dieldrin levels in Chiapas were moderate (AM of 15 pg mÿ3) and aldrin was below detection in all samples. This marked difference in dieldrin concentrations was not simply due to the 4e5 year difference between sampling at the two locations. In their 2000e2001 passive air sampling campaign, Shen et al. (2005) also found much higher levels of dieldrin in Belmopan, Belize (260 pg mÿ3) compared to levels in Tapachula (AM 15 pg mÿ3). In our studies, toxaphene was an order of magnitude higher (AMs 505 pg mÿ3 vs. 35 and 29 pg mÿ3) and chlordanes were 2e3 times higher (AMs 200 pg mÿ3 vs. 76 and 78 pg mÿ3) in Chiapas than in Belize. Concentrations of DDTs were statistically similar (unpaired ttests at 95% confidence interval using Excel software) in both areas. DDTs in Chiapas and Belize were, for the most part, much higher than those measured in the southern United States. Exceptions were in Mississippi (Coupe et al., 2000) and Arkansas (Hoh and Hites, 2004) where concentrations of p,p#-DDE rivalled those in Chiapas and Belize. DDTs in Chiapas and Belize were 1e2 orders of magnitude above levels in the Great Lakes and 3 orders of magnitude above those in the Canadian Arctic (Table 2). Thus, the southern Mexicoe Central America region may be a source of DDTs to the rest of North America. Toxaphene and chlordane were also higher in Chiapas than in the Great Lakes and Arctic receptor regions. However, concentrations of both pesticides in the air of the southern United States were of the same magnitude as those in Chiapas. In addition, levels in the southern states were about 10-fold higher than those in Belize (Table 2). The toxaphene congener profiles in both Chiapas and the southern states suggest a weathered source, probably emission from soils. Thus, depending on the direction of air mass movement, southern Mexico and Central America may be sometimes a source and sometimes a receptor region for toxaphene and chlordanes (impacted by the southern United States). Table 2 also compares our measurements in Chiapas and Belize to results of a North American wide campaign with PAS carried out in 2000e2001 by Shen et al. (2004, 2005). The PAS consisted of XAD-2 resin contained in porous stainless steel tubes. Deployed for one year, each PAS sampled approximately 190 m3 of air (Shen et al., 2005) and yielded one integrated air concentration for the year. The two sampling programs gave air concentrations agreeing within a factor of two for DDTs and HCHs in Chiapas and for DDTs and dieldrin in Belize. Concentrations of a-endosulfan in Chiapas also agreed excellently between our measurements (AM Z 367 pg mÿ3) and the PAS campaign (350 pg mÿ3). However, PAS-derived air concentrations were lower for HCHs in Belize, dieldrin in Chiapas and chlordanes in both locations. 489 H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 Table 2 Selected OC pesticides in ambient air of source and receptor regions, ranges or arithmetic means (pg mÿ3) p,p#-DDT C p,p#-DDE Great Lakes Ontario Point Petre Erie Sturgeon Point Huron Burnt Island Michigan S. Bear Dunes S. Bear Dunes S. Bear Dunes Open Lake Superior Brule River Pukaskwa Eagle Harbor Eagle Harbor Open Lake Open Lake Canada Arctic S Chlordanesa 24 20 32 41 3.3 5.7 11 16 8.7b 39 3.3 2.5 4.5 9.1 4.7 9.4 0.49 1.5 Prairies Southern U.S. Muscle Shoals, AL Muscle Shoals, AL Columbia, SC Rohwer, AR Rohwer, AR Lubbock, TX Galveston Bay, TX Houston, TX Rolling Forks, MS Cocodrie, LA C. America/Mexico Belize City, Belize Belmopan, Belize Belmopan, Belize Cheturnal, Mexico Costa Rica, C.A. Tapachula, Chiapas a b c d a- C gHCH ÿ ÿ ÿ83 ÿ ÿ83 ÿ ÿ5.8 ÿ ÿ100 ÿ ÿ ÿ ÿ ÿ90 ÿ104 ÿ97 ÿ ÿ ÿ ÿ ÿ58 ÿ ÿ!100ÿ2700d 290b 200 19 94 670b 3.6b 59 ÿ ÿ142 ÿ113 ÿ ÿ ÿ ÿ ÿ214 ÿ404d ÿ ÿ 408 850 440 350 14 808 78 76 16 1.2 5.4 200 ÿ ÿ36 ÿ44 ÿ7.6 18 31 ÿ103 10b 71 98.1 84 180 Dieldrin Toxaphene Year(s) Ref. 2001e01 Shen et al. (2004, 2005) 1996e98 Buehler et al. (2001) 2000e01 Shen et al. (2004, 2005) 1996e98 Buehler et al. (2001) 2002e03 Hoh and Hites (2004) Buehler et al. (2001) !0.1ÿ63 3.0ÿ54 17.0ÿ41 1996e98 2000e01 1996e98 1997 1997 1996e97 5 1993e97 12 Endosulfan-I 93 24 6.8 18 18 21 23 11 1.9 12 1 38 25 12 176 105 189 950c 1400 160c 19 61 37 775 260 1.5 2.8 15 29 35 505 4.7 63 58 367 Buehler et al. (2001) Glassmeyer et al. (1999) James et al. (2001) Jantunen and Bidleman (2003) 1997e98 Hung et al. (2002) Macdonald et al. (2000) Waite (2001) 1996e97 2000e01 1994e95 2000e01 2002e03 2000e01 1995e96 1999e00 1995 2002e03 Jantunen et al. (2000) Shen et al. (2004, 2005) Bidleman et al.(1998) James and Hites (2002) Hoh and Hites (2004) James and Hites (2002) Park et al. (2001) Offenberg et al. (2004) Coupe et al. (2000) Hoh and Hites (2004) 1995e96 1995e96 2000e01 2000e01 Alegria et al. (2000) Alegria et al. (2000) Shen et al. (2004, 2005) Shen et al. (2004, 2005) Shen et al. (2004, 2005) This study 2000e01 TC C CC C TN. p,p0 -DDE only. Adjusted to 288 K. g-HCH only. 4. Conclusions Measurements in Chiapas, Mexico show that concentrations of several OC pesticides (DDTs, chlordanes, and toxaphene) are elevated in ambient air compared to those in the Great Lakes region, while other pesticides are not (HCHs and dieldrin). While this suggests southern Mexico as a source region for the former group of chemicals, comparably high levels have also been reported in parts of the southern U.S. where their suspected sources are soil emissions (DDTs, toxaphene) and termiticide usage (chlordanes). Ratios of p,p#- DDT/p,p#-DDE and TC/CC in Chiapas suggest a mixture of fresh and weathered sources, while congener profiles of toxaphene suggest emission of old residue from soils. This is supported by air parcel back trajectory analysis, which indicated that air masses over Chiapas at the time of sampling passed over areas of continuing or recent use of some OC pesticides as well as areas of past use. The measurements presented here represent a further step in clarifying the significance of Central America and Mexico as a region for OC pesticide emission. A more comprehensive sampling programme is needed to obtain a clearer spatial 490 H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 picture for Mexico, to distinguish emissions from current usage and legacy sources, and to define regional differences such as those seen between Chiapas and Belize. Such information would allow emissions from the region to be placed in perspective with the emissions of old OC pesticide residues from soils in the United States and Canada. Acknowledgements Thanks to the students at the Universidad Autonoma de Chiapas who helped with sampling. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (http://www.arl.noaa.gov/ready.html) used in this publication. References Alegria, H.A., Bidleman, T.F., Shaw, T.J., 2000. Organochlorine pesticides in ambient air of Belize, Central America. Environmental Science and Technology 34, 1953e1958. Andrews, P., Vetter, W., 1995. A systematic nomenclature system for toxaphene congeners. Part l: Chlorinated bornanes. Chemosphere 31, 3879e 3886. Anonymous, 2001. North America ahead of the game on DDT elimination. Trio Newsletter 4, North American Commission for Environmental Cooperation, Montreal. http://www.cec.org/trio/stories/index.cfm?edZ4&DZ 51&varlanZenglish. Aulagnier, F., Poissant, L., 2005. Some pesticides occurring in air and precipitation in Quebec, Canada. Environmental Science and Technology 39, 2960e2967. Bidleman, T.F., Leone, A.D., 2004a. Soil-air exchange of organochlorine pesticides in the southern United States. Environmental Pollution 128, 49e57. Bidleman, T.F., Leone, A.D., 2004b. Soil-air relationships for toxaphene in the southern United States. Environmental Toxicology and Chemistry 23, 2337e2342. Bidleman, T.F., Alegria, H., Ngabe, B., Green, C., 1998. Trends of chlordane and toxaphene in ambient air of Columbia, South Carolina. Atmospheric Environment 32, 1849e1856. Bidleman, T.F., Jantunen, L.L.M., Helm, P.A., Brostrom-Lunden, E., Juntto, S., 2002. Chlordane enantiomers and temporal trends of chlordane isomers in Arctic air. Environmental Science and Technology 36, 539e 544. Bidleman, T.F., Cussion, S., Jantunen, L.M., 2004. Interlaboratory study of toxaphene analysis in ambient air. Atmospheric Environment 38, 3713e 3722. Blais, J.M., Schindler, D.W., Muir, D.C.G., Kimpe, L.E., Donald, D.B., Rosenberg, B., 1998. Accumulation of persistent organochlorine compounds in mountains of western Canada. Nature 395, 585e588. Breivik, K., Pacyna, J.M., Münch, J., 1999. Use of a-, b-, and g-hexachlorocyclohexane in Europe, 1970e1996. Science of the Total Environment 239, 151e163. Buehler, S.S., Basu, I., Hites, R.A., 2001. A comparison of PAH. PCB and pesticide concentrations in air at two rural sites on Lake Superior Environmental Science and Technology 35, 2417e2422. Carvalho, F.P., Montenegro-Guillen, S., Villeneuve, J.-P., Cattini, C., Tolosa, I., Bartocci, J., Lacayo-Romero, M., Cruz-Granja, A., 2003. Toxaphene residues from cotton fields in soils and in the coastal environment of Nicaragua. Chemosphere 53, 627e636. Castillo, L.E., de la Cruz, E., Ruepert, C., 1997. Ecotoxicology and pesticides in tropical aquatic ecosystems of Central America. Environmental Toxicology and Chemistry 16, 41e51. Cortes, D.R., Hites, R.A., 2000. Detection of statistically significant trends in atmospheric concentrations of semivolatile compounds. Environmental Science and Technology 34, 2826e2829. Coupe, R.H., Manning, M.A., Foreman, W.T., Goolsby, D.A., Majewski, M.S., 2000. Occurrence of pesticides in rain and air in urban and agricultural areas of Mississippi, AprileSeptember, 1995. Science of the Total Environment 248, 227e240. Donald, D.B., Syrgiannis, J., Crosley, R.W., Holdsworth, G., Muir, D.C.G., Rosenberg, B., Sole, A., Schindler, D.W., 1999. Delayed deposition of organochlorine pesticides at a temperate glacier. Environmental Science and Technology 33, 1794e1798. Eitzer, B.D., Mattina, M.J.I., Iannuchi-Berger, W., 2001. Compositional and chiral profiles of weathered chlordane residues in soil. Environmental Toxicology and Chemistry 20, 2198e2204. Eitzer, B.D., Iannucci-Berger, W., Mattina, M.J.I., 2003. Volatilization of weathered chiral and achiral chlordane residues from soil. Environmental Science and Technology 37, 4887e4893. Glassmeyer, S.T., Brice, K.A., Hites, R.A., 1999. Atmospheric concentrations of toxaphene on the coast of Lake Superior. Journal of Great Lakes Research 25, 492e499. Hainzl, D., Burhenne, J., Parlar, H., 1994. Theoretical consideration of the structural variety in the toxaphene mixture, taking into account recent experimental results. Chemosphere 28, 245e251. Halsall, C.J., Bailey, R., Stern, G.A., Barrie, L.A., Fellin, P., Muir, D.C.G., Rosenberg, B., Rovinsky, F.Y., Kononov, E.Y., Pastukhov, B., 1998. Multi-year observations of organohalogen pesticides in the Arctic atmosphere. Environmental Pollution 102, 51e62. Harner, T., Wideman, J.L., Jantunen, L.M., Bidleman, T.F., Parkhurst, W.J., 1999. Residues of organochlorine pesticides in Alabama soils. Environmental Pollution 106, 323e332. Harner, T., Shoeib, M., Diamond, M., Stern, G., Rosenberg, B., 2004. Using passive air samplers to assess urban-rural trends for persistent organic pollutants. 1. Polychlorinated biphenyls and organochlorine pesticides. Environmental Science and Technology 38, 4474e4483. Hernandez-Romero, A.H., Tovilla-Hernandez, C., Malo, E.A., BelloMendoza, R., 2004. Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico. Marine Pollution Bulletin 48, 1130e 1141. Hinckley, D.A., Bidleman, T.F., Foreman, W.T., Tuschall, J.R., 1990. Determination of vapor pressures for nonpolar and semipolar organic compounds by capillary gas chromatography. Journal of Chemical and Engineering Data 35, 232e237. Hoh, E., Hites, R.A., 2004. Sources of toxaphene and other organochlorine pesticides in North America as determined by air measurements and potential source function contribution analysis. Environmental Science and Technology 38, 4187e4194. Hung, H., Halsall, C.J., Blanchard, P., Li, H.H., Fellin, P., Stern, G., Rosenberg, B., 2002. Temporal trends of organochlorine pesticides in the Canadian Arctic atmosphere. Environmental Science and Technology 36, 862e868. Hung, H., Blanchard, P., Halsall, C.J., Bidleman, T.F., Stern, G.A., Fellin, P., Muir, D.C.G., Barrie, L.A., Jantunen, L.M.., Helm, P.A., Ma, J., Konoplev, A., 2004. Temporal and spatial variabilities of atmospheric polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and polychlorinated aromatic hydrocarbons in the Canadian Arctic: Results from a decade of monitoring. Science of the Total Environment 342, 119e144. James, R.R., Hites, R.A., 2002. Atmospheric transport of toxaphene from the southern United States to the Great Lakes region. Environmental Science and Technology 36, 3474e3481. James, R.R., McDonald, J.G., Symonik, D.M., Swackhamer, D.L., Hites, R.A., 2001. Volatilization of toxaphene from Lakes Michigan and Superior. Environmental Science and Technology 35, 3653e3660. Jantunen, L.M., Bidleman, T.F., 2003. Air-water gas exchange of toxaphene in Lake Superior. Environmental Toxicology and Chemistry 22, 1229e1237. Jantunen, L.M.M., Bidleman, T.F., Harner, T., Parkhurst, W.J., 2000. Toxaphene, chlordane, and other organochlorine pesticides in Alabama air. Environmental Science and Technology 34, 5097e5105. H. Alegria et al. / Environmental Pollution 140 (2006) 483e491 Jaward, F.M., Farrar, N.J., Harner, T., Sweetman, A.J., Jones, K.C., 2004. Passive air sampling of PCBs, PBDEs and organochlorine pesticides across Europe. Environmental Science and Technology 38, 34e41. Larsson, P., Berglund, O., Backe, C., Bremle, G., Eklöv, A., Järnmark, C., Person, A., 1995. DDT fate in tropical and temperate regions. Naturwissenschaften 82, 559e561. Leonard, H.J., 1990. Natural resources and economic development in Latin America: A regional environmental profile; International Institute for Environment and Development. Li, Y.-F., 2001. Toxaphene in the United States: 1. Usage gridding. Journal of Geophysical Research 106, 17919e17927. Li, Y.-F., Macdonald, R.W., 2005. Sources and pathways of selected organochlorine pesticides to the Arctic and the effect of pathway divergence on HCH trends in biota: A review. Science of the Total Environment 342, 87e106. Lopez-Carrillo, L., Torres-Arreola, L., Torres-Sanchez, L., Espinosa-Torres, F., Jimenez, C., Cebrian, M., Waliszewski, S., Saldate, O., 1996. Is DDT use a public health problem in Mexico? Environmental Health Perspectives 104, 584e588. Macdonald, R.W., Barrie, L.A., Bidleman, T.F., Diamond, M.L., Gregor, D.J., Semkin, R.G., Strachan, W.M.J., Li, Y.F., Wania, F., Alaee, M., Alexeeva, L.B., Backus, S.M., Bailey, R., Bewers, J.M., Gobeil, C., Halsall, C.J., Harner, T., Hoff, J.T., Jantunen, L.M.M., Lockhart, W.L., Mackay, D., Muir, D.C.G., Pudykiewicz, J., Reimer, K.J., Smith, J.N., Stern, G.A., Schroeder, W.H., Wagemann, R., Yunker, M.B., 2000. Contaminants in the Canadian Arctic: 5 years of progress in understanding sources, occurrence and pathways. The Science of the Total Environment 254, 93e234. Marvin, C., Painter, S., Williams, D., Richardson, V., Rossmann, R., Van Hoof, P., 2004. Spatial and temporal trends in surface water and sediments contamination in the Laurentian Great Lakes. Environmental Pollution 129, 131e144. Mattina, M.J.I., Iannucci-Berger, W., Dykas, L., Pardus, J., 1999. Impact of long-term weathering, mobility and land use on chlordane residues in soil. Environmental Science and Technology 33, 2425e2431. Moody, J., 2003. North America eliminates use of chlordane. Trio Newsletter 4, North American Commission for Environmental Cooperation, Montreal. !http://www.cec.org/trio/stories/index.cfm?edZ9&IDZ111&varlanZ englishO. Mora, M., 1997. Transboundary pollution: Persistent organochlorine pesticides in migrant birds of the southwestern United States and Mexico. Environmental Toxicology and Chemistry 16, 3e11. NACEC, 2004. History of DDT use in North America to 1997. !http://www. cec.org/files/pdf/POLLUTANTS/HistoryDDTe_EN.PDFO. 491 Ngabe, B., Bidleman, T.F., 1992. Occurrence and vapor particle partitioning of heavy organic compounds in ambient air in Brazzaville, Congo. Environmental Pollution 76, 147e156. Offenberg, J.H., Naumova, Y.Y., Turpin, B.J., Eisenreich, S.J., Morandi, M.T., Stock, T., Colome, S.D., Winer, A.M., Spektor, D.M., Zhang, J., Weisel, C.P., 2004. Chlordanes in the indoor and outdoor air of three U.S. cities. Environmental Science and Technology 38, 2760e2768. Park, J.-S., Wade, T., Sweet, S., 2001. Atmospheric deposition of organochlorine contaminants to Galveston Bay, Texas. Atmospheric Environment 35, 3315e3324. Rodezno, R.A., 1997. Plaguicida y salud en Nicaragua. In: Memorias del Congreso Nacional Sobre Impacto de los Plaguicidas en Ambiente, Salud, Trabajo y Agricultura. Managua, Nicaragua, 27e31 October 1997, Managua, OPS-OMS, pp. 464e482. Shen, L., Wania, F., Lei, Y.D., Teixeira, C., Muir, D.C.G., Bidleman, T.F., 2004. Hexachlorocyclohexanes in the North American atmosphere. Environmental Science and Technology 38, 965e975. Shen, L., Wania, F., Lei, Y.D., Teixeira, C., Muir, D.C.G., Bidleman, T.F., 2005. Atmospheric distribution and long-range transport behavior of organochlorine pesticides in North America. Environmental Science and Technology 39, 409e420. Shoeib, M., Brice, K.A., Hoff, R.M., 2000. Studies of toxaphene in the technical standard and extracts of background air samples (Point Petre, Ontario) using multidimensional gas chromatographyeelectron capture detection. Chemosphere 40, 201e211. Van Drooge, B.L., Grimalt, J.O., Garcia, C.J.T., Cuevas, E., 2002. Semivolatile organochlorine compounds in the free troposphere of the northeastern Atlantic. Environmental Science and Technology 36, 1155e1161. Vetter, W., Oehme, M., 2000. Toxaphene: analysis and environmental fate of congeners. In: Paasivirta,, J. (Ed.), Handbook of Environmental Chemistry, vol. 3, Part K, New Types of Persistent Halogenated Compounds. Springer, Berlin, pp. 237e287. Waliszewski, S.M., Aguirre, A.A., Infanzon, R.M., Silva, C.S., Sileceo, J., 2001. Organochlorine pesticide levels in maternal adipose tissue, maternal blood serum, umbilical cord serum and milk from inhabitants of Veracruz, Mexico. Archives of Environmental Contamination and Toxicology 40, 432e438. Waite, D., Gurprasad, N., Sproull, J., Quiring, D., Kotylak, M., 2001. Atmospheric movements of lindane (gamma-HCH) from canola fields planted with treated seed. Journal of Environmental Quality 30, 768e775.