outdoor PAH air pollution in Brazil

Environmental Pollution 169 (2012) 210e216

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Influence of sugarcane burning on indoor/outdoor PAH air pollution in Brazil Joyce Cristale a, *,1, Flávio Soares Silva b, Guilherme Julião Zocolo a, Mary Rosa Rodrigues Marchi a a b

Analytical Chemistry Department, Institute of Chemistry, Unesp e Univ Estadual Paulista, P.O. Box 355, 14800-900 Araraquara, SP, Brazil Federal University of Itajubá e UNIFEI, Institute of Exact Sciences (ICE), Av. BPS, 1303, 37500-903 Itajubá, MG, Brazil

a r t i c l e i n f o

a b s t r a c t

Article history: Received 26 March 2012 Accepted 31 March 2012

This work presents the influence of sugarcane burning on PAH levels and their profiles at a residence located in Araraquara (SP, Brazil), a city surrounded by sugarcane plantations. The average concentrations of total PAHs (SPAHs) associated with atmospheric particulate matter were higher during the burning period (SPAHs 22.9 ng m
3) than in the non-burning period (SPAH 2.35 ng m
3). A comparison of our results with previous studies regarding PAH levels and their profiles in Araraquara outdoor air indicated that sugarcane burning was the main PAH air source in the indoor harvesting season samples. The benzo[a] pyrene equivalent (BaPeq) was used for cancer risk assessment, and higher average values were obtained in the harvesting season air samples (1.7 ng m
3) than in the non-harvesting air samples (0.07 ng m
3). These findings suggest that sugarcane burning during the harvesting season can represent a public health risk in affected cities. Ó 2012 Elsevier Ltd. All rights reserved.

Keywords: Indoor air PAH Sugarcane Biomass burning

1. Introduction Human exposure to polycyclic aromatic hydrocarbons (PAHs) and their derivatives deserves special attention because of their association with an increased incidence of several types of cancers (Gammon and Santella, 2008; Okona-Mensah et al., 2005; Rybicki et al., 2006). PAHs are a class of chemicals characterized by the presence of two or more condensed aromatic rings. These substances are ubiquitously distributed and are found as complex mixtures in all environmental compartments (Ravindra et al., 2008). PAHs in air have been studied in the recent decades, and high concentrations of these substances have been found in both indoor and outdoor air (Gevao et al., 2007; Gustafson et al., 2008; Makkonen et al., 2010; Meijer et al., 2008; Ohura et al., 2002; Zhu and Wang, 2003; Martellini et al., 2012). PAH sources include organic-material combustion processes (particularly diesel or gasoline engines), cigarette smoke, coke gasification, some industrial processes (e.g., aluminum production) and biomass burning (Ravindra et al., 2008; Katsoyiannis et al., 2011). Biomass burning at Brazilian sugarcane plantations has caused an increase in PAH outdoor air concentrations of cities surrounded by this crop (de Andrade et al., 2010; Magalhães et al., 2007; Silva et al.,

* Corresponding author. E-mail addresses: [email protected] (J. Cristale), fl[email protected] (F.S. Silva), [email protected] (G.J. Zocolo), [email protected] (M.R.R. Marchi). 1 Present address: Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18-26, 08034 Barcelona, Catalonia, Spain. 0269-7491/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2012.03.045

2010). Brazil is the world’s largest producer of sugarcane (569 million tons of sugarcane in 2008e09) (UNICA, 2010). Each year, during the sugarcane harvesting season, from May to November, plantations are burnt to facilitate the process of manual harvesting and to increase the sugar content by weight via water evaporation. The sugarcane burning generates large amounts of smoke and soot containing numerous compounds, including PAHs, that are released to the atmosphere and could potentially reach urban centers (de Andrade et al., 2010; Godoi et al., 2004; Zamperlini et al., 1997). Sao Paulo State (SE, Brazil) is the largest Brazilian sugarcane producer and is responsible for the 60% of the national production. Several studies were carried out in Araraquara (Sao Paulo, Brazil) to determine the influence of sugarcane plantation burnings on outdoor air pollution (de Andrade et al., 2010; Godoi et al., 2004; Magalhães et al., 2007; Silva et al., 2010; Zamperlini et al., 1997). Araraquara is a moderately industrialized city with approximately 210 000 inhabitants and is surrounded by sugarcane plantations. de Andrade et al. (2010) reported that the total PAH concentration (SPAH) in PM10 collected in Araraquara during the harvesting and non-harvesting seasons, from 2002 to 2004, were 11.6 and 2.5 ng m
3, respectively. The high PAH levels during the harvesting season were attributed to sugarcane burning and motor exhaust. Silva et al. (2010) assessed the potential cancer risk of human exposure to PAHs and PM2.5 (fine particulate matter) in Araraquara from 2008 to 2009 and reported a doubled increase during the harvesting season. Even though the PAH outdoor air pollution associated with the burning of sugarcane plantations has been widely studied in Brazil, no data is to date available concerning the influence of this activity

J. Cristale et al. / Environmental Pollution 169 (2012) 210e216

on PAH indoor air pollution. Considering that people spend most of their time indoors (Klepeis et al., 1996; Ohura et al., 2002), a proper evaluation of the human health risk from exposure to atmospheric pollution requires a detailed knowledge of these pollutants levels indoors. Previous studies reported that the principal indoor sources of PAHs include smokers, cooking, heating, and biomass combustion while cooking (Slezakova et al., 2009; Zhu and Wang, 2003; Menichini et al., 2007; Bhargava et al., 2004). However, additional studies have indicated that outdoor sources are primarily responsible for the high PAH levels in the indoor air of residences located in polluted areas (Fromme et al., 2004; Li et al., 2005b). The aim of this study was to determine the presence and profile of PAHs in indoor air during the sugarcane harvesting and non-harvesting seasons in Araraquara (SP, Brazil). These results were compared to the outdoor PAH data for the same location, and an estimate of the potential cancer risk of an indoor environment during the sugarcane harvesting season was determined. To the best of our knowledge, this is the first study with respect to PAH pollution in Brazilian residential air. 2. Experimental 2.1. Chemicals and materials HPLC-grade solvents used in this study were: dichloromethane, methanol, n-hexane, acetone, and acetonitrile (J.T. Baker, USA). A standard mixture solution of 13 PAHs was prepared from solid standards of each PAH: phenanthrene (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr), benz[a]anthracene(B(a)A), chrysene (Chry), benzo[b]fluoranthene (B(b)F), benzo[k]fluoranthene (B(k)F), benzo[a]pyrene (B(a)P), benzo[e]pyrene (B(e)P), dibenz[ah]anthracene (D(ah)A), benzo[ghi]perylene (B(ghi)P), and Indeno[1,2,3-cd]pyrene (IP). Benzo[k]fluoranthene and benzo[ghi]perylene solid PAH standards were provided by SigmaeAldrich Brazil. The remaining solid PAH standards (purity > 98%) were obtained from Dr. Ehrenstorfer GmbH (Augsburg, Germany). The reference material CRM 1649a (urban dust) was purchased from the National Institute of Standards and Technology (NIST, Gaithersburg, MD, USA). Sampling filters (PFTE, 37 mm) were purchased from Millipore (Massachusetts, USA). 2.2. Indoor sampling Araraquara is located in the central region of São Paulo, 21 470 3100 latitude and 48 100 5200 longitude. The city has a tropical altitude climate, which is influenced by the altitude and presents lower temperatures than the tropical climate. This type of climate is typical for the southeast of Brazil and is characterized by two well-defined seasons: one with high temperatures (average of 31  C) and high rainfall (September to May) and another with warm temperatures (average 20  C) and low rainfall (June to August). The total area of Araraquara city is 1312 km2, with approximately 80 km2 occupied by urban space. The agricultural area surrounding Araraquara is divided between predominantly sugarcane and orange plantations. The sampling was conducted inside a one-story house located in the urban area of Araraquara city. The house was approximately 10 m from a light-trafficked road and 300 m from a highway. In this house, there were no smokers, central heating, or biomass burnt for cooking. The sampling method was based on the NIOSH recommendations for occupational environments (NIOSH, 1998). The sampling pump used was a low-volume Buck Basic-5 (Buck, USA) operating at 2 L/min. A PFTE filter was used for sampling the atmospheric particulate material. Four of these systems were used simultaneously for each sampling event. The sampling was carried out for 25 days in August 2007 and 25 days in January 2008, representing the sugarcane harvesting and non-harvesting seasons, respectively. Air samples were collected in the living room for 8 h per day, from 0:00 to 8:00 h. The choice of daily collection time took into account a regulation enacted by the São Paulo State government (SMA, 2007) that prohibits sugarcane plantation burning between 6:00 and 20:00 h. This sampling time was also chosen to simulate the human exposure during sleep. It was also assumed that people spend less time indoors in tropical climate countries than in temperate climate regions like Europe or North America. The predominant wind direction was not an important factor in data interpretation. Araraquara is surrounded by sugarcane plantations and burning events were randomly distributed and occurred continuously and simultaneously in different areas during the harvesting season. 2.3. Chromatographic analysis Each four filters set were extracted together, resulting in one extract per sampling day. PAH extraction was performed using 3 volumes of 20 mL of hexane/ acetone 1:1 (v/v) in an ultrasonic bath for 10 min. The solvent extraction volume was reduced to approximately 3 mL in a rotating evaporator, and then to near-dryness

211

under an N2 flow. The residue was dissolved in 600 mL of acetonitrile and analyzed by HPLC/fluorescence. Thirty microliters of extract was injected into an HPLC Pro Star (Varian, Walnut Creek, CA, USA) equipped with an autosampler 400 and a model 360 fluorescence detector. A SUPELCOSIL LC PAH column (250 mm  4.6 mm  5 mm; SUPELCO, Bellefonte, PA, USA) was used. The chromatographic conditions were optimized by Silva (2006). The mobile phase was acetonitrile/water in gradient elution mode: 60% acetonitrile for 5 min, followed by a linear increase until 100% acetonitrile was achieved (20 min), and then the 100% condition was maintained for 15 min. The fluorescence detector was operated with a 240-nm excitation wavelength (lex) and a 398-nm emission wavelength (lem); however, indeno[1,2,3-cd]pyrene was analyzed with 300 nm (lex) and 498 nm (lem) wavelengths (29.4e35.0 min). 2.4. Quality control The analyses were performed by external standard quantification. Each calibration curve was constructed with at least five points. The instrumental detection and quantification limits were calculated from the curve parameters (Thompson et al., 2002). The relative standard deviation (RSD) for the peak area of the standards, in triplicate, was on average 2.8% for all PAHs (range 0.1%e12%) at all levels of the calibration curve. The correlation coefficient (r2) was higher than 0.99 for all PAHs. The instrumental detection limits ranged from 0.03 to 3.7 ng mL
1, and the quantification limits were 0.07e7 ng mL
1 First, the performance of two solvent mixtures (dichloromethane/methanol 4:1 (v/v) and hexane/acetone 1:1 (v/v)) were compared using PAH extraction in an ultrasonic bath. Groups of four spiked PFTE filters with 0.3e12 ng of each PAH, and 1 mg of certified reference material NIST CRM-1649a (urban dust) were used. The recovery of each PAH with each solvent mixture was higher than 70% for both spiked PFTE filters and certified reference material. A significant difference between solvent extractions was not observed for any PAHs using spiked PFTE filters and reference material as measured by the Student’s t coefficient (95% confidence) below a reference value of 2.2281. The hexane/acetone (1:1) mixture was used for extraction because of its lower toxicity and rapid evaporation under an N2 flow. The accuracy of the method was studied using spiked air samples. The protocol recommended by the ICH (International Conference on Harmonization) for validation of analytical methods was used. This protocol required a minimum of nine determinations involving three different concentration levels and recoveries from 50 to 150% for trace analysis (Chan et al., 2004). Recoveries ranged from 58 to 88% for the PAHs at all levels of spiking (corresponding to the beginning, middle and the end of each PAH calibration curve) with RSDs below 14%. The quantification limit of the method (LOQ) was determined from the lowest spiked level with a recovery higher than 50% and an RSD lower than 20%. Under these criteria, LOQ was between 0.0088 and 1.2 ng m3 for each PAH. Table 1 shows the accuracy of the method results and the obtained LOQ values. Procedural blanks were performed in triplicate, using groups of four PFTE filters subjected to the extraction procedure.

3. Results and discussion 3.1. PAH concentrations Fig. 1 shows the results for each air sampling event. The amounts and PAH profiles were different between the harvesting (August 2007)

Table 1 Results of the method quantification study on spiked filters.

Phe Ant Fl Pyr BaA Chry B(e)P B(b)F B(k)F B(a)P D(ah)A B(ghi)P IP

Level 1 (ng)

Level 2 (ng)

Level 3 (ng)

Rec 1 (%)

0.35 0.034 0.88 0.30 0.23 0.23 0.62 0.095 0.050 0.10 2.9 4.7 0.57

8.7 0.84 22 7.5 5.6 5.8 15 2.4 1.2 2.5 73 117 14

35 3.3 87 30 22 23 61 9.5 4.9 10 294 470 56

69 74 65 69 58 78 74 58 71 52 74 74 78

            

Rec 2 (%) 8 7 5 5 5 8 9 6 8 5 7 7 9

73 76 71 78 68 83 71 62 70 54 72 70 88

            

Rec 3 (%) 9 8 9 9 8 8 6 6 4 5 8 8 11

78 73 72 74 67 75 69 67 71 59 70 71 81

            

LOQ (ng m
3) 6 5 6 7 7 8 7 7 6 4 6 6 8

0.091 0.0088 0.23 0.078 0.06 0.06 0.16 0.025 0.013 0.026 0.75 1.2 0.15

Level 1, 2, and 3 corresponds to the beginning, the middle and the end of the linear response curve of each PAH in the HPLC-Fluorescence system. Rec 1, 2 and 3 ¼ recovery for each level, respectively. LOQ ¼ limit of quantification for the whole analytical method, considering 3840 L (3.840 m3) sampling volume actually used in this study.

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Table 2 Comparison between our and reported PAH indoor levels studies. Sampling site

Measured PAH

Air sampling

United Kingdom urban area (Delgado-Saborit et al., 2011)

16

TSP

Porto, Portugal: house influenced by tobacco smoke and non-smoking house (Castro et al., 2011) Non-smoker houses in the Chicago area (Li et al., 2005a) Urban area houses in Guangzhou, China (Li et al., 2005b) Urban area in Taipei, Taiwan (Li and Ro, 2000) Homes with local wood combustion Kurkimak, Finland (Hellén et al., 2008) This Study

18

Gas phase þ PM2.5 þ PM10

15 19 15 16

gas phase þ TSP PM2.5 gas phase þ TSP PM10

13

TSP

SPAHs (ng m
3) Mean

Range

1.37 (homes)c 12 (pubsETS)c 66.7 (smoke)a 34.5 (non smoke)a 36a 43.5b 267c 22.5a

n.de25 (homes) 3.1e63 (pubsETS) 28.3e106 (smoke) 17.9e62.0 (non smoke) 2e147 14.18e77.89

Sugarcane harvesting season 4.82e44.8 22.9a Sugarcane non-harvesting season a 0.79e5.53 2.35

ETS e Environmental Tobacco Smoke. a Average. b Calculated average from published data. c Geometric mean.

and non-harvesting (January 2008) samples. Average concentrations of total PAHs (SPAHs) in total suspended particles (TSP) were higher in the samples from the harvest season. The SPAHs values were 22.9 ng m
3 (4.82e44.8 ng m
3) and 2.35 ng m
3 (0.79e5.53 ng m
3) for harvest and non-harvest seasons, respectively. All PAHs were detected in the harvesting season samples. The most abundant compounds were Phe, Flu, Pyr, B(e)P and B(g,h,i)P. In the non-harvesting season samples, the most abundant PAHs were Phe and Pyr, while some heavy PAHs, such as D(ah)A, B(ghi)P and IP, were not detected. Table 2 shows a comparison of SPAH between this study and other reported studies. Our SPAH levels from the harvesting season were higher than those reported in United Kingdom urban-area homes and sites with PAH specific sources, e.g., houses with local wood combustion in Finland and UK pubs where environmental tobacco smoke was present (Hellén et al., 2008; Delgado-Saborit et al., 2011). We measured 13 PAHs in the TSP and found that the harvesting season results were comparable with non-smoker houses in Porto (Portugal) and Chicago (USA) (Castro et al., 2011; Li et al., 2005a). On the other hand, our results were lower than urban area houses in China and Taiwan (Li et al., 2005b; Li and Ro, 2000). Thus, these harvesting season results point to sugarcane biomass burning as an outdoor PAH source that influences the indoor air quality and

this influence can be compared to other well known urban sources, such as vehicular emissions and some industrial activities. Fig. 2 shows a comparison of SPAH reported for Araraquara outdoor air in other studies (de Andrade et al., 2010; Silva et al., 2010). The outdoor and indoor SPAH in non-harvest season samples were statistically similar (p > 0.05). The outdoor and indoor SPAH harvest season samples were significantly different (p < 0.05). Our indoor results were approximately 2e3 times higher than reported in previously published studies. The lower reported outdoor levels during the harvest season in Araraquara in 2002e2004 (average of 11.2 ng m
3) and 2008e2009 (average of 7.67 ng m
3) suggest that indoor air pollution can reach higher values than outdoor air during the sugarcane harvesting season. The lower outdoor pollution levels were probably due to the atmosphere’s capacity to dilute analytes by intense displacement of air masses, which is not possible inside a residence. In addition, during atmospheric transport, PAHs are subjected to photo-oxidation processes with ozone, NO2, and OH radicals leading oxy- and nitro-PAH (Calvert et al., 2002; Esteve et al., 2006; Schauer et al., 2003). Thus, when outdoor particles infiltrate to the indoor environments through atmospheric transport, PAH particle-bound are protected from photoreactions. Ant, Pyr, B(a)P, B(a)A, B(ghi)P are more susceptible to photo-oxidation than their correspondent isomers Phe, Flu, B(e)P, Chry and Ip (Esteve et al., 2006;

Fig. 1. Multiple Box Whiskers for individual PAH concentration in indoor air samples from (a) harvesting and (b) non-harvesting sugarcane seasons. n e number of samples where the PAH was quantified.

J. Cristale et al. / Environmental Pollution 169 (2012) 210e216

213

not possible because the main PAH sources were different for each study, as discussed below. Other factor that could interfere on the degradability of PAH particle-bound generated by sugarcane burning is the crop burning time. During de Andrade et al. (2010) study there were no restrictions from Brazilian laws about the allowed time for burning of sugarcane plantations, so plantations were burned during both, day and night periods. On the other hand, at the time of our study, burning of sugarcane plantation has occurred only at night (SMA, 2007). Thus, PAH generated in the day time at de Andrade et al. (2010) study were affected by photoreactions during atmospheric transportation of the particles, while in this study this effect was less important because the burning of plantations have occurred at night. 3.2. Indoor versus outdoor and source identification P Fig. 2. Multiple Box Whiskers of PAH (ng m
3) in harvesting and non-harvesting seasons in different studied periods. Outdoor harvesting/non-harvesting 2002e2004 reported by de Andrade et al. (2010). Outdoor harvesting/non-harvesting 2008e2009 reported by Silva et al. (2010).

Robinson et al., 2006). Fig. 3 shows a comparison between this work and the results of de Andrade et al. (2010), revealing the relative contribution of each PAH for each sampling season. Fig. 3(a) (harvesting period) shows that the relative concentration of labile PAH such as Ant, Pyr, B(a)A, B(ghi)P is higher for indoor samples than for outdoor samples. Considering that the main PAH source during the harvesting season is the burning of sugarcane plantations (see next section), the present results suggest that these labile PAH are in higher levels in indoor environment because the PAH particlebound were protected from photo-oxidation. For the non-harvesting period, a qualitative comparison between these indoor and outdoor studies in terms of photoreaction and abundances of labile PAHs is

Relative Contribution (%)

a

Relative Contribution (%)

b

50 45 40 35 30 25 20 15 10 5 0

Indoor - Harvesting/2007 - 2008

Indoor - Non-Harvesting/2007-2008

In the present study, differences in PAH concentrations and profiles between samples from August 2007 (sugarcane harvesting season) and January 2008 (sugarcane non-harvesting season) suggested different sources in each period. No differences in indoor PAH sources between the seasons have occurred, and the absence of indoor PAH sources (smokers, heating or biomass burning for cooking) leads one to conclude that the observed results were from outdoor PAH sources. The similarities of our results with other studies that investigated Brazilian sugarcane burning air pollution (de Andrade et al., 2010; Godoi et al., 2004; Magalhães et al., 2007; Silva et al., 2010) point out the biomass burning from these plantations as the main source of the high PAH levels in the harvesting season indoor samples. de Andrade et al. (2010) reported on the contribution of sugarcane burning to PAH air pollution in Araraquara. This study attributed the high PAH levels in outdoor air samples from August 2002 and September 2003 mainly to sugarcane burning and transportation sources (diesel, gasoline, and natural gas). Their reported

Outdoor - Harvesting/2002-2004

Outdoor -Non-Harvesting 2002-2004

80 70 60 50 40 30 20 10 0

Fig. 3. PAH profile (individual PAH concentration/total PAH concentration) comparison between indoor air (this study) and outdoor air (de Andrade et al., 2010).

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data from an earlier study (2002e2004) were compared to our results. The outdoor air sampling point of de Andrade’s study was located 300 m from the sampling point of ours, and no significant differences in sugarcane burning amounts in Sao Paulo State occurred during the sampling periods of both studies. The Sao Paulo State sugarcane production for 2001e2002 and 2002e2003 were approximately 176 and 192 million tons, respectively (UNICA, 2010). Sugarcane burning and manual harvesting were the most-used practices. For 2006e2007, this production was 264 million tons (UNICA, 2010), and the total plantation area burned decreased to 65.8% (Aguiar et al., 2010). This reduction was due to a 2002 state law for the gradual elimination of the practice of sugarcane burning (Diario Oficial Estado de São Paulo, 2002). Thus, besides the increase in sugarcane production during 2006e2007 compared to 2001e2003, the emissions during the both periods are assumed to be fairly similar, because of the relative decrease in sugarcane burning area. Fig. 3(a) shows the harvesting season results obtained in this study and those obtained by de Andrade et al. (2010) in terms of relative contribution of each PAH. The PAH profiles were similar for both studies. Phe, Flu, B(e)P and B(ghi)P were the predominant PAHs in both studies, while this study observed a higher contribution of Pyr. PAH profile similarities for both studies in harvesting season suggested the same main PAH sources. Our work and de Andrade’s results are also in agreement with respect to the SPAH levels during each season. de Andrade et al. (2010) reported that the SPAH average concentration was five times higher for harvesting versus non-harvesting samples. Our results for indoor PAH levels were ten times higher for harvesting versus non-harvesting samples (see Fig. 2). In regions affected by the burning of sugarcane plantations, the main differences with respect to PAH pollution during harvesting and non-harvesting seasons can be observed in differences of the PAH profiles, primarily the levels of Phe, Flu and Pyr (de Andrade et al., 2010; Magalhães et al., 2007). These are the major PAHs emitted from the burning of Gramineae species, to which sugarcane belongs (Oros et al., 2006). Our levels of Phe, Flu and Pyr also point to sugarcane burning. The highest concentration of these Gramineae burning tracers were found during the harvesting season. Flu was detected in most of harvesting samples and only detected in four samples during the non-harvesting season. Heavy PAHs, such as D(ah)A, B(ghi)P and IP, were found in most samples from the harvesting season and were not detected in the non-harvesting season. Diesel exhaust is known to contain more particulate matter than gasoline exhaust, and heavy PAHs are associated with these particles (Ravindra et al., 2008). During sugarcane harvesting season, diesel-fueled trucks are used intensively to transport sugarcane from the fields to processing plants. Thus, diesel exhaust could be a potential heavy PAH source during harvesting season, as previously suggested by other authors (Umbuzeiro et al., 2008). Despite the similarity between this study and the results of de Andrade et al. (2010) that identified sugarcane burning as the primary PAH source for the indoor harvesting season samples, there are differences in the data for non-harvesting samples that indicate different PAH sources in this period. Fig. 3(b) shows a comparison between both studies with respect to the PAH relative contribution for non-harvesting samples. Our results showed that Phe and Pyr were the most abundant PAHs, while de Andrade et al. (2010) identified Phe, Flu, B(ghi)P and IP, which were attributed to vehicular emissions. One PAH source in indoor air is cooking. At Chinese non-smoker residences, 3e4 ring PAHs primarily derived from cooking (Zhu and Wang, 2003). However, samples were collected during non-cooking times (from 0:00 to 8:00). The discussion indicating cooking as a PAH source is complicated by the differences in various countries’

cooking practices and ingredients types. Phe and Pyr sources also include vehicular emission, oil combustion and biomass burning (Ravindra et al., 2008). Another possible PAH source in the present study is background contamination due to PAH accumulation in living room furniture. Polyurethane foam (PUF) is a well known sorbent for PAHs and is used in passive air sampling devices (Harner et al., 2006; Motelay-Massei et al., 2005). During the summer in this Brazilian region, the high temperatures (approximately 30e35  C) can promote PAH desorption and reemissions from furniture PUF. Indeed, Phe and Pyr, the most abundant PAHs in the non-harvesting samples, have gas-phase enrichment of 82% and 35%, respectively (Ré-Poppi and Santiago-Silva, 2005). 3.3. Risk assessment For benzo[a]pyrene, classified as a human carcinogen (IARC, 2010), the average concentrations were 0.3 ng m
3 and 0.06 ng m
3 for the August and January samples, respectively. In Brazil there are no fixed limits for PAH atmospheric concentrations (indoor or outdoor). During the harvesting season, the B(a)P average concentration exceeded the guide value (annual average) of some European countries, including France (0.1 ng m
3) and the United Kingdom (0.25 ng m
3) (Ravindra et al., 2008). Besides B(a)P, other compounds measured in indoor air samples were classified concerning human carcinogenicity by the International Agency for Research on Cancer, e.g., D(ah)A (2A group), B(a)A, B(b)F, B(k)F, Cry, and IP (2B group) (IARC, 2010). Because humans are exposed to complex PAH mixtures, the benzo[a]pyrene equivalent (BaPeq) is used to calculate the risk of cancer from PAH exposure (Castro et al., 2011; Delgado-Saborit et al., 2011; Silva et al., 2010). The BaPeq is calculated using the Toxic Equivalency Factor (TEF), which measures the relative toxicity of a specific PAH to B(a)P (Nisbet and LaGoy, 1992). The BaPeq is obtained by summing the products of each PAH concentration and its respective TEF. In this study, BaPeq was calculated for samples from harvesting and nonharvesting seasons using the TEF values proposed by Nisbet and LaGoy (1992). This work used a TEF equal to 1 instead of 5 for D(ah)A, as proposed by Malcolm and Dobson (2004). During the harvesting season, the average BaPeq was 1.7 ng m
3 and ranged from 0.1 to 4.3 ng m
3. The average BaPeq for the non-harvesting season was 0.07 ng m
3 and ranged from 0.001 to 0.3 ng m
3. The harvesting BaPeq level was higher than that established by the European Commission for B(a)P, 1 ng m
3 (annual average) (EU, 2004). We calculated BaPeq from the PAH average reported values in Brazilian studies. Our data from the harvesting season were comparable to, or even larger than, values observed in the outdoor air of large Brazilian cities, such as São Paulo, BaPeq e 0.72 ng m
3 (Vasconcellos et al., 2003) and Rio de Janeiro, BaPeq e 0.51 ng m
3 (Quiterio et al., 2007). Our BaPeq data from the harvesting season were also higher than New York City residences with heating systems (Jung et al., 2010), with a BaPeq of 0.460  0.365 ng m
3, and city air, with a BaPeq of 0.558  0.407 ng m
3. Additionally, this study reports higher BaPeq levels than the reported ones by Martellini et al. (2012) for a high traffic area in Florence (Italy), with BaPeq of 0.79 ng m
3 (city center). In accordance with our study, Silva et al. (2010) studied PM from Araraquara in 2009 and calculated BaPeq values for the harvesting season to be 1.3 ng m
3 and 1.2 ng m
3 for PM2.5 and PM10, respectively. These results suggest that PAHs from sugarcane burning can potentially represent a driver of the observed increase in cancer incidence in this area. 4. Conclusion This study presents data for PAH residential air pollution in Brazil. We observed higher PAH levels in indoor air samples collected

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during the sugarcane harvesting season. The present results indicate that the sugarcane biomass burning process is a factor that influences the indoor air quality in this residence and probably in other indoor environments in the proximities of sugarcane plantations. The increase in the calculated cancer risk (BaPeq based) during the sugarcane harvesting season, beyond the limit recommended by international agencies (>1 ng m
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