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Ambient protein concentration in PM10 in Hefei, central China
Atmospheric Environment 54 (2012) 73e79
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Ambient protein concentration in PM10 in Hefei, central China Hui Kang, Zhouqing Xie*, Qihou Hu Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 26 October 2011 Received in revised form 26 February 2012 Accepted 2 March 2012
The total protein associated with bioaerosol particulate matter (PM) is generally measured as an allinclusive indicator of airborne biological material, which may enhance the effects of allergens, allergic and asthmatic responses. To investigate the level and seasonal variations of biological loading, PM10 were collected in a metropolitan area of Hefei, central China from June 2008 to February 2009 and analyzed for total protein mass, trace elements, and water-soluble ions. The protein concentration in PM10 ranged from 2.08 to 36.71 mg m3 with an average of 11.42 mg m3. This was the highest value reported so far in the literature. The total protein was found to have a significant correlation with the air pollution index (API) and mean visibility (VV), indicating the potential influence of anthropogenic sources and/or crustal sources. The protein content displayed an obvious seasonal variation with respect to weather conditions. In the rainy season the level of protein was low, while in the dry season and foggy weather the level of protein was relatively high. A correlation analysis revealed that the relationship between total protein concentration and water-soluble ions Kþ and NO 3 in PM10 during the dry season is 0.92 and 0.66 (P < 0.05), respectively, suggesting that anthropogenic pollution and biomass burning are main contributors during this period. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Protein PM10 Bioaerosol China
1. Introduction Biological aerosols are ubiquitous in the Earth’s atmosphere. They affect atmospheric chemistry and physics, the biosphere, climate, and human health. Exposure to ambient particulate matter (PM) has been associated with severe adverse health effects (Dockery and Pope, 1994), including immunological reactions and allergic disease (mediated by IgE antibodies) (Flynn et al., 1979; Miguel et al., 1999; Schneider et al., 1997; Ahlholm et al., 1998; Bossche et al., 1988), from contact urticaria, rhinitis, hypersensitivity pneumonitis, and asthma to anaphylaxis and death. Approximately 40% of the population exposed to environmental allergens has developed IgE antibodies. About 20% of the general public demonstrates upper respiratory symptoms typical of rhinitis, and 10% shows lower respiratory symptoms characteristic of asthma (Pope et al., 1993). Respiratory effects like these are an allergic response to inhaled airborne particles that contain specific proteins. Most airborne proteins are derived from natural sources such as plant pollens and microbial metabolites (mold and bacteria) (Menetrez et al., 2000). Other allergens are released from anthropogenic air pollution sources that use or process contemporary
* Corresponding author. Tel.: þ86 551 3601415. E-mail address: [email protected] (Z. Xie). 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2012.03.003
organic materials (Miguel et al., 1996). They may induce irritational, allergic, infectious, and chemical responses in exposed individuals. Commonly, ambient biological PM has been characterized by the measurement of total protein content in PM10 (<10 mm in aerodynamic diameter) and PM2.5 (<2.5 mm in aerodynamic diameter). Studies indicated that the coarse and fine PM in both indoor and outdoor samples was of a biological origin (Heederick, 2003; Menetrez et al., 2001). These studies have demonstrated that 5e12% of the atmospheric total suspended PM samples were composed of biological protein allergens. These fragments remain toxic or allergenic depending upon the specific organism or organism component and can cause allergic, asthma-like reactions or pulmonary disease. Protein has been found in both coarse and fine PM fractions (Pope, 1999). However, studies have demonstrated that the coarse PM fraction contain a higher protein content and have been associated with significant adverse effects (Monn and Becker, 1999; Soukup and Becker, 2001). A significant positive correlation was found between protein and the coarse PM fraction in Phoenix, AZ (Boreson et al., 2004). Mueller-Anneling et al. (2004) found that the levels of PM10 and endotoxin concentrations were significantly correlated in Southern California. Total protein concentration is often used as an all-inclusive indicator of biologically-based aerosols in fine and coarse PM samples collected for aerobiological studies (Schappi et al., 1996; Miguel et al., 1999; Womiloju et al., 2003). Previous reports found
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that paved road dust consisted of a significant portion of organic protein material and was a major component of PM in some areas because paved road dust can be re-suspended by moving vehicles (Watson et al., 1994). Potential allergens within paved road dust came from at least 20 different sources, including pollen, animal dander and mold (Miguel et al., 1999). Chemical constituents of PM can enhance allergic and asthmatic reactions caused by bioaerosols. Trace amounts of transition metals such as vanadium, chromium, iron, nickel, copper, zinc, and lead in PM (from fossil fuel combustion, incineration, high-temperature metal processing and to a lesser extent from soil dust) may exacerbate biological allergenic responses (Gavett and Koren, 2001; Frampton et al., 1999). These factors emphasize the importance of investigating the biological loading of ambient PM. In Hefei, a city with approximately 5 million inhabitants, the urbanization and industrial processes have led to increased levels of air, water, and soil pollution, and modifications of weather conditions. This study examined atmospheric particulate matter as sources of allergen exposure and characterized the level and seasonal variations of protein concentrations extracted from air filters as a possible indicator of airborne biological material (viable and nonviable). With few reports on biological aerosols in the ambient air in Chinese cities, this study provides a case to understand the characteristics and potential health risks of such biological aerosols. 2. Materials and methods 2.1. Sampling location The aerosol samples were collected in Hefei, China (31500 N, 117160 E, Fig. 1). Hefei is the capital and commercial center of Anhui Province in central China, with an area of 7048 km2 and a population of over five million. Hefei is a developing city located in the Yangtze River Delta economic development zone. The city has rapidly become industrialized due to the relocation of many factories (e.g., electronic factory) from the Pearl River Delta (the so called “world factory”) to central China. The rapid urbanization and industrialization have led to large amounts of untreated or inadequately treated wastewater, poor drainage of inland rivers, and serious air pollution. 2.2. Sample collection Coarse ambient particle (PM10) samples were collected using a high-volume bulk aerosol sampler (TH-1000C2, Tianhong Instruments, Wuhan, China) at a flow rate of 1.05 m3 min1. Glass
microfiber filters (GFs) (Whatman EPM2000, 20 cm 25 cm) were used to collect bulk aerosols. GFs were baked at 300 C for 24 h to remove organic contaminants before sampling. The sampler was installed on the roof platform (15 m above the surrounding ground level) of the First Teaching Building in the University of Science and Technology of China, in Hefei, China (31500 N, 117160 E, Fig. 1). After sampling according to the contamination controlling procedure (Gao et al., 1996), the filters were placed in pre-cleaned aluminum foil (baked at 500 C for 5 h) and stored in a freezer at 20 C before analysis. The time for each sample collection lasted 48 h and the total volume was approximately 2800 m3. The sampling period was from June 2008 to February 2009. 2.3. Samples analysis 2.3.1. Protein analysis Sample filters were cut off using sterilized stainless steel scissors. The filter was extracted with a mixture of 0.6 mL of phosphate buffered saline (PBS) (Franze et al., 2003) and 5.4 mL ultrapure water (Milli-Q water, 18.2 MU), and stirred for 90 min. The filterbuffer slurry was then centrifuged at 5000 rpm for 20 min and subsequently filtered through a 0.45 mm syringe filter (cellulose acetate membrane with glass fiber pre-filter, Sartorius). The residue was twice washed with 1 mL ultrapure water, and the washing solutions were filtered and added to the first filtrate. The combined filtrates were dried under a nitrogen stream and redissolved in water (2 mL) for the determination of total proteins. Total protein was analyzed according to the method of Franze et al. (2005). The samples were determined with a bicinchoninic acid assay (Micro BCA Protein Assay Kit, Thermo), which is a detergent-compatible bicinchoninic acid formulation for the colorimetric detection and quantitation of the total protein. Most of the molecules known to interfere with the BCA protein assay are negligible (Stoscheck, 1990). The Micro BCA assay utilizes bicinchoninic acid (BCA) as the detection reagent for Cuþ, which is formed when Cu2þ is reduced by protein in an alkaline environment. A purple-colored reaction product is formed by the chelation of two molecules of BCA with one cuprous ion (Cuþ). This water-soluble complex exhibits a strong absorbance. The assay was performed in microwell plates (96 wells) and calibrated with aqueous solutions of bovine serum albumin (BSA) in the concentration range of 0.5e40 mg L1 (detection limit w2 mg L1). A total of 150 mL of the standard and sample solutions, respectively, was pipetted into the microwells (three wells per sample solution), and the freshly prepared working reagent was added (150 mL per well). The microwell plate was incubated at 37 C for 2 h, and then cooled to room temperature. The
Fig. 1. Location of the sampling site.
H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
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total protein. The content of total protein in Hefei varied considerably, ranging from 2.08 to 36.71 mg m3 with an average value of 11.42 mg m3. As shown in Fig. 2, the protein concentration peaked at 36.71 mg m3 from November 13, 2008 to November 15, 2008, and reached the minimum level of 2.08 mg m3 from July 29, 2008 to July 31, 2008. As an all-inclusive indicator of biological aerosol, the level of total protein was previously reported in some regions. Table 1 summarized the total protein concentrations by volume of air sampled in different areas. In urban central North Carolina, the total protein for PM10 ranged from 0 to 0.2 mg m3 with an average of 0.125 mg m3 (Menetrez et al., 2007). In southern California, total protein contribution to monthly average airborne TSP and PM10 concentrations was found to be in the range of 1.0e5.8 mg m3 (Miguel et al., 1999). Rosas et al. (1995) examined the protein content of coarse fraction samples in Mexico City and found that the concentrations ranged from non-detectable to 2.54 mg m3. Total protein in aerosols in the south of western Siberia was reported in the range of 0e3.5 mg m3 (Belan et al., 2000). In comparison with these previous reports, the value in Hefei was obviously an order of magnitude higher, indicating a high mass of bioaerosol occurring in the ambient air over the city.
absorbance was measured on a microplate reader (Universal Microplate Reader, ELX 800) at 550 nm. The protein concentrations were calculated from the standard curve. Blank filters were assayed according to the same procedure. The results were corrected by subtracting the mean value of the blank filters. 2.3.2. Elemental analysis PM10 samples were acid digested using airtight microwave digestion (CEM MARS) according to the EPA-3051 Test Method (2003). A portion of each filter was cut and placed inside a pressure controlled sample bottle. A proper amount of aqua regia solution was then added (6 mL HNO3 þ 3 mL HCl) to each sample, and the sample was digested and then analyzed for the elements using Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES). All ICP-OES data shown in this paper were blank subtracted. 2.3.3. Ion chromatography analyses (IC) A portion of each sample, approximately 4 4 cm2, was extracted with 20 mL ultrapure (18 MU) deionized water by ultrasonic waves for half an hour. The solutions were filtered with a 0.45 mm pore-size membrane filter. The water-soluble ion was then measured using ion chromatography (Dionex, ICS-3000, CA). The procedures were strictly quality-controlled to avoid any possible contamination of the samples. The results were corrected with the filter blank.
3.2. Potential sources The total protein may be a combination of pollen, mold, bacteria, insect debris, fecal matter, dander, and so on. The protein concentration of air has many influencing factors such as phenology, meteorological conditions, sunshine, rainfall, and wind direction in connection with sampling locality and distance from their sources of abiotic and biotic emission. As shown in Fig. 3a, the temporal change in the protein mass of PM10 is similar to the temporal change of API and VV during the sampling period. Both visibility and API can characterize the air quality level. Higher absolute values of API or lower values of VV mean relatively serious air pollution. As shown in Fig. 3b, there was a significant positive correlation between protein and API (R ¼ 0.80, P < 0.05), and a significant negative correlation between protein and VV (R ¼ 0.42, P < 0.05). Although protein concentrations in the atmosphere may be influenced by many factors, the relationship revealed that ambient proteins in Hefei could be mainly ascribed to the contribution of anthropogenic sources (e.g., traffic and industry) and/or crustal sources (disturbed desert due to construction and agricultural dust). One of the important anthropogenic sources is road dust, which can be re-suspended into the atmosphere by passing vehicle traffic (Miguel et al., 1999) and has been documented as an important source of airborne proteins (Taylor et al., 1977; Schumacher, 1980). Hefei is a quickly developing
2.3.4. Meteorological parameters The data of precipitation amount (PP), mean visibility (VV) and weather conditions in Hefei were obtained from the website (http:// www.tutiempo.net/en/Climate/). In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. The data of air pollution index (API) in Hefei was obtained from the website of China National Environmental Monitoring Center Station (http://www.cnemc.cn/citystatus/airDailyReport. jsp). The API is a simple and generalized way to describe the air quality in mainland China. The API level is based on the level of 5 atmospheric pollutants including sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particulates (PM10), carbon monoxide (CO) and ozone (O3). The results of meteorological data in this study were the average values in corresponding to each sampling period. 3. Results and discussion 3.1. The total content of protein in PM10 Coarse particulate matters (PM10) were collected from June 2008 to February 2009. A total of 30 samples were analyzed for the 40
30 25 20 15 10
Date Fig. 2. Protein concentrations (mg m3) of PM10.
09.02.20
09.02.07
09.01.30
09.01.19
09.01.12
08.11.28
08.11.24
08.11.17
08.11.13
08.10.31
08.11.10
08.10.21
08.10.17
08.10.06
08.10.03
08.09.29
08.09.19
08.09.26
08.09.12
08.09.05
08.08.31
08.08.15
08.08.09
08.08.04
08.07.29
08.07.26
08.07.18
08.07.07
0
08.06.18
5 08.06.23
Protein of PM10 (µg m-3)
35
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Table 1 Summary of total protein concentrations (mg m3) in different areas. PM Period of species sampling
Site
TSP
Oct. 95 to May 96
PM10
Oct. 95 to May 96 Aug. 2003 to Jan. 2004 Dec. 1998 to Jan. 2000 1 day a week, 1991 Jun. 2008 to Feb. 2009
Los Angeles Long Beach Rubidoux Rubidoux
PM10
PM10 PM10
North Carolina
Mean
Reference
1.5e5.8 0.6e5.8 1.7e4.3 2.1e3.9
Miguel et al., 1999
0.125 0e0.2
South of western Siberia Mexico City Hefei, China
Range
11.42
0e3.5
Menetrez et al., 2007 Belan et al., 2000
0e2.54
Rosas et al., 1995
2.08e36.71 This study
city with machinery, electronic, chemistry, steel, textile, cigarette manufacturing factories and other industries. The process of industrialization and urbanization of the city has led to the reduction of green areas, biodiversity loss, heavy traffic, and soil pollution by human and animal excreta. The sampling site located in the center of Hefei (Fig. 1) is a traffic-intensive area undergoing periodic construction. For example, during the sampling period, Jinzhai Road viaduct was being built 50 m away from the sampling site. This construction could have generated a great amount of dust, which can cause biological materials to be aerosolized by vehicle traffic over the road, and thereby enhance atmospheric bioaerosol concentrations. On the other hand, agricultural dust sources may also have contributed to the high protein concentration in aerosol samples. Hefei is the capital and largest city of Anhui Province, which is a major agricultural province of China. In suburbs, there are a large number of agricultural production activities (e.g., cultivation of rice, vegetables, and other crops). These activities produce large amounts of pollen grains and mold spores that may enhance the level of biological aerosols. Both anthropogenic and agricultural
Fig. 3. (a) Protein (mg m3) of PM10, air pollution index (API) and mean visibility (VV, km) during the sampling period; (b) Relationships between protein (mg m3) of PM10 and air pollution index (API) and mean visibility (VV).
H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
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20
Protein Fog 15
10
5
0 Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Jan.
Feb.
Fig. 4. Monthly change in total protein concentrations (mg m3) of PM10 and the number of foggy days.
sources observed in this study are in agreement with previous reports. For example, in large metropolitan areas, previous longterm studies indicated that elevated, localized concentrations of PM10 around the urban area were often due to nearby soildisturbing activities (Chow et al., 1999). Boreson et al. (2004) estimated that more than 70% of coarse particles were generated from road dust, agriculture, and construction activities in Phoenix, and coarse PM were higher at the urban fringe compared to the natural desert. Road dust present on the streets of southern California was shown to contain a significant portion of organic protein material (Miguel et al., 1999). More discussion on the sources is presented below. 3.3. Seasonal variation The average monthly total protein concentration of PM10 is shown in Fig. 4. From Jun. to Nov. 2008, the protein concentration increased gradually, peaking at 36.71 mg m3 in Nov. 2008. Figs. 2 and 4 clearly showed that total protein concentrations were higher in winter than in summer. The seasonal variations appeared to be related to changes in precipitation. As shown in Fig. 5, the protein concentration of PM10 and precipitation amount were inversely related during the sampling period, i.e., a high level of protein was
observed in the dry season, while a low level of protein occurred in the wet season. Similar observations have been reported in Mexico City where protein concentrations of aerosols in the dry season were higher than those in the wet season (Rosas et al., 1995). Likewise, both PM10 and endotoxin levels were lower on days with precipitation in Southern California (Mueller-Anneling et al., 2004). This phenomenon has been ascribed to the rainfall that swept particles to the ground in the rainy season and the low moisture of soils that enhanced aerosolization of particles in the dry season. Moreover, autumn and winter are the foggy seasons in Hefei. Fig. 4 showed that the number of foggy days was much higher during autumn and winter than during other seasons, e.g., there were 12 foggy days in November 2008 alone. Sampling dates of October 17e19, November 13e15, 23e24, and 29 of 2008, and January 19e21 of 2009 were all foggy days, during which the pollutants can combine with water vapor in air to make more PM materials. The concentrations of protein and API were higher during these periods, and the monthly protein level in November was the highest. In addition to weather conditions, the sources of ambient proteins could also explain seasonal fluctuations. To determine the sources, PM10 samples with high protein levels collected during the dry season of Sep. 08 to Jan. 09 (samples not associated with precipitation or fog) were also analyzed for elemental composition and water-
60
PP(mm)
50 40 30 20 10 0
Protein (µg m-3)
40 30 20 10 0 6/1
6/21
7/11
7/31
8/20
9/9
9/29
10/19
11/8
11/28 12/18
1/7
1/27
2/16
3/8
Date Fig. 5. Protein (mg m3) of PM10 and precipitation amount (PP, mm) during the sampling period (shaded areas show the rainy and dry season, respectively).
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H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
Table 2 Correlations between protein and trace element and water-soluble ions of PM10 from Hefei during Sep. 2008eJan. 2009. The bold values shows the significant correlation between total protein concentration and water-soluble ions Kþ and NO 3 in PM10, respectively.
Fe Ni Cu Zn Ba Pb V Mn Sr Kþ NO 3 SO2 4 MSA Protein
Fe
Ni
Cu
Zn
Ba
Pb
V
Mn
Sr
Kþ
NO 3
SO2 4
MSA
Protein
1 0.674 0.772 0.839 0.385 0.730 0.359 0.960 0.611 0.096 0.271 0.369 0.311 0.147
1 0.130 0.513 0.179 0.447 0.123 0.521 0.138 0.167 0.389 0.635 0.805 0.034
1 0.652 0.482 0.519 0.347 0.876 0.775 0.272 0.361 0.190 0.074 0.061
1 0.133 0.851 0.480 0.759 0.237 0.277 0.105 0.502 0.270 0.295
1 0.147 0.218 0.556 0.818 0.567 0.404 0.424 0.013 0.395
1 0.002 0.603 0.098 0.384 0.156 0.450 0.104 0.297
1 0.374 0.161 0.179 0.255 0.354 0.216 0.397
1 0.785 0.133 0.351 0.149 0.194 0.005
1 0.510 0.363 0.399 0.138 0.279
1 0.656 0.686 0.065 0.922
1 0.136 0.682 0.661
1 0.554 0.526
1 0.284
1
soluble ions. Correlation analysis (Table 2) indicated that the correlation coefficient between the total protein and water-soluble Kþ and NO 3 were 0.92 and 0.66 (P < 0.05), respectively, implying these substances had similar sources. Water-soluble potassium ion in PM samples, a tracer of biomass burning (Arimoto et al.,1995), was found to correlate with protein with a high coefficient of 0.92. In Hefei region, the period from September to November is the rice harvest season and as such there is heavy straw burning. The high correlation between protein and Kþ indicated a substantial contribution by biomass burning in the dry season. Rogge et al. (1991) reported that biomass burning could produce biomolecules such as cholesterol. It was reasonable to presume that proteins may be released as well. It was well known that NO 3 could come from emissions from both gasoline and diesel combustion, and power plant exhaust (Pacyna, 1998). The relationship with protein concentration thus indicates that anthropogenic sources are important contributors to high protein masses in aerosols. 3.4. Implication for health effects due to high protein masses in PM10 Protein concentrations were much higher in Hefei than those reported in other regions, illustrating a high biological loading over the city. It was documented that inhaled components of protein PM could stimulate alveolar macrophages and respiratory epithelial tissue to release cytokines or chemattractants that initiate an inflammatory cascade (Thorne, 2000). This is significant to asthmatics and those with impaired pulmonary function. In comparison with other cities in China, Hefei is considered small to medium-sized. There are many large or mega cities in the regions of Pearl River Delta, Yangtze River Delta, and Bohai of China. In these regions, there are intensive industries and human activities and serious environmental pollution. However, ambient biological aerosols are rarely reported. It can be speculated, nevertheless, that high protein levels exist in aerosols of these regions. Since the majority of China’s population is concentrated in regions with serious air pollution, more attention should be paid to the health risks caused by exposure to biological materials in aerosols. Additional studies are urgently needed to investigate the occurrence, distribution, source, and health effects of ambient proteins in China. 4. Conclusions The level and seasonal variations of total protein in ambient air in Hefei were investigated for the period of June 2008 to February 2009. The protein concentration in PM10 ranged from 2.08 to 36.71 mg m3 with an average of 11.42 mg m3. In comparison with
literature reports elsewhere, this value was an order of magnitude higher, indicating a high loading of biological aerosols in the air. The significant correlation between total protein and API and VV suggested the potential influence of anthropogenic sources and/or crustal sources. The protein content displayed seasonal variations with a low level in the rainy season and a high level in the dry season and foggy weather. The sources were ascribed to anthropogenic pollution and biomass burning during the dry season as suggested by a significant correlation between total protein concentration and water-soluble ions Kþ and NO 3 in PM10. Acknowledgments This research was supported by grants from the National Natural Science Foundation of China (Project Nos. 41025020, 41176170), the Chinese Academy of Sciences (Grant KZCX2-YW-QN506) and the Fundamental Research Funds for the Central Universities. References Ahlholm, J.U., Helander, M.L., Savolainen, J., 1998. Genetic and environmental factors affecting the allergenicity of birch (Betula pubescens ssp. czerepanovii [Orl.] Hamet-Ahti) pollen. Clinical & Experimental Allergy 28, 1384e1388. Arimoto, R., Duce, R.A., Ray, B.J., Ellis Jr., W.G., Cullen, J.D., Merrill, J.T., 1995. Trace elements in the atmosphere over the North Atlantic. Journal of Geophysical Research 100, 1119e1213. Belan, B.D., Borodulin, A.I., Buryak, G.A., Marchenko, Y.V., Olkin, S.E., Panchenko, M.V., Pyankov, O.V., Safatov, A.S., 2000. Annual changes in concentration in protein content of atmospheric aerosol in the south of western Siberia. Journal of Aerosol Science 31, 963e964. Boreson, J., Dillner, A.M., Peccia, J., 2004. Correlating bioaerosol load with PM2.5 and PM10 concentrations: a comparison between natural desert and urban-fringe aerosols. Atmospheric Environment 38, 6029e6041. Bossche, H.V., Mackenzie, D.W.R., Cauwenbergh, G., 1988. Aspergillus and Aspergillosis. Plenum Press, New York, pp. 87e105. Chow, J.C., Watson, J.G., Green, M.C., Lowenthal, D.H., DuBois, D.W., Kohl, S.D., Egami, R.T., Gillies, J., Rogers, C.F., Frazier, C.A., Cates, W., 1999. Middle and neighborhood-scale variations of PM10 source contributions in Las Vegas, Nevada. Journal of the Air & Waste Management Association 49, 641e654. Dockery, D.W., Pope, C.A., 1994. Acute respiratory effects of particulate air pollution. Annual Review of Public Health 15, 107e132. Flynn, N.M., Hoeprich, P.D., Kawachi, M.M., Lawrence, R.M., Goldstein, E., Jordan, G.W., Kundargi, R.S., Wong, G.A., 1979. An unusual outbreak of windborne coccidioidomycosis. New England Journal of Medicine 301, 358e361. Frampton, M.W., Ghio, A.J., Samet, J.M., Carson, J.L., Carter, J.D., Devlin, R.B., 1999. Effects of aqueous extracts of PM10 filters from the Utah Valley on human airway epithelial cells. American Journal of Physiology Lung Cellular and Molecular Physiology 277, L960eL967. Franze, T., Weller, M.G., Niessner, R., Pöschl, U., 2003. Enzyme immunoassays for the investigation of protein nitration by air pollutants. Analyst 128, 824e831. Franze, T., Weller, M.G., Niessner, R., Pöschl, U., 2005. Protein nitration by polluted air. Environmental Science & Technology 39, 1673e1678. Gao, Y., Arimoto, R., Duce, R.A., Chen, L.Q., Zhou, M.Y., Gu, D.Y., 1996. Atmospheric non-sea-salt sulfate, nitrate and methanesulfonate over the China Sea. Journal of Geophysical Research 101, 12601e12611.
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Rogge, W.F., Hildemann, L.M., Mazurek, M.A., Cass, G.R., Simoneit, B.R.T., 1991. Sources of fine organic aerosol. 1. Charbroilers and meat cooking operations. Environmental Science & Technology 25, 1112e1125. Rosas, I., Yela, A., Salinas, E., Arreguin, R., Rodriguez-Romero, A., 1995. Preliminary assessment of protein associated with airborne particles in Mexico City. Aerobiologia 11, 81e86. Schappi, G.F., Monn, C., Wuthrich, B., Wanner, H.U., 1996. Direct determination of allergens in ambient aerosols: methodological aspects. International Archives of Allergy and Immunology 110, 364e370. Schneider, E., Hajjeh, R.A., Spiegel, R.A., Jibson, R.W., Harp, E.L., Marshall, G.A., Gunn, R.A., McNeil, M.M., Pinner, R.W., Baron, R.C., Burger, R.C., Hutwagner, L.C., Crump, C., Kaufman, L., Reef, S.E., Feldman, G.M., Pappagianis, D., Werner, S.B., 1997. A coccidioidomycosis outbreak following the Northridge, Calif, Earthquake. Journal American Medical Association 277, 904e908. Schumacher, M.J., 1980. Characterization of allergens from urine and pelts of laboratory mice. Molecular Immunology 17, 1087e1095. Soukup, J.M., Becker, S., 2001. Human alveolar macrophage responses to air pollution particulates are associated with insoluble components of coarse material, including particulate endotoxin. Toxicology and Applied Pharmacology 171, 20e26. Stoscheck, C.M., 1990. In: Deutscher, M.P. (Ed.), Methods in Enzymology. Academic Press, New York, pp. 50e68. Taylor, A.N., Longbottom, J., Pepys, J., 1977. Respiratory allergy to urine proteins of rats and mice. Lancet 310, 847e849. Thorne, P.S., 2000. Inhalation toxicology models of endotoxin and bioaerosol induced inflammation. Toxicology 152, 13e23. Watson, J.G., Chow, J.C., Lu, Z., Fujita, E.M., Lowenthal, D.H., Lawson, D.R., Ashbaugh, L.L., 1994. Chemical mass balance source apportionment of PM10 during the southern California air quality study. Aerosol Science and Technology 21, 1e36. Womiloju, T.O., Miller, J.D., Mayer, P.M., Brook, J.R., 2003. Methods to determine the biological composition of particulate matter collected from outdoor air. Atmospheric Environment 37, 4335e4344.
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Ambient protein concentration in PM10 in Hefei, central China Hui Kang, Zhouqing Xie*, Qihou Hu Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 26 October 2011 Received in revised form 26 February 2012 Accepted 2 March 2012
The total protein associated with bioaerosol particulate matter (PM) is generally measured as an allinclusive indicator of airborne biological material, which may enhance the effects of allergens, allergic and asthmatic responses. To investigate the level and seasonal variations of biological loading, PM10 were collected in a metropolitan area of Hefei, central China from June 2008 to February 2009 and analyzed for total protein mass, trace elements, and water-soluble ions. The protein concentration in PM10 ranged from 2.08 to 36.71 mg m3 with an average of 11.42 mg m3. This was the highest value reported so far in the literature. The total protein was found to have a significant correlation with the air pollution index (API) and mean visibility (VV), indicating the potential influence of anthropogenic sources and/or crustal sources. The protein content displayed an obvious seasonal variation with respect to weather conditions. In the rainy season the level of protein was low, while in the dry season and foggy weather the level of protein was relatively high. A correlation analysis revealed that the relationship between total protein concentration and water-soluble ions Kþ and NO 3 in PM10 during the dry season is 0.92 and 0.66 (P < 0.05), respectively, suggesting that anthropogenic pollution and biomass burning are main contributors during this period. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Protein PM10 Bioaerosol China
1. Introduction Biological aerosols are ubiquitous in the Earth’s atmosphere. They affect atmospheric chemistry and physics, the biosphere, climate, and human health. Exposure to ambient particulate matter (PM) has been associated with severe adverse health effects (Dockery and Pope, 1994), including immunological reactions and allergic disease (mediated by IgE antibodies) (Flynn et al., 1979; Miguel et al., 1999; Schneider et al., 1997; Ahlholm et al., 1998; Bossche et al., 1988), from contact urticaria, rhinitis, hypersensitivity pneumonitis, and asthma to anaphylaxis and death. Approximately 40% of the population exposed to environmental allergens has developed IgE antibodies. About 20% of the general public demonstrates upper respiratory symptoms typical of rhinitis, and 10% shows lower respiratory symptoms characteristic of asthma (Pope et al., 1993). Respiratory effects like these are an allergic response to inhaled airborne particles that contain specific proteins. Most airborne proteins are derived from natural sources such as plant pollens and microbial metabolites (mold and bacteria) (Menetrez et al., 2000). Other allergens are released from anthropogenic air pollution sources that use or process contemporary
* Corresponding author. Tel.: þ86 551 3601415. E-mail address: [email protected] (Z. Xie). 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2012.03.003
organic materials (Miguel et al., 1996). They may induce irritational, allergic, infectious, and chemical responses in exposed individuals. Commonly, ambient biological PM has been characterized by the measurement of total protein content in PM10 (<10 mm in aerodynamic diameter) and PM2.5 (<2.5 mm in aerodynamic diameter). Studies indicated that the coarse and fine PM in both indoor and outdoor samples was of a biological origin (Heederick, 2003; Menetrez et al., 2001). These studies have demonstrated that 5e12% of the atmospheric total suspended PM samples were composed of biological protein allergens. These fragments remain toxic or allergenic depending upon the specific organism or organism component and can cause allergic, asthma-like reactions or pulmonary disease. Protein has been found in both coarse and fine PM fractions (Pope, 1999). However, studies have demonstrated that the coarse PM fraction contain a higher protein content and have been associated with significant adverse effects (Monn and Becker, 1999; Soukup and Becker, 2001). A significant positive correlation was found between protein and the coarse PM fraction in Phoenix, AZ (Boreson et al., 2004). Mueller-Anneling et al. (2004) found that the levels of PM10 and endotoxin concentrations were significantly correlated in Southern California. Total protein concentration is often used as an all-inclusive indicator of biologically-based aerosols in fine and coarse PM samples collected for aerobiological studies (Schappi et al., 1996; Miguel et al., 1999; Womiloju et al., 2003). Previous reports found
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H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
that paved road dust consisted of a significant portion of organic protein material and was a major component of PM in some areas because paved road dust can be re-suspended by moving vehicles (Watson et al., 1994). Potential allergens within paved road dust came from at least 20 different sources, including pollen, animal dander and mold (Miguel et al., 1999). Chemical constituents of PM can enhance allergic and asthmatic reactions caused by bioaerosols. Trace amounts of transition metals such as vanadium, chromium, iron, nickel, copper, zinc, and lead in PM (from fossil fuel combustion, incineration, high-temperature metal processing and to a lesser extent from soil dust) may exacerbate biological allergenic responses (Gavett and Koren, 2001; Frampton et al., 1999). These factors emphasize the importance of investigating the biological loading of ambient PM. In Hefei, a city with approximately 5 million inhabitants, the urbanization and industrial processes have led to increased levels of air, water, and soil pollution, and modifications of weather conditions. This study examined atmospheric particulate matter as sources of allergen exposure and characterized the level and seasonal variations of protein concentrations extracted from air filters as a possible indicator of airborne biological material (viable and nonviable). With few reports on biological aerosols in the ambient air in Chinese cities, this study provides a case to understand the characteristics and potential health risks of such biological aerosols. 2. Materials and methods 2.1. Sampling location The aerosol samples were collected in Hefei, China (31500 N, 117160 E, Fig. 1). Hefei is the capital and commercial center of Anhui Province in central China, with an area of 7048 km2 and a population of over five million. Hefei is a developing city located in the Yangtze River Delta economic development zone. The city has rapidly become industrialized due to the relocation of many factories (e.g., electronic factory) from the Pearl River Delta (the so called “world factory”) to central China. The rapid urbanization and industrialization have led to large amounts of untreated or inadequately treated wastewater, poor drainage of inland rivers, and serious air pollution. 2.2. Sample collection Coarse ambient particle (PM10) samples were collected using a high-volume bulk aerosol sampler (TH-1000C2, Tianhong Instruments, Wuhan, China) at a flow rate of 1.05 m3 min1. Glass
microfiber filters (GFs) (Whatman EPM2000, 20 cm 25 cm) were used to collect bulk aerosols. GFs were baked at 300 C for 24 h to remove organic contaminants before sampling. The sampler was installed on the roof platform (15 m above the surrounding ground level) of the First Teaching Building in the University of Science and Technology of China, in Hefei, China (31500 N, 117160 E, Fig. 1). After sampling according to the contamination controlling procedure (Gao et al., 1996), the filters were placed in pre-cleaned aluminum foil (baked at 500 C for 5 h) and stored in a freezer at 20 C before analysis. The time for each sample collection lasted 48 h and the total volume was approximately 2800 m3. The sampling period was from June 2008 to February 2009. 2.3. Samples analysis 2.3.1. Protein analysis Sample filters were cut off using sterilized stainless steel scissors. The filter was extracted with a mixture of 0.6 mL of phosphate buffered saline (PBS) (Franze et al., 2003) and 5.4 mL ultrapure water (Milli-Q water, 18.2 MU), and stirred for 90 min. The filterbuffer slurry was then centrifuged at 5000 rpm for 20 min and subsequently filtered through a 0.45 mm syringe filter (cellulose acetate membrane with glass fiber pre-filter, Sartorius). The residue was twice washed with 1 mL ultrapure water, and the washing solutions were filtered and added to the first filtrate. The combined filtrates were dried under a nitrogen stream and redissolved in water (2 mL) for the determination of total proteins. Total protein was analyzed according to the method of Franze et al. (2005). The samples were determined with a bicinchoninic acid assay (Micro BCA Protein Assay Kit, Thermo), which is a detergent-compatible bicinchoninic acid formulation for the colorimetric detection and quantitation of the total protein. Most of the molecules known to interfere with the BCA protein assay are negligible (Stoscheck, 1990). The Micro BCA assay utilizes bicinchoninic acid (BCA) as the detection reagent for Cuþ, which is formed when Cu2þ is reduced by protein in an alkaline environment. A purple-colored reaction product is formed by the chelation of two molecules of BCA with one cuprous ion (Cuþ). This water-soluble complex exhibits a strong absorbance. The assay was performed in microwell plates (96 wells) and calibrated with aqueous solutions of bovine serum albumin (BSA) in the concentration range of 0.5e40 mg L1 (detection limit w2 mg L1). A total of 150 mL of the standard and sample solutions, respectively, was pipetted into the microwells (three wells per sample solution), and the freshly prepared working reagent was added (150 mL per well). The microwell plate was incubated at 37 C for 2 h, and then cooled to room temperature. The
Fig. 1. Location of the sampling site.
H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
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total protein. The content of total protein in Hefei varied considerably, ranging from 2.08 to 36.71 mg m3 with an average value of 11.42 mg m3. As shown in Fig. 2, the protein concentration peaked at 36.71 mg m3 from November 13, 2008 to November 15, 2008, and reached the minimum level of 2.08 mg m3 from July 29, 2008 to July 31, 2008. As an all-inclusive indicator of biological aerosol, the level of total protein was previously reported in some regions. Table 1 summarized the total protein concentrations by volume of air sampled in different areas. In urban central North Carolina, the total protein for PM10 ranged from 0 to 0.2 mg m3 with an average of 0.125 mg m3 (Menetrez et al., 2007). In southern California, total protein contribution to monthly average airborne TSP and PM10 concentrations was found to be in the range of 1.0e5.8 mg m3 (Miguel et al., 1999). Rosas et al. (1995) examined the protein content of coarse fraction samples in Mexico City and found that the concentrations ranged from non-detectable to 2.54 mg m3. Total protein in aerosols in the south of western Siberia was reported in the range of 0e3.5 mg m3 (Belan et al., 2000). In comparison with these previous reports, the value in Hefei was obviously an order of magnitude higher, indicating a high mass of bioaerosol occurring in the ambient air over the city.
absorbance was measured on a microplate reader (Universal Microplate Reader, ELX 800) at 550 nm. The protein concentrations were calculated from the standard curve. Blank filters were assayed according to the same procedure. The results were corrected by subtracting the mean value of the blank filters. 2.3.2. Elemental analysis PM10 samples were acid digested using airtight microwave digestion (CEM MARS) according to the EPA-3051 Test Method (2003). A portion of each filter was cut and placed inside a pressure controlled sample bottle. A proper amount of aqua regia solution was then added (6 mL HNO3 þ 3 mL HCl) to each sample, and the sample was digested and then analyzed for the elements using Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES). All ICP-OES data shown in this paper were blank subtracted. 2.3.3. Ion chromatography analyses (IC) A portion of each sample, approximately 4 4 cm2, was extracted with 20 mL ultrapure (18 MU) deionized water by ultrasonic waves for half an hour. The solutions were filtered with a 0.45 mm pore-size membrane filter. The water-soluble ion was then measured using ion chromatography (Dionex, ICS-3000, CA). The procedures were strictly quality-controlled to avoid any possible contamination of the samples. The results were corrected with the filter blank.
3.2. Potential sources The total protein may be a combination of pollen, mold, bacteria, insect debris, fecal matter, dander, and so on. The protein concentration of air has many influencing factors such as phenology, meteorological conditions, sunshine, rainfall, and wind direction in connection with sampling locality and distance from their sources of abiotic and biotic emission. As shown in Fig. 3a, the temporal change in the protein mass of PM10 is similar to the temporal change of API and VV during the sampling period. Both visibility and API can characterize the air quality level. Higher absolute values of API or lower values of VV mean relatively serious air pollution. As shown in Fig. 3b, there was a significant positive correlation between protein and API (R ¼ 0.80, P < 0.05), and a significant negative correlation between protein and VV (R ¼ 0.42, P < 0.05). Although protein concentrations in the atmosphere may be influenced by many factors, the relationship revealed that ambient proteins in Hefei could be mainly ascribed to the contribution of anthropogenic sources (e.g., traffic and industry) and/or crustal sources (disturbed desert due to construction and agricultural dust). One of the important anthropogenic sources is road dust, which can be re-suspended into the atmosphere by passing vehicle traffic (Miguel et al., 1999) and has been documented as an important source of airborne proteins (Taylor et al., 1977; Schumacher, 1980). Hefei is a quickly developing
2.3.4. Meteorological parameters The data of precipitation amount (PP), mean visibility (VV) and weather conditions in Hefei were obtained from the website (http:// www.tutiempo.net/en/Climate/). In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. The data of air pollution index (API) in Hefei was obtained from the website of China National Environmental Monitoring Center Station (http://www.cnemc.cn/citystatus/airDailyReport. jsp). The API is a simple and generalized way to describe the air quality in mainland China. The API level is based on the level of 5 atmospheric pollutants including sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particulates (PM10), carbon monoxide (CO) and ozone (O3). The results of meteorological data in this study were the average values in corresponding to each sampling period. 3. Results and discussion 3.1. The total content of protein in PM10 Coarse particulate matters (PM10) were collected from June 2008 to February 2009. A total of 30 samples were analyzed for the 40
30 25 20 15 10
Date Fig. 2. Protein concentrations (mg m3) of PM10.
09.02.20
09.02.07
09.01.30
09.01.19
09.01.12
08.11.28
08.11.24
08.11.17
08.11.13
08.10.31
08.11.10
08.10.21
08.10.17
08.10.06
08.10.03
08.09.29
08.09.19
08.09.26
08.09.12
08.09.05
08.08.31
08.08.15
08.08.09
08.08.04
08.07.29
08.07.26
08.07.18
08.07.07
0
08.06.18
5 08.06.23
Protein of PM10 (µg m-3)
35
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H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
Table 1 Summary of total protein concentrations (mg m3) in different areas. PM Period of species sampling
Site
TSP
Oct. 95 to May 96
PM10
Oct. 95 to May 96 Aug. 2003 to Jan. 2004 Dec. 1998 to Jan. 2000 1 day a week, 1991 Jun. 2008 to Feb. 2009
Los Angeles Long Beach Rubidoux Rubidoux
PM10
PM10 PM10
North Carolina
Mean
Reference
1.5e5.8 0.6e5.8 1.7e4.3 2.1e3.9
Miguel et al., 1999
0.125 0e0.2
South of western Siberia Mexico City Hefei, China
Range
11.42
0e3.5
Menetrez et al., 2007 Belan et al., 2000
0e2.54
Rosas et al., 1995
2.08e36.71 This study
city with machinery, electronic, chemistry, steel, textile, cigarette manufacturing factories and other industries. The process of industrialization and urbanization of the city has led to the reduction of green areas, biodiversity loss, heavy traffic, and soil pollution by human and animal excreta. The sampling site located in the center of Hefei (Fig. 1) is a traffic-intensive area undergoing periodic construction. For example, during the sampling period, Jinzhai Road viaduct was being built 50 m away from the sampling site. This construction could have generated a great amount of dust, which can cause biological materials to be aerosolized by vehicle traffic over the road, and thereby enhance atmospheric bioaerosol concentrations. On the other hand, agricultural dust sources may also have contributed to the high protein concentration in aerosol samples. Hefei is the capital and largest city of Anhui Province, which is a major agricultural province of China. In suburbs, there are a large number of agricultural production activities (e.g., cultivation of rice, vegetables, and other crops). These activities produce large amounts of pollen grains and mold spores that may enhance the level of biological aerosols. Both anthropogenic and agricultural
Fig. 3. (a) Protein (mg m3) of PM10, air pollution index (API) and mean visibility (VV, km) during the sampling period; (b) Relationships between protein (mg m3) of PM10 and air pollution index (API) and mean visibility (VV).
H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
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20
Protein Fog 15
10
5
0 Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Jan.
Feb.
Fig. 4. Monthly change in total protein concentrations (mg m3) of PM10 and the number of foggy days.
sources observed in this study are in agreement with previous reports. For example, in large metropolitan areas, previous longterm studies indicated that elevated, localized concentrations of PM10 around the urban area were often due to nearby soildisturbing activities (Chow et al., 1999). Boreson et al. (2004) estimated that more than 70% of coarse particles were generated from road dust, agriculture, and construction activities in Phoenix, and coarse PM were higher at the urban fringe compared to the natural desert. Road dust present on the streets of southern California was shown to contain a significant portion of organic protein material (Miguel et al., 1999). More discussion on the sources is presented below. 3.3. Seasonal variation The average monthly total protein concentration of PM10 is shown in Fig. 4. From Jun. to Nov. 2008, the protein concentration increased gradually, peaking at 36.71 mg m3 in Nov. 2008. Figs. 2 and 4 clearly showed that total protein concentrations were higher in winter than in summer. The seasonal variations appeared to be related to changes in precipitation. As shown in Fig. 5, the protein concentration of PM10 and precipitation amount were inversely related during the sampling period, i.e., a high level of protein was
observed in the dry season, while a low level of protein occurred in the wet season. Similar observations have been reported in Mexico City where protein concentrations of aerosols in the dry season were higher than those in the wet season (Rosas et al., 1995). Likewise, both PM10 and endotoxin levels were lower on days with precipitation in Southern California (Mueller-Anneling et al., 2004). This phenomenon has been ascribed to the rainfall that swept particles to the ground in the rainy season and the low moisture of soils that enhanced aerosolization of particles in the dry season. Moreover, autumn and winter are the foggy seasons in Hefei. Fig. 4 showed that the number of foggy days was much higher during autumn and winter than during other seasons, e.g., there were 12 foggy days in November 2008 alone. Sampling dates of October 17e19, November 13e15, 23e24, and 29 of 2008, and January 19e21 of 2009 were all foggy days, during which the pollutants can combine with water vapor in air to make more PM materials. The concentrations of protein and API were higher during these periods, and the monthly protein level in November was the highest. In addition to weather conditions, the sources of ambient proteins could also explain seasonal fluctuations. To determine the sources, PM10 samples with high protein levels collected during the dry season of Sep. 08 to Jan. 09 (samples not associated with precipitation or fog) were also analyzed for elemental composition and water-
60
PP(mm)
50 40 30 20 10 0
Protein (µg m-3)
40 30 20 10 0 6/1
6/21
7/11
7/31
8/20
9/9
9/29
10/19
11/8
11/28 12/18
1/7
1/27
2/16
3/8
Date Fig. 5. Protein (mg m3) of PM10 and precipitation amount (PP, mm) during the sampling period (shaded areas show the rainy and dry season, respectively).
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H. Kang et al. / Atmospheric Environment 54 (2012) 73e79
Table 2 Correlations between protein and trace element and water-soluble ions of PM10 from Hefei during Sep. 2008eJan. 2009. The bold values shows the significant correlation between total protein concentration and water-soluble ions Kþ and NO 3 in PM10, respectively.
Fe Ni Cu Zn Ba Pb V Mn Sr Kþ NO 3 SO2 4 MSA Protein
Fe
Ni
Cu
Zn
Ba
Pb
V
Mn
Sr
Kþ
NO 3
SO2 4
MSA
Protein
1 0.674 0.772 0.839 0.385 0.730 0.359 0.960 0.611 0.096 0.271 0.369 0.311 0.147
1 0.130 0.513 0.179 0.447 0.123 0.521 0.138 0.167 0.389 0.635 0.805 0.034
1 0.652 0.482 0.519 0.347 0.876 0.775 0.272 0.361 0.190 0.074 0.061
1 0.133 0.851 0.480 0.759 0.237 0.277 0.105 0.502 0.270 0.295
1 0.147 0.218 0.556 0.818 0.567 0.404 0.424 0.013 0.395
1 0.002 0.603 0.098 0.384 0.156 0.450 0.104 0.297
1 0.374 0.161 0.179 0.255 0.354 0.216 0.397
1 0.785 0.133 0.351 0.149 0.194 0.005
1 0.510 0.363 0.399 0.138 0.279
1 0.656 0.686 0.065 0.922
1 0.136 0.682 0.661
1 0.554 0.526
1 0.284
1
soluble ions. Correlation analysis (Table 2) indicated that the correlation coefficient between the total protein and water-soluble Kþ and NO 3 were 0.92 and 0.66 (P < 0.05), respectively, implying these substances had similar sources. Water-soluble potassium ion in PM samples, a tracer of biomass burning (Arimoto et al.,1995), was found to correlate with protein with a high coefficient of 0.92. In Hefei region, the period from September to November is the rice harvest season and as such there is heavy straw burning. The high correlation between protein and Kþ indicated a substantial contribution by biomass burning in the dry season. Rogge et al. (1991) reported that biomass burning could produce biomolecules such as cholesterol. It was reasonable to presume that proteins may be released as well. It was well known that NO 3 could come from emissions from both gasoline and diesel combustion, and power plant exhaust (Pacyna, 1998). The relationship with protein concentration thus indicates that anthropogenic sources are important contributors to high protein masses in aerosols. 3.4. Implication for health effects due to high protein masses in PM10 Protein concentrations were much higher in Hefei than those reported in other regions, illustrating a high biological loading over the city. It was documented that inhaled components of protein PM could stimulate alveolar macrophages and respiratory epithelial tissue to release cytokines or chemattractants that initiate an inflammatory cascade (Thorne, 2000). This is significant to asthmatics and those with impaired pulmonary function. In comparison with other cities in China, Hefei is considered small to medium-sized. There are many large or mega cities in the regions of Pearl River Delta, Yangtze River Delta, and Bohai of China. In these regions, there are intensive industries and human activities and serious environmental pollution. However, ambient biological aerosols are rarely reported. It can be speculated, nevertheless, that high protein levels exist in aerosols of these regions. Since the majority of China’s population is concentrated in regions with serious air pollution, more attention should be paid to the health risks caused by exposure to biological materials in aerosols. Additional studies are urgently needed to investigate the occurrence, distribution, source, and health effects of ambient proteins in China. 4. Conclusions The level and seasonal variations of total protein in ambient air in Hefei were investigated for the period of June 2008 to February 2009. The protein concentration in PM10 ranged from 2.08 to 36.71 mg m3 with an average of 11.42 mg m3. In comparison with
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