Air Qual Atmos Health DOI 10.1007/s11869-014-0264-9

Assessment and characterization of ambient indoor particulate matters using aerosol monitor, inductively coupled plasma mass spectrometry, and transmission electron microscopy Alaa A. Salem & Ismail A. El-Haty & Mohamed Al-Gunaid & Mahmoud Al-Balushi & Bashar Y. Abu-Hattab & Anas Al-Aidros & George O. Odhiambo

Received: 18 January 2014 / Accepted: 22 April 2014 # Springer Science+Business Media Dordrecht 2014

Abstract In this work, we studied the levels of ambient indoor particulate matters in some work premises of Al-Ain city during the months June–July 2013. Work premises included United Arab Emirates University (UAEU) campus, hospitals, and schools. We also studied the chemical composition and morphology of collected particulate matters using inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscope (TEM). Our results indicated average total concentrations less than 50.00 μg/m3 for PM1.0, PM2.5, PM4.0, plus PM10.0 in closed sites. Sites crowded with customers coming in and out such as entrances of hospitals and municipality gave average total concentrations in the range 160.0–200.0 μg/m3. Higher average total concentrations were found in sites with high outdoor air exchange. Particulate matters in the city ambient air originate from neighboring deserts and mountain and carried out by storms covering the country for different time intervals over the year. Correlation between the levels of particulate matters (PMs) and metrological parameters during the time of study was found insignificant. ICP-MS elemental analysis of collected particulate matters revealed sulfur and silicon-based particles containing significant amounts of calcium, sodium, boron, aluminum, magnesium, potassium, and chlorine. TEM imaging of collected particles showed clusters of crystalline and amorphous particulates corresponding to the silicate and sulfate matrices, respectively. Although the levels we recorded for particulate matters are generally in accordance with the United Arab Emirates and WHO standards for indoor PMs, our findings are important since long exposures to silicate and sulfate particles represent high risk factors on public health. A. A. Salem (*) : I. A. El-Haty : M. Al-Gunaid : M. Al-Balushi : B. Y. Abu-Hattab : A. Al-Aidros : G. O. Odhiambo Department of Chemistry, College of Science, UAE University, Al-Ain, P.O. Box 1551, United Arab Emirates e-mail: [email protected]

Keywords Indoor air . Particulate matters . Health risks . Al-Ain . TEM . ICP-MS

Introduction The impact of indoor pollutants on humans is a function of their concentrations and exposure times. Closed spaces confine air pollutants and allow them to accumulate up to 50 times higher than outdoors (Samet and Spengler 1991; Afshari et al. 2005). Times spent indoor is dependent on climate and might exceed 85 % of human life in extreme climates (Jenkins et al. 1992). Therefore, most of the body’s air intake during a lifetime is home inhaled. Subsequently, most environmental illnesses originate from exposures to indoor pollutants, of which particulate matters carry many health risks (Sundel 2004). Particulate matters with aerodynamic diameters of less than 10 μm (particulate matter (PM)≤10.0 μm) when inhaled, travel into the lower respiratory tract entering the smaller airways, trachea, bronchi, bronchioles, and alveoli causing greater respiratory health risks than other air pollutants (Samet and Spengler 1991; WHO 1987; Ashmore and Dimitroulopoulou 2009). Inhaled particles are slowly released from the body and impair healthy cells and tissues (Miller 2000). The large surface areas per unit mass of particulate matters make them excellent carriers for adsorbing inorganic and organic compounds that cause lung, cardiac, cancer, and other diseases. Associations between mass concentrations and aerodynamic diameter of respired particles and disease such as pulmonary and cardiovascular diseases were established (Pope et al. 2002; Dockery et al. 1993; Health Effects Institute 2000; WHO 2004). Duffin has shown that toxicity of particulate matters may increase with decreasing particle

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size. Nanosized particles are regarded the most toxic (Duffin et al. 2002). As the health implications of particulate matters have become evident, studying the physical and chemical characteristics of particulate matters in different urban areas has become an important area of research (Atkinson et al. 2010). Exposures to ambient indoor PMs have been accounted responsible for 4–8 % of global premature mortality rate (Smith and Jantunen 2002). Exposure to ambient indoor PMs was also reported as the cause of asthma in around 5 % of UK’s population. Unofficial equivalent figure of around 15 % was reported in the United Arab Emirates (UAE). Children are more vulnerable to health hazards caused by PMs. Indoor particulate matters are often two to five times higher in school facilities compared to outdoors, a reason for triggering respiratory symptoms among children (Afshari et al. 2005; Wichmann et al. 2010). In 2005, the Health Authority - Abu Dhabi (HAAD) reported that 90 % out of 150,000 patients treated at Al-Ain public health clinics suffered from respiratory diseases. In response to this threat, we monitored outdoor air pollutants in the city on 2005–2006. Our results indicated that gaseous air pollutants in Al-Ain were below the national and international standards. In conclusion, we attributed that the above health risks to outdoor PMs originate from sand dunes around the city and other sources (Salem, et al. 2009). Recently, the National UAE Forecasting Center reported that storms carrying PMs originating from neighboring deserts have covered the UAE for average time intervals of 20 % over the years 2007–2011. Also, the Abu Dhabi Environmental Agency (ADEA) has ranked indoor air pollution as the second highest in the national ranking scale of environmental risks. Recently, the UAE National Environmental Health project has concluded that 6–7 % of annual deaths are possibly attributed to indoor air pollution (State of Environmental Health in UAE 2009). Also, Li and others have reported that out of 609 deaths reported in 2007, 545 deaths were attributed to ambient PMs and 62 were attributed to ozone smog (Li et al. 2010). They concluded that anthropogenic ambient air pollution, especially particular particulate matters, are responsible for a considerable public health impact in UAE in terms of premature deaths. On the other hand, the types and concentrations of indoor PMs in residential areas are generally dependent on indoor and outdoors’s emissions, frequency of sand and dust storms carrying billions of tiny particles, and on air exchange rate. Indoor activities such as smoking, fuel combustion for heating or cooking, suspended particles by walking, vacuum cleaners, and others may represent sources of indoor PMs’ emission (Klepeis et al. 2001; Monn 2001; Luoma and Batterman 2001; Graudenz et al. 2005; Ito et al. 2011). It is well established that chemical composition of PMs is dependent on its sources which differ from one region to another. Elemental carbon,

organic compounds, ammonium sulfate, ammonium nitrate, metal-rich coarse dusts, sea salt, and bound water are the major components of particulate matters (Harrison et al. 2003). Analysis of submicron PMs is still a challenging task. Inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) are powerful analytical techniques for bulk analyses and characterizing size and morphology of individual, small clusters, or agglomerated particles in the submicron size range, respectively. These techniques are capable of giving chemical fingerprints that can be used for identifying and classifying different particulate matters (Gross et al. 2000; Silva and Prather 2000). This work aims to assess the levels of indoor PMs in the ambient air of some working premises in Al-Ain city. Locations subjected for study include the United Arab Emirates University (UAEU) campus, governmental entities, hospitals, and schools. It also aims to identify size distribution of these floating particles which is firmly related to their health impacts. ICP-MS and TEM will be used for characterizing chemical composition and morphology of collected particulate matters. The results obtained will be correlated with metrological parameters during the time of study and will also serve to develop a baseline data that could be useful to the makers of health policies and for further indoor assessments of PMs in the city and the state.

Experimental Materials We used polycarbonate microfilters (Track-Etch membrane) with pore size of 0.2 μm and 50 mm diameter manufactured by Sartorius Stedim Biotech, Germany, for samples collection. Samples were digested in concentrated nitric acid. Particles on the filters were washed out using 10 % ethanol-water.

Apparatus DustTrak™ DRX Aerosol Monitor, model 8533, TSI Inc., USA has been used to simultaneously measure sizeaggregated mass fractions of PM1, PM2.5, PM4.0, PM10, and total suspended particulate matter (TSP). This aerosol monitor is based on laser optics and counts single particles in a series of size ranges. It is well suited for assessing human exposure to aerosols. ICP-MS, model Perkin Elmer-Nexion 300x ICP-MS was used for studying the chemical composition of collected particulate matters. A TEM, model Philips CM-10 was used for studying their morphology

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Procedures Measurement of particulate matters’ levels The DusrTrak instrument was positioned on a horizontal table in the selected sites and zero calibrated before each measurement’s cycle. Sampling times of 4 h were set for each measurement’s cycle using a constant flow of 1.6 m3/h. Each measurement cycle was repeated in the same site or different sites in the same building. Differential data were collected and analyzed. To collect samples, a 72-h sampling time was set. Particles were collected over polycarbonate Track-Etch membrane of 0.2 μm and 50.0 mm diameter. To study the chemical composition, particulate matters collected over membrane filters were suspended into 10 % ethanol-water solution, concentrated to 1.0 ml, and digested with 0.5 ml concentrated nitric acid. The chemical composition of the resulting solution was analyzed using the Nexion 300x ICP-MS. To study the morphology of the particles, a Philips CM-10 STEM operated at 100 kV with spot size of 2–3 μm and

Fig. 1 Variation of PMs’ concentration over a 4-h time period in UAEU buildings C1corridor (UNC1-C), C1-room (UNC1-R), crescent-corridor (UNCRE-R), C6-corridor (UNC6-C), E4-corridor (UNE4C) and H4-room (UNH4-R)

magnification power of 1,400–7,400× was used. Particles were collected over 200 mesh Copper/Formvar-coated grid mounted into the DusrTrak instrument. Scanned particles were selected from different spots on the grid square by going to low magnification mode in the microscope, centering on the region of interest within the grid square through the viewing screen, and increasing the magnification until the particles were visible. Sites descriptions This preliminary screening study was conducted from 29 June to 7 August 2013 in selected residential entities in Al-Ain city. The study covered 37 locations—19 in the UAE University, 10 in the hospitals (Tawam and Al-Ain), 3 in the city municipality, 2 in the school (House of Sciences private school), and 3 in the Zayed House for Islamic Culture nearby the city’s cement factory. The UAEU enrolls around 13,000 students and 1,200 faculty member into a newly well-designed campus. In this study, we assessed PM levels in nine buildings including the lecturing rooms, labs, administration crescent building, and

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one student’s hostel (F1, F2, F3, F4, C1, C6, H4, CRE, and male hostel). Hospitals screened included the two governmental hospitals in the city—Tawam and Al-Ain. The Tawam Hospital consists of several buildings. The main building comprises the emergency department, the wards, and laboratories. The outpatient polyclinic building is visited by around 20,000 patients monthly (Tawam Hospital). On the other hand, Al-Ain hospital comprises 402 beds and around 35 medical departments. The hospital treats ∼20,000 in-patients and 320,000 out-patients annually (Al-Ain Hospital). Sites subjected for investigations include outpatient, wards, and special care neonatal baby unit (SCBU). The Al-Ain municipality is a five-floor building and provides services for several thousand costumers per month. Schools were represented in this study by the House of Sciences School, one of the biggest private schools in Al-Ain. It

comprises around 1,300 students in grades 1–12 and kindergarten, 50 classes, and 75 employees. The area near the city’s cement factory was screened through the Zayed House for Islamic Culture (ZHIC), a cultural institution located 2 km away from the factory and comprises of lecture rooms, recreational rooms, gym, hostel, and sports facilities. All the above buildings are air conditioned.

Fig. 2 Variation of PMs’ concentration over a 4-h time period in Tawam Hospital Polyclinic (HOSTPC-C), human resources (HOSTHR-C), medical ward (HOSTMED-C)), Al-Ain Hospital medical ward (HOSTJ

OBD1 C), neonatal unit (HOS J SCBU-R), and Al-Ain municipality corridor (MUME-C)

Results and discussion Screening of particulate matters Particulate matters pose significant health impacts. Therefore, monitoring indoor and outdoor air pollutants has become a main objective on the agenda of governments and local

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Figure 3 shows the individual average concentrations of PM1– 10 and their total averages in the 19 studied UAEU sites. PM1, PM2.5, PM4, PM10, and total average ranging 1.0–14.0, 2.0– 21.0, 3.0–26.0, 5.0–38.0, and 6.0–59.0 μg/m3 were respectively obtained. Our results are less than the ADEA quality standard (PM10.0 <150.0 μg/m3) and the WHO quality standard (PM2.5 <25 μg/m3, PM10 <50 μg/m3). These results explain the fact that all UAEU buildings are neatly air

7 6

UN E4 R

UN E4 C

UN C1 R

UN C1 C

UN SBH…

2 1 UN SBH R

UN SBH…

UN CRE R

UN CRE C

UN H4 C

5

UN C6 R

UN F1 C

UN F1 R

UN C6 C

4 3 4 3 4 2 2 2 UN H4 R

2 1 UN F3 R

0

3 UN F2 C

5

5

UN F3 C

10

10

UN F2 R

Concentration (µg/m3) Concentration (µg/m3)

30

14

21

16

14 13

UN E4 R

UN E4 C

UN C1 C

UN C1 R

UN SBH R

4 2 UN SBH…

UN C6 R

UN C6 C

UN CRE R

UN CRE C

UN H4 R

UN H4 C

UN F1 R

UN F1 C

UN F3 R

UN SBH…

10

6 3 3 2 2 5 4 5 3 2

UN F2 R

0

6 UN F2 C

10

12

UN F3 C

20

PM4 26

22

19 17

15

UN E4 R

UN E4 C

UN SBH R

UN SBH…

UN C6 R

UN C6 C

UN C1 R

6 3

3 3

UN C1 C

11

UN CRE R

UN CRE C

UN H4 C

UN H4 R

UN F1 R

UN F1 C

7 5 3 3 6 5 3 UN F3 R

0

9

UN F3 C

10

18

UN F2 R

20

UN SBH…

30

UN F2 C

Concentration (µg/m3)

PM2.5

37 38 28

25

19

21

UN E4 R

UN C1 R

UN C1 C

UN SBH R

UN SBH…

4 UN SBH…

UN C6 R

UN C6 C

7 5

6 UN CRE R

10

UN CRE C

UN H4 C

8 UN F1 R

UN F1 C

UN F3 R

UN F3 C

5 7

12

17

UN H4 R

20

UN E4 C

35

28

UN F2 C

40 30 20 10 0

UN F2 R

Concentration (µg/m3)

PM10

51

45

59 35

26 22 UN E4 R

UN E4 C

UN C1 R

UN C1 C

UN SBH R

UN SBH…

6 UN SBH B3 C

UN C6 R

UN C6 C

11 6 UN CRE R

UN H4 C

16 9 UN CRE C

27 10

35

UN H4 R

18

UN F1 R

UN F3 R

UN F3 C

6 10

UN F1 C

28 32

UN F2 R

(µg/m3)

PM TOTAL 80 60 40 20 0

UN F2 C

Quantitative findings in investigated sites

PM1 15

Concentration

authorities in many countries. Both inhalable (PM10) and respirable (PM1.0–4.0) particles go into the lungs. Fine particles further go to the deepest portion of the lungs, passing to the blood, and carried out through the whole body. These particles can alter the body’s defense system against foreign materials, damage lung tissues, aggregate existing respiratory and cardiovascular diseases, and might lead to cancer. Asthmatic people are at the highest risk, while influenza, lung, heart, and cardiovascular patients, elderly, and children are also at risk. Studies showed an 18 % increase in deaths from heart diseases among people with long-term exposure to PMs. The reason was attributed to heart inflammation results in ischemia, rhythms, heart attacks, heart failure, or cardiac arrest. Premature deaths have been reported. The US Environmental Protection Agency (US-EPA) 24-h exposure standards for PM10 and PM2.5 are 150.0 and 65.0 μg/m3, respectively. Their annual exposure standards are 50.0 and 15.0 μg/m3, respectively. Several worldwide air quality indices recognize PM’s concentration in the range 0.0– 50.0 μg/m3 as good, 51.0–100.0 μg/m3 as moderate, 101.0– 150.0 μg/m3 as unhealthy for sensitive groups, 151.0– 200.0 μg/m3 as unhealthy, 201.0–300.0 μg/m3 as very unhealthy, and 301.0–500.0 μg/m3 as hazardous. In this study, the average indoor concentrations of PM1.0, PM2.5, PM4.0, and PM10.0 were measured during the period 29 June to 7 August 2013 in the UAEU campus and some work premises in Al-Ain city. The results obtained were compared with the quality standards of ADEA and international standards. Figures 1 and 2 show the variations in PM concentrations in different sites using a 4-h screening time. Intervals between 4 and 72 h were imposed based on needs. Steady conditions in the green zone with concentrations below 50.0 μg/m3 were generally observed in the majority of investigated sites. Peaks with PM total average up to 300 μg/m3 were observed in few locations. The main entrances of Al-Ain Municipality and Tawam Polyclinics recorded PM levels of 160.0 and 200.0 μg/m3. The reason is attributed to the high number of customers coming in and out associated with air exchange through opening doors. Thus, it seems that outdoor PMs and type of indoor activities are responsible for the observed high PM concentrations (Branis et al. 2005).

Fig. 3 Average concentrations of PM1, PM2.5, PM4, PM10, and total average in different UAEU buildings F1, F2, F3, H4, crescent, C6, student hostel, C1, and E4 referred as UNF2, UNF3, UNF1, UNH4, UNCRE, UNC6, UNSB, UNC1, and UNE4, respectively. C corridor, R room, and H hall

conditioned with limited ventilation. The highest relative PMs’ concentrations were recorded in the student hostel and

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the administration buildings. This reason could be attributed to air exchange during coming in and out to both sites of students or employees. Figure 4 shows the variations in PM1.0–10.0 and their total average for the investigated hospitals’ sites. Figure 4a shows change in PM1.0, PM2.5, PM4.0, PM10.0, and their total average recorded in Tawam Hospital’s sites. Average concentrations in the ranges 2.0–14.0, 4.0–22.0, 5.0–35.0, 5.0–93.0, and 6.0– 163.0 μg/m3 were respectively obtained. These results are generally lower than the standards. However, the 22.0 and 93.0 μg/m3 concentrations, recorded respectively for the PM2.5 and PM10 in the polyclinics building, are moderate and might represent a threat for outpatients resonating to these

24

12

13

PM2.5

41

40

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HOS J SCBU R

HOS J MED2 C

18 HOS J NEWT C

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HOS J OBD2 C

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PM TOTAL Concentration (µg/m3)

38

HOS T CAF C

HOS T MED2 C

45

HOS T SB C

24

HOS T HR C

6

13 HOS J SCBU R

7

PM TOTAL

163

HOS J SCBU R

PM10

31 15

10 HOS J SCBU R

10 HOS J MED2 C

HOS T CAF C

9 HOS T CAF C

HOS T MED2 C

21

8

PM4

HOS J MED2 C

HOS T SB C

HOS T MED2 R

27

HOS T SB C

14

HOS T HR C

5

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HOS J NEWT C

HOS T HR C

PM10

10

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HOS J NEWT C

HOS T MED2 C

5

HOS J OBD2 C

HOS T CAF C

9

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HOS T SB C

11

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5

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HOS T MED2 C

PM4

Concentration (µg/m3)

4

15 10 5 0

Concentration (µg/m3)

6

HOS T MED2 R

HOS T PC C

8

HOS T MED2 R

200 160 120 80 40 0

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93

HOS T PC C

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HOS T PC C

Concentration (µg/m3)

40 30 20 10 0

22

HOS J SCBU R

HOS J MED2 C

5

HOS J MED2 C

8 HOS J NEWT C

6

HOS J NEWT C

HOS T SB C

HOS T CAF C

2

PM1 30 20 10 0

HOS J OBD2 C

5

HOS T HR C

HOS T MED2 C

HOS T MED2 R

4

6

Concentration (µg/m3)

PM1 6

PM2.5 30 20 10 0

Concentration (µg/m3)

(b)

14

HOS T PC C

15 10 5 0

Concentration (µg/m3)

Concentration (µg/m3)

(a)

Concentration (µg/m3)

Fig. 4 Average concentrations of PM1, PM2.5, PM4, PM10, and total average in different sites of Tawam Hospital (a) and Al-Ain Hospital (b). Tawam’s sites are referred as HOSTPC for the polyclinic building, HOSTMED2 for the medical ward2, HOSTHR for the HR building, HOSTSB for Starbucks area, and HOSTCAF for the hospital main cafeteria. AlAin Hospital sites are referred as HOSTJ OBD1 for the medical ward, HOSJ NEWT for the new tower building, HOSJ MED2 for the medical 2 building, and HOSJ SCBU for the SCBU building. C corridor, R room, and H hall

clinics. On the other hand, Fig. 4b shows the average recorded concentrations in Al-Ain Hospital. PM1, PM2.5, PM4.5, PM10, and their total average ranging 5.0–24.0, 8–13.0, 10–16, 7.0– 31.0, and 18.0–41.0 μg/m3 were respectively obtained. These values are again matching both ADEA and WHO standards. Increase in PM concentrations was associated with the number of patients and visitors resonating to these sites and to increased outdoor air exchange. Similar findings were found in the three sites screened in Al-Ain municipality (Fig. 5a). Concentrations in the ranges of 4.0–11.0, 4.0–11.0, 8.0–26.0, 15.0–64.0, and 22.0–108.0 μg/ m3 were respectively obtained for PM1–10 and their total average. The 64.0 μg/m3 was recorded for PM10 in the

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(b)

15

20

entrance lobby of the municipality. The reason could be attributed to the high number of resonating customers. Figure 5b shows the average concentrations recorded in the screened school’s sites. PM1–10 and their total average gave values in the ranges 12.0–15.0, 17.0–19.0, 20.0–25.0, 24.0–37.0, and 25.0–44.0 μg/m3, respectively. These results categorized the school in the green portion of the PM index. The area adjacent to the cement factory was screened in ZHIC. Average concentrations lower than standards (≤40.0 μg/m3) were recorded. The reason could be attributed to the wind’s direction and because the site is an air-conditioned

SCHOOL C

PM4

37

PM10

PM TOTAL 50 40 30 20 10 0

44 25

SCHOOL R

Concentration (µg/m3)

25 MU ARC

MU ME C

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MU R

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MU ARC

MU R MU R

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19

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MU ME C

MU R

PM10

PM2.5

SCHOOL C

108

8

16

PM1

SCHOOL C

150

13

30 20 10 0

18

15

19

SCHOOL R

64

PM4

26

MU ARC

80 60 40 20 0

4

MU ARC

Concentration (µg/m3)

MU ME C

Concentration (µg/m3)

30 20 10 0

7

20

12

SCHOOL R

PM2.5 11

Concentration (µg/m3)

MU R

MU ME C

0

4

Concentration (µg/m3)

7

5

16 12 8 4 0

Concentration (µg/m3)

10

PM1

Concentration (µg/m3)

15 10 5 0

11

MU ARC

Concentration (µg/m3)

15

Concentration (µg/m3)

(a)

Concentration (µg/m3)

Fig. 5 Average concentrations of PM1, PM2.5, PM4, PM10, and the total average in different sites of the municipality (a) and the house of sciences’ school (b). Municipality sites are referred as MUMEC for the main entrance corridor, MUR for the main building room, and MUARC for the archive. School’s sites are referred as SCHOOLR for school room and SCHOOL C for the corridor

closed system. Thus, sites scanned are generally in the green zone of the PM index of both ADEA and WHO standards. Exceptions were generally attributed to outdoor air exchange and the large number of customers resonates to some sites. Metrological parameters during the time of study in the city showed daily average temperature ranging 36–41 °C, daily average humidity between 16 and 55 %, and daily average wind speed between 8 and 23 km/h (Al-Ain International Airport). Correlations of these metrological parameters with our recorded PM concentrations revealed insignificant correlations.

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Chemical characterization of particulate matters 1000

Table 1 Composition and relative parts per million concentrations of elements found in particulate matters collected from the Zayed House and UAEU campus Element

Concentration/ppm Zayed House

UAEU campus

B Na Mg Al

5.22 124.94 5.53 13.70

30,308.53 47,307.24 1,727.01 7,253.98

Si P S Cl K Ca Ti Cr Mn Fe Ni Cu Zn Br Sr Zr Ba

18.74 0.29 484.15 6.22 5.79 105.54 0.38 0.96 0.81 17.08 0.71 0.24 4.87 0.88 0.20 0.11 0.11

98,381.47 322.44 969,015.42 6,000.12 6,979.43 12,019.89 277.43 622.80 301.02 5,467.90 117.49 379.60 2,032.57 693.46 129.10 111.50 111.04

900 800

Concentration / ppm

Since Al-Ain is surrounded by sand dunes from all directions, and the whole country is exposed to storms coming from the great desert from time to time, silica-based particles are expected to be the major component of particulate matters detected in the city. Silica describes different forms of crystalline and amorphous silicon dioxide and silicate materials. Table 1 shows the ICP-MS elemental analysis of indoor particulate matters collected from the UAEU and the Zayed Culture House. In both locations, sulfur, silicon, sodium, calcium, aluminum, and iron seemed to be the major components. Boron, magnesium, chlorine, potassium, and zinc are minor components. Iron, zinc, lead, barium, strontium, bromine, manganese, chromium, and titanium were found as trace (≤1.0 ppm). These findings indicated that the particles are composed of mixed salts based on sodium and potassium silicates, calcium and magnesium sulfates (gypsum) as major components, and aluminate as minor component. These matrices are doped with a number of light and heavy elements (Fig. 6). These findings are important since exposures to silica dust are known to cause silicosis and increase the risk of

Zayed House

700

UAEU

600 500 400 300 200 100 0 Li Na Al P Cl Ca Ti Cr Fe Ni Zn Br Sr Mo I La Sm Pb

Element Fig. 6 Composition and relative parts per million concentrations of elements found in particulate matters collected from Zayed House (blue) and UAEU (red)

tuberculosis. Silicosis is an incurable fetal lung disease that can develop into lung cancer, pulmonary tuberculosis, and airways diseases with autoimmune disorders, chronic renal diseases, and other adverse health effects that may result in disability or death (WHO 2000). On the other hand, exposure to sulfate particulate matter has been associated with higher mortality rates compared to other particulate matters (Özkaynak and Thurston 1987). In a case study on more than 8,000 adults living in six US cities, Dockery et al. concluded a significant relationship between exposures to PM2.5 and sulfate fine particles and mortality. Exposures to total suspended particulates, aerosol acidity, sulfur dioxide, and ozone were found insignificant (Dockery et al. 1993). This significant correlation between increased mortality and exposure to sulfate and fine particulates was also confirmed through a bigger study on more than 500,000 subjects from 151 US metropolitan areas done by the American Cancer Society (1980–1989) (Pope et al. 1995). Daily hospital admissions for respiratory causes were correlated with exposures to PMs with a decrease in correlation strength from hydrogen ion>sulfates>PM2.5 > PM10 >total suspended particulates. Size and composition of particles were found important in defining the adverse effects of these particulate matters on human health (Thurston et al. 1994). Hospital admissions for cardiovascular diseases were also associated with PM10 and sulfates exposures (Schwartz and Morris 1995; Burnett et al. 1995). Figure 7 shows TEM images of particle aggregates collected from Building F2, UAEU campus. Spherical particles possibly attributed to amorphous sulfate and silicates are shown in Fig. 7a, b. Figure 7c, d shows tetrahedral or hexagonal particles possibly attributed to crystalline silicates.

Air Qual Atmos Health Fig. 7 TEM structural image of particulates aggregates collected from Building F2, UAEU campus. Spherical particles in a and b are possibly attributed to amorphous sulfate and silicates. Tetrahedral or hexagonal particles in c and d are possibly attributed to crystalline silicates. Bigger aggregates with particles’ aerodynamic diameters of 30– 115 nm are shown in a, b, and d. Smaller aggregate with particles’ aerodynamic diameters of 80– 112 nm are shown c

a

b

c

d

Aggregates in Fig. 7a, b, and d are composed of particulates with smaller aerodynamic diameters ranging 50–115, 40–60, and 30–50 nm, respectively. Aggregates in Fig. 7c are formed from particulates with larger aerodynamic diameters ranging in 80–110 nm. Amorphous aggregates are possibly made of gypsum (calcium sulfate, CaSO4) mixed with traces of Mg, B, Zn, Be, and Fe (Pósfai et al. 1994). Crystalline aggregates are possibly silicate matrix mixed with traces of light and heavy elements (K, Br, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Se). Amorphous and crystalline aggregates are normally based on morphologically different types of slats (Smith et al. 2012). Storms originate from the great desert and sand dunes surrounding the city are the major sources of silicate particulates in the ambient outdoor and indoor city air. Sulfate particulates (gypsum) might originate from the Hafeet Mountain located in the southwest part of the city and minor contribution are from other nonpoint sources. Although our results indicated that the levels of PMs in investigated sites were generally in the green range of the PM index, they are still highly alerting since long-term exposure—even to low concentrations—carries significant health

risks. This is supported by the work published by Dockery indicating that exposure to 10 μg/m3 PMs revealed total mortality relative risk factors of 1.10 for inhalable particles (PM15–10), 1.14 for fine particles (PM2.5), and 1.33 for sulfate particles in humans (Dockery et al. 1996). It is also supported by the results of Raizenne et al. indicating that long-term exposure to low PM levels demonstrated mortality relative risks of 1.34, 1.29, and 1.96 for PM2.5, PM10, and sulfate particles, respectively (Raizenne et al. 1996). In addition, particle depositions in human lungs and noses have been correlated with its aerodynamic diameters. PMs<100 nm and PMs≥5,000 nm are ∼60 and ∼80 % deposited in the lungs, respectively, while PMs 1,000–3,000 nm are ∼20 % deposited in the noses (WHO 2000; Becquemin et al. 1991). Therefore, our findings are very important starting point not only for evaluating respiratory and nonrespiratory health risks in the city, but also for setting long-term strategies about the health impacts of indoor and outdoor PMs in the city. For this purpose, a long-term study on levels of PMs and their health impacts is strongly recommended in the near future.

Air Qual Atmos Health

Conclusion

References

Indoor particulate matters in Al-Ain city were assessed by screening 37 locations in the UAEU campus, hospitals, municipality, schools, and an area near the cement factory. The results indicated that concentrations of PM1.0, PM2.5, PM4.0, PM10.0, and total average were generally below the quality standards of ADEA and WHO that amounted to 50.0 μg/m3. Relative higher PM concentrations were recorded in the entrance lobby of the municipality (64 μg/m3) and in the polyclinics’ corridor of Tawam Hospital (93 μg/m3), the restaurant of students’ hostel, and the lobby of the crescent building. The reason was attributed to outdoor air exchange and the increased numbers of customers resonate to these sites. Correlation between PM levels and metrological parameters during the time of study was found insignificant. Chemical analysis indicated that particulate matters are composed of mixed salts based on sodium and potassium silicates, calcium or magnesium sulfates (gypsum), and aluminate matrices. These salts are doped with traces of some light and heavy and elements. TEM morphological study indicated the presence of crystalline and amorphous aggregates with the particles’ aerodynamic diameters in the range 40–115 nm. Crystalline and amorphous aggregates were attributed to silicate and sulfate salts, respectively. These particles are carried to the city by wind or storms from mountains and sand dunes surrounding the city and deserts surrounding the country. Although our results indicated that the levels of PMs in investigated sites were generally in the green range of the PM index, they are still highly alerting since long-term exposure—even to low concentrations—carries significant health risks. Long-term exposure to PM level as low as 10 μg/m3 has been shown to carry significant risk factors on mortality and morbidity of patients and healthy subjects. Exposures to silicate and sulfate particulate matters as well as PM1, PM2.5, and PM10 represent higher health risk factors compared to other air pollutants. Our results also indicated that detected particles have aerodynamic parameters in the range 40–115 nm. These particles are largely deposited in the lungs, enter blood streams, and possibly cause serious health effects. Therefore, our findings are very important starting point not only for evaluating respiratory and nonrespiratory health risks in the city, but also for the needs of setting long-term strategy about the health impacts of indoor and outdoor PMs in the city. For this purpose, a long-term study on the levels of PMs and their health impacts is strongly recommended in the near future

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Acknowledgments The authors are gratefully acknowledging the United Arab Emirates University for the financial support provided to run this work through the SURE-2013 program (Grant #31S099). Without their supports, this work would have not been executed.

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