International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 54 Ambient Air Particulate Matter Levels in Selected Urban Centres of Niger Delta Region, Nigeria Ngele S. O1* and Onwu F. KDepartment of Industrial Chemistry, Ebonyi State University, P.M.B. 053 Abakaliki, NIGERIA Department of Chemistry, Michael Okpara University of Agriculture Umudike, P.M.B 7267 Umuahia, Abia, NIGERIA Available online at: www.isca.in, www.isca.me Received 3rd February 2015, revised 9th March 2015, accepted 16th April 2015 AbstractThis study measured total suspended particulate (TSP) matter load, particulate matter with aerodynamic diameter ten micrometer or less (PM10) and two and half micrometer or less (PM2.5) in five urban centres in the Niger Delta region, Nigeria in the dry and wet seasons from December, 2008 to September, 2009 using photometric laser-based particle counter instrument. The results showed that the seasonal mean varied in the range of 72.25±12.32- 320.06±235.42 µg m-3for the TSP in the dry season and 16.31±4.77 – 87.94±27.32 µg m-3 forthe wet season. The seasonal mean of (PM10) ranged from 42.44±9.74 - 181.38±50.64 and 6.94±2.05 – 59.88±20.89 µg m-3 for the dry and wet seasons respectively. Similarly, PM2.5 gave 13.56±2.63-55.00±29.45 µg m-3 and 1.81±1.11-12.88±3.48 µg m-3respectively for the dry and wet seasons. The annual mean of TSP in all the cities were within World Health Organization (WHO) annual guideline limit of 230-250 µg m-3 Also PM10 annual levels exceeded the 20 µg m-3 WHO annual guideline limitwhile PM2.5 annual levels in two cities (Uyo and PortHarcourt) exceeded the US annual National Ambient Air Quality Standard (NAAQS) of 15 µg m-3. The F-test statistics revealed statistical significant difference in the dry and wet seasonal means of TSP in Eket and Uyo (p0.05). The PM10 dry seasonal level in Eket and Uyo wetseasonal level were significant (p0.05) while PM2.5 dry seasonal level in Eket and wet seasonallevels in Uyo and PortHarcourt were statistical significant (p0.05). The study concluded that the high levels of PM10 and PM2.5 in all the cities monitored especially in the dry season may present a potential public health risk. Keywords: Ambient air, environmental pollution, fine, coarse, particulate matter, south-south Nigeria. Introduction Suspended particulate matter (SPM) is one of the deleterious air pollutants. It is a complex mixture of different particle sizes. Processes that emit particulate matter into the atmosphere include: volcanic eruptions, geochemical sources, windblown dust, soil re-suspension, spray from marine sources, power plant emissions, agricultural and industrial emissions and vehicular emissions1,2. Historically, SPM is measured as total suspended particulate (TSP) and it refers to SPM in the air of all sizes. The TSP is an archaic regulatory measure of the mass concentration of SPM and was used by regulatory agencies such as the USEPA until 1987. Studies involving particle transport and transformationsuggest that ambient air SPM commonly occur in two modes namely the fine (aerodynamic diameter two and half or less, PM2.5) mode and the coarse (aerodynamic diameter 2.5-10 µm, PM10) mode3-. The fine or accumulation mode ( PM2.5) is also referred to as respirable particulate matter because when inhaled, it can penetrates deep into lower region of the human respiratory tract9,10. Findings from research on human health effect of SPM have made the health professionals to generally recognize that the particle sizes ten micrometer or less are responsible for many of the significant adverse health effects attributable to particulate matter such as risk of lung cancer, aggravation of respiratory and cardiovascular diseases11-13. Studies have correlated PM10 and PM2.5 to aggravation of asthma attack, pulmonary inflammation, daily mortality and a number of hospital admissions14-16. The negative effects of PM also include retardation in growth and yield of plants17, reduction in visibility18, 19 and deterioration of the physical environment20. The regulatory focus of PM has since changed to reflect the current knowledge with regard to particle size and influence on the adverse health effect caused by particulate. For instance, in June, 1987, the USEPA promulgated a new size-specific air quality standard based on PM10 as a measure of the ambient air SPM, hence replacing the hitherto used TSP standard (EPA/625/R-96/010A). The PM10 standard for ambient air PM has also been further revised to include the PM2.5 as among the criteria pollutants to be monitored and regulated by USEPA. The European communities (EC) has also passed a directive for the PM10 and PM2.5 to be the regulatory PM standard in their member states with a daily and annual PM10 average of 50 µg m-and annual PM2.5average of 15 µg m-3 Measurements of TSP, PM10 and PM2.5 in the different regions of developed world are well documented in the literature21, 22. In Nigeria, researchers have also reported ambient air TSP and International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 55 PM10 in few urban cities such as Ile-Ife, Calabar, Warri, Lagos and Abakaliki23-28. However, published report on PM monitoring campaign in Nigeria is still limited in scope in terms of the number of cities covered and duration of measurement. This study was aimed at providing an estimate of TSP, PM10and PM2.5 concentrations in selected five cities in the South-South (Niger Delta region) Nigeria. Material and MethodsThe study Area: The study covered five major cities namely Eket, Uyo, Calabar, Ogoja and Port-Harcourt (all in South-South Nigeria). The area is located within latitudes (4ş-6.5ş) N and longitudes (5ş-9ş) E. The area has an approximate population of 21,014,675 according to the 2006 census figure. The climatic condition is tropical, characterized by wet and dry seasons. The wet season sets in between April and October while the dry season is usually between November and March. The phenomena and activities in South-South Nigeria that have potential of impacting on the environment (air pollution) include the sea spray, salt volatilization from the ocean, emission of gases from the decaying of organic substance in swampy environment, emissions from the agglomerations of industries (large, medium and small scale) in the area especially in Port Harcourt, emission from the oil exploration and exploitation activities including refinery and gas flaring operations, that are common in the area, emission from vehicular traffic with its preponderance in the state capitals and large commercial cities. Sampling site selection: In each of the cities monitored, a site was chosen in the ‘heart’ of the city based on visible human activities, high population density and traffic volume. The coordinates of each site was measured with Garmin global position system, model etrex H (Taiwan).Table-1 Sampling Location, Name and GPS Coordinates S/No City Site Name Coordinates 1 EKET Ataobong junction N04 0 39.03 1 E007 55.63 2 UYO Abak Road by Edrock Junction N05 0 01.95 1 E007 55.28 3 CALABAR EPZ junction N05 0 01.13 1 E008 19.85 4 OGOJA Catheral Round about N06 0 39.34 1 E008 48.45 5 PORTHARCOURT Rumuokwuta Junction N04 0 50.22 1 E006 59.28 Monitoring protocol: The concentrations of the suspended particulate matter (TSP, PM10 and PM2.5) in the ambient air of the monitored sites was determined by means of a digital read out electronic instrument, Aerocet Model 531-9800 Rev. C (Metone Inc. U.S.A). The instrument has in-built particle count data for eight different particle size ranges including total suspended particulate (TSP), PM10, PM2.5 and proprietary algorithm to derive the mass concentration for particulate sampled. The sampler was held at a height of 2 m above ground level, the human breathing zone and the ambient air PM concentration reading recorded as displayed on the instrument's screen. Sampling time for each parameter was two minutes (that is time taken from switch on of parameter nub to display of reading on the screen). The frequency of the monitoring was such that a site was monitored one day in a week for twelve hours (6.00 am-6.00 pm) at an interval of thirty minutes for four months (16 weeks) in the dry season, December, 2008 to March, 2009 and four months in the wet season, June-September, 2009. The hourly mean level for the twelve hours per day per week of each parameter was averaged and the mean for the 16 weeks computed to obtain the seasonal mean for the parameters using statistical package for social science (SPSS) software, version 17. Results and Discussion The results of the seasonal variations of the mean TSP, PM10 and PM2.5 are presented in Tables 2, 3 and 4 and their relationships shown in figures-1A, B, C, 2A, B, C and 3A, B and C. The highest dry season TSP value of 320.06±235.422.36 g m-3within the period of the study was obtained in Uyo urban while the minimum value of 72.25±12.32 g m-3 was obtained in Ogoja urban. Similarly, in the wet season, PortHarcourt recorded the maximum level of 87.94±27.12 g m-3 while the minimum value of 16.31±4.27 g m-3 was obtained in Calabar. The annual mean TSP levels ranged between 44.35±39.46-195.22±176.55 g m-3 (table-2A). Across the cities, the mean seasonal TSP showed relatively higher levels in more urbanized cities of PortHarcourt and Uyo relative to less urbanized cities of Eket and Ogoja. Calabar displayed an exceptional trend as the measured TSP level does not equate its level of urbanization. PortHarcourt recorded the highest PM10 level of 181.38±50.64 g m-3 in the dry season while the minimum level in the dry season of 42.44±9.74 g m-3 in Ogoja as against the wet season maximum and minimum levels of 59.88±20.89 and 6.94±2.05 g m-3 obtained in PortHarcourt and Ogoja urban respectively. The annual mean PM10 levels ranged between 24.69±25.10-120.44±85.64 g m-3 (table-3). The dry seasonal mean level of PM2.5 ranged between 13.56±2.63-55.00±29.45 g m-3 recorded in Ogoja and Uyo urban respectively, while in the wet season the range was 1.81±1.11-12.88±3.48 g m-3 obtained in Calabar and Port Harcourt respectively. Also the annual mean PM2.5 levels ranged between 8.66±6.94-29.92±35.47 g m-3 (table-4). International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 56 Table-2 Dry and Wet seasonal mean levels of TSP (µg m-3) in the cities monitoredWeek EKET UYO CALABAR OGOJA Portharcourt Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet 1 81 25 650 82 65 22 80 25 180 160 2 93 30 800 134 83 10 76 20 201 88 3 146 35 720 100 56 15 90 30 191 94 4 87 20 625 75 90 17 72 10 186 53 5 65 21 314 71 120 25 60 16 159 59 6 82 26 290 80 130 20 55 10- 167 80 7 76 22 260 60 104 18 75 15 175 58 8 71 18 245 56 93 15 66 13 160 96 9 107 15 162 50 140 18 75 12 370 100 10 98 17 143 55 120 15 60 10 364 92 11 76 16 157 61 115 17 53 08 367 106 12 80 18 109 58 107 10 67 10 360 122 13 120 26 186 89 120 20 100 25 202 80 14 128 24 153 60 96 14 80 21 180 67 15 135 18 144 40 112 15 75 20 191 88 16 122 18 163 55 77 10 72 18 170 64 x 97.94 21.82 320.06 70.38 101.75 16.31 72.25 16.44 226.44 87.94 S 25.19 5.52 235.42 23.09 23.42 4.27 12.32 6.58 83.73 27.12 Annual mean ± Std. 59.88 ± 53.83 195.22 ± 176.55 59.03 ± 60.42 44.35 ± 39.46 157.19 ± 97.93 Table-3 Dry and Wet seasonal mean levels of PM10 (µg m-3) in the cities monitored Week EKET UYO CALABAR OGOJA PORTHARCOURT Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet 1 60 15 385 30 50 08 60 10 148 40 2 50 10 260 40 60 10 40 08 167 34 3 58 12 238 35 40 06 30 07 158 60 4 40 10 305 32 73 07 32 06 160 26 5 45 08 235 25 80 06 40 08 134 50 6 60 08 186 30 86 06 33 06 158 56 7 55 05 198 22 74 04 46 06 146 80 8 52 08 130 20 65 05 38 05 150 77 9 60 12 80 18 100 15 44 09 293 94 10 66 15 89 16 93 18 40 08 242 82 11 57 12 76 19 80 10 30 06 266 85 12 62 14 72 15 81 08 35 02 254 81 13 80 22 60 14 70 09 60 10 162 35 14 85 20 75 15 64 07 52 08 150 56 15 88 21 70 16 75 05 50 07 156 50 16 82 20 72 12 40 05 49 05 158 52 x 62.50 13.25 158.19 22.44 70.69 8.06 42.44 6.94 181.38 59.88 S 14.28 5.23 101.86 8.52 17.15 3.79 9.74 2.05 50.64 20.89 Annual mean ± Std. 37.88 ± 34.83 90.32 ± 95.99 39.38 ± 40.29 24.69 ± 25.10 120.44 ± 85.64 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 57 Table-4 Dry and Wet seasonal mean levels of PM2.5 (µg m-3) in the cities monitoredWeek EKET UYO CALABAR OGOJA PORTHARCOURT Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet 1 25 10 110 10 15 02 15 06 41 16 2 21 07 90 10 20 02 12 05 42 22 3 26 02 86 06 12 01 16 01 38 11 4 22 02 92 03 14 01 14 01 28 18 5 18 06 80 12 25 03 15 03 33 10 6 15 01 30 04 28 03 12 03 40 14 7 16 02 75 03 18 01 10 03 37 08 8 12 02 63 02 12 01 10 02 39 12 9 20 08 30 08 30 05 13 07 44 14 10 18 06 40 06 20 02 15 05 37 12 11 15 04 42 02 20 02 10 03 41 10 12 22 02 35 01 16 01 12 01 42 12 13 25 06 28 05 18 02 20 08 30 14 14 27 03 34 05 14 01 15 06 26 10 15 26 03 20 01 10 01 15 05 28 12 16 12 02 25 01 08 01 13 01 25 11 x 20.00 4.13 55.00 4.94 17.50 1.81 13.56 3.75 35.69 12.88 S 5.05 2.68 29.45 3.51 6.23 1.11 2.63 2.29 6.37 3.48 Annual mean ± Std. 12.07 ± 11.22 29.92 ± 35.47 9.66 ± 11.09 8.66 ± 6.94 24.29 ± 16.13 Table-5 Percentages of fine to coarse fractions of the suspended particulate matter Parameter EKET UYO Calabar OGOJA Portharcourt % PM10/TSP 63.25 46.99 66.01 55.67 76.62 % PM2.5/TSP 20.12 15.56 16.36 19.53 15.45 % PM2.5/PM10 31.86 33.13 24.53 35.07 20.17 The percentage of fine to coarse particle was calculated from the annual mean of the TSP, PM10 and PM2.5. Ogoja, though lowest in PM load relative to the other cities had the highest level of fine particle as can be adduced from the sum of the percentage PM2.5/TSP and PM2.5/PM10. The PM10/TSP ratio in all the cities except in Port Harcourt lies within 0.4-0.7 (40-70%) estimate of USEPA (table-5). It has been reported that the finer the particle the more hazardous as it penetrates deeper in the lower respiratory tract9, 29. The source of the fine particle in this city (Ogoja) may be transboundary as there are no industries in the city that would contribute majorly to the city’s ambient air fine particulate level. Gomez et al. reported that coarse PM comes from such anthropogenic activities like vehicular traffic, mining/quarry activities, agricultural activities etc while the fine PM comes from secondary source and from metal smelting industries. Comparatively, the levels of suspended particulate matter (SPM) in the dry season were higher than those of the wet season across the cities monitored. Furthermore, SPM levels (TSP, PM10, PM2.5) in Uyo and PortHarcourt were consistently higher than those of other cities (figures-1A, 2A and 3A). The higher PM level of Uyo relative to more urbanized PortHarcourt city may be due the various road construction works going on in the city during the monitoring campaign with its attendant dust suspension characteristics. The trend of the SPM within the dry season showed a slight elevation in the first four weeks of the campaign and a more or less dipping towards the end of the monitoring period in most of the cities with the exception of Uyo and PortHarcourt urban that showed a marked elevation within the few weeks of commencement of the campaign and at the middle of the period (figures-1B, 2B and 3B). The elevation in the first four weeks corresponds to the period of harmattan in the South-South when the ambient air SPM load is usually elevated due to the North-East trade wind laden with dust that is prevalent within this period. Early research works have observed similar SPM level elevation in the harmattan30, 31. In the wet season, the trend depicts higher levels at the beginning of the campaign and then gradual dipping due to wet precipitation as the rainy season heightens (figures-1C, 2C and 3C). International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 58 Figure-1A Variations of TSPconcentrations in Ambient Air between the dry and wet seasons across cities in South- South Nigeria Figure-1B Trend of Dry season TSP concentrations within the months of Dec. 2008 to March 2009 Figure-1C Trend of Wet season TSP concentrations within the months of June –September, 2009 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 59 Figure-2A Variations of PM10 concentrations in Ambient Air between the dry and wet seasons across cities in South-South Nigeria Figure-2B Trend of Dry season PM10 concentrations within the months of Dec. 2008 to March 2009 Figure-2C Trend of Wet season PM10 concentrations within the months of June –September, 2009 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 60 Figure-3A Variations of PM2.5 concentrations in Ambient Air between the dry and wet seasons across cities in South-South Nigeria Figure-3B Trend of Dry season PM2.5 concentrations within the months of Dec. 2008 to March 2009 Figure-3C Trend of Wet Season PM2.5 concentrations within the months of June –September, 2009 International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 61 Table-6A Analysis of variance (ANOVA) of the dry and Wet seasonal mean levels of TSP (µg m-3) data in the cities monitored Source variables Mean std.dev df SS MSE F ratio p-value Eket dry 97.94 25.186 1 17.920 17.920 10.150 0.024 Eket wet 21.81 5.516 1 11.685 11.685 6.618 0.040 Uyo dry 320.06 235.420 1 58.614 58.614 33.198 0.002 Uyo wet 70.38 23.088 1 9.686 9.686 5.486 0.036 Calabar dry 101.75 23.422 1 3.538 3.538 2.004 0.216 Calabar wet 16.31 4.270 1 0.249 0.249 0.141 0.723 Ogoja dry 72.75 12.321 1 0.093 0.093 0.052 0.828 Ogoja wet 15.81 7.626 1 0.308 0.308 0.174 0.694 Port Harcourt dry 226.44 83.730 1 3.054 3.054 1.730 0.246 Port Harcourt wet 87.94 27.123 1 0.015 0.015 0.009 0.929 Constant 1 31.910 ESS 8.828 5 8.828 Table-6B Analysis of variance (ANOVA) of the Dry and Wet seasonal mean levels of PM10 (µg m-3) data in the cities monitored Source variables Mean std.dev df SS MSE F ratio p-value Eket dry 62.50 14.283 1 3.765 3.765 5.082 0.024 Eket wet 13.25 5.235 1 1.129 1.129 1.524 0.272 Uyo dry 158.19 101.861 1 2.920 2.920 3.942 0.104 Uyo wet 22.44 8.524 1 8.752 8.752 11.814 0.018 Calabar dry 70.69 17.145 1 0.545 0.545 0.735 0.430 Calabar wet 8.06 3.785 1 0.384 0.384 0.518 0.504 Ogoja dry 42.44 9.743 1 1.545 1.545 2.085 0.208 Ogoja wet 6.94 2.048 1 0.005 0.005 0.006 0.940 Port Harcourt dry 181.38 50.644 1 1.714 1.714 2.313 0.189 Port Harcourt wet 59.88 20.893 1 4.177 4.177 5.638 0.064 Constant 1 12.957 ESS 5 3.704 Table-6C Analysis of variance (ANOVA) of the dry and wet seasonal mean levels of PM2.5 (µg m-3) in the cities monitored Source variables Mean std.dev df SS MSE F ratio p-value Eket dry 20.00 5.046 1 0.599 0.599 5.082 0.024 Eket wet 4.13 2.680 1 10.213 10.213 1.524 0.272 Uyo dry 55.00 29.448 1 59.478 59.478 3.942 0.104 Uyo wet 4.94 3.511 1 0.740 0.740 11.814 0.018 Calabar dry 17.50 6.229 1 0.002 0.002 0.735 0.430 Calabar wet 1.81 1.109 1 2.757 2.757 0.518 0.5041 Ogoja dry 13.56 2.632 1 3.108 3.108 2.085 0.208 Ogoja wet 3.75 2.295 1 1.176 1.176 0.006 0.940 Port Harcourt dry 35.69 6.374 1 11.039 11.039 2.313 0.189 Port Harcourt wet 12.88 3.481 1 6.191 6.191 5.638 0.024 Constant 1 81.198 ESS 5 6.315 The Fisher test, analysis of variance (ANOVA), for the TSP, PM10 and PM2.5 in the dry and wet seasons showed that TSP levels in the dry and wet seasons in Eket and Uyo urban were statistically significant as shown by the p-values (p0.05) (Table 6A). For the PM10, the wet season levels in Eket and Uyo were significant (p0.005) (Table 6B). The dry seasonal levels of PM2.5 in Eket and wet season concentrations in Uyo and Portharcourt were statistically significant (p0.05). The TSP, PM10 and PM2.5 concentrations obtained in this study were lower than those reported for Abakaliki urban, South-East Nigeria28 and Calabar25. The annual mean TSP in all the cities International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 62 were below the 230-250 g.m-3 WHO annual guideline limit. All the cities had annual PM10 concentrations above the WHO 20 g.m-3 annual guideline limit. In contrast, only the annual mean PM2.5 in Uyo and PortHarcourt exceeded the annual US National Ambient Air Quality Standard (NAAQS) limit of 15 g m-3Conclusion This study has provided baseline data of TSP, PM10 and PM2.5levels of the cities monitored. Comparatively, the SPM levels in Uyo and PortHarcourt were relatively higher than those of the other three cities monitored. The study concludes that within the period of the campaign, the TSP levels were within the guideline limit while levels of PM10 and PM2.5 either exceeded or were very close to the guideline limits in all the cities monitored and hence presents possible public health risk. References 1.Gomez D.R., Reich S.L., Dawidowski L.E. and Vazquez C. A., Combined Analysis to Identify Airborne PM10 Sources, J. Environ. Monit.,, 52-59 (2005)2.European Communities Commission, EC., Proposal of Council on Ambient Air Quality and Cleaner Air for Europe, 2005/0183 (COD), Brussels, 21st Sept, (2005)3.Wehner B., Birmili W., Gnauck T. and Wiedensohler A., Particlenumber size distributions in a street canyon and their transformationinto the urban-air background: Measurements and a simple model study, Atmos. Environ., 36, 2215–2223 (2002)4.Friedlander S.K., Koch W. and Main H. H., Scavenging of a coagulating fine aerosol by a coarse particle mode, J. Aerosol Sci., 22, 1–8 (1991)5.Bigg E. K., A mechanism for the formation of new particles in the atmosphere, Atmospheric research, 43, 129–137 (1997)6.Weber R.J., McMurry P.H., Mauldin III R. L., Tanner D.J., Eisele F.L., Clarke A.D. and Kapustin V. N., New particle formation in the remote troposphere: A comparison of observations at various sites, Geophys. Res. Lett., 26(3), 307–310 (1999)7.Shendell D.G. and Naeher L.P., A pilot study to assess ground level ambient air concentration of fine particles and carbon monoxide in urban Guatamala, Environment International,28, 375-382 (2002). 8.Sodhi G.S., Fundamental Concepts of Environmental Chemistry 2nd Edition, Narosa Publishing House, New Deihi, 56-65 (2005)9.Philip R.S and Graham J.J., Fine Particulate Matter National Ambient Air Quality Standards: Public Health Impact on Populations in the North Eastern United States, Environ. Health Persp., 113(9), 1140-1147 (2005) 10.Natusch D.E and Wallace J.S., Urban Aerosol Toxicity: The Influence of Particle size, Science, 186, 695 (1974)11.Pope C.A. and Dockery D.W., Health effects of fine particulate air pollution, J Air Waste Manag Assoc, 56, 709-42 (2006)12.Beelen R., Hoek G., van den Brandt P.A. and Goldbohm R.A., Long-termexposure to traffic-related air pollution and lung cancer risk, pidemiology, 19, 702-710 (2008) 13.Rosenlund M., Forastiere F. and Porta D., Trafic-related air pollution in relation to respiratory symptoms, allergic sensitisation and lung function in schoolchildren, Thorax , 64, 573-580 (2009) 14.Davidson C.I., Phalen R. and Solomon P., Airborne Particulate Matter and Human Health: A Review, Aerosol Science and Technology, 39, 737–749 (2005)15.Samet J.M., Dominic F., Currieo F.C., Coursac T and Zeagr S. Fine Particulate Air Pollution and Mortality in 29 US Cities 1987-1994, N. Engl. J. Med., 343, 1742-1749 (2000)16.Speizer F.E and Heath C.W., Particulate Air-Pollution as a Predictor of Mortality in a Prospective-Study of Us Adults, American Journal ofRespiratory and Critical Care Medicine, 151, 669-674 (1995)17.Prajapati S.K and Tripathi B.D., Seasonal variation of leaf dust accumulation and pigment content in plant species exposed to urban particulate pollution, Journal of environmental quality, 37, 865-870 (2008) 18.Kim Y.J., Lee K.W., Kim S and Ham J.S., Fine particulate characteristics and its impact on visibility impairment at two urban sites in Korea; Seoul and Incheon, Atmospheric environment,40, 5593-5605 (2006)19.EPA, Protecting visibility: An EPA report to congress, research triangle park, NC office of air quality and planning standards EPA report no, EPA-450/5-79-008 (1979)20.Ferm M., Watt J., O'Hanlon S., Santis F. De and Varotasas C., Deposition measurement of particulate matter in connection with corrosion studies, Anal.Chem. Bioanal., 384,1320-1330 (2006)21.Tuch T., Brand P., Wichmann H.E. and Heyder J., Variation of Number and Mass Concentration in Various Size Ranges of Ambient Aerosols in Eastern Germany, Atmos. Environ., 31,4293–4197 (1997)22.JICA/PAKEPA Report, Investigation of Air and Water Quality in Lahore, Rawalpindi and Islambad, (2002) International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 4(4), 54-63, April (2015) Int. Res. J. Environment Sci. International Science Congress Association 63 23.Ikamaise V., Obioh I.B., Ofoezie I.E and Akeredolu F.P., Monitoring of Total Suspended Air Particulate in the Ambient Air of Welding, Car Painting and Battery Charging Workshops in Ile-Ife, Nigeria Global, J. Pureand App. Sci., 7, 743-748 (2001) 24.Akeredolu F.P., Atmospheric Environment Problems in Nigeria: An Overview, Atmos. Environ.,23(4), 7-10 (1989)25.Abam F.I. and Unachukwu G.O., Vehicular emissions and air quality standards in Nigeria, Euro journal34(4) 550-560 (2009)26.Koku C.A. and Osuntogun B.A., Environmental impacts of road transportation in South, Western states of Nigeria, Journal of Applied Sciences, 7(16), 2536-2550 (2007)27.Efe S.I., Spatial distribution of particulate air pollution in Nigerian cities: Implication for human health, J. Environmental Health Research, 2(7), 9-13 (2008)28.Ngele S.O., Fine and total suspended particulate matter in ambient air of Abakaliki, Journal of Chemical Society of Nigeria (JCSN), 34(2), 24-30 (2009)29.Pope A.C., Epidemiology of Fine Particulate Air Pollution and Human Health: Biologic Mechanism and who,s at Risk, Environ. Health Perspect.,108, 713-723 (2000) 30.Remoundaki E., Papayannis A., Kassomenos P., Mantas E., Kokkalis P. and Tsezos M., Influence of Saharan Dust transport events on PM2.5 concentrations and composition over Athens, Water, Air Soil Poll., 224, 1373-1379 (2013)31.Pope A.C., Epidemiology of Fine Particulate Air Pollution and Human Health: Biological Mechanism and who,s at Risk, Environ. Health Perspect.,108,713-723 (2000)