An Assessment of Effective Temperature, Relative Strain Index and Dew Point Temperature Over Southwest Nigeria

The study of human comfort has generated interests across the world, because comfort often forms the basis for planning for housing, healthcare and recreation facilities [1,2]. Knowledge of the thermal comfort ensures adequate warning for future extreme climate scenarios and for adequate preparation of humans and their livelihood against extreme climate conditions [3].

The developing countries have been reported to be characterized by increasing population but relatively poor social infrastructural facilities to cope with extreme climate effects. While many studies have been carried out in temperate region and in developed countries, only a few studies have been done in many developing countries, including Nigeria [4,5].

Human thermal comfort is an expression of feeling of satisfaction with the prevailing weather condition [6,7]. Extreme climate conditions outside the comfort zone are conditions of heat and cold stresses. Stressful climatic conditions are known to decrease work productivity, and increase (heat-related) mortality or morbidity [3,8-10]. Thermal stresses in tropical environment are often associated with increased heat and cold stress, and are typically described in terms of too high or too low humidity, temperatures and in excess of certain thermal thresholds [5,11-13]. Thermal thresholds are usually in terms of unitary (temperature, humidity and other heat related climatic elements) and integrative indices [14].

Abuloye [15] modified a list of human thermal comfort indices by De Freitas and Grigorieva [14], and listed 82 integrative indices, out of which only three (Effective Temperature (ET), Relative Strain (RS) and Temperature Humidity Indices (THI)) have been extensively reported on Nigeria [3,4]. These previous studies have shown that the results from ET and THI are not significantly different for Nigeria, and that ET is more suitable for the country. In addition, the studies indicated that, since Nigeria is a large country (with a population of more than 140 million spread over an area of 923 800 km2), each of the geographical regions deserve to be studied for variability in the thermal climate.

The south-western part of Nigeria is known as the most populated and industrialised within the country, especially as it is the location for the second most populated (Lagos), and second and third largest city in Africa (Ibadan and Ogbomosho, respectively). Studies on the south-western region have focused on the temporal changes in the temperature and relative humidity [12,16-20], and existing studies with regional focus is scarce to find.

In addition, each of these studies has focused on one settlement or another in the region, and relatively dated. Furthermore, published studies informing about the perception of residents of the region (and Nigeria, in general) to thermal comfort have only focused on the people in tertiary schools [21], and the perceptions of the people in either the rural or urban areas in this region are less reported. Studies on adaptation of humans to stressful thermal climatic conditions have nevertheless suggested that adaptive methods (which may be anticipatory or reactive; behavioural, physiological or psychological) can vary over space, and can inform about the coping capability of the people with climate change [22].

Subsequently, information presented in this study is aimed at enhancing policy issues on peoples’ preparedness to extreme climatic conditions in the region. Specific objectives are to determine the spatial and temporal variations in the thermal conditions over the south-western Nigeria; and examine the adaptive methods of the residents of two purposively selected settlements for coping with extreme weather conditions in the region.

This study is presented as a case study for regional study of thermal comfort in developing countries. Indices evaluated for thermal conditions in this study are Effective Temperature (ET), Relative Strain Index (RSI) and Dew Point temperature (Td), based on previous studies that showed that they are relevant to tropical climates. Although the Td is not a comfort index, it is a measure of humidity, and this also has significant implication for thermal stress [23]. The ET and RSI are also not state-of-the-art indicators because they do not take into consideration the effects of radiation and wind velocity, which are heat elements [7].

However, studies on the regional climate with respect to the indices and humidity are few, and the results from the traditional indices will provide a control for the understanding of the more state-of-the-art indices in the area.

The southwest of Nigeria lies between 2°3'-6° E and 6°2'-8°4' N (Figure 1), and is characterised by the tropical rainforest in the south and tropical guinea savanna in the north. The climate of region is strongly influenced by the moisture-laden tropical maritime (mT) and dust-laden tropical continental (cT) air masses [24].

Figure 1: Map of Nigeria, showing the location of the states that make up the southwest region.

The southern sub-region is characterized by a general low relief (0-200 m above sea level), and rises gently northwards to the area of crystalline rocks where inselbergs (981 m) rise abruptly above the surrounding plains [25]. In the urban centres, construction of roads, buildings, factories, manufacturing plants, bridges and culverts, farmlands and others have reduced drainage channels and erosion passages and or diverted the natural courses of others [26].

The population of the region, as at 2006 was over 36 million, and was projected to be about 183 million in 2015, and about 433 million by 2050. The total land area is about 166,361 km [27].

Previous studies showed evidence of regional difference in the climate of Nigeria, as typical of large countries, including India, United States of America and China [13,21,28].

Data used for this study include the monthly temperature and relative humidity records for all the 10 synoptic stations (with the records from 1960 onwards) in the region (Figure 2) [29]. The data were obtained from the office of the Nigerian Meteorological Agency’s office at Oshodi, Lagos. Data were examined for spurious values and evidence of non-climatic heterogeneity and instrumental errors as advised by the World Meteorological Organisation (1989).

Figure 2: Selected meteorological stations and settlements for the perception study.

The thermal comfort indices (ET, RSI and Td) were derived from the temperature and corresponding relative humidity data using equations i–iii [11,28] (for ET); Giles (for RSI); Wolkoff and Kjargaard [10] (for RSI)):

(1)

(2a)

(2b)

(2c)

(3)

Where ET: Effective Temperature, Hrh: Relative Humidity, RSI: Relative Strain Index, Vp: Vapour Pressure (hPa), Td: Dewpoint Temperature, T: Air Temperature, RH: Relative Humidity, e: Actual Vapour Pressure.

The mean and variations of the elements and indices were computed for 1961-1990, 1991-2010 and 1961-2010, and descriptive maps were produced with the moving average interpolation statistics in geographic information systems, for the periods. For the generation of comfort map for the study area, comfortable region for Td, RSI and ET were 17.5–23°C [23], 0.1–0.2 [30] and 18.9–25.6°C [11,31]. Areas outside these thresholds were mapped as discomfort zone in the study.

In addition, responses of residents of two purposively (based on convenience and relatively small size, and significant dichotomy across different landuse areas) selected settlements (Ile-Ife, a medium-size University town, and Eruwa, a semi-rural settlement in the region) were elicited with a semi structured questionnaire (Appendix). These settlements also represent locations in the two (tropical rainforest and guinea savanna) main ecological zones in the regions (Figure 2). In each settlement, occupants of every third building in a street) were sampled in identified residential, industrial (e.g. sawmills and a metal scrapping and smelting firm in Ile-Ife) and commercial (markets) areas in each settlement. In all, 501 (321 and 180, in Ile-Ife and Eruwa, respectively) copies of questionnaire, which represents the responses of about 0.5% of the entire population of the two communities were returned after two weeks of administration by ten field personnel. Most of the copies of questionnaire for the residential areas were administered in the evening and weekends, because most respondents were not often in the house in the other periods (Table 1).

Table 1: Demographic and socio-economic characteristics of the respondents.

Regional pattern of temperature and thermal variables

Mean variations, trends and change in 1960-1990 and 1991-2013 means: The summary statistics for the 50 (1961–2010) year mean monthly temperatures (minimum, average and maximum) and those of ET, RSI and Td at all the selected stations are presented in Tables 2 and 3, respectively. Minimum temperature over the region varied between 21.1 and 22.9°C while maximum temperature varied between 30.9 and 32.2°C; mean temperature was from 26.2 to 28.1°C. Dewpoint temperature values that varied from 21.3 to 24.4°C while RSI values ranged from 0.09 to 0.15 (no unit). The ET values were between 24.6 and 26.7°C. The temporal variations in the temperature variables were generally below 10%. Furthermore, whilst Akure (a medium-size administrative city in the region) exhibited decreasing trend in all the temperature variables, other stations exhibited increasing trends in minimum (except Ibadan and Ikeja) and maximum (except Ilorin and Lokoja) over the years. Correspondingly, relative humidity has increased in Akure, and Saki. Comparison of the 1961–1990 and 1991– 2010 values of the temperature variables indicated significant (p ≤ 0.05) increase (though with small 30-year average in most cases) at most stations (except Ilorin for mean and minimum temperature, Benin for maximum, Lokoja and Osogbo, for the mean temperature). Relative humidity also significantly reduced at most stations, except at Saki, Lokoja and Akure (p ≥ 0.05).

Table 2: Mean, range, variation, trend (change of values over time) and temporal variations in temperature variables over selected station in southwest Nigeria (1961-2010).

Table 3: Mean, range, variation, trend (change of values over time) and temporal variations in effective temperature, relative strain index and dewpoint temperature over selected station in southwest Nigeria (1961-2010).

The patterns of temporal change in RS, Td and ET were different across the stations. Whereas the Td trend at most of the stations showed significant increase between the 1961–1990 and 1991–2010 values (except at Akure, Benin and Ilorin, where it significantly decreased, or Ondo and Saki, where changes in Td was not significant), RSI significantly reduced at most of the stations (except Saki, where it has significantly increased and other stations, where such variation was not significant). Significant 1960–1990 and 1991–2013 change occurred in the values of ET at all but the Ibadan station, and such trend of change was negative for most stations (except Abeokuta, Ikeja and Saki) (Table 3).

Descriptive thermal maps for the region: The results of the moving average interpolation of the thermal climate variables investigated in this study are presented as Figures 3-6. Minimum temperature appears to decrease as one move away from the coastal areas, whereas maximum temperature was slightly higher around Lokoja than the other parts of the region. Except for the area around Abeokuta, where both minimum and maximum temperatures were higher than most part of the surroundings, maximum temperature tend to vary inversely with minimum temperature over the region (Figure 3). Both Td and ET were also higher around Abeokuta–Ikeja axis and Benin in the south than the settlements in the other part of the southwestern Nigeria while the RSI interpolation showed lower values in the inner settlements (Osogbo–Ondo-Akure –Ilorin axis) of the region than the other parts (Figure 3d-3f). Furthermore, whereas the values of minimum and mean temperature around the Ikeja and Lokoja axes have generally increased by 1°C, in 1991-2010 period, when compared to the 1961-1990 means, there was a decrease in the maximum temperature, also, by about 1°C around Lokoja in 1991-2010 period (Figure 4). In addition, Td and ET interpolations over the study area exhibited an increase of at about 1°C, over the coastal region of the Atlantic Ocean, and a converse decrease by 1°N in the northern subregion. The RSI unit was also lower around the northern part in the 1991-2010 periods (Figure 5).

Figure 3: 50 (1961–2010)–year Average temperature (minimum, maximum and mean), relative strain index, effective temperature and dewpoint temperature over the southwest Nigeria. The cross indicates the location of the meteorological station whose data were interpolated.

Figure 4: Variation in the minimum, mean and maximum temperature over the southwest Nigeria in 1961-1990 and 1991– 2010 years periods. The cross indicates the location of the meteorological station whose data were interpolated.

Figure 5: Variation in the effective temperature index, relative strain index and dewpoint temperature over southwest Nigeria in 1961-1990 and 1991–2010 years periods. The cross indicates the location of the meteorological station whose data were interpolated.

Assessment of the Td, RSI and ET over the study area with the recommended thresholds of 17.5–23°C, 0.1–0.2 and 18.9–25.6°C, respectively, showed that areas further into the interior of the region are more thermally comfortable than the coastal region, especially with respect to Td and ET but RSI results describes the entire region as thermally comfortable, however (Figure 6).

Figure 6: Computed variations in dewpoint temperature and effective temperature index for 1961-1990, 1991–2010 and 1961– 2010 means. The relative strain index is not presented because the entire region was homogenously classified as comfortable in the study period.

When compared across the 1961-1990 and 1991-2010 periods, the results of the interpolation indicate that whereas thermal discomfort has aggravated in more areas in the western sub-region of the study area, the thermal condition in eastern region has improved in the 1991-2010, than the preceding 30-year period (Figure 6).

Perception of residents of selected settlements on comfortable weather condition

Characteristics of respondents: Over 94% of the respondents in both settlements have had at least primary education and were able to understand the content of the questionnaire and its purpose. The entire sampled population at Eruwa were aged above 30 years and majority of the respondents from Ile Ife were at least 18 years. About 81% of the respondents were employed and made at least N20, 000 ($100) monthly while more than 70% have dependants, and worked for a minimum of 5 h daily. In addition, majority of the respondents work indoor (55.3% and 76.1% respectively in Ile Ife and Eruwa) and under shade, if outdoor (35.4 and 18.9%, respectively) (Table 1).

Coping strategies to extreme weather conditions in the southwest Nigeria: Concerns were raised over heat stress in the study area. At least 80% of the respondents at both the settlements of Eruwa and Ile- Ife considered the time between 0800 and 1200 Nigerian Local Standard Time (LST) as comfortable, and the periods between 1200 and 1800 LST as thermally uncomfortable. The period between 1800 and 2100 LST was also considered as comfortable by about 70% of the respondents. There was no significant (p ≤ 0.05) difference in the perceptions of the different categories of residents (those outdoor, undershade, outdoor without shade, and indoor) at the periods.

Coping strategies, however, varied among the different the majority of people in the two locations (Ile-Ife and Eruwa). Whilst the first three coping preferences at Ile-Ife were cloth/wear type, (ii) installation of fan and (iii) installation of air conditioners at home and offices, the most important preferences at Eruwa (in order of importance) were (ii) opening of ventilation for cross ventilation, (i) changing changing of cloth or wear type, and (iii) sleeping outside the house (outdoor) at certain times of the night or day (Figure 7).

Figure 7: Distribution of prominent coping strategies to thermal stress in the selected settlements in Southwest Nigeria.

A number of recent studies have focused on the thermal comfort of Nigeria, probably because of the increased awareness on climate change and its effects on the people and their livelihoods [32-36]. Nigeria is a typical developing country where people have been noted to be vulnerable to the effects of extreme climatic conditions because of poor economic, political and technological responses [2,37,38]. Studies have noted that many sub-Saharan countries are vulnerable to conditions of livelihoods (e.g., food insecurity, water scarcity and environmental degradation) due to the intensive effects of climaterelated causes, including decortication, desertification and temperature increase [39].

In Nigeria, our previous studies [4,21], among others have indicated that human comfort in the southwest Nigeria may be under heat stress in the recent years, but we could not determine the certainty of the stretch of the vulnerable area in the region, since the studies-like majority of other previous studies from other sources-have been based on smaller, country-wide scale. In the present larger, regional-scale study, the southern (coastal) settlements- consisting of the areas around Benin, Abeokuta, Ikeja, Ondo and Ibadan, which are mainly traditional large cities in the southwest Nigeria, are characterized by heat stress, as typical of many large cities, globally [40-42]. A major difference between the countries in developing and developed economies is however the reaction to the increasing thermal discomfort. Whilst in the southwest Nigeria, the common mitigating/ coping strategies to heat stress are personal adjustments (changing personal variables, such as clothing, moving to a different location, etc.), and few instances of technological or environmental adjustments (e.g., opening or closing windows or shades, turning on of fans and/or air conditioners, especially among economically buoyant populations), approaches for coping strategies in many developed countries have developed into policy issues, early warning system and speedy responses. Metcalf et al. [43], for example, noted the development of urban greening as a social movement in New York whereas the few capital cities (e.g., Ikeja and Akure) that promote urban greening in Nigeria do it for aesthetic justification. Again, while studies have reported the adoption of early warning system on impending heat stress in north-eastern North America [3], cases of heat stress are still rarely reported in Nigerian hospitals. In our study area, majority of respondents argued that effects of climatic discomfort are ‘not-lifethreatening’, and do not require reporting in hospitals. Nonetheless, heat stress has been linked with violence, heat stroke, rashes and meningitis among people [9,44,45].

Furthermore, this study has shown an increase in temperature by about 1°C in the southwest Nigeria between 1960–1990 and 1991– 2013. Temperature increase in the southwest Nigeria may be associated with increased urbanization, transportation and industrial activities in the region, especially with its role as the commercial and industrial hub of the country. Recent studies have reported massive industrial plans for the area, but these plans are often unassociated with a parallel policy on impact assessment and mitigation [46,47]. For example, Oketola and Osibanjo noted that rapid and haphazard industrialization has taken place in part of the southwest Nigeria without environmental considerations, and that pollution abatement technologies are largely absent. Earlier, Hettige et al. [48] has also indicated that many developing countries (including Nigeria) lack the necessary information to set priorities, strategies, and action plans on environmental protection issues. Studies have also linked urbanization and associated activities with development of urban heat islands in some major cities in the region [20,32]. Also, studies have shown that a number of heat-related mortality cases have been reported in Nigeria and neighboring countries [49,50]. Similarly, concerns for sustainable development have increased, globally with the post Kyoto Protocol assessments that indicate the increased culpability of developing countries to contribute to global warming.

The study showed that there was significant increase in temperature and selected indices of thermal comfort at most studied stations in 1991-2013 over 1960-1990, and that while the thermal variables have increased, relative humidity exhibited significant decrease. It also showed that resident’s coping strategies were mainly of personal adjustment, with few cases of environmental adjustments in urban settlements, or among economically buoyant population. Subsequently, there is need for policy re-drive in the region towards sustainable urbanization and development, and with concerns for the impact of many developmental actions on the humans.

1. De Freitas C (2003) Tourism climatology: evaluating environmental information for decision making and business planning in the recreation and tourism sector. Int J Biometeorol 48: 45-54.
2. World Health Organisation (WHO) (2011) Regional consultation on health of the urban, Proceedings of the 2010 Regional consultation of Mumbai, India, Regional Office for South East Asia, UNFPA, pp: 82.
3. Kalkstein LS, Smoyer KE (1993) The impact of climate change on human health: some international implications. Experientia 49: 969-979.
4. Eludoyin OM, Adelekan IO (2013) The physiological climate of Nigeria. Int J Biometeorol 57: 241-264.
5. Eludoyin OM, Adelekan IO, Webster R, Eludoyin AO (2014) Air temperature, relative humidity, climate regionalization and thermal comfort of Nigeria. Int J Climatol 34: 2000-2018.
6. Lee DH (1953) Physiological climatology as a field of study, Annals of the Association of American Geographers 43: 127-137.
7. Terjung W (1967) The geographical application of some selected physio-climatic indices to Africa. Int J Biometeorol 11: 5-19.
8. Havenith G, Holmer I, Parsons KC (2002) Personal factors in thermal comfort assessment; clothing properties and metabolic heat production. In Energy Building 34: 581-591.
9. Alcamo J, Moreno JM, Novaky B, Bindi M, Corobov R, et al. (2007) Europe, climate change 2007: impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.
10. Wolkoff P, Kjargaard SK (2007) The dichotomy of relative humidity on indoor air quality. Environ Int 33: 850-857.
11. Ayoade JO (1978) Spatial and seasonal patterns of physiologic comfort in Nigeria. Arch Met Geoph Biokl B 26: 319-337.
12. Olaniran OJ (1982) The physiological climate of Ilorin, Nigeria. Arch Met Geoph Biocl 31: 287-299.
13. Candido C, Dear RJ, Lamberts R, Bitterncourt L (2010) Air movement acceptability limits and thermal comfort in Brazil’s hot humid climate zone. Build Environ 45: 222-229.
14. De Freitas CR, Grigorieva EA (2015) A comprehensive catalogue and classification of human thermal climate indices. Int J Biometeorol 59: 109-120.
15. Abuloye AP (2015) Assessment of variations in thermal climate and response to thermal stress in some parts of the southwest Nigeria, Unpublished M.Sc. thesis, Obafemi Awolowo University, Ile-Ife, Nigeria.
16. Omogbai BE (1985) Aspects of Urban Climate of Benin City, Nigeria. Atmos Clim Sci 4: 241-252.
17. Adebayo YR (1987) A note on the effect of urbanization on temperature in Ibadan. J Climatol 7: 185-192.
18. Adebayo YR (1991) Heat island in a humid tropical city and its relationship with potential evaporation. Theor Appl Climatol 43: 12-26.
19. Aina SA (1989) Aspects of the Urban Climate of Oshogbo, Unpublished M.Sc Dissertation, University of Ibadan, Nigeria.
20. Akinbode OM, Eludoyin AO, Fasae OA (2008) Temperature and relative humidity distributions in a medium-size administrative town in Southwest Nigeria. J Environ Manag 87: 95-105.
21. Eludoyin OM (2015) Assessment of daytime physiologic comfort, its perception and coping strategies among people in tertiary institutions in Nigeria. Weather and Climate Extremes 10: 70-84.
22. De Dear R, Brager G, Cooper D (1997) Developing an Adaptive Model of Thermal Comfort and Preference. Final report of ASHRAE RP-884.
23. Lawrence MG (2005) The relationship between relative humidity and the dewpoint temperature in moist air: A simple conversion and applications. Bul American Meteorol Soci 86: 225-233.
24. Omogbai BE (2010) Rain days and their predictability in south-western region of Nigeria J Hum Ecol 31: 185-195.
25. Ileoje NP (2001) A New Geography of Nigeria, New Revised Edition. Longman Publishers: Ibadan, Nigeria.
26. Oyinloye RO, Oloukoi J (2012) Spatio-temporal assessment and mapping of the land use/land cover dynamics in the central forest belt of Southwestern Nigeria. Res J Environ Earth Sci 4: 720-730.
27. National Population commission (NPC) (2006) National population census, Abuja, Nigeria.
28. Gregorczuk M, Cena K (1967) Distribution of effective temperature over the surface of the earth. Int J Biometeorol 11: 145-149.
29. Aderinto SA (2006) Implication of Automatic Weather Observing Stations in Nigerian Meteorological Agency, Unpublished IMO report.
30. Balafoutis CJ, Makrogiannis TJ (2003) Hourly discomfort conditions in the city of Thessaloniki (North Greece) estimated by the relative strain index (RSI), pp: 1-5.
31. Kyle WJ (1994) The human bioclimate of Hong Kong. In: Brazdil R, Kolar M (eds.) Contemporary Climatology, Masaryk University, Brno, Czech Republic pp: 345-350.
32. Ayanlade A, Jegede OO (2015) Evaluation of the intensity of the daytime surface urban heat island: how can remote sensing help? Int J Image Data Fusion 6: 348-365.
33. Ayanlade A (2016) Seasonality in the daytime and night-time intensity of land surface temperature in a tropical city area. Sci Total Environ 557: 415-424.
34. Mirrahimi S, Mohamed MF, Haw LC, Ibrahim NLN, Yusoff WFM, et al. (2016) The effect of building envelope on the thermal comfort and energy saving for high-rise buildings in hot-humid climate. Renewable and Sustainable Energy Reviews 53: 1508-1519.
35. Igbawua T, Zhang J, Chang Q, Yao F (2016) Vegetation dynamics in relation with climate over Nigeria from 1982 to 2011. Environ Earth Sci 75: 1-16.
36. Ilesanmi AO (2016) Doctoral research on architecture in Nigeria: Exploring domains, extending boundaries. Front Architect Res 5: 134-142.
37. United Nations International Strategy for Disaster Reduction Regional Office for Africa (UNISDR) (2012) Disaster Reduction in Africa, Special Issue on drought.
38. Pezzoli A, Santos Dávila JL, d’Elia E (2016) Climate and Human Health: Relations, Projections, and Future Implementations. Climate 4: 18.
39. Lawson ET (2016) Negotiating stakeholder participation in the Ghana national climate change policy. Int J Clim Change Strat Manag 8.
40. Algeciras JAR, Consuegra LG, Matzarakis A (2016) Spatial-temporal study on the effects of urban street configurations on human thermal comfort in the world heritage city of Camagüey-Cuba. Build Environ 101: 85-101.
41. Yang YE, Wi S, Ray PA, Brown CM, Khalil AF (2016) The future nexus of the Brahmaputra River Basin: Climate, water, energy and food trajectories. Glob Environ Change 37: 16-30.
42. Baklanov A, Molina LT, Gauss M (2016) Megacities, air quality and climate. Atmos Environ 126: 235-249.
43. Metcalf SS, Svendsen ES, Knigge L, Wang H, Palmer HD, et al. (2016) Urban Greening as a Social Movement, In Urban Sustainability: Policy and Praxis pp: 233-248.
44. Mohammed I, Nasidi A, Alkali AS, Garbati MA, Ajayi-Obe EK, et al. (2000) A severe epidemic of meningococcal meningitis in Nigeria. Tran R Soc Trop Med Hyg 94: 265-270.
45. Lin T, Ho T, Wang Y (2011) Mortality risk associated with temperature and prolonged temperature extremes in elderly populations in Taiwan. Environ Res 111: 1156-1163.
46. Oketola AA, Osibanjo O (2009) Estimating sectoral pollution load in Lagos by Industrial Pollution Projection System (IPPS): Employment versus output. Toxicol Environ Chem 91: 799-818.
47. Ajayi DD (2007) Recent trends and patterns in Nigeria’s industrial development. Afr Dev 32.
48. Hettige H, Martin P, Singh M, Wheeler D (1994) IPPS-The Industrial Pollution Projection System, World Bank, Policy Research Working Paper.
49. Greenwood B (2006) Editorial: 100 years of epidemic meningitis in West Africa-has anything changed? Trop Med Int Health 11: 773-780.
50. Sawa BA and Buhari B (2011) Temperature variability and outbreak of meningitis and measles in Zaria, northern Nigeria. Res J Applied Sci Eng Technol 3: 399-402.