A. F. Oluwole

Air pollution in a large tropical city with a high traffic density — results of measurements in Lagos, Nigeria

Abstract The joint project, ‘Environmental Monitoring and Impact Assessment in Nigeria’ consisted of universities from Nigeria, Germany and Great Britain, and was funded by the European Union. Within the context of this project, an air monitoring station was purchased and placed in Lagos, the former capital of Nigeria. In addition to these permanent measurements, single samples were taken at different places in Lagos. A northern wind, the so-called Harmattan, transports much dust from the Sahara. But most of the identified air pollution in Lagos is caused by the traffic which can even be recognized without measurements, by strong turbidity, bad smell and eye irritation. This pollution is caused by the combination of many strongly emitting vehicles and frequent traffic jams. Diesel vehicles emit plumes of black smoke consisting of soot. Many petrol engined cars exhaust blue smoke which is caused by unburnt oil; market places are established especially around bus stops, and many people are exposed to unhealthily high concentrations of aromatic hydrocarbons, CO and particles. The results of measurements at such places are presented here. The measured CO values, for instance, often exceed the limits set by WHO guidelines. These initial results show that drastic measures are necessary to protect the population against this high pollution. The measured benzene concentrations cause a raised carcinogenic risk.

Trace elements in drinking and groundwater samples in southern Nigeria.

The levels of Al, Sn, Cs, Rb, Sr, Br, Cr, Mo, Co, Ba, Cu, Zn, Cd, Pb, Mn, Se, As, V and Ni were determined in drinking water supplies (public taps, domestic taps and treated water from public water sources) and groundwater supplies (boreholes and shallow wells) in some parts of Southern Nigeria. The water samples were analysed using inductively coupled plasma mass-spectrometry (ICP-MS). The mean levels (microgram/l) of all the elements ranged between 0.35 microgram/l for Cs and 87.3 micrograms/l for Zn in the drinking waters and between 0.54 microgram/l for Co and 420.3 micrograms/l for Ba in the groundwaters. A comparison of the elemental concentrations with WHO guidelines showed that with the exception of violations of Cd, Cr and Se limits in some of the drinking water samples, the levels of all the other elements investigated were below the WHO maximum allowable concentrations.

Traffic pollution: preliminary elemental characterisation of roadside dust in Lagos, Nigeria

Roadside dust collected from different parts of Lagos metropolis were analysed for heavy metals and other trace elements using a combination of instrumental neutron activation analysis (INAA), inductively coupled plasma-optical emission spectrometry (ICP-OES), and flame atomic absorption spectrometry (FAAS). The results show a positive correlation of the concentration of Pb and some other vehicular emission-related elements with the traffic density. Automotive emission was also found to be the main contributor to Pb concentration in the roadside dust but some elements which hitherto have been linked with automotive emission, such as cadmium and nickel, did not show any strong correlation with traffic density.

The atmospheric deposition of major, minor and trace elements within and around three cement factories

Total atmospheric deposits of particulate matter within the premises of three Nigerian cement factories were collected and characterised for about 25 elements using a combination of Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF) and Instrumental Neutron Activation Analysis (NAA). Some toxic heavy metals like As, Pb, Ni, Co, Zn, Cu, Cr, as well as S, Ca, P were found to be highly enriched in the neighbourhood compared to the control sites. Deposition rates of the cement marker element, Ca, decreased exponentially with increasing distance from the factories.

Neutron activation analysis of Nigerian crude oils

A total of 40 crude oils from 10 different oil fields in Nigeria were analysed for 39 elements by Instrumental Neutron Activation Analysis (INAA). Significant correlations were found between Ni and V concentrations and Ni versus Se concentrations. The American Petroleum Institute (API) gravities are inversely correlated with total transition metal concentration of the oils but there is no obvious correlation of the V/Ni ratio with the age of the oil fields. The oils are very similar to North Alaska Type B oils in key transition metal parameters and cluster analysis results using the transition metals as variables indicate that the oils might have been formed from two closely related sources.

Environmental impact of vehicular traffic in Nigeria: health aspects

Blood lead levels were analysed and pulmonary function tests were performed on Nigerian traffic wardens, comprising sixty from Lagos (ages 24-52 years; 27 +/- 6), thirteen from the sparsely populated university town of Ile-Ife (ages 22-40 years; 27 +/- 8) and a control group of twenty-four subjects (age 19-55 years; 31 +/- 8). Perkin-Elmer Zeeman 3030/HGA 600 AAS was used for blood analysis. The mean lead level in Lagos wardens was 18.1 +/- 6.4 micrograms/dl, which was significantly higher than the level of 10.2 +/- 2.7 micrograms/dl in Ife wardens and 12.9 +/- 7.0 micrograms/dl obtained in the controls (P < 0.001). However, there was no significant difference between the levels of blood lead in Ife traffic wardens and normal controls. Significant differences (P < 0.0005) in spirometric measurements--peak flow rate (PEFR), forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC)--were observed between traffic wardens and control subjects. The noise levels measured along traffic roads exceeded the threshold for hearing damage.

Urban and rural fuelwood situation in the tropical rain-forest area of south-west Nigeria

Our study describes a 1995 survey (1120 questionnaires) in the urban and rural rain-forests of Ile-Ife, Osun State, Nigeria, on fuel use for cooking. We assessed the biofuel burning in Africa, in particular, and in tropical countries, in general. Included are discussions of socio-economic conditions, descriptions of the types and numbers of stoves, fuel and combustion characteristics, specific fuel consumption in both the private and commercial sectors, fuel sources and their availability, and health effects caused by cooking with firewood. We determined the weights and/or dimensions of fuel units, wood residues, fireplaces and combustion chambers. The consumptions of firewood (in kgcap−1yr−1) obtained by this method are of 515 in urban areas and 573 in rural areas. Wood usage is greater for low-income groups than for better situated householders who utilize kerosene, liquid petroleum gas (LPG), and electricity for cooking. Agricultural residues are used to start and support wood combustion; animal residues are not used as cooking fuels.

Effects of cement production on the elemental composition of soils in the neighborhood of two cement factories

The effects of cement production on the elemental composition of soils in the neighborhood of two cement factories in Nigeria have been investigated using the XRF and PIXE/RBS techniques. The concentration of 21 elements viz:-Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Pb, As, Zr, Rb and Br, were determined in about 30 samples. Calcium, P, S, Cr, Ni, Cu and Zn, were found to be relatively enriched in the soils of the cement factory premises. Calcium, a cement marker element, was found to be well correlated with Mg, S, Fe, Ni and Cu in the soils, and inversely proportional to the Si and Ti concentrations. From Ca/Si ratios and enrichment factors of the marker elements, it was found that soil contamination due to cement drops sharply with distance from the factories, and with increasing depth from the surface.

Elemental Composition of Head Hair and Fingernails of Some Nigerian Subjects

In this article, we present the elemental concentrations determined by INAA for 30 elements measured in some or all head hair samples of 100 Nigerian subjects and 20 elements in the fingernails of some of the same subjects. Measurements of the skewness of the distribution of each element in both tissues confirm previous reports that many tend toward a log-normal distribution. Thus, their concentrations in the tissues may not be under any homeostatic control. The ranges of elemental concentrations together with the medians, and the arithmetic and geometric means, with their respective standard deviations are presented and compared with literature values for other populations. Correlations between elements detected in hair are also sought.

Analysis of suspended air particulates along some motorways in Nigeria by PIXE and EDXRF

Elemental concentrations of air particulates collected by a gravimetric method were determined using proton induced X-ray emission (PIXE) and energy dispersive X-ray fluorescence (EDXRF) analytical techniques. Air particulate samples were collected over a six-month period at three positions (middle and two opposite sides) across a road at different locations. Total suspended particulate (TSP) matter concentrations were between 100 and 2000 μg/m3 in Lagos and between 120 and 720 μg/m3 at Ile-Ife; traffic densities were 1000–10000 vehicles per hour and 450–1500 vehicles per hour respectively. Preliminary results show that Pb, Br and Zn were highly enriched relative to the Earths crust and the Pb concentration exceeded the threshold limit value (TLV) prescribed by the Nigerian Federal Environmental Protection Agency (FEPA) for over 50% of the sampling times. Furthermore, the lead to bromine ratios in both cities were found to be within the range of those emanating from vehicular exhaust (i.e. 2.57).