LEAD IN THE NIGERIAN ENVIRONMENT: PROBLEMS AND PROSPECTS

 

M. K. C. Sridhar*, J. F. Olawuyi, L. A. Adogame, I. R. Okekearu, C. O. Osajie,

and Linda Aborkar

Division of Environmental Health, College of Medicine,

University of Ibadan, Ibadan, Nigeria

*mkcsridhar@skannet.com

 

Abstract

Lead levels in outdoor and indoor environment of two populous cities in Nigeria, Ibadan and Lagos were measured. Samples of surface and ground waters, soils, dust, and various foods consumed by communities were collected from (a) selected communities representing high, medium and low density areas, (b) automobile service stations, and (c) heavy traffic areas. Communities’ perceptions on the lead and health effects were also recorded. The results indicated that the levels of lead in drinking waters varied between 0.004–1.98 mg/l. Ground waters showed the highest levels (up to 2.16 mg/l). The lead levels in soils varied depending on the location: residential areas, 140.0– 5454.6 mg/Kg and 81.91–4060.7 mg/Kg in mechanic’s villages where automobiles are serviced. The commonly eaten foods in the communities contained 0.0-18.5 mg/Kg.  The level of knowledge on the lead and health impacts is rather poor among the various communities. The communities living in the high-risk areas complained of headache, fatigue, muscular weakness and sleeplessness.  Some of the high-risk areas were noted.

 

Introduction

Lead is a well known pervasive chemical and is known for its toxicity. The major environmental sources of metallic lead and its salts are paint, auto exhaust, food, and water.  For children, the most important pathways of lead exposure are ingestion of chips from lead-painted surfaces, inhalation of lead from automobile emissions, food from lead soldered, plumbing, and medications in the form of folk remedies.  The main source of adult human exposure is food, which is believed to account for over 60% of blood levels; air inhalation accounts for approximately 30% and water of 10% (John et al, 1991).  Automobile emissions have been an important source of lead exposure for urban residents, particularly in areas with congested traffic. The lead from dust in automobile emissions is being deposited in soils and other ecosystems (Mombeshora et al, 1981). Once mobile in the environment, it finds way into the body through drinking water, food and air like many other toxic elements. Lead is a cumulative poison whose effects include damage to the brain and central nervous system but symptoms may not appear until after several years of exposure. Nriagu (1979) assessed childhood lead poisoning in selected African cities particularly among the populations in urban, rural and mining areas. The concentrations in the atmosphere were reported to reach 0.5 to 3.0 ΅g/m3 and >100 mg/g in soils. Available information on its levels in the Nigerian environment and effects on populations is not documented adequately. This paper describes assessment of lead levels in two populous cities, Lagos and Ibadan, in Nigeria and the perceptions of the commuity members to lead poisoning.

 

 

Methodology

Study Areas and Sampling. Lagos City is the capital of Lagos State and has a population of over 10 million. Being the former capital of Nigeria, it enjoys a unique position with respect to trade and commerce, and also the centre for various diplomatic missions and maritime activities. It has an estimated area of 3577 Km2 and has 13 Local Government Areas in the main City area .  Ibadan City is located near the forest-grassland boundary of  South-western Nigeria at a distance some 145 kilometres North East of Lagos.  It is the capital of Oyo-State of Nigeria. It has an estimated population of 3.5 million from the projections. The total area of the city is approximately as 103.8 Km2.  The Ibadan Region is made up of 11 Local Government areas. Both cities have the unique characteristic of three distinctive socio-economic groups living in defined areas, viz. high density (HD), medium density (MD) and low density (LD) areas.

 

Samples of surface and ground water, dust, soil and foods were collected from each of these areas. The samples were collected both from indoor and outdoor environments. In Lagos, Agege (HD), Ilupeju (MD) and Ikeja Government Reserved Area (LD) were selected and from Ibadan, Foko, Oje, Apata, Bere and Oke-Ado areas (HD), Oke-Bola and Eleyele areas (MD), and Agodi Reservation, University of Ibadan Campus, and Bodija Estate (LD) areas were selected for sampling. A sampling frame was prepared for each of the locations and various samples were collected. The number of samples ranged from 4 to 15 depending on the location and availability. They were analyzed for lead using Alpha 4 Chem Tech Analytical Atomic Absorption Spectrophotometer along with other physico-chemical parameters (pH, water quality parameters, soil characteristics) as described in standard methods (USEPA, 1989; APHA, 1998). A questionnaire survey and Focal Group discussions were used for community perception on lead poisoning.

 

Results and Discussion

The results of analysis of various environmental samples are given in Table 1. The levels of lead in various water sources indicate that majority of the waters showed lead levels higher than the WHO permissible level of 0.01 mg/l. The tap waters from medium and low density areas recorded relatively higher levels. Waters from low density areas in Ibadan recorded higher lead levels. However, the ground waters from the high density areas in both the cities showed significantly higher lead levels. 

 

Soils from the residential areas showed higher lead levels in Lagos more than in Ibadan. Similarly, the soils around the mechanic villages where automobiles are serviced showed significantly higher levels of lead in Ibadan than in Lagos. This observation is interesting in that the topography of Lagos is flat with poor drainage system and water logging during rainy season.  Ibadan, however, enjoys well-maintained drainage and slopes and valleys, which promote good drainage, characterize the topography. The dust collected during the dry weather showed lead levels ranging from 19.5 to 192.2 and the highest levels are recorded in the high density areas. Foods collected from Ibadan showed higher lead levels though they were within the permissible limits. These foods are generally ready to eat and are exposed to dust, smoke and fumes on the roadside during vending.

 

Regarding the indoor environment, people in Lagos though enjoy regular tap water supply, the lead levels are significantly high (maximum 1.2 mg/l). In Ibadan, the source  is mostly ground water and occasionally tap water. The water is stored generally in storage tanks made of mild steel, plastic or any available container which may range from disused paint cans, buckets or clay pots in high density areas. Way of handling is unhygienic. Populations in Lagos live in highly congested areas characterized by ill-planned road network and heavy vehicular traffic. This is further confirmed from the dust, which showed significantly higher levels of lead. Further evidence on the lead levels of indoor foods cooked also shows that in Lagos the levels are higher as compared to Ibadan. The general health problems perceived by the communities in high risk exposure areas are headache, irritation, constipation / abdominal problems, general fatigue, tremors and restlessness. The level of awareness on the sources of lead and its health effects is very poor among most of the communities (5.3 to 18.75 per cent) and those in high density areas knew the least

 

Conclusions

Data available on lead levels in Nigeria is rather scanty. This study is an attempt to  summarize various ongoing researches from our Laboratory. Nigeria is one of the petroleum exporting countries and use of automobiles by middle and high income groups is rather high. The Nigerian petroleum contains >0.45 g/l lead as per the Nigerian Industrial Standards (NIS 116:1981). However, the levels also exceed 0.5g/l in certain brands (Friends of the Environment, 1998). Vehicular emissions are not checked. Federal Ministry of Environment is currently trying to phase out lead in petroleum products and introduce emission control measures. There is also the need to collect more scientific data on the lead levels in the environment, its exposure routes and health effects.

 

References

American Public Health Association (1998), Standard Methods for the Examination of

Water and Wastewater, 18th Edition, Washington, DC, USA.

Friends of the Environment (1998), Vehicular emission and Lead Poisoning in Nigeria,

Proceedings of a Workshop, Edited by A. A. Falomo and C. C. Chikwendu, Lagos, pp. 1-88

John, H; Cheryl, H; Richard, S and Christine, S. (1991). Toxics: A to Z - A guide to

Everyday Pollution Hazards, University of California Press, Berkeley,  Los Angeles,  Oxford   pp.47-104.

Mombeshora, C., Osibanjo, O. and  Ajayi, S.O (1981).Pollution Studies on Nigerian

Rivers. Toxic heavy  metals status on surface waters in Ibadan-city.  Environmental International, Vol.5, pp.49-53.

Nriagu, J.O (ed.) (1978). The Biogeochemistry of Lead in the Environment, Part A.

Elsevier/North- Holland Biomedical Press, Amsterdam.

Sridhar, M. K. C. and Okekearu, I. R. (1998), Exposure to Indoor Lead in Lagos

Metropolois: A Nigerian Experience, Epidemiology, USA, Vol. 10, No.4, p.227

USEPA (1989), Description and Sampling of Contaminated Soils – A Field Pocket Guide

by United States EPA: 625/12-91/002, pp.1-98

 

 

 

Table 1 Lead Levels in Various Samples in Lagos and Ibadan Environment

(Results expressed as ranges)

 

 

 

Environmental Sample

 

Outdoor Environment

 

Indoor Environment

Area

    High Density     Medium Density    Low Density

 

Area

    High Density     Medium Density    Low Density

 

Lagos City

Waters, mg/l

    Tap

    Surface

    Ground

        Water

Soils, mg/Kg

    Residential

 

    Mechanics

         Area

 

Dust, mg/Kg

 

Foods, mg/Kg

   

Ibadan City

Waters, mg/l

    Tap

    Surface

    Ground

        water

Soils, mg/Kg

     Residences

     Mechanics

              Area

Dust, mg/Kg

Foods, mg/Kg

 

 

 

0.004 –0.48   0.0 – 0.003     0.14 – 1.48

          NA               NA               NA

 

0.25 – 1.02    0.001 – 0.009       NA

 

400.5 –           351.1 -            191.49 -

   5454.6          3087.8          1723.4

112.6 –            81.91 –             81.91 --

982.9             522.2                409.56

   

     NA                  NA                  NA

 

0.02 – 25.6    0.01 – 10.0      0.002 -

                                                 7.3

 

 

0.02 – 0.94    0.01 – 1.98   0.01 – 1.8   

0.02 – 0.79    1.08 – 1.44   0.02 –0.94

 

1.23 – 2.16    0.01 – 1.23   0.02 –1.44

 

263.2-491.2   140.0-403.5 193.0-491.2

767.8-2129.3     265.2-3918.2  296.9- 

                                               4060.7

85.7–192.2     19.5-105.2  19.5-132.5

 0.0-15.1          0.0-8.6        0.0- 8.6

 

 

 

0.14 – 0.47     0.002 – 0.15   0.03 – 1.2

          NA             NA                NA

 

0.15 – 0.35           NA                NA

 

           NA             NA               NA

 

            NA             NA               NA

 

 

0.19 – 388.9   18.5 – 259.3    10.25 –   

                                                 215.0  

           NA       0.2 – 20.2        0.06 --

                                                  18.5

 

 

0.01-0.09*  0.0009 – 0.09*  0.05 - 0.14*

         NA                 NA              NA

 

           *                     *                  *

 

          NA                  NA              NA

          NA                  NA              NA

 

 57.9-115.8    19.3-279.85    65.6 – 77.2

 0.38-10.38      0.03--6.85     0.04 -6.63

Water sold by Vendors in nylon sachets showed lead levels in the range of 0.04 to 0.7 mg/l in both Lagos and Ibadan;  NA = Samples Not Available

* = Water from indoor storage pots; the source was mostly from tap and occasionally from ground water