Blood-Lead levels among Inhabitants of Enyigba Lead-Zinc Mining Community of Ebonyi State, Nigeria: Indications of Occupational and Environmental Health Hazards

Bello H Tilako1, Fred C Otuu2*, Bassey E Bassey3 and Elvis N Shu4

Nigeria

Tel: +234 703 245 4222; Email: fred.otuu@unn.edu.ng community in Ebonyi State, Nigeria.

Introduction

With the discovery and exploration of solid minerals in Abakaliki division of the old Eastern Nigeria, in the nineteen-forties, artisanal mining activities have become a significant occupation among the inhabitants, to the extent that virtually every household within the mining area is involved in artisanal mining. This has affected the environment of the mining areas negatively, as heaps of mining tails are scattered everywhere, and lead-zinc metals are heaped in most households, exposing the inhabitants to metal pollution. Studies so far on the impacts of mining in Abakaliki lead-zinc mining area have focused mainly on water, soil, and plant metal loads and their speculative health and environmental impacts [1, 2, 3, 4]. The impact of lead-zinc mining on plant physiology, anatomy and biochemistry are also available in local and international literatures [5, 6, 7, 8]. However, there is scarcity of literature on the impacts of lead-zinc mining activities on the specific health status of inhabitants of the mining environment.

Many serious health concerns may arise from the uptake of heavy metal contaminated food or water. A decrease in immunological defenses, intra-uterine growth retardation, impaired psycho-social behavior, and disabilities associated with mal-nutrition are some of the many health concerns [9]. The disease burden imposed by mining pollution affects children greatly and over 70 percent of these children face hazardous conditions [10]. Children, who are more vulnerable to the impacts of heavy metals, tend to have higher exposures and generally account for the majority of deaths and diseases associated with mass poisoning incidents from the mining operations. Studies have documented that children involved in mining have higher exposures to mercury, lead, and other metals and suffer severe lead and mercury intoxication [10]. Lead-zinc mining has assumed significant occupation in Enyigba community such that even children of preschool age are also involved directly when they are strapped on their mothers’ backs during mining or indirectly when they are exposed to the mining heaps in the household.

The heavy metals such as zinc, copper, cadmium, iron, selenium, cobalt, nickel, arsenic and mercury tend to have very high enrichment factor and slow clearance rate [11]. The accumulation of these heavy metals in sediments and water is a major health concern because of the removal of such metals by plants and the resultant exposure of human and animal life to the elevated metals through the food chain. However, because of the illegal nature of artisanal mining, there is a need for research to assess the severity of environmental and occupational problems resulting from their activities. Such studies will serve to show the magnitude of the problems, indicate likely initiatives required to arrest arising potential and associated environmental and social conflicts, and provide cognitive basis for informed intervention policies by government.

Fred C Otuu, et al. Blood-Lead levels among Inhabitants of Enyigba Lead-Zinc Mining Community of Ebonyi State, Nigeria: Indications of Occupational and Environmental Health Hazards. Adv Clin Toxicol 2019, 4(3): 000162.

There is extensive evidence that measures of body- lead burden are associated with lead levels in environmental media [12, 13]. Three of the measures of body-lead burden reported in the literature are bone-lead content, blood-lead concentration, and erythrocyte protoporphyrin (EP) blood concentration. Bone-lead levels are considered to be reflective of cumulative exposure to lead, but their determination is currently either expensive or invasive. More importantly, the accuracy and representativeness of bone-lead concentrations measured externally by x-ray fluorescence (XRF) instrument has been questioned by researchers [14]. Blood-lead and EP levels can be more readily measured, but reflect a varying mixture of long-term and more recent exposures [15, 16, 17]. Despite the complex interaction of prior and current exposures, evident in measured blood-lead concentrations, they are still the measure of choice for most studies of intervention effectiveness. There is a body of literature relating blood- lead concentrations to specific health outcomes stemming from lead exposure, though much of it examined children with levels of exposure usually indicative of lead poisoning [12]. Blood-lead concentration is associated with environmental lead exposure and linked to health outcomes. In this study, blood-lead levels were used as indices of environmental/occupational exposure to lead contamination.

Results

Copyright© Fred C Otuu, et al.

Table 3 presents the awareness of occupational hazards and safety measure utilization of the subjects. Majority of the 89 occupationally exposed subjects (69.67%) were not aware of the hazards associated with their job and as a result, only 22 (24.72%) used personal protective devices. Among the 22 who agreed subjects to have been using protective devices, only 13.64% used them regularly? Safety boots (50.10%) were reported as the commonly used protective devices by the subjects.

Fred C Otuu, et al. Blood-Lead levels among Inhabitants of Enyigba Lead-Zinc Mining Community of Ebonyi State, Nigeria: Indications of Occupational and Environmental Health Hazards. Adv Clin Toxicol 2019, 4(3): 000162.

Copyright© Fred C Otuu, et al.

Table 4 represents self-reported occupational health problems among subjects. Most of the subjects (74.40%) reported that they had headache followed by itching (53.93%) and dizziness (40.45%)

Table 5 represents blood-lead levels of the inhabitants in the study and control areas. The subjects who were occupationally-exposed to lead contamination had mean blood-lead levels of 42.30µg/dl, while the environmentally-exposed had average subject’s blood- lead levels of 28.67µg/dl. Both values were significantly higher (p<0.0001) than the control value (4.76µg/dl) and the WHO recommended maximum exposure level of 10µg/dl. The blood lead levels of the occupationally- exposed individuals were also significantly higher (p<0.0001) than that of the environmentally exposed subjects.

Discussion

This study investigated the blood-lead levels of one hundred and fifty (150) subjects of Enyigba lead-zinc Fred C Otuu, et al. Blood-Lead levels among Inhabitants of Enyigba Lead-Zinc Mining Community of Ebonyi State, Nigeria: Indications of Occupational and Environmental Health Hazards. Adv Clin Toxicol 2019, 4(3): 000162.

mining community who voluntarily participated in the study. The participants were grouped into occupationally and environmentally exposed subjects. The occupationally exposed subjects were those who were involved in lead-zinc mining activities as a significant source of income. The environmentally exposed subjects were those who were not involved in the mining activities but were exposed to lead contamination through environmental media such as soil, air and water, and environmental components such as foods and household storage facilities, because they live within the mining community. The awareness of the hazards associated with the lead-zinc mining activities and the necessary safety measures against the occupational hazards were also investigated. The difference in blood-lead levels among the occupationally exposed in comparison with the environmentally exposed was used as an evidence of occupational hazards associated with the lead-zinc mining activities in Enyigba.

The result of the demography showed that male were actively involved in the lead-zinc mining activities, probably more involved than women, because the population of the male subjects (56.18%) was higher than women (43.82%). This could be explained from the fact that lead-zinc mining activities have become major occupations second only to farming activities in the lead- zinc mining communities of Abakaliki18. In most communities of Ebonyi state, subsistence farming is a common practice with men. With the recognition of the economic value inherent in artisanal lead-zinc mining, the gradual shift from agricultural dominated economic base to mixed economic base, the emergence of artisanal men miners is a strong possibility. The sieving of stream sediments and sorting of lead from the mining tails seem attractive and fitting to more men than women. The absence of divorcées among the subjects presupposed strong marriage bond. This could also favor women participation in the mining activities as some of the men are polygamous, a culture commonly found in Abakaliki rural communities. Polygamy is culturally accepted among rural agricultural communities since it means more helping hands to the husbands in their farms.

Ebonyi State in general is considered an educationally disadvantaged State among the south-eastern States. This accounts for the greater number of subjects with secondary education (55.06%). The few subjects (3.37%) with tertiary education were not entirely indigenes of the community, as some were civil servants (teachers, construction workers) whose involvements with lead-zinc mining were pastime.

Copyright© Fred C Otuu, et al.

The storage of the mining products in the house was a common feature with the miners (96.63%) and environmentally exposed (80.333%). This could be explained by the fact that most of the subjects (69.67%) had no awareness of the hazards associated with lead contamination through dietary and environmental exposures. The lack of hazard awareness could also be attributed to inadequate education. In the present educational standard ravaging the national educational system, primary school education is close to illiteracy. The greater use of safety boots by the subjects (50.10%) might not be for safety against lead contamination, but rather for protection against sharp objects (stones, gravels, thistles) piercing the feet. This argument could be supported by the fact that many of the subjects agreed to have been using safety boots in their regular farming activities, especially during the rainy season. Some of the self-reported occupational health problems among the subjects were also those associated with lead contamination and activities involving weight lifting, long hours of bending down and stooping low.

There was a significant differences (p<0.0001) in the blood-lead levels of the occupationally and environmentally exposed respondents. The subjects who were occupationally exposed were also environmentally exposed, accounting for relatively higher mean blood-lead levels (42.30µg/dl) than the environmentally exposed (28.67µg/dl).

In general the blood levels of both groups were higher than the control group (4.76µg/dl) and also higher than the WHO recommended maximum exposure level of 10 ug/dl [22]. This observation poses a public health problem realizing the implication of lead contamination in a myriad of diseases. Lead, Zinc and Cadmium have been implicated in a number of diseases owing to their roles in creation of oxidative stress with the associated morphological distortion and biochemical disruption [23]. The destruction of sensitive thiol groups by metal interaction may negatively affect the protein folding/ or binding of apoenzymes by cofactors, resulting in deformation of the normal biological activity of the proteins [24]. Lead, like some other heavy metals can participate in catalytic reactions, known as Fenton-type reactions that produce Reactive Oxygen Species (ROS), setting the cell under an oxidative stress which may result in DNA damage, destructions of lipids and proteins through a wide range of biochemical routes [25]. Lead and other heavy metal species may also get into cells through various transport routes, or penetrate the cellular membrane to bind to lipophilic carrier. This Fred C Otuu, et al. Blood-Lead levels among Inhabitants of Enyigba Lead-Zinc Mining Community of Ebonyi State, Nigeria: Indications of Occupational and Environmental Health Hazards. Adv Clin Toxicol 2019, 4(3): 000162.

transporter-mediated uptake of toxic heavy metals interferes with the normal transport of essential substrates, resulting in competitive inhibition of the transport process necessary for nutrient normal haemostatic processes. Significantly, transportation of heavy metals across the membrane barriers may require acquisition of energy from the proton motive force or ATP pool, interrupting the role of ATP in cellular metabolism. This underlies the many metabolic diseases traceable to heavy metal intoxication [26].

Occupational and environmental exposures continue to be a serious global problem, especially in developing or rapidly industrializing countries [27]. This is in line with the present study where crude artisanal mining activities characterized by unregulated disposal of mining tails, lack of awareness of safety measures and ignorance of health effects of lead contamination have resulted in the high blood-lead levels among the sampled subjects. Developing country populations, especially children, may have higher levels of lead exposure due to unregulated industrial emission and car emission of leaded petrol; less stringent environmental and occupational health safety regulation, and cottage (domestic) industries such as metal polishing and smelters [28]. In view of the increasing participation of households in lead mining activities in the Enyigba community and persistence of lead in the environment, the issue of lead contamination is likely to remain a significant public health issue in the study area.

In Abakiliki lead-zinc mining communities, outdoor environmental pollution plays a significant role in indoor lead exposure. The ignorance of the miners (adults and children) of lead contamination through work-clothes, implements, and storage has contributed to extraneous lead contamination of the house-hold from the field [29]. Breaking the chain-flow of lead from the field to the home through holistic education will minimize the quantity of house-hold lead, thereby reducing environmental exposure of non-miners, especially children and aged ones in the household.

Acknowledgment

Authors acknowledged the assistance of the community leaders who made it possible for peaceful community entry to be achieved.

Conflict of Interest

None

Copyright© Fred C Otuu, et al.