Friday, 31 January 2020

Assessing air pollution associated with mines in Zambia.

Zambia has been predominantly a mining country and the copper industry has dominated the mining landscape for more than eight decades since the first commercial mine was opened in the early 1900s. To date, the mining sector is still the major foreign exchange earner for the country and the increase in the mining activities in the last decade has seen an increase in the sector's contribution to Gross Domestic Product from around 8% in 2000 to 11% in 2011, employing over 50,000 people. Zambia plays an important role in the global mining industry and the country contains the largest known reserves of copper in Africa, holding 6% of known copper reserves in the world. Zambia's mining sector has continued to register strong performance over the last decade with growth averaging 11% per annum. At present, five companies own holding of about 80% of all copper output and these are Swiss (Glencore Limited, majority owners of Mopani Cooper Mine), Canadian (First Quantum Minerals Limited,  majority owners of Kansanshi Mine, and Barrick Gold owners of Lumwana Mines Plc), Indian (Vedanta, majority owners of Konkola Copper Mine),  and Chinese (NFC Africa). According to the Zambia extractive industries transparency initiative report, covering the 2015 fiscal year, there were more than 30 companies operating in Zambia who provided information on their contribution to the Government of the Republic of Zambia's revenues arising from the extractive industrial activities. Besides, copper, Zambia is endowed with mineral wealth that includes cobalt, gold, nickel, lead, silver, uranium, zinc and numerous precious and semi-precious stones. These minerals are dotted all over the country, although mining activities are predominantly found on the Copperbelt and North-Western Provinces. The copper mine operations on the Copperbelt have had a history of poor environmental management from inception. The poor environmental stewardship has continued irrespective of whether the mining companies were privately or public owned. Over the years, sadly, this environmental mismanagement has compromised the health of the local people, vegetation, animals and has led to the destruction of infrastructure. According to some recent studies, there are three prominent environmental problems arising from the mining operations namely sulphur dioxide (SO₂) and particulate matter emission from smelters, heavy–metal effluents released into water streams and rivers and siltation of local rivers and water bodies.

In a paper published in the journal Heliyon in September 2019, Phenny Mwaanga of the Africa Centre of Excellence in Sustainable Mining, and the Department of Environmental Engineering at Copperbelt University, Mathews Silondwa of the Department of Occupational Safety and Health Services at rhe Zambian Ministry of Labour and Social Services, George Kasali of the Department of Environmental Engineering and Department of Biological Sciences at Copperbelt University, and Paul Banda, also of the Department of Environmental Engineering at Copperbelt University, review the current knowledge of air pollution (sulphur dioxide and particulat matter) associated with the mining industry in Zambia.

GIS map showing location of study area. Mwaanga et al. (2019).

Mine air pollution in Zambia, which is largely due to SO₂ and particulate matter, both fine and ultrafine, has been a topical issue since commercial mining started in the 1920s in the Copperbelt region of Zambia. However, very few studies have been undertaken to chronicle the extent of damage to the environment and harm to human health. The studies showing extent of widespread pollution have been undertaken in the recent past. For instance, in 2000, the Air Pollution Information Network for Africa conducted a study to ascertain the levels of air pollution in Zambia. The results of this study showed that the highest total emissions in Zambia where course particulate emissions of 406.8 kilotonnes per year accounted for 35% of the total emissions that year. This was followed by sulphur dioxide at 359.6 kilotonnes per year, accounting for 31%, while fine particulate matter, ammonia and nitrous oxides were at 252.7 kilotonnes per year, 75.8 kilotonnes per year and 72.8 kilotonnes per year, respectively. An audit report from the Office of the Auditor General on mine operations revealed that SO₂ and particulate matter emissions for most of the 5 large scale mines with smelters and other discharge licences were outside the national set limits by between 155% to 111% higher than the Zambia Environmental Management Agency standard during the 2013 reporting year.

SO₂ is the most critical air pollutant that continues to be emitted from the mining companies. The main source of SO₂ pollution from the Zambian mines is from the roasting and refining of copper bearing sulphide ores, chalcopyrite (CuFeS₂). The first stage in most processes is roasting or smelting the ore in air which oxidizes some of the copper and produces SO₂. The increase in SO₂ emissions has always been observed to increase at the same rate as copper production, primarily due to old smelting processes that are inefficient.

However, in the last two decades, partly as a result of pressure from international non-governmental organisations and banks and the strengthening of the implementation of air pollution legislation by Zambia Environmental Management Agency, serious efforts by mining companies in modernising their smelters has led to significant reduction in SO₂ emissions. For instance, 4 of the 5 major mining companies in Zambia that have a holding of 80% copper output have modern smelters with improved efficiency of SO₂ capture.

Whilst there is some noticeable improvement in the reduction in SO₂ emissions, the control of particulate pollutants from mining environments especially fine and ultrafine particulte matter still remain a major concern. Particulate matter can be classified as coarse (2.5-10 μm aerodynamic diameter), fine (0.1-2.5 μm aerodynamic diameter) and ultrafine ( less than 0.1 μm aerodynamic diameter). Fine and ultrafine particulate matter are produced by combustion that include motor vehicles and power plants, whereas course particulate matter is generated by mechanical processes that produce fugitive dusts from non-combustive sources. All production oriented mining operations such as cutting, breaking, crushing, drilling, grinding or abrasive blasting contribute to fine particulate matter generation, while tailings dump sites are responsible for the emission of coarse particulate matter. Other pollutants such as nitrous oxides and carbon monoxide, including secondary pollutants like ozone are generated from mining related activities. However, the impacts of these pollutants are not as significant on the local communities as that of SO₂ and particulate matter, whose impacts are quite evident on the Copperbelt Province.

Air pollution from the Mufulira Mine. Mwaanga et al. (2019).

Considering the long period of mining on the Copperbelt it is important to look at the historical background to mine air pollution and control efforts. From the beginning of large scale commercial mining in 1928 on the Copperbelt, the mines with smelters received protection from the law against liability as they were indemnified from liability through Smoke Damage (prohibition) Act of 1935. This act declared smelter areas like Nkana, Luanshya and Mufulira Mine areas as Smoke Areas. So during the colonial times under the British rule the mine operators were thus not liable for any damage to human health and property as a result of air pollution from these smelters. Therefore, there was no incentive to control the emissions but rather a licence to pollute.

Upon Zambia getting independence and nationalization of the private mines, this law still remained on the statute books of law. The then government-owned Zambia Consolidated Copper Mines also enjoyed indemnity from liability resulting from air pollution. When Zambia returned to multi-party democracy and the liberization of the economy in the 1990s, the Smoke Damage Act was found to be repugnant and was thus repealed in 1996.

However, during privatization of the mines in the late 1990s-2000 the spirit of the Smoke Damage Act found its way in the development agreements, as the new investors sought indemnity for acquiring and operating polluting mine operations for the so called stability period, in which period the government or its agencies will not take any action to enforce or penalize the new owners of the mines for any pollution during the stability period. During this period the mines environmental management was only regulated within the scope of their approved Environmental Management Plans.

Studies elsewhere have revealed that air pollution can have devastating effects on human health. According to the World Bank, urban air pollution is estimated to cause 250,000 deaths and millions of cases of respiratory illnesses every year. Other studies have shown that toxicological data collected worldwide suggests that human fatalities can arise from short-term exposure to atmospheric SO₂ levels in excess of 1000 μg/m³. Such levels were common in Copperbelt, especially in the mining towns of Kitwe and Mufulira.

The Zambia Environmental Outlook Report 3, indicated that the major source of SO₂ was from industrial processing which contributed 346 700 tonnes per year, accounting for 98% of the total emission and these were mainly from metal processing, mostly copper smelting. Another study measured the concentration of SO₂ from the converters and the smelter in Chambishi and the results showed a concentration of 1402 μg/m³ and 369 μg/m³ SO₂ from the converters and the smelter, respectively. Furthermore, this study also showed that the levels of SO₂ in ambient air, several kilometers from emission sources still exceeded the permissible Zambian annual ambient value of 50 μg/m³ by between 2–3 orders of magnitude.

The Occupational Health and Safety Institute of Zambia is a statutory body in the Ministry of Health, mandated to carry out occupational medical surveillance, occupational hygiene and occupational health and safety research in the Zambian mines and miners with particular emphasis on silicosis, tuberculosis and silico-tuberculosis.

Silicosis has been described as a potentially fatal, irreversible, fibrotic pulmonary disease that develops subsequent to the inhalation of large amounts of silica dust over time. This has a long latency period and develops subsequent to substantial occupational exposures. It clinically presents as an acute, accelerated, or chronic disease.

Few studies have been done on silicosis prevalence in Zambia. A study carried out by the Occupational Health and Safety Institute of Zambia in 1962 undertook the first published descriptive epidemiological study of Zambian copper miners, and reported a low silicosis incidence (less than 0.5%.) However, thiss analysis lacked age stratification of the cohort. By the early 1970s, this weakness was obvious to Occupational Health and Safety Institute scientists who corrected it by reporting age stratified silicosis risk that showed a prevalence of 5% in older in-service miners.

A retrospective study published in 2012 reviewed 476 randomly selected records of Zambian former copper mineworkers who underwent medical examinations at the Occupational Health and Safety Institute for the period of 1st January 2004 to 31st December 2008. The results showed a silicosis prevalence of 8.8%. The silicotics were found to have worked in the mining industry for a median 26 years while the non-silicotics' median service stood at 21 years.

Tuberculosis, though typically not restricted to miners, presents another disease burden in Zambia that has been associated with exposure to respirable silica dust in underground mines. Silica-related tuberculosis has become a menace among silicosis-afflicted mineworkers. An examination of medical records of 2114 Zambian miners for the period 1945 to 2002. It was found that 22.7% had silicosis, 65.4% had tuberculosis, while 11.9% suffered from silico-tuberculosis. Another analysis of data from the Occupational Health and Safety Institute of a sample of copper miners carried out in 2016 revealed that the average incidence rate of bacteriologically confirmed pulmonary tuberculosis within the Zambian mines for the period 1994–2014 was 658 per 100 000 persons. It was also found that the Copperbelt Province, a region with the highest concentration of mines in Zambia, had a notification rate of 415 per 100 000 people in 2013, which was more than 10-fold the national tuberculosis notification rate.

Human exposure to air pollutants from mining and ore processing operations can also occur through the food chain. A study published in 2014 found substantial chemical contamination of the surface of leaves of cassava (second staple crop after maize in Zambia) grown near the smelters located in the Copperbelt region of Zambia. The leaves of cassava cultivated in the immediate vicinity of smelters were found covered with tiny particles of dust that contained potentially toxic levels of heavy metals. The presence of these metals in the fallout dust was confirmed when their concentrations in washed and unwashed cassava leaves were compared. Overall, using the highest tolerable weekly ingestion limits established by the Joint FAO/WHO Expert Committee on Food Additives, this study concluded that dietary exposure to metals through the consumption of uncooked cassava leaves and tubers posed a moderate hazard to human health. It was further noted that as the surfaces of leaves were strongly contaminated by metalliferous dust in the polluted areas of the Copperbelt, there was still a potential hazard of ingesting dangerous levels of copper, lead and arsenic if dishes were prepared with poorly washed foliage.

Another lesson that has been learnt from the legacy of mining in Zambia is the fact that human exposure to toxicants can persist for decades, long after the closure of mining operations at any given locality. This situation pertains to Kabwe town, the provincial capital of Zambia's Central Province that has had a long history of open-pit lead and zinc  mining. The mine opened in 1902 and ceased operations in 1994. Apart from lead and zinc, cadmium was produced as a byproduct of processing zinc-containing ores. A study published in 2018 analysed lead and cadmium concentrations in blood, feces and urine of children from three townships near the abandoned lead-zinc mine in Kabwe. They found that faecal lead levels of up to 2252 mg/kg, dry weight, and urine lead levels of up to 2914 mg/litre, which is considered extremely high. An earlier study of the same townships and children in Kabwe, was found that all the 246 sampled children exhibited indications of lead poisoning, with blood lead levels exceeding the 50 μg  per litre, above the ‘level of concern’ set by Centers for Disease Control. The mean blood lead level was 594 μg per litre for all the sampled children, with a range of 54–4278 μg per litre. Children living in townships which were close to and in the direction of the prevailing winds from the abandoned mine dumps recorded the highest concentrations of metals in their bodies. Therefore, polluted dust was the main exposure route for the affected townships. The study described the above-stated levels of lead and cadmium in children as alarming and prescribed immediate medical intervention for the affected children.

The study of lead poisoning in Kabwe has also been extended to terrestrial wildlife, in the form of small wild mammals. Analysis of the lead and other heavy metal concentrations in soil and wild Rat (Rattus sp.) samples collected from around the abandoned lead and zinc mine in Kabwe and Lusaka (the capital city of Zambia). Lusaka served as the control as it was not a mining town. The results revealed that concentrations of lead, zinc, copper, cadmium, and arsenic in Kabwe soils were much higher than those for Lusaka and that metal concentrations dropped off with distance in all directions from the abandoned mine.

Of particular interest was the finding that both liver and kidney from Rats in Kabwe had significantly higher lead concentrations than those from Lusaka, indicating that polluted soil caused metal accumulation in wild Rats.

It is also evident that the levels of lead in Kabwe Rats exceeded the histopathological threshold of 2.5 mg per kg dry weight. Additionally; a significant negative correlation between body weight and renal lead was found, suggesting that wild Rats from Kabwe have been chronically exposed to lead, and that lead might have affected growth of these Rats. A reduction in body weight is a known typical toxic effect of lead in Rats.

The damage due to air pollution on materials is of serious concern as it affects the service life of buildings and hence the economy of the affected community. In Zambia, due to the nature of the mined copper ore, chalcopyrite, the predominant air pollutants include SO₂ and particulate matter. These anthropogenic pollutants can cause building degradation through soiling, corrosion and erosion. Although the effects of air pollution on materials may easily be seen in terms of discoloration, material loss and soiling, the structural failing and economic losses may not always be visible to everyone.

Though sulphur dioxide can fall both as wet and dry deposition, it frequently falls as dry deposition even up to 30 km of its source. Wet deposition of acids occurs when the pollutants are released into the atmosphere and react with water vapor present in clouds to form dilute acids. Besides sulphur dioxide, nitrogen dioxide and carbon dioxide can also cause damage to the materials and infrastructure.

In Copperbelt Province, sulphur dioxide emissions are chiefly responsible for the acid rain which deteriorates the houses of inhabitants in mining communities. For instance, the Kankoyo Township near the Mufulira Mine is one of the classic examples were paint on houses have been peeling off and the corrugated iron roofs are corroded by the sulphur acidity.

Roofs and paints corroded by sulphur acidity in Kankoyo. Mwaanga et al. (2019).

It was not possible to find scientific literature that directly linked air pollution in Kankoyo township of Mufulira to acid rain and the resultant damages to housing infrastructure. However, the potential or probability for acid rain occurrence could be gleaned from the historical atmospheric concentrations of sulphur dioxide recorded in the area.

Four SO₂ monitoring stations were installed by the mining company at different clinics of the residential areas of Mufulira town. This showed that the SO₂ concentrations were very high at Clinics 3 and 5, representing the townships of Kantanshi and Kankoyo respectively, which were located in the vicinity of the smelter as well as in the downwind direction of the smelter. On the other hand, the other clinics which were located further away, and either upwind of the plant (Clinic 8 in a low-density neighbourhood of Mufulira town) or not directly in the path of the dominant winds (Clinic 7 of Butondo township) recorded relatively reduced levels of SO₂.

The data further show that the SO₂ levels at Clinics 3 and 5 exceeded the annual guidelines significantly and even exceeded the daily guideline value for most of the years. Clinic 7 is located relatively far away downwind of the smelter but its SO₂ levels often exceeded the annual guideline value. It is only at Clinic 8, on the upwind side of the smelter, where the SO₂ levels were below the guideline values.

Research elsewhere has shown that ambient air pollutants can adversely impact the physiological and biochemical parameters of plants, which can lead to a reduction in the overall growth and development of some plants species. Usually the greatest effects occurs when plants are exposed to mixtures of pollutants, whose effects can even manifest at lower threshold levels at which effects for each individual pollutant cannot be detected. Thus in case of the copper mine air pollution effects, other minor pollutants such as oxides of nitrogen, including the secondary pollutant like ozone become significant as they can contribute to poor plant growth.

The particulate matter effects on the growth and development aspects of plants are dependent on the physical and chemical nature of the particulate matter. Besides, the presence of heavy metals, the pH of particulate matter can adversely affect soils making plant growth impossible.

The SO₂ emitted in the air may form acid rain especially in the rain season and this contributes to the deterioration of the soils which become unfit for farming and inhibit growth of vegetation. The effect of mine air pollution is clearly visible in the vegetation of some townships near the mine areas. For instance, the Kankoyo area in Mufulira has open spaces without vegetation and only certain shrubs and trees, such as Cactuses, Mango and Avocado are able to grow. Thus some areas of Mufulira are considered as wasteland.

Only plants resistant to air pollution are able to grow in some Mufulira townships. Mwaanga et al. (2019).

The direct cause and effect relationship between air pollution and failure of the soils in Kankoyo to support plant life, as witnessed by the residents of Kankoyo and the surrounding townships in Mufulira town, has yet to be scientifically established. However, a study published in 2014 revealed that the soils in Kankoyo Township and other surrounding areas which were located downwind of the Mufulira smelter had undergone acidification. Moreover, these soils recorded excessive amounts of metals, in the ranges of 37–8980 mg per kilogram of copper, 3–46 mg per kilogram of cobalt, up to 42 mg per kilogram of lead, and 16–83 mg per kilogram of zinc; with the lowest values corresponding to topsoil from the reference sites located at 24 km upwind from the smelter. When these soils were tested for biotoxicity, it was found that reproduction of the Worm Enchytraeus crypticus was fully inhibited in the soils with the highest copper concentration of 8980 mg per kilogram. Overall, the number of reproduced Enchytraeid Worms dropped with higher copper and cobalt concentrations. No reproduction was possible in soils with copper levels of above 5000 mg per kilogram. Additionally, the number of reproduced Enchytraeid Worms also dropped with higher sulphur levels in these soils.

Enchytraeid Worms are critical soil biome components that contribute to organic matter decomposition by fragmenting organic debris, changing its properties and structure, and regulating soil microbial processes that are vital for normal plant growth. They are, therefore, used as indicators to assess the biotoxicity or ecological health of contaminated soils.

A study that examined the extent of damage of mine air pollution to vegetation in Mufulira and noted that SO₂ emissions from the mines caused physical damages such as necrotic spot, yellowing of leaves, defoliation and die-back on trees which were closer to the emission source.

Effects of air pollution on plant species. Mwaanga et al. (2019).

Mwaanga et al.'s review has revealed the possibility of mine-derived air pollution in Zambia. The few studies that are available are not contemporary, but they have revealed the occupational and environmental effects of airborne hazard exposures associated with mining and ore-processing operations in Zambia.

In the mining workplaces, exposure to PM, in the form of silica dust, has created a pool of former and in-service silicosis-afflicted mineworkers. However, the actual prevalence or incidence rates for silicosis amongst miners are not exactly known as they change from one study to another. The reported rates are mainly based on restricted sample sizes, making it difficult to derive population-based rates. Moreover, the reported rates could substantially underestimate total silicosis cases in Zambia. This is because the Occupational Health and Safety Institute's radiological diagnosis procedures of occupational respiratory diseases have not been updated in the last 30 years and the institute reports silicosis morbidity as annual counts of silicosis cases instead of succinct silicosis parameters such as prevalence or incidence. The Occupational Health and Safety Institute has also a limitation of poor follow-up of retired miners who are usually repatriated to their distant places of origin around Zambia. These miners usually undergo socio-economic destitution due to the debilitating effects of silicosis, for which, currently, there is no cure or effective treatment available. Tuberculosis has also emerged among Zambian miners as an additional occupational disease. Tuberculosis being an airborne disease entails that enclosed areas such as mining sites with poor ventilation create favorable environments for tuberculosis transmission. The higher tuberculosis incidence rates in the mines have been attributed to higher rates of exposure to silica dust and silicosis (silicosis increases risk of tuberculosis by up to three times), the HIV/AIDS epidemic (HIV/AIDS increases risk of tuberculosis by up to ten times) and the environmental factors associated with the mines.

Mwaanga et al.'s review also shows that apart from occupational exposures, the mining industry in Zambia has subjected residents, fauna and flora of surrounding communities to environmental exposures of air-borne pollutants. The main exposure hazards are SO₂ and metal-laden particulate matter emanating from smelter emissions and wind-blown dust from both operating and abandoned tailings and mining-waste dumps.

The ambient air SO₂ and particulate matter concentrations reported in the review were in most cases above the international and Zambian permissible guideline limits. The effects of SO₂ on humans are well documented. SO₂ in high concentration with or without exercise is a respiratory irritant, provoking airflow limitation. In some studies SO₂, sulfates and acid aerosols have been associated with increased emergency visits and hospitalizations for asthma. Besides SO₂, particulate matter is another environmental issue of great concern to both the miners and the residents living near the mine sites. It has been established that elevated concentrations of particulate matter induces protective but injurious cellular response, and can cause oxidative stress in Humans. The other health impacts on particulate matter include procoagulant activity by ultrafine particles after access to the systemic circulation and the suppression of the normal defense mechanisms e.g. suppression of the alveolar macrophage functions. Exposure to ambient air pollution particulates has been associated with increased cardiopulmonary morbidity and mortality, particular in individuals with pre-existing diseases.

Both in vivo and in vitro studies of the health effects of ambient particulate matter have identified the generation of oxidative stress as one of the major mechanism by which air pollution particles exerts adverse biological effects. Among particles of different sizes, it has also been established that ultrafine particles are potentially the most dangerous due to their small size, large surface area, deep penetration and ability to be retained in lungs and content of redox – cycling organic chemicals.

Short term exposure to air pollutants is directly linked to increased morbidity, and an increase in particulate matter level by 10 μg/m³ is associated with 1.27%, 1.45% and 2.00% increase in hospital admissions for heart disease, chronic obstructive pulmonary disease, and pneumonia respectively.

In the mining towns of the Copperbelt Province, miners and residents have endlessly been exposed to elevated concentrations of SO₂ and particulate matter. residents of mining towns, particularly Mufulira, complain of an array of diseases including pulmonary tuberculosis and other respiratory complications associated with mine air pollution. Whilst these complaints were likely to be a reflection of what people have endured in these mining towns for a long time, the absence of research based evidence makes it difficult for government to take any remedial action.

When SO₂ is released into the atmosphere, it can react photochemically or catalytically with other pollutants to form sulphur trioxide (SO₃), sulphuric acid (H₂SO₄) and various sulphuric acid salts which represent the main constituents of acid precipitation, also known as acid rain. Therefore, the potential or propensity for acid rain occurrence in Mufulira town of the Copperbelt Province is quite high and cannot be ruled out, despite the absence of direct research based scientific evidence.

Acid rain speeds up the natural chemical weathering and corrosion of exposed material in a variety of ways like ferrous metals are attacked by SO₂ and rust more quickly; steel buildings, rail tracks and other structures built of iron can be adversely affected by air pollution with extensive economic losses. The corrosion rate has been shown to be about two to ten times higher in polluted urban and industrial air in India especially in the presence of high concentration of SO₂ than the countryside.

Despite the visible effects of mine air pollution on infrastructure in the Copperbelt Province, there has not been any research to quantify the quantitative silica content in dust to which miners are exposed. Furthermore, even in cases where the total dust to which miners were exposed exceeded the statutory Zambian limit of 1.75 mg/m³, little or no practical measures were taken, except providing the affected miners with 'dust masks' whose pore size could have no bearing to the dust characteristics, as no studies have ever been conducted to ascertain the physico-chemical characteristics of the mine particulate matter (dust).

In the last decade, efforts have been made by the mining companies, albeit partly due to pressure from international non-governmental organisationss and banks and partly due to the strengthening of implementation of regulation by the Zambia Environmental Management Agency, to minimize the emission of SO₂ and particulate matter from the copper smelters and converters.

For instance in 2009 the Nkana Copper Smelter which has been a source of SO₂ pollution for over six decades was closed and this has improved the quality of air in Kitwe, despite the damage caused to property and vegetation still remain unmitigated. Interviews with residents of this area bear testimony to the fact that respiratory related complaints have drastically reduced. Unfortunately, records from two hospitals, Wusakile and Sino-Zam, within the proximity of the Nkana Smelter, which would have availed documentary evidence to the nature of frequent cases related to air pollution, are not accessible.

Similarly, the Mufulira Copper Smelter which is well known for polluting the environment especially the Kankoyo Township where some areas have been declared a wasteland, has undergone some modernization and the SO₂ emissions have been reduced. The smelter upgrade project that started in 2005 was completed in 2016. In Chingola, the Nchanga Smelter is a modern facility with little known episodes of SO₂ pollution. According to the design parameters, it was expected to capture about 95% of the SO₂ and feed to the modern and fully fledged sulphuric acid plant.

Finally, both the Kansanshi Mine and the Chambishi Copper Smelters in Solwezi and Chambishi, respectively, are equally new and as such low levels of SO₂ emissions are expected. Despite the installation of new and modern smelters, it is only the stringent monitoring of SO₂ emissions at these facilities that will help avoid the age long legacy that has been endemic in the Zambian mines.

Based on the reviewed literature and the current state of mine air pollution in Zambia, Mwaanga et al. recomend further research in the follwing areas:

Critical studies on comprehensive characterization of particulate matter from the mine environments are required, as these will help in understanding the possible long and short term adverse health and ecological effects particulate matter has on the communities in the mining areas. In Mufulira and other affected regions, there is need for studies on the effects of miningderived acid rain, dust deposition on leaves and soil heavy metal contamination on plant/crop growth and related abiotic and biotic processes in the soil. These ecological impact assessments must include the identification of resistant species that may have the potential for bioremediation of metal-contaminated soils or sites.

Though silicosis is an occupational health issue in the Zambian miners, there is need for research to understand its influence on pulmonary tuberculosis and establish the link between silicosis, Tuberculosis cases and the prevalence of HIV/AIDS among Zambian miners. Surveillance/monitoring and epidemiological studies covering retired and inservice miners are required for determining the actual prevalence rates of mining-related illnesses and diseases in Zambia and the appropriate interventions for control, prevention and compensation.

The current occupational exposure limits in Zambia do not take into account the silica content in the ore dust. This situation suggest that many miners maybe exposed to levels of total respirable dust and
respirable crystalline silica that are higher than Occupational Safety and Health Administration Personal Exposure Limit for respirable dust containing crystalline silica. There is need for research to establish the relationship between silica exposure and silicosis occurrence in miners. In this regard, it is imperative that national institutions, mandated to regulate, monitor and screen miners for silica exposure and silicosis prevalence, acquire contemporary state of the art equipment and attain international certification for both personnel and laboratories. This responsibility should be shared with mining firms in Zambia. Data from these monitoring and screening activities should be analysed to set appropriate occupational personal exposure limits and supporting policies and legal instruments.

Health risk assessments and epidemiological studies in mining towns are required to determine the mining-related environmental air pollution exposure levels, sources, routes and risk factors, so that interventions could be developed to protect human and ecosystem health in the affected communities. In the mining-based air-borne hazard hotspots of Kabwe and Mufulira towns, it is necessary to conduct prospective and retrospective longitudinal cohort studies to establish the short- and long-term health impacts and the socioeconomic implications of environmental exposure to mining-related air pollution.

Mining companies and the mandated regulatory institutions must institute intervention research to determine the efficiency and efficacy of air-borne hazard control technologies and other measures employed in protecting the health of miners.

Research on the effects of current and past air pollution on agricultural productivity and costs in affected areas of the mining towns requires attention.

Baseline scientific investigation using Remote Sensing and GIS Tools to confirm the absence of environmental degradation (land cover and land use changes) and human health issues prior to mining activities in Zambia.

Despite the paucity of data on the extent of the impacts of mine air pollution in Zambia, its effects are visible particularly on vegetation and infrastructure. In some towns of the Copperbelt, for instance, Mufulira, the impact there is so severe that an area like Kankoyo Township has been declared a 'wasteland'. In terms of human health, insufficient studies have been conducted to corroborate the numerous complaints from residents in the mining towns about respiratory complications associated with air pollution. In order to have a comprehensive understanding of the extent of adverse impacts of mine air pollution on human health and the economic costs, future research involving interdisciplinary research groups is recommended.

Whilst much investment has been made by mining companies towards reducing SO₂ emissions, vigilance on the part of the  Zambia Environmental Management Agency is critical. The reviewed literature has shown that the current state of environmental degradation arising from mine air pollution has its genesis from the Smoke Damage Act of 1935. Furthermore, it has also been observed that the academic and research institutions in Zambia have not provided leadership in the area of research and potential areas of research have been highlighted. Nevertheless, based on this review it can be concluded that there is a strong link between human health, animal health, and environmental degradation and mine air pollution in Zambia.

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