Introduction: Inappropriate and excess vitamin supplementation, particularly for vitamin A, is increasingly recognized as a public health problem in developed countries. On the other hand, blind supplementation of vit...Introduction: Inappropriate and excess vitamin supplementation, particularly for vitamin A, is increasingly recognized as a public health problem in developed countries. On the other hand, blind supplementation of vitamin A, for children in developing countries is a subject of controversy in the literature. The crucial role of vitamin A in the process of spermatogenesis in adult rodents is well established, but only a few publications are consecrated to the long-term effect of vitamin A intake at a young age on testicular development and differentiation. Objectives: Our study aimed to evaluate the long-term effects of acute supplementation at an early age, in the post-natal period, on spermatogenesis and testicular trophicity at adult age. Material and Methods: Young Wistar Albinos rats of 22 days received an acute high dose of supplementation of vitamin A (retinyl palmitate). The control group, group 1, received only extra virgin olive oil, Group 2 a dose of 7000 IU/kg of retinyl palmitate, group 3, 14,000 IU/kg, and Group 4 a dose of 28,000 IU/kg. At 10 weeks of age, the testes’ testosterone levels were measured by ELISA. For histological assessment, sections were stained with Hematoxylin eosin, and the Johnsen score was used to evaluate spermatogenesis in the seminiferous tubules. Results: The average testicular weights of rats were significantly lower in group 4 (p < 0.05), and so was the testosterone level in the testis compared to the control group (p .01). Most of the seminiferous tubules were concerned by an arrest of spermatogenesis and the Johnsen score was decreased with a mean score of 5.96 ± 1.60 (p .001) in that Group. In Group 3, Johnsen’s score was significantly better than the one obtained with the control. Conclusion: We observed a negative effect in the long term with a high acute dose of supplementation of retinyl palmitate at a young age, on testicular development and differentiation. Despite a return to normal diet after that supplementation, during childhood, impaired spermatogenesis was identified at the adult age with an arrest of spermatogenesis. The reversibility of that lack of differentiation by a return to a normal diet is questionable and would need more investigation.展开更多
Cemented paste backfill(CPB)is extensively used for underground mine support and/or tailings management.However,CPB behavior under cyclic loadings might be affected by the chemistry of its porewater,which often contai...Cemented paste backfill(CPB)is extensively used for underground mine support and/or tailings management.However,CPB behavior under cyclic loadings might be affected by the chemistry of its porewater,which often contains sulphate ions.Till today,no studies have addressed the effect of sulphate on the response of CPB to cyclic loadings by using shaking table technique.This study presents new findings of assessing the effect of the sulphate in the pore water of CPB on its geotechnical response to cyclic loading by using shaking table.CPB mixtures were prepared(with and without sulphate),poured into a flexible laminar shear box,cured to 4 h,and then exposed to cyclic loading using one-dimensional(1D)shaking table.Several parameters(e.g.pore water pressure,settlement,lateral deformation,acceleration,electrical conductivity,effective stress,and liquefaction susceptibility)were monitored or determined before,during,and after shaking.Obtained results indicate that the sulphate-bearing CPB cured to 4 h can be prone to liquefaction under the studied conditions.However,sulphate-free CPB samples are resistant to liquefaction.These results are expected to contribute to a better understanding of the effect of water chemistry on the cyclic behavior of CPB,consequently enhancing the cost-effective design of CPB structures.展开更多
In this paper, the hydro-mechanical behavior and physical properties of mature fine tailings(MFT) under atmospheric drying are investigated through a column study. In the study, evaporation takes place in the developm...In this paper, the hydro-mechanical behavior and physical properties of mature fine tailings(MFT) under atmospheric drying are investigated through a column study. In the study, evaporation takes place in the development of suction in the upper parts of the column and increasing suction leads to higher strength in the tailings. After 5 days, the suction in the first lift is around 17 k Pa in the upper part of the column.When a second lift is added, the first lift initially loses strength but over a 30 days' period, the strength is recovered to its prior value and suction in the second lift reaches 500 k Pa. The vane shear strength values show a substantial increase in the strength of the MFT after 30 days under atmospheric drying and drainage. The 90% strength found in the column exceeds the threshold(5 k Pa). The hydraulic-mechanical properties of the deposited tailings are closely coupled due to several mechanisms, such as evaporation,drainage, self-consolidation, suction and crack development. The findings of this study will provide a better understanding of the placement behavior of multiple lifts of MFT and thus contribute to reclamation design standards and reduce the use of dedicated disposal areas.展开更多
Natural methane(CH_4) oxidation that is carried out through the use of landfill covers(biocovers) is a promising method for reducing CH_4 emissions from landfills.Previous studies on peat-based landfill covers have ma...Natural methane(CH_4) oxidation that is carried out through the use of landfill covers(biocovers) is a promising method for reducing CH_4 emissions from landfills.Previous studies on peat-based landfill covers have mainly focused on their biochemical properties(e.g.CH_4 oxidation capacity).However,the utilization of peat as a cover material also requires a solid understanding of its geotechnical properties(thermal,hydraulic,and mechanical),which are critical to the performance of any biocover.Therefore,the objective of this context is to investigate and assess the geotechnical properties of peat-based cover materials(peat,peat-sand mixture),including compaction,consolidation,and hydraulic and thermal conductivities.The studied materials show high compressibility to the increase of vertical stress,with compression index(C_c) values ranging from 0.16 to 0.358.The compressibility is a function of sand content such that the peat-sand mixture(1:3) has the lowest C_c value.Both the thermal and hydraulic conductivities are functions of moisture content,dry density,and sand content.The hydraulic conductivity varies from 1.74 × 10^(-9) m/s to 7.35 × 10^(-9) m/s,and increases with the increase in sand content.The thermal conductivity of the studied samples varies between 0.54 W/(m K) and 1.41 W/(m K) and it increases with the increases in moisture and sand contents.Increases in sand content generally increase the mechanical behavior of peat-based covers;however,they also cause relatively high hydraulic and thermal conductivities which are not favored properties for biocovers.展开更多
Although a large number of previous researches have significantly contributed to the understanding of the quasi-static mechanical behavior of cemented tailings backfill,an evolutive porous medium used in underground m...Although a large number of previous researches have significantly contributed to the understanding of the quasi-static mechanical behavior of cemented tailings backfill,an evolutive porous medium used in underground mine cavities,very few efforts have been made to improve the knowledge on its response under sudden dynamic loading during the curing process.In fact,there is a great need for such information given that cemented backfill structures are often subjected to blast loadings due to mine exploitations.In this study,a coupled thermo-hydro-mechanical-chemical(THMC)-viscoplastic cap model is developed to describe the behavior of cementing mine backfill material under blast loading.A THMC model for cemented backfill is adopted to evaluate its behavior and evolution of its properties in curing processes with coupled thermal,hydraulic,mechanical and chemical factors.Then,the model is coupled to a Perzyna type of viscoplastic model with a modified smooth surface cap envelope and a variable bulk modulus,in order to reasonably capture the nonlinear and rate-dependent behaviors of the cemented tailings backfill under blast loading.All of the parameters required for the variable-modulus viscoplastic cap model were obtained by applying the THMC model to reproducing evolution of cemented paste backfill(CPB)properties in the curing process.Thus,the behavior of hydrating cemented backfill under high-rate impacts can be evaluated under any curing time of concern.The validation results of the proposed model indicate a good agreement between the experimental and the simulated results.The authors believe that the proposed model will contribute to a better understanding of the performance of hydrating cemented backfill under blasting,and also to practical risk management of backfill structures associated with such a dynamic condition.展开更多
Compacted bentonite-sand(B/S)mixtures have been used as a barrier material in engineered barrier systems(EBSs)of deep geological repositories(DGR)to store nuclear wastes.This study investigates the individual and comb...Compacted bentonite-sand(B/S)mixtures have been used as a barrier material in engineered barrier systems(EBSs)of deep geological repositories(DGR)to store nuclear wastes.This study investigates the individual and combined effects of different chemical compositions of deep groundwaters(chemical factor)at potential repository sites in Canada(the Trenton and Guelph regions in Ontario),heat generated in DGRs(thermal factor),dry densities and mass ratios of bentonite and sand mixtures(physical factors)on the swelling behavior and ability of bentonite-based materials.In this study,swelling tests are conducted on B/S mixtures with different B/S mix ratios(20/80 to 70/30),compacted at different dry densities(ρd=1.6-2 g/cm^(3)),saturated with different types of water(distilled water and simulated deep groundwater of Trenton and Guelph)and exposed to different temperatures(20℃-80℃).Moreover,scanning electron microscopy(SEM)analyses,mercury intrusion porosimetry(MIP)tests and X-ray diffractometry(XRD)analyses are carried out to evaluate the morphological,microstructural and mineralogical characteristics of the B/S mixtures.The test results indicate that the swelling potential of the B/S mixtures is significantly affected by these physical and chemical factors as well as the combined effects of the chemical and thermal factors.A significant decrease in the swelling capacity is observed when the B/S materials are exposed to the aforementioned groundwaters.A large decrease in the swelling capacity is observed for higher bentonite content in the mixtures.Moreover,higher temperatures intensify the chemically-induced reduction of the swelling capacity of the B/S barrier materials.This decrease in the swelling capacity is caused by the chemical and/or microstructural changes of the materials.The results from this research will help engineers to design and build EBSs for DGRs with similar groundwater and thermal conditions.展开更多
Introduction: Chronic respiratory diseases (CRD) are obvious effects of air pollution and the third reason of death in developing countries. In Africa, air pollution from road traffic is one of the main causes of poor...Introduction: Chronic respiratory diseases (CRD) are obvious effects of air pollution and the third reason of death in developing countries. In Africa, air pollution from road traffic is one of the main causes of poor air quality. We set out to systematically review existing published researches on traffic related to air pollution and CRD, particularly asthma and Chronic Obstructive Pulmonary Disease (COPD) in Africa. Methods: A literature search of PubMed, Scholar and LISSA databases, published journals, reference articles, published up to 31 December 2016, has been done by using a research strategy procedure. Texts were reviewed for inclusion. Studies were included if they met the following criteria: 1) the relationship between asthma or COPD with ambient air pollution related to road traffic was studied and 2) the population included people from Africa or lived in Africa. Articles written in English and French were included. Results: Fifty-five articles were selected in this review, of which twenty-seven were on air pollution and CRD in Africa. The proximity of the residence or workplace to the traffic is associated with an increased risk of asthma with a dose-response relationship. The estimated prevalence of COPD varies between 2.7% and 38.5%. Conclusion: There is little research on traffic related to air pollution and CRD in Africa. Strategies to reduce traffic related to air pollution in African cities have been proposed in order to have a healthier ambient air.展开更多
Water contamination by chemical pollutants is increasingly associated with waterborne diseases worldwide. The objective of this study is to assess the chemical health risk associated with drinking water consumption in...Water contamination by chemical pollutants is increasingly associated with waterborne diseases worldwide. The objective of this study is to assess the chemical health risk associated with drinking water consumption in Dakar, Senegal. The methodology adopted in this study is based on the determination of trace metals (Cd, Pb, Fe, Cu and Mn) in human drinking water by flame atomic absorption spectrometry, the estimation of the exposure of populations of the study area on the basis of the quantity of water consumed daily and the determination of the hazard quotient which allows estimating the health risk. The results indicate unacceptable levels of Pb and Cd in the water according to World Health Organization (WHO) guidelines, while the concentrations of Fe, Cu and Mn are below the regulatory values. The hazard quotient (HQ) is in the majority of samples higher than 1 in children and infants for scenario 1 (based on WHO data), reflecting a high risk for this target. In scenario 2 based on consumption data from the populations studied, the HQ is greater than 1 only in heavy consumers. The drinking water consumed by Dakar population presents health risks related to Pb and Cd, particularly for infants, children and heavy consumers, hence the need to strengthen the water treatment system before home consumption.展开更多
Introduction: Road traffic exposes bus drivers to the detrimental effects of air pollutants on respiratory health. This study determined the frequency of chronic respiratory illnesses and its related factors among bus...Introduction: Road traffic exposes bus drivers to the detrimental effects of air pollutants on respiratory health. This study determined the frequency of chronic respiratory illnesses and its related factors among bus drivers in Dakar, Senegal. Methods: This study had a cross-sectional design conducted in a total of 178 bus drivers in Dakar, Senegal. A questionnaire was used to inquire about socio-economic characteristics, occupational factors and respiratory symptoms of bus drivers. Lung function tests were used to determine the presence of asthma and Chronic Obstructive Pulmonary Disease (COPD). The relationship between our variables of interest and respiratory diseases was determined by logistic regression analysis. Results: The results of the study show that 57.9% of bus drivers had a chronic cough, and 65.7% had recurrent cold. Lung function tests showed that 38.8% of bus drivers had asthma and 30.3% COPD. Multivariate analysis found that recurrent cold increased the risk of asthma (OR = 6.3, 95% CI: 1.12 - 35.79) and COPD (OR = 7.7, 95% CI: 1.14 - 52.8). The respiratory health status of bus drivers depended on the work area (OR = 3.2, 95% CI: 1.13 - 9.31). Conclusion: The respiratory symptoms and illnesses observed among bus drivers are associated with their exposure to air pollutants from road traffic.展开更多
Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air po...Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air pollution. The study determined the prevalence of allergic rhinitis and its associated risk factors in these vendors. Methods: This was a cross-sectional survey based on a structured questionnaire, conducted among vendors in the neighborhoods of HLM, Medina and Petersen in Dakar, Senegal. A total of 200 vendors were interviewed. Symptoms of allergic rhinitis were defined as the simultaneous presence of rhinorrhea, nasal congestion and sneezing in the absence of respiratory infection. A logistic regression analysis was performed to determine the relationship between socio-demographic characteristics, occupational factors, and allergic rhinitis. Results: Results of the study show a prevalence of 43% of allergic rhinitis among vendors. Multivariate analysis showed that the independent factors associated with allergic rhinitis in these vendors were age [OR: 3.28 (1.02 - 10.51)], working area [OR: 8.31 (2.39 - 28.95)], exposure to multiple sources of pollution [OR: 4.08 (1.43 - 11.63)], and recurrent cold [OR: 4.39 (1.15 - 16.85)]. Conclusion: The prevalence of allergic rhinitis was high among vendors in Dakar. Our data suggest that exposure to air pollution at the workplace in vendors could lead to allergic rhinitis.展开更多
The Tobène deposit forms, with those of NdomorDiop and KeurMor Fall, the large phosphate deposit of Ta?ba. The Tobène site has been the subject of lithostratigraphic, biostratigraphic, mineralogical, petrogr...The Tobène deposit forms, with those of NdomorDiop and KeurMor Fall, the large phosphate deposit of Ta?ba. The Tobène site has been the subject of lithostratigraphic, biostratigraphic, mineralogical, petrographic and geochemical studies. The lithostratigraphic and biostratigraphic studies dated the series from Lutetian to Bartonian composed of five lithological units, which are assembled by [1] in three formations. The mineralogical study shows three groups of minerals associated with the different phosphatic facies identified in the various sectors of Tobène: 1) characteristic minerals of sedimentological conditions;2) minerals of diagenetic origin;3) minerals of alteration. The petrographic study allowed an inventory of the constituting visible grains of the microfacies as well as the different phases of diagenetic and post-diagenetic transformations that may have affected them. It thus appears that the phosphatic ore of Tobène has undergone an extensive diagenesis (compaction, dissolution-recrystallization, epigenesis) to which a relatively intense ferruginization has been added.展开更多
文摘Introduction: Inappropriate and excess vitamin supplementation, particularly for vitamin A, is increasingly recognized as a public health problem in developed countries. On the other hand, blind supplementation of vitamin A, for children in developing countries is a subject of controversy in the literature. The crucial role of vitamin A in the process of spermatogenesis in adult rodents is well established, but only a few publications are consecrated to the long-term effect of vitamin A intake at a young age on testicular development and differentiation. Objectives: Our study aimed to evaluate the long-term effects of acute supplementation at an early age, in the post-natal period, on spermatogenesis and testicular trophicity at adult age. Material and Methods: Young Wistar Albinos rats of 22 days received an acute high dose of supplementation of vitamin A (retinyl palmitate). The control group, group 1, received only extra virgin olive oil, Group 2 a dose of 7000 IU/kg of retinyl palmitate, group 3, 14,000 IU/kg, and Group 4 a dose of 28,000 IU/kg. At 10 weeks of age, the testes’ testosterone levels were measured by ELISA. For histological assessment, sections were stained with Hematoxylin eosin, and the Johnsen score was used to evaluate spermatogenesis in the seminiferous tubules. Results: The average testicular weights of rats were significantly lower in group 4 (p < 0.05), and so was the testosterone level in the testis compared to the control group (p .01). Most of the seminiferous tubules were concerned by an arrest of spermatogenesis and the Johnsen score was decreased with a mean score of 5.96 ± 1.60 (p .001) in that Group. In Group 3, Johnsen’s score was significantly better than the one obtained with the control. Conclusion: We observed a negative effect in the long term with a high acute dose of supplementation of retinyl palmitate at a young age, on testicular development and differentiation. Despite a return to normal diet after that supplementation, during childhood, impaired spermatogenesis was identified at the adult age with an arrest of spermatogenesis. The reversibility of that lack of differentiation by a return to a normal diet is questionable and would need more investigation.
基金The authors would like to thank the National Natural Sciences and Engineering Research Council of Canada(NSERC)for financially supporting this project
文摘Cemented paste backfill(CPB)is extensively used for underground mine support and/or tailings management.However,CPB behavior under cyclic loadings might be affected by the chemistry of its porewater,which often contains sulphate ions.Till today,no studies have addressed the effect of sulphate on the response of CPB to cyclic loadings by using shaking table technique.This study presents new findings of assessing the effect of the sulphate in the pore water of CPB on its geotechnical response to cyclic loading by using shaking table.CPB mixtures were prepared(with and without sulphate),poured into a flexible laminar shear box,cured to 4 h,and then exposed to cyclic loading using one-dimensional(1D)shaking table.Several parameters(e.g.pore water pressure,settlement,lateral deformation,acceleration,electrical conductivity,effective stress,and liquefaction susceptibility)were monitored or determined before,during,and after shaking.Obtained results indicate that the sulphate-bearing CPB cured to 4 h can be prone to liquefaction under the studied conditions.However,sulphate-free CPB samples are resistant to liquefaction.These results are expected to contribute to a better understanding of the effect of water chemistry on the cyclic behavior of CPB,consequently enhancing the cost-effective design of CPB structures.
基金the University of Ottawa and the National Natural Sciences and Engineering Research Council of Canada(NSERC)for supporting this research
文摘In this paper, the hydro-mechanical behavior and physical properties of mature fine tailings(MFT) under atmospheric drying are investigated through a column study. In the study, evaporation takes place in the development of suction in the upper parts of the column and increasing suction leads to higher strength in the tailings. After 5 days, the suction in the first lift is around 17 k Pa in the upper part of the column.When a second lift is added, the first lift initially loses strength but over a 30 days' period, the strength is recovered to its prior value and suction in the second lift reaches 500 k Pa. The vane shear strength values show a substantial increase in the strength of the MFT after 30 days under atmospheric drying and drainage. The 90% strength found in the column exceeds the threshold(5 k Pa). The hydraulic-mechanical properties of the deposited tailings are closely coupled due to several mechanisms, such as evaporation,drainage, self-consolidation, suction and crack development. The findings of this study will provide a better understanding of the placement behavior of multiple lifts of MFT and thus contribute to reclamation design standards and reduce the use of dedicated disposal areas.
文摘Natural methane(CH_4) oxidation that is carried out through the use of landfill covers(biocovers) is a promising method for reducing CH_4 emissions from landfills.Previous studies on peat-based landfill covers have mainly focused on their biochemical properties(e.g.CH_4 oxidation capacity).However,the utilization of peat as a cover material also requires a solid understanding of its geotechnical properties(thermal,hydraulic,and mechanical),which are critical to the performance of any biocover.Therefore,the objective of this context is to investigate and assess the geotechnical properties of peat-based cover materials(peat,peat-sand mixture),including compaction,consolidation,and hydraulic and thermal conductivities.The studied materials show high compressibility to the increase of vertical stress,with compression index(C_c) values ranging from 0.16 to 0.358.The compressibility is a function of sand content such that the peat-sand mixture(1:3) has the lowest C_c value.Both the thermal and hydraulic conductivities are functions of moisture content,dry density,and sand content.The hydraulic conductivity varies from 1.74 × 10^(-9) m/s to 7.35 × 10^(-9) m/s,and increases with the increase in sand content.The thermal conductivity of the studied samples varies between 0.54 W/(m K) and 1.41 W/(m K) and it increases with the increases in moisture and sand contents.Increases in sand content generally increase the mechanical behavior of peat-based covers;however,they also cause relatively high hydraulic and thermal conductivities which are not favored properties for biocovers.
文摘Although a large number of previous researches have significantly contributed to the understanding of the quasi-static mechanical behavior of cemented tailings backfill,an evolutive porous medium used in underground mine cavities,very few efforts have been made to improve the knowledge on its response under sudden dynamic loading during the curing process.In fact,there is a great need for such information given that cemented backfill structures are often subjected to blast loadings due to mine exploitations.In this study,a coupled thermo-hydro-mechanical-chemical(THMC)-viscoplastic cap model is developed to describe the behavior of cementing mine backfill material under blast loading.A THMC model for cemented backfill is adopted to evaluate its behavior and evolution of its properties in curing processes with coupled thermal,hydraulic,mechanical and chemical factors.Then,the model is coupled to a Perzyna type of viscoplastic model with a modified smooth surface cap envelope and a variable bulk modulus,in order to reasonably capture the nonlinear and rate-dependent behaviors of the cemented tailings backfill under blast loading.All of the parameters required for the variable-modulus viscoplastic cap model were obtained by applying the THMC model to reproducing evolution of cemented paste backfill(CPB)properties in the curing process.Thus,the behavior of hydrating cemented backfill under high-rate impacts can be evaluated under any curing time of concern.The validation results of the proposed model indicate a good agreement between the experimental and the simulated results.The authors believe that the proposed model will contribute to a better understanding of the performance of hydrating cemented backfill under blasting,and also to practical risk management of backfill structures associated with such a dynamic condition.
基金the funding support from Natural Sciences and Engineering Research Council of Canada (NSERC)
文摘Compacted bentonite-sand(B/S)mixtures have been used as a barrier material in engineered barrier systems(EBSs)of deep geological repositories(DGR)to store nuclear wastes.This study investigates the individual and combined effects of different chemical compositions of deep groundwaters(chemical factor)at potential repository sites in Canada(the Trenton and Guelph regions in Ontario),heat generated in DGRs(thermal factor),dry densities and mass ratios of bentonite and sand mixtures(physical factors)on the swelling behavior and ability of bentonite-based materials.In this study,swelling tests are conducted on B/S mixtures with different B/S mix ratios(20/80 to 70/30),compacted at different dry densities(ρd=1.6-2 g/cm^(3)),saturated with different types of water(distilled water and simulated deep groundwater of Trenton and Guelph)and exposed to different temperatures(20℃-80℃).Moreover,scanning electron microscopy(SEM)analyses,mercury intrusion porosimetry(MIP)tests and X-ray diffractometry(XRD)analyses are carried out to evaluate the morphological,microstructural and mineralogical characteristics of the B/S mixtures.The test results indicate that the swelling potential of the B/S mixtures is significantly affected by these physical and chemical factors as well as the combined effects of the chemical and thermal factors.A significant decrease in the swelling capacity is observed when the B/S materials are exposed to the aforementioned groundwaters.A large decrease in the swelling capacity is observed for higher bentonite content in the mixtures.Moreover,higher temperatures intensify the chemically-induced reduction of the swelling capacity of the B/S barrier materials.This decrease in the swelling capacity is caused by the chemical and/or microstructural changes of the materials.The results from this research will help engineers to design and build EBSs for DGRs with similar groundwater and thermal conditions.
文摘Introduction: Chronic respiratory diseases (CRD) are obvious effects of air pollution and the third reason of death in developing countries. In Africa, air pollution from road traffic is one of the main causes of poor air quality. We set out to systematically review existing published researches on traffic related to air pollution and CRD, particularly asthma and Chronic Obstructive Pulmonary Disease (COPD) in Africa. Methods: A literature search of PubMed, Scholar and LISSA databases, published journals, reference articles, published up to 31 December 2016, has been done by using a research strategy procedure. Texts were reviewed for inclusion. Studies were included if they met the following criteria: 1) the relationship between asthma or COPD with ambient air pollution related to road traffic was studied and 2) the population included people from Africa or lived in Africa. Articles written in English and French were included. Results: Fifty-five articles were selected in this review, of which twenty-seven were on air pollution and CRD in Africa. The proximity of the residence or workplace to the traffic is associated with an increased risk of asthma with a dose-response relationship. The estimated prevalence of COPD varies between 2.7% and 38.5%. Conclusion: There is little research on traffic related to air pollution and CRD in Africa. Strategies to reduce traffic related to air pollution in African cities have been proposed in order to have a healthier ambient air.
文摘Water contamination by chemical pollutants is increasingly associated with waterborne diseases worldwide. The objective of this study is to assess the chemical health risk associated with drinking water consumption in Dakar, Senegal. The methodology adopted in this study is based on the determination of trace metals (Cd, Pb, Fe, Cu and Mn) in human drinking water by flame atomic absorption spectrometry, the estimation of the exposure of populations of the study area on the basis of the quantity of water consumed daily and the determination of the hazard quotient which allows estimating the health risk. The results indicate unacceptable levels of Pb and Cd in the water according to World Health Organization (WHO) guidelines, while the concentrations of Fe, Cu and Mn are below the regulatory values. The hazard quotient (HQ) is in the majority of samples higher than 1 in children and infants for scenario 1 (based on WHO data), reflecting a high risk for this target. In scenario 2 based on consumption data from the populations studied, the HQ is greater than 1 only in heavy consumers. The drinking water consumed by Dakar population presents health risks related to Pb and Cd, particularly for infants, children and heavy consumers, hence the need to strengthen the water treatment system before home consumption.
文摘Introduction: Road traffic exposes bus drivers to the detrimental effects of air pollutants on respiratory health. This study determined the frequency of chronic respiratory illnesses and its related factors among bus drivers in Dakar, Senegal. Methods: This study had a cross-sectional design conducted in a total of 178 bus drivers in Dakar, Senegal. A questionnaire was used to inquire about socio-economic characteristics, occupational factors and respiratory symptoms of bus drivers. Lung function tests were used to determine the presence of asthma and Chronic Obstructive Pulmonary Disease (COPD). The relationship between our variables of interest and respiratory diseases was determined by logistic regression analysis. Results: The results of the study show that 57.9% of bus drivers had a chronic cough, and 65.7% had recurrent cold. Lung function tests showed that 38.8% of bus drivers had asthma and 30.3% COPD. Multivariate analysis found that recurrent cold increased the risk of asthma (OR = 6.3, 95% CI: 1.12 - 35.79) and COPD (OR = 7.7, 95% CI: 1.14 - 52.8). The respiratory health status of bus drivers depended on the work area (OR = 3.2, 95% CI: 1.13 - 9.31). Conclusion: The respiratory symptoms and illnesses observed among bus drivers are associated with their exposure to air pollutants from road traffic.
文摘Introduction: The work environment is one of the main causes of allergic rhinitis. The majority of vendors in Dakar work in places close to roads that are very frequented by vehicles, exposing them to increased air pollution. The study determined the prevalence of allergic rhinitis and its associated risk factors in these vendors. Methods: This was a cross-sectional survey based on a structured questionnaire, conducted among vendors in the neighborhoods of HLM, Medina and Petersen in Dakar, Senegal. A total of 200 vendors were interviewed. Symptoms of allergic rhinitis were defined as the simultaneous presence of rhinorrhea, nasal congestion and sneezing in the absence of respiratory infection. A logistic regression analysis was performed to determine the relationship between socio-demographic characteristics, occupational factors, and allergic rhinitis. Results: Results of the study show a prevalence of 43% of allergic rhinitis among vendors. Multivariate analysis showed that the independent factors associated with allergic rhinitis in these vendors were age [OR: 3.28 (1.02 - 10.51)], working area [OR: 8.31 (2.39 - 28.95)], exposure to multiple sources of pollution [OR: 4.08 (1.43 - 11.63)], and recurrent cold [OR: 4.39 (1.15 - 16.85)]. Conclusion: The prevalence of allergic rhinitis was high among vendors in Dakar. Our data suggest that exposure to air pollution at the workplace in vendors could lead to allergic rhinitis.
文摘The Tobène deposit forms, with those of NdomorDiop and KeurMor Fall, the large phosphate deposit of Ta?ba. The Tobène site has been the subject of lithostratigraphic, biostratigraphic, mineralogical, petrographic and geochemical studies. The lithostratigraphic and biostratigraphic studies dated the series from Lutetian to Bartonian composed of five lithological units, which are assembled by [1] in three formations. The mineralogical study shows three groups of minerals associated with the different phosphatic facies identified in the various sectors of Tobène: 1) characteristic minerals of sedimentological conditions;2) minerals of diagenetic origin;3) minerals of alteration. The petrographic study allowed an inventory of the constituting visible grains of the microfacies as well as the different phases of diagenetic and post-diagenetic transformations that may have affected them. It thus appears that the phosphatic ore of Tobène has undergone an extensive diagenesis (compaction, dissolution-recrystallization, epigenesis) to which a relatively intense ferruginization has been added.
