Background. The presence of heavy metals in the aquatic environment is a concern because of potential toxicity and threats to plant and animal life. Objective. The present study evaluated the joint action toxicity and biochemical effects of sublethal concentrations of copper (Cu), lead (Pb) and cadmium (Cd) against Clarias gariepinus over a period of 28 days. Methods. We procured fingerlings (weight: 5–8 g; length: 4.5–6.0 cm) and juveniles (weight: 20–25 g; length: 14.5–17.5 cm) from a commercial fish farm in Bariga, Lagos state, Nigeria. Test toxicants were selected from the analyzed heavy metals in the field based on their deviation from World Health Organization, Federal Environmental Protection Agency and United States Environmental Protection Agency standards. Fish were randomly loaded into a 4-L glass aquaria for the bioassay per toxicant concentration of two replicates and untreated control (dechlorinated tap water). Results. The derived 96 hour lethal concentration 50 (LC50) value of Cu (2.11 mg/L) was the most toxic followed by Cd (24.18 mg/L) and Pb (34.48 mg/L), which was the least toxic of the singly tested pollutants. The analysis of dose-response data of the joint action toxicity of Cu and Cd, and Cu and Pb determined 96 hour LC50 values of 1.804 mg/L and 2.15 mg/L, respectively. The interactions between the mixture of Cu:Cd conformed with the model of synergism (synergistic ratio (SR)>1 and relative toxic units (RTU)>1), while the interaction between Cu:Pb was found to be antagonistic (SR<1), with an SR value of 0.98. The biochemical effects study revealed that malondialdehyde (MDA) levels decreased significantly (P<0.05) in the exposed fish, reduced glutathione was not significant at (P<0.05), and levels of superoxide dismutase (SOD), catalase, glucose and cholesterol were significantly different (P<0.05). Discussion. The observed increased in the glutathione level in the Cu:Cd mixture and a corresponding decrease in MDA concentration in the liver of test animals revealed the ability of fish to overcome the effects of lipid peroxidation in this group because the Cu ion is displaced by Cd, and the fish were able to catalyze the breakdown of hydrogen peroxide via the Fenton reaction. Conclusions. Further studies on the joint action toxicity of heavy metals are needed in order to further determine their concentration in the local environment. Ethics Approval. Study protocols were approved by the Health Research Ethics Committee of the University of Lagos. Competing Interests. The authors declare no financial competing interests

Background. Urbanization, energy consumption, intensification of road traffic and rapid population growth pose significant challenges to ambient air quality. Therefore, regular monitoring of current air quality is essential. Objectives. The study investigated the concentration of sulfur dioxide (SO2), oxides of nitrogen (NOx), ozone (O3), ammonia (NH3) and carbon monoxide (CO) in ten different sites to investigate possible anthropogenic sources within Ibadan, Nigeria. Methods. Air samples were collected into specific absorbing solutions twice daily in the morning and afternoon for four weeks. The resulting solutions were analyzed following specific colorimetric techniques according to standard methods of analysis. Results. Average concentrations varied among the sampling areas. All were above background levels obtained at the control site. Overall concentrations were found to be 30±19 μg/m3 (SO2), 63±16 μg/m3 (NOx), 31±18 μg/m3 (O3), 463±180 μg/m3 (NH3) and 0.59±0.21 ppm (CO). These concentrations were present at the study areas at 15, 31, 17, 5 and 3 times the background concentrations for SO2, NOx, O3, NH3 and CO, respectively. Conclusions. In spite of the short duration of sampling, the data can guide future long term monitoring of air quality in Nigeria. The level of SO2 exceeded World Health Organization limits within this short duration. This is an indication of the need for long term air quality monitoring with a sustainable plan for air pollution management. Competing Interests. The authors declare no competing financial interests.

Background. Urbanization, industrialization and changes in consumption patterns have compounded the problem of solid waste management in Nigeria. Poor waste management threatens the well-being and health of the local population, particularly those living adjacent to dumpsites. Objectives. An assessment of the impact of dumpsites in a satellite town of the Federal Capital Territory, Abuja, Nigeria was carried out to determine the level of biophysical/chemical parameters (pH, temperature, conductivity, nutrients (calcium and magnesium), heavy metals (lead, chromium, zinc), and microbial burden) on the quality of soil and groundwater and their impact on health and the environment. Methods. Soil and ground water samples were collected in four different dumpsites (Bwari, Gwagwalada, Kuje and Azhatta) with reference samples taken from the Federal Capital Territory, Abuja, and taken to the laboratory for biophysical/chemical analysis using standard methods. Results. The results were compared with the national and World Health Organization (WHO) standard limits for soil and water respectively. Except for zinc, the average concentrations for heavy metals in the soil samples were higher in all four dumpsites than the permissible levels. Soil and water parameters that exceed the standard limits pose significant health and environment risks to nearby residents. Conclusions. There is a need for raising the awareness of residents living close to dumpsites and those who use the well or nearby streams for domestic activities on the need to carry out adequate water treatment prior to its use. Competing Interests. The authors declare no competing financial interests.

Background. Arsenic, antimony and selenium contamination of groundwater is of great concern due to the potential detrimental effects to human health. Objectives. This study investigates the occurrence and distribution of arsenic, antimony and selenium in the shallow groundwater system of Ibadan metropolis, southwestern Nigeria. Methods. A total of 210 groundwater samples were collected from 35 shallow wells (3.15–7.86 m) within the residential, commercial, industrial and agricultural areas of the metropolis during the dry and wet seasons. The average daily dose intake (ADD), hazard quotient (HQ) and hazard index (HI) of arsenic, antimony and selenium exposure in groundwater were calculated from these four studied areas for children and adults. Results. Average concentrations of arsenic, antimony and selenium in groundwater ranged between 2.17±3.49 to 33.8±37.2 μg/L, 13.5±15.0 to 33.2±36.8 μg/L and 7.33±6.22 to 46.3±22.4 μg/L, respectively. A corresponding analysis relay plot showed the order of occurrence of these trace metals in groundwater to be antimony>selenium>arsenic. The principal component analysis biplot showed that arsenic, antimony and selenium were fairly distributed in all of the study areas, suggesting the influence of geogenic factors. A total of 74.3% of sampling locations had antimony levels slightly above the World Health Organization (WHO) safe limit of 20 μg/L. Statistical t testing (0.05 confidence limit) showed a significant difference in seasonal levels of groundwater antimony concentration, with the dry season recording significantly higher levels with 100% of samples exceeding WHO safe limits. The chemical of highest potential human health concern is antimony, with a non-carcinogenic HQ risk factor >2 for both age groups. The overall non-carcinogenic HI was highest in the commercial area, 4.1989 for adults and 5.2487 for children. Conclusions. Antimony in groundwater within the Ibadan metropolis raises health concerns and a concerted effort is needed to identify its sources to avoid the risk of antimony toxicity. Competing Interests. The authors declare no competing financial interests.

Background. Tanzania has seen explosive development in small scale gold mining (SGM) operations. Recently, the use of cyanide has become more common in SGM, especially in the reprocessing of mercury-amalgamated tailings from artisanal mining sites. Objectives. The primary objective of this study was to examine the level of knowledge and adherence to the Cyanide Code among workers and managers at SGM operations in northwestern Tanzania that use cyanide for gold extraction, focusing on workers' safety. Methods. A cross-sectional study of workers and managers at 17 selected SGM sites was conducted. A random-cluster approach was used to recruit 215 mine workers and 23 mine managers who worked at the same sites for more than three months. Individuals participated in structured face-to-face interviews. Site evaluation checklists were also administered to assess adherence. Results. The majority of the SGM workers (61.4%, n=132) were not aware of the Cyanide Code. Among the mine managers, 64.2% (n=15) were aware of the Cyanide Code. Fifty-four percent of workers and 39.1% of managers did not adhere to the Cyanide Code. Workers who reported being trained on the Cyanide Code were significantly more likely to have knowledge about the Cyanide Code guidelines compared to untrained workers (adjusted odds ratio =20.3, confidence interval: 7.5 – 54.8). Discussion. Wide variations in knowledge of and adherence to the Cyanide Code were found. A manager's knowledge of Cyanide Code was significantly associated with workers' knowledge. High worker and manager knowledge was associated with increased site safety performance. Even though all the SGM sites were physically visited, some potentially hazardous practices may not have been revealed by managers and workers because of fear of possible regulatory actions due to disclosure of concerns related to their operation's safety compliance. Conclusions. The limited knowledge of the Cyanide Code among workers and managers, combined with poor adherence to cyanide waste management practices, indicates that there is a need for education, health promotion and sensitization among workers and managers to improve worker safety and minimize environmental health impacts. Participant Consent: Obtained Competing Interests. The authors declare no competing financial interests. Ethics Approval: Ethical approval was obtained from the Conjoint Catholic University of Health and Allied Sciences and Bugando Medical Centre Research Review and Ethics Committee (Ref. BREC/001/35/2014). Permission to conduct research in Geita District was obtained from the respective authorities at the regional and district levels and from owners of the SGM sites.

Background. Developing countries such as Zimbabwe deal with challenges in solid waste management such as insufficient waste recycling, hazardous wastes that are not separated for safe disposal, and landfills that are not properly engineered to prevent groundwater pollution. For these reasons, landfills in developing countries pose serious environmental and public health hazards. Objectives. The objective of this study was to assess heavy metal release and groundwater pollution from an unlined landfill in Bulawayo, Zimbabwe. The purpose of the study was to explore environmental and public health risks posed by improperly managed landfills in developing countries. Methods. We assessed levels of metal release from Richmond landfill in the city of Bulawayo, Zimbabwe by measuring lead, cadmium, chromium and copper levels in landfill soil, leachate and plants. We also monitored metal levels in groundwater from boreholes located in a residential area in the vicinity and downgradient of the landfill within a range of 800–2135 m. Soil was characterized at the landfill to assess potential sources of heavy metals. Results. All metals that were assessed were present in landfill soil and in leachate. There was high metal accumulation in weeds that were growing at the landfill, indicating mobility and bioavailability of the metals. Groundwater from nearby boreholes had high levels of lead (Pb) and cadmium (Cd) which were negatively correlated to distance from the landfill (p<0.01), indicating contamination from the landfill. The Pb and Cd levels exceeded World Health Organization standards for drinking water quality, posing health hazards to the communities who rely on the water. Solid waste at the landfill consisted of soft plastics (33%), hard plastics (18.6%), metals (3%), paper (8%), electronic waste (0.8%), organics (15.3%) and various other types (21.3%). Discussion. A combination of factors may be attributed to groundwater contamination. These include the co-disposal of metallic and electronic wastes at the landfill, lack of membrane lining at the landfill, inadequate leachate management and the porous geo-physical characteristics of the sub-surface at the landfill site. Conclusions. Our study highlights adverse environmental and public health consequences of co-disposal of metals and electronic wastes at improperly engineered municipal landfills. This is a ‘wake-up' call for policy makers in developing countries to improve solid waste management. Competing Interests. The authors declare they have no competing financial interests.

Introduction. An increase in population and related increased demand for health services, expansion of industries, and increasing transportation demands have increased the emission of dioxin and furan persistent organic pollutants (POPs) in Addis Ababa, Ethiopia. Objective. This study aimed to identify sources of dioxin and furan emissions, quantify their release into various environmental medias and assess related management practices. Methods. The standard United Nations Environmental Programme (UNEP) (2005) toolkit guide and default emission factor were used to identify the main anthropogenic sources and to quantify the amount of released dioxin and furan. Stratified random sampling techniques were applied to assess current management practices. Results. Nine main groups of dioxin and furan emission sources were identified. The emission of each source group was calculated by the activity rate data multiplied by an emission factor. The results found that about 138.85 g toxic equivalent(TEQ)/a(TEQ/year)of dioxin and furan were released to air, water, residue (materials remaining as sludge after sewage treatment or in the form of ash after incineration activity) and soil. Waste disposal activities recorded the largest release of dioxin and furan, accounting for 68.30 g TEQ/a of dioxin and furan to water and residue, 34.00 g TEQ/a to air and 0.64 g TEQ/a emitted into soil. Conclusions. Several sources of dioxin and furan emission were identified and the present study found that their management is inadequate. Waste disposal services are especially inadequate and generate higher amounts of dioxin and furan gasses. In addition, the organizations that are responsible for the release of dioxin and furan have no awareness of their release and inadequate management practices. The present study points to the need for reformulation of the national legal management framework, adoption of best available technology for disposal services such as incinerators with flue gas management, increasing public and stakeholders' awareness and participation and capacitating the responsible government organizations. Competing Interests. The authors declare no financial competing interests.

Background. Production of foods safe for consumption is an important issue worldwide. Organochlorine pesticides (OCP) are often used to preserve crops. Their use can have serious impacts on human health. Objectives. This research aims at assessing OCP residues in food samples from markets in Lagos in southwestern Nigeria and their risk to human health. Methods. Sixteen food samples were collected from Lagos, Nigeria and analyzed for organochlorine pesticide residues. Extraction was performed using an ultrasonicator, and analysis was carried out using a gas chromatograph-electron capture detector. Risk assessment was carried out by determining the hazard quotient. Results. Results of the OCP residues found in the foods were generally low, with dichlorodiphenyldichloroethylene (p,p'-DDE) having the highest residue concentration. The concentration of p,p'-DDE was as high as 110 ng/g in pulses and 123 ng/g in Cameroon and chili peppers. The risk index was <1 in most cases, with the exception of dichlorodiphenyldichloroethane (p,p'-DDD) in fruits for children. Discussion. The results were generally lower than what has been documented in other parts of the world and suggest that consumption of the foods investigated in the present study in Nigeria may be considered safe for the 13 OCPs investigated. Conclusions. There is a need for continuous monitoring of these OCPs and investigation of carbamate and phosphate pesticide residues since they are more widely used in farming practices in Nigeria. Competing Interests. The authors declare no competing financial interests.

Background. An increase in human and industrial activities has led to an increase in the pollution of soils by metals. If these metals become bioavailable, there is potential for human exposure, leading to possible health effects. Remediation of soils is important to ensure that soil is suitable for agricultural purposes. Objectives. To explore the use of sawdust and cow dung to remediate contaminated soil by reducing the bioavailability of metals. Methods. Soil samples were collected from Oke Afa dumpsite and Owode Onirin metallic store and total metal concentrations were determined by digesting with aqua regia and analyzed using flame atomic absorption spectrophotometry. The effect of varied dosages (1–5%) of cow dung and sawdust on the immobilization of the selected metals was investigated, and results were compared with disodium hydrogen phosphate (DSHP) amendments. A single reagent leaching test was carried out with 0.1 M calcium chloride to determine the bioavailability of metals before and after amendment. Results. Before amendment, the amount of bioavailable metal in the soil sample from Oke Afa dumpsite was 57.5 mg/kg, 194 mg/kg and 17.5 mg/kg for copper (Cu), lead (Pb) and zinc (Zn), respectively, while in the second soil sample, from Owode Onirin metallic store, the amount of bioavailable Cu, Pb and Zn was observed to be 19.9 mg/kg, 36.4 mg/kg and 11.1 mg/kg, respectively. Up to 73.4% of mobile Zn was immobilized using DSHP, while cow dung and saw dust were effective in the immobilization of Cu and Pb, but not Zn. Conclusions. Cow dung and sawdust reduced the bioavailability of copper and lead, while Zn can be effectively immobilized with the use of DSHP. It was generally observed that the bioavailability of heavy metals decreased with increasing dosage of the amendments. Competing Interests. The authors declare no competing financial interests.