Consumption of food contaminated with heavy metals is a major source of health problems for man and animals. Three commonly edible Leafy vegetables (Amaranthus hybridus, Celosia argentea ,Cochorus olitoris) from Agboju and Iba markets , Lagos Nigeria were sampled, identified, digested and analyzed with the aid of Atomic Absorption Spectrophotometer (AAS) as directed by APHA (American Public Health Association) to determine heavy metals concentration in them with the aim of ascertaining their edibility for human consumption. The mean concentration for each heavy metal in the samples gotten from each market were calculated, the comparison of these data was done amongst the two markets, and compared with the permissible levels set by the FAO and WHO. The results showed that the levels of Lead, Cadmium, Copper, Zinc, Iron, Nickel, Selenium and Chromium present in the vegetable concentrated in the following order Fe>Pb>Zn>Cd>Ni>Cu>Cr>Se. With regards to vegetables in questions, analysis of variance showed that some vegetables accumulated metals more than each other and as such indicated that metals like copper, cadmium, selenium, iron and zinc are significant at P<0.05) while others were not. Whereas with regards to locations, Iron, cadmium and lead were significant at P< (0.05) while other metals were not significant P>0.05). With significant values of lead, cadmium and nickel, recorded in both Amaranthus hybridus and Celosia argentea vegetables, vegetables consumers must be weary of vegetables to buy and the market that is save to buy from, especially markets located very close to highways or close to major busy roads .

Farmers have long considered urban agriculture as a panacea to urban food insecurity. However, growing food in cities is faced with many challenges like food contamination. Past studies on leafy vegetables focused on vegetables cultivated in urban centres. However, this paper aimed to determine and compare the level of heavy metals concentrations in soil and leafy vegetables in Urban Expressway Farms (UEF) and Peri-urban Road Farms (PRF) in Lagos, Nigeria. These two locations were purposefully selected. Soil Auger was used to drill holes to the required soil depth to collect soil samples. Sample of Amaranthus hybridus, Celosia argentea and Corchorus olitorius were collected using “envelope” principle. Pb, Cd and Mn residues in the samples were digested and determined using Atomic Absorption Spectrophotometer. The collected data were analysed using mean, standard deviation and Analysis of Variance. The mean pH value for UEF soil is 6.5 while PRF soil is 6.6. The highest Pb (0.93±0.06) was recorded in Celosia argentea at UEF. The highest mean concentration of Cd (0.51±0.11) was recorded in Amaranthus hybridus at UEF. The highest concentration for Mn was recorded in Amaranthus hybridus (0.98±0.02) at UEF. The concentrations of Pb in Celosia argentea at UEF 5 m from the expressway and Cd concentration in Amaranthus hybridus at 10 m from expressway were above the WHO/FAO permissible levels in vegetables. Level of heavy metal residue observed in soil and vegetables under this study were mostly influenced by the location of the farm-environment and not mainly the vegetable type.  The relative concentrations of Pb and Cd in all the three leafy vegetables raise some serious environmental concerns and need to be monitored regularly to prevent consumption of contaminated leafy vegetables. Farmers are encouraged to cultivate in fields far away from expressway.

Static bioassay methods were used under laboratory conditions to determine the accumulation of lead by Clarias gariepinus. The C. gariepinus fingerlings were exposed to sublethal analar grade of lead nitrate solution. The levels of lead in the samples were determined by Atomic Absorption Spectroscopy. The amount of lead accumulated by C. gariepinus was found to be a function of the concentration of lead in the water in which the test C. gariepinus were maintained and duration of exposure. After 8 weeks of exposure, to 0.032, 0.052, and 0.160mgl-1 the accumulated lead was 12.63, 26.94, and 33.49 Ugg-1 (fresh weight) respectively. The lead was found to be accumulated to different levels by the different tissues analysed. The order of accumulation was gill > liver > muscles. The high level of lead in the lead in the gill might not be unconnected with externally bound lead from the medium rather than internally bound lead to the gill. The increase lead concentration recorded in the control fish could be due to lead in their food (feed) or the lead present in the well water to which the fish were exposed in this study.

The effects of three traditional smoking methods on the concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in smoked fishes were studied to determine the concentration of PAHs in locally available and commonly consumed smoked fish species. Samples of two highly traded species of fish, Scomber scombrus and Horse markerel, among the low income people for immediate consumption were purchased from the market and processed using sawdust smoke, firewood smoke and charcoal smoke respectively. Some of the fresh fishes were also analyzed as control. The PAHs content were extracted with standard dichloromethane using solid-liquid extraction, and analyzed using Gas chromatography – Mass spectrophotometer (GC-MS) method. The results showed that fish samples processed with sawdust smoke recorded the highest concentrations of total PAHs, having 1.295 mg/kg in Horse markerel and 2.020 mg/kg in Scomber scombrus, followed by firewood smoked samples with total PAHs content of 0.910mg/kg in Horse markrel and 1.175 g/kg in Scomber scombrus while charcoal smoked samples recorded the least total PAHs levels of 0.590 mg/kg in Horse markerel and 0.960 mg/kg in Scomber scombrus. Benzo(a)pyrene concentrations which is usually used to estimate the carcinogenicity of other PAHs was below detection level in both species of fish. PAH4 was proposed by European food safety authority, recommendation level of 30 mg/kg was concluded by the EU regulation. Any PAHs have been associated with intense carcinogenicity in humans, and thus have implication for the quality and safety of these fish products. Therefore, it is imperative that regulatory bodies conduct awareness campaigns to educate the smoked fish processors, traders and consumers on the need to discourage the use of sawdust in smoking fish and adopt safer and improved methods of smoking fishes.

Several studies have been carried out on leafy vegetables but many did not assess the heavy metals in soil and leafy vegetables along urban-peri-urban gradient of Lagos State. The study assessed the concentration of heavy metals in the soil and leaves of three commonly consumed vegetables (Amaranthus hybridus, Celosia argentea and Corchorus olitorius) in Lagos State. Sampling was conducted in 2019 and 2020. Fe, Pb, Cu and Cd residues in the soil and the leafy vegetables samples were digested and determined using Atomic Absorption Spectrophotometer. The collected data were analyzed using simple descriptive statistics and Analysis of Variance. The range of values of the mean concentrations of the heavy metals in soil showed that Fe =20.76±0.20mg/kg – 107.83±17.02mg/kg, Pb = 0.13±0.07mg/kg –2.47± 0.45mg /kg, Cd=0.08 ± 0.02mg/kg – 6.07 ± 2.90mg/kg and Cu = 0.24±0.11mg/kg–40.20±4.90mg/kg. The range of values of the mean concentrations of the heavy metals in the leafy vegetables showed that Fe = 113.10±14.05mg/kg – 1.51±0.02mg/kg, Pb=0.51±0.09mg/kg - 0.001±0.001 mg/kg, Cd=0.51±0.01mg/kg-0.001±0.01amg/ kg, Cu=7.54±0.97 mg/kg - 0.36±0.03mg/kg. The Level of heavy metals residues in soil and the three leafy vegetables were at safe levels set by WHO/FAO except for Pb and Cd found in vegetables in Ketu and Yaba study locations.