Even in the current era of growing technology, the concentration of heavy metals present in drinking water is still not within the recommended limits as set by the regulatory authorities in different countries of the world. Drinking water contaminated with heavy metals namely; arsenic, cadmium, nickel, mercury, chromium, zinc, and lead is becoming a major health concern for public and health care professionals. Occupational exposure to heavy metals is known to occur by the utilization of these metals in various industrial processes and/or contents including color pigments and alloys. However, the predominant source resulting in measurable human exposure to heavy metals is the consumption of contaminated drinking water and the resulting health issues may include cardiovascular disorders, neuronal damage, renal injuries, and risk of cancer and diabetes. The general mechanism involved in heavy metal-induced toxicity is recognized to be the production of reactive oxygen species resulting oxidative damage and health related adverse effects. Thus utilization of heavy metal-contaminated water is resulting in high morbidity and mortality rates all over the world. Thereby, feeling the need to raise the concerns about contribution of different heavy metals in various health related issues, this article has discussed the global contamination of drinking water with heavy metals to assess the health hazards associated with consumption of heavy metal-contaminated water. A relationship between exposure limits and ultimate responses produced as well as the major organs affected have been reviewed. Acute and chronic poisoning symptoms and mechanisms responsible for such toxicities have also been discussed.

Prevalence of exposure of heavy metals and their impact on health consequences

In most rural settlements in Nigeria, access to clean and potable water is a great challenge, resulting in water borne diseases. The aim of this study was to assess the levels of some physical, chemical, biochemical and microbial water quality parameters in twelve hand – dug wells in a typical rural area (Igbora) of southwest region of the country. Seasonal variations and proximity to pollution sources (municipal waste dumps and defecation sites) were also examined. Parameters were determined using standard procedures. All parameters were detected up to 200 m from pollution source and most of them increased in concentration during the rainy season over the dry periods, pointing to infiltrations from storm water. Coliform population, Pb, NO 3- and Cd in most cases, exceeded the World Health Organization recommended thresholds for potable water. Effect of distance from pollution sources was more pronounced on fecal and total coliform counts, which decreased with increasing distance from waste dumps. The qualities of the well water samples were therefore not suitable for human consumption without adequate treatment. Regular monitoring of groundwater quality, abolishment of unhealthy waste disposal practices and introduction of modern techniques are recommended.

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Assessment of Groundwater Quality in a Typical Rural Settlement in Southwest Nigeria

The effect of a low mineral ash biochar on biomass production and nitrogen (N) uptake into plants was tested with wheat and radish in a Yellow Earth used for commercial vegetable production. The biochar had an acid neutralising capacity <0.5% CaCO3, a total C content of 75%, and a molar H/C ratio of 0.45, indicating stability due to its aromaticity. A pot trial was established under climate-controlled conditions. Five rates of N fertiliser (0, 17, 44, 88, 177kgN/ha) were applied as urea in combination with 5 biochar rates (0, 1.1, 2.2, 4.4, 11% w/w). Analysis of biomass production revealed a significant biocharN fertiliser interaction. In particular, increasing biochar concentrations improved biomass production in both crop species at lower N application rates. The highest biochar application rate resulted in significantly greater accumulation of NO3 - -N in the soil and lower NH4 + -N averaged across the 5N application rates. The biochar also decreased available P, and significantly increased microbial activity measured using the fluorescein diacetate method. Increasing N fertiliser application resulted in greater accumulation of NO3 - -N with no changes to NH4 + -N averaged across the 5 biochar application rates. Nitrogen fertiliser application did not influence microbial activity or biomass C. The trial suggests that in some cropping systems, biochar application will enable reduced N fertiliser input while maintaining productivity.

A glasshouse study on the interaction of low mineral ash biochar with nitrogen in a sandy soil

The current research examined the level of groundwater contamination near a municipal landfill site in Alimosho Local Government Area of Lagos State, Nigeria. Water quality parameters (physico-chemical and heavy metals) of leachate and groundwater samples were analyzed. The mean concentrations of all measured parameters except NO3G, PO4 + and CrG conform to the stipulated World Health Organization potable water standards and the Nigerian Standard for Drinking Water Quality. Mean concentration values for TDS, DO, NH4 , SO4 , PO4 , NO3G and ClG are 9.17 mg LG , 3.19 mg LG, 0.22 mg LG, 1.60 mg LG, 10.73 mg LG, 38.5 mg LG and 7.80 mg LG respectively. The mean concentration values for Fe, Mn, Zn and Cr in groundwater samples are 0.07mg LG, 0.08mg LG, 0.08mg LG and 0.44mg LG respectively. The current results show insignificant impact of the landfill operations on the groundwater resource. The existing soil stratigraphy at the landfill site consisting of clay and silty clay is deduced to have significantly influenced natural attenuation of leachate into the groundwater resource. It is however observed that in the absence of a properly designed leachate collection system, uncontrolled accumulation of leachates at the base of the landfill pose potential contamination risk to groundwater resource in the very near future. The research recommends an upgrade of the solous landfill to a standard that would guarantee adequate protection of both the surface and the groundwater resources in the locality.

Groundwater quality assessment near a municipal landfill, Lagos, Nigeria.

The drive for development and modernization has come at great cost. Various human activities in developed and developing countries, particularly in sub-Saharan Africa (SSA) have given rise to environmental safety concerns. Increased artisanal mining activities, illegal refining, use of leaded petrol, airborne dust, arbitrary discarding and burning of toxic waste, absorption of production industries in inhabited areas, inadequate environmental legislation, and weak implementation of policies, have given rise to the incomparable contamination and pollution associated with heavy metals in recent decades. This review evaluates the public health effects of heavy metals and their mixtures in SSA. This shows the extent and size of the problem posed by exposure to heavy metal mixtures in regard to public health.

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Heavy Metal Mixture Exposure and Effects in Developing Nations: An Update

The efficiency of ready-to-use, source-separated, composted municipal organic wastes of Nigerian origin on degradation of soil total petroleum hydrocarbons (TPHs) in soils polluted with petroleum products (crude oil, diesel, and spent engine oil) was assessed in screen house experiments. The effect of compost:soil ratios and combined effect of compost-phytoremediation technique were also studied. TPH was determined spectrophotometrically, after extraction with 1:1 acetone-dichloromethane mixture at 425 nm. Soil pH, electrical conductivity, and phytotoxicity to seed germination and growth of maize (Zea mays L.) served as risk assessments on soil quality and evidence of recovery for the oil-impacted soil. Results showed that the treatments increased soil pH and electrical conductivity but reduced TPH. Reductions in TPH by compost technology ranged from 40% to 75.87%. Toxicity to seed germination reduced from 100% to 16.12%. Positive correlations were obtained for plant agronomical parameters and gr...

Bioremediation of Soils Contaminated with Nigerian Petroleum Products Using Composted Municipal Wastes

Recycling of organic wastes through composting for land applications: a Nigerian experience.

Lead levels of certain consumer products in Nigeria: a case study of smoked fish foods from Abeokuta.

Assessment of lead in blood (BLL) and lead in urine (ULL) of some non-occupationally exposed, nonsmoking 214 pregnant Nigerian women, aged 17 to 49 years, and resident in Lagos was carried out using atomic absorption spectrometry with control subjects consisting of 113 nonpregnant women. From results, the mean BLL and ULL (μg/dL) for pregnant women (59.5 ± 2.1; 29.4 ± 1.1) were significantly (p 0.10). Study is a contribution to blood and urine lead status of Nigerian pregnant women, being relevant for healthcare management purposes, public health decision making, and possible primary prevention activities.

I. M. Adekunle

Papers

Assessment of Groundwater Quality in a Typical Rural Settlement in Southwest Nigeria

Bioremediation of Soils Contaminated with Nigerian Petroleum Products Using Composted Municipal Wastes

Recycling of organic wastes through composting for land applications: a Nigerian experience.

Lead levels of certain consumer products in Nigeria: a case study of smoked fish foods from Abeokuta.

Assessment of blood and urine lead levels of some pregnant women residing in Lagos, Nigeria