Estimation of Human Health Risk Due to Heavy Metals around Schools and Auto-Mobile Workshops near Frequented Roads in Kaduna State, Nigeria

Heavy metals are widely known for their potential to cause carcinogenic and non-carcinogenic health risks. In this work, the carcinogenic and non-carcinogenic health risks associated with heavy metals in the vicinity of schools and auto mechanic workshops close to busy roads in Kaduna state was assessed using NEX CG EDXRF MODEL with brand name RIGAKU situated at a UTM Laboratory, Malaysia. The obtained heavy metals concentrations were used to estimate the health effects that might result from exposure to carcinogenic and non-carcinogenic chemicals for both the population ages using US EPA methodology. Findings indicated that in some locations the carcinogenic and non-carcinogenic hazards associated with exposure for residents was greater than the US EPA acceptable thresholds of 10-4 and 1 respectively. This indicated that the heavy metals may result to unacceptable carcinogenic and non-carcinogenic risks, which is an issue of concern in public health especially looking at the way school children play around these areas. The present study therefore provides scientific basis for strategies required to protect human and environmental health in schools and automobile workshops

Industrial metal pollution in water and probabilistic assessment of human health risk

© 2016 Elsevier Ltd Concentration of eight heavy metals in surface and groundwater around Dhaka Export Processing Zone (DEPZ) industrial area were investigated, and the health risk posed to local children and adult residents via ingestion and dermal contact was evaluated using deterministic and probabilistic approaches. Metal concentrations (except Cu, Mn, Ni, and Zn) in Bangshi River water were above the drinking water quality guidelines, while in groundwater were less than the recommended limits. Concentration of metals in surface water decreased as a function of distance. Estimations of non-carcinogenic health risk for surface water revealed that mean hazard index (HI) values of As, Cr, Cu, and Pb for combined pathways (i.e., ingestion and dermal contact) were >1.0 for both age groups. The estimated risk mainly came from the ingestion pathway. However, the HI values for all the examined metals in groundwater were 1 × 10−4 for adult and children, respectively. Deterministic and probabilistic estimations of cancer risk through exposure to groundwater were well below the safety limit. Overall, the population exposed to Bangshi River water remained at carcinogenic and non-carcinogenic health threat and the risk was higher for adults. Sensitivity analysis identified exposure duration (ED) and ingestion rate (IR) of water as the most relevant variables affecting the probabilistic risk estimation model outcome

Development and application of a computer simulation tool for ecological risk assessments

In an effort to improve tools in ecological risk assessment (ERA), an ERA software tool was developed and applied. Based on a preliminary evaluation of existing ecorisk models, the relative deficiencies were identified and included the need for a user-friendly interface, an interactive database management system (DBMS), and a comprehensive evaluation of exposure pathways. In this research, Visual Basic (VB) 6.0 and Microsoft SQL server were selected for developing the Windows-based interface and local DBMS, respectively. For the exposure estimate, Yuma and Aberdeen Proving Grounds were identified as baseline ecosystems. Terrestrial and aquatic plant and animal receptor selection was based on the U.S. EPA Guidelines for ERA. All potential exposure pathways were included. Overall, results of the case study of replacing electroplated chromium coatings with sputtered tantalum showed that the most significant exposure resulted from molybdenum and hexavalent chromium, which posed moderately high and slight potential adverse risks to aquatic and terrestrial species at both sites. On the other hand, tantalum (with vanadium as the surrogate) resulted in the least risk to the receptors within the studied areas. However, a slight potential adverse risk was also observed for a large faction of terrestrial mammals at both sites as a result of using sodium vanadate as surrogate for Ta. An uncertainty analysis was included to address the data quality and demonstrated that distribution coefficients have the most influence on the results

Bioaccessibility of metals and human health risk assessment in community urban gardens

Pseudo-total (i.e. aqua regia extractable) and gastric-bioaccessible (i.e. glycine + HCl extractable) concentrations of Ca, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in a total of 48 samples collected from six community urban gardens of different characteristics in the city of Madrid (Spain). Calcium carbonate appears to be the soil property that determines the bioaccessibility of a majority of those elements, and the lack of influence of organic matter, pH and texture can be explained by their low levels in the samples (organic matter) or their narrow range of variation (pH and texture). A conservative risk assessment with bioaccessible concentrations in two scenarios, i.e. adult urban farmers and children playing in urban gardens, revealed acceptable levels of risk, but with large differences between urban gardens depending on their history of land use and their proximity to busy areas in the city center. Only in a worst-case scenario in which children who use urban gardens as recreational areas also eat the produce grown in them would the risk exceed the limits of acceptabilit

Quantitative Health Risk Assessment of Metals on Surfaces Using the Construction Industry as a Test Environment

Routes of human exposure to hazardous substances include inhalation, ingestion, skin, and eye contact. To protect worker health against airborne contaminants numerous occupational exposure limit values (OELVs) have been established by regulatory or health authorities. These limits are airborne concentrations of hazardous substances which are often established as health-based benchmarks according to epidemiological and toxicological evaluations. OELVs have exclusively focused on the inhalation exposure pathway because it has been considered the most important route of exposure (Anderson & Meade 2014; Schneider et al. 1999). In contrast, there is a lack of quantitative exposure limits to assess skin exposures in the workplace. A research gap with respect to the development of health-based skin exposure limits for metals was identified. This thesis addressed two main research questions; (1) What methods should be employed to measure skin exposure to metals? (2) What is an acceptable skin exposure limit to metals using the construction industry, where there is a high prevalence of occupational skin exposures, as a test environment

Modeling contaminant transport and fate and subsequent impacts on ecosystems

Assessing risks associated with the release of metals into the environment and managing remedial activities requires simulation tools that depict speciation and risk with accurate mechanistic models and well-defined transport parameters. Such tools need to address the following processes: (1) aqueous speciation, (2) distribution mechanisms, (3) transport, and (4) ecological risk. The primary objective of this research is to develop a simulation tool that accounts for these processes. Speciation in the aqueous phase can be assessed with geochemical equilibrium models, such as MINEQL+. Furthermore, metal distribution can be addressed mechanistically. Studies with Pb sorption to amorphous aluminum (HAG), iron (HFO), and manganese (HMO) oxides, as well as oxide coatings, demonstrated that intraparticle diffusion is the rate-limiting mechanism in the sorption process, where best-fit surface diffusivities ranged from 10-18 to 10-15 cm2 s-1 Intraparticle surface diffusion was incorporated into the Groundwater Modeling System (GMS) to accurately simulate metal contaminant mobility where oxides are present. In the model development, the parabolic concentration layer approximation and the operator split technique were used to solve the microscopic diffusion equation coupled with macroscopic advection and dispersion. The resulting model was employed for simulating Sr90 mobility at the U.S. Department of Energy (DOE) Hanford Site. The Sr90 plume is observed to be migrating out of the 100-N area extending into other areas of the Hanford Site and beyond. Once bioavailability is understood, static or dynamic ecological risk assessments can be conducted. Employing the ERA model, a static ecological risk assessment for exposure to depleted uranium (DU) at Aberdeen and Yuma Proving Grounds (APG and YPG) revealed that a reduction in plant root weight is considered likely to occur. For most terrestrial animals at YPG, the predicted DU dose is less than that which would result in a decrease in offspring. However, for the lesser long-nosed bat, reproductive effects are expected to occur through the reduction in size and weight of offspring. At APG, based on very limited data, it is predicted that uranium uptake will not likely affect survival of terrestrial animals and aquatic species. In model validation, sampling of pocket mice, kangaroo rat, white-throated woodrat, deer, and milfoil showed that body burden concentrations fall into the distributions simulated at both sites. This static risk assessment provides a solid background for applying the dynamic approach. Overall, this research contributes to a holistic approach in developing accurate mechanistic models for simulating metal contaminant mobility and bioavailability in subsurface environments

Assessing the state of rainwater for consumption in a community in dire need of clean water: Human and health risk using HERisk

This study examines the case of Ekpoma community, Edo State, Nigeria, where roof-harvested rainwater is the primary source of water for drinking and domestic purposes. Eight potentially toxic elements (PTEs), namely aluminum, chromium, copper, iron, manganese, nickel, lead, and zinc, were detected in rainwater samples, collected and analyzed from 54 sampling locations across the community. The elemental concentrations were quantified using atomic absorption spectrophotometry and compared using the regulatory standards of the World Health Organization, United States Environmental Protection Agency, and Nigerian Drinking Water Quality Standards. The PTEs detected in the rainwater samples can be attributed to the nature of the materials used in the roof catchment systems, storage tank conditions, anthropogenic effects from industrial and agricultural processes, and fossil fuel emissions. However, only 20% of the evaluated samples contained PTE concentrations below the allowable regulatory limits. Spatio-temporal health risk analysis conducted using HERisk software showed that children in the development phase (1–18 years) are most vulnerable to health risks in the community. After age 18, the risk increased by approximately 10% and remained constant until old age. In addition, the evaluation of the studied sites showed that 33% of the evaluated sites had negligible carcinogenic risks, while the other 61% were sites with low carcinogenic risks to residents

Soil contamination in China : studies on the status, priorities, policies, management and risk assessment

As China is trying to balance economic development, environmental safety and human health, the Government has released strategic plans and legislation for soil contamination management. Aspects of the quality of China’s soils and management of soil contamination in China are addressed in this thesis. Soil environmental quality standards and science-based risk assessment of contaminants in soils are evaluated. China and the UK use different risk-based approaches to derive soil screening or guideline values (SSVs; SGVs) for contaminants. The approaches are compared and values derived for 6 illustrative contaminants. China’s SSVs are derived using an approach developed in the US as follows: for carcinogens, acceptable level of risk (ACR) is set at 10-6 and the SSVs calculated as 10-6 divided by the soil exposure and toxicity data; for non-carcinogens, the hazard quotient is 1 and the SSV is calculated as 1 divided by the soil exposure and toxicity data. The UK’s SGVs are calculated by the CLEA model, for which the Average Daily Exposure (ADE) from soil sources by a specific exposure route equals the health criteria values (HCVs) for that route, whether for carcinogens or a non-carcinogens. The UK’s CLEA model is also used here to derive SSVs with Chinese input parameters. China’s SSVs, the UK’s SGVs and values for Chinese conditions derived using the UK approach were as follows (mg/kg): As, <1, 35, 20; Cd, 20, 18, 11; Cr (VI), <1, 14, 29; benzene, 1, 1, 2; toluene, 1200, 3005, 3800; ethyl-benzene, 7, 930, 1200. The difference in toxicity assessment and risk characterization for carcinogens results in the biggest difference in SSVs between the 2 countries. However, for non-carcinogenic substances, the difference of SSVs calculation method and SSVs is small. In the future, China can use the UK method to strengthen its toxicity assessment and risk characterization for carcinogenic substances. Data was made available for this thesis from an extensive field and analytical campaign of human exposure to heavy metals in China. This was used to calculate the relative contributions of exposure to As, Cd, Cr, Hg and Pb from environmental media (air, water, soils) via the inhalation, drinking and the diet for different regions of China. Dietary exposure dominated, contributing ~90-97% of the total exposure for these elements. Exposure differences were observed with gender, age and region. This survey information can be used to derive exposures from soil-borne sources. Soil organic matter (SOM) and pH are critical soil properties strongly linked to carbon storage, nutrient cycling and crop productivity, but there is a lack of information on changes in these soil properties over time for China. This study used data from Chinese soil surveys to examine changes in soil pH and SOM across different land uses (dry farmland, paddy fields, grassland, woodland, unused land), with surface soil (0-20 cm) collected in the periods 1985-90 (Survey 1; 890 samples) and 2006-10 (Survey 2; 5005 samples) from two contrasting areas. In the southern part of China, the mean pH of paddy soils fell over the two decades between surveys - from pH 5.81 to 5.19 (p<0.001), while dry farmlands in the northern sampling area fell slightly (from pH 8.15 to 7.82; p<0.001). The mean SOM content of dry farmland soil rose in both areas and the mean SOM of paddy fields in the southern area also rose (all p<0.001). Woodland soil pH in the south increased from 4.71 to 5.29 (p<0.001) but no significant difference was measured in the woodlands of the northern area, although the trend increased. The SOM content of woodland top soils rose in the northern (p=0.003) and southern (p<0.001) study areas. The implications and potential causes of these changes are discussed and suggestions made as to how large-scale soil sampling campaigns can be designed to monitor for changes and potential controlling factors. Because of rapid urbanization in China, the demand for land for urban development is increasing. To upgrade and modernize, China has also moved many major industries and factories from urban centres to less populated areas. With the high economic value of urban land, the transformation and utilization of the brownfield areas left behind has become important economically and socially. Strong scientific, regulatory and decision-making frameworks are needed, to ensure practical, careful and wise use of central and local Government resources, to manage the re-use and regeneration of these brownfield sites. The final chapter provides a thorough review of the background, context, regulations, policies and management procedures to develop and utilize brownfields in developed countries such as the US and UK, and identifies some of the priorities for brownfield governance and redevelopment in China. It is proposed: to establish a monitoring body, to identify shared responsibilities and inputs of various stakeholders, to establish brownfield databases, and to set up a remediation advisory system with technology support as future priorities of brownfield management. Recommendations are made for future research, to support China’s strategic management of soil resources

Tungsten

prepared by Syracuse Research Corporation under contract no. 205-1999-00024 ; prepared for U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry."August 2005."Chemical manager(s)/author(s): Sam Keith ... [et al.]--P. ix."A toxicological profile for tungsten , draft for public comment was released in September 2003. This edition supersedes any previously released draft or final profile"--P. iii."This toxicological profile is prepared in accordance with guidelines developed by the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA). The original guidelines were published in the Federal Register on April 17, 1987"--P. v.Also available via the World Wide Web.Includes bibliographical references (p. 131-156) and index