Engaging One Health in Heavy Metal Pollution in Some Selected Nigerian Niger Delta Cities. A Systematic Review of Pervasiveness, Bioaccumulation and Subduing Environmental Health Challenges.

The Niger Delta environment is under serious threat due to heavy metal pollution. Many studies have been conducted on the heavy metal contamination in soils, water, seafood and plants in the Niger Delta ecosystem. However, there is a lack of clear understanding of the health consequences for people and strategies for attaining One Health, and a dispersion of information that is accessible. The study focused on investigating the contamination levels, distributions, risks, sources and impacts of heavy metals in selected regions of the Niger Delta. Prior studies revealed that the levels of certain heavy metals, including Cd, Pb, Cu, Cr, Mn, Fe and Ni, in water, sediment, fish and plants in most Niger Delta ecosystems were higher than the acceptable threshold attributed to various anthropogenic stressors. In the reviewed Niger Delta states, ecosystems in Rivers state showed the highest concentrations of heavy metals in most sampled sites. Groundwater quality was recorded at concentrations higher than 0.3 mg/L World Health Organization drinking water guideline. High concentrations of copper (147.915 mg/L) and zinc (10.878 mg/L) were found in Rivers State. The heavy metals concentrations were greater in bottom-dwelling organisms such as bivalves, gastropods and shrimp than in other fishery species. Heavy metal exposure in the region poses risks of communicable and non-communicable diseases. Diverse remediation methods are crucial to reduce contamination levels, but comprehensive strategies and international cooperation are essential to address the health hazards. Actively reducing heavy metals in the environment can achieve One Health objectives and mitigate disease and economic burdens.

An Update Overview on Mechanistic Data and Biomarker Levels in Cobalt and Chromium-Induced Neurodegenerative Diseases.

There is increasing evidence that the imbalance of metals as cobalt (Co) and chromium (Cr) may increase the risk of development and progression of neurodegenerative diseases (NDDs). The human exposure to Co and Cr is derived mostly from industry, orthopedic implants, and polluted environments. Neurological effects of Co and Cr include memory deficit, olfactory dysfunction, spatial disorientation, motor neuron disease, and brain cancer. Mechanisms of Co and Cr neurotoxicity included DNA damage and genomic instability, epigenetic changes, mitochondrial disturbance, lipid peroxidation, oxidative stress, inflammation, and apoptosis. This paper seeks to overview the Co and Cr sources, the mechanisms by which these metals induce NDDs, and their levels in fluids of the general population and patients affected by NDDs. To this end, evidence of Co and Cr unbalance in the human body, mechanistic data, and neurological symptoms were collected using in vivo mammalian studies and human samples.

The endocrine disrupting effects of nanoplastic exposure: A systematic review.

Good mechanical properties and low costs have led to a global expansion of plastic production and use. Unfortunately, much of this material can be released into the environment as a waste product and cleaved into micro- and nanoplastics (NPs) whose impact on the environment and human health is still largely unknown. Considering the growing worldwide awareness on exposure to chemicals that can act as endocrine disruptors, a systematic review was performed to assess the impact of NPs on the endocrine function of in vitro and in vivo models. Although a limited number of investigations is currently available, retrieved findings showed that NPs may induce changes in endocrine system functionality, with evident alterations in reproductive and thyroid hormones and gene expression patterns, also with a trans-generational impact. Nanoplastic size, concentration, and the co-exposure to other endocrine disrupting pollutants may have an influencing role on these effects. Overall, although it is still too early to draw conclusions regarding the human health risks derived from NPs, these preliminary results support the need for further studies employing a wider range of plastic polymer types, concentrations, and time points as well as species and life stages to address a great variety of endocrine outcomes and to achieve a broader and shared consensus on the role of NPs as endocrine disruptors.

Potentially harmful elements released by volcanic ash of the 2021 Tajogaite eruption (Cumbre Vieja, La Palma Island, Spain): Implications for human health.

This study assesses the potential impacts on human health of volcanic ash emitted during the 2021 Tajogaite eruption (La Palma Island, Spain). Ash samples were physically and chemically characterized and leaching tests (with deionized water and acidic solution) were performed according to the IVHHN protocols to elucidate i) the leachable elements that may affect water quality and represent a potential threat for livestock and humans through drinking water supply; and ii) the bioaccessible fraction of toxicants able to be solubilized from ash surfaces if ashes are incidentally ingested by children. The most abundant readily water-soluble compounds were SO4, F, Cl, Na, Ca, Ba, Mg, and Zn. Fluoride and chloride (up to 1085 and 1347 mg/kg) showed higher values in distal ash samples than closer ones. The potential F availability assessed from water leachates may suggest important environmental and health implications. In addition, long-term health hazard due to a long-term weathering of tephra deposits should be possible as confirmed by the greater amount of F extracted by acidic solution. Concentration of other trace elements (e.g., As, V, Mn, Mo, Cr, Fe, Se, Ti, Pb) were low compared to global medians and within the range globally assessed. Indicative calculation of hazard for water supply showed that F concentration may exceed both the recommended value (1 mg/L) for irrigation purpose and the health-based drinking water limits of 1.5 mg/L (for humans) and 2 mg/L (for livestock). If the predicted concentrations in water were compared with the toxicologically dose, F showed a potential health-risk for children through drinking water. The indicative health-risk characterization via accidental ash ingestion showed that the direct exposure does not represent a primary source of F daily intake for children. This important outcome confirmed F as element with the greatest health threat during Tajogaite 2021 eruption.

Heavy metals and inflammatory, oxidative/antioxidant and DNA damage biomarkers among people living with HIV/AIDS (PLWHA) in Niger Delta, Nigeria.

This study evaluated the association of heavy metals (HMs) and effect biomarkers (inflammation, oxidative stress/antioxidant capacity and DNA damage) among people living with HIV/AIDS (PHWHA) in Niger Delta area, Nigeria. Blood levels of lead (BPb), cadmium (BCd), copper (BCu), zinc (BZn), iron (BFe), C-reactive protein (CRP), Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), Interferon-γ (IFN-γ), Malondialdehyde (MDA), Glutathione (GSH) and 8-hydroxy-2-deoxyguanosine (8-OHdG) were determined in a total of 185 participants, 104 HIV-positive and 81 HIV-negative sampled in both Niger Delta and non-Niger Delta regions. BCd (p < 0.001) and BPb (p = 0.139) were higher in HIV-positive subjects compared to HIV-negative controls; on the contrary, BCu, BZn and BFe levels were lower (p < 0.001) in HIV-positive subjects compared to HIV-negative controls. The Niger Delta population had higher levels of heavy metals (p < 0.01) compared to non-Niger Delta residents. CRP and 8-OHdG were higher (p < 0.001) in HIV-positive than in HIV-negative subjects and in Niger-Delta than in non-Niger Delta residents. BCu had significant positive dose-response relationship with CRP (61.9%, p = 0.063) and GSH (1.64%, p = 0.035) levels in HIV-positive subjects, and negative response with MDA levels (26.6%, p < 0.001). Periodic assessment of HMs levels among PLWHA is recommended.

HBM4EU chromates study - the measurement of hexavalent and trivalent chromium in exhaled breath condensate samples from occupationally exposed workers across Europe.

The aim of this study was to investigate the practicability of exhaled breath condensate (EBC) as a biological matrix to detect and measure hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) in workers occupationally exposed to Cr(VI). EBC samples were collected from workers in France, Finland, Italy, The Netherlands and the United Kingdom from three different target activities: chrome platers, stainless steel welders and surface treatment workers. Pre and post working week EBC samples were collected from 177 exposed workers and 98 unexposed workers (control group). Hyphenated chromatography systems with inductively coupled plasma - mass spectrometry (ICP-MS) were for the analysis. The results showed that the occupationally exposed workers had significantly higher levels of Cr(VI) and Cr(III) than the control group. Chrome platers exhibited the highest Cr(VI) levels in their EBC samples, with a significant increase from their pre to post samples for both Cr(VI) and Cr(III). A significant difference was also found between pre and post EBC samples for Cr(III) in welders. This study has shown that EBC has the potential to be a valid, non-invasive biological matrix to assess occupational exposure to Cr(VI) and Cr(III) for biological monitoring assessment, with the ability to detect low level inhalation exposures.

The HBM4EU chromates study - Outcomes and impacts on EU policies and occupational health practices.

Within the EU human biomonitoring initiative (HBM4EU), a targeted, multi-national study on occupational exposure to hexavalent chromium (Cr(VI)) was performed. Cr(VI) is currently regulated in EU under REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) and under occupational safety and health (OSH) legislation. It has recently been subject to regulatory actions to improve its risk management in European workplaces. Analysis of the data obtained within the HBM4EU chromates study provides support both for the implementation of these regulatory actions and for national enforcement programs and may also contribute to the updating of occupational limit values (OELs) and biological limit values for Cr(VI). It also provides useful insights on the contribution of different risk management measures (RMMs) to further reduce the exposure to Cr(VI) and may support the evaluation of applications for authorisation under REACH. Findings on chrome platers' additional per- and polyfluoroalkyl substances (PFAS) exposure highlight the need to also pay attention to this substance group in the metals sector. A survey performed to evaluate the policy relevance of the HBM4EU chromates study findings supports the usefulness of the study results. According to the responses received from the survey, the HBM4EU chromates study was able to demonstrate the added value of the human biomonitoring (HBM) approach in assessment and management of occupational exposure to Cr(VI). For future occupational studies, we emphasise the need for engagement of policy makers and regulators throughout the whole research process to ensure awareness, relevance and uptake of the results in future policies.

Exposure to heavy metals and red blood cell parameters in children: A systematic review of observational studies.

Background: Mechanistic studies show that heavy metals interfere with the hematopoietic system by inhibiting key enzymes, which could lead to anemia. However, the link between children's exposure and red blood cell (RBC) parameters has been inconsistent. We aimed to summarize evidence on human studies exploring the association between exposure to lead, mercury, cadmium, arsenic, and chromium VI and RBC parameters in children. Methods: Following the PRISMA guidelines, we searched PubMed, Scopus, and Web of Science databases for studies published between January 2010 and April 2022. Eligible papers included human observational studies that directly assessed exposure (internal dose) to the heavy metals under study and RBC parameters in participants aged ≤ 18 years. We excluded studies using hospital-based samples. Study quality was assessed using the National Institutes of Health's Quality Assessment Tools for Cohort and Cross-Sectional Studies. We synthesized the evidence using vote counting based on the direction of the relationship. Results: Out of 6,652 retrieved papers, we included a total of 38 (33 assessing lead, four mercury, two cadmium, and two arsenic; chromium VI was not assessed in any included paper). More than half of the studies were conducted in Asia. We found evidence of a positive relationship between lead concentration and hemoglobin (proportion of studies reporting negative relationships = 0.750; 95% Confidence Interval (CI) 0.583, 0.874) and mean corpuscular hemoglobin (0.875; 95% CI 0.546, 0.986), and a positive relationship with red cell distribution width (0.000; 95%CI 0.000, 0.379). When considering only good-quality studies (24% of the Pb studies), only the relationship with hemoglobin levels remained (0.875; 95% CI: 0.546, 0.986). Conclusion: We found evidence of a negative relationship between lead concentration and hemoglobin and mean corpuscular hemoglobin and of a positive relationship with red cell distribution width in children. We also identified a need to conduct more studies in European countries. Future studies should use standardized practices and make efforts to increase study quality, namely by conducting comprehensive longitudinal studies. Our findings support the need to take further actions to limit heavy metal exposure during childhood.

Mechanistic considerations and biomarkers level in nickel-induced neurodegenerative diseases: An updated systematic review.

The environment has been implicated to be a strong determinant of brain health with higher risk of neurodegeneration. The drastic rise in the prevalence of neurodegenerative diseases (NDDs) including Alzheimer's disease (AD), Parkinson's disease (PD), autism spectrum disorder (ASD), multiple sclerosis (MS) etc., supports the idea that environmental factors may play a major role in NDDs aetiology. Nickel is one of the listed environmental metals reported to pose a serious threat to human health. This paper reported available studies on nickel level in NDDs covering both animal and human studies. Different databases were searched for articles reporting the main neurotoxicity mechanisms and the concentration of nickel in fluids and tissues of NDDs patients compared to controls. Data were extracted and synthesized by ensuring the articles were related to nickel and NDDs. Various mechanisms were reported as oxidative stress, disturbances in mitochondrial membrane potential, trace elements homeostasis destabilization, etc. Nickel was found elevated in biological fluids as blood, serum/plasma and CSF and in the brain of NDDs, as a consequence of unintentional exposure thorough nickel-contaminated air, food, water, and skin contact. In addition, after exposure to nickel, the concentration of markers of lipid peroxidation were increased, while some antioxidant defence systems decreased. Thus, the reduction in the exposure to nickel contaminant may hold a promise in reducing the incidence of NDDs.

HBM4EU chromates study - Usefulness of measurement of blood chromium levels in the assessment of occupational Cr(VI) exposure.

Occupational exposures to hexavalent Chromium (Cr(VI)) can occur in welding, hot working stainless steel processing, chrome plating, spray painting and coating activities. Recently, within the human biomonitoring for Europe initiative (HBM4EU), a study was performed to assess the suitability of different biomarkers to assess the exposure to Cr(VI) in various job tasks. Blood-based biomarkers may prove useful when more specific information on systemic and intracellular bioavailability is necessary. To this aim, concentrations of Cr in red blood cells (RBC-Cr) and in plasma (P-Cr) were analyzed in 345 Cr(VI) exposed workers and 175 controls to understand how these biomarkers may be affected by variable levels of exposure and job procedures. Compared to controls, significantly higher RBC-Cr levels were observed in bath plating and paint application workers, but not in welders, while all the 3 groups had significantly greater P-Cr concentrations. RBC-Cr and P-Cr in chrome platers showed a high correlation with Cr(VI) in inhalable dust, outside respiratory protective equipment (RPE), while such correlation could not be determined in welders. In platers, the use of RPE had a significant impact on the relationship between blood biomarkers and Cr(VI) in inhalable and respirable dust. Low correlations between P-Cr and RBC-Cr may reflect a difference in kinetics. This study showed that Cr-blood-based biomarkers can provide information on how workplace exposure translates into systemic availability of Cr(III) (extracellular, P-Cr) and Cr(VI) (intracellular, RBC-Cr). Further studies are needed to fully appreciate their use in an occupational health and safety context.

E-WASTE threatens health: The scientific solution adopts the one health strategy.

The aggressively extractive advanced technology industry thrives on intensive use of non-renewable resources and hyper-consumeristic culture. The environmental impact of its exponential growth means extreme mining, hazardous labour practices including child labour, and exposure burden to inorganic and organic hazardous chemicals for the environment and current and future human generations. Globally, processes such as in-country reduce, reuse and recycle have so far received less attention than outer-circle strategies like the uncontrolled dumping of e-waste in countries that are unprotected by regulatory frameworks. Here, in the absence of infrastructures for sound hazardous e-waste management, the crude recycling, open burning and dumping into landfills of e-waste severely expose people, animal and the environment. Along with economic, political, social, and cultural solutions to the e-waste global problem, the scientific approach based on risk analysis encompassing risk assessment, risk management and risk communication can foster a technical support to resist transgenerational e-waste exposure and health inequalities. This paper presents the latest public health strategies based on the use of integrated human and animal biomonitoring and appropriate biomarkers to assess and manage the risk of e-waste embracing the One Health approach. Advantages and challenges of integrated biomonitoring are described, along with ad-hoc biomarkers of exposure, effect and susceptibility with special focus on metals and metalloids. Indeed, the safe and sustainable management of novel technologies will benefit of the integration and coordination of human and animal biomonitoring.

Environmental Substances Associated with Chronic Obstructive Pulmonary Disease-A Scoping Review.

Chronic obstructive pulmonary disease (COPD) is a slowly developing non-communicable disease (NCD), causing non-reversible obstruction and leading to marked morbidity and mortality. Besides traditional risk factors such as smoking, some environmental substances can augment the risk of COPD. The European Human Biomonitoring Initiative (HBM4EU) is a program evaluating citizens' exposure to various environmental substances and their possible health impacts. Within the HBM4EU, eighteen priority substances or substance groups were chosen. In this scoping review, seven of these substances or substance groups are reported to have an association or a possible association with COPD. Main exposure routes, vulnerable and high-exposure risk groups, and matrices where these substances are measured are described. Pesticides in general and especially organophosphate and carbamate insecticides, and some herbicides, lead (Pb), and polycyclic aromatic hydrocarbons (PAHs) showed an association, and cadmium (Cd), chromium (Cr and CrVI), arsenic (As), and diisocyanates, a possible association with COPD and/or decreased lung function. Due to long latency in COPD's disease process, the role of chemical exposure as a risk factor for COPD is probably underestimated. More research is needed to support evidence-based conclusions. Generally, chemical exposure is a growing issue of concern, and prompt action is needed to safeguard public health.

HBM4EU Chromates Study: Determinants of Exposure to Hexavalent Chromium in Plating, Welding and Other Occupational Settings.

Work-related exposures in industrial processing of chromate (chrome plating, surface treatment and welding) raise concern regarding the health risk of hexavalent chromium (Cr(VI)). In this study, performed under the HBM4EU project, we focused on better understanding the determinants of exposure and recognising how risk management measures (RMMs) contribute to a reduction in exposure. HBM and occupational hygiene data were collected from 399 workers and 203 controls recruited in nine European countries. Urinary total chromium (U-Cr), personal inhalable and respirable dust of Cr and Cr(VI) and Cr from hand wipes were collected. Data on the RMMs were collected by questionnaires. We studied the association between different exposure parameters and the use of RMMs. The relationship between exposure by inhalation and U-Cr in different worker groups was analysed using regression analysis and found a strong association. Automatisation of Cr electroplating dipping explained lower exposure levels in platers. The use of personal protective equipment resulted in lower U-Cr levels in welding, bath plating and painting. An effect of wearing gloves was observed in machining. An effect of local exhaust ventilation and training was observed in welding. Regression analyses showed that in platers, exposure to air level of 5 µg/m3 corresponds to U-Cr level of 7 µg/g creatinine. In welders, the same inhalation exposure resulted in lower U-Cr levels reflecting toxicokinetic differences of different chromium species.

Human dietary exposure to metals in the Niger delta region, Nigeria: Health risk assessment.

The contamination profile and the human health risk assessment of various heavy metals (Cd, Cr, Mn, Ni and Pb) in vegetable oils, palm oils, butter and shea butter purchased from the Nigerian market were evaluated. Univariate and multivariate analyses including the principal component analysis (PCA), hierarchical cluster analysis (HCA) and heat map visualization were used to evaluate correlation, similarity and source of metals. Dietary intake and dermal absorption through the application in skin were also assessed. The heavy metals 5th and 95th percentile interval range (in mg/kg) were 0.003-0.208, 0.003-0.392, 0.003-1.344, 0.003-0.369 and 0.006-0.531 for Cd, Cr, Mn, Ni and Pb, respectively. Concentrations of Cr and Mn were significantly different across sample categories, being the levels of Mn and Ni positively correlated in both oil and butter samples. The result of PCA, HCA and heat map revealed the profile of heavy metals in oils was different from that of butters, with Pb mainly associated to oils, and Cd, Cr, Mn and Ni to butters. In some samples, the international maximum levels for Cd, Ni and Pb in edible oils were exceeded. Cadmium and Pb dietary intake through Nigerian oils and butters should not be considered negligible for human health protection.

HBM4EU chromates study - Overall results and recommendations for the biomonitoring of occupational exposure to hexavalent chromium.

Exposure to hexavalent chromium [Cr(VI)] may occur in several occupational activities, e.g., welding, Cr(VI) electroplating and other surface treatment processes. The aim of this study was to provide EU relevant data on occupational Cr(VI) exposure to support the regulatory risk assessment and decision-making. In addition, the capability and validity of different biomarkers for the assessment of Cr(VI) exposure were evaluated. The study involved nine European countries and involved 399 workers in different industry sectors with exposures to Cr(VI) such as welding, bath plating, applying or removing paint and other tasks. We also studied 203 controls to establish a background in workers with no direct exposure to Cr(VI). We applied a cross-sectional study design and used chromium in urine as the primary biomonitoring method for Cr(VI) exposure. Additionally, we studied the use of red blood cells (RBC) and exhaled breath condensate (EBC) for biomonitoring of exposure to Cr(VI). Personal measurements were used to study exposure to inhalable and respirable Cr(VI) by personal air sampling. Dermal exposure was studied by taking hand wipe samples. The highest internal exposures were observed in the use of Cr(VI) in electrolytic bath plating. In stainless steel welding the internal Cr exposure was clearly lower when compared to plating activities. We observed a high correlation between chromium urinary levels and air Cr(VI) or dermal total Cr exposure. Urinary chromium showed its value as a first approach for the assessment of total, internal exposure. Correlations between urinary chromium and Cr(VI) in EBC and Cr in RBC were low, probably due to differences in kinetics and indicating that these biomonitoring approaches may not be interchangeable but rather complementary. This study showed that occupational biomonitoring studies can be conducted successfully by multi-national collaboration and provide relevant information to support policy actions aiming to reduce occupational exposure to chemicals.

Arsenic and toxic metals in meat and fish consumed in Niger delta, Nigeria: Employing the margin of exposure approach in human health risk assessment.

This study provides information on the health risk of As, Cd, Hg, Pb and V exposure from Nigerian foods consumption (fish, cow, goat and chicken meat) in different age-groups (children, adolescent, adult, senior) and six areas of Niger Delta, Nigeria (Choba, Khana, Eleme, TransAmadi, Uyo, and Yenogoa). The health risk assessment was performed by estimating the weekly or monthly intake of metals from foods and Margin of Exposure (MOE) approach by using established benchmark dose levels (BMDLs). Regarding As, cow and chicken meat products contributed to As exposure intake especially in children resulting in values higher than BMDL0.1 for cancer risk in TransAmadi and Uyo areas. Cadmium exposure was due to cow, chicken and goat meat ingestion mostly in adolescent above the tolerable monthly intake limit in TransAmadi and Uyo areas. Concerning Hg and V, the exposure from Nigerian food did not constitute a potential health hazard. Lead exposure in children were above or close to BMDL0.1 for developmental neurotoxicity by ingestion of cow and goat meat in all the Nigerian areas. In adult and senior the Pb dietary exposure were above the BMDL10 providing a low to negligible risk for kidney effects. The potential concern for health effects in Niger Delta population needs further efforts to decrease As, Cd and Pb dietary exposure especially for children and adolescent, who are more vulnerable to adverse life events.

Concentrations of polycyclic aromatic hydrocarbons in samples of soil, feed and food collected in the Niger Delta region, Nigeria: A probabilistic human health risk assessment.

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed compounds with two or more fused aromatic ring, being some of them classified as carcinogenic. In the present study, the concentrations of 16 PAHs and the sum of them (∑PAHs) were determined in samples of food, feed, plant and soil collected in six different heavily polluted areas (Choba, Khana, Trans Amadi, Eleme, Uyo and Yenagoa) of the Niger Delta Region (Nigeria). Principal component analysis (PCA) was then used to identify groups of variables (PAHs) and groups of samples that were the best in rendering the environmental pollution in that Region of Nigeria. In addition, PAHs food consumption and the derived carcinogenic risks were assessed in a probabilistic way. The highest ∑PAHs (mg/kg) were: 16.7 in cow meat, 8.06 in goat meat, 25.4 in chicken meat, 7.72 in fish, 28.70 in fish feed, 15.3 in chicken feed, 8.42 in plant, and 8.80 in soil. In most of the Nigerian areas, cooked cow meat, chicken and chicken feed presented the highest impact regarding PAHs contamination. The highest intake of PAHs was through meat consumption, with a very high and unassumable carcinogenic risk, which is quite above 10-5 for some PAHs, including benzo [a]pyrene. The results of the present survey highlight the importance of reducing PAHs content in food, specially in meat, in the Niger Delta region.

Trace elements exposure and risk in age-related eye diseases: a systematic review of epidemiological evidence.

This systematic review aimed to evaluate existing evidence on the associations between trace elements exposure and age-related eye diseases. PubMed and Google scholar databases were searched for epidemiological and postmortem studies on the relationship between exposure to trace elements and Age-related eye diseases such as age-related macular degeneration (AMD), cataract, glaucoma and diabetic retinopathy (DR), in population groups aged 40 years and above. Available evidence suggests that cadmium (Cd) exposure may be positively associated with the risks of AMD and cataract. There is also evidence that exposure to lead (Pb) may be positively associated with higher risk of cataract and glaucoma. There is limited number of relevant studies and lack of prospective studies for most of the investigated associations. Evidence for other trace elements is weak and inconsistent, and the number of available studies is small. Likewise, there are very few relevant studies on the role of trace elements in DR. Chemical elements that affect the distribution and absorption of other trace elements have never been investigated. The suggestive but limited evidence motivates large and quality prospective studies to fully characterize the impact of exposure to trace (toxic and essential) elements on age-related eye diseases.

Metal pollution of soil, plants, feed and food in the Niger Delta, Nigeria: Health risk assessment through meat and fish consumption.

This study was aimed at determining mainly the concentrations of As and other metals (Cd, Cu, Hg, Pb, V and Zn) in samples of feed, soil, plants and foods (fish, chicken, goat and cow meat) grown and consumed in six areas of Niger Delta, Nigeria (Choba, Khana, Trans Amadi, Eleme, Uyo and Yenagoa). Principal Component Analysis (PCA) models were used for identifying groups of variables (i.e., elements) based on the loadings and groups of samples (i.e., plants, soil, fish, meet, feed) according to the scores that contributed most to the environmental pollution in each Nigerian area. In Choba and Khana sites, the results showed a cluster of elements like As, Pb, V and Zn, mostly associated with samples of goat and cow meat, as well as soils, and separated from another cluster of metals composed by Cu and Hg with different origin. In Trans Amadi area, a clustering of As, Cd and V was found associated to different types of meat (chicken, goat, and cow) located in the opposite side of Cu and Hg, which correlated to plants and soil. In Eleme, the strongest loadings were obtained for V and Zn associated with soil and meat (goat and cow) samples and separated from As and Cd. Finally, in Uyo and Yenagoa, dominant elements were As, Cu, Pb and Zn, with proximity to cow and goat liver samples, while Cd and V corresponded to a different pollution pattern. Lead intake trough meat and fish consumption for adults and children were much higher than the tolerable limits set by international organizations. The results of this study should allow a better understanding of the complex phenomenon of metal pollution in the feed-to-food chain and human health in Nigeria, which should help to manage a pollution reduction strategy and give priorities of research and monitoring.

Challenges to Evidence Synthesis and Identification of Data Gaps in Human Biomonitoring.

The increasing number of human biomonitoring (HBM) studies undertaken in recent decades has brought to light the need to harmonise procedures along all phases of the study, including sampling, data collection and analytical methods to allow data comparability. The first steps towards harmonisation are the identification and collation of HBM methodological information of existing studies and data gaps. Systematic literature reviews and meta-analyses have been traditionally put at the top of the hierarchy of evidence, being increasingly applied to map available evidence on health risks linked to exposure to chemicals. However, these methods mainly capture peer-reviewed articles, failing to comprehensively identify other important, unpublished sources of information that are pivotal to gather a complete map of the produced evidence in the area of HBM. Within the framework of the European Human Biomonitoring Initiative (HBM4EU) initiative-a project that joins 30 countries, 29 from Europe plus Israel, the European Environment Agency and the European Commission-a comprehensive work of data triangulation has been made to identify existing HBM studies and data gaps across countries within the consortium. The use of documentary analysis together with an up-to-date platform to fulfil this need and its implications for research and practice are discussed.