Environmental lead exposure and its relationship to traffic density among Senegalese children: a cross-sectional study

Sources of Lead Exposure in West Africa

This commentary is an investigation of sources of lead (Pb) exposure in West Africa. Pb is generally acknowledged as one of the most widespread environmental health hazards in West Africa, and there is heightened concern over adverse health effects at various levels of exposure (at doses once considered safe) in the West African region. A literature review for the possible health implications of Pb exposure on human health showed nervous system dysfunction, anemia, and potential cognitive diseases as the major health issues among children, while adults were found to suffer more from cardiovascular dysfunction, neurological decline, and reproductive diseases. Despite a decline in blood lead levels (BLLs), lead exposure continues to be a major public health concern as no level of Pb exposure can be considered safe. Moreover, lowering BLLs entails identifying various lead sources such as gasoline emissions, leaded paint, canned foods, and beverages, as well as plausible biological pathways of lead exposure and response. However, only countries such as Nigeria and Ghana have extensive research available regarding the different sources of Pb exposure. Further, it is not apparent which country is affected the most by Pb exposure. Therefore, this commentary was aimed to explore different literature sources to describe and list the different sources of Pb exposure in 15 West African countries. The findings indicated water, food, and occupational exposure as the major sources of Pb exposure in the region. People with occupations such as e-waste and Pb acid battery recycling, auto mechanics, fuel attending, welding, electronic repairing, farming/spraying, and mining were found to be at immediate risk. Tobacco, spices and paints constituted additional potential sources of exposure. For residents living near landfills or urban area, the major sources of Pb exposure were soil, air, and dust particles. The review revealed a vast research gap on the sources and implications of Pb exposure. Exposure to Pb could further increase due to uncontrolled traffic, urban growth, inadequate urban planning, and the inadequate enforcement of regulations. Therefore, more extensive research on the changing trends of Pb exposure among West African populations is needed.

Metal exposure and oxidative stress biomarkers in a Brazilian agricultural community

We examined the association between exposure to metals, metalloids, and oxidative stress biomarkers among rural community residents in Brazil. Multiple linear regression was used to evaluate associations between serum metal and metalloid concentrations and blood oxidative stress biomarkers, adjusting for sex, age, education, smoking, and alcohol use. After adjustment for covariates, glutathione peroxidase activity (GPx) was inversely and significantly associated with an increase in serum arsenic (As) levels. Positive and significant associations were seen between elevated glutathione reductase (GR) activity and serum cadmium (Cd), barium (Ba), and lead (Pb) concentrations. In addition, we observed a significant increase in malondialdehyde (MDA) levels in association with an increase in Ba levels. These findings suggest that toxic metals and metalloids such as As, Ba, Cd, and Pb alter antioxidant enzyme activities. In addition, Ba seems to promote lipid peroxidation.

The Relation Between Low-Level Lead Exposure and Oxidative Stress: a Review of the Epidemiological Evidence in Children and Non-Occupationally Exposed Adults

Experimental studies in animals and observational studies in occupationally exposed adults indicate that higher lead exposure results in higher biomarkers of oxidative stress. However, this evidence cannot be extended to the general population who typically experience lower levels of lead exposure. This systematic review evaluates the epidemiological evidence on the association between lead and oxidative stress in non-occupationally exposed general population, with a particular focus on the pediatric population. Studies were identified through a systematic search of Medline and Web of Science. Ultimately, evidence from 15 studies conducted in children and 22 studies in adults from the general population was reviewed. Overall, the published findings are inconsistent, and there are very few well-designed studies on the relation between lead exposure and oxidative stress in the general population. The strength of the current evidence is discussed in light of the methodological approaches employed, and recommendations are made for future research directions. These include designing prospective studies with repeat measurements of clinically relevant oxidative stress markers to answer the question of causality and sensitive windows and reanalyzing previously published data, but using multivariable statistical approaches and adjustment for relevant explanatory factors.

Differential responses of healthy and chronic obstructive pulmonary diseased human bronchial epithelial cells repeatedly exposed to air pollution-derived PM4

While the knowledge of the underlying mechanisms by which air pollution-derived particulate matter (PM) exerts its harmful health effects is still incomplete, detailed in vitro studies are highly needed. With the aim of getting closer to the human in vivo conditions and better integrating a number of factors related to pre-existing chronic pulmonary inflammatory, we sought to develop primary cultures of normal human bronchial epithelial (NHBE) cells and chronic obstructive pulmonary disease (COPD)-diseased human bronchial epithelial (DHBE) cells, grown at the air-liquid interface. Pan-cytokeratin and MUC5AC immunostaining confirmed the specific cell-types of both these healthy and diseased cell models and showed they are closed to human bronchial epithelia. Thereafter, healthy and diseased cells were repeatedly exposed to air pollution-derived PM₄ at the non-cytotoxic concentration of 5 μg/cm². The differences between the oxidative and inflammatory states in non-exposed NHBE and COPD-DHBE cells indicated that diseased cells conserved their specific physiopathological characteristics. Increases in both oxidative damage and cytokine secretion were reported in repeatedly exposed NHBE cells and particularly in COPD-DHBE cells. Diseased cells repeatedly exposed had lower capacities to metabolize the organic chemicals-coated onto the air-pollution-derived PM₄, such as benzo[a]pyrene (B[a]P), but showed higher sensibility to the formation of OH-B[a]P DNA adducts, because their diseased state possibly affected their defenses. Differential profiles of epigenetic hallmarks (i.e., global DNA hypomethylation, P16 promoter hypermethylation, telomere length shortening, telomerase activation, and histone H3 modifications) occurred in repeatedly exposed NHBE and particularly in COPD-DHBE cells. Taken together, these results closely supported the highest responsiveness of COPD-DHBE cells to a repeated exposure to air pollution-derived PM₄. The use of these innovative in vitro exposure systems such as NHBE and COPD-DHBE cells could therefore be consider as a very useful and powerful promising tool in the field of the respiratory toxicology, taking into account sensitive individuals.

The Level of Selenium and Oxidative Stress in Workers Chronically Exposed to Lead

The possible beneficial role of selenium (Se) on the oxidative stress induced by lead (Pb) is still unclear in humans. Therefore, the aim of the present study was to explore the associations among the Se levels, chronic Pb exposure, oxidative stress parameters, and parameters characterizing the function of the antioxidant defense system in men who are occupationally exposed to Pb. Based on the median serum Se concentrations, the 324 study subjects were divided into two subgroups: a subgroup with a low Se level (L-Se) and a subgroup with a high Se level (H-Se). The levels of lead (PbB) and zinc protoporphyrin (ZPP) in the blood and the delta-aminolevulinic acid (ALA) level in the urine served as indices of Pb exposure. The PbB level was significantly lower in the H-Se group compared to that in the L-Se group by 6 %. The levels of 8-hydroxyguanosine and lipofuscin (LPS) and the activity of superoxide dismutase were significantly lower in the H-Se group compared to that in the L-Se group by 17, 19, and 11 %, respectively. However, the glutathione level (GSH) and the activities of glutathione peroxidase (GPx) and catalase were significantly higher by 9, 23, and 3 %. Spearman correlations showed positive associations between the Se level and GPx activity and GSH level. A lower serum Se level in chronically Pb-exposed subjects is associated with higher Pb blood levels and an elevated erythrocyte LPS level, which reflects the intensity of oxidative stress. Besides, in a group of Pb-exposed subjects with lower serum Se level, depleted GSH pool and decreased activity of GPx in erythrocytes were reported. However, the present results are inadequate to recommend Se supplementation for chronic lead exposure at higher doses than would be included in a normal diet except for selenium deficiency.

Lead Exposure and Oxidative Stress: A Systematic Review

Lead is an environmental toxicant that can induce oxidative stress (OS) via reactive oxygen species (ROS) generation, which has been reported as an important mechanism underlying lead toxicity (Gurer and Ercal 2000; Pande and Flora 2002; Kasperczyk et al. 2004a; Farmand et al. 2005; Verstraeten et al. 2008; Wang et al. 2009; Martinez-Haro et al. 2011). OS occurs when the generation of ROS exceeds the antioxidant system's ability to defend cells against oxidized molecules. ROS is a term generally used to refer to free radicals derived from O2 (e.g., superoxide anions [O2-] and hydroxyl radicals [OH-]) or to non-radical species (e.g. hydrogen peroxide [H2O2]) (Halliwell and Cross 1994).

Effects of environmental cadmium and lead exposure on adults neighboring a discharge: Evidences of adverse health effects

The purpose of the study was to determine Pb and Cd concentrations in humans and to assess the effect of co-exposure to these metals on biomarkers of oxidative stress and nephrotoxicity. Blood and urine levels of Pb and Cd, oxidative stress and urinary renal biomarkers were measured in 77 subjects neighboring a discharge and 52 in the control site. Exposed subjects showed significantly higher levels of lead and cadmium in blood and urine than the controls. Excessive production of reactive oxygen species induced by these metals in exposed subjects conducted to a decrease in antioxidant defense system (GPx, Selenium, GSH) and an increase in lipid peroxidation (MDA). Moreover, changes in markers of nephrotoxicity (high urinary concentrations of total protein, RBP and CC16, as well as GSTα and LDH increased activities) suggested the occurrence of discrete and early signs of impaired renal function for the discharge neighboring population.

Proinflammatory effects and oxidative stress within human bronchial epithelial cells exposed to atmospheric particulate matter (PM(2.5) and PM(>2.5)) collected from Cotonou, Benin

After particulate matter (PM) collection in Cotonou (Benin), a complete physicochemical characterization of PM2.5 and PM>2.5 was led. Then, their adverse health effects were evaluated by using in vitro culture of human lung cells. BEAS-2B (bronchial epithelial cells) were intoxicated during short-term exposure at increasing PM concentrations (1.5-96 μg/cm(2)) to determine global cytotoxicity. Hence, cells were exposed to 3 and 12 μg/cm(2) to investigate the potential biological imbalance generated by PM toxicity. Our findings showed the ability of both PM to induce oxidative stress and to cause inflammatory cytokines/chemokines gene expression and secretion. Furthermore, PM were able to induce gene expression of enzymes involved in the xenobiotic metabolism pathway. Strong correlations between gene expression of metabolizing enzymes, proinflammatory responses and cell cycle alteration were found, as well as between proinflammatory responses and cell viability. Stress oxidant parameters were highly correlated with expression and protein secretion of inflammatory mediators.

Blood lead concentrations in sub-Saharan African children below 6 years: systematic review

OBJECTIVE

To assess the geometric mean of blood lead levels in children aged below 6 years living in sub-Saharan Africa.

METHODS

Search strategies were developed in MEDLINE, Web of Science and Google scholar system, supplemented by screening of references from included papers and review articles. Studies including children younger than 6 years residing in sub-Saharan Africa (SSA) were eligible. The studies were assessed for quality of methods for blood collection, for participants' recruitment and for quality control for lead analyses. Data were extracted and synthetised by estimating the mean weighted by sample size.

RESULTS

A total of 11 148 published papers were identified with only 16 studies conducted in SSA. Only nine of them were relevant of inclusion criteria. The weighted mean of blood lead levels was 13.1 μg/dl. Five of included studies were classified as being less likely to present selection bias, having performed venipuncture and adequate quality control for lead analyses. The weighted mean from analyses involving only these studies was 16.2 μg/dl. Six of the included studies reported the prevalence of blood lead levels ≥10 μg/dl; levels ranged from 7.0% to 70.9%. Only one study reported the prevalence of blood lead levels ≥5 μg/dl (50%).

CONCLUSIONS

The geometric mean of blood lead levels in sub-Saharan African children is still elevated relative to the US children. The new standard from the Centers for Disease Control and Prevention (5 μg/dl) implies that important efforts should be directed towards the initiation (or reinforcement) of prevention programmes and thorough research studies in sub-Saharan Africa.

The effect of occupational lead exposure on blood levels of zinc, iron, copper, selenium and related proteins

The study objective was to evaluate the effect of occupational lead exposure on blood concentrations of zinc, iron, copper, selenium and proteins related to them, such as transferrin, caeruloplasmin and haptoglobin. The examined group consisted of 192 healthy male employees of zinc-lead works. By the degree of lead exposure, the exposed group was subdivided into three subgroups. The control group was composed of 73 healthy male administrative workers. The markers of lead exposure (blood levels of lead and zinc protoporphyrin) were significantly elevated in the exposed group compared with the control group. Additionally, concentrations of copper and caeruloplasmin were raised. The significant increase in haptoglobin level was observed only in the low exposure group. Selenium levels were significantly decreased, whereas iron, zinc and transferrin levels were unchanged in the exposed group compared with the control group. There were positive correlations between the lead toxicity parameters and the copper and caeruloplasmin levels. In conclusion, the effect of occupational exposure to lead on the metabolism of trace metals appears to be limited. However, significant associations between lead exposure and levels of copper and selenium were shown. Changed levels of positive acute-phase proteins, such as caeruloplasmin and haptoglobin, were also observed.

Low-level environmental exposure to lead and renal adverse effects: a cross-sectional study in the population of children bordering the Mbeubeuss landfill near Dakar, Senegal

This study deals with the health effects within a child population, neighbouring a landfill. After detecting metals in soil and air samples collected in the surroundings of the landfill and in a control site, we have studied: (i) levels of lead (Pb) and exposure biomarkers in blood and urine, (ii) oxidative stress biomarkers and (iii) renal injury by applying a set of early effect biomarkers. Levels of Pb were higher in the exposed site (i.e. 1129 mg/kg and 640 ng/m(3) in soil and air samples, respectively) versus those in the control site (i.e. 14.3 mg/kg and 9.3 ng/m(3) in soil and air samples, respectively). Pb impregnation and levels of delta-aminolevulinic acid in urine were influenced by the living site that shows the prevailingly alarming situation in the Mbeubeuss landfill. Malondialdehyde changes indicated Pb-induced excessive production of reactive oxygen species. Lactate dehydrogenase activities and proteinuria were found to be higher in the children living in the exposed site. These evidences may reveal the usefulness of these two effect biomarkers to monitor the kidney injury entailed by relatively low-environmental exposure to Pb. Overall, these results show that the Mbeubeuss landfill constitutes a real source of environmental and health risk, be it living or working on site, of the surrounding population, predominantly for children.

Relationship between physicochemical characterization and toxicity of fine particulate matter (PM2.5) collected in Dakar city (Senegal)

The massive increase in emissions of air pollutants due to economic and industrial growth in developing countries has made air quality a crucial health problem in this continent. Hence, it is somewhat critical to have a better knowledge on the air pollution in Sub-Saharan Africa countries. Three air pollution PM2.5 samples were also collected in two urban sites (i.e., Fann and Faidherbe) in Dakar (Senegal) and in a rural site near Dakar (i.e., Ngaparu). The two urban sites mainly differ in the type of used vehicles: in Fann, most of the traffic is made of buses, which are absent, in Faidherbe. The physicochemical characteristics of the three PM2.5 samples revealed their high heterogeneities and complexities, related to the multiple natural and anthropogenic emission sources. Results from 5-bromodeoxyuridine incorporation into DNA, mitochondrial dehydrogenase activity, and extracellular lactate dehydrogenase activity in PM2.5-exposed BEAS-2B cells suggested the exposure conditions (i.e., 3 and 12 μg PM/cm² during 24, 48, and 72 h) to further consider. The organic fractions (i.e., mainly PAHs) of the PM(2.5) samples were able to induce a time and/or concentration-dependent gene expression of CYP1A1 and CYP1B1, and, to a lesser extent, NQO1. There was a time and/or dose-dependent increase of both the gene expression and/or protein secretion of inflammatory mediators (i.e., TNF-α, IL-1β, IL-6, and/or IL-8) in PM(2.5)-exposed BEAS-2B cells. In agreement with the physicochemical characterization, urban PM(2.5) samples caused greater biological responses in BEAS-2B cells than the rural one. Variable concentrations of transition metals (i.e., Fe, Al, Pb, Mn, Zn) and organic compounds (i.e., PAHs) founded in the three PM2.5 samples might be firmly involved in a time- and/or dose-dependent toxicity, relying on inflammatory processes.

Manganese and lead in children's blood and airborne particulate matter in Durban, South Africa

Despite the toxicity and widespread use of manganese (Mn) and lead (Pb) as additives to motor fuels and for other purposes, information regarding human exposure in Africa is very limited. This study investigates the environmental exposures of Mn and Pb in Durban, South Africa, a region that has utilized both metals in gasoline. Airborne metals were sampled as PM(2.5) and PM(10) at three sites, and blood samples were obtained from a population-based sample of 408 school children attending seven schools. In PM(2.5), Mn and Pb concentrations averaged 17±27 ng m(-3) and 77±91 ng m(-3), respectively; Mn concentrations in PM(10) were higher (49±44 ng m(-3)). In blood, Mn concentrations averaged 10.1±3.4 μg L(-1) and 8% of children exceeded 15 μg L(-1), the normal range. Mn concentrations fit a lognormal distribution. Heavier and Indian children had elevated levels. Pb in blood averaged 5.3±2.1 μg dL(-1), and 3.4% of children exceeded 10 μg dL(-1), the guideline level. Pb levels were best fit by a mixed (extreme value) distribution, and boys and children living in industrialized areas of Durban had elevated levels. Although airborne Mn and Pb concentrations were correlated, blood levels were not. A trend analysis shows dramatic decreases of Pb levels in air and children's blood in South Africa, although a sizable fraction of children still exceeds guideline levels. The study's findings suggest that while vehicle exhaust may contribute to exposures of both metals, other sources currently dominate Pb exposures.

Blood lead levels in children of Lucknow, India

After implementing measures to control lead pollution in many countries, blood lead levels (BLLs) in children have been declined. The phase-out of leaded petrol began in Lucknow, the capital of most populated state, Uttar Pradesh in India on April 1, 2000. We evaluated the mean BLL and associated risk factors for lead exposure in Lucknow children (3-12 years) after petrol lead phase-out activity. The mean BLL of the 200 children was 9.3 microg/dL (range: 1.0-27.9 microg/dL). Seventy-four children (37%) had BLL above the Centre for Disease Control and Prevention's (CDC) level of concern (10 microg/dL). When these data were compared with BLLs determined by the George Foundation among the children of Mumbai, Bangalore, Kolkata, Chennai, Hyderabad, and Delhi during the year 1997 when leaded petrol was in use, where 62%, 62%, 87%, 96%, 43%, and 95%, respectively, then exceeded the CDC intervention level. Further, BLL of present study was very close to Mumbai children (age < or =12 years) estimated following the introduction of unleaded petrol, and 33% children had BLL above the CDC concern level with an average 8.4 microg/dL. Low socioeconomic status, proximity of home to traffic density, and mother's illiteracy were the factors associated with elevated BLLs in Lucknow children (P < 0.05). Overall, results indicate a declining trend of BLL in Lucknow children when compared with those reported from other cities of India when leaded petrol was in practice. A national population-based study is recommended to determine the prevalence of elevated BLLs after the phase-out of leaded-petrol. In addition, future studies on other sources of lead exposure in Lucknow are warranted for public health purposes.

Mass lead intoxication from informal used lead-acid battery recycling in dakar, senegal

BACKGROUND AND OBJECTIVES

Between November 2007 and March 2008, 18 children died from a rapidly progressive central nervous system disease of unexplained origin in a community involved in the recycling of used lead-acid batteries (ULAB) in the suburbs of Dakar, Senegal. We investigated the cause of these deaths.

METHODS

Because autopsies were not possible, the investigation centered on clinical and laboratory assessments performed on 32 siblings of deceased children and 23 mothers and on 18 children and 8 adults living in the same area, complemented by environmental health investigations.

RESULTS

All 81 individuals investigated were poisoned with lead, some of them severely. The blood lead level of the 50 children tested ranged from 39.8 to 613.9 microg/dL with a mean of 129.5 microg/dL. Seventeen children showed severe neurologic features of toxicity. Homes and soil in surrounding areas were heavily contaminated with lead (indoors, up to 14,000 mg/kg; outdoors, up to 302,000 mg/kg) as a result of informal ULAB recycling.

CONCLUSIONS

Our investigations revealed a mass lead intoxication that occurred through inhalation and ingestion of soil and dust heavily contaminated with lead as a result of informal and unsafe ULAB recycling. Circumstantial evidence suggested that most or all of the 18 deaths were due to encephalopathy resulting from severe lead intoxication. Findings also suggest that most habitants of the contaminated area, estimated at 950, are also likely to be poisoned. This highlights the severe health risks posed by informal ULAB recycling, in particular in developing countries, and emphasizes the need to strengthen national and international efforts to address this global public health problem.

Evaluation of calcium excretion in Brazilian infantile and young population environmentally exposed to lead

Lead exposure is an important issue in the research of several toxic effects resulting from the biochemical interaction between this metal and the organism. Calcium is a fundamental mineral for the maintenance of the organism homeostasis where there is interaction between lead and calcium in metabolic pathways. Environmental lead exposure by verifying the usefulness and applicability of urinary calcium/creatinine ratio (UCa/Cr) in this context was evaluated. This was an extensive socio-demographic study of the nutritional profile, lead exposure biomarkers in blood and the urine and UCa/Cr ratio. The children studied were from a low socio-economic group characterized by unsatisfactory nutritional diet. Lead environmental exposure was shown by biomarkers, with UCa/Cr ratio having positive and significant correlations with both lead and delta-aminolevulinic acid in urine (ALA-U), without colinearity diagnosis. There was a strong association between calcium excretion and lead exposure as a result of linear regression construction models. In children, lead increases calcium excretion which is an additional risk to infantile health. Urinary calcium/creatinine ratio may be a useful tool in the biological monitoring of lead exposure and health promotion programs.

Low level lead exposure and oxidative stress: Current opinions

Lead continues to pose a serious threat to the health of many children as well as adults. Concern about lead exposure as a significant public health problem has increased as evidence has mounted regarding adverse health effects at successively lower levels. This issue is complicated by the fact that there is no demonstrated biological function of lead in human. Lead potentially induces oxidative stress and evidence is accumulating to support the role of oxidative stress in the pathophysiology of lead toxicity. Lead is capable of inducing oxidative damage to brain, heart, kidneys, and reproductive organs. The mechanisms for lead-induced oxidative stress include the effects of lead on membranes, DNA, and antioxidant defense systems of cells. Recent epidemiological and toxicological studies have reported that lead exposure causes several diseases including hypertension, kidney disease, neurodegenerative disease and cognitive impairment. Although all these diseases include components of oxidative stress, the relevance of oxidative stress to lead-related diseases with low lead exposure has been criticized because most of the mechanistic studies have been conducted at moderate to higher dose levels. The association between low level lead exposure and oxidative stress has not been explored systematically. The present review focuses on mechanisms for lead-induced oxidative stress and relevance of oxidative stress to lead-related human disease with low lead exposure.