Tracing lead contamination in foods in the city of Kolkata, India

Source apportionment and emission projections of heavy metals from traffic sources in India: Insights from elemental and Pb isotopic compositions

The study investigates the sources of metals in urban road dusts using elemental concentration and Pb isotopic ratios. The elemental concentrations are also utilized to determine the present heavy metal emissions as well as projected emissions till 2045. Bayesian mixing model for source apportionment highlights the significant contributions of both exhaust and non-exhaust sources to the metal-enriched urban road dusts, with each contributing approximately 40 %. Emission analysis reveals that India's projected electric vehicle (EV) penetration may not be sufficient to suppress the metal emissions from vehicular exhausts. Further challenge is posed by high metal concentrations in the non-exhaust sources, that dominates the emission of some metals compared to exhaust sources. If the metal concentrations remain unchanged, the emission analysis predicts alarming increases in total emissions from all the exhaust and non-exhaust sources by 174 %, 176 %, 163 % and 184 % for Ni, Cu, Zn and Pb, respectively, from 2022 to 2045. Thus, it is crucial to reduce the metal concentrations in traffic emission sources and also impose better regulatory measures to improve the urban metal pollution scenario.

Entrapment of atmospheric particle bound heavy metals by ferns as evidenced by lead (Pb) isotope and MixSIAR: Implications for improving air quality

Plant metal uptake can occur through both soil-root and atmospheric transfer from leaves. The latter holds potential implications for development of biofiltration systems. To explore this potential, it is crucial to understand entrapment capacity and metal sources within plants. As ferns absorb materials from atmosphere, this study focuses on two abundant fern species growing in densely populated and highly polluted regions of Eastern India. Gravimetric quantification, elemental concentration and Pb isotopic analyses were performed by segregating the ferns into distinct components: foliage dusts (loose dust (LD) and wax-bound dust (WD)) and plant tissue (leaves and roots). To understand metal sources, the study analyzes soil, and atmospheric particulates (PM10 and dust fall (DF)). Results indicate that, while LDs have soil dust influence, wax entraps atmospheric particulates and translocates them inside the leaves. Furthermore, roots demonstrate dissimilar isotopic ratios from soil, while displaying close association with atmospheric particulates. Isotopic composition and subsequent mixing model reveal dominant contribution from DF in leaves (53-73%) and roots (33-86%). Apart from DF, leaf Pb is sourced from PM10 (21-38%) with minimal contribution from soil (6-10%). Conversely, in addition to dominance from DF, roots source Pb primarily from soil (12-62%) with a meagre 2-8% contribution from PM10.

Use of Radioisotope Ratios of Lead for the Identification of Historical Sources of Soil Lead Contamination in Santa Ana, California

Lead (Pb) is an environmental neurotoxicant that has been associated with a wide range of adverse health conditions, and which originates from both anthropogenic and natural sources. In California, the city of Santa Ana represents an urban environment where elevated soil lead levels have been recently reported across many disadvantaged communities. In this study, we pursued a community-engaged research approach through which trained “citizen scientists” from the surrounding Santa Ana community volunteered to collect soil samples for heavy metal testing, a subset of which (n = 129) were subjected to Pb isotopic analysis in order to help determine whether contamination could be traced to specific and/or anthropogenic sources. Results showed the average 206Pb/204Pb ratio in shallow soil samples to be lower on average than deep samples, consistent with shallow samples being more likely to have experienced historical anthropogenic contamination. An analysis of soil Pb enrichment factors (EFs) demonstrated a strong positive correlation with lead concentrations, reinforcing the likelihood of elevated lead levels being due to anthropogenic activity, while EF values plotted against 206Pb/204Pb pointed to traffic-related emissions as a likely source. 206Pb/204Pb ratios for samples collected near historical urban areas were lower than the averages for samples collected elsewhere, and plots of 206Pb/204Pb against 206Pb/207 showed historical areas to exhibit very similar patterns to those of shallow samples, again suggesting lead contamination to be anthropogenic in origin, and likely from vehicle emissions. This study lends added weight to the need for health officials and elected representatives to respond to community concerns and the need for soil remediation to equitably protect the public.

Adsorption mechanism of Pb2+ in montmorillonite nanopore under various temperatures and concentrations

Adsorption of lead (Pb²⁺) onto the montmorillonite (Mt) surface is one of the key approaches to remove Pb²⁺ in geological and environmental engineering. Temperature and initial Pb²⁺ concentration are two essential factors that influence the adsorption capacity of Mt on absorbing Pb²⁺. However, the nanoscale governing mechanism of temperature and initial concentration on Pb²⁺ adsorbing of Mt is still unclear. This research performed comprehensively molecular dynamics (MD) simulations to investigate how temperature and initial concentration affect the dynamic Pb²⁺ adsorption of Mt nanopore. The Pb²⁺ removal ratio shows a two-stage variation with the increase of initial Pb²⁺ concentration. Temperature controls the maximum initial Pb²⁺ concentration for complete Pb²⁺ removal by changing the maximum adsorption energy of Mt. Temperature also influences the maximum adsorption capacity and Pb²⁺ removal ratio of Mt nanopore indirectly by changing diffusion and hydration state of Pb²⁺. The initial Pb²⁺ concentration corresponding to the maximum adsorption energy coincides with the maximum initial Pb²⁺ concentration determined by the Pb²⁺ removal ratio. Lower adsorption energy and higher level of hydration and diffusion make Pb²⁺ absorbing on Mt surface become more difficult, reducing the Pb²⁺ adsorbing capacity of Mt. The initial Pb²⁺ concentration influences adsorption capacity and Pb²⁺ removal ratio not only via altering the quantity of Pb²⁺ but also through controlling the adsorption energy of Mt, as well as the diffusion and hydration state of Pb²⁺. With the increase of initial Pb²⁺ concentration, the hydration of Pb²⁺ is weakened while the adsorption energy of Mt and diffusion of Pb²⁺ are enhanced.

A feasibility study of Indian fly ash-bentonite as an alternative adsorbent composite to sand-bentonite mixes in landfill liner

Multi-layered engineered landfill consists of the bottom liner layer (mainly bentonite clay (B)) upon which the hazardous wastes are dumped. In current practice, sand (S) is mixed with bentonite to mitigate the adverse effects of using bentonite alone in the liner layer. Incorporation of waste and unutilized fly ash (FA) as an amendment material to B has been explored in terms of its hydro-mechanical properties, but not gauged its adsorption potential. Indian subcontinent primarily relies on the thermal power source, and FA dumps have already reached its full capacity. The objective of this study is to explore the adsorption characteristics of four B-FA composite mixes sourced within India, considering Pb²⁺ as a model contaminant. The effect of fly ash type, fly ash amendment rate and adsorbate concentration was explored in the current study and juxtaposed with B-S mixes, based on 960 batch adsorption tests. Both B-FA and B-S mixes reached equilibrium adsorption capacity within 65 min. At higher adsorbate concentrations (commonly observed in the liner), B-FA mixes exhibited superior adsorption capacity, mainly one mixed with Neyvelli fly ash (NFA). The effect of higher amendment rate had little impact on the adsorption capacity at different concentration, but gradually decreased the percentage removal of Pb²⁺. The B-S mix showed a drastic decrease in percentage removal at higher adsorbate concentration among all tested mixes. Systematic characterization including geotechnical properties, microstructure and chemical analysis was also done to interpret the obtained results. Both Freundlich and Langmuir models fitted the isotherm data well for all B-FA mixes. The maximum adsorption capacity from the isotherm was correlated to easily measurable Atterberg limits by two empirical relationships.

Adsorption characteristics of Barmer bentonite for hazardous waste containment application

Low hydraulic conductivity and high chemical immobilization are the two characteristics that make bentonite a mandatory construction material for hazardous waste containment applications. We performed a comprehensive batch sorption study on Barmer bentonite (BB), an exclusive construction clay mined in India, using lead (Pb²⁺) as a model contaminant. The maximum adsorption capacity of BB was obtained as 55 mg g^-1 at pH 5 and 27 ± 2℃. Adsorption was extremely rapid, with equilibrium attained <5 min for the BB. Increased adsorbent dosage resulted in higher Pb²⁺ percentage removal, while adsorption capacity decreased. Ionic strength, salt concentration, valency and ionic radius played a critical role in suppressing the adsorption of Pb²⁺. Clay fabric change was observed to be dispersed at low ionic strength and gradually attained aggregated face-to-face structures at high ionic strength. The simultaneous presence of other metals/salts strongly influenced Pb²⁺ removal by BB, while divalent salt exhibited high suppression of adsorptive reaction at low concentrations. Sorption isotherm and kinetic modeling results indicated the possibility of chemisorption of Pb²⁺ on BB. Based on the thermodynamic analysis, it was noted that Pb²⁺ adsorption on BB is exothermic, spontaneous and adsorption reaction is less favorable at a higher temperature.

Heavy metals in urban road dusts from Kolkata and Bengaluru, India: implications for human health

Air pollution and dust pollution are major urban environmental issues, with road dust being a potential source and a pathway for human exposure. The developing megacities of India, where the population may spend a significant portion of their working lives close to the roadside, including consuming street food, have obvious source-pathway-receptor linkages. The aim of this study in Kolkata and Bengaluru, India, was to evaluate the risk to human health from inorganic components of road dust. Samples were collected and analysed from a cross section of urban environments for a wide range of anthropogenic and geogenic elements, some such as antimony showing an increase in response to vehicle activity. Calculated enrichment factors relative to crustal abundance demonstrated significant enrichment in common heavy metals and less commonly reported elements, e.g. molybdenum, antimony, that may be used as contaminant markers. Factor analysis gave multielement signatures associated with geography, vehicle traffic and local industry. The bio-accessibility of road dusts in terms of ingestion was determined using the BARGE method with more than 50% of zinc and lead being available in some cases. A formal human health risk assessment using the US EPA framework showed that lead in Kolkata and chromium in Bengaluru were the elements of most concern amongst chromium, nickel, copper, zinc and lead. However, the only risk combination (hazard index) shown to be significant was lead exposure to children in Kolkata. Ingestion dominated the risk pathways, being significantly greater than dermal and inhalation routes.

Street food research worldwide: a scoping review

BACKGROUND

Street foods vary with respect to their nutritional value and safety characteristics and contribute to a sizable proportion of food intake in many populations worldwide. Therefore, the present study aimed to describe the coverage in the scientific literature of different health-related and socio-economic aspects of street food consumption and trading.

METHODS

Three electronic databases (searched from inception to 16 October 2017), a hand-search of relevant journals and backward citation tracking were used to identify eligible scientific articles with a main objective of investigating or reporting specific results on health-related or socio-economic aspects of street food. Papers published in English, Portuguese, French, Spanish or Italian, as well as English abstracts of papers published in other languages, were assessed. The selected articles were evaluated by two independent researchers and described according to year of publication, geographical distribution, definition of street food, main topics addressed and target population.

RESULTS

In total, 441 papers were selected. The number of publications has increased in recent years, almost half of them being published after 2012. Almost three-quarter of the articles were from Africa or Asia. Most studies addressed food safety (85.5%), whereas street food availability and consumption were much less frequently investigated (30.3%). The focus of the studies was usually the food (mostly its microbiological contamination) and the vendors (mostly their food handling), whereas consumers and vending sites were seldom evaluated. More than half of the studies did not specify a definition for street food.

CONCLUSIONS

Efforts are needed for a more widespread and comprehensive assessment of different issues related to street food availability and consumption in different settings, especially regarding street food offer, nutritional composition, and patterns of purchase and consumption by the population.

Geochemical sources of metal contamination in a coal mining area in Chhattisgarh, India using lead isotopic ratios

A geochemical study of the trace metals and lead isotopic ratios of soil and sediments in Korba, Chhattisgarh, India is presented here for the first time. Korba, the nation's 'power hub' is also the fifth among its eighty-eight most critically polluted industrial hotspots. A very high mean concentration (in mg kg-1) of V (308), Cr (567), Mn (3442), Co (92), Cu (218), Zn (426), Pb (311), Th (123) and U (32) characterized the sediments of the studied area with mean I_geo values of the trace metals ranging from -2.29 to 3.27. In the two-ratio scatter Pb isotope plot of the different environmental matrices, except for human blood, coal, soil, sediments, non-washed leaves, flyash and diesel overlapped linearly in the mixing line between diesel as the highest anthropogenic end member and a core sediment fraction representing its geogenic counterpart. The mean ²⁰⁷Pb/²⁰⁶Pb Pb ratio decreased in the order of diesel (0.9012) > flyash (0.8757) > coal (0.8498) soils and sediments (0.8374) > lowest core sediment fraction (0.8017). Principal Component Analysis (PCA) of the trace metal data extracted V, Cr, Cu, Zn, Pb, U and Th in the first component PC1. The northeastern part of the study area revealed major hotspots of V, Cu, Co, Zn and Pb near the flyash dykes of the power stations. Human blood used as a biomarker for Pb pollution in this study had a mean blood lead level of 28 μg/dl with a distinctive high ²⁰⁷Pb/²⁰⁶Pb ratio of 0.8828.

Historical documentation of lead toxicity prior to the 20th century in English literature

Lead is a heavy metal that remains a persistent environmental toxin. Although there have been a substantial number of reviews published on the health effects of lead, these reviews have predominantly focused on recent publications and rarely look at older, more historical articles. Old documents on lead can provide useful insight in establishing the historical context of lead usage and its modes of toxicity. The objective of this review is to explore historical understandings and uses of lead prior to the 20th century. One hundred eighty-eight English language articles that were published before the year 1900 were included in this review. Major themes in historical documentation of lead toxicology include lead's use in medical treatments, symptoms of lead poisoning, treatments for lead poisoning, occupational lead poisonings, and lead contamination in food and drinking water. The results of this review indicate that lead's usage was widespread throughout the 19th century, and its toxic properties were well-known. Common symptoms of lead poisoning and suggested treatments were identified during this time period. This review provides important insight into the knowledge and uses of lead before the 20th century and can serve as a resource for researchers looking at the history of lead.

Geochemical sources, forms and phases of soil contamination in an industrial city

This study examines current soil contamination in an Australian industrial city, Newcastle. Public (roadside verges and parks) and private (homes) surface soils (n=170) contained metal(loid)s elevated above their respective Australian Health Investigation Levels (HIL). Lead (Pb), the most common contaminant in the city, exceeds the HIL for residential soils (HIL-A, 300mg/kg) in 88% of private soils (median: 1140mg/kg). In-vitro Pb bio-accessibility analysis of selected soils (n=11) using simulated gastric fluid showed a high affinity for Pb solubilisation (maximum Pb concentration: 5190mg/kg, equating to 45% Pb bio-accessibility). Highly soluble Pb-laden Fe- and Mn-oxides likely contribute to the bio-accessibility of the Pb. Public and private space surface soils contain substantially less radiogenic Pb (range: ²⁰⁸Pb/²⁰⁷Pb: 2.345-2.411, ²⁰⁶Pb/²⁰⁷Pb: 1.068-1.312) than local background soil (²⁰⁸Pb/²⁰⁷Pb: 2.489, ²⁰⁶Pb/²⁰⁷Pb: 1.198), indicating anthropogenic contamination from the less radiogenic Broken Hill type Pb ores (²⁰⁸Pb/²⁰⁷Pb: 2.319, ²⁰⁶Pb/²⁰⁷Pb: 1.044). Source apportionment using Pb isotopic ratio quantification and soil mineralogy indicate the city's historic copper and steel industries contributed the majority of the soil contaminants through atmospheric deposition and use of slag waste as fill material. High-temperature silicates and oxides combined with rounded particles in the soil are characteristic of smelter dust emissions. Additionally, a preliminary investigation of polycyclic aromatic hydrocarbons in soils, sometimes associated with ferrous metal smelting, coal processing or burning of fossil fuels, shows that these too pose a health exposure risk (calculated in comparison to benzo(a)pyrene: n=12, max: 13.5mg/kg, HIL: 3mg/kg).