Dr Sazal Kumar

There are significant concerns about the risks to human health posed by metal(loid) contamination in dietary fishes in Bangladesh. Therefore, this study aimed to evaluate heavy metal(loid) contamination in fish and their associated health risks using published data from 2000 to 2022. Additionally, the safe limit of fish consumption was estimated using the target hazard quotient (THQ) followed by computational modelling and artificial neural networks (ANN). Results showed that freshwater and herbivorous fishes pose the least non-cancer risks, whereas saltwater and carnivorous fishes pose the highest non-cancer risks to Bangladeshi consumers. However, freshwater and omnivorous fish consumption pose the highest cancer risks compared to all studied metal(loid)s. In particular, among the heavy metal(loid)s, As, Cr, Hg, and Ni pose significant cancer and non-cancer risks to Bangladeshi consumers. On the contrary, the ANN and Decision tree regression (DTR) characterized the dataset, simulation model, or data testing condition, reaching 94.7% accuracy and allowing us to measure the safest fish consumption limit. The herbivorous fishes are less contaminated and allow greater consumption (175.09¿g¿day-1). Contrarily, the allowable intake rates of carnivorous and omnivorous fishes are 153.05 and 168.63¿g¿day-1, respectively. Besides, the safe consumption rate of saltwater fishes was 156.51¿g¿day-1, which was lower than freshwater (180.59¿g¿day-1) and euryhaline fishes (182.17¿g¿day-1). Therefore, this study will assist fish consumers in selecting less contaminated fish, ensuring safe consumption levels, and ultimately reducing health risks associated with metal(loid) contamination in fish.

Air quality degradation due to high levels of atmospheric particulate matter (PM) of various size fractions and the associated potentially toxic trace elements (PTEs) is a global concern. This article provides a thorough review and analysis of the temporal and spatial distribution of PM and PTEs in Bangladesh, offering a comprehensive assessment with other megacities worldwide based on existing literature. This study provides insights into the sources and transport mechanisms of PM and their link to human health. The level of PM was consistently high in Dhaka (capital of Bangladesh), with occasional higher levels in the surrounding cities. Different functional areas within Bangladesh show varying levels of PM, with total suspended particulates (TSP) being notably prevalent. When compared to megacities worldwide, African and Asian megacities, like India, Pakistan, Nigeria, and Egypt, exhibited higher PM concentrations. The concentration of PM-associated PTEs varies significantly among megacities and PM10 tends to have relatively higher concentrations¿of PTEs compared to other fractions in Bangladesh. Pb in ambient air was found across most megacities, with a temporal increase in Bangladesh. TSP exhibited the highest relative Pb content, followed by PM10 and PM2.5. Temporal factors, geographic locations, meteorological conditions, and anthropogenic activities contribute to the variation in PM and associated PTEs concentration in Bangladesh and global megacities. Ultimately, this study would¿aid policymakers in assessing the magnitude of PM pollution in Bangladesh compared to other megacities considering regional factors.

Elevated metal(loid) concentrations in soil and foodstuffs is a significant global issue for many densely populated countries like Bangladesh, necessitating reliable estimation for sustainable management. Therefore, a comprehensive data synthesis from the published literature might help to provide a wholistic view of metal(loid) contamination in different areas in Bangladesh. This study provided a clearer view of metal(loid) contamination status and their associated ecological and health risks in different land use and ecosystems in Bangladesh. Comprehensive analyses were performed on data gathered from 143 published articles using multiple statistical techniques including meta-analysis. Considering the potential loading of metal(loid), the data were summarized under various groups, including coastal, rural, urban and industrial regions. Also, the concentrations of seven metal(loid)s, e.g., cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and arsenic (As) in soil, sediment, cereal, vegetable, fruit, surface water and groundwater were included. Results showed that the relative concentrations of metal(loid)s in comparison to the maximum permissible limit (MPL) were mostly less than one, although they varied significantly for locations and individual metal(loid). However, the normalized cumulative relative concentrations over the MPL for all seven metal(loid)s across different environmental samples were 4.75, 2.97, 1.51 and 2.79 for coastal, industrial, rural and urban areas, respectively, which was¿due to the higher concentration of Cd, Cr and Cu. Similar to the metal(loid) concentrations, the average of cumulative median non-cancer risks for all metal(loid)s was in the order of industrial (6.46) > urban (4.05) > rural (3.83) > coastal (2.41). This research outcome will provide a foundation for future research on metal(loid)s and will help in pertinent policy-making by the relevant authorities in Bangladesh.

The Sundarbans is the largest single-mass mangrove forest in the world, experiencing environmental and anthropogenic stress from metal(loid) inputs. We undertook a comprehensive assessment of sediment contamination and ecological risks posed by metal(loid)s in the Sundarbans using previously published data. There was a distinct difference in metal(loid) content, pollution level and ecological risk in Bangladeshi and Indian parts of the Sundarbans, with the Indian counterpart experiencing relatively higher metal(loid) pollution. The higher pollution level in India might be attributed to its vicinity to municipal and industrial areas that act the primary source of metal(loid)s in the Sundarbans. The cumulative ecological risks of metal(loid)s pointed out that the south-eastern part of Bangladeshi Sundarbans and north-eastern Indian part are at moderate ecological risk. This research will provide valuable data to inform the responsible authorities and will underpin future policies and management to reduce future metal(loid) inputs in the Sundarbans.

Intense human activities, particularly industrial and agricultural output, has enriched metal(loid)s in riverine sediment and endangered aquatic ecosystems and human health. Promoting proper river management requires an assessment of the possible ecological hazards and pollution posed by metal(loid)s in sediments. However, there are limited large-scale risk assessments of metal(loid)s contamination in riverine sediment in heavily populated nations like Bangladesh. This study compiled data on sediment metal(loid)s, for example, Cd, As, Cu, Ni, Cr, Pb, Mn, and Zn, from 24 major rivers located across Bangladesh between 2011 and 2022 and applied positive matrix factorization (PMF) to identify the critical metal(loid)s sources and PMF model-based ecological risks. Based on studied metal(loid)s, 12¿78% of rivers posed higher contents than the upper continental crust and 8% of the river sediments for Cr and Ni, whereas 4% for Cd and As exceeded probable effect concentration. Cr and Ni in the sum of toxic units (STU), whereas Mn, As and Cd in potential ecological risk (PER) posed the highest contribution to contaminate sediments. In the studied rivers, sediment contaminant Mn derived from natural sources; Zn and Ni originated from mixed sources; Cr and Cu were released from the tannery and industrial emissions and Cd originated from agricultural practices. Source-based PER and NIRI indicated that mixed source (4% rivers) and tannery and industrial emission (4% rivers) posed very high risks in sediments. For the creation of macroscale policies and the restoration of contaminated rivers, our national-scale comprehensive study offers helpful references.

Buriganga is an economically important river located around the industrialized urban area of Dhaka City, Bangladesh. In this study, 17 water quality parameters (electrical conductivity, pH, total suspended solids, temperature, F-, Cl-, SO42-, Cr, Ni, As, Cd, Hg, Cu, Pb, Fe, Mn, and Zn) of surface and deep waters of the Buriganga River were measured to assess the water quality, pollution level, elemental sources, and their potential ecological and human health risks. Comparing the concentrations of the analyzed parameters with the permissible standards, it was indicated that the water in Buriganga is unsafe for residential and recreational uses. Principal component and correlation analysis revealed that point and diffuse sources, such as the combustion of lubricant oils, fuel additives, exhaust fumes from vehicles, domestic wastewater, and inorganic fertilizers from agricultural fields, control the water quality. Regardless of depth, a higher degree of contamination and ecological risk was observed during the dry season, indicating a higher content of heavy metals in river water, which might impact the ecological balance in the future. Through ingestion, the hazard quotient (HQ) of As, Cd, Pb, and Hg and the hazard index (HI) values were higher than the risk threshold (HQ > 1). Total HI values for children in both residential and recreational water were higher than those for adults (1.04 × 101 and 1.73 × 100 for surface and deep water, respectively), indicating that children are more sensitive to elemental contamination. Total carcinogenic risks of Cr and As due to exposure to water were higher than the standard limit (>1.0 × 10-4), which indicated possible cancer risks to the inhabitants around the river. Therefore, regular monitoring of river water quality and sustainable management could be implemented to recover the polluted river water and keep it pollution-free in the future.

In this study, we analyse the development of mangroves around the South China Sea (SCS) over the last 40 kyrs BP. Findings are based on 208 palynological samples obtained from a sediment core (NS07¿25) in the reef area of the SCS. These palaeo-records are interpreted in the context of 161 surface sediment palynological samples obtained from across the SCS that serve as a modern reference set. Employing the Near Analysis function in ArcGIS, mangrove pollen in modern surface sediment comprises two major assemblages: dominant Rhizophoraceae (subtropical, wind- and animal-pollinated taxa) in the northern SCS and diverse Sonneratia (tropical, animal-pollinated taxa) in the southern SCS. The distribution field of these modern mangrove pollen assemblages is bounded by the Nansha Islands and reefs, which may act to obstruct pollen transportation between the northern and southern parts of the SCS. In our late Quaternary core, concentrations of Rhizophoraceae and Sonneratia pollen assemblages gradually increase in the late stage of Marine Isotope Stage 3 and during the Last Glacial Maximum, as a result of falling sea level and mangrove colonization of the exposed marine shelf, whereas they rapidly decrease in the Deglacial period, coincident with an increase in sea level and coastal retreat. The occurrence of Rhizophoraceae pollen assemblages in the southern SCS during the Last Glacial Maximum indicates that these communities disperse southward in response to climate change. Our findings highlight the complex effects of growth conditions, varied pollinators, and transportation patterns on the preservation of Rhizophoraceae and Sonneratia pollen assemblages with implications for understanding change in climate and sea level since 40 kyr BP.

Exposure to dust particles enriched with arsenic (As) is a significant health threat for populations living in Southeast Asian megacities. The mineralogical composition of dust particles is the key factor that controls the retention and release of As. This study investigated the degree of metal(oid)s pollution (As, Ca, Fe, K, Ga, Rb, Sr, Ti, V, Y, and Zr) in road dust of Dhaka city, Bangladesh. Enrichment factor and geoaccumulation index suggested that the road dust was heavily enriched with As, which triggers a comprehensive investigation of its controlling mechanisms and potential health risks by combining physicochemical and mineralogical information with multivariate analysis and a simulated probabilistic risk estimation model. Alkaline road dust (pH1:5 ranges from 8.02 to 10.34) in Dhaka city was found to have significant enrichment of As. Dust alkalinity was possibly controlled by the presence of carbonate minerals, such as calcite. Quartz was identified as the dominant mineral phase followed by magnesium carbon arsenide (MgCAs2). Carbonate mineral driven alkaline pH conditions in road dust would potentially trigger the release and mobilization of As to the environment. However, organic complexation can stabilize As on particle surfaces. Monte Carlo simulation-based health risk forecast suggested that the probability of As associated cancer risk has greatly exceeded the threshold value of 1E-4 for adults and children, and children are more vulnerable than adults. According to sensitivity analysis, the concentration of As and exposure duration (ED) posed the most significant impact (>58%) on risk estimation.

Lead (Pb) pollution in the environment predominantly occurs through anthropogenic activities, which pose significant threats to human health and that of biota. In this study, Pb and other elements were investigated in different soils (n = 52), crops (n = 24) and water (n = 13) around a lead-acid battery (LAB) recycling workshop in southwestern Bangladesh. Most of the elements' concentrations (except Se and Ag) in soil were lower than the background concentrations. However, excessive concentrations of Pb were found in both surface (966 ± 2414 mg kg-1 at 0¿15 cm) and subsurface (230 ± 490 mg kg-1 at 15¿30 cm) soil. Although no definitive pattern or direction in elemental concentration in soil was observed, relatively higher concentrations of most elements were detected at the southeast part of the factory. The LAB factory, brick kiln, agricultural and geogenic activities might be the sources of these elements in soil. Extremely high amounts of Cr, As, Cd, and Pb were found in the food crops around the area. In particular, the Pb concentrations were 114 ± 155 and 665 ± 588 mg kg -1 dry weight in rice grain and straw, respectively, which reflected the emissions of Pb from the LAB recycling workshop. Moreover, 40% and 100% of the groundwater samples exceeded, respectively, the WHO provisional guideline values for As (0.01 mg L-1) and Pb (0.05 mg L-1). Consequently, a high level of Pb contamination in the soil was observed while assessing different soil pollution indices. Human health risk assessment indicated severe carcinogenic (from Pb, As, and Cr intake) and non-carcinogenic (from Pb, As, Co, Cr, Ni and Sb intake) health risks are associated with rice and groundwater consumption. It is concluded that all LAB recycling workshops should be better managed to prevent Pb pollution from seeping into the environment.

Arsenic (As) is one of the major pollutants of groundwater in many developing countries including Bangladesh, and it poses a significant health risk to humans. This study aims to assess the potential health threat to school children through As-contaminated drinking water. For this analysis, 180 samples of water from tubewells located in high school premises in southwestern Bangladesh were analyzed for As and other elements such as iron (Fe), manganese (Mn), calcium (Ca), and magnesium (Mg). Also examined were the physicochemical parameters including, pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, chloride, and hardness. The results revealed that groundwater is slightly alkaline and very hard. The mean As concentration in drinking water was 71.06 ± 66.47 µg L-1 (range: 1¿250 µg L-1), which was 7-fold higher than the World Health Organization (WHO) provisional guideline value (10 µg L-1). Human health risk assessment was evaluated using hazard quotient (HQ) for As, Fe and Mn, and the cancer risk (CR) assessment for As only. The values of As for HQ and CR (HQ and CR were up to 9.04 and 4.1 × 10-3 for boys and 9.82 and 4.4 × 10-3 for girls, respectively), revealed that children are susceptible to higher risks. The risk was slightly higher in girls than boys were. No health risk was observed in the children when they consumed drinking water containing Mn and Fe. The school-going children are at the greatest threat from As-containing drinking water on school premises, and this situation requires urgent attention to ensure safe potable water in As-endemic areas. Graphical abstract: [Figure not available: see fulltext.].