Total Mercury Levels Research Articles

Total mercury exposure through canned tuna in water sold in Quito, Ecuador.

Mercury is a toxic trace metal found in seafood products owing to its bioaccumulative and ubiquitous nature. Seafood and fish are frequently consumed, being necessary to assess its human health risk. Accordingly, this study quantified total mercury in samples of canned tuna in water from supermarkets in the Metropolitan District of Quito in Ecuador, in order to ensure that Hg content is within the maximum limits stablished in national and international regulations. Total mercury levels were measured through cold vapor atomic fluorescence spectrophotometry. Three of the most consumed tuna brands in Ecuador were analyzed, coded as A, B, and C, according to the price at which they are sold in the market (A < B < C). Results indicated that mean total mercury in different tuna brands were within the permissible limits. Total mercury concentrations were 0.14 ± 0.11mg kg-1; 0.41 ± 0.42mg kg-1; and 0.25 ± 0.22mg kg-1 for brands A, B, and C, respectively. However, for brand B the potential non-carcinogenic risk of mercury for consumers exceeded the threshold limit (> 1). When considering the highest total mercury content to which Ecuadorian population is exposed through the consumption of brand A, B, and C, the recommended weekly intake for children and adults were: A: 63g and 306g; B: 12g and 57g; C: 30g and 144g, respectively.

Mercury monitoring in farmed Pacific bluefin tuna (Thunnus orientalis) using liquid asymmetric-electrode plasma optical emission spectroscopy: Ventricle tissue as a potential indicator

Tuna muscle is known to contain high levels of mercury, necessitating the monitoring of mercury concentrations in farmed fish at production sites. There is currently no straightforward in on-site method for testing whether the mercury levels in farmed tuna exceed regulatory limits. This study investigated the potential application of liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES) to estimate mercury concentrations in the tissues of cultured Pacific bluefin tuna at aquaculture farms. No significant differences in mercury concentrations were observed between the ventricle tissue and biopsied tissue from tuna bleeding site (TTBS), which can be harvested without reducing the market value of farmed tuna (Hg concentration of the ventricle tissue and the TTBS, median: 0.41 and 0.40 mg/kg, respectively). In addition, the relationship between mercury concentrations in the ventricle tissue and in the edible portions of three tuna fish was examined. The findings showed that total mercury level in the edible tissues varied, with the ratio of the mercury level in edible tissues to that in the ventricle ranging from 0.39 to 1.08. A positive correlation was observed between the average total mercury levels in edible tissues and ventricle tissue. These results suggest that determining the total mercury level in the ventricle, which is typically discarded at processing sites, may serve as a convenient proxy for quality control and monitoring purposes using the LAEP-OES method. However, larger sample sizes are needed to validate the proposed approach more robustly.

Influence of Contaminants Mercury and PAHs on Somatic Indexes of the European Hake (Merluccius merluccius, L. 1758).

This research investigates the dynamics of contaminant exposure in European hake (Merluccius merluccius, L. 1758) from the Adriatic Sea (Central Mediterranean Sea) by examining the levels of total mercury (THg) and polycyclic aromatic hydrocarbons (PAHs) in the muscle fish tissues. The study explores the correlations between these pollutants and somatic indexes to identify the early warning signals of pollution and ecological effects. The levels of pollutants are influenced by season and sex. Lipids appear to have a minimal effect on the PAH levels, whereas they exhibit a positive correlation with mercury levels in the muscle. No significant relationships between the pollutants and condition indexes were observed, except for a positive correlation between THg and the gonadosomatic index, indicating a potential impact on the reproductive health of fish. In contrast, PAHs showed no meaningful correlation with condition indexes. Differences in contaminant accumulations and lipid levels between sexes reflect variations in metabolic activity, reproductive costs, and adaptive strategies to seasonal changes and energy demands. This study highlights the importance of long-term monitoring to improve pollution management, environmental conservation, and the protection of marine organisms' health.

Elevated total mercury (THg) levels in water sources under the influence of artisanal and small-scale gold mining (ASGM) in Tanzania.

This study investigated the presence and distribution of mercury in water bodies under the influence of artisanal and small-scale mining (ASGM) activities in Tanzania, which continue to predominantly rely on mercury for gold extraction. Various water bodies available for domestic and animal use in mining communities were sampled from surface water sources in ASGM settlements during the rainy and dry seasons. Water samples were analysed using cold vapour atomic fluorescence spectrophotometer (CVAFS). The results indicate that most of water sources had THg levels above the WHO guideline of 1.0µg/L (1000ng/L) for safe drinking water. The levels were significantly higher during the wet season ranging from 3.4 to 96.3µg/L, whereas the range was from 0.84 to 2.12µg/L during the dry period. The higher THg values during the wet season are likely a result of increased lateral transport (e.g. via enhanced runoff) and physical properties of the waterways. Transportation and resuspension of matrix-bound mercury from surface soils and inflow of contaminated water from unprotected tailings were also observed to be potential means of lateral mercury transport. The lowest concentrations (0.846µg/L) were observed in water samples from the Mabubi River, upstream of a mining village. Downstream of the mining village in the same river, higher concentrations were observed in the Nungwe Bay region of Lake Victoria. In other surveyed mining settlements where there were no nearby rivers, pool water indicated high concentrations of THg, including levels above thresholds for safe human use. Immediate stringent measures are needed in order to ensure human and animal safety at ASGM mining settlements. Future investigation is suggested to focus on the distribution of mercury in different media, assessing the prevalence of different mercury species, and investigating the influence of weather and hydrological conditions on the impacts of mercury to organisms as part of the strategies to mitigate mercury pollution.

Total mercury and methylmercury levels in Brazilian Amazon fish: A scope review with meta-analysis and local population health risk assessment

IntroductionThe Brazilian Amazon has one of the richest biomes and the largest source of freshwater on the planet. However, anthropogenic activities have also turned this region into one of the highest points of human exposure to mercury ever recorded. Therefore, the aim of the present work was to perform a scope review with meta-analysis in order to evaluate the total mercury (THg) and methylmercury (MeHg) levels in Brazilian Amazon fish, as well as to carry out a local population health risk assessment. MethodsA literature search was systematically performed in research databases and gray literature, remaining 14 studies from 2017 to 2022 for final analysis. The studies were submitted to raw mean and subgroup meta-analysis, followed by a risk characterization and the calculation of a maximum safe consumption of fish for the Amazonian population. ResultsThe selected studies covered 4 Amazonian states, as well as included the analysis of >30 fish species of different trophic levels and sampling in >15 cities. The overall total mercury mean obtained for Brazilian Amazon fish was 0.29 ug g⁻¹. Significant difference was observed between THg levels according to fish trophic level (p < 0.05), which reinforces the MeHg biomagnification. When THg levels from all fish samples were pooled, it was not observed a significant difference among the Amazonian states and the fish sampling season. However, significant variations between microregions and species-specific variations over the seasons should not be discarded. All estimated daily methylmercury intake exceeded the reference dose of 0.1 ug kg BW⁻¹ day⁻¹, resulting in a hazard quotient (HQ) greater than 1 and indicating a risk of chronic exposure by the local population. The maximum safe consumption of fish calculated based on the overall total mercury mean was set as 31, 147 and 173 g week⁻¹ for children, adult women and adult men, respectively, which is much lower than the reality of consumption by the riverside communities (2870 g week⁻¹). ConclusionThere is an urgent need to reduce Hg exposure levels in the region as well as to recommend other protective nutritional strategies to the local population such as defining the fish species with lower mercury contamination levels and their safe weekly consumption.

Higher blood manganese level associated with increased risk of adult latent tuberculosis infection in the US population.

The associations between blood heavy metal levels and latent tuberculosis infection (LTBI) have not been fully elucidated. The aim of this study was to investigate the potential association between blood heavy metal levels and LTBI in adults using National Health and Nutrition Examination Survey data from 2011 to 2012. We enrolled 1710 participants in this study, and compared the baseline characteristics of participants involved. Multivariate logistic regression analysis, restricted cubic splines (RCS) analysis, along with subgroup analysis and interaction tests were utilized to explore the association between blood manganese (Mn) level and LTBI risk. Participants with LTBI had higher blood Mn level compared to non-LTBI individuals (p < 0.05), while the levels of lead, cadmium, total mercury, selenium, copper, and zinc did not differ significantly between the two groups (p > 0.05). In the fully adjusted model, a slight increase in LTBI risk was observed with each 1-unit increase in blood Mn level (OR = 1.00, 95% CI: 1.00-1.01, p = 0.02). Participants in the highest quartile of blood Mn level had a threefold increase in LTBI risk compared to those in the lowest quartile (OR = 4.01, 95% CI: 1.22-11.33, p = 0.02). RCS analysis did not show a non-linear relationship between blood Mn level and LTBI (non-linear p-value = 0.0826). Subgroup analyses and interaction tests indicated that age, alcohol consumption, and income-to-poverty ratio significantly influenced LTBI risk (interaction p-values<0.05). Individuals with LTBI had higher blood Mn level compared to non-LTBI individuals, and higher blood Mn level associated with increased LTBI risk.

Validation of a New Liquid Asymmetric-Electrode Plasma Optical Emission Spectroscopy (LAEP-OES) Method for Measurement of Total Mercury in Tuna.

Mercury intake is caused by eating seafood, such as tuna and other predatory fish species. To reduce the health risks of mercury intake, it is necessary to continuously measure and monitor mercury concentrations at fish farms and markets. We have developed a compact system that can detect multiple heavy metals by liquid asymmetric-electrode plasma optical emission spectroscopy (LAEP-OES). The validity of the LAEP-OES method for total mercury levels was evaluated using standard solutions, certified substances, and specimens of bluefin tuna and other fish species. All specimens were dissolved in 4 M lithium hydroxide solution and then dispensed into a sample reservoir well of the single-use measurement reagent pack. Total mercury levels were automatically measured within 15 min of placement into the dedicated equipment. A total of 102 fish specimens, classified into 10 fish species, were evaluated using the new method and the results were compared to those obtained from validated analytical methods. LOD (0.02 mg/kg), LOQ (0.07 mg/kg), repeatability (4.0%), intermediate precision (9.8%), and trueness (recoveries 107%) of the proposed method were within satisfactory limits for total mercury levels in fish. Additionally, when using various fish species, the method had a strong positive correlation with the results of cold-vapor atomic absorption spectrometry (CV-AAS, the official method) with Spearman rs = 0.984. The LAEP-OES method can be used for measuring total mercury levels in bluefin tuna. Total mercury measurement using this new method has the potential to be applied to other fish species. Total mercury levels in fish were measured using our unique analysis system. Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna distributed in the Japanese market were analyzed for total mercury in their wild and farmed fish varieties.

Exceptionally high levels of total mercury in deep-sea sharks of the Southeastern Mediterranean sea over the last ∼ 40 years

Deep-sea habitats are currently recognized as a hot spot for mercury (Hg) accumulation from anthropogenic sources, resulting in elevated concentrations of total mercury (THg) in deep-sea megafauna. Among them, deep-sea sharks (Class Chondrichthyes) are characterized by high trophic position and extended longevity and are, therefore, at high risk for mercury contamination. Despite this, sharks are overexploited by fishing activity in increasingly deeper water, worldwide, imposing health risks to human consumption. While it is imperative to better understand long-term mercury contamination in deep-sea megafauna, few historical data sets exist to capture this process. Here we explore four decades (1985–2022) of THg accumulation in five species of deep-sea sharks (G. melastomus, E. spinax, S. rostratus, C. granulosus, and D. licha) of the ultra-oligotrophic Southeastern Mediterranean Sea (SEMS) sampled during 19 research cruises. We exhibited exceptionally high THg levels (per length/weight), the highest as 16.6 μg g−1 (wet wt.), almost entirely (98.9 %; n = 298 specimens) exceeding the limit for safe consumption (0.3–0.5 μg THg g−1 wet wt.). The maximal THg levels of the long-lived species D. licha and C. granulosus in the SEMS were enriched by a factor of ∼ 7 and >10 compared to counterpart species from other oceanic areas, respectively. We attribute this to the ultra-oligotrophic conditions of the SEMS, which cause slower growth rates and dwarfism in deep-sea sharks, resulting in an extended exposure time to mercury contamination. In the long-lived species, C. granulosus and D. licha, a temporal increase of average THg levels of ∼ 80 % was recorded between 1987–1999 and 2021–2022. This likely reflects the long-term accumulation of historical anthropogenic Hg in deep-sea environments, which is further amplified in marginal seas such as the Mediterranean, impacted by global air pollution crossroads and surrounded by land-based pollution sources. Future consumption of products from deep-sea sharks is potentially high risk to human health.

Measuring Total Mercury Level in Local Food Fish Bangamary (Macrodon ancylodon) in Guyana

This research conducted in 2019 at the University of Guyana investigated the content of methylmercury in local food fish Macrodon ancylodon locally known as Bangamary. A total of 24 samples of M. ancylodon was purchased from the Meadow Bank Wharf in Guyana for analysis of total mercury level. Additionally, the size frequency at which mercury concentration is the highest was also evaluated. The results indicated that total mercury concentration in each sample of M. ancylodon was less than 0.5 mg/kg. With an average total mercury content of 0.10 mg/kg, adults had the greatest total mercury content, followed by juveniles (0.06 mg/kg) and young (0.02 mg/kg). This may be attributed to the carnivorous diet of M. ancylodon and the fact that the fish species is usually captured in the estuarine regions of the Demerara and Essequibo Rivers. These waterways are linked to mining areas in Guyana's interior region that discharge mercury contaminated water, which could be the reason why mercury is bioaccumulating in the tissue of the Bangamary.

Clinical, Laboratory and Neurodevelopmental Findings in Children from the Yanomami-Ninam Population Chronically Exposed to Methylmercury.

Despite legal safeguards, the Yanomami community faces challenges such as unauthorized incursions by gold miners, resulting in environmental degradation, particularly from mercury. This jeopardizes the health and food security of indigenous individuals, especially due to the consumption of contaminated fish. Ethnic and racial disparities persist in indigenous healthcare, marked by troubling health indicators such as malnutrition, anemia, and infectious diseases. This cross-sectional study, conducted in October 2022 in the Yanomami Indigenous Territory in the Amazon Forest, Brazil, presented clinical, laboratory, and neurodevelopmental findings in Yanomami children chronically exposed to methylmercury. The results revealed that Yanomami children exhibited weights and heights below expectations (median Z-scores of -1.855 for weight for age and -2.7 for height for age), a high prevalence of anemia (25%), low vaccination coverage (15%), and low IQ (average 68.6). The Total Hair Mercury (Total Hg) levels ranged from 0.16 µg/g to 10.20 µg/g (mean: 3.30 µg/g; median: 3.70 µg/g). Of 117 children tested, 93 children (79.4%) had levels ≥ 2.0 µg/g (had no significant difference between sex). Among the 58 children for whom it was possible to estimate the Total Intelligence Quotient (TIQ), the average value was 68.6, ranging from 42 to 92 points (median: 69.5; standard deviation: 10.5). Additionally, the lowest score on the IQ test was associated with 5 times the risk of having high levels of mercury in their hair, 2,5 fold the risk of having an older age, and almost 8 times the risk of consuming fish, adjusting for nut consumption. Notwithstanding the study's limitations, results suggest that mercury contamination from illegal mining activities on indigenous lands may negatively impact neurodevelopment in older indigenous children, particularly those fish consumers, despite the inherent benefits of fish consumption. Addressing other socio-environmental concerns is crucial for enhancing the overall health of the population.

Mercury exposure in riverine populations of Terra do Meio Extractive Reserves in the Xingu basin, Amazon, Brazil.

Amazon is a hotspot for mercury (Hg) contamination and Terra do Meio region, despite its protected status for sustainable use, has never been monitored for this element. Looking to address this gap, this study aimed to quantify capillary Hg concentration in riverine populations of Terra do Meio (Xingu Basin, Central Amazon, Brazil) and associated factors with high Hg levels (90 percentile). Hair samples from 182 individuals from Iriri, Riozinho do Anfrísio and Xingu Extractive Reserves (RESEX), aged between 18 and 70 years old, were collected to measure total mercury levels (HgT), and socioeconomic, demographic, and clinical-epidemiological data were annotated. Overall, high levels of Hg were observed (mean 4.985 µg/g, median 3.531µg/g) with significant differences between localities. Among the factors related to high capillary Hg levels, male gender, smoking habit, work in agriculture, livestock or extractivism, and residence in Iriri and Riozinho do Anfrísio RESEX were highlighted. A high prevalence of symptoms related to Hg intoxication, including anxiety, memory deficit, and lower limb problems, was observed. Overall, the results reveal that communities in these RESEXs are exposed to Hg and appear to be suffering from chronic health effects. Considering the increased anthropogenic alterations observed recently in the Amazon region and the subsequent amplified environmental bioavailability of Hg, further studies and mitigating actions are critical. This includes better surveillance of illegal anthropic activities and provision of ongoing education on this matter and incentives for dietary adaptations.

Determination of mercury in soil and water from a gold mining area in Karang Jaya Sub-district, Musi Rawas Utara, Indonesia

The present study focuses on the assessment of Hg distribution in both soil and water samples from the small-scale gold mining region of Karang Jaya Sub-district, Musi Rawas Utara Regency, South Sumatra Province. For over 30 years, this region has witnessed persistent utilization of mercury as an amalgam for gold extraction. The investigation encompasses an analysis of total mercury levels in soil samples obtained from Sukamenang, Muara Batang Empu, and Terusan Villages. As a comparative reference point devoid of gold mining activities, the neighboring Muara Lakitan Village was selected. The obtained results indicate a moderate to strong contamination level across the 30 sampled locations based on the Geoaccumulation Index (Igeo), with an average Igeo value of 2.6. Furthermore, Pollution Load Index (PLI) and Contamination Factor (CF) values demonstrate high contamination. Conversely, analysis of river water samples from 30 stations along the Rupit River reveals that most of the samples comply with quality standards (&lt;0.0005 mg/L), with an average value at 0.000322 mg/L; only four stations exhibit total Hg concentrations surpassing regulatory thresholds. All soil and river water samples from the control area (10 stations) exhibited no signs of pollution. Appropriate investments in technology, finance, and technical skills are needed to reduce mercury pollution due to small-scale gold mining activities.

Validation and Determination of Mercury in Yemeni Common Canned Tuna Using Direct Mercury Analyzer

The presence of Hg in canned tuna flesh is a major source of customer concern. Thus, the primary goal of this investigation was to evaluate total mercury levels in Yemeni canned tuna. Thirty-one samples of seven popular locally canned tuna brands were acquired from local stores in Sana'a. A Direct Mercury Analyzer was used to determine the mercury content. The linearity of the method was tested by assessing a series of mercury standards in triplicates at concentrations ranging from 20 to 500 ppb. The correlation coefficient for this method was 0.9993. The repeatability of the procedure was measured as intra-day variation and given as the relative standard deviation, which did not exceed 4.45%. This indicated the excellent precision of the method. Mercury recoveries from spiked actual canned tuna samples were between 96.61% and 100.49%, demonstrating excellent accuracy and an acceptable procedure for mercury measurement. The limits of detection and quantitation were 1.62 ppb and 5.4 ppb, respectively. The mercury content in 31 canned tuna samples was less than the 500 ppb standard imposed by the Yemeni Organization for Standards Metrology and Quality Control (YSMO).

Heavy metal baselines in cyprinidae of the Han River: a decade-long study on bioaccumulation trends and species-specific sensitivities

Despite numerous urban pollution sources, research on aquatic species bioaccumulation in the Han River is scarce. In this longitudinal study, we assessed baseline heavy metal (HM) concentrations in Cyprinidae, a major freshwater fish family in the Han River. Specifically, were evaluated copper (Cu), total mercury (THg), cadmium (Cd), lead (Pb), and chromium (Cr) levels in the muscle of common carp, crucian carp, and barbel steed. Common carp had the highest HM accumulation, with baseline concentrations of Cu, THg, Cd, Pb, and Cr at 0.877, 0.060, 0.003, 0.032, and 0.178 mg/kg, respectively. Larger fish exhibited greater bioaccumulation, with THg levels significantly correlated with fish length (correlation coefficients: 0.57 (p < 0.05)–0.74 (p < 0.001)). Notably, Cr accumulated more extensively in fish muscle than Pb, and the metal selectivity index (MSI) of THg in barbel steed was 2–3 times higher than in other fish species. The baseline concentrations determined in this study can serve as identifiers of the initial point of abnormal HM bioaccumulation in fish and provide foundational data for future long- or short-term fish monitoring.

Effects of blood mercury accumulation on DNA methylation levels in the Khorat snail-eating turtle (Malayemys khoratensis)

Mercury (Hg) has adverse effects on humans and wildlife. Hg exposure can cause significant alterations in DNA methylation, an epigenetic modification that causes various illnesses. Hg accumulation in the blood of the Khorat snail-eating turtle (Malayemys khoratensis) from northeastern Thailand was previously reported. Thus, this study aimed to assess total mercury (THg) levels in M. khoratensis blood and to examine the impact of these concentrations on DNA methylation (5-methylcytosine, 5-mC) levels. We divided turtles based on morphological characteristics into two groups, normal and deformed, and then the levels of each variable in both groups were assessed. The deformed group presented higher mean THg concentration and DNA methylation levels compared to the normal group; however, the differences were not significant. Additionally, we found no correlation between DNA methylation levels and THg concentrations in both groups. This study is the first attempt to investigate the relationship between mercury accumulation and DNA methylation in the blood of deformed freshwater turtles.

Non-carcinogenic human risk assessment of the consumption of infant formulas contaminated with total and organic mercury

The quality of food is paramount for the healthy growth and development of children, with nutrients and contaminants like mercury playing significant roles here. In this study, the levels of total mercury (THg) and methylmercury (MeHg) in infant formulas such as the first infant formula, hypoallergenic formula, comfort formula against colic and constipation, and anti-reflux formula were investigated. A validated and optimized cold atomic absorption spectrometry method of direct thermal decomposition with gold amalgamation was used. Analysis revealed notable variations in THg and MeHg levels among products. Basic infant formulas were characterized by the highest average and median THg values (6.14 µg/kg, and 3.27 µg/kg, respectively), while hypoallergenic preparations showed the lowest THg content (1.069 µg/kg on average and 0.922 µg/kg for the median). Methylmercury levels were the lowest in preparations meant to treat constipation and colic, whereas anti-reflux formulas were characterized by the highest mean and median values. Based on the evaluation of the Provisional Tolerable Weekly Intake realization for THg, and MeHg, it was determined that the mercury content in infant formulas was within acceptable consumption limits. However, the target hazard quotient, and the total hazard index revealed elevated mercury levels in certain products, potentially posing health risks.

Levels of Total Mercury and Health Risk Assessment of Consuming Freshwater Stingrays (Chondrichthyes: Potamotrygoninae) of the Brazilian Amazon.

Mercury is an element with potential risk to fish and those who consume it. Thus, this study aimed to determine the levels of total mercury (THg), carry out a health risk assessment related to the consumption of the freshwater stingrays Potamotrygon motoro, and determine the physical and chemical properties of the water where stingrays occur. Stingrays of the species P. motoro were obtained from the Amazon River, and samples of the animals' musculature were collected to determine THg levels. Risk assessment was conducted using pre-established formulas of estimated monthly intake (EMI), maximum monthly intake rate (IRmm), and hazard quotient (HQ). Three population scenarios were evaluated, considering both sexes and differences between rural and urban areas. There was no relationship between weight and THg concentration nor between total length and THg concentration. Higher EMI values were observed in rural children; for the IRmm, male children had the lowest consumption levels. For the hazard quotient, there was a similarity between the three age groups when comparing the male and female sexes. In addition, the representatives of the rural area always had lower values than the urban area. Freshwater stingrays, like other elasmobranchs, can be crucial animal species because they act as sentinels in studies that assess harmful chemicals like mercury.

Mercury distribution in fish organs sampled along the Mauritanian Atlantic coast and their potential human health risks

This paper aimed at assessing total mercury concentration in seven common fish species (Auxis rochei, Caranx rhonchus, Sardina pilchardus, Sardinella aurita, Sardinella maderensis, Scomber colias and Trachurus trecae) and a relationship between Hg organotropism and food regimes along the Mauritanian Atlantic coast. Results show that total mercury concentration in fish collected along five sites ranged from 0.027 to 0.533 mg/kg dry weight. Significant differences were observed among species depending on feeding behavior. Muscle tissues of carnivorous fish presented significantly higher levels of total mercury than that of omnivorous fish, except for Scomber colias, suggesting mercury biomagnification through the food chain. Significant differences in mercury concentrations were observed between muscle tissues and liver, for Auxis rochei, Trachurus trecae, and Caranx rhonchus.The mean concentrations in the different species are however low and none of the concentration values exceed the World Health Organization's threshold for human consumption.

Neurodevelopmental associations of prenatal and postnatal methylmercury exposure among first-grade children in the Kinan region, Japan

The most severe effects of methylmercury (MeHg) exposure during child development are thought to result from exposure during fetal life and childhood. However, comparing the neurodevelopmental effects of prenatal and postnatal MeHg exposure (PreMeHg and PostMeHg, respectively) remains unclear. We aimed to investigate the associations between neurodevelopmental indicators and PreMeHg or PostMeHg. The participants were 134 children in the first grade of elementary schools aged 7–8 years from the Kinan region, an area with high consumption of MeHg-rich whales and tunas in Japan. We measured MeHg levels in preserved umbilical cord tissues and total mercury (T-Hg) levels in children's hair to estimate PreMeHg and PostMeHg levels, respectively. Neuropsychological (intelligence quotient testing and Boston Naming Test) and neurophysiological (brainstem auditory evoked potential [BAEP], visual evoked potential [VEP], and color vision tests) studies were performed to evaluate the neurodevelopmental status. Multiple regression analyses were conducted according to sex. The geometric mean MeHg levels in preserved umbilical cord tissues and T-Hg levels in children's hair were 0.11 μg/g and 2.94 μg/g, respectively. Neither PreMeHg nor PostMeHg was related to neuropsychological indicators. Some associations between MeHg exposure and neurophysiological results were observed only in boys. N145 latency in VEPs was significantly prolonged with increasing PreMeHg (β: 12.01, 95% confidence interval [CI]: 0.648, 23.38). The III–V interpeak intervals in BAEP were significantly prolonged with increasing PreMeHg or PostMeHg (β [95% CI]: 0.142 [0.041, 0.243] and 0.159 [0.052, 0.265], respectively). After adjusting for PreMeHg, the association between PostMeHg and BAEP latencies disappeared. In conclusion, the latency in the auditory and visual pathways was significantly prolonged with increasing PreMeHg in boys. These findings suggest that male fetuses may be more susceptible to MeHg exposure.

Influence of Residential Combustion on Total Gaseous Mercury (TGM) Levels: a Preliminary Study at an Urban Megacity in Vietnam

Mercury (Hg) is a global pollutant that has gained monumental attention in recent decades due to its neurotoxicity and great bioaccumulation features. The atmosphere plays a key role in the movement of Hg in the environment, and residential combustion is a significant contributor to atmospheric Hg. However, there is a severe lack of research on the impact of Hg emissions from residential combustion in Southeast Asia (SEA). This study focused to illustrate the contribution of residential combustion on the level of total gaseous mercury (TGM) in a tropical megacity in southern Vietnam by conducting a short field campaign in February 2023. The mean TGM concentration during the study period was 2.27 ± 0.81 ng m-3, in which daytime TGM level (7 am – 7 pm, 2.56 ± 0.80 ng m-3) was significantly higher than at night (7 pm – 7 am, 1.58 ± 0.28 ng m-3), which could be attributed to local burning activities. The TGM concentration was also increased because of the increase in burning activities (i.e. burning joss paper and incense) during the Lantern Festival. Backward trajectory analysis suggested the domination of regional background air mass in the study area, implying that TGM concentration variation is mostly associated with local influences. We estimated that residential combustion caused a rise of around 70% in TGM concentration at the sampling site. Overall, this is the first study to illustrate the importance of Hg emissions from residential combustion in urban SEA region, laying a background for upcoming studies in atmospheric Hg in this region.