High-fish consumption and risk prevention: assessment of exposure to methylmercury in Portugal

Subsistence fishing in the Eeyou Istchee (James Bay, Quebec, Canada): A regional investigation of fish consumption as a route of exposure to methylmercury

Fishing is part of the traditional activities of Indigenous people in Canada. However, it is also a route of exposure to methylmercury, a known neurotoxicant, and this is a concern for those who rely on fish as part of their diet. The probable weekly intake (PWI) of methylmercury from six species of fish was calculated for Indigenous community members (N = 1406), grouped by age and sex, and compared to Canadian and international provisional reference doses to assess exposure. Mixed-effects regression models were also used to estimate the input of methylmercury into the blood, and Hazard Quotients (HQ) were used to assess potential effects. Of the species of fish in our study, walleye and lake trout contributed the most to methylmercury intake. There was a positive association between the consumption of walleye and the total blood mercury concentrations of mercury in women and men (R²_A = 0.40 and 0.47, respectively), and to a lesser extent, children. Similar results were observed for the consumption of lake trout. The 95th-percentile HQ for girls (3.16) and boys (3.18) from the consumption of lake trout was relatively high, and to a lesser extent, so was the HQ for walleye and pike. The consumption of some species of fish increases the exposure to methylmercury, however, taking a balanced approach, there are health benefits associated with the consumption of fish that must be considered. To mitigate future exposure to methylmercury, we recommend follow-up blood monitoring and local-geospatial-based assessments.

Effects of seafood consumption on mercury exposure in Norwegian pregnant women: A randomized controlled trial

BACKGROUND

Seafood provides nutrients that are important for optimal development of the unborn child. However, seafood is also a source of contaminants including mercury (Hg) and methylmercury (MeHg) that may have adverse effects on neurodevelopment of the fetus. Humans are predominantly exposed to MeHg through seafood consumption, however, levels of MeHg vary considerably between species.

OBJECTIVES

Investigate, in a randomized controlled trial (RCT) during pregnancy, if an increased intake of Atlantic cod (Gadus morhua), a fish species with relatively low levels of MeHg contamination, influences total hair Hg (THHg) concentrations in humans.

METHODS

Pregnant women (n = 137) were enrolled in the RCT "Mommy's Food" (2016-2017), which was designed to increase iodine status. Participants were randomly assigned to intervention (400 g of cod fillets per week) or control (continued habitual diet) groups for 16 weeks (gestational week 20-36). THHg concentrations were measured at baseline and post-intervention using thermal decomposition, amalgamation, and atomic absorption spectrophotometry (US EPA method 7473). The trial is registered in ClinicalTrials.gov, NCT02610959.

RESULTS

Post-intervention, the intervention group had median (inter-quartile range) THHg concentrations of 554 (392-805) µg/kg, and the control group 485 (341-740) µg/kg (p = 0.186). When adjusting for baseline THHg concentrations, there was a significant difference between the groups in those participants with baseline THHg concentrations below 534 µg/kg. Post-intervention, 8% of the study population exceeded the US EPA reference dose in hair (1,000 µg/kg) (intervention group: n = 6, control group: n = 4).

CONCLUSION

THHg concentrations were generally low in both study groups of pregnant women, despite the relatively high seafood intake. While the intervention with 400 g of cod per week slightly increased THHg concentrations, it did not lead to an increase in number of subjects exceeding the US EPA reference dose; a dose level at which no adverse effects are expected to occur over a period of lifetime exposure.

In Vitro Assessment of the Efficacy of a Macrocyclic Chelator in Reversing Methylmercury Toxicity

Methylmercury (MeHg) is a highly neurotoxic compound to which human populations are exposed via fish consumption. Once in cells, MeHg actively binds thiols and selenols, interfering with the activity of redox enzymes such as thioredoxin (Trx) and the selenoenzyme thioredoxin reductase (TrxR) which integrate the thioredoxin system. In fact, it has been shown that inhibition of this system by MeHg is a critical step in the unfolding of cell death. Current clinical approaches to mitigate the toxicity of MeHg rely on the use of chelators, such as meso-2,3-dimercaptosuccinic acid (DMSA) which largely replaced British anti-Lewisite or 2,3-dimercapto-1-propanol (BAL) as the prime choice. However, therapeutic efficacy is limited and therefore new therapeutic options are necessary. In this work, we evaluated the efficacy of a macrocyclic chelator, 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]aneN₄S), in preventing MeHg toxicity, namely by looking at the effects over relevant molecular targets, i.e., the thioredoxin system, using both purified enzyme solutions and cell experiments with human neuroblastoma cells (SH-SY5Y). Results showed that [15]aneN₄S had a similar efficacy to DMSA and BAL in reversing the inhibition of MeHg over purified TrxR and Trx by looking at both the 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) reduction assay and insulin reduction capability. In experiments with cells, none of the chelating agents could reverse the inhibition of TrxR by MeHg, which corroborates the high affinity of MeHg to the selenol in TrxR active site. [15]aneN₄S and BAL, unlike DMSA, could prevent inhibition of Trx, which allows the maintenance of downstream functions, although BAL showed higher toxicity to cells. Overall these findings highlight the potential of using [15]aneN₄S in the treatment of MeHg poisoning and encourage further studies, namely in vivo.

Risk assessment of methylmercury in pregnant women and newborns in the island of Madeira (Portugal) using exposure biomarkers and food-frequency questionnaires

Methylmercury (MeHg) is a contaminant present in fish which exerts a severe impact on health predominantly exhibiting neurotoxicity that might irreversibly affect fetal neurodevelopment. Fish consumption in Portugal is the third highest in the world, particularly high in regions with fishing tradition such as the Madeira Archipelago. Therefore, this study aimed at assessing the risk of exposure to MeHg in a population of pregnant women residing in Madeira. Blood samples from pregnant women (533) and umbilical cord (194) were collected from volunteer participants collected at primary health services in Madeira (Portugal) and analyzed for total mercury (HgT) level. A food-frequency questionnaire was used to estimate exposure and indices of risk while HgT in blood were correlated with estimated exposure. Analysis of HgT levels in blood indicated that 30% of pregnant women surpassed the maximum safe level of 10 µg/L recommended by the WHO, which was derived from the consumption of predatory fish, rich in MeHg. In addition, HgT levels in cord blood were 1.3 fold higher than in maternal blood, indicating the high risk of exposure to MeHg in this population. It is thus important to provide nutritional advice concerning fish consumption as a food choice in order to reduce fetal exposure and potential neurologic damage.

Children's Hair Mercury Concentrations and Seafood Consumption in Five Regions of Japan

Exposure to methylmercury (MeHg) during the foetal and postnatal periods is known to have adverse effects on children's development. However, little attention has been paid to MeHg exposure during early childhood in Japan. To examine the regional differences in MeHg exposure and seafood consumption and the association between MeHg exposure and seafood consumption and dental metal restorations, we measured the total mercury (T-Hg) concentration in hair as an MeHg exposure index, and using questionnaires, we measured the frequency and amount of seafood consumption and the presence of dental metal restorations in 118 children aged 3-6 years in five regions of Japan. The arithmetic and geometric means of the T-Hg concentrations in hair were 1.03 and 0.87 ppm, respectively, and approximately 40% of the children exceeded the United States Environmental Protection Agency recommendation of 1.0 ppm. Significant regional differences in the hair T-Hg concentrations were found among the five regions, and the regional differences were consistent with the traditional regional patterns of eating fatty fish. According to the regression analysis, the consumption of fatty fish, particularly tuna/swordfish, had a significant effect on hair T-Hg concentrations, whereas age, sex, the materials used for dental metal restorations, and other types of seafood or fish/shellfish had no significant effects.

Microplastics cause neurotoxicity, oxidative damage and energy-related changes and interact with the bioaccumulation of mercury in the European seabass, Dicentrarchus labrax (Linnaeus, 1758)

Microplastics pollution is a global paradigm that raises concern in relation to environmental and human health. This study investigated toxic effects of microplastics and mercury in the European seabass (Dicentrarchus labrax), a marine fish widely used as food for humans. A short-term (96 h) laboratory bioassay was done by exposing juvenile fish to microplastics (0.26 and 0.69 mg/L), mercury (0.010 and 0.016 mg/L) and binary mixtures of the two substances using the same concentrations, through test media. Microplastics alone and mercury alone caused neurotoxicity through acetylcholinesterase (AChE) inhibition, increased lipid oxidation (LPO) in brain and muscle, and changed the activities of the energy-related enzymes lactate dehydrogenase (LDH) and isocitrate dehydrogenase (IDH). All the mixtures caused significant inhibition of brain AChE activity (64-76%), and significant increase of LPO levels in brain (2.9-3.4 fold) and muscle (2.2-2.9 fold) but not in a concentration-dependent manner; mixtures containing low and high concentrations of microplastics caused different effects on IDH and LDH activity. Mercury was found to accumulate in the brain and muscle, with bioaccumulation factors of 4-7 and 25-40, respectively. Moreover, in the analysis of mercury concentrations in both tissues, a significant interaction between mercury and microplastics was found. The decay of mercury in the water increased with microplastics concentration, and was higher in the presence of fish than in their absence. Overall, these results indicate that: microplastics influence the bioaccumulation of mercury by D. labrax juveniles; microplastics, mercury and their mixtures (ppb range concentrations) cause neurotoxicity, oxidative stress and damage, and changes in the activities of energy-related enzymes in juveniles of this species; mixtures with the lowest and highest concentrations of their components induced different effects on some biomarkers. These findings and other published in the literature raise concern regarding high level predators and humans consuming fish being exposed to microplastics and heavy metals, and highlight the need of more research on the topic.

An epidemiological approach to characterise the human exposure pathways in a contaminated estuarine environment

This study's aim was to develop and implement an integrative epidemiologic cross-sectional study that allows identifying and characterising exposure pathways of populations living and working on the shores of a contaminated estuarine environment. Population residing in Carrasqueira, located on the Sado estuary with known contaminated areas was compared to another population on a noncontaminated estuary (Vila Nova de Mil Fontes - VNMF), considered a nonexposed population. Simple random samples of individuals were selected in each study population from the National Health Service Lists: 140 individuals were selected in Carrasqueira and 219 in VNMF. Participation rates were higher in the exposed group (62.5%, n=102 in Carrasqueira and 48.3%, n=100 individuals in VNMF). The same structured questionnaire was used in both populations, including questions on occupational activities, leisure activities, consumption of food (including fish and mollusks from the estuary) and use of water for human intake and agriculture. Results showed that a significantly higher proportion of Carrasqueira participants reported doing tasks in their job that promote direct (48.8% vs 1.2% in VNMF, p-value<0.001) or indirect (30% vs 11.9% in VNMF, p-value=0.004) contact with water from the estuary. Regarding seafood consumption, the exposed population of Carrasqueira had a higher frequency of consumption of cuttlefish (23.5% vs 9% in VNMF, p-value=0.007), sole (22.5% vs 4% in VNMF, p-value<0.001) and clams (18.6% vs 5.0 in VNMF, p-value=0.004). The comparative study design, with exposed and nonexposed populations living on the shores of two different estuaries allowed us to confirm the hypothesis of a higher risk of contamination from the contaminated estuarine environment. The study design and the selection of both populations were adequate for this type of epidemiologic study of potential routes of human contamination in a mixture of contaminated estuarine environment and can be used in other estuarine areas with similar environmental risk.

Assessment of Mercury Intake from Fish Meals Based on Intervention Research in the Polish Subpopulation

The paper's objective was to estimate weekly Hg intake from fish meals based on intervention research. Total Hg (THg) concentrations in blood and hair samples collected from men (n = 67) from an intervention study as well as muscular tissues of fresh and after heat-treating fish were determined using the thermal decomposition amalgamation atomic absorption spectrometry method (TDA-AAS) using direct mercury analyzer (DMA-80). The mean of the estimated weekly intake (EWI) was estimated at 0.62 μg/kg bw/week in the range 0.36-0.96 μg/kg body weight (bw) /week through the consumption of 4 edible marine fish species every day (for 10 days) by the participants from the intervention research in Lodz, Poland. The Hg intake in the volunteers in our intervention study accounted for 38.6% of the provisional tolerable weekly intake (PTWI) (1.6 μg/kg bw, weekly) value. The average Hg concentration in the analyzed fish ranged from 0.018 ± 0.006 mg/kg wet weight (Gadus chalcogrammus) to 0.105 ± 0.015 mg/kg wet weight (Macruronus magellanicus). The results for the average consumers were within PTWI of methylmercury (MeHg). Moreover, the average concentration of Hg in the selected fish after heat treatment did not exceed the maximum permitted concentrations for MeHg (MPCs = 0.5 mg/kg wet weight) in food set by the European Commission Regulation (EC/1881/2006). Hence, the risk of adverse effects of MeHg for the participants is substantially low.

Biomarkers of mercury toxicity: Past, present, and future trends

Mercury (Hg) toxicity continues to represent a global health concern. Given that human populations are mostly exposed to low chronic levels of mercurial compounds (methylmercury through fish, mercury vapor from dental amalgams, and ethylmercury from vaccines), the need for more sensitive and refined tools to assess the effects and/or susceptibility to adverse metal-mediated health risks remains. Traditional biomarkers, such as hair or blood Hg levels, are practical and provide a reliable measure of exposure, but given intra-population variability, it is difficult to establish accurate cause-effect relationships. It is therefore important to identify and validate biomarkers that are predictive of early adverse effects prior to adverse health outcomes becoming irreversible. This review describes the predominant biomarkers used by toxicologists and epidemiologists to evaluate exposure, effect and susceptibility to Hg compounds, weighing on their advantages and disadvantages. Most importantly, and in light of recent findings on the molecular mechanisms underlying Hg-mediated toxicity, potential novel biomarkers that might be predictive of toxic effect are presented, and the applicability of these parameters in risk assessment is examined.

Perceptions about mercury and lead in fish consumed in Lake Albert fishing communities Uganda

Fish consumption is a lifestyle in fishing communities influenced by individual and communal perceptions. However, information about individual perceptions about fish consumption in the vulnerable fishing community in a developing country is lacking. Without this study, the benefits of fish consumption in a vulnerable community may not be realized. Data collection was executed using key informant interviews and survey structured questionnaires. The key informants include fisheries, community development, veterinary, community and environmental officers. The household heads were the respondents. The Qualitative data was organized and queried using QSR Nvivo 10 and quantitative data analyzed with SPSS version 22. The perceived benefits of eating fish are health, income, nutrition and manhood. The perceived risks are Stigma and ill health. The factors increasing fish consumption are heedless of fish consumption benefits (p = 0.041) and household size i.e. number of adults more than seven (p = 0.020). Those decreasing are methods of preparation of fish i.e. boiling and frying (p = 0.019 and p = 0.010) and oblivious about organizations dealing with fishing activities (p = 0.029). An awareness campaign is needed to demystify the health benefits and fallacies of fish consumption. The knowledge on individual perceptions associated with fish consumption will increase fish consumption but with fewer risks.

Risk estimates for children and pregnant women exposed to mercury-contaminated Oreochromis niloticus and Lates niloticus in Lake Albert Uganda

Exposure to mercury contaminated fish predisposes populations particularly children and pregnant women to various health hazards including neurotoxicity, reproductive abnormalities and cognitive disorders. Earlier studies in the Lake Albert community have demonstrated the presence of mercury in Nile tilapia and Nile perch. However, the risk estimates for vulnerable groups such as Children and pregnant women is not well documented. Secondary data-set from previous studies were employed comprising family household size and fish consumption history, fish consumption quantity and frequency and mercury levels in fish species in comparison with FAO/WHO guidelines. Data collected was used to establish the hazard quotients (HQs) for the vulnerable group and the general population. A risk model was developed using iRISK to demonstrate the Disability Adjusted Life Years (DALYs) for eating different parts of the fish (muscle and bellyfat). HQ values (HQ = 2.05) above one for the vulnerable group were realized especially with Nile perch muscle. The highest DALYs (0.111) was obtained with tilapia muscle consumption. The study outcome reveals that vulnerable populations are at risk of non-carcinogenic complications. Therefore, there is a need for sensitization of the community especially the vulnerable groups about risks associated with consuming mercury-contaminated fish.

Children's health risk and benefits of fish consumption: risk indices based on a diet diary follow-up of two weeks

Several epidemiological studies indicate that fish intake is associated with neurocognitive development and visual outcomes in children attributed to long-chain polyunsaturated fatty acids (PUFA). However, methylmercury (MeHg) represents the most toxic and abundant form of environmental mercury (Hg) exposure to humans and exposure occurs primarily through fish consumption. The objective of the study was to describe fish consumption during childhood in Portugal, estimating the intake of Hg from fish and calculating the indices of risk. The group consisted of 233 infants and students aged 7-11 yr and attending 5 primary schools in Lisbon, Amadora, and Sesimbra. Information regarding food consumption habits was collected through a food diary during 2 weeks, completed under the supervision of teachers and parents, where participants registered what was ingested for lunch and dinner during that period. The exposure assessment and indices of risk were calculated for each participant. Individuals were classified according to weekly intake and indices of risk determined per group. In addition, the methods used to collect information on fish intake habits, a food frequency questionnaire and diet diary, are described in relation to quality of information provided. The mean value of fish meals per week was approximately 5. The calculated indices of risk reached values above 1 in more than 50% of the studied population, demonstrating the presence of risk in subsets of the population. While Portuguese children represent an important group of fish consumers, this does not manifest as appreciable benefit with respect to omega-3 ingestion, as children ingest half or less of the recommended value (200 mg/d of omega-3), which is equivalent to being exposed to risk for Hg intoxication. The choice of fish species shows lack of knowledge of fish characteristics. Therefore, risk communication and population education need to be established to prevent consumption of predatory fish species that contribute to the increase in risk toxicity and to encourage ingestion of prey fish, which represent significant levels of high-value nutrients such as PUFA.

Exposure assessment of pregnant Portuguese women to methylmercury through the ingestion of fish: cross-sectional survey and biomarker validation

Methylmercury (MeHg) contamination is a critical public health problem in Portugal, where fish is an important component of the daily diet. The Portuguese are the third largest consumers in the world (after Japan and Iceland) but first in Europe. Prenatal exposure to MeHg is believed to be linked to fetal/child neurodevelopment and behavioral impairments due to the neurotoxicity of the compound. The objective of this study was to assess the exposure of pregnant Portuguese women to mercury (Hg) due to fish consumption, calculating the indices of risk and confirming exposure through analyses of a biomarker of exposure. The study consisted of a cross-sectional evaluation of 343 pregnant women recruited at their visit to two antenatal care units in Lisbon, Portugal. A food frequency questionnaire was used to estimate prenatal exposure. Total Hg levels in hair were analyzed by atomic absorption, in samples from 186 women. The average fish consumption was 3.1 meals per week. Median Hg level in the hair was 1.26 μg/g (range: 0.07-5.3 μg/g). The mean calculated risk index was 0.81; however, 28% of the pregnant women ingested levels above the provisional tolerable weekly intake (PTWI) level recommended by the World Health Organization (WHO; 1.6 mg/kg per body weight), indicating the possibility of risk due to MeHg exposure. Multiple linear regression analysis showed the risk index was reliably predicted from predatory fish species and number of fish meals consumed per week. Ingestion of black and silver scabbard fish as well as mixed predatory fish cooked in traditional dishes enhanced the toxicity risk. In conclusion, some exposure levels exceeded the reference value; therefore, nutritional counseling needs to be provided to populations at risk.

Methyl mercury exposure from fish consumption in vulnerable racial/ethnic populations: probabilistic SHEDS-Dietary model analyses using 1999-2006 NHANES and 1990-2002 TDS data

NHANES subjects self-identified as "Asian, Pacific Islander, Native American, or multiracial" (A/P/N/M) have higher levels of blood organic mercury than other racial/ethnic groups; however, the reasons for this have been unclear. This research uses exposure modeling to determine the reasons for elevated blood methylmercury (MeHg) levels, and also extends previous analyses of observed NHANES blood levels. The probabilistic SHEDS-Dietary model was applied, using MeHg fish residue data from FDA's Total Diet Study (1990-2002) combined with NHANES/WWEIA (1999-2006) fish consumption data, to generate exposure estimates by race/ethnicity, age group, and fish type. Statistical analyses of blood methylmercury levels in the (6 times larger) 1999-2006 NHANES data were compared against previous published results for 1999-2002 data. The A/P/N/M group has higher fish intake, modeled MeHg exposures, and blood levels than the general population and other racial/ethnic groups. Tuna, other saltwater fish, and other freshwater fish are key food types driving dietary MeHg exposure. The 1-<3 years-old A/P/N/M group has the highest mean dietary MeHg intake per body weight (0.06 μg/kg/day; ~2.3 times higher than the rest of the population). Fish intake and modeled exposure predictions correlate well with NHANES blood biomarker levels. This study, using the SHEDS-Dietary model with national data, reinforces and expands upon previous observations that dietary exposure via fish consumption is an important route for methylmercury intake by the general population, and especially for racial/ethnic groups with higher fish consumption. These probabilistic dietary modeling approaches could be applied for local populations (e.g., tribes) and other chemicals and foods, if data are available.

Mercury bioaccumulation in the spotted dogfish (Scyliorhinus canicula) from the Atlantic Ocean

The annual and life-cycle mercury bioaccumulation pattern in selected tissues of the economically relevant Elasmobranchii species Scyliorhinus canicula was studied, and the risks associated with its consumption evaluated. Preferential mercury bioaccumulation occurred in muscle tissue, and followed the order muscle>heart>liver>gills>pancreas. Total mercury in muscle tissue ranged from 0.13mgkg(-1) (wwt) in 1+year old males to 0.8mgkg(-1) (wwt) in 8+ year old mature females, with no significant differences found between genders, and no clear lifespan bioaccumulation pattern observed, except for mature females. Organic mercury in the muscle ranged from 0.05mgkg(-1) (wwt) to 0.52mgkg(-1) (wwt), corresponding to an average of 70% of total mercury content. In mature females, a significant correlation (R=0.99, P=0.01) was found between size and organic mercury fraction, suggesting reproduction as an important factor controlling organic mercury bioaccumulation in the spotted dogfish.

Mercury content in the trophic chain of the Tanew River, Poland, ecosystem

Mercury (Hg) is a highly toxic metal posing a hazard to water ecosystems. This investigation was aimed at determining Hg content in the Tanew River, Poland, and subsequent transfer to fish inhabiting this lake. The area studied included approximately a 50-km distance of the river, with 5 sampling locations selected. Samples of water and bottom sediments were collected from 10 sites along the river-bank zone for each location. At the same location, fish were caught and samples of coastal water plants were collected. Fish that were caught included the following species: chub (Leuciscus cephalus), pike (Esox lucius), ide (Leuciscus idus), and roach (Rutilus rutilus). Dominanting species of water plants included reed-mace (Typha angustifolia), rigid hornwort (Ceratophyllum demersum), and water knotweed (Polygonum amphibium). Mercury content in samples of water, bottom sediments, water plants, and fish tissues (muscles and gills) were determined by using a Mercury/MA-2000 system (NIC, Japan). The average Hg content in the waters of Tanew ranged between 1 and 5 microg/L, and in the bottom sediments ranged between 17 and 214 microg/kg dry weight, which are characteristic values for typical unpolluted areas. The highest Hg contamination of waters and bottom sediments was found where the Tanew estuary enters the San River. Mercury levels in fish from the Tanew delta appeared to be higher compared to other sampling sites. Data indicated that even if water environment is contaminated with Hg to a limited extent, fish accumulate this metal at higher levels, probably due to a bioaccumulation or bioconcentration factor.

Estimation of tolerable upper intake level (UL) of active aloe

It has been reported that an active aloe polysaccharide isolated from Aloe barbadensis Miller exerted various pharmacological effects, such as anti-inflammatory, wound healing, anti-hepatitis, anti-gastric ulcer, and anti-tumorigenicity in animals. Adverse health effects of aloe are of concern in humans. Therefore, this study was conducted to investigate a tolerable upper intake level (UL) of active aloe or a maximal allowable daily intake (ADImax) of active aloe based on 4-wk oral toxicity investigation in ICR mice. An active aloe was daily administered to male and female ICR mice for 4 wk at different dose levels (0, 120, 600, 3000, or 15,000 mg/kg body weight [bw]). All animals were sacrificed at the end of the experiment and changes of body weight, food consumption, organ weights, and hematological and biochemical parameters were recorded. In this study, no changes in clinical signs, urinalysis, or hematological or biochemical analysis were observed. In females, a dose-dependent quantitative decrease in albumin (ALB) levels was observed, but it was not significant, due to wide interindividual variations. A significant decrease in male kidney weight was observed from the 120-mg/kg to the 15,000-mg/kg bw treatment groups, and blood urea nitrogen (BUN) levels were also quantitatively lower. A dose-dependent reduction in the body weight of females was also observed, which might be related to less food consumption. Based on the reduced kidney weights in males, the lowest-observed-adverse-effect level (LOAEL) of an active aloe was estimated to be 120 mg/kg bw in male ICR mice, and the UL or ADImax was 0.4 mg/kg bw/d [(120 mg/kg bw/d)/(100 for safety factor) x (3 for modifying factor)], or 24 mg for a 60-kg adult (24 mg x 200 = 4.8 g of aloe gel/d/adult), assuming that consumers utilize active aloe for a month. Data showed that an active aloe did not induce any remarkable subacute toxic effects, but decreased male kidney weights, which requires further investigation.

Dietary exposure and risk assessment of mercury from the Korean total diet study

As a national project, obtaining information on the amount of heavy metal exposure of individuals through food intake is an important basic parameter for risk assessment. This study was conducted to evaluate dietary exposure levels and various risks from mercury (Hg) in Korean foods. In total, 342 samples comprising 114 food items were collected and then cooked prior to analysis. As found by Hg analysis, the mean content of metal in the fish and shellfish group was highest among the 15 Korean food groups. The total daily amount of Hg intake from typical Korean foods was 2.40 microg/person/d. The daily amount (microg/person/d) of Hg intake from each food group was 0.155 in grains and cereals, 0.008 potatoes and starch, 0.005 sugars and sweets, 0.0093 pulses, 0.0018 nuts and seeds, 0.203 vegetables, 0.027 fruits, 0.021 meats and poultry, 0.004 eggs, 1.826 fish and shellfish, 0.022 seaweed, 0.043 milk and dairy products, 0.008 oils and fats, 0.042 beverages, and 0.023 seasonings. The fish and shellfish group contributed most to total dietary intake at 76%. For risk assessment, probable daily intake (PDI) was calculated and compared with provisional tolerable weekly intake (PTWI) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The level of Hg intake through fish and shellfish of 0.001 mg/kg body weight bw/wk corresponded to 4.54% of the PTWI value of 0.005 mg/kg bw/wk, the safety standard for JECFA. The level of Hg intake through selected foods from the Food list for Koreans was 0.001 mg/kg bw/wk, corresponding to 5.95% of PTWI value. Therefore, overall intake was at levels below the recommended JECFA levels. The relative gender Hg hazard from Korean foods was 6.26% and 5.5% for males and females, respectively. The relative age Hg hazard from Korean foods was, 8.9% in those 3-6 yr old, 6.7% in those 7-12 yr old, 5.2% in those 13-19 yr old, 5.9% in those 20-29 yr old, 6.3% in those 30-49 yr old, 5.6% in those ages 50-64 yr, and 3.7% in the group of those over 65 yr of age. Relative regional Hg hazard from Korean foods was 6.3% in urban versus 5.5% in rural areas. Thus, the amount of Hg intake through consumption of Korean foods was found to be at a relatively safe level. These data may be thus used to establish safety standards for fish and shellfish consumption.

Diphenyl diselenide, a simple organoselenium compound, decreases methylmercury-induced cerebral, hepatic and renal oxidative stress and mercury deposition in adult mice

Oxidative stress has been pointed out as an important molecular mechanism in methylmercury (MeHg) intoxication. At low doses, diphenyl diselenide ((PhSe)2), a structurally simple organoselenium compound, has been shown to possess antioxidant and neuroprotective properties. Here we have examined the possible in vivo protective effect of diphenyl diselenide against the potential pro-oxidative effects of MeHg in mouse liver, kidney, cerebrum and cerebellum. The effects of MeHg exposure (2 mg/(kg day) of methylmercury chloride 10 ml/kg, p.o.), as well as the possible antagonist effect of diphenyl diselenide (1 and 0.4 mg/(kg day); s.c.) on body weight gain and on hepatic, cerebellar, cerebral and renal levels of thiobarbituric acid reactive substances (TBARS), non-protein thiols (NPSH), ascorbic acid content, mercury concentrations and activities of antioxidant enzymes (glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD)) were evaluated after 35 days of treatment. MeHg caused an increase in TBARS and decreased NPSH levels in all tissues. MeHg also induced a decrease in hepatic ascorbic acid content and in renal GPx and CAT activities. Diphenyl diselenide (1 mg/kg) conferred protection against MeHg-induced hepatic and renal lipid peroxidation and at both doses prevented the reduction in hepatic NPSH levels. Diphenyl diselenide also conferred a partial protection against MeHg-induced oxidative stress (TBARS and NPSH) in liver and cerebellum. Of particular importance, diphenyl diselenide decreased the deposition of Hg in cerebrum, cerebellum, kidney and liver. The present results indicate that diphenyl diselenide can protect against some toxic effects of MeHg in mice. This protection may be related to its antioxidant properties and its ability to reduce Hg body burden. We posit that formation of a selenol intermediate, which possesses high nucleophilicity and high affinity for MeHg, accounts for the ability of diphenyl diselenide to ameliorate MeHg-induced toxicity.