Estimation of acceptable mercury intake from fish in Taiwan

Isolation and characterization of mercury and multidrug-resistant Citrobacter freundii strains from tannery effluents in Kolkata, India

Mercury (Hg) is one of the most potent toxic heavy metals that distresses livestock, humans, and ecological health. Owing to uncontrolled exposure to untreated tannery industrial effluents, metals such as Hg are increasing in nature and are, therefore, becoming a global concern. As a result, understanding the thriving microflora in that severe condition and their characteristics becomes immensely important. During the course of this study, two Hg-resistant bacteria were isolated from tannery wastewater effluents from leather factories in Kolkata, India, which were able to tolerate 2.211 × 10- 3 M (600 µg/ml) Hg. 16 S rDNA analysis revealed strong sequence homology with Citrobacter freundii, were named as BNC22A and BNC22C for this study. In addition they showed high tolerance to nickel (Ni) and Chromium (Cr) at 6.31 × 10- 3 M (1500 µg/ml) and 6.792 × 10- 3 M (2000 µg/ml) respectively. However, both the isolates were sensitive to arsenic (As) and cadmium (Cd). Furthermore, their antibiotic sensitivity profiles reveal a concerning trend towards resistance to multiple drugs. Overuse and misuse of antibiotics in healthcare systems and agriculture has been identified as two of the main reasons for the decline in efficacy of antibiotics. Though their ability to produce lipase makes them industrially potent organisms, their competence to resist several antibiotics and metals that are toxic makes this study immensely relevant. In addition, their ability to negate heavy metal toxicity makes them potential candidates for bioremediation. Finally, the green mung bean seed germination test showed a significant favourable effect of BNC22A and BNC22C against Hg-stimulated toxicity.

Mercury abatement in the environment: Insights from industrial emissions and fates in the environment

Mercury's neurotoxic effects have prompted the development of advanced control and remediation methods to meet stringent measures for industries with high-mercury feedstocks. Industries with significant Hg emissions, including artisanal and small-scale gold mining (ASGM)-789.2 Mg year-1, coal combustion-564.1 Mg year-1, waste combustion-316.1 Mg year-1, cement production-224.5 Mg year-1, and non-ferrous metals smelting-204.1 Mg year-1, use oxidants and adsorbents capture Hg from waste streams. Oxidizing agents such as O3, Cl2, HCl, CaBr2, CaCl2, and NH4Cl oxidize Hg0 to Hg2+ for easier adsorption. To functionalize adsorbents, carbonaceous ones use S, SO2, and Na2S, metal-based adsorbents use dimercaprol, and polymer-based adsorbents are grafted with acrylonitrile and hydroxylamine hydrochloride. Adsorption capacities span 0.2-85.6 mg g-1 for carbonaceous, 0.5-14.8 mg g-1 for metal-based, and 168.1-1216 mg g-1 for polymer-based adsorbents. Assessing Hg contamination in soils and sediments uses bioindicators and stable isotopes. Remediation approaches include heat treatment, chemical stabilization and immobilization, and phytoremediation techniques when contamination exceeds thresholds. Achieving a substantially Hg-free ecosystem remains a formidable challenge, chiefly due to the ASGM industry, policy gaps, and Hg persistence. Nevertheless, improvements in adsorbent technologies hold potential.

Blood and seminal plasma mercury levels and predatory fish intake in relation to low semen quality

Declining human sperm quality has been demonstrated in several recent studies. Age, environmental factors, and nutritional factors can affect semen quality. Mercury (Hg) is considered a male reproductive toxicant. Animal studies indicated that exposure to Hg can cause DNA damage, sperm dysfunction, and decreased sperm motility. Some previous studies also revealed that blood Hg levels in infertile or subfertile males were higher than those in normal males. In this study, we recruited 84 male participants from a reproductive medical center and investigated the Hg, lead, and selenium levels in blood and seminal plasma. Participants were divided into two groups, low- and high-quality semen groups, according to the World Health Organization reference values for human semen characteristics. The distribution of blood reproductive hormones and information on participants' lifestyle and medical history were collected from structured questionnaires. Average Hg levels in blood were 9.3±5.9 versus 8.9±5.9 and in seminal plasma were 1.26±0.61 versus 1.05±0.52 μg/L in the low- and high-quality semen groups, respectively. There was a dose-dependent relationship between blood Hg levels and normal sperm morphology (p=0.02). Participants with predatory fish intake and high blood Hg level had lower sperm with a normal morphology. Therefore, predatory fish intake may be a critical risk factor for elevated Hg levels in males and cause low semen quality.

Methylmercury levels in commonly consumed fish and methylmercury exposure of children and women of childbearing age in Hong Kong, a high fish consumption community

BACKGROUND

Despite high fish consumption levels of Hong Kong residents, little is known about the MeHg exposure levels of Hong Kong high-risk populations (i.e. young children and women of childbearing age).

OBJECTIVES

To investigate the MeHg levels in fish commonly consumed in Hong Kong and assess the exposure levels of local kindergarten children and women of childbearing age.

METHODS

A community-based survey was conducted in randomly recruited local kindergartens. The MeHg concentrations of the most commonly consumed fish items were measured. Based on their fish consumption data, subjects' MeHg exposure levels were estimated and compared with the reference dose (RfD) set by U.S. Environmental Protection Agency.

RESULTS

A total of 2917 mother-child pairs were recruited. The MeHg levels of the fish samples ranged from < 2-1498.7 ng/g. Six frozen cod fish samples contained MeHg levels exceeding the local legal limit of 500 ng/g. The median estimated MeHg intake for children and mothers were 0.29 and 0.22 µg/kg bw/wk, respectively. Approximately 16% children and 9% mothers exceeded the RfD.

CONCLUSIONS

Apart from frozen cod fish, most fish species commonly consumed in Hong Kong had low MeHg content. Although the majority of our subjects were exposed to low MeHg levels, high fish consumers could still exceed the RfD and are potentially at risk of MeHg toxicity. To avoid excessive MeHg exposure, we suggest that young children and their mothers may consume a variety of locally available fish, but avoid consumption of frozen cod fish.

Mercury levels in human population from a mining district in Western Colombia

A biomonitoring study was carried out to examine the adverse impacts of total mercury in the blood (HgB), urine (HgU) and human scalp hair (HgH) on the residents of a mining district in Colombia. Representative biological samples (scalp hair, urine and blood) were collected from volunteered participants (n=63) to estimate the exposure levels of THg using a Direct mercury analyzer. The geometric mean of THg concentrations in the hair, urine and blood of males were 15.98μg/g, 23.89μg/L and 11.29μg/L respectively, whereas the females presented values of 8.55μg/g, 5.37μg/L and 8.80μg/L. Chronic urinary Hg (HgU) levels observed in male workers (32.53μg/L) are attributed to their long termed exposures to inorganic and metallic mercury from gold panning activities. On an average, the levels of THg are increasing from blood (10.05μg/L) to hair (12.27μg/g) to urine (14.63μg/L). Significant positive correlation was found between hair and blood urinary levels in both male and female individuals. Thus the present biomonitoring investigation to evaluate the Hg levels and associated health issues would positively form a framework for further developmental plans and policies in building an ecofriendly ecosystem.

Assessment of metal levels in foodstuffs from the Region of Valencia (Spain)

Concentrations of lead, mercury, cadmium, arsenic, tin, copper and chromium were measured in a study carried out in 2010-2011. A total of 8100 food samples were collected and composite samples for 12 food groups were analysed for metal concentration levels. Metal levels were, in general, below the maximum levels set by the current European legislation. The fish group presented the highest Cd, Hg and As levels, whereas sweeteners and condiments group was the most contaminated food group by Pb, Cr and Sn and the meat group had the highest concentrations of Cu. The results of this study are generally similar to or lower than those observed in other studies conducted in other countries, except in the case of Hg, for which high values were obtained, mainly in swordfish. In addition, this survey confirms a decreasing tendency when compared with other studies carried out in Spain.

Path analysis of prenatal mercury levels and birth weights in Korean and Taiwanese birth cohorts

Prospective cohort studies of the effect of mercury (Hg) exposure on birth weight have shown conflicting results. We combined data from Taiwanese and Korean birth cohorts, and assessed the effects of Hg exposure on birth weight. The first cohort was drawn from the Mothers and Children's Environmental Health (MOCEH) study performed in Korea from 2006 to 2010. The second cohort was enrolled from 2004 to 2005 and included singleton term births from the Taiwan Birth Panel Study (TBPS). In total, 1147 pregnant women were included in this study. A pooled analysis was performed to obtain combined estimates of the association between prenatal total Hg exposure and birth weight. A significant negative association between maternal and cord blood Hg and birth weight in the high-Hg group (Hg level>25th percentile) was detected (maternal blood: β=-0.056; 95% CI, -0.100 to -0.013, cord blood: β=-0.075; 95% CI, -0.121 to -0.028). Hg level showed a negative coefficient in the path analysis, indicating an adverse effect on birth weight (total effects: β=-0.177, P=0.01 in MOCEH, β=-0.204, P=0.03 in TBPS), but fish consumption exhibited a strong positive coefficient. In addition, fish consumption exerted a significant indirect effect on birth weight through exposure to cord blood Hg. Exposure to hazardous contaminants and beneficial nutrients may be highly correlated in those who frequently consume fish. Moreover, Hg in cord blood may adversely affect birth weight.

Bioaccumulation and potential sources of heavy metal contamination in fish species in Taiwan: assessment and possible human health implications

In this study, tissues of five fish species prevalent in the Houjing River were analyzed for heavy metal concentrations. Results show concentrations of such metals to be much higher than internationally recommended standard limits (as determined by the WHO and FAO) and other similar studies. Heavy metal contamination of fish in the Houjing River is hence significant. High hazard and carcinogenic risk related to the Houjing River's fish was proven based on target hazard quotient (THQ) and target cancer risk (TR) estimations. In fact, four of the five species studied present THQ levels higher than 1, and seven TRs of zinc (Zn) and arsenic (As) are higher than 10^-4. Despite lower estimated daily intake (EDI) of fish in the area (per recommended daily allowance guidelines), possible heavy metal bioaccumulations in fish stock pose a high health risk for human consumption. From our analyses, the highest bioaccumulation factor (BAF) estimated above 1000 was of Zn. Among the fish species studied, Oreochromis niloticus possesses the ability to accumulate copper (Cu) and Zn dramatically. Pearson's correlation matrix showed a positive correlation between Cu and As, attributed to multiple industrial activities along the river. Hierarchical cluster analysis of results based on sampling stations exhibits three clusters and may be linked to the type of industrial activities specific to that area. More intensive study is needed in order to further determine the toxic metals in fish. Reporting of contaminant levels must be compared with optimal health criteria guidelines. Our study, while showing the severity of heavy metal contamination in fish stock, calls for urgent, sustained, and targeted actions by both governmental authorities and the local scientific community-to help prevent and mitigate the situation and ensure the physical well-being of local inhabitants.

Assessment of fish consumption and mercury exposure among pregnant women in Jamaica and Trinidad & Tobago

BACKGROUND

Fish is an essential and traditional element in the diet of most Caribbean people. However it also contains methylmercury which can have severe effects on fetal neurodevelopment. The objective of this study was to assess the fish intake of a selected group of pregnant women from Jamaica and Trinidad & Tobago and evaluate prenatal mercury exposure, using the placenta as a biomarker.

METHOD

Food frequency questionnaires and placental samples were obtained from participating parturients at the time of delivery at the University Hospital of the West Indies in Kingston, Jamaica (N = 100, from November 2012 to March 2013) and the Mt Hope Women's hospital in St Joseph, Trinidad & Tobago (N = 30, in June 2015). The participants were asked to identify the species of fish and the frequency of consumption. Placental samples were analysed for mercury using cold vapour atomic absorption.

RESULTS

The fish consumption preferences for pregnant women, varies based on the marine fish catch production of each country. The main fish species that contributed to the highest estimated methylmercury exposure in Jamaica and Trinidad & Tobago were cod and shark, respectively. There was a weak association between maternal fish intake and placental mercury concentrations. The mean placental mercury concentrations in Jamaica and Trinidad & Tobago were 0.74 ± 0.5 μg/kg and 1.46 ± 0.6 μg/kg, wet weight respectively.

CONCLUSION

The results from this study showed an influence of Caribbean fish intake preferences on mercury exposure and thus a recommendation for continuous bio-monitoring for public health purposes.

Determination of total mercury in fish and sea products by direct thermal decomposition atomic absorption spectrometry

A Zeeman Mercury analyzer Model RA-915(+) (Lumex, St. Petersburg, Russia), based on the direct thermal evaporation of Hg from solid samples was used for developing a method for the determination of Hg in fish and other seafood. The method does not require any chemical pretreatment of samples. This greatly simplifies the analytical procedure and minimises potential sources of contamination. The limit of detection (3s criteria) and limit of quantification (10 s criteria) for the determination of Hg in wet fish samples with a mass of 250 mg was found to be 0.6 ng g(-1) and 2.0 ng g(-1), respectively. Time taken for the analysis of one sample is about 3 min. The accuracy of the method was confirmed by the analysis of certified reference materials of different types and by comparative analysis of fish samples using the accepted method of cold vapour generation. Excellent correspondence to the certified values was obtained. It was found that the mercury concentration in most fish species purchased from the Tshwane fish market were below the 0.5 mg kg(-1) (500 ng g(-1)), wet weight, recommended by the FAO/WHO. It was also found that the direct thermal decomposition method for the determination of mercury is a more environmentally friendly alternative since it does not generate chemical waste.

In vitro estimation of exposure of Hong Kong residents to mercury and methylmercury via consumption of market fishes

In order to evaluate effects of exposure to mercury (tHg) and methylmercury (MeHg) of Hong Kong residents via consumption of fish, total and bioaccessible concentrations of tHg and MeHg were measured in 10 freshwater and 10 marine fishes collected from markets in Hong Kong. Concentrations of tHg and MeHg in fishes ranged from 27.2 to 311ngg(-1) (median 88.9ngg(-1)) and ND to 116ngg(-1) (median 45.0ngg(-1)), respectively. Concentrations of MeHg in marine fishes (64.4±28.5ngg(-1)) were significantly greater than those in freshwater fishes (40.3±26.0ngg(-1)). Bioaccessibility tHg and MeHg was predicted for edible flesh of twenty fishes by use of an in vitro gastrointestinal assay. Bioaccessibilities of tHg and MeHg ranged from 21.4 to 51.7% (mean 37.4%) and 19.5 to 59.2% (mean 43.7%), respectively. Based on total concentrations, diets of 36% of adults and 51% of children exceeded the reference dose (RfD, 100ngkg(-1)bodymass(bm)d(-1)) for MeHg, but when bioaccessibility was considered, consumption of local market fish would not result in an EDIbio exceeded the RfD of MeHg for Hong Kong adults. These contradictory results suggested that risk assessments based on total concentrations would overestimate exposure because not all of contaminants consumed are bioaccessible. Furthermore, 9% of children had EDIbio for MeHg that exceeded the RfD, which suggests that more attention should be paid to consumption of local fish on health and development of children in Hong Kong.

Factors influencing blood mercury levels of inhabitants living near fishing areas

Methylmercury (MeHg), a well-known neuro-toxicant, is usually emitted by industrial and other man-made activities; it is ingested with seafood and shellfish, and accumulates in the human body. The aim of this study was to compare the differences in blood levels of total mercury (T-Hg) and MeHg in residents of 4 coastal sites and 4 inland sites around Taiwan. Meanwhile, the potential question is warranted to find out the association between dietary intake and MeHg accumulation. We found that coastal residents had significantly higher mean blood T-Hg levels (mean: 16.1 μg/L, range: 0.9-184.9 μg/L) than inland residents (mean: 11.8 μg/L, range: 0.8-146.6 μg/L). The same was for blood MeHg levels: coastal residents (mean: 16.5 μg/L, range: 0.9-184.9 μg/L), inland residents (mean: 11.8 μg/L, range: 2.1-133.4 μg/L). These elevated levels were positively associated with seafood and shellfish consumption. However, the nature of their residential area may also be an important factor, because the highest T-Hg and MeHg levels were found in residents of a relatively non-industrialized area. To protect vulnerable population-especially children and pregnant women-it is important to know whether locally caught or raised and consumed fish has any source of Hg and MeHg pollution.

Fish consumption and risk of contamination by mercury---considerations on the definition of edible parts based on the case study of European sea bass

In the present study, the risk to humans by consuming European sea bass (Dicentrarchus labrax), captured at three sites along a Hg contamination gradient, was evaluated by comparing muscle and kidney total Hg (T-Hg) levels with the European regulations for marketed fish. Moreover, T-Hg and organic Hg (O-Hg) levels in muscle were compared with the Provisional Tolerable Weekly Intake (PTWI) and the Reference Dose (RfD). Although T-Hg levels in muscle were below the European value allowable for marketed fish, kidney's levels were higher than the set value, stressing the importance of redefining the concept of edible tissue and which tissues should be considered. Mercury weekly ingestion in the contaminated areas was higher than the PTWI, and O-Hg daily ingestion rates were higher than the RfD in all sampling sites. Thus, populations consuming sea bass from the contaminated sites may be at risk, with particular relevance for children and pregnant women.

Mercury organotropism in feral European sea bass (Dicentrarchus labrax)

The knowledge of mercury (Hg) burdens in a wide set of tissues and organs of exposed fish is crucial to understand the internal distribution dynamics and thus predict Hg bioavailability and implications for ecosystem and human health. Total Hg was measured in six tissues of Dicentrarchus labrax captured along an estuarine contamination gradient, revealing the following pattern: liver > kidney > muscle > brain ≈ gills > blood. All of the tissues displayed intersite differences, although brain and muscle seemed to better reflect the extent of contamination. Hg speciation showed that liver presented higher concentrations than muscle for both organic and inorganic forms. Furthermore, liver seemed to exert a protective action in relation to Hg accumulation in the other tissues and organs. This protection seems to be particularly marked in relation to the brain, whereas liver is assisted in that action by kidney and muscle.

Determination of dietary intake of total arsenic, inorganic arsenic and total mercury in the Chilean school meal program

The dietary intake of total arsenic (tAs), inorganic arsenic (iAs) and total mercury (tHg) in lunch and breakfast servings provided by the Chilean School Meal Program (SMP) was estimated, using the duplicate-portion variant of the total diet study. Lunch and breakfast samples were collected from 65 schools throughout the country in 2006. The population sample was a group of girls and boys between 6 and 18 years old. The tAs concentration was measured via hydride-generation atomic absorption spectrometry. The total mercury concentration was measured via cold-vapor atomic absorption spectroscopy. The estimated iAs intake was 12.5% (5.4 μg/day) of the Provisional tolerable daily intake (PTDI) as proposed by the FAO/WHO, and the tHg intake was 13.2% (1.9 μg/day) of the PTDI as proposed by the FAO/WHO. It was therefore concluded that tAs, iAs and tHg intake from food provided by the SMP do not pose risks to student health.

Hair mercury concentration and fish consumption: risk and perceptions of risk among women of childbearing age

The purposes of this study were to assess the hair mercury concentration of women of childbearing age in Taiwan, and to calculate a hazard quotient (HQ) to evaluate the risk of fish consumption for these women. We also examined perceptions of risk associated with fish consumption and whether women in our study changed their habits in response to such risks. The average concentration of mercury was 1.73+/-2.12microgg(-1) (range: 0.02-16.34microgg(-1)), exceeding the US EPA reference dose of 1microgg(-1) in 52.9% of study subjects. The WHO tolerance limit of 10microgg(-1) was exceeded in 1.5% of study subjects. Hair mercury concentration in groups who consumed fish was significantly higher than in groups who never consumed fish (p<0.05). The hazard quotient (exposure estimate/oral reference dose) exceeded 1.0 for 29% of subjects, based on the US EPA's reference dose (0.1microgkg(-1)d(-1)), and the average HQ equaled 1.26. When told that some fish contain high levels of mercury that may be harmful for unborn babies, 67.6% of women still indicated that they would not change their amount of fish intake. The high hair mercury concentrations among women of childbearing age in Taiwan are a cause for concern, due to the effect on babies' brain development. The government should provide specific information about risks and benefits of fish consumption for women to make risk-balancing decisions.

Mercury concentration in meconium and risk assessment of fish consumption among pregnant women in Taiwan

Meconium is a matrix that can be obtained easily and noninvasively and is useful for detecting antenatal fetal exposure to environmental toxins. Taiwan is an island with high fish consumption, and many pregnant women would like to enjoy the benefits of fish without jeopardizing their health or that of their child. The aim of this study is to assess the mercury concentration in meconium in relation to the health risk of mercury exposure. A total of 198 mother-infant pairs residing in the city of HsinChu were recruited for the study between January 2007 and June 2007. The average mean concentration of mercury in meconium was 79.2+/-7.3 ng g(-1) dry wt We use the Monte Carlo technique to assess the uncertainty in risk assessment and the impact of these uncertainties on the estimation of expected risk of mercury intake from fish in mothers. Based on the FAO/WHO's tolerable daily intake of methylmercury (0.23 microg kg(-1)d(-1)), we found that 17.3% and 14.0% of the daily mercury exposure estimated exceeded the reference dose for foreign-born and Taiwan-born mothers, respectively. We found that the mercury concentration in meconium was much higher than in other studies, except for one study done in Tagum in the Philippines where mercury is used in gold mining. This may be because Asia is the largest emitter of anthropogenic mercury, accounting for 53% of worldwide emissions. Sensitivity analysis suggests that mercury concentration in fish and the rate of ingesting fish may be the key parameters for governments offering risk management guidance to protect the health of mothers and unborn babies.