Relationship between Blood Mercury Level and Risk of Cardiovascular Diseases: Results from the Fourth Korea National Health and Nutrition Examination Survey (KNHANES IV) 2008-2009

Cerebrovascular accidents association between serum trace elements and toxic metals level, a case-control study

BACKGROUND

Cerebrovascular accidents (CVAs) are among the most common complications of patients today. As the prevalence of ischemic CVAs rises, detecting related risk factors is crucial. Metal concentration has previously been considered a major risk factor in several neural complications, and in this study, we will investigate this.

METHODS

In this case-control study, 70 CVA (clinically approved ischemic stroke cases by imaging and NIH Stroke Scale (NIHSS)) and 70 individuals with no history of CVA controls were enrolled as the control group. The serum level of several metals, including Fe (Iron), Co (Cobalt), Ni (Nickel), Cu (copper), Zn (Zinc), Mn (Manganese), Pb (lead), Hg (Mercury), has been assessed using Inductively coupled plasma mass spectrometry (ICP-MS) method. Logistic regression (LR) has also been used to determine the association between metals' levels and CVA occurrence.

RESULTS

As the mean age of the CVA group was 48.68  ±  15.25 years and for the non-CVA group was 47.89 ± 9.65 years, the result indicated that the serum level of Cu and Pb has been statically higher in the CVA group (respectively; P  <  0.001 and P  =  0.002) and Ni level was significantly lower (P  =  0.003). Other measured metals' levels (Fe, Co, Ni, Mn, Hg) were not significantly different between CVA and non-CVA groups. In the LR model, all Cu, Pb, and Zn metals had a P value of 0.03 and an odd ratio (OR) and confidence interval (CI) of 1.34 (1.02-1.75), 1.19 (1.01-1.39) and 1.01 (1.001-1.02) respectively.

CONCLUSION

Given that some metals are associated with a higher risk of CVA, researchers and physicians must better understand the risk factors and causes of the burden of CVA. However, further studies with a larger population and investigation of the exact pathogenesis of these metals are needed.

Cerebrovascular accident and essential and toxic metals: cluster analysis and principal component analysis

BACKGROUND

Cerebrovascular accidents are known as a great cause of morbidity and mortality worldwide. Although there are known risk factors for ischemic stroke, the cases that cannot be justified with these risk factors are increasing. Toxic metals as a potential risk factor for other diseases in humans are assessed in this study in the CVA group and compared to controls.

METHOD

70 participants (35 each group) have been selected for this study. The group with recent medical history of documented CVA and a control non-CVA group. The serum level of several metals has been assessed using Inductively coupled plasma mass spectrometry (ICP-MS) method. principal components and cluster analyses were employed to compare toxic metal toxicity between the groups.

RESULTS

Cu (p < 0.001) and Pb (p = 0.002) levels were significantly higher in the CVA group whereas Ni (0.003) were significantly lower. There was no significant difference between the smoking (p = 0.56) and opium (p = 0.46) use between these groups. Most of the essential metals were positively correlated with each other in both groups (Ni with Fe, Zn; Fe with Zn with r over 0.6). there was also PCA and CA are crucial in and cluster analysis in which Ni, Fe, and Zn were most similarly correlated in both groups.

CONCLUSION

we found a complex interaction between toxic metals in the healthy and CVA human body. Due to the lack of data on in vivo interaction of these metals even in healthy individuals, further investigation is needed to evaluate the exact mechanism of such relations.

Association between blood total mercury and psoriasis: The NHANES 2005-2006 and 2013-2014: A cross-sectional study

An inflammatory skin condition called psoriasis results from immune system interactions that are out of balance. Reactive oxygen species are produced as a general mechanism of mercury toxicity. This study aimed to determine whether there was an association between blood total mercury and psoriasis in US adults. Utilizing data from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 and 2013-2014. NHANES is a national research survey program every two years to assess the population's nutritional and physical health. The relationship between blood total mercury and psoriasis was studied using multivariable logistic regression models and smooth curve fitting. Subgroup analysis and interaction tests were used to investigate if this association was stable across populations. After adjusting for several factors, we found a positive association between blood total mercury and psoriasis in 6086 participants. According to the fully adjusted model, each 1-unit increase in blood total mercury was associated with an 8% increase in the prevalence of psoriasis [1.08 (1.03, 1.14)]. The favorable association seems to be more pronounced in non-diabetes. Our research shows a positive association between psoriasis and blood total mercury in US adults. The results of this study need to be supported by additional prospective research.

Systematic Review and Meta-analysis of Environmental Toxic Metal Contaminants and the Risk of Ischemic Stroke

Background

Stroke is the second largest cause of mortality (WHO 2014) and long-lasting disability worldwide. Many risk factors are associated with stroke, such as age, gender, chronic illnesses, cardiovascular disease, lifestyle, and smoking. With global industrialization, the roles of environmental contaminants and their association with stroke are still unclear and have attracted much more attention.

Materials and Methods

We conducted a systematic review on the environmental toxic metal contaminants and the risk of ischemic stroke. A comprehensive literature search was carried out till June 30, 2021 from databases such as PubMed, Science Direct, Embase, and Scopus. The quality of all the articles which met our inclusion criteria was assessed using Newcastle-Ottawa scaling, and four eligible studies were included for our systematic review.

Results

The serum and urine cadmium concentrations were positively associated with the risk of ischemic stroke. There was an inverse association of serum and urine concentrations of mercury (Hg), serum concentration of gold and cerium with ischemic stroke, and the serum and urine concentrations of lead (Pb) had no association with ischemic stroke risk.

Conclusion

The study showed strong associations between heavy metals and ischemic stroke, but more studies are required to prove the associations.

Hair methylmercury levels are inversely correlated with arterial stiffness

BACKGROUND AND AIMS

Cardiovascular diseases (CVD), including coronary heart disease, are the leading cause of death worldwide. Several studies investigating the relationship between fish intake, methylmercury exposure, and CVDs in adults have reported inconsistent results. This study aimed to determine the association between hair methylmercury levels and arterial stiffness using brachial-ankle pulse wave velocity (baPWV).

METHODS

This cross-sectional study included 891 seemingly healthy Korean adults (418 men and 473 women). The anthropometric and biochemical profiles, including methylmercury levels in the hair, were measured. Arterial stiffness was measured using baPWV, wherein high baPWV was defined as >1375 cm/s (>75th percentile). The odds ratios for high baPWVs were examined using multivariable logistic regression analysis after adjusting for potential confounders across the quintiles of hair methylmercury levels (Q1 = ≤0.6, Q2 = 0.6-0.8, Q3 = 0.8-1.1, Q4 = 1.1-1.5, and Q5=>1.5 μg/g).

RESULTS

After adjusting for multiple confounders-age, sex, height, body weight, smoking status, weekly alcohol consumption, total metabolic equivalent of task, mean arterial blood pressure, resting heart rate, triglycerides, low density lipoprotein cholesterol, fasting plasma glucose, uric acid and white blood cell count-the odds ratios (95% confidence intervals) for high baPWVs in each quintile of hair methylmercury levels were 1.00, 0.36 (0.17-0.76), 0.38 (0.20-0.76), 0.28 (0.13-0.61), and 0.49 (0.24-0.99), respectively.

CONCLUSIONS

Within non-toxic low levels, higher hair methylmercury levels are independently associated with lower arterial stiffness in seemingly healthy Korean adults regardless of classical cardiovascular risk factors.

The Effect of Mixture of Heavy Metals on Obesity in Individuals ≥50 Years of Age

Little is known about the association between a mixture of heavy metals and obesity among individuals ≥50 years of age with comorbidities. Thus, we identified the associations of serum cadmium (Cd), lead (Pb), and mercury (Hg) with obesity using linear regression models; weighted quantile sum (WQS) regression, quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR) were conducted as secondary analyses. Of the 6434 subjects included in the analysis, 13.8% had obesity and 44.6% had abdominal obesity. In the logistic regression model, serum Hg was associated with obesity and abdominal obesity, and significant trends were observed for these heavy metal tertiles (p < 0.001). Serum Hg levels were also associated with body mass index (BMI) and waist circumference (WC). The WQS index was significantly associated with both obesity (OR = 1.43, 95% CI: 1.40-1.46) and abdominal obesity (β = 1.51, 95% CI: 1.48-1.54). The qgcomp index also found a significant association between heavy metals and both obesity (OR = 1.35, 95% CI: 1.12-1.63) and abdominal obesity (OR = 1.34, 95% CI: 1.12-1.60). Serum Hg was the most heavily weighed heavy metal in these models. In BKMR analysis, the overall effect of the mixture was significantly associated with obesity, BMI, and WC. Serum Hg showed positive trends and was observed as the most important factor associated with obesity, BMI, and WC. Our findings were largely robust to secondary analyses that used three novel mixture modeling approaches: WQS, qpcomp, and BKMR. Given increasing exposure to heavy metals, well-characterized cohorts of individuals aged ≥50 years are required to determine the mixed effects of heavy metals on obesity and related diseases.

Methyl mercury triggers endothelial leukocyte adhesion and increases expression of cell adhesion molecules and chemokines

Cardiovascular disease is the leading cause of morbidity, mortality, and health care costs in the USA, and around the world. Among the various risk factors of cardiovascular disease, environmental and dietary exposures to methyl mercury, a highly toxic metal traditionally labeled as a neurotoxin, have been epidemiologically linked to human cardiovascular disease development. However, its role in development and promotion of atherosclerosis, an initial step in more immediately life-threatening cardiovascular diseases, remains unclear. This study was conducted to examine the role that methyl mercury plays in the adhesion of monocytes to human microvascular endothelial cells (HMEC-1), and the underlying mechanisms. Methyl mercury treatment significantly induced the adhesion of monocyte to HMEC-1 endothelial cells, a critical step in atherosclerosis, while also upregulating the expression of proinflammatory cytokines interleukin-6, interleukin-8. Further, methyl mercury treatment also upregulated the chemotactic cytokine monocyte chemoattractant protein-1 and intercellular adhesion molecule-1. These molecules are imperative for the firm adhesion of leukocytes to endothelial cells. Additionally, our results further demonstrated that methyl mercury stimulated a significant increase in NF-κB activation. These findings suggest that NF-κB signaling pathway activation by methyl mercury is an important factor in the binding of monocytes to endothelial cells. Finally, by using flow cytometric analysis, methyl mercury treatment caused a significant increase in necrotic cell death only at higher concentrations without initiating apoptosis. This study provides new insights into the molecular actions of methyl mercury that can lead to endothelial dysfunction, inflammation, and subsequent atherosclerotic development.

Human mercury exposure levels and fish consumption at the French Riviera

Humans are exposed to methylmercury (MeHg), a bioaccumulative neurotoxin, mainly through the consumption of marine fish. Several studies showed that high MeHg exposure can lead to neurological damage. This is particularly relevant for pregnant women, because MeHg exposure negatively impacts foetal development. Populations living near the sea are generally at increased exposure risk due to higher consumption of fish and seafood. Here, we present the first study of MeHg exposure levels of the population living at the French Riviera, using mercury (Hg) concentrations in hair as a proxy for MeHg exposure. We found that older people that consume more fish presented the highest hair Hg concentrations. Compared to other Mediterranean bordering countries and other European countries, the southern France population is among those with high MeHg exposure (median for women of childbearing age is 0.56 μg g^-1). A global implementation of the Minamata Convention is necessary to lower MeHg exposure of the population.

Association between heavy metal levels and acute ischemic stroke

Background

Few studies have examined the relationship between the amounts of heavy metal and stroke incidence. The aim of this study was to explore the relationship between levels of heavy metals, including Pb, Hg, As, and Cd, in patients with acute ischemic stroke (AIS).

Methods

We selected patients with first-ever AIS onset within 1 week as our study group. Healthy controls were participants without a history of stroke or chronic disease, except hypertension. The serum levels of Pb, Hg, As, and Cd in participants in the experimental and control groups were determined. All participants received a 1-g infusion of edetate calcium disodium (EDTA). Urine specimens were collected for 24 h after EDTA infusion and measured for heavy metal levels.

Results

In total, 33 patients with AIS and 39 healthy controls were enrolled in this study. The major findings were as follows: (1) The stroke group had a significantly lower level of serum Hg (6.4 ± 4.3 μg/L vs. 9.8 ± 7.0 μg/L, P = 0.032, OR = 0.90, 95% CI = 0.81–0.99) and a lower level of urine Hg (0.7 ± 0.7 μg/L vs. 1.2 ± 0.6 μg/L, P = 0.006, OR = 0.27, 95% CI = 0.11–0.68) than the control group. (2) No significant difference in serum Pb (S-Pb), As (S-As), and Cd (S-Cd) levels and urine Pb (U-Pb), As (U-As) and Cd (U-Cd) levels was observed in either group.

Conclusions

Our study found low levels of serum and urine Hg in first-ever patients with AIS, providing new evidence of dysregulated heavy metals in patients with AIS.

Electronic supplementary material

The online version of this article (10.1186/s12929-018-0446-0) contains supplementary material, which is available to authorized users.

Fish consumption, mercury exposure, and the risk of cholesterol profiles: findings from the Korea National Health and Nutrition Examination Survey 2010-2011

In this study, the associations between mercury (Hg) exposure and cholesterol profiles were analyzed, and increased Hg levels and cholesterol profiles according to the amount of fish consumption were evaluated. Data on levels of blood Hg, the frequency of fish consumption, total blood cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) in 3951 adults were obtained from the Korea National Health and Nutrition Examination Survey 2010-2011 database. To compare the distribution for each log-transformed indicator, Student's t-test and analysis of variance were carried out, and the groups were classified according to the frequency of fish consumption through linear regression analysis; the association between Hg level and cholesterol profiles in each group was analyzed. The blood Hg levels (arithmetic mean, median, and geometric mean) for all target participants were 4.59, 3.66, and 3.74 µg/L, respectively. The high cholesterol group, low HDL-C group, and high TG group showed a statistically and significantly higher blood Hg level than the low-risk group. In both sexes, as the frequency of fish consumption increased, blood Hg level also increased, but TC, HDL-C, LDL-C, and TG did not show a similar trend. Increased blood Hg level showed a significant association with increased TC and LDL-C. This statistical significance was maintained in the group with less frequent fish consumption (<4 times per month), but the group with frequent fish consumption (>8 times per month) did not show a similar trend. The results of this study suggest that fish consumption increases the level of Hg exposure, and that as the level of Hg exposure increases, the levels of cholesterol profiles increase. However, this study also suggests that the levels of cholesterol profiles in those with frequent fish consumption can be diminished.

Association between Blood Mercury Level and Visceral Adiposity in Adults

BACKGROUND

Few studies have examined the association between mercury exposure and obesity. The aim of this study is to investigate the association between blood mercury concentrations and indices of obesity in adults.

METHODS

A total of 200 healthy subjects, aged 30 to 64 years, who had no history of cardiovascular or malignant disease, were examined. Anthropometric and various biochemical profiles were measured. Visceral adipose tissue (VAT) was measured using dual-energy X-ray absorptiometry (DXA).

RESULTS

All subjects were divided into three groups according to blood mercury concentrations. Compared with the subjects in the lowest tertile of mercury, those in the highest tertile were more likely to be male; were current alcohol drinkers and smokers; had a higher body mass index (BMI), waist circumference (WC), and VAT; had higher levels of blood pressure, fasting glucose, and insulin resistance; and consumed more fish. The blood mercury concentration was significantly associated with anthropometric parameters, showing relationships with BMI, WC, and VAT. After adjusting for multiple risk factors, the odds ratios (ORs) for high mercury concentration was significantly higher in the highest VAT tertile than in the lowest VAT tertile (OR, 2.66; 95% confidence interval, 1.05 to 6.62; P<0.05).

CONCLUSION

The blood mercury concentration was significantly associated with VAT in healthy adults. Further studies are warranted to confirm our findings.

Lean Fish Consumption Is Associated with Beneficial Changes in the Metabolic Syndrome Components: A 13-Year Follow-Up Study from the Norwegian Tromsø Study

BACKGROUND

Fish consumption may have beneficial effects on metabolic syndrome (MetS); however, limited information of such associations exists. This study investigated possible associations between fish consumption and changes in MetS components during a 13-year follow-up period.

METHODS

The sample included participants (26-69 years) from the Tromsø Study 4 (1994-1995, n = 23,907) and Tromsø Study 6 (2007-2008, n = 12,981). Data were collected using questionnaires including food frequency questions, non-fasting blood samples, and physical examinations. MetS was defined using the Joint Interim Societies (JIS) definition, in which one point was given for each MetS criteria fulfilled (metabolic score). Longitudinal analyses were performed using Linear mixed models.

RESULTS

For both genders, lean fish consumption once a week or more was significantly associated with decreased future metabolic score, decreased triglycerides, and increased high-density lipoprotein (HDL)-cholesterol, whereas decreased waist circumference and blood pressure was identified only for men (age adjusted models). Fatty fish consumption was significantly associated with increased waist circumference for both genders and increased HDL-cholesterol levels in men. Conclusion: The results suggest that fatty and lean fish consumption may influence MetS differently and that lean fish consumption in particular seems to be associated with beneficial changes in the MetS components.

Mercury exposure and risk of cardiovascular disease: a nested case-control study in the PREDIMED (PREvention with MEDiterranean Diet) study

BACKGROUND

Substantial evidence suggests that consuming 1-2 servings of fish per week, particularly oily fish (e.g., salmon, herring, sardines) is beneficial for cardiovascular health due to its high n-3 polyunsaturated fatty acid content. However, there is some concern that the mercury content in fish may increase cardiovascular disease risk, but this relationship remains unclear.

METHODS

The PREDIMED trial included 7477 participants who were at high risk for cardiovascular disease at baseline. In this study, we evaluated associations between mercury exposure, fish consumption and cardiovascular disease. We randomly selected 147 of the 288 cases diagnosed with cardiovascular disease during follow-up and matched them on age and sex to 267 controls. Instrumental neutron activation analysis was used to assess toenail mercury concentration. In-person interviews, medical record reviews and validated questionnaires were used to assess fish consumption and other covariates. Information was collected at baseline and updated yearly during follow-up. We used conditional logistic regression to evaluate associations in the total nested case-control study, and unconditional logistic regression for population subsets.

RESULTS

Mean (±SD) toenail mercury concentrations (μg per gram) did not significantly differ between cases (0.63 (±0.53)) and controls (0.67 (±0.49)). Mercury concentration was not associated with cardiovascular disease in any analysis, and neither was fish consumption or n-3 fatty acids. The fully-adjusted relative risks for the highest versus lowest quartile of mercury concentration were 0.71 (95% Confidence Interval [CI], 0.34, 1.14; p_trend = 0.37) for the nested case-control study, 0.74 (95% CI, 0.32, 1.76; p_trend = 0.43) within the Mediterranean diet intervention group, and 0.50 (95% CI, 0.13, 1.96; p_trend = 0.41) within the control arm of the trial. Associations remained null when mercury was jointly assessed with fish consumption at baseline and during follow-up. Results were similar in different sensitivity analyses.

CONCLUSIONS

We found no evidence that mercury exposure from regular fish consumption increases cardiovascular disease risk in a population of Spanish adults with high cardiovascular disease risk and high fish consumption. This implies that the mercury content in fish does not detract from the already established cardiovascular benefits of fish consumption.

TRIAL REGISTRATION

ISRCTN35739639 .

An analysis of factors affecting the mercury content in the human femoral bone

The study was carried out to determine the content of mercury in bone tissue of the proximal femur (head and neck bone) of 95 patients undergoing total hip replacement due to osteoarthritis, using CF-AFS analytical technique. Furthermore, the investigations were aimed at assessing the impact of selected factors, such as age, gender, tobacco smoking, alcohol consumption, exposure to chemical substance at work, type of degenerative changes, clinical evaluation and radiological parameters, type of medications, on the concentration of mercury in the head and neck of the femur, resected in situ. Mercury was obtained in all samples of the head and neck of the femur (n = 190) in patients aged 25-91 years. The mean content of mercury for the whole group of patients was as follows: 37.1 ± 35.0 ng/g for the femoral neck and 24.2 ± 19.5 ng/g for the femoral head. The highest Hg contents were found in femoral neck samples, both in women and men, and they amounted to 169.6 and 176.5 ng/g, respectively. The research showed that the mercury content of bones can be associated with body mass index, differences in body anatomy, and gender. The uses of statistical analysis gave the possibility to define the influence of factors on mercury content in human femoral bones.

Chemical Speciation of Selenium and Mercury as Determinant of Their Neurotoxicity

The antagonism of mercury toxicity by selenium has been well documented. Mercury is a toxic metal, widespread in the environment. The main target organs (kidneys, lungs, or brain) of mercury vary depending on its chemical forms (inorganic or organic). Selenium is a semimetal essential to mammalian life as part of the amino acid selenocysteine, which is required to the synthesis of the selenoproteins. This chapter has the aim of disclosing the role of selenide or hydrogen selenide (Se^-2 or HSe^-) as central metabolite of selenium and as an important antidote of the electrophilic mercury forms (particularly, Hg²⁺ and MeHg). Emphasis will be centered on the neurotoxicity of electrophile forms of mercury and selenium. The controversial participation of electrophile mercury and selenium forms in the development of some neurodegenerative disease will be briefly presented. The potential pharmacological use of organoseleno compounds (Ebselen and diphenyl diselenide) in the treatment of mercury poisoning will be considered. The central role of thiol (-SH) and selenol (-SeH) groups as the generic targets of electrophile mercury forms and the need of new in silico tools to guide the future biological researches will be commented.

Screening of Blood Levels of Mercury, Cadmium, and Copper in Pregnant Women in Dakahlia, Egypt: New Attention to an Old Problem

Heavy metals toxicity is a prevalent health problem particularly in developing countries. Mercury and cadmium are toxic elements that have no physiologic functions in human body. They should not be present in the human body by any concentration. Copper, on the other hand, is one of the elements that are essential for normal cell functions and a deficiency as well as an excess of which can cause adverse health effects. To test blood levels of mercury, cadmium, and copper in pregnant women in Dakahlia, Egypt. Using atomic absorption spectrophotometry, blood levels of cadmium, mercury, and copper were measured in 150 pregnant women attending to the antenatal care in Mansoura University Hospital in Dakahlia governorate, Egypt. The mean ± SD of blood mercury, cadmium, and copper levels were found to be far from their levels in the population surveys carried in developed countries like United States of America (USA) and Canada. Heavy metal intoxication and accumulation is a major health hazard. Developing countries, including Egypt, still lack many of the regulatory policies and legislations to control sources of pollution exposure. This should be dealt with in order to solve this problem and limit its health consequences.

The Association Between Blood Mercury Levels and Risk for Overweight in a General Adult Population: Results from the Korean National Health and Nutrition Examination Survey

The primary objective of this study was to estimate the association between blood mercury levels and overweight in Korean adults. We analyzed cross-sectional data from 9228 participants (4283 men and 4945 women) who completed the Korean National Health and Nutrition Examination Survey (KNHANES), 2007-2013. The population was divided into two groups according to the body mass index (BMI) and waist circumference (WC). Blood mercury levels were analyzed using a gold amalgam method with a DMA-80 instrument, categorized into quartiles, and stratified by sex. After adjusting for all covariates, blood mercury was significantly associated with overweight in all subjects. According to the BMI criteria, the adjusted odds ratio of being in the highest blood mercury quartile was 1.75 (95 % confidence interval [CI], 1.53-2.01) overall, 2.09 (95 % CI, 1.71-2.55) in men, and 1.58 (95 % CI, 1.32-1.89) in women. According to the WC criteria, the adjusted odds ratio of being in the highest blood mercury quartile was 1.85 (95 % CI, 1.49-2.30) in men and 1.96 (95 % CI, 1.62-2.36) in women compared to the lowest quartile. Additionally, a trend in overweight across increasing blood mercury levels was observed by the p for trend test in the multiple diagnostic criteria.

Associations of serum n-3 and n-6 PUFA and hair mercury with the risk of incident stroke in men: the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD)

PUFA have been associated with lower risk of CVD, but less is known about their association with stroke risk. Fish, a major source of n-3 PUFA, may also contain methylmercury, which has been associated with higher risk of CVD and attenuation of the benefits of long-chain n-3 PUFA. We investigated the associations of serum n-3 and n-6 PUFA and hair Hg with risk of stroke in men. A total of 1828 men from the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42-60 years and free of CVD at baseline in 1984-1989 were studied. Cox regression models were used for the analyses. During the mean follow-up of 21·2 years, 202 stroke cases occurred, of which 153 were ischaemic strokes. After adjustment for age and examination year, the only statistically significant association among the n-3 and n-6 PUFA was observed between the n-3 PUFA α-linolenic acid and risk of haemorrhagic stroke (hazard ratio in the highest v. the lowest quartile 0·33; 95 % CI 0·13, 0·86; P trend=0·03). However, further adjustments attenuated the association to statistically non-significant. Hair Hg was not associated with stroke risk, but among those with hair Hg above the median level, higher serum long-chain n-3 PUFA concentrations were associated with a higher risk of ischaemic stroke. In our cohort of men, serum n-3 or n-6 PUFA or hair Hg were not associated with stroke risk; however, the interaction between Hg and long-chain n-3 PUFA with regard to ischaemic stroke risk warrants further investigation.

Cerebrovascular endothelial dysfunction induced by mercury exposure at low concentrations

Mercury (Hg) has many harmful vascular effects by increasing oxidative stress, inflammation and vascular/endothelial dysfunction, all of which may contribute to cerebrovascular diseases development. We aimed to explore the effects of chronic low-mercury concentration on vascular function in cerebral arteries and the mechanisms involved. Basilar arteries from control (vehicle-saline solution, im) and mercury chloride (HgCl2)-treated rats for 30 days (first dose 4.6μg/kg, subsequent dose 0.07μg/kg/day, im, to cover daily loss) were used. Vascular reactivity, protein expression, nitric oxide (NO) levels and superoxide anion (O2(-)) production were analyzed. HgCl2 exposure increased serotonin contraction and reduced the endothelium-dependent vasodilatation to bradykinin. After NO synthase inhibition, serotonin responses were enhanced more in control than in mercury-treated rats while bradykinin-induced relaxation was abolished. NO levels were greater in control than Hg-treated rats. Tiron and indomethacin reduced vasoconstriction and increased the bradykinin-induced relaxation only in HgCl2-treated rats. Vascular O2(-) production was greater in mercury-treated when compared to control rats. Protein expressions of endothelial NO synthase, copper/zinc (Cu/Zn), Manganese (Mn) and extracellular-superoxide dismutases were similar in cerebral arteries from both groups. Results suggest that Hg treatment increases cerebrovascular reactivity by reducing endothelial negative modulation and NO bioavailability; this effect seems to be dependent on increased reactive oxygen species and prostanoids generation. These findings show, for the first time, that brain vasculature are also affected by chronic mercury exposure and offer further evidence that even at small concentration, HgCl2 is hazardous and might be an environmental risk factor accounting for cerebral vasospasm development.

Mercury, selenium and fish oils in marine food webs and implications for human health

Humans who eat fish are exposed to mixtures of healthful nutrients and harmful contaminants that are influenced by environmental and ecological factors. Marine fisheries are composed of a multitude of species with varying life histories, and harvested in oceans, coastal waters and estuaries where environmental and ecological conditions determine fish exposure to both nutrients and contaminants. Many of these nutrients and contaminants are thought to influence similar health outcomes (i.e., neurological, cardiovascular, immunological systems). Therefore, our understanding of the risks and benefits of consuming seafood require balanced assessments of contaminants and nutrients found in fish and shellfish. In this paper, we review some of the reported benefits of fish consumption with a focus on the potential hazards of mercury exposure, and compare the environmental variability of fish oils, selenium and mercury in fish. A major scientific gap identified is that fish tissue concentrations are rarely measured for both contaminants and nutrients across a range of species and geographic regions. Interpreting the implications of seafood for human health will require a better understanding of these multiple exposures, particularly as environmental conditions in the oceans change.