The evolution of symptoms of nervous system dysfunction in a First Nation community with a history of mercury exposure: a longitudinal study.

BACKGROUND: Since the 1960's, mercury (Hg) contamination of the aquatic environment of Asubpeeschoseewagong Anishinabek (Grassy Narrows First Nation) territories has impacted the community members' traditions, culture, livelihood, diet and health. Despite decreasing Hg exposure over time, a recent study suggested that long-term exposure contributed to later-life symptom clusters of nervous system dysfunction. Here, the objective was to evaluate, 5 years later, the prevalence and progression of these symptoms and examine the contribution of long-term, past Hg exposure. METHODS: The symptom questionnaire, applied in the 2016/17 Grassy Narrows Community Health Assessment (GN-CHA) (Time 1), was re-administered in the 2021/22 Niibin study (Time 2). A total of 85 adults (median age: 47y; range: 29-75y) responded at both times. Paired statistics were used to test the differences (Time 2 - Time 1) in self-reported symptom frequencies. The symptom clustering algorithm, derived from the entire study group of the GN-CHA (n = 391), which had yielded 6 clusters, was applied at Time 1 and 2. Equivalent hair Hg measurements (HHg) between 1970 and 1997 were used in Longitudinal Mixed Effects Models (LMEM), with a sub-group with ≥ 10 repeated HHg mesurements (age > 40y), to examine its associations with symptom cluster scores and their progression. RESULTS: For most symptoms, paired analyses (Time 2 - Time 1) showed a significant increase in persons reporting " very often" or "all the time", and in the mean Likert scores for younger and older participants (< and ≥ 50y). The increase in cluster scores was not associated with age or sex, except for sensory impairment where a greater increase in symptom frequency was observed for younger persons. LMEM showed that, for the sub-group, long-term past Hg exposure was associated with most cluster scores at both times, and importantly, for all clusters, with their rate of increase over time (Time 2 - Time 1). CONCLUSIONS: The persistence of reported symptoms and their increase in frequency over the short 5-year period underline the need for adequate health care services. Results of the sub-group of persons > 40y, whose HHg reflects exposure over the 28-year sampling period, suggest that there may be a progressive impact of Hg on nervous system dysfunction.

The Contribution across Three Generations of Mercury Exposure to Attempted Suicide among Children and Youth in Grassy Narrows First Nation, Canada: An Intergenerational Analysis.

BACKGROUND: For 60 y, the people of Asubpeeschoseewagong Anishinabek (Grassy Narrows First Nation) have endured the effects of massive mercury (Hg) contamination of their river system, central to their traditions, culture, livelihood, and diet. In the years following the Hg discharge into the English-Wabigoon River system by a chloralkali plant in the early 1970s, there was a dramatic increase in youth suicides. Several authors attributed this increase solely to social disruption caused by the disaster. OBJECTIVE: This research examined the possible contribution of Hg exposure across three generations on attempted suicides among today's children (5-11 y old) and youth (12-17 y old), using a matrilineal intergenerational paradigm. METHODS: Information from the 2016-2017 Grassy Narrows Community Health Assessment (GN-CHA) survey was merged with Hg biomonitoring data from government surveillance programs (1970-1997). Data from 162 children/youth (5-17 years of age), whose mothers (n=80) had provided information on themselves, their parents, and children, were retained for analyses. Direct and indirect indicators of Hg exposure included a) grandfather had worked as a fishing guide, and b) mother's measured and estimated umbilical cord blood and childhood hair Hg and her fish consumption during pregnancy with this child. Structural equation modeling (SEM) was used to examine significant links from grandparents (G0) to mothers' exposure and mental health (G1) and children/youth (G2) risk for attempted suicide. RESULTS: Mothers' (G1) median age was 33 y, 86.3% of grandmothers (G0) had lived in Grassy Narrows territory during their pregnancy, and 52.5% of grandfathers (G0) had worked as fishing guides. Sixty percent of children (G2) were <12 years of age. Mothers reported that among teenagers (G2: 12-17 years of age), 41.2% of girls and 10.7% of boys had ever attempted suicide. The SEM suggested two pathways that significantly linked grandparents (G0) to children's (G2) attempted suicides: a) through mothers' (G1) prenatal and childhood Hg exposure and psychological distress, and b) through maternal fish consumption during pregnancy (G1/G2), which is an important contributor to children's emotional state and behavior. DISCUSSION: Despite minimal individual information on G0 and G1 past life experiences, the findings support the hypothesis that Hg exposure over three generations contributes to the mental health of today's children and youth. The prevalence of Grassy Narrows youth ever having attempted suicide is three times that of other First Nations in Canada. https://doi.org/10.1289/EHP11301.

Visual Characteristics of Adults with Long-Standing History of Dietary Exposure to Mercury in Grassy Narrows First Nation, Canada.

Since the 1960s, Grassy Narrows First Nation (Ontario, Canada) has been exposed to methyl mercury (Hg) through fish consumption, resulting from industrial pollution of their territorial waters. This cross-sectional study describes the visual characteristics of adults with documented Hg exposure between 1970 and 1997. Oculo-visual examinations of 80 community members included visual acuity, automated visual fields, optical coherence tomography [OCT], color vision and contrast sensitivity. Median age was 57 years (IQR 51-63) and 55% of participants were women. Median visual acuity was 0.1 logMAR (Snellen 6/6.4; IQR 0-0.2). A total of 26% of participants presented a Visual Field Index inferior to 62%, and qualitative losses assessment showed concentric constriction (18%), end-stage concentric loss (18%), and complex defects (24%). On OCT, retinal nerve fiber layer scans showed 74% of participants within normal/green range. For color testing with the Hardy, Rand, and Rittler test, 40% presented at least one type of color defect, and with the Lanthony D-15 test, median color confusion index was 1.59 (IQR 1.33-1.96). Contrast sensitivity showed moderate loss for 83% of participants. These findings demonstrate important loss of visual field, color vision, and contrast sensitivity in older adults in a context of long-term exposure to Hg in Grassy Narrows First Nation.

How to carry out participatory research that takes account of sex and gender issues: a scoping review of guidelines targeting health inequities.

OBJECTIVE: Conducting participatory research (PR) aimed at improving health implies considering inequitable power relations, including those related to sex/gender (S/G). This necessitates specific skills and methods and may be challenging especially since guidelines are scarce. Our objective was to perform a scoping review to provide a typology of existing guidelines for researchers on how to take account of S/G in the context of PR in public health, with a focus on occupational and environmental health. METHODS: All steps of the research were conducted with the collaboration of an advisory committee, following PR principles. Nineteen documents were retained from 513 references identified in nine scientific databases and grey literature between 2000 and 2020. Data on recommendations were extracted and coded qualitatively. Cluster analysis based on similarities in recommendations proposed in the documents identified four types: (1) empowerment-centered; (2) concrete action-centered; (3) macrosystem-centered; and (4) stakeholder-centered. SYNTHESIS: Many sources gave pointers on how to include S/G during data collection and analysis or during the dissemination of findings, but there was a dearth of suggestions for building partnerships with stakeholders and producing sustainable S/G sociopolitical transformations. Occupational health PR showed less similarities with other public health subfields including environmental health PR. Power relationships with workplace stakeholders generated specific obstacles related to S/G integration that require further attention. Intersectionality and reflexive practices emerged as overarching themes. CONCLUSION: This review provides helpful guidelines to researchers at different stages of planning PR, ranging from familiarizing themselves with S/G approaches to anticipating difficulties in their ongoing S/G-transformative PR.

RéSUMé: OBJECTIF: Les recherches participatives (RP) visant l'amélioration de la santé doivent tenir compte de rapports de pouvoir inéquitables, incluant ceux liés au sexe/genre (S/G). Cela peut s'avérer difficile vu les compétences requises et la rareté de recommandations. Notre objectif consistait à réaliser une revue de portée menant à une typologie des recommandations existantes pour les chercheurs.euses sur l'intégration du S/G en contexte de RP en santé publique, particulièrement en santé environnementale ou au travail. MéTHODOLOGIE: Un comité d'encadrement a participé à chaque étape de l'étude. Nous avons retenu 19 documents parmi 513 références identifiées dans neuf bases de données scientifiques et la littérature grise (2000­2020). L'extraction et le codage qualitatif des recommandations a mené à une analyse de clusters basée sur les similitudes identifiant quatre types centrés sur : 1) pouvoir d'agir; 2) actions concrètes; 3) macro-système; et 4) parties prenantes. SYNTHèSE: Plusieurs sources indiquaient comment intégrer le S/G pendant la collecte/analyse des données ou la diffusion des résultats. Peu de recommandations touchaient l'aspect S/G au niveau des partenariats avec des parties prenantes ou des transformations sociopolitiques durables. Les recommandations en santé au travail étaient moins similaires aux autres sous-domaines de santé publique. Les relations de pouvoir en milieu de travail engendrent des obstacles spécifiques liés à l'intégration du S/G et nécessitent une attention particulière. L'intersectionnalité et les pratiques réflexives sont apparues comme des thèmes primordiaux. CONCLUSION: Les recommandations repérées aideront des chercheurs.euses à différents stades de leur parcours d'intégration du S/G dans une RP en cours, allant de la familiarisation à l'anticipation de difficultés.

Integration of sex and gender in interventions by students in ergonomics.

This article aims to analyse the integration of sex and gender (s/g) by ergonomics students during their internship at the master's degree level, following training sessions on s/g issues in the workplace. This exploratory research used a descriptive mixed-methods design, encompassing evaluation of students' intention to use the content from the training (n = 13 students), and a multiple case study (n = 5 ergonomics interventions). The results show that while students found the training relevant, they only minimally integrated s/g in their interventions and when they did, it was primarily from an anthropometric and physiological perspective. In addition to discussing the training format limitations, the article discusses barriers to this integration: combining learning about s/g issues with learning about activity analysis is challenging; employers' and workers' organisations may be reluctant to approach s/g issues; and it is difficult for an ergonomist to integrate these issues when the employer's request does not specify it.Practitioner summary: This article aims to analyse the integration of s/g by ergonomics students during their internships. Findings show that they only minimally considered s/g. The discussion examines s/g training, organisational obstacles to inclusion of s/g during interventions, and how ergonomists can consider s/g in their practice.

Past mercury exposure and current symptoms of nervous system dysfunction in adults of a First Nation community (Canada).

BACKGROUND: The watershed in Asubpeeschoseewagong Netum Anishinabek (Grassy Narrows First Nation) territory has been contaminated by mercury (Hg) since 1962, resulting in very high Hg concentrations in fish, central to the community's culture, traditions, economy and diet. Biomarkers of Hg exposure (umbilical cord blood and hair/blood samples), monitored between 1970 and 1997, decreased over time. A recent Grassy Narrows Community Health Assessment (GN-CHA) survey included current symptoms of nervous system dysfunction. The present study aimed to cluster self-reported symptoms and examine their associations with past Hg exposure. METHODS: The GN-CHA included 391 adults. Symptom clustering used a two-step segmentation approach. Umbilical cord Hg and/or yearly measurements of equivalent hair Hg were available for 242 participants. Structural Equation Models (SEM) displayed the associations between Hg exposure and clusters, with Hg exposure modelled as a latent variable or in separate variables (prenatal, childhood and having had hair Hg ≥ 5 µg/g at least once over the sampling period). Longitudinal Mixed Effects Models (LMEM) served to examine past hair Hg with respect to clusters. RESULTS: A total of 37 symptoms bonded into 6 clusters, representing Extrapyramidal impairment, Sensory impairment, Cranial nerve disturbances, Gross motor impairment, Neuro-cognitive deficits and Affect/Mood disorders. Median Hg concentrations were 5 µg/L (1-78.5) and 1.1 µg/g (0.2-16) for umbilical cord and childhood hair, respectively. More than one-third (36.6%) had hair Hg ≥ 5 µg/g at least once. In SEM, latent Hg was directly associated with Extrapyramidal and Sensory impairment, Cranial nerve disturbances and Affect/Mood disorders. Direct associations were observed for prenatal exposure with Affect/Mood disorders, for childhood exposure with Extrapyramidal impairment and Cranial nerve disturbances, and for hair Hg ≥ 5 µg/g with Extrapyramidal and Sensory impairment. For all clusters, a further association between past Hg exposure and symptom clusters was mediated by diagnosed nervous system disorders. LMEM showed higher past hair Hg among those with higher scores for all clusters, except Affect/Mood disorders. CONCLUSION: Our findings provide evidence that in this First Nation community, past Hg exposure from fish consumption was associated with later-life clusters of coexisting symptoms of nervous system dysfunction.

Mercury exposure and premature mortality in the Grassy Narrows First Nation community: a retrospective longitudinal study.

BACKGROUND: Little is known about the influence of toxic exposures on reduced life expectancy in First Nations people in Canada. The Grassy Narrows First Nation community have lived with the consequences of one of the worst environmental disasters in Canadian history. In the early 1960s, 10 000 kg of mercury (Hg) was released into their aquatic ecosystem. Although Hg concentration in fish, their dietary staple, decreased over time, it remains high. We aimed to examine whether elevated Hg exposure over time contributes to premature mortality (younger than 60 years) in this community. METHODS: We did longitudinal and case-control analyses with data for individuals of the Grassy Narrows First Nation community. In 2019, the community obtained their historical Hg biomarker data from a government surveillance programme, which was then shared with the authors. A matched-pair approach allowed us to compare longitudinal hair Hg concentration between cases (individuals who died aged younger than 60 years) and controls (individuals who lived beyond 60 years). Matching criteria included year of birth (allowing 2 years either side), sex, and a minimum of four hair Hg concentration measures, of which at least two were in the same year. Analyses included change-point detection, interrupted time series, mixed models, and Cox survival models. FINDINGS: We analysed data collected between Jan 1, 1970, and Jan 31, 1997, for 657 individuals (319 women and 338 men, born between 1884 and 1991) for whom we assembled a retrospective database of yearly measures of hair Hg concentration (n=3603). Hair Hg concentration decreased over time. A subgroup of 222 individuals (107 women and 115 men) reached or could have reached 60 years old by August, 2019. There was an increased risk of dying at a younger age among those with at least one hair Hg measure of 15 µg/g or more (adjusted hazard ratio 1·55, 95% CI 1·11-2·16; p=0·0088). Among the deceased individuals (n=154), longevity decreased by 1 year with every 6·25 µg/g (4·35-14·29) increase in hair Hg concentration. Analyses of 36 matched pairs showed that hair Hg concentration of those who died aged younger than 60 years was 4·7 times higher (3·4-5·9) than controls. INTERPRETATION: The consistent findings between our different analyses support an association between long-term Hg exposure from freshwater fish consumption and premature mortality in this First Nation community. There is a need to do risk-benefit analyses of freshwater fish consumption in environmentally contaminated regions. FUNDING: Canadian Institutes of Health Research.

Rural development and shifts in household dietary practices from 1999 to 2010 in the Tapajós River region, Brazilian Amazon: empirical evidence from dietary surveys.

BACKGROUND: Research on changing dietary practices is rare in lower and middle income countries, and understanding the impact of global economic processes on population health and nutrition is important, especially of rural communities. We analyzed the diet of 22 families in Brasília Legal, a riverside community in the Tapajós River region of the Brazilian Amazon, using nonparametric tests to compare dietary surveys taken in 1999 and 2010. RESULTS: Data from the two surveys show that food obtained through commercial supply chains became more frequent in household diets, corresponding to significant increases in daily consumption of food items rich in energy, protein, and sugar. At the same time, there was a decline in traditional Amazonian food intake. CONCLUSIONS: Comparing these results with household socio-economic characteristics and drawing on open-ended interviews, we consider the multiple influences that economic development processes may have had on local diets. The introduction of new income sources and employment opportunities, infrastructural and transportation expansion, as well as environmental change appear to have influenced the observed dietary shifts. Such shifts are likely to have important implications for the nutritional status of communities in the Amazon, highlighting concerning trade-offs between current development trajectories and human health. Public policies and health education programs must urgently consider the interactions between sustainable development priorities in order to address emerging health risks in this rapidly changing region.

Caribou (Rangifer tarandus) and Inuit Nutrition Security in Canada.

Caribou (Rangifer tarandus) has been fundamental to the diet and culture of Arctic Indigenous Peoples for thousands of years. Although caribou populations observe natural cycles of abundance and scarcity, several caribou herds across the Circumpolar North have experienced dramatic declines in recent decades due to a range of interrelated factors. Broadly, the objectives of this study are to examine food and nutrition security in relation to wildlife population and management status across Inuit Nunangat (the Inuit homeland, consisting of four regions across the Canadian Arctic). Specifically, we: (1) characterize the contribution of caribou to Inuit nutrition across northern Canada and (2) evaluate the population and management status of caribou herds/populations harvested by Inuit. Dietary data were derived from the 2007-2008 Inuit Health Survey, which included dietary information for Inuit adults (n = 2097) residing in thirty-six communities, spanning three regions (the Inuvialuit Settlement Region, Nunavut, and Nunatsiavut) of the Canadian North. Published information regarding the range, abundance, status, and management status of caribou herds/populations was collected through document analysis and was validated through consultation with northern wildlife experts (territorial governments, co-management, and/or Inuit organizations). While caribou contributed modestly to total diet energy (3-11% of intake) across the regions, it was the primary source of iron (14-37%), zinc (18-41%), copper (12-39%), riboflavin (15-39%), and vitamin B12 (27-52%), as well as a top source of protein (13-35%). Restrictions on Inuit subsistence harvest (harvest quotas or bans) are currently enacted on at least six northern caribou herds/populations with potential consequences for country food access for over twenty-five Inuit communities across Canada. A holistic multi-sectorial approach is needed to ensure the sustainability of wildlife populations, while supporting Inuit food and nutrition security in the interim.

Perinatal MAO Inhibition Produces Long-Lasting Impairment of Serotonin Function in Offspring.

In addition to transmitter functions, many neuroamines have trophic or ontogenetic regulatory effects important to both normal and disordered brain development. In previous work (Mejia et al., 2002), we showed that pharmacologically inhibiting monoamine oxidase (MAO) activity during murine gestation increases the prevalence of behaviors thought to reflect impulsivity and aggression. The goal of the present study was to determine the extent to which this treatment influences dopamine and serotonin innervation of murine cortical and subcortical areas, as measured by regional density of dopamine (DAT) and serotonin transporters (SERT). We measured DAT and SERT densities at 3 developmental times (PND 14, 35 and 90) following inhibition of MAO A, or MAO B or both throughout murine gestation and early post-natal development. DAT binding was unaltered within the nigrostriatal pathway, but concurrent inhibition of MAO-A and MAO-B significantly and specifically reduced SERT binding by 10⁻25% in both the frontal cortex and raphe nuclei. Low levels of SERT binding persisted (PND 35, 90) after the termination (PND 21) of exposure to MAO inhibitors and was most marked in brain structures germane to the previously described behavioral changes. The relatively modest level of enzyme inhibition (25⁻40%) required to produce these effects mandates care in the use of any compound which might inhibit MAO activity during gestation.

Psychometric validation of the household food insecurity access scale among Inuit pregnant women from Northern Quebec.

BACKGROUND: Globally, food insecurity is a major public health concern. In North America, it is particularly prevalent in certain sub-groups, including Indigenous communities. Although many Indigenous and remote communities harvest and share food, most food security assessment tools focus on economic access. This study describes the psychometric evaluation of a modified Household Food Insecurity Access Scale (HFIAS), developed for mixed economies, to assess food insecurity among pregnant Inuit women. METHODS: The HFIAS was administered to 130 pregnant women in Nunavik (Arctic region of Quebec), Canada. Data were fit to a Rasch Rating Scale Model (RSM) to determine the discrimination ability of the HFIAS. Person parameter (Theta) estimates were calculated based on the RSM to provide a more accurate scoring system of the modified HFIAS for this population. Theta values were compared to known correlates of food insecurity. RESULTS: Comparative fit indices showed preference for a modified version of the HFIAS over the original. Theta values displayed a continuum of severity estimates and those values indicating greater food insecurity were consistently linked to known correlates of food insecurity. Participants living in households with more than 1 hunter (Theta = -.45) or more than 1 fisher (Theta = -.43) experienced less food insecurity than those with no hunters (Theta = .48) or fishers (Theta = .49) in their household. The RSM indicated the scale showed good discriminatory ability. Subsequent analyses indicated that most scale items pertain to the classification of a household as moderately food insecure. CONCLUSIONS: The modified HFIAS shows potential for measuring food insecurity among pregnant women in Nunavik. This is an efficient instrument that can inform interventions targeting health conditions impacting groups that obtain food through both monetary and non-monetary means.

Development of a strategic plan for food security and safety in the Inuvialuit Settlement Region, Canada.

BACKGROUND: Current social and environmental changes in the Arctic challenge the health and well-being of its residents. Developing evidence-informed adaptive measures in response to these changes is a priority for communities, governments and researchers. OBJECTIVES: To develop strategic planning to promote food security and food safety in the Inuvialuit Settlement Region (ISR), Northwest Territories (NWT), Canada. DESIGN: A qualitative study using group discussions during a workshop. METHODS: A regional workshop gathered Inuit organizations and community representatives, university-based researchers from the Inuit Health Survey (IHS) and NWT governmental organizations. Discussions were structured around the findings from the IHS. For each key area, programs and activities were identified and prioritized by group discussion and voting. RESULTS: The working group developed a vision for future research and intervention, which is to empower communities to promote health, well-being and environmental sustainability in the ISR. The group elaborated missions for the region that address the following issues: (a) capacity building within communities; (b) promotion of the use of traditional foods to address food security; (c) research to better understand the linkages between diseases and contaminants in traditional foods, market foods and lifestyle choices; (d) and promotion of affordable housing. Five programs to address each key area were developed as follows: harvest support and traditional food sharing; education and promotion; governance and policy; research; and housing. Concrete activities were identified to guide future research and intervention projects. CONCLUSIONS: The results of the planning workshop provide a blueprint for future research and intervention projects.

Identification of environmental sources of lead exposure in Nunavut (Canada) using stable isotope analyses.

BACKGROUND: Blood lead levels (BLLs) were measured in the adult Inuit population of Nunavut, Northern Canada, during the Inuit Health Survey (IHS) in 2007-2008. Approximately 10% of the adult participants had BLL over the Health Canada's guidance of 100µg/L. OBJECTIVES: 1) To repeat the measurement of BLL among the IHS participants with high BLL and household members including pregnant women and children under 10years of age; 2) to measure lead (Pb) concentrations in environmental samples to identify potential sources and 3) to explore how Pb from environmental samples contributes to BLL using Pb stable isotopic analyses. METHODS: Blood samples were collected from 100 adults and 56 children in 2012. A total of 169 environmental samples (tap water, house dust, paint, country food, soil, and ammunition) were collected from 14 houses from three communities where the IHS participants had the highest BLL. Total Pb concentrations and Pb isotope mass balance were determined by inductively coupled plasma-mass spectrometry (ICP-MS). RESULTS: The geometric mean of BLL was 43.1µg/L; BLL increased with age and was higher in adults than children (71.1 vs. 17.5µg/L). Median Pb concentrations in water (1.9µg/L) and dust (27.1µg/m(2) for wiped dust, 32.6mg/kg for vacuum dust coarse fraction, and 141.9mg/kg for vacuum dust fine fraction) were generally higher than in other parts of Canada. Median Pb concentrations of food and soil coarse and fine fractions were low (36.6µg/kg, 5.4mg/kg and 11.8mg/kg respectively); paint chips exceeded the Canadian guidelines in two houses (median: 3.8mg/kg). Discriminant analyses and isotope ratio analyses showed that ammunition and house dust are major sources of Pb in this study population. CONCLUSION: Analyses of Pb stable isotopes are useful to identify the routes of exposure to Pb. This approach can contribute to develop targeted public health programmes to prevent Pb exposure.

Toxic risks and nutritional benefits of traditional diet on near visual contrast sensitivity and color vision in the Brazilian Amazon.

BACKGROUND: Visual functions are known to be sensitive to toxins such as mercury (Hg) and lead (Pb), while omega-3 fatty acids (FA) and selenium (Se) may be protective. In the Tapajós region of the Brazilian Amazon, all of these elements are present in the local diet. OBJECTIVE: Examine how near visual contrast sensitivity and acquired color vision loss vary with biomarkers of toxic exposures (Hg and Pb) and the nutrients Se and omega-3 FA in riverside communities of the Tapajós. METHODS: Complete visuo-ocular examinations were performed. Near visual contrast sensitivity and color vision were assessed in 228 participants (≥15 years) without diagnosed age-related cataracts or ocular pathologies and with near visual acuity refracted to at least 20/40. Biomarkers of Hg (hair), Pb (blood), Se (plasma), and the omega-3 FAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in plasma phospholipids were measured. Multiple linear regressions were used to examine the relations between visual outcomes and biomarkers, taking into account age, sex, drinking and smoking. RESULTS: Reduced contrast sensitivity at all spatial frequencies was associated with hair Hg, while %EPA, and to a lesser extent %EPA+DHA, were associated with better visual function. The intermediate spatial frequency of contrast sensitivity (12 cycles/degree) was negatively related to blood Pb and positively associated with plasma Se. Acquired color vision loss increased with hair Hg and decreased with plasma Se and %EPA. CONCLUSIONS: These findings suggest that the local diet of riverside communities of the Amazon contain toxic substances that can have deleterious effects on vision as well as nutrients that are beneficial for visual function. Since remediation at the source is a long process, a better knowledge of the nutrient content and health effects of traditional foods would be useful to minimize harmful effects of Hg and Pb exposure.

No evidence of selenosis from a selenium-rich diet in the Brazilian Amazon.

Selenium (Se) is an essential element and a well-known anti-oxidant. In the Lower Tapajós River region of the Brazilian Amazon, biomarkers of Se range from normal to very high. The local traditional diet includes important Se sources such as Brazil nuts, chicken, game meat and certain fish species. Some studies have reported alterations in keratin structure, gastrointestinal problems and paresthesia in populations with high Se intake. The objective of the present study was to evaluate cutaneous and garlic odor of the breath signs and sentinel symptoms of Se toxicity (selenosis) in relation to Se status in communities along the Tapajós River. Participants (N=448), aged 15-87 years, were recruited from 12 communities. Se concentrations were measured in blood (B-Se) and plasma (P-Se) by ICP-MS. A nurse performed an examination of the hair, nails, skin and breath for signs of Se toxicity. Interview-administered questionnaires were used to collect information on socio-demographics, medical history and possible symptoms of Se toxicity. In this population, the median levels of B-Se and P-Se were 228.4 µg/L (range 103.3-1500.2 µg/L) and 134.8 µg/L (range 53.6-913.2 µg/L) respectively. Although B-Se and P-Se surpassed concentrations considered toxic (B-Se: 1000 µg/L (U.S. EPA, 2002)), no dermal or breath signs or symptoms of Se toxicity were associated with the biomarkers of Se status. In the present study population, where Se intake is mostly from traditional diet, there is no evidence of selenosis. These findings support the need to re-assess Se toxicity considering factors such as the chemical form of Se exposure, route of exposure (inhaled versus ingested), co-exposures to toxic elements such as mercury. Considering the current food transition towards a western diet in the Amazon, further studies should address the possible association between high Se status and cardiometabolic health in this study population.

Neurotoxic sequelae of mercury exposure: an intervention and follow-up study in the Brazilian Amazon.

Since 1995, the Caruso Project used an Ecosystem Approach to Human Health to examine mercury (Hg) exposure in fish-eating communities in the Brazilian Amazon and develop interventions to maximise nutrition from traditional diet and minimise toxic risk. In 1995, 2000 and 2006, this study followed fish consumption, Hg levels, and visual and motor functions in 31 villagers. Questionnaires gathered information on socio-demographics and diet. Hair Hg (H-Hg) levels were measured. Visual acuity, colour vision, manual dexterity and grip strength were assessed. Data was analysed using general linear models of repeated measures. Total fish consumption, similar in 1995 and 2000, decreased in 2006. Carnivorous fish consumption initially decreased and then remained stable, whereas non-carnivorous fish consumption first increased and then decreased. H-Hg declined from 17.6 to 7.8 µg/g. Visual functions showed a significant decrease over time, with those with H-Hg ≥ 20 µg/g in 1995 showing greater loss. Motor functions showed initial improvement and then returned to the 1995 performance level. Decrease in Hg exposure is attributed to the intervention and socio-economic changes in the village. While there may be a certain reversibility of motor deficits, visual capacities may decrease progressively with respect to exposure prior to the intervention.

Visual acuity in fish consumers of the Brazilian Amazon: risks and benefits from local diet.

OBJECTIVE: To examine the associations between near and distant visual acuity and biomarkers of Hg, Pb, n-3 fatty acids and Se from the local diet of fish-eating communities of the Tapajós River in the Brazilian Amazon. DESIGN: Visuo-ocular health and biomarkers of Hg (hair, whole blood, plasma), Pb (whole blood), Se (whole blood and plasma) and n-3 fatty acids (plasma total phospholipids) were assessed in a cross-sectional study. SETTING: Lower Tapajós River Basin (State of Pará, Brazil), May to July 2006. SUBJECTS: Two hundred and forty-three adults (≥15 years) without diagnosed age-related cataracts or ocular pathologies. RESULTS: Near visual acuity was negatively associated with hair Hg and positively associated with %DHA, with a highly significant Log Hg × age interaction term. Stratifying for age showed that while young people presented good acuity, for those aged ≥40 years, clinical presbyopia was associated with hair Hg ≥ 15 µg/g (OR = 3·93, 95% CI 1·25, 14·18) and %DHA (OR = 0·37, 95% CI 0·11, 1·11). A similar age-related pattern was observed for distant visual acuity in relation to blood Pb, but the evidence was weaker. CONCLUSIONS: These findings suggest that Hg and Pb may affect visual acuity in older persons, while DHA appears to be protective for near visual acuity loss. In this population, with little access to eye care, diet may have an important influence on visuo-ocular ageing.

Biomarkers of methylmercury exposure immunotoxicity among fish consumers in Amazonian Brazil.

BACKGROUND: Mercury (Hg) is a ubiquitous environmental contaminant with neurodevelopmental and immune system effects. An informative biomarker of Hg-induced immunotoxicity could aid studies on the potential contribution to immune-related health effects. OBJECTIVES: Our objectives were to test the hypothesis that methylmercury (MeHg) exposures affect levels of serum biomarkers and to examine interactions between Hg and selenium (Se) in terms of these responses. METHODS: This cross-sectional epidemiological study assessed adults living along the Tapajós River, a system long affected by MeHg. We measured antinuclear (ANA) and antinucleolar (ANoA) autoantibody levels and eight cytokines in serum samples (n = 232). Total Hg (including MeHg) and Se were measured in blood, plasma, hair, and urine. RESULTS: The median (range) total Hg concentrations were 14.1 µg/g (1.1-62.4), 53.5 µg/L (4.3-288.9), 8.8 µg/L (0.2-40), and 3.0 µg/L (0.2-16.1) for hair, blood, plasma, and urine, respectively. Elevated titers of ANA (but not ANoA) were positively associated with MeHg exposure (log-transformed, for blood and plasma), unadjusted [odds ratio (OR) = 2.6; 95% confidence interval (CI): 1.1, 6.2] and adjusted for sex and age (OR = 2.9; 95% CI: 1.1, 7.5). Proinflammatory [interleukin (IL)-6 and interferon (IFN)-γ], anti-inflammatory (IL-4), and IL-17 cytokine levels were increased with MeHg exposure; however, in the subset of the population with elevated ANA, proinflammatory IL-1ß, IL-6, IFN-γ, and tumor necrosis factor (TNF)-α and anti-inflammatory (IL-4) cytokine levels were decreased with MeHg exposure. Although Se status was associated with MeHg level (correlation coefficient = 0.86; 95% CI: 0.29, 1.43), Se status was not associated with any changes in ANA and did not modify associations between Hg and ANA titers. CONCLUSIONS: MeHg exposure was associated with an increased ANA and changes in serum cytokine profile. Moreover, alterations in serum cytokine profiles differed based on ANA response, suggesting a specific phenotype of MeHg susceptibility. Further research on the potential health implications of these observed immunological changes is warranted.

Selenium from dietary sources and motor functions in the Brazilian Amazon.

Selenium (Se) is a well-known anti-oxidant with a critical role in the proper functioning of nervous and muscle functions. Se deficiency has been associated with both cognitive and neuromotor impairment, while sensory and motor deficits have been attributed to excess Se. In the Lower Tapajós Region of the Brazilian Amazon, riverside populations present a wide range of Se levels. These fish-eating communities have among the highest mercury (Hg) exposures reported in the world today, and recently, lead (Pb) exposure has been identified. Some studies suggest that Se intake can be protective for Hg and/or Pb toxicity, however, data from animal and human studies are inconsistent. The objective of the present study was to examine the relations between biomarkers of Se and motor functions, taking into account co-variables and biomarkers of exposure to Hg and Pb. Participants (n=448), aged 15-87 y, were recruited from 12 communities along the Tapajós River. Se concentrations were measured in whole blood (B-Se), plasma (P-Se), hair (H-Se) and urine (U-Se) by ICP-MS. Whole blood Hg (B-Hg) and Pb (B-Pb) were also measured by ICP-MS. Interview-administered questionnaires served to collect information on socio-demographics and medical history. All participants underwent a complete visual examination and performed tests of motor functions (Branches Alternate Movement Task, Santa Ana Test, Dynamometer and Grooved Pegboard Test). B-Se varied from 103 to 1500 µg/L (median 228 µg/L), P-Se from 53.6 to 913 µg/L (median 135 µg/L), H-Se from 0.4 to 3.8 µg/g (median 0.7 µg/g) and U-Se from 2.3 to 1375 µg/g cr. (median 33.6 µg/g cr.). Median B-Hg and B-Pb levels were 42.5 µg/L and 113 µg/L respectively. In multivariable analysis, Se biomarkers (log-transformed) were positively related to better performance on all motor tests, taking into account socio-demographic co-variables and B-Hg and B-Pb levels. P-Se consistently showed stronger associations to motor performance compared to the other Se biomarkers. Regression estimates for Se biomarkers were considerably stronger when controlling for B-Hg. When stratifying at the median for B-Hg concentrations, P-Se consistently presented associations with the outcomes only at high B-Hg concentrations. This is the first human study to report beneficial effects of high Se status on motor functions. For this population with elevated Hg exposure, high dietary Se intake may be critical for brain and muscle functions. However, these findings are not necessarily applicable to populations with lower Hg exposure and/or Se status, which is the case for people who do not rely heavily on fish consumption, be they in Brazil, the United States or elsewhere. The associations were mostly observed with P-Se, suggesting that P-Se or plasma selenoproteins may be good biomarkers for these outcomes.

Selenium and mercury in the Brazilian Amazon: opposing influences on age-related cataracts.

BACKGROUND: Age-related cataracts (ARCs) are an important cause of blindness in developing countries. Although antioxidants may be part of the body's defense to prevent ARC, environmental contaminants may contribute to cataractogenesis. In fish-eating populations of the lower Tapajós region, elevated exposure to mercury (Hg) has been reported, and blood levels of selenium (Se) range from normal to very high (> 1,000 microg/L). OBJECTIVES: We examined ARCs in relation to these elements among adults (> or = 40 years of age) from 12 riverside communities. METHODS: Participants (n = 211) provided blood samples and underwent an extensive ocular examination. Inductively coupled plasma mass spectrometry was used to assess Hg and Se in blood and plasma. RESULTS: One-third (n = 69; 32.7%) of the participants had ARC. Lower plasma Se (P-Se; < 25th percentile, 110 microg/L) and higher blood Hg (B-Hg; > or = 25th percentile, 25 microg/L) were associated with a higher prevalence odds ratio (POR) of ARC [adjusted POR (95% confidence interval), 2.69 (1.11-6.56) and 4.45 (1.43-13.83), respectively]. Among participants with high P-Se, we observed a positive but nonsignificant association with high B-Hg exposure, whereas among those with low B-Hg, we observed no association for P-Se. However, compared with the optimum situation (high P-Se, low B-Hg), the POR for those with low P-Se and high B-Hg was 16.4 (3.0-87.9). This finding suggests a synergistic effect. CONCLUSION: Our results suggest that persons in this population with elevated Hg, the cataractogenic effects of Hg may be offset by Se. Because of the relatively small sample size and possible confounding by other dietary nutrients, additional studies with sufficient power to assess multiple nutrient and toxic interactions are required to confirm these findings.