Cross-sectional assessment of infants' exposure to toxic metals through breast milk in a prospective cohort study of mining communities in Ghana

Essential and non-essential element concentrations in human milk samples and the assessment of infants' exposure

As the data concerning element concentrations in human milk (HM) samples and their intake by infants are lacking in Poland, the present study aimed to explore this issue. The material consisted of HM samples obtained from 30 exclusively breastfeeding mothers during 4-6 weeks postpartum. Additionally, to identify the factors that may potentially affect HM composition, information regarding maternal data (anthropometry, body composition, and diet) was also collected. Maternal diet was assessed with two methods-a food frequency questionnaire and 3-day dietary records. In total, 18 essential and non-essential elements were determined. For the elements analysis, we used inductively coupled plasma quadrupole mass spectrometry. Most of the elements (n = 11, 61%) were detected in all HM samples. In all HM samples tin concentration was higher (5.67 ± 2.39 μg/L) than the usual range reported by the World Health Organization (~ 1.0 μg/L). HM cadmium content was positively associated with maternal salty snacks intake (r = 0.502, p = 0.005), arsenic with whole-grain products intake (r = 0.37, p = 0.043), and mercury concentration with fruits and seeds/nuts consumption (r = 0.424, p = 0.042 and r = 0.378, p = 0.039, respectively). Higher HM lead concentration was predicted by maternal age (95% CI [0.94-0.97]), intake of fish (95% CI [1.01-1.03]), and vegetables (95% CI [1.02-1.06]). The highest infants' intake was observed for copper (35.24 ± 12.48) and the lowest for arsenic (0.076 ± 0.102). Infants' exposure to lead was associated with maternal frequency consumption of canned fish (p = 0.0045). There is a need to perform further research on this topic to maximize the benefits of breastfeeding by minimizing maternal and infant exposure to potentially toxic elements.

Concentrations of Lead and Arsenic in Mother's Milk and Children's Blood in Peruvian Breastfeeding Dyads

BACKGROUND

Toxic trace elements could enter human milk through mothers' food consumption, drinking water, air, or incidental soil ingestion, and are of concern to the nursing infant.

RESEARCH AIM

To determine the concentration of toxic trace elements (lead and arsenic) in Peruvian mothers' milk and their association with blood concentrations in their own infants 3-20 months old.

METHOD

This exploratory, cross-sectional study, carried out in Peru, included breastfeeding mother/child dyads (N = 40). Following standardized protocols, biospecimens of human milk and child's blood were collected.

RESULTS

Lead and arsenic concentrations in milk were above the method detection limits in 73% and 100% of samples with median concentrations of 0.26 µg/L (IQR = 0.10, 0.33 µg/L) and 0.73 µg/L (IQR = 0.63, 0.91 µg/L), respectively. Concentrations of lead and arsenic in blood were 2.05 µg/dL (SD = 1.35), and 1.43 µg/dl (geometric mean: SD = 1.39), respectively. Blood lead concentrations in 12.5% (n = 5) of the samples were above the U.S. Center for Disease Control and Prevention reference value (< 3.5 µg/dl), and over half of arsenic concentrations were above the acceptable levels of < 1.3 µg/dl (Mayo Clinic Interpretative Handbook). Our results showed that for every one-month increase in age, lead blood concentrations increased by 0.1 µg/dl (p = 0.023). Additionally, every 1 µg/L increase in the mother's milk arsenic was associated with a 1.40 µg/dl increase in the child's blood arsenic concentration.

CONCLUSIONS

Implementing effective interventions to decrease the toxic exposure of reproductive-aged women is needed in Peru and worldwide.

Correlates of whole blood metal concentrations among reproductive-aged Black women

BACKGROUND

Metals may influence reproductive health, but few studies have investigated correlates of metal body burden among reproductive-aged women outside of pregnancy. Furthermore, while there is evidence of racial disparities in exposure to metals among U.S. women, there is limited research about correlates of metal body burden among Black women.

OBJECTIVE

To identify correlates of whole blood metal concentrations among reproductive-aged Black women.

METHODS

We analyzed cross-sectional data from a cohort of 1664 Black women aged 23-35 years in Detroit, Michigan, 2010-2012. We collected blood samples and questionnaire data. We measured concentrations of 17 metals in whole blood using inductively-coupled plasma-mass spectrometer-triple quadrupole and total mercury using Direct Mercury Analyzer-80. We used multivariable linear regression models to identify sociodemographic, environmental, reproductive, and dietary correlates of individual metal concentrations.

RESULTS

In adjusted models, age was positively associated with multiple metals, including arsenic, cadmium, and mercury. Education and income were inversely associated with cadmium and lead. Current smoking was strongly, positively associated with cadmium and lead. Alcohol intake in the past year was positively associated with arsenic, barium, copper, lead, mercury, vanadium, and zinc. Having pumped gasoline in the past 24 h was positively associated with cadmium, chromium, and molybdenum. Having lived in an urban area for the majority of residence in Michigan was positively associated with arsenic, lead, and nickel. Higher water intake in the past year was positively associated with several metals, including lead. Fish intake in the past year was positively associated with arsenic, cesium, and mercury. We also observed associations with body mass index, season, and other environmental, reproductive, and dietary factors.

SIGNIFICANCE

We identified potential sources of exposure to metals among reproductive-aged Black women. Our findings improve understanding of exposures to metals among non-pregnant reproductive-aged women, and can inform policies in support of reducing disparities in exposures.

IMPACT STATEMENT

There are racial disparities in exposures to metals. We analyzed correlates of blood metal concentrations among reproductive-aged Black women in the Detroit, Michigan metropolitan area. We identified sociodemographic, anthropometric, lifestyle, environmental, reproductive, and dietary correlates of metal body burden. Age was positively associated with several metals. Education and income were inversely associated with cadmium and lead, indicating socioeconomic disparities. We identified potential exposure sources of metals among reproductive-aged Black women, including smoking, environmental tobacco smoke, pumping gasoline, living in an urban area, and intake of alcohol, water, fish, and rice.

The impact of the 2019/2020 Australian landscape fires on infant feeding and contaminants in breast milk in women with asthma

BACKGROUND

The 2019/2020 Australian landscape fires (bushfires) resulted in prolonged extreme air pollution; little is known about the effects on breastfeeding women and their infants. This study aimed to examine the impact of prolonged landscape fires on infant feeding methods and assess the concentration of polycyclic aromatic hydrocarbons (PAHs) and elements in breast milk samples.

METHODS

From May - December 2020, women with asthma, who were feeding their infants during the fires, were recruited from an existing cohort. Data on infant feeding and maternal concern during the fires were retrospectively collected. Breast milk samples were collected from a sample of women during the fire period and compared with samples collected outside of the fire period for levels of 16 PAHs (gas chromatography coupled with mass spectrometry), and 20 elements (inductively coupled plasma-mass spectrometry).

RESULTS

One-hundred-and-two women who were feeding infants completed the survey, and 77 provided 92 breast milk samples. Two women reported concern about the impact of fire events on their infant feeding method, while four reported the events influenced their decision. PAHs were detected in 34% of samples collected during, versus no samples collected outside, the fire period (cross-sectional analysis); specifically, fluoranthene (median concentration 0.015 mg/kg) and pyrene (median concentration 0.008 mg/kg) were detected. Women whose samples contained fluoranthene and pyrene were exposed to higher levels of fire-related fine particulate matter and more fire days, versus women whose samples had no detectable fluoranthene and pyrene. Calcium, potassium, magnesium, sodium, sulphur, and copper were detected in all samples. No samples contained chromium, lead, nickel, barium, or aluminium. No statistically significant difference was observed in the concentration of elements between samples collected during the fire period versus outside the fire period.

CONCLUSIONS

Few women had concerns about the impact of fire events on infant feeding. Detection of fluoranthene and pyrene in breast milk samples was more likely during the 2019/2020 Australian fire period; however, levels detected were much lower than levels expected to be related to adverse health outcomes.

Toxic metal and trace element status in the breast milk of Turkish new-born mothers

BACKGROUND AND AIM

This study aims to evaluate the toxic metal and trace element concentrations in breast milk obtained from new-born nursing mothers in rural Giresun province, located on the coast of the Black Sea.

METHODS

Milk samples were randomly collected once from early lactation of 50 nursing mothers. Inductively coupled plasma mass spectrometry was used to analyse the concentrations of iron (Fe), nickel (Ni), manganese (Mn), cobalt (Co), chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), molybdenum (Mo), cadmium (Cd) and lead (Pb) in the breast milk. Shapiro-Wilk test was used to evaluate the distribution of data. The Pearson-J correlation was used for normally distributed elements, and Spearman correlation analysis was used for others.

RESULTS

The mean amounts of elements were 3.36 µg kg^-1 of Cr, 9.26 µg kg^-1 of Mn, 797 µg kg^-1 of Fe, 1.99 µg kg^-1 of Ni, 5.92 µg kg^-1 of Cu, 379 µg kg^-1 of Zn and 2.23 µg kg^-1 of Pb. Co, As, Mo and Cd concentrations were below the detection limit. A highly significant correlation was found between iron and Nickel in breast milk.

CONCLUSION

Our findings were evaluated in comparison with the WHO data, and whether they were in accordance with the recommended Dietary Reference Intake (DRI) values for 0-6-months-old infants was calculated. Pb levels were similar to those of WHO, while As and Cd were below the measurable limit. Fe, Mn, and Cr concentrations were higher than WHO data, while Co, Ni, Cu and Zn were lower. This research is the first study conducted in this region.

Toxic metal exposures from infant diets: Risk prevention strategies for caregivers and health care professionals

Concerns are growing regarding the presence of toxic elements such as arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) in the ingredients and prepared foods for infants and young children. There are few clear, evidence-based, guidelines on the maximum tolerable limits of toxicants in foods and little understanding of toxicant exposure or adverse health effects attributable to dietary exposure. Caregivers are faced with the burden of making decisions about which foods to select, how often to feed them to their children, and what foods to limit. This article reviews the current literature and existing recommendations on dietary exposure to toxic elements in children under 2 years of age, and their health effects in early childhood-focusing on growth, neurodevelopment, and immune function. The article also outlines best practices for healthcare providers to address the concerns of toxic element exposure through the diet in young children. Several foods consistently appear in the literature as potential sources of toxic element exposure. Contaminated drinking and cooking water, including water used to prepare infant formula, could also be a major exposure source. In the absence of stronger evidence on effects of dietary modification, exclusive breastfeeding until six months of age, followed by a diverse diet are some strategies to reduce dietary toxic element exposure while ensuring an adequate and balanced nutrient intake. Healthcare providers can support families by sharing information and encouraging blood Pb testing, the only element for which such testing is currently recommended.

The concentration and health risk of potentially toxic elements (PTEs) in the breast milk of mothers: a systematic review and meta-analysis

AIM

Breast milk is the best source of nutrition for a newborn during the first six months of his or her life. However there is a possibility that breast milk may contain pollutants such as metals. The current meta-analytic study assessed the concentration of potentially toxic elements (PTEs), including lead (Pb), cadmium (Cd), arsenic (As), Iron (Fe), Zinc (Zn), copper (Cu), and nickel (Ni), in mothers' milk.

METHOD

The literature studies regarding the concentrations of PTEs in the breast milk of mothers were collected from international databases such as PubMed, Scopus, Web of Science, and Embase. Afterward, the Total Target Hazard Quotient (TTHQ) by Monte Carlo Simulation (MCS) model was used to assess the non-carcinogenic risk.

RESULTS AND DISCUSSION

According to 42 of the 836 retrieved articles, the PTE concentrations in mother's milk were as follows: Cu (1.84 mg/kg) > Zn (1.80 mg/kg) > Fe (1.03 mg/kg) > Ni (0.60 mg/kg) > Pb (0.10 mg/kg) > As (0.15 mg/kg) ≈ Cd (0.15 mg/kg). Based on the containment type, the highest concentrations of As (2.80 mg/kg), Cd (0.07 mg/kg), and Pb (2.68 mg/kg) were related to Western Pacific Region (WPRO), European Region (EURO), and WPRO, respectively. In addition, for trace elements, Eastern Mediterranean Region (EMRO) was the region with the highest concentrations of Cu (3.56 mg/kg), Fe (2.78 mg/kg), Ni (3.13 mg/kg), and Zn (5.58 mg/kg) were related to Lastly, the non-carcinogenic risk assessment of the PTEs in breast milk indicated different risk patterns in various countries, and the calculated TTHQ level in infants was below 1.

CONCLUSION

Overall, human breast milk was generally safe for infants to consume and poses no risks to their health.

Sources of Lead Exposure in West Africa

This commentary is an investigation of sources of lead (Pb) exposure in West Africa. Pb is generally acknowledged as one of the most widespread environmental health hazards in West Africa, and there is heightened concern over adverse health effects at various levels of exposure (at doses once considered safe) in the West African region. A literature review for the possible health implications of Pb exposure on human health showed nervous system dysfunction, anemia, and potential cognitive diseases as the major health issues among children, while adults were found to suffer more from cardiovascular dysfunction, neurological decline, and reproductive diseases. Despite a decline in blood lead levels (BLLs), lead exposure continues to be a major public health concern as no level of Pb exposure can be considered safe. Moreover, lowering BLLs entails identifying various lead sources such as gasoline emissions, leaded paint, canned foods, and beverages, as well as plausible biological pathways of lead exposure and response. However, only countries such as Nigeria and Ghana have extensive research available regarding the different sources of Pb exposure. Further, it is not apparent which country is affected the most by Pb exposure. Therefore, this commentary was aimed to explore different literature sources to describe and list the different sources of Pb exposure in 15 West African countries. The findings indicated water, food, and occupational exposure as the major sources of Pb exposure in the region. People with occupations such as e-waste and Pb acid battery recycling, auto mechanics, fuel attending, welding, electronic repairing, farming/spraying, and mining were found to be at immediate risk. Tobacco, spices and paints constituted additional potential sources of exposure. For residents living near landfills or urban area, the major sources of Pb exposure were soil, air, and dust particles. The review revealed a vast research gap on the sources and implications of Pb exposure. Exposure to Pb could further increase due to uncontrolled traffic, urban growth, inadequate urban planning, and the inadequate enforcement of regulations. Therefore, more extensive research on the changing trends of Pb exposure among West African populations is needed.

Environmental distribution and risk of exposure of Heavy Metal Pollutants from Lolgorian Artisanal Gold Mining in Kenya

The aim of the study was to assess the distribution of heavy metals in the environmental compartments from artisanal and small-scale gold mining (ASGM) activities from Lolgorian, Kenya. The investigation was carried out using Inductively-Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Mercury (p > 0.05) (p = 0.755), arsenic (p = 0.182), and lead (p = 0.430) mean concentrations in soil, water, sediments, and ore were not significantly different. The mean mercury, lead, and arsenic concentrations in the water were 0.66 mg/L, 0.46 mg/L, and 1.25 mg/L, respectively. In sediments, the mean values of Cr (66.65 mg/kg), Zn (45.62 mg/kg), Hg (24.63 mg/kg), Pb (22.35 mg/kg), Cd (0.90 mg/kg), and Mn (613.10 mg/kg) were found to be significantly higher. A positive correlation between ore-tailings (r = 0.971109), tailings-sediment (r = 0.9441036), and ore-sediment (r = 0.9441036), was observed indicating the presence of harmful heavy metals in the environment in excess of national and World Health Organization (WHO) recommended threshold, posing a high risk of multiple human exposure pathways.

Kidney Cadmium Concentrations in an Urban Sri Lankan Population: an Autopsy Study

Contamination and bioaccumulation of toxic heavy metals in our geo-environment is a growing public health concern. Human biomonitoring is an essential step in assessing the population risk of chronic exposure to environmental contaminants. Whole kidneys collected from a cohort of 92 deceased individuals undergoing forensic autopsies in Colombo, Sri Lanka, were analysed for cadmium (Cd) bioaccumulation using ICP-MS. Mean age of the population was 55.4 ± 15.4 years. Mean and median renal Cd concentrations of the total population were 4.38 and 2.60 μg g^-1 w/w, respectively, which were below estimated toxic ranges. Males accumulated higher levels of Cd than females (p = 0.377). Cd concentrations were higher in the < 60 age group than the > 60 age group (p = 0.92), while the highest levels were reported in 51-60 age group. However, no significant correlation was found between renal Cd concentration and age (Ʈ_b = - 0.005, p = 0.94). Individuals who smoked, chewed betel or consumed alcohol were found to have elevated renal Cd concentrations in comparison to those who did not use these substances. This is the largest autopsy study on renal Cd bioaccumulation in Sri Lanka, and the findings do not indicate a high exposure risk to environmental Cd contamination at present.

Health Risk Assessments of Selected Trace Elements and Factors Associated with Their Levels in Human Breast Milk from Pretoria, South Africa

While breast milk is the recommended food for infants up to at least six months, exogenously derived compounds such as trace elements have been widely reported in human milk which may make it become toxic or a source of pollutants to the infants. Numerous short- and long-term health effects have been associated with high body-burdens of trace elements, which are amplified in infants. The current study determined the levels and possible contributing factors of six trace elements in breast milk of nursing mothers from a local hospital in Pretoria. Extraction of trace elements employed a digestion technique using perchloric and nitric acid in a ratio of 1:3, while Inductively Coupled Plasma-Membrane Spectrophotometry was used to identify and quantify their levels in breast milk. Concentrations of Cr and Mn were the highest in breast milk, with values ranging from 0.30 to 5.72 µg/L and 0.23 to 5.13 µg/L, respectively. Levels of Co, As, Pb and Cd ranged from Collapse

Key Words

• arsenic
• breast milk and passive smoking
• chromium
• manganese

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MESH Headings

• Environmental Pollutants
• Female
• Humans
• Milk, Human/chemistry
• Risk Assessment
• South Africa
• Trace Elements/analysis

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Grants Collapse

Affiliation(s)

Joshua O. Olowoyo Department of Biology, Sefako Makgatho Health Sciences University, P.O Box 139, Pretoria 0204, South Africa; (L.R.M.); (P.M.M.)
Linda R. Macheka
Phiona M. Mametja

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Neurodevelopment and exposure to neurotoxic metal(loid)s in environments polluted by mining, metal scrapping and smelters, and e-waste recycling in low and middle-income countries

This review covers a wide body of literature to gain an understanding of the impacts of informal activities related to metal extraction (primary mining and recycling) on early life exposure to neurotoxicants and on neurodevelopment. In primary mining, gold extraction with Hg amalgamation is the main environmental cause of Hg pollution in most artisanal small-scale gold mining (ASGM) activities around the world. Nevertheless, in Sub-Saharan Africa (SSA), Pb disrupted from gold-related ores, mining, and artisanal cookware production are an important neurotoxicant that seriously contaminates the affected population, with devastating effects on children. In e-waste recycling settings, the range of neurotoxic substances that contaminate mothers and children is wider than in primary mining environments. Thus, Hg and Pb are major pre- and postnatal neurotoxicants affecting children in the informal metal extraction activities and SSA countries show the highest record of human contamination and of neurotoxic effects on children. There are additional sources of neurotoxic contamination from mining and metal processing activities (cyanide tailing in South America and SSA) and/or co-exposure to Hg-containing products such as cosmetics (soaps and Hg-based skin lightning creams in Africa) and pediatric Thimerosal-containing vaccines (TCVs, that breaks down to ethyl-mercury) in current use in middle and low income countries. However, the action of these neurotoxicants (per se or in combination) on children needs more attention and research. Studies show a negative association between biomarkers of all environmental metal(loid)s (As, Cd, Hg, Mn, and Pb) studied and neurodevelopment in young children. Sadly, in many unregulated activities, child labor is widely employed, thus presenting an additional occupational exposure. Children living in polluted environments related to metal processing are disproportionately exposed to a wide range of co-occurring neurotoxic substances. The review showed compelling evidence from highly representative parts of the world (Africa, Asia, and Latin America) that the studied neurotoxic substances negatively affected areas of the brain associated with language, memory and executive function, as well as psychosocial behavior. Protecting the environment and children from unregulated and highly polluting metal extraction and processing are inextricably intertwined and deserve urgent attention.

Essential and toxic elements in human milk concentrate with human milk lyophilizate: A preclinical study

Concentrated human milk (HM-concentrate) can be obtained from the simple and inexpensive method of donated breast milk direct lyophilization. A previous study reported that HM-concentrate contains the adequate amount of main macro- and micronutrients for use as a nutritional resource for preterm infants with very low birth weight admitted to neonatal intensive care units. However, further details need to be elucidated about HM-concentrate composition, particularly its content of essential and potentially toxic trace elements. Therefore, this study aimed to determine the concentration of essential and toxic elements in human milk considered baseline (HM-baseline) and HM-concentrate, as well as to quantify changes in concentration of these elements after the HM concentration process. The concentration of Aluminum, Arsenic, Cadmium, Chromium, Iron, Mercury, Manganese, Nickel, Lead, Selenium, Tin, and Thallium was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). Moreover, Bayesian linear mixed effect models were applied to estimate the mean difference between HM-baseline and HM-concentrate samples. After comparison (HM-concentrate versus HM-baseline), a significant increase in concentration was observed only for Manganese (0.80 μg/L; 95% CrI [0.16; 1.43]) and Selenium (6.74 μg/L; 95% CrI [4.66; 8.86]), while Lead concentration (-6.13 μg/L; 95% CrI [-8.63; -3.61]) decreased. This study provides latest and reliable information about HM composition. After milk concentration by lyophilization, there was a significant increase only in the essential elements Manganese and Selenium. The essential micronutrient content in HM-concentrate was similar or higher than that in preterm mothers' milk, which suggests it is viable for nutritional support of preterm infants. In addition, the low concentrations of potentially toxic elements in HM-concentrate indicates that it is safe for consumption by premature newborns.

The mercury level in hair and breast milk of lactating mothers in Iran: a systematic review and meta-analysis

Exposure to mercury is one of the major global health concerns due to its stability, bioaccumulation and high toxicity. Therefore, the present study was conducted to assess the mean mercury level in hair and breast milk (BM) of Iranian lactating mothers (ILMs) through meta-analysis technique. We conducted a systematic literature search in online electronic databases included main domestic databases (SID, Magiran, Iran medex, Medlib and ISC) and international databases (Embase, Scopus and PubMed) for studies published between 2000 up 2018. Each process of research and evaluation of articles based on inclusion and exclusion criteria is done by two researchers, individually. From10 studies entered to meta-analysis process including 556 ILM, the mean hair mercury level (HML) and mean milk mercury level (MML) was estimated to be 0.15 μg/g (95 CI: 0.11-0.19, I2: 47.6%, P: 0.028) and 0.51 μg/l (95 CI: 0.28-0.74, I2: 1.9%, P: 0.421), respectively. In this meta-analysis, the mean HML and mean MML were estimated to be lower than the standard of World Health Organization (WHO). Although the mean mercury level in hair and BM of ILMs was lower than the WHO standard, but due to toxicity and serious concern of health, management and Periodic monitor are recommended in different cities of the country for evaluate the mercury levels in hair and BM of ILMs and to estimate the infant's exposure.

Infants and mothers levels of mercury in breast milk, urine and hair, data from an artisanal and small-scale gold mining area in Kadoma / Zimbabwe

In Kadoma (Zimbabwe) gold is extracted from ore based on a simple technology using mercury. Women are exposed whilst living in an exposed area, or even more working directly with mercury. Breast fed infants are exposed via mercury contaminated milk and the general environmental mercury exposure. The aim of the study was to measure infants and mothers levels of mercury in urine and hair, as well as in breast milk. In 2006, an environmental epidemiological field study with 120 mother - child pairs was conducted. A non exposed control group (n = 42) was compared with a medium exposed group (n = 51) and a high exposed group (occupational exposure, n = 27). Urine and hair samples from mother and infants plus breast milk samples were analyzed for total mercury. 120 breast milk samples were analyzed, median (maximum) concentrations [μg Hg/l] were (i) control group < 0.50 (1.55), (ii) medium exposed group 1.10 (10.48), (iii) high exposed group 1.20 (24.80) (p < 0,001). Urine and hair results were distributed similarly for infants and mothers, with higher levels according to the exposure subgroup. All specimen results correlated very well with another, indicating there is a pathway between breast milk and infant's level of mercury. The daily uptake of mercury via breast milk was calculated. The reference dose of 0.3°[μg Hg/kg BW/d] was used to compare the burden of the infants. No infant from the control group, but 17.6% of the medium and 18.5% of the high exposed group were above the reference dose. Mercury in breast milk is generally higher in artisanal and small scale gold mining areas. Breast fed infants were burdened with toxic mercury via breast milk and via the general environment, both are important public health issues.

An overview of worldwide and regional time trends in total mercury levels in human blood and breast milk from 1966 to 2015 and their associations with health effects

BACKGROUND

Mercury is a pollutant of global concern. To protect human health and environment from mercury pollution, the Minamata Convention on mercury entered into force in 2017.

OBJECTIVES

To support a future effectiveness evaluation of the convention, this study assesses worldwide and regional time trends of total mercury levels in human blood and breast milk across different population sub-groups in the last half-century prior to entry-into-force of the Minamata Convention. This study also provides an overview of the epidemiological literature showing evidence of associations between mercury exposure (in terms of total mercury levels in whole blood, cord blood, and breast milk) and human health.

METHODS

We searched electronic databases to identify articles published prior to June 14, 2017 and reported total mercury levels in any of three biological matrices (whole blood, cord blood, or breast milk) and/or associations with human health. Temporal trends of total mercury levels in the selected biological matrices across different population sub-groups were estimated using a linear fit of the log-transformed data. In parallel, statistical methods were employed to assess any possible effect of sources of inhomogeneity (i.e. study and population characteristics such as age, sex, ethnicity, source of exposure, sampling period, and geographical region) in the collected studies. Furthermore, a summary of significant and relevant associations between mercury exposure and human health conditions in children and adults was prepared.

FINDINGS

We found significant declines in total mercury levels in whole blood, cord blood, and breast milk between 1966 and 2015. A regional overview of total mercury levels in whole blood, cord blood, and breast milk suggests the highest levels in South America, followed by Africa or Asia whereas the population groups from Europe or North America displayed the lowest levels of total mercury in the selected biological matrices. We observed conclusive consistent associations of mercury exposure with selected health conditions, especially neurodevelopment and neurotoxicity in children and adults. For several other health conditions, reported findings in the collected studies do not support conclusive associations. We also found that several studies demonstrated significant associations between mercury exposure below the USEPA reference level and various health conditions.

CONCLUSIONS

This study provides a worldwide and regional overview of trends in total mercury levels in human blood and breast milk and associated health risks prior to entry-into-force of the Minamata Convention and calls for further epidemiological investigations from across the globe to fully understand the health implications of mercury exposure.

Multiple low-level exposures: Hg interactions with co-occurring neurotoxic substances in early life

All chemical forms of Hg can affect neurodevelopment; however, low levels of organic Hg (methylmercury-MeHg and ethylmercury-EtHg in Thimerosal-containing vaccines, hereafter 'TCV') exposures during early life (pregnancy and lactation) co-occur with other environmental neurotoxic substances. These neurotoxicants may act in parallel, synergistically, or antagonistically to Hg. Nevertheless, the risks of neurotoxicity associated with multiple neuro-toxicants depend on type, time, combinations of exposure, and environmental and/or genetic-associated factors. Neurological developmental disorders, delays in cognition and behavioral outcomes associated with multiple exposures (which include Hg) may show transient or lasting outcomes depending on constitutional and/or environmental factors that can interact to neutralize, aggravate or attenuate these effects; often these studies are challenging to interpret. During pregnancy and lactation, fish-MeHg exposure is frequently confounded with the opposing effects of neuroactive nutrients (in fish) that lead to positive, negative, or no effects on neurobehavioral tests. In infancy, exposures to acute binary mixtures (TCV- EtHg and Al-adjuvants in infant immunizations) are associated with increased risks of tics and other developmental disorders. Despite the certitude that promulgates single environmental neurotoxicants, empirical comparisons of combined exposures indicate that Hg-related outcome is uneven. Hg in combination with other neurotoxic mixtures may elevate risks of neurotoxicity, but these risks arise in circumstances that are not yet predictable. Therefore, to achieve the goals of the Minamata treaty and to safeguard the health of children, low levels of mercury exposure (in any chemical form) needs to be further reduced whether the source is environmental (air- and food-borne) or iatrogenic (pediatric TCVs).

Heterogeneity of Multimedia Exposures to Neurotoxic Elements (Al, As, Cd, Pb, Mn, and Hg) in Breastfed Infants from Porto Velho, Brazil

Infant exposure to neurotoxic elements is a public health issue that needs monitoring with regard to breast milk composition. We studied six neurotoxic elements in breast milk samples at different stages of lactation in mothers from Porto Velho, Brazil. We used a flow-injection mercury system (FIMS) to determine total Hg concentrations and an inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the concentrations of Al, As, Cd, Pb, and Mn in 106 donors of a human milk bank. Association rules analyses were applied to determine the pattern of binary and ternary mixtures of the measured exposants. The metal concentration was mostly below the limit of detection (LOD) for Cd (99%), Pb (84%), and Hg (72%), and it was above the LOD for As (53%), Mn (60%), and Al (82%), respectively. Median concentrations (dry weight) of Al, As, Hg, Mn, and Pb were 1.81 μg/g, 13.8 ng/g, 7.1 ng/g, 51.1 ng/g, and 0.43 μg/g, respectively. Al is singly the most frequent element to which infants are exposed. Occurring binary combination (> LOD) was 56% for Al-Mn, 41% for Al-As, 22% for Al-Hg, and 13% for Al-Pb. In 100% of neonates, exposure to Al-ethylmercury (EtHg) occurred through immunization with thimerosal-containing vaccines (TCV). Association rules analysis revealed that Al was present in all of the multilevel combinations and hierarchical levels and that it showed a strong link with other neurotoxic elements (especially with Mn, As, and Hg). (a) Nursing infants are exposed to combinations of neurotoxicants by different routes, dosages, and at different stages of development; (b) In breastfed infants, the binary exposures to Al and total Hg can occur through breast milk and additionally through TCV (EtHg and Al);