Mercury, lead and cadmium in human milk in relation to diet, lifestyle habits and sociodemographic variables in Madrid (Spain)

Assessment of cadmium levels in human breast milk and the affecting factors: A systematic review, 1971-2014

BACKGROUND

This is a first systematic review summarizing 43 years of research from 36 countries for the assessment of cadmium in breast milk, a suitable matrix in human biomonitoring.

OBJECTIVES

To report from the published literature the levels of cadmium in breast milk, and the affecting factors causing increase in cadmium concentrations. In addition, to gather several quantitative data that might be useful to evaluate the international degrees of maternal and infant exposure.

METHODS

We reviewed the literature published between 1971 and 2014, available on Pubmed, Science Direct, and Google Scholar, reporting quantitative data about cadmium levels in human breast milk. Information about the aim of the study, name of the country, period of collection of samples, size of samples, sampling method, time of lactation, mother's age, area of residence, cadmium concentration, and other data were extracted.

RESULTS

Sixty-seven studies were selected and included in this systematic review. Some concentrations greatly exceed the limit set by the World Health Organization (WHO); however, about 50% of the studies had less than 1 µg/L cadmium concentration (recommended by the WHO); as well as many factors have shown their implication in breast milk contamination.

CONCLUSIONS

Breast milk is a pathway of maternal excretion of cadmium. It is also a biological indicator of the degree of environmental pollution and cadmium exposure of the lactating woman and the nourished infant. Therefore, preventive measures and continuous monitoring are necessary.

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

Background

Although breastfeeding of infants is recommended globally, the fact that maternal toxic metal stores are mobilised into breast milk implies infants, whose mothers live and work in mining communities, are at risk of multiple exposure to mining related toxic metals, such as Lead (Pb), Mercury (Hg), Cadmium (Cd) and Arsenic (As), through breast milk intake, in addition to in utero exposure.

Method

A total of 114 mother-baby pairs, recruited from two community hospitals servicing mining communities in two different regions in Ghana (57 each), were involved in this study. When the babies were 3 months old, the amount of breast milk intake, concentrations of selected toxic metals in the breast milk and therefore the amount of toxic metals exposure through breast milk were determined. The study also, determined the amount of these toxic metals in the hair and urine of each mother-baby pair at 3 months postpartum.

Results

Based on the amounts of milk intake and non-milk oral intakes (geometric mean of 0.701 (95% CL 0.59–0.81) Kg/day and median of 0.22 Kg/day respectively), 90% of the babies were determined to have been exclusively breastfed. The amounts of most of the toxic metals in breast milk were higher than the WHO set limits and for 46.4%, 33.3% and 4.4% of the babies, their intake of As, Hg and Pb respectively were above the WHO provisional tolerable daily intake (PTDI) values.

Conclusion

An appreciable proportion of babies living within the communities served by the Mangoasi Community Hospital in the Obuasi Municipality of the Ashanti Region and the Dompime Health Centre in the Tarkwa Municipality of the Western Region were exposed to Hg, As and Pb through breast milk in excess of what they should and these may have health implication for the infants and therefore calls for interventions.

Blood cadmium concentrations and environmental exposure sources in newcomer South and East Asian women in the Greater Toronto Area, Canada

BACKGROUND

Immigrant women are often identified as being particularly vulnerable to environmental exposures and health effects. The availability of biomonitoring data on newcomers is limited, thus, presenting a challenge to public health practitioners in the identification of priorities for intervention.

OBJECTIVES

In fulfillment of data needs, the purpose of this study was to characterize blood concentrations of cadmium (Cd) among newcomer women of reproductive age (19-45 years of age) living in the Greater Toronto Area (GTA), Canada and to assess potential sources of environmental exposures.

METHODS

A community-based model, engaging peer researchers from the communities of interest, was used for recruitment and follow-up purposes. Blood samples were taken from a total of 211 newcomer women from South and East Asia, representing primary, regional origins of immigrants to the GTA, and environmental exposure sources were assessed via telephone survey. Metal concentrations were measured in blood samples (diluted with 0.5% (v/v) ammonium hydroxide and 0.1% (v/v) octylphenol ethoxylate) using a quadrupole ICP-MS. Survey questions addressed a wide range of environmental exposure sources, including dietary and smoking patterns and use of nutritional supplements, herbal products and cosmetics.

RESULTS

A geometric mean (GM) blood Cd concentration of 0.39µg/L (SD:±2.07µg/L) was determined for study participants (min/max: <0.045µg/L (LOD)/2.36µg/L). Several variables including low educational attainment (Relative Ratio (RR) (adjusted)=1.50; 95% CI 1.17-1.91), milk consumption (RR (adjusted)=0.86; 95% CI 0.76-0.97), and use of zinc supplements (RR (adjusted)=0.76; 95% CI 0.64-0.95) were observed to be significantly associated with blood Cd concentrations in the adjusted regression model. The variable domains socioeconomic status (R²_adj=0.11) and country of origin (R²_adj=0.236) were the strongest predictors of blood Cd.

CONCLUSION

Blood Cd concentrations fell below those generally considered to be of human health concern. However, negative health effects cannot be entirely excluded, especially for those that fall in the upper percentile range of the distribution, given the mounting evidence for negative health outcomes at low environmental exposure concentrations.

Exposure to multiple chemicals in a cohort of reproductive-aged Danish women

BACKGROUND

Current exposure assessment research does not sufficiently address multi-pollutant exposure and their correlations in human media. Understanding the extent of chemical exposure in reproductive-aged women is of particular concern due to the potential for in utero exposure and fetal susceptibility.

OBJECTIVES

The objectives of this study were to characterize concentrations of chemical biomarkers during preconception and examine correlations between and within chemical classes.

METHODS

We examined concentrations of 135 biomarkers from 16 chemical classes in blood and urine from 73 women aged 18-40 enrolled in Snart Foraeldre/Milieu, a prospective cohort study of pregnancy planners in Denmark (2011-2014). We compared biomarker concentrations with United States similarly-aged, non-pregnant women who participated in the National Health and Nutrition Environmental Survey (NHANES) and with other international biomonitoring studies. We performed principal component analysis to examine biomarker correlations.

RESULTS

The mean number of biomarkers detected in the population was 92 (range: 60-108). The most commonly detected chemical classes were phthalates, metals, phytoestrogens and polycyclic aromatic hydrocarbons. Except blood mercury, urinary barium and enterolactone, geometric means were higher in women from NHANES. Chemical classes measured in urine generally did not load on a single component, suggesting high between-class correlation among urinary biomarkers, while there is high within-class correlation for biomarkers measured in serum and blood.

CONCLUSIONS

We identified ubiquitous exposure to multiple chemical classes in reproductive-aged Danish women, supporting the need for more research on chemical mixtures during preconception and early pregnancy. Inter- and intra-class correlation between measured biomarkers may reflect common exposure sources, specific lifestyle factors or shared metabolism pathways.

Contaminación por mercurio de leche materna de madres lactantes de municipios de Antioquia con explotación minera de oro

Introducción. La leche materna es esencial para el desarrollo del ser humano, pero puede contener sustancias tóxicas provenientes de la contaminación ambiental, especialmente en las áreas mineras.Objetivo. Determinar la prevalencia de la contaminación con mercurio de la leche materna de mujeres lactantes residentes en los municipios con explotación minera de oro.Materiales y métodos. Se hizo un estudio transversal de 150 madres lactantes de cuatro municipios mineros de Antioquia (El Bagre, Segovia, Remedios y Zaragoza), a quienes se les hizo una encuesta sobre factores sociodemográficos, ocupacionales y ambientales relacionados con el mercurio, y se les tomaron muestras de leche materna, de orina y de cabello. Se calculó el promedio de la concentración de mercurio y las prevalencias municipales de contaminación.Resultados. El promedio de la concentración de mercurio en la leche materna fue de 2,5 (± desviación estándar 9,2) μg/L. La prevalencia de muestras de leche materna con niveles altos de mercurio fue de 11,7 %.Conclusión. En este estudio se evidencia un grave problema en las regiones mineras auríferas de Antioquia por el efecto de la contaminación con mercurio en sectores de la población más vulnerable.

Prevalence and associated demographic characteristics of exposure to multiple metals and their species in human populations: The United States NHANES, 2007-2012

Lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) are among the top 10 pollutants of global health concern. Studies have shown that exposures to these metals produce severe adverse effects. However, the mechanisms underlying these effects, particularly joint toxicities, are poorly understood in humans. The objective of this investigation was to identify and characterize prevalent combinations of these metals and their species in the U.S. NHANES population to provide background data for future studies of potential metal interactions. Exposure was defined as urine or blood levels ≥ medians of the NHANES 2007-2012 participants ≥6 years (n = 7408). Adjusted-odds ratios (adj-OR) and 95% confidence intervals were determined for covariates (age, gender, and race/ethnicity, cotinine and body mass index). Species-specific analysis was also conducted for As and Hg including iAs (urinary arsenous acid and/or arsenic acid), met-iAs (urinary monomethylarsonic acid and/or dimethylarsinic acid), and oHg (blood methyl-mercury and/or ethyl-mercury). For combinations of As and Hg species, age- and gender-specific prevalence was determined among NHANES 2011-2012 participants (n = 2342). Data showed that approximately 49.3% of the population contained a combination of three or more metals. The most prevalent unique specific combinations were Pb/Cd/Hg/As, Pb/Cd/Hg, and Pb/Cd. Age was consistently associated with these combinations: adj-ORs ranged from 10.9 (Pb/Cd) to 11.2 (Pb/Cd/Hg/As). Race/ethnicity was significant for Pb/Cd/Hg/As. Among women of reproductive age, frequency of oHg/iAs/met-iAS and oHg/met-iAs was 22.9 and 40.3%, respectively. These findings may help prioritize efforts to assess joint toxicities and their impact on public health.

Assessment of Aflatoxin M1 and Heavy Metal Levels in Mothers Breast Milk in Famagusta, Cyprus

Breast milk contributes towards optimal nutrition for infants. However, studies showed that it can also contain different toxins and heavy metals, which reduce its health benefits. The aim of this study is to determine the level of contaminants such as aflatoxin M1 (AFM1), Pb, Cd, As, and Hg in breast milk samples from Famagusta, Cyprus. Correlations between moldy food consumption, smoking habits of the mothers, and contaminant levels in breast milk were also investigated. Breast milk samples from 50 lactating mothers in rural and urban areas of Famagusta District were analyzed for AFM1 by ELISA. Eighty percent of them were found to be contaminated with AFM1 with the mean measurement of 7.84 ± 1.72 ng/l. Socio-demographic status, moldy food consumption habits, and smoking status do not have any effect on the AFM1 levels observed in breast milk. Heavy metal levels in breast milk were examined by inductively coupled plasma mass spectrometry, and the mean measurements were1.19 ± 1.53 ppm for Pb, 0.73 ± 0.58 ppm for As, 0 ± 0.20 ppm for Hg, and 0.45 ± 0.23 ppm for Cd. This study indicates that the levels of these contaminants in breast milk samples obtained in Famagusta District are well within the acceptable levels. However, the presence of AFM1 and heavy metals still may pose risks for infant health.

Use of human milk in the assessment of toxic metal exposure and essential element status in breastfeeding women and their infants in coastal Croatia

Pregnant and lactating women and infants are vulnerable population groups for adverse effects of toxic metals due to their high nutritional needs and the resultant increased gastrointestinal absorption of both, essential and toxic elements. Although breastfeeding is recommended for infants worldwide, as human milk is the best source of nutrients and other required bioactive factors, it is also a pathway of maternal excretion of toxic substances including toxic metals and thus a source of infant exposure. The aim of this research was to assess health risks in breastfeeding women in the coastal area of the Republic of Croatia and their infants (N=107) due to maternal exposure to Cd and Pb via cigarette smoking, and Hg via seafood and dental amalgam fillings, and their interaction with essential elements. Biological markers of exposure were the concentrations of main toxic metals Pb, Cd and Hg in maternal blood and three types of breast milk throughout lactation stages. Biological markers of effects were the levels of essential elements Ca, Fe, Cu, Zn and Se in maternal serum and breast milk. With regard to cigarette smoking as a source of exposure to Cd and Pb, there were effects of smoking on Cd concentration in blood and correlations between the smoking index and Cd concentrations in maternal blood (ρ=0.593; P<0.001) and mature milk (ρ=0.271; P=0.011) and Pb concentration in transitional milk (ρ=0.280; P=0.042). Regarding fish, we found correlations between weekly consumption frequency and total Hg concentrations in maternal blood (ρ=0.292; P=0.003) and mature milk (ρ=0.303; P=0.003). The number of dental amalgam fillings correlated with total Hg concentrations in colostrum (ρ=0.489; P=0.005) and transitional milk (ρ=0.309; P=0.018). As for the essential element status, only Se levels in maternal serum decreased by 10% in persons who continued smoking during pregnancy compared to non-smokers. In conclusion, the levels of main toxic metals Cd, Pb and Hg and essential elements Ca, Fe, Cu, Zn and Se in maternal blood and three types of breast milk samples in the studied area of coastal Croatia showed no risk of disrupted essential element levels with regard of toxic metal exposure in both breastfeeding women and their infants.

Tobacco smoking and breastfeeding: Effect on the lactation process, breast milk composition and infant development. A critical review

Approximately 10% of women report smoking during pregnancy. The number of breastfeeding women who relapse back to smoking is even greater. Smoking may cause adverse changes to the milk's composition by not only reducing its protective properties, but also by affecting the infant's health. The pathophysiological mechanisms underlying these adverse effects are not entirely known. This article is a review of previous reports about the effects of smoking on the lactation process, breast milk composition and infant development. A systematic search for English language articles published until 2015 was made, using a MEDLINE data. The key search terms were "smoking and breastfeeding", "smoking and lactation", "smoking and milk composition", "nicotine and breast milk". Studies have shown that nicotine levels in breast milk of women who smoke are three times higher than those in the plasma levels. Breast milk volume is reduced and the duration of lactation period is shorter. Smoking causes adverse changes to the milk's composition by not only reducing its protective properties, but also affecting infants' response to breastfeeding and to breast milk.

The Nickel Concentration in Breast Milk during the First Month of Lactation in Yazd, Center of Iran

Breastfeeding plays an important role in the growth and development of breastfed infants, especially in the first 6 months of their lives. The present study was conducted to determine the nickel concentrations in breast milk of lactating women in Yazd, Iran. One hundred fifty volunteers were selected among nursing mothers referring to health centers in Yazd. In the first month of lactation, milk samples were collected three times, on days 3 to 5 (first), 16 (Second), and 30 (third) after delivery. Nickel concentration of the samples was measured by atomic absorption spectrophotometer. Demographic variables were collected through a questionnaire which was completed by mothers. The mean age of the study group was 27.40 ± 4.66 years. The mean nickel concentrations in breast milk at the first, second, and third samples were 47.3 ± 7.40, 49.9 ± 8.05, and 54.8 ± 7.38 μg/l, respectively. The concentration of nickel in the breast milk of more than 86 % of mothers was higher than the permissible range for it. There was no significant relationship between the mean value of nickel in breast milk and education, age, and job of mothers. High level of nickel in breast milk may be attributed to consumed food and drinking water containing nickel. Monitoring the nickel level in breast milk regularly is recommended.

Arsenic, lead, mercury and cadmium: Toxicity, levels in breast milk and the risks for breastfed infants

Metals are ubiquitous in nature, being found in all environmental compartments, and have a variety of applications in human activities. Metals are transferred by maternal blood to the fetus via the placenta, and exposure continues throughout life. For the general population, exposure comes mainly from water and food consumption, including breast milk. In this paper, we reviewed studies on the toxicity of arsenic, lead, mercury and cadmium, the toxic metals of most concern to human health, focusing on the potential risks to newborns and infants. A total of 75 studies published since 2000 reporting the levels of these metals in breast milk were reviewed. Lead was the metal most investigated in breast milk (43 studies), and for which the highest levels were reported (up to 1515µg/L). Arsenic was the least investigated (18 studies), with higher levels reported for breast milk (up to 149µg/L) collected in regions with high arsenic concentrations in water (>10µg/L). Data from 34 studies on mercury showed that levels in breast milk were generally higher in populations with high fish consumption, where it may be present mainly as MeHg. Cadmium levels in breast milk were the lowest, with means <2µg/L in most of the 29 studies reviewed. Results of risk assessments indicated that the intake of arsenic, lead and mercury by infants through breastfeeding can be considered a health concern in most regions of the world. Although the potential risks to infants are mostly outweighed by the benefits of breast milk consumption, it is essential that contaminants be continuously monitored, especially in the most critical regions, and that measures be implemented by health authorities to reduce exposure of newborns and infants to these metals, and thus avoid unnecessary health risks.

Cadmium Concentration in Mother's Blood, Milk, and Newborn's Blood and Its Correlation with Fatty Acids, Anthropometric Characteristics, and Mother's Smoking Status

The aim of this study was to determine cadmium concentration in mothers' blood, milk, and newborns' blood from Szczecin (Poland) as a result of environmental cadmium exposure and evaluate the correlation (1) between cadmium levels in analyzed matrices, (2) between cadmium and fatty acids in those matrices, and (3) between cadmium and some selected personal variables, such as anthropometric characteristics, mothers' smoking status, and fruit and fish consumption by mothers. The concentration of cadmium in whole blood and milk of mothers and in the umbilical cord blood of newborns was determined by atomic absorption spectrometry with graphite furnace atomization and Zeeman correction. The fatty acid concentrations were determined by gas chromatography in our previous study. The mean concentrations of cadmium in maternal blood, newborn's blood, and breast milk were 0.61 ± 0.62 μg/L, 0.05 ± 0.04 μg/L, and 0.11 ± 0.07 μg/L, respectively, and differed significantly between analyzed matrices. Cadmium concentrations in the umbilical cord blood were 15 % (range 0-83 %) of the concentration in maternal blood, whereas cadmium concentrations in breast milk constituted 35 % (range 3-142 %) of the concentration in mothers' blood. No correlation was found between cadmium levels in three analyzed matrices. The correlation analysis revealed significant low positive correlation between maternal blood cadmium concentrations and concentrations of elaidic, oleic, and cis-vaccenic acids in mothers' milk (correlation coefficients 0.30, 0.32, and 0.31, respectively). Mothers' blood cadmium correlated with mothers' age (r = -0.26, p = 0.03), maternal smoking before pregnancy (r = 0.55, p < 0.000), maternal smoking during pregnancy (r = 0.58, p < 0.000), and fruit consumption by mothers after delivery (r = -0.44, p = 0.003). Mothers' height was the only variable that correlated significantly with breast milk cadmium levels. Newborns' blood cadmium concentrations correlated significantly with mothers' height (r = 0.28, p = 0.02), newborns' birth weight (r = 0.26, p = 0.03), maternal smoking during pregnancy (r = 0.24, p = 0.048), and fish consumption by mothers after delivery (r = 0.37, p = 0.02). The concentrations of cadmium in Polish mother-newborn pairs are among the lowest in Europe and within the norms established by different institutions. The results of our study confirm the existence of effective partial barriers (such as the placenta and mammary gland) restricting cadmium passage from mother to newborn. The significant positive correlations between maternal blood Cd and concentrations of oleic, elaidic, and cis-vaccenic acids in breast milk might suggest the increased cadmium toxicity to infant, taking into consideration even low cadmium passage to milk. Maternal smoking during pregnancy increases both maternal and newborn's blood cadmium level. Promotion of nonsmoking among pregnant women could substantially reduce prenatal and neonatal exposure to cadmium. Moreover, the results of our study point to the need of establishing complex biomonitoring of cadmium in mother-infant pairs in order to better protect children from this toxic and carcinogenic metal exposure.

Factors affecting lactoferrin concentration in human milk: how much do we know?

Lactoferrin (LF) is a breast milk glycoprotein with antimicrobial and anti-inflammatory effects. Its beneficial properties in infants, especially in those born preterm, are currently being studied in clinical trials. However, the maternal and nursing infant factors that may affect LF concentration in breast milk are still not clear. We conducted a systematic review to investigate the factors that may affect the concentration of LF in breast milk. We used a 2-step approach to identify the eligible studies according to inclusion/exclusion criteria, and to determine which studies would be considered. We included 70 qualified articles from 29 countries with publication dates ranging from 1976 to 2015. We described the correlation between LF concentration in breast milk and lactation stage; 10 maternal factors, such as race, parity, among others; and 2 infant factors: infections and prematurity. Colostrum has the highest LF levels, but they decrease with days postpartum. No other factor has been consistently associated with LF concentration. A major limitation of the majority of the published studies is the small sample size and the different methods used to measure LF concentration. Therefore, there is a need for large, multicenter studies with standardized study design, sample collection, and LF measurement methods to identify clinically significant factors associated with LF expression in breast milk, which will help promote exclusive breastfeeding in preterm infants.

Breast Milk Lead Levels in 3 Major Regions of the West Bank of Palestine

BACKGROUND

Lead is a neurotoxic pollutant that is ubiquitously spread in our environment. Breast milk contaminated with lead poses a potential risk of exposing a recipient infant to lead.

OBJECTIVES

The primary aims of this study were to evaluate the breast milk lead levels (BMLLs) in breastfeeding mothers in 3 major regions of the West Bank of Palestine and to investigate the effects of some sociodemographic variables on the BMLLs.

METHODS

Breast milk samples were collected from 89 breastfeeding mothers from the Nablus, Ramallah, and Jerusalem regions and analyzed for their BMLLs using graphite furnace atomic absorption spectrophotometry. Breastfeeding mothers were interviewed and responded to a sociodemographic questionnaire.

RESULTS

The median BMLL was 4.0 µg/L, ranging from 2.0 to 12.0 µg/L. Breast milk lead levels in 19.1% of the samples analyzed were higher than the World Health Organization's safety limits of 2.0 to 5.0 µg/L for an occupationally unexposed population. Breast milk lead levels were significantly higher in breast milk of mothers who lived in cities and refugee camps (P < .01), had lower monthly household income levels (P < .05), lived close to paint shops (P < .05), lived in houses with peeling or chipping paint (P < .05), used eye kohl (P < .01), and worked in agriculture for a duration longer than 3 years (P < .01).

CONCLUSION

Breast milk lead levels were higher than the safety limits for occupationally unexposed populations. Authorities need to implement measures to eliminate or reduce lead exposure, especially in refugee camps and cities. Marketed eye kohl preparations should be tested for their lead contents.

The extent of mercury (Hg) exposure among Saudi mothers and their respective infants

A total of 1016 healthy Saudi mothers and their respective infants (aged 3-12 months) were recruited from 57 Primary Health Care Centers (PHCCs) in Riyadh, Saudi Arabia, to evaluate the extent of mercury (Hg) exposure and predict its sources in the healthy Saudi population. Total Hg levels were measured in maternal urine, breast milk, blood, and hair and in the infants' urine and hair. Only 1.9% of the mothers had urinary Hg (UHg)>10 μg/l, the limit for asymptomatic adults recommended by the World Health Organization, but the median (0.99 μg/l) was higher than in other countries. Also, 49.3% of the mothers had UHg>1 μg/l, the German reference value for adults. Median infant UHg was 0.729 μg/l, and 77 and 93 % of the infants had levels higher than 0.4 and 0.1 μg/l, the reference values of the Centers for Disease Control and Prevention and for Germany, respectively. The median Hg level in breast milk was 0.884 μg/l. Even though 43.2% of the milk samples were above the background level for Hg in human milk (1 μg/l), our results were lower than those reported from other countries. Median maternal total Hg in blood was 0.637 μg/l, and only 0.4 and 6.9% of samples were higher than the Hg reference levels of 5.8 μg/l of the Environmental Protection Agency (EPA) and of 2 μg/l for Germany, respectively. Total Hg levels in hair (HHg) varied widely among mothers and infants, but only 3.9% of the mothers and 2.8% of the infants had HHg>1 μg/g (the EPA reference level). Median HHg values were 0.117 μg/g dry weight in mothers and 0.1 μg/g dry weight in infants; both were lower than in other countries. The Hg levels in mothers and their respective infants were relatively low, but our results were consistent with other studies indicating that dental amalgam fillings and fish consumption were the main predictors of maternal Hg exposure. Among the several biomarkers of Hg exposure, Hg levels in maternal hair and urine were the strongest predictors of infant exposure. The lack of an association between Hg in breast milk and Hg in infant urine and hair suggested that the infants were exposed to Hg predominately during pregnancy rather than during breastfeeding. We expect that our data can serve as a baseline for further biomonitoring and follow-up studies, particularly of the long-term impact of Hg on childhood neurodevelopment.

Methylmercury in the breast milk of Japanese mothers and lactational exposure of their infants

The human fetus is known to be exposed to methylmercury (MeHg), but little is known about the risk of infant exposure via breast milk. To evaluate the lactational exposure to MeHg via breast milk in Japanese infants, the levels of total mercury (THg) and MeHg were determined in breast milk and maternal blood using samples from a birth cohort study at the Tohoku Study of Child Development. Maternal blood and breast milk were collected one day postpartum and one month after delivery, respectively. The median THg (and MeHg) concentrations in maternal RBCs, plasma and breast milk were 17.8 ng g(-1) (17.8 ng g(-1)), 1.51 ng g(-1) (1.33 ng g(-1)) and 0.81 ng g(-1) (0.45 ng g(-1)), respectively (n=27). The median percentage of MeHg in THg was 54% in breast milk. Breast milk contained substantial amounts of MeHg, which was strongly associated with the internal accumulation of MeHg and the lipid content of the milk (r=0.684). The range of lipid contents in milk varied widely from 0.50 to 6.60 g/100 g of milk, with a median of 3.60 g/100 g. The median (range) weekly average intake of MeHg via breast milk was estimated to be 0.63 μg kg(-1) (0.08-1.68 μg kg(-1)) BW/week. Because the MeHg and lipid contents in milk substantially fluctuate, an investigation of the variations of MeHg and lipid content in breast milk may be required for a more precise risk assessment.

Concentration profiles of metals in breast milk, drinking water, and soil: relationship between matrices

The concentrations of Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sn, and Zn were determined in breast milk of women living in Conceição das Alagoas, Minas Gerais, Brazil. The potential relationships between metal levels in samples of breast milk, drinking water, and soils collected in the study area were also established. Metal levels in breast milk, except Cr, were lower in comparison to WHO reference concentrations. Zinc was the predominant element in breast milk and drinking water samples, with a median level of 46.2 and 82.2 μg · L(-1), respectively. Soils presented a different pattern of metal concentrations with respect to those found in breast milk and drinking water, Chromium showed the highest median levels (148 mg · kg(-1)), while a certain predominance of Zn and Cu was also observed (47.0 and 43.0 mg · kg(-1), respectively). Similar profiles were observed when comparing metal concentrations in drinking water and breast milk (chi-square χ(2) = 14.36; p < 0.05). In contrast, breast milk-soil and drinking water-soil metal concentration profiles showed significant differences (χ(2) = 635.05 and χ(2) = 721.78, respectively; p < 0.05). These results indicate that drinking water is an important exposure pathway for metals to newborns through breast milk. Further studies should be aimed at assessing the body burdens of metals in that population and at evaluating the potential relationships in the concentrations in biological and environmental matrices as well as at estimating the contribution of dietary intake of metals. In addition, the presence of other chemical pollutants in breast milk should be also studied in order to assess the combined newborn exposure to other contaminants.

Mercury (Hg) exposure in breast-fed infants and their mothers and the evidence of oxidative stress

The objective of this work was to assess exposure to mercury (Hg) and its induction of oxidative stress in 155 healthy lactating Saudi mothers and their infants. Samples of breast milk and blood were collected from the mothers, while urine was taken from both infants and mothers. Both urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) were measured in mothers and infants as biomarkers of oxidative stress. The mean concentration of Hg in breast milk was 1.19 μg/L (range 0.012-6.44 μg/L) with only one mother having Hg >4 μg/L, the upper limit established by the US Agency for Toxic Substance and Disease Registry. However, 57.4 % had Hg ≥1 μg/L, the background level for Hg in human milk. The mean urinary Hg corrected for creatinine (Hg-C) in mothers and infants was 1.47 and 7.90 μg/g creatinine, respectively, with a significant correlation between the two (p < 0.001). Urinary Hg levels over 5 μg/g creatinine (the background level in an unexposed population) were found in 3.3 % of mothers and 50.1 % of infants. None of the mothers had total blood Hg above the US Environmental Protection Agency's maximum reference dose of 5.8 μg/L. No correlation was noted between urinary Hg in infants and Hg in breast milk (p > 0.05). Hg in breast milk, though, was associated with Hg in blood (p < 0.001), suggesting the efficient transfer of Hg from blood to milk. Hg in the breast milk of mothers and in the urine of infants affected the excretion of urinary MDA and 8-OHdG, respectively, in a dose-related manner. These findings reveal for the first time lactational exposure to Hg-induced oxidative stress in breast-fed infants, which may play a role in pathogenesis, particularly during neurodevelopment. This will also contribute to the debate over the benefits of breast milk versus the adverse effects of exposure to pollutants. Nevertheless, breastfeeding should not be discouraged, but efforts should be made to identify and eliminate the source of Hg exposure in the population.

Cytokine profile of mature milk from smoking and nonsmoking mothers

We verified whether smoking during lactation influences breast milk cytokine (interleukin [IL]-1α, IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-α) levels 30 to 32 days after delivery. The study group comprised 24 postpartum women who declared smoking >5 cigarettes per day. The control group included 45 nonsmoking postpartum women. Compared with nonsmoking women, smokers were characterized by significantly higher breast milk concentrations of IL-1α (P = 0.04), whereas no significant intergroup differences were observed in terms of remaining analyzed cytokines. Moreover, both groups were characterized by a similar fraction of women with detectable cytokine levels.

Lead, mercury, and cadmium in blood and their relation to diet among Swedish adults

The aim of the present study was to examine the body burden of lead (Pb), mercury (Hg), and cadmium (Cd) in blood among Swedish adults and the association between blood levels, diet and other lifestyle factors. The study was based on a subgroup (n=273) of the national survey Riksmaten 2010-2011 (4-day food records and questionnaire). Lead, Hg, and Cd were measured in whole blood, and Cd additionally in urine, by mass or fluorescence spectrometry methods. The median values (5-95th percentiles) of the metals in blood were as follows; Pb: 13.4 (5.8-28.6) μg/L, Hg: 1.13 (0.31-3.45) μg/L, and Cd: 0.19 (0.09-1.08) μg/L. All three metals increased with increasing age. Lead levels in blood were positively associated with intakes of game and alcohol, Hg was related to fish intake, and blood Cd related to smoking and low iron stores and to a low meat intake. Body burdens of the studied metals were generally below health based reference values, but several individuals had blood Pb levels above the reference point for possible nephrotoxic and developmental neurotoxic effects. As health effects cannot be excluded, individuals with high Pb exposure should aim at decreasing their body burden, both from food and from other exposure routes.

Total and methyl-mercury in hair and milk of mothers living in the city of Porto Velho and in villages along the Rio Madeira, Amazon, Brazil

High fish consumption and extended breastfeeding are hallmarks of traditional lifestyle in Western Amazonia. We studied sources of mercury exposure, fish-methylmercury (meHg) and dental-amalgam filling, in 75 urban and 82 rural lactating mothers. Total mercury was determined in all samples while meHg concentrations were determined in subsamples of milk (45) and hair (27) of urban mothers living in Porto Velho (PV) and in hair (46) and milk (37) of mothers living in traditional communities (TC) of the Rio Madeira. The TC mothers showed significantly higher median hair-Hg concentrations (8.2μgg(-1)) than PV mothers (1.3μgg(-1)). Median total Hg in milk of PV mothers (0.36ngg(-1)) was significantly lower (p=0.0000) than that found in milk of TC mothers (2.30ngg(-1)). The median meHg concentrations in milk of TC mothers were also significantly higher (1.0ngg(-1)) than in milk of PV mothers (0.07ngg(-1)). For urban mothers with low fish consumption rates (and relatively higher dental amalgam fillings) the proportion of inorganic Hg in milk was higher (85%) than in TC (62%). In TC mothers 51% of breast milk Hg concentrations were above 2ngg(-1) (world median concentrations), contrasting with 8% in PV mothers. Despite this, there was no significant correlation between total Hg concentrations in milk and either amalgam filling or daily fish consumption. Socioeconomic changes occurring in Western Amazonia are causing changes in fish-eating habits of urban mothers. However, traditional lifestyle and attendant high fish consumption in riverine populations can still impact total Hg and methylmercury concentrations in mothers' milk and hair.

Mercury concentration in breast milk and infant exposure assessment during the first 90 days of lactation in a midwestern region of Brazil

Breast milk samples collected from 18 nursing mothers between the 15th and 90th day of lactation were digested in nitric acid in a microwave, and total mercury (THg) levels were quantified by atomic fluorescence spectrometry. Participants responded to a 24-h dietary recall questionnaire on the 74th and 76th day of lactation and to a Food Frequency Questionnaire querying the frequency of fish intake over the last 90 days. Usual intake was estimated using the PC-SIDE software package. A meal of fish was offered on the 75th day of lactation. Mothers' individual mean THg levels ranged from <0.76 to 22.7 ng/mL during the period, and the mean level for all samples (n = 142) was 6.47 ±6.04 ng/mL. The multilevel mixed linear model used showed high heterogeneity of the mercury levels among the mothers, and THg levels did not change significantly over the period under study. However, a significant increase in THg levels was observed after the intervention with the fish meal. Exposure increased for most infants on the 90th day of lactation, with intakes exceeding the THg provisional tolerable weekly intake (PTWI) at least once during the period for 77.8 % of samples. Mothers consumed mostly food from the fat and grain groups, and a significant correlation was detected between consumption of food of these groups and breast milk THg levels (p = 0.006 and 0.007). A significant correlation was also found between vegetable consumption and carbohydrate intake and THg levels in the samples (p = 0.015 and 0.045, respectively). No correlation was found between mothers' daily fish consumption frequency and THg levels. Although this study showed that mercury intake by infants during lactation may exceed the toxicologically safe exposure level (PTWI), we nevertheless believe that the benefits of lactation for both the mother and the infant outweigh the eventual risks that this exposure may represent.

Evidence on the human health effects of low-level methylmercury exposure

BACKGROUND

Methylmercury (MeHg) is a known neuro-toxicant. Emerging evidence indicates it may have adverse effects on the neuro-logic and other body systems at common low levels of exposure. Impacts of MeHg exposure could vary by individual susceptibility or be confounded by beneficial nutrients in fish containing MeHg. Despite its global relevance, synthesis of the available literature on low-level MeHg exposure has been limited.

OBJECTIVES

We undertook a synthesis of the current knowledge on the human health effects of low-level MeHg exposure to provide a basis for future research efforts, risk assessment, and exposure remediation policies worldwide.

DATA SOURCES AND EXTRACTION

We reviewed the published literature for original human epidemiologic research articles that reported a direct biomarker of mercury exposure. To focus on high-quality studies and those specifically on low mercury exposure, we excluded case series, as well as studies of populations with unusually high fish consumption (e.g., the Seychelles), marine mammal consumption (e.g., the Faroe Islands, circumpolar, and other indigenous populations), or consumption of highly contaminated fish (e.g., gold-mining regions in the Amazon).

DATA SYNTHESIS

Recent evidence raises the possibility of effects of low-level MeHg exposure on fetal growth among susceptible subgroups and on infant growth in the first 2 years of life. Low-level effects of MeHg on neuro-logic outcomes may differ by age, sex, and timing of exposure. No clear pattern has been observed for cardio-vascular disease (CVD) risk across populations or for specific CVD end points. For the few studies evaluating immunologic effects associated with MeHg, results have been inconsistent.

CONCLUSIONS

Studies targeted at identifying potential mechanisms of low-level MeHg effects and characterizing individual susceptibility, sexual dimorphism, and non-linearity in dose response would help guide future prevention, policy, and regulatory efforts surrounding MeHg exposure.