Protective role of selenium in the shortening of telomere length in newborns induced by in utero heavy metal exposure.

The effects of toxic heavy metals, such as arsenic (As), cadmium (Cd), and lead (Pb), on telomere length (TL) have been reported previously. Although selenium (Se) is considered as an anti-oxidant which may detoxify the effects, there are no data on whether Se could protect against the TL-shortening effects of heavy metals. Thus, the aim of this study was to evaluate the protective role of Se against heavy metal-induced TL shortening. A birth cohort study was conducted in Myanmar in 2016, including 408 mother-infant pairs. First, pregnant women in the third trimester were interviewed concerning their socioeconomic, and pregnancy and birth characteristics using a pre-validated questionnaire. Maternal spot urine samples were collected after the interview. During the follow-up period (1-3 months), blood samples were collected from the umbilical cord at birth by local health workers. Metal concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). TL was measured by quantitative real-time polymerase chain reaction (PCR). Relative TL was calculated as the ratio of telomere genes to single-copy genes. To evaluate the effect of Se on TL shortening, molar ratios were calculated. Linear regression analyses were performed to examine the associations between heavy metals and TL, individually and after adjustment for Se level. The effects of As, Cd, and Pb exposure on TL were smaller after adjustment for the Se level, especially for Pb (unadjusted ß = -0.10; 95% CI: 0.18, -0.01; adjusted ß = -0.03; 95% CI: 0.13, 0.05). On stratifying the data by Se concentration, there was no significant association between Cd or Pb exposure and TL in the high-Se group. Our study indicated a protective effect of Se against the TL shortening induced by heavy metal exposure, where the effect sizes were smaller after adjusting for the Se level, compared to individual metal exposure.

Arsenic exposure through drinking Water and oxidative stress Status: A cross-sectional study in the Ayeyarwady region, Myanmar.

Arsenic is a well-known toxic heavy metal that is naturally dispersed in groundwater. Whereas arsenic is widely accepted to be involved in oxidative stress damage, little is known about arsenic-induced oxidative damage in relationship to contaminated drinking water as a source. The aim of this study was to determine the association between arsenic exposure through drinking water and oxidative stress status by measuring levels of urinary 8-hydroxydeoxyguanosine (8-OHdG) as a biomarker of oxidative stress damage in a Myanmar population. A questionnaire-based survey and drinking water and urine sampling (n = 198) were performed to assess the association between arsenic exposure and urinary 8-OHdG concentration in the Ayeyarwady Region, Myanmar. Urinary arsenic concentrations were significantly correlated with drinking water arsenic concentrations (Spearman's rho = 0.32, p < 0.001). Multivariate linear regression analysis showed that higher urinary arsenic concentrations were significantly associated with higher 8-OHdG concentrations (coefficient = 0.09, 95% confidence interval, 0.03 - 0.15; p = 0.002). The present study identified that exposure to arsenic through drinking water could induce an increase in the urinary 8-OHdG concentration, reflecting increased oxidative DNA damage. These findings provide evidence that may explain the role of arsenic-induced oxidative stress in the pathophysiology of arsenic-induced diseases including cancers.

Impact of prenatal heavy metal exposure on newborn leucocyte telomere length: A birth-cohort study.

Arsenic, cadmium and lead are toxic environmental contaminants. They were shown to be associated with telomere length (TL) in adults. Although they can cross the placental barrier, the effect of prenatal exposure of these metals on newborn TL is unknown. The aim of this study was to examine whether prenatal exposure to heavy metals has an impact on newborn leucocyte TL. A birth-cohort study was conducted with 409 pregnant women and their newborns in Myanmar. During the first visit, face-to-face interviews were conducted, and maternal spot urine sampling was performed. Cord blood samples were collected during follow-up. Urinary heavy metal concentration was measured by ICP-MS and adjusted for creatinine. Relative TL was measured by quantitative real-time polymerase chain reaction. The extent of prenatal arsenic, cadmium and lead exposure and their associations with newborn leucocyte TL were assessed using multivariate linear regression. The median values of maternal urinary arsenic, cadmium, and lead concentrations were 73.9, 0.9, and 1.8 µg/g creatinine, respectively. Prenatal arsenic and cadmium exposure was significantly associated with newborn TL shortening (lowest vs highest quartile, coefficient = - 0.13, 95% CI: - 0.22, - 0.03, p = 0.002, and coefficient = - 0.17, 95% CI: - 0.27, - 0.07, p = 0.001, respectively), and the associations remained robust after adjusting for confounders. There was no significant association between prenatal lead exposure and newborn TL. The present study identified the effect of arsenic and cadmium exposure on TL shortening, even in utero exposure at a lower concentration.

Prenatal Heavy Metal Exposure and Adverse Birth Outcomes in Myanmar: A Birth-Cohort Study.

Arsenic, cadmium and lead are well-known environmental contaminants, and their toxicity at low concentration is the target of scientific concern. In this study, we aimed to identify the potential effects of prenatal heavy metal exposure on the birth outcomes among the Myanmar population. This study is part of a birth-cohort study conducted with 419 pregnant women in the Ayeyarwady Division, Myanmar. Face-to-face interviews were performed using a questionnaire, and maternal spot urine samples were collected at the third trimester. Birth outcomes were evaluated at delivery during the follow up. The median values of adjusted urinary arsenic, cadmium, selenium and lead concentration were 74.2, 0.9, 22.6 and 1.8 µg/g creatinine, respectively. Multivariable logistic regression revealed that prenatal cadmium exposure (adjusted odds ratio (OR) = 1.10; 95% confidence interval (CI): 1.01-1.21; p = 0.043), gestational age (adjusted OR = 0.83; 95% CI: 0.72-0.95; p = 0.009) and primigravida mothers (adjusted OR = 4.23; 95% CI: 1.31-13.65; p = 0.016) were the predictors of low birth weight. The present study identified that Myanmar mothers were highly exposed to cadmium. Prenatal maternal cadmium exposure was associated with an occurrence of low birth weight.

Soil amendments effects on radiocesium translocation in forest soils.

We conducted an experiment to investigate the potential of phytoremediation by soil amendments in a forest area. To desorb radiocesium (137Cs) from variable charges in the soil, ammonium sulfate (NH4+) and elemental sulfur (S) (which decrease soil pH) were applied to forest soil collected from contaminated area at a rate of 40 and 80 g/m2, respectively. A control condition with no soil treatment was also considered. We defined four groups of aboveground conditions: planted with Quercus serrata, planted with Houttuynia cordata, covered with rice straw as litter, and unplanted/uncovered (control). Cultivation was performed in a greenhouse with a regular water supply for four months. Following elemental sulfur treatment, soil pH values were significantly lower than pH values following ammonium sulfate treatment and no treatment. During cultivation, several plant species germinated from natural seeds. No clear differences in aboveground tissue 137Cs concentrations in planted Q. serrata and H. cordata were observed among the treatments. However, aboveground tissue 137Cs concentration values in the germinated plants following elemental sulfur treatment were higher than the values following the ammonium sulfate treatment and no treatment. Although biomass values for Q. serrata, H. cordata, and germinated plants following elemental sulfur treatment tended to be low, the total 137Cs activities in the aboveground tissue of germinated plants were higher than those following ammonium sulfate treatment and no treatment in rice straw and unplanted conditions. Although no significant differences were observed, 137Cs concentrations in rice straw following ammonium sulfate and elemental sulfur treatments tended to be higher than those in the control case. The results of this study indicate that elemental sulfur lowers the soil pH for a relatively long period and facilitates 137Cs translocation to newly emerged and settled plants or litter, but affects plant growth in large concentrations and/or anaerobic conditions. Combining elemental sulfur application with forest management practices, such as mowing and thinning, could be a suitable method of decontamination of the forest environment.

Radiocesium distribution in sugi (Cryptomeria japonica) in eastern Japan: translocation from needles to pollen.

We assessed the radiocesium contamination of sugi (Cryptomeria japonica) forests in eastern Japan from November 2012 to February 2013, including 80 sites in Fukushima and 35 sites in other regions (Tohoku and Kanto-Koshinetsu), by measuring the (137)Cs concentrations in needles of different ages, male flowers, and pollen. Over a wide geographic area, needles that were present at the time of the Fukushima Dai-ichi Nuclear Power Plant accident contained much higher (137)Cs concentrations than needles that emerged after the accident. This result, together with visual analysis of (137)Cs distribution using autoradiography, indicated that some of the (137)Cs derived from direct fallout remained on the surface of the older needles. Since we also detected (137)Cs in younger needles and male flowers, we concluded that (137)Cs was translocated toward the tips of sugi needles. The (137)Cs concentration in male flowers was higher than and positively correlated with that in the currently growing (2012) needles. Also, a positive relationship was observed between the (137)Cs concentration of male flowers and pollen, and they were found to be nearly identical (137)Cs concentration. These results indicate the occurrence of acropetal translocation of (137)Cs from old needles to young needles, male flowers and pollen. However, the results as related to (137)Cs concentration in the needles of three different ages differed from the results of similar studies conducted more than 4 y after the Chernobyl accident. This suggests that, 2 y after the Fukushima Dai-ichi NPP accident, the distribution of (137)Cs in the sugi forests has not yet reached a steady state.

Retranslocation and localization of nutrient elements in various organs of moso bamboo (Phyllostachys pubescens).

Moso bamboo (Phyllostachys pubescens) is one of the major giant bamboo species growing in Japan, and the invasion of mismanaged bamboo populations into contiguous forests has been a serious problem. To understand expansion mechanisms of the bamboo, it is important to obtain some first insights into the plant's rapid growth from the viewpoints of the nutrient dynamics in bamboo organs. We have investigated seasonal changes in the concentrations of several nutrient elements in leaves of the plants from three P. pubescens forests and the distributions of those elements in both mature (culms, branches, leaves, roots, and rhizomes) and growing organs (shoots and rhizomes). Among all elements analyzed, boron (B) concentrations in leaves showed a specific seasonal variation that was synchronous across all study sites. Boron was detected at high concentrations in the younger parts of growing rhizomes and shoots, and in mature leaves. These results indicate that P. pubescens could actively utilize B for vegetative reproduction by the retranslocation and the local accumulation behaving as mobile B. Silicon (Si) was found in high concentrations in surface parts of culms and in the mature sheaths of growing rhizomes and shoots following those in mature leaves. P. pubescens, a plant known to accumulate Si, accumulated only low levels of Ca and B in the leaves, indicating that it is possible to utilize more Si for cell wall enhancement than Ca or B. In both mature culms and rhizomes, zinc (Zn) was found at much higher concentrations in the nodes with meristematic tissue than those in internodes, indicating that Zn might play a role in promoting culm and rhizome elongation. We suggest that specific and local utilization of B, Si, and Zn in P. pubescens might support the vegetative reproduction and rapid growth.