RESUMO
This study concerns the metabolism of inorganic arsenic (As) in children in three villages in northern Argentina: San Antonio de los Cobres and Taco Pozo, each with about 200 microg As/l in the drinking water, and Rosario de Lerma, with 0.65 microg As/l. Findings show that the concentrations of As in the blood and urine of the children in the two As-rich villages were on average 9 and 380 microg/l, respectively, the highest ever recorded for children. The concentrations were about 10 and 30 times higher for blood and urine, respectively, than in Rosario de Lerma. Total As in urine was only slightly higher than the sum of metabolites of inorganic As (U-Asmet), i.e., inorganic As, methylarsonic acid (MMA), and dimethylarsinic acid (DMA); this shows that inorganic As was the main form of As ingested. In contrast to previous studies on urinary metabolites of inorganic As in various population groups, the children and women in the present study excreted very little MMA. Thus, there seems to be a polymorphism for the enzymes (methyltransferases) involved in the methylation of As. Interestingly, the children had a significantly higher percentage of inorganic As in urine than the women, about 50% versus 32%. Also, the percentage of inorganic As in the children is considerably higher than in previous studies on children (about 13% in the two studies available) and adults (about 15-25%) in other population groups. This may indicate that children are more sensitive to As-induced toxicity than adults, as the methylated metabolites bind less to tissue constituents than inorganic As. In the children, the percentage inorganic arsenic in urine decreased, and the percentage of DMA increased with increasing U-Asmet, indicating an induction of As methylation with increasing exposure.
Assuntos
Arsênio/metabolismo , Proteção da Criança , Exposição Ambiental , Poluentes Químicos da Água/metabolismo , Abastecimento de Água , Adulto , Argentina , Arsênio/efeitos adversos , Arsênio/sangue , Criança , Feminino , Humanos , Masculino , Poluentes Químicos da Água/efeitos adversosRESUMO
OBJECTIVE: To investigate the excretion of arsenic in breast milk of lactating native Andean women living in a village in northwestern Argentina with high concentrations of arsenic in the drinking water (about 200 micrograms/l) and to assess the exposure of children to arsenic during the very first period of life. METHODS: The study included ten lactating women and two nursing babies. Hydride-generation atomic absorption spectrometry (HG-AAS) was used to determine the concentration of arsenic in samples of human milk, drinking water, blood, and urine. RESULTS: The concentrations of arsenic detected in maternal blood (total arsenic) and urine (metabolites of inorganic arsenic) were high, averaging 10 and 320 micrograms/l, respectively. In subjects without known exposure to arsenic the average concentrations found in blood and urine are 1-2 and about 10 micrograms/l, respectively. The metabolites of inorganic arsenic constituted more than 80% of the total arsenic in the urine, which shows that inorganic arsenic was the main form of arsenic ingested. The average concentration of arsenic detected in human milk was 2.3 micrograms/kg fresh weight (range 0.83-7.6 micrograms/kg). Although data on background levels of arsenic in human breast milk are scarce, the present concentrations seem to be slightly elevated. However, considering the high levels of arsenic exposure in the mothers, the total arsenic concentrations measured in human milk were low. In concordance with the low concentrations of arsenic found in the milk, the concentrations of arsenic metabolites measured in the urine of two of the nursing babies were low: 17 and 47 micrograms/l, respectively. CONCLUSIONS: The low concentrations of arsenic detected in the breast milk and urine of the two nursing babies in relation to the high level of maternal exposure to arsenic indicate that inorganic arsenic is not excreted in breast milk to any significant extent. This is a very important reason for long breast-feeding periods.
Assuntos
Arsênio/análise , Exposição Ambiental/análise , Leite Humano/química , Abastecimento de Água/análise , Adolescente , Adulto , Argentina , Arsênio/sangue , Arsênio/urina , Ingestão de Líquidos , Feminino , Humanos , Recém-Nascido , Gravidez , População Rural , Estudos de AmostragemRESUMO
The metabolism of inorganic arsenic (As) in native women in four Andean villages in north-western Argentina with elevated levels of As in the drinking water (2.5, 14, 31, and 200 micrograms/1, respectively) has been investigated. Collected foods contained 9-427 micrograms As/kg wet weight, with the highest concentrations in soup. Total As concentrations in blood were markedly elevated (median 7.6 micrograms/1) only in the village with the highest concentration in the drinking water. Group median concentrations of metabolites of inorganic As (inorganic As, methylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in the urine varied between 14 and 256 micrograms/1. Urinary concentrations of total As were only slightly higher (18-258 micrograms/1), indicating that inorganic As was the main form of As ingested. In contrast to all other populations studied so far, arsenic was excreted in the urine mainly as inorganic As and DMA. There was very little MMA in the urine (overall median 2.2%, range 0.0-11%), which should be compared to 10-20% of the urinary arsenic in all other populations studied. This may indicate the existence of genetic polymorphism in the control of the methyltransferase activity involved in the methylation of As. Furthermore, the percentage of DMA in the urine was significantly higher in the village with 200 micrograms As/1 in the water, indicating an induction of the formation of DMA. Such an effect has not been observed in other studies on human subjects with elevated exposure to arsenic.