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Abstract
Our six years of field experience in Bangladesh showed that normally children under 11 years of age do not show arsenical skin manifestations. However, we have observed a few exceptions when (1) the arsenic content in water consumed by children is very high (≥1,000 µg/L) and (2) the arsenic content is not very high, but the children get poor nutrition. It appears that although 6.12% of 4,864 children showed arsenic skin lesions but hair and nail analysis of children (below 11 years) with or without arsenical skin lesions from affected villages of Bangladesh showed that 84% of the children had arsenic in hair more than the toxic level and 89% in nail above normal level. It appears that children living in arsenic affected villages have higher arsenic body burden but less dermatological symptoms. The value of arsenic excretion and arsenic intake per kg of body weight ratio for adults is 0.53 while that of the children is 0.69. This indicates total arsenic excretion is higher for children per kg of body weight than adults. The average values (n = 18) for speciation of arsenic in children urine are 15.60% In-As, 10.64% MMA, and 73.76% DMA. Overall percentage of MMA is higher, and DMA is lower in adults than children (average % MMA is 17.20 vs. 10.64 and % DMA is 64.62 vs. 73.76%, respectively). Therefore, the 2nd methylation step (MMA to DMA) could be more active in children than adults. The results indicate that the first reaction of the metabolism pathway is more active in adults than children, basically in adult’s male. Also shows a significant (t-test positive) increase in the values of the DMA/MMA ratio in children compared to adults of the exposed group (8.15 vs. 4.11, respectively). Moreover, it is also observed that the second methylation step in the arsenic metabolic pathway is more active in children than adults. Because there is no significant difference of the values of MMA/iAs ratio, but the values of DMA/MMA ratio are significantly different between adults and children of the exposed group (0.92 vs. 0.73 for MMA/Asi and 4.11 vs 8.15 for DMA/MMA, respectively). Thus, from these results we may conclude that children retain arsenic shorter in their body comparing adults.
The distribution of the values of DMA/MMA ratios with different ages of exposed humans shows that the DMA/MMA ratio decreases with increasing age, i.e., the methylation process decreases with increasing age. This observation also supports that the 2nd methylation process of arsenic (MMA to DMA) in children is better than the adults.
In conclusions, i) it appears that children living in arsenic affected villages have higher arsenic body burden but less dermatological symptoms, ii) children require more water than adults in terms of ml, per kg body weight, iii) the average values for speciation of arsenic in children urine are 15.60% In-As; 10.64% MMA, and 73.76% DMA), iv) methylation capacity (2nd methylation step) in children is better than adults, v) methylation process of arsenic (MMA to DMA) decreases with increasing age, and vi) may be children excrete arsenic faster i.e., retain less arsenic in their cellular system than adults.
