Arsenic species were analyzed in urines of arsenic exposed and control children (B, n=17; G, n=10), adults (M, n=22; F, n=20), and domestic animals (cow, n=31; calf, n=1; and goat, n=1) by using HPLC-ICP-MS. Urinary arsenic concentration increases with increasing arsenic concentration in drinking water. Strong correlations were not observed, and the reasons may be subjects were drinking water from mixed sources; adult males and children normally drink water from many sources as they spend most of their daytime outside (in field, market, working place, school, etc.).
The results show that average percentage of Inorg-As, MMA, and DMA for exposed adult males are 15.52%, 17.49%, and 66.99%; for adult females 20.41%, 16.96%, and 62.63%; for children males (boys) 14.39%, 10.28%, and 75.33%, and for children females (girls) 18.77%, 11.60%, and 69.63%, respectively. It appears that there is no significant difference for the average percentage of arsenic species in urine between adult males and females, and between boys and girls. Also, there is no significant difference for the average percentage (%) of arsenic species in urine between exposed and control groups. But the results indicate that first step of the methylation pathway is more active in adults than children, but second methylation step is more active in children than adults and it shows a significant (t-test positive) increase in the values of the DMA/MMA ratio in children than adults of exposed group (8.15 vs. 4.11, respectively). There is no difference between the value of DMA/MMA ratio in adult males and females (average 4.22 vs. 4.03). But DMA/MMA ratio in boys is greater than girls (8.62 vs 6.93).
The average percentages of Inorg-As, MMA, and DMA for exposed cow group are 2.20%, 10.41%, and 87.38%, respectively. It appears that the presence of DMA, MMA, and As(V); and also possibility of an unknown arsenic species at the retention time is 108 sec in both exposed and control cows. It shows a significant increase in the values of the MMA/As-inorg and DMA/MMA ratios in cows than adults and children of exposed group (1st step: 6.68, 0.92, & 0.73 and 2nd step: 12.39, 4.11, & 8.15, respectively). The percentages of DMA, MMA, and As(V) and also possibility of an unknown arsenic species at the retention time 108 sec in both calf and mother cases (78.3% vs. 75.5%, 17.8% vs. 23.3%, and 3.9% vs. 1.2%, respectively) where total arsenic metabolites in urines for calf and mother are 141.3 and 1794.6 μg/L, respectively. The urinary percentages of DMA, MMA, and As(V) for exposed goat are 68.13%, 22.48%, and 9.39%, respectively where total arsenic metabolites is 29.8 μg/L of urine. In conclusion, these results indicate that (i) methylation capacity (2nd step) in children is higher than adults, (ii) the methylation pathway is more active in cow animal comparing human of exposed group, (iii) the cow animal excrete more DMA and less MMA and In-As in urine than human, (iv) the arsenic species of calf and mother cow are similar. This obviously indicates that during pregnancy mother cow transfers arsenic to calf, i.e., arsenic passes through placenta barrier (only one study), and (iv) It appears that arsenic species of goat is like that of cow (one study only).