Arsenic and Drinking Water in West Bengal

To the Editor: I read the research findings of Basu et al. (1) with great interest. However, there are some points which should be discussed. The authors showed that the level of lymphocytes with micronuclei in control (unexposed) persons was extremely low (1.66%). For example, in some European nations it is between 7% and 18% (2-7), and the least is in Turkish subjects—2.8% (8). According to the data of the Human MicroNucleus project (9), this index is 6% to 18%. In Indians the micronuclei level is 7.5% (10) and the closest to the data presented by Basu et al.—1.6 (11). Earlier, Basu et al. (12) showed that this index in healthy persons from the same region of India was even lower—0.53%. In both cases they studied enough cells, and this cannot be a source of bias. By the way, the level of oral cells with micronuclei is also very low compared with other data concerning healthy subjects from India (0.19-0.27; refs. 13, 14). It would be of interest to know their explanations why the number of lymphocytes with micronuclei in their studies is one of the lowest in the world! The levels of lymphocytes and buccal cells with micronuclei in healthy persons (1.66% and 1.28%, respectively) are very close. However, this ratio (lymphocytes with micronuclei / buccal cells with micronuclei) in healthy European subjects is 4.8 to 18.4 (6, 15). Even in the above-mentioned article concerning Turkish subjects (8) the ratio is 3.5. In the report of Basu et al. (1) it is only 1.29! And this needs to be explained. I could not find in the article (1) which stain was used for epithelial cells although this information about lymphocytes is presented. This is a very important question, and I recently discussed this problem (16). The data about the duration of living of exposed persons in the area and consuming water with arsenic are absent. For example, to study the micronuclei-inducing activity of chlorinated water on bladder cells (17) recruited people should reside at the needed area for at least 6 months. This information should be presented, which could help to calculate the cumulative dose of ingested arsenic. On page 826 the authors discussed about higher micronuclei level in lymphocytes than in oral and bladder cells. I disagree with their explanations because it is well established that use of micronuclei in exfoliated buccal and bladder cells to detect clastogenic and aneugenic effects induced by various mutagens/carcinogens is less efficient than use of both micronuclei and chromosomal aberrations in lymphocytes (16), and there is no significant difference between them. The authors wrote that ‘‘the three different levels of arsenic in drinking water did not affect the micronuclei proportions in the three subgroup(s) within the exposed group. This could probably be due to differences in quantity of water intake and duration of arsenic exposure in the study participants as well as interindividual variations in susceptibility to arsenic’’. All three t in Table 3 are less than 0.05. I am not sure about the level of significance in Cochran-Armitage test, but at first glance micronuclei in lymphocytes and in bladder cells correlated with arsenic content in water significantly. And about the duration of exposure I wrote earlier, it is a shortcoming in the design of the experiment. The authors cited an article (their ref. 43) and stated that ‘‘the high carotene content of betel leaf. . . make betel quid less toxic and carcinogenic than cigarette smoking. . .’’. However, it is well known that betel quid with and without tobacco is carcinogenic to humans—group 1 agent according to IARC expert classification (18, 19). Hence, the mentioned sentence is not correct. By the way, almost all investigators showed micronuclei-inducing activity of betel quid in oral mucosa cells; however, the data concerning micronuclei-inducing activity of cigarette smoking are contradictory (14). Then, the authors wrote that ‘‘within the exposed group, addicted individuals exhibited significantly increased micronuclei frequency (P < 0.01) over nonaddicted ones in oral mucosa cells’’. According to the data presented in Table 2, the difference between micronuclei levels in lymphocytes also should be significant. My calculations using Student’s t test showed that t=2.3, and it should be significant at least on level of P < 0.05. By the way, in Table 2 all P values (it ought to be p instead of P in the Table 2 in my opinion) are the same (P < 0.01), although U values varied from 6.59 to 26.82! The authors stated that ‘‘among the addicted, the increases in the micronuclei frequencies were less for all the three cell types... than in nonaddicted category’’. However, they did not explain why. Moreover, on page 826, right column, the authors wrote about synergistic effect of arsenic with the betel quid chewing habit, which, of course, was a contradiction. There are also some linguistic errors. On page 825, left column, the authors wrote ‘‘observed in unexposed lymphocyte culture’’. It should be ‘‘in lymphocyte (culture) of unexposed subjects,’’ because the subjects were exposed, not the cultures! A little further, it is writen that ‘‘...was 4.40-fold over unexposed,’’ which looks like an error. In the statement of the authors that ‘‘urothelial cell micronuclei reflect damage to the bladder epithelial tissue, which occurs 1 to 3 weeks prior...’’ the word ‘‘urothelial’’ should be replaced with ‘‘epithelial’’. On page 825 it is written that micronuclei incidence in urothelial cells was found to be slightly elevated (5.02). However, 5-fold increase in the level of exfoliated cells with micronuclei is a great one for epithelial cells (14, 16)! The authors (1) wrote that ‘‘exfoliated epithelial cells have traditionally been used for cancer screening and biomonitoring of genotoxic effects in humans (page 820)’’ citing the article dated 2003 although there are a lot of other sources dated much earlier. On page 826, left column, the authors wrote that ‘‘unlike the study of Warner et al. (30) in which they reported absence of significant micronuclei incidence in oral mucosa cell. . .’’. However, the aim of the cited authors was to study micronuclei level in bladder cells. In conclusion, very interesting data are presented with a lot of errors and shortcomings.