Endosulfan’s Effects: Omissions and Flawed Data

We would like to address problems with the article “Effect of Endosulfan on Male Reproductive Development” by Saiyed et al. (2003). Our comments are based on extensive discussions with several experts and decision-making bodies on the subject. First, Saiyed et al. (2003) described the results from a report first submitted in India in July 2002 by the National Institute of Occupational Health (NIOH 2002). We noted with interest that Saiyed et al. (2003) did not include additional or new data in the article beyond what was presented in the original report (NIOH 2002). Consequently, there was no need for discussing the results again. The original NIOH report (NIOH 2002) was submitted to an expert panel of Indian scientists appointed by the Government of India. The results of this review were reported to the Indian Central Insecticides Board and Registration Committee in April 2003. The committee was highly critical of the overall conduct of the study and concluded that “there is no link established between use of endosulfan in PCK [Plantation Corporation of Kerala] plantations and health problems reported in Padre village”(Central Insecticides Board and Registration Committee 2003). This was further endorsed at a subsequent meeting of the Registration Committee in September 2003. The Indian scientists who reviewed this report evidently had some major advantages of additional information that were not available to the reviewers of the article by Saiyed et al. (2003). Namely, they had access to all of the data, they could consult the authors, and they clearly comprehended the local situation in the region of India under consideration. Therefore, they found that the NIOH study (NIOH 2002) failed to prove what appeared to be an apparently flawed hypothesis. Referring to the statement by the Central Insecticides Board and Registration Committee (2003), the Minister for Agriculture reiterated in the Indian parliament that “The [Government] of India also constituted an expert committee and based on its recommendations decided that the use of endosulfan be continued as per provisions of Insecticides Act 1968 as there is no link established between the use of endosulfan in PCK plantations and health problems in Padre village. ” In their article in EHP, Saiyed et al. (2003) emphasized the premise that the geographical area studied was unique, with only a single pesticide used over a long period of time. Unfortunately, this is not correct; local records show that several pesticides were applied in this area. Furthermore, what is also apparent from local records is that several of the same pesticides were also commonly used in the control area. Thus, the scientific value of this study is questionable. For sexual maturity rating (SMR) and hormone levels, the results presented by Saiyed et al. (2003) displayed a relatively poor correlation with age; this is not enough to clearly describe a positive correlation. There are two additional confounding factors: a) small sample size (small number of subjects and only one blood sample per subject), which was recognized by the authors, and b) Saiyed et al. (2003) did not mention the normal biological ranges for either SMR or hormone levels in such a population. For example, serum hormone levels are highly variable and, without reference to what would be considered a normal range, the authors cannot confidently claim that the apparent changes they described were caused by pesticide exposure. This is evident in the last paragraph of the article, in which Saiyed et al. (2003) concluded that “ long-term follow-up of the children is essential to understand the implications. ” As a measure of endosulfan exposure, the authors described serum levels of endosulfan and endosulfan sulphate. There are a number of interesting paradoxes with these results. The first is that endosulfan was not used in the area, as described in the article, for 10 months before the study started. Given the rapid biodegradation and subsequent clearance of endosulfan in this type of environment, it is surprising that endosulfan was discovered in these samples. To further confound this, the levels of endosulfan, again as described by Saiyed et al. (2003), were ≥ 0.03 ppb in water and ≥ 0.3 ppb in pond sediments, well below the levels in the serum samples. Endosulfan is rapidly cleared from the body and does not bioaccumulate; thus, the serum levels are clearly at odds with those found in water samples, including those of the control samples. It should also be added that the water levels of endosulfan described by Saiyed et al. (2003) are well below the maximum recommended by the U.S. Environmental Protection Agency (EPA). The distance between PCK plantations and Vaninagar school is about 3 km. The amount of endosulfan applied in the PCK plantation block closest to Vaninagar school was about 105 g active ingredient (ai)/acre/year, whereas the permissible application rates authorized by the U.S. EPA are > 1,000 g ai/acre/season. Saiyed et al. (2003) did not include this fact in their article. In the area described by Saiyed et al. (2003), aerial application was carried out by helicopter at a height of about 10 feet above cashew tree plantations. It is highly unlikely that the sprayed endosulfan would drift away all the way to the Vaninagar school area 3 km away. Also, the interval between annual aerial applications was about 11 months. Endosulfan is likely to undergo significant degradation during this period. In this area, it is highly unlikely that significant amounts of endosulfan would have translocated with rainwater runoff during monsoon rains, which normally occur 5–6 months after aerial application. Under typical conditions in India, significant degradation of endosulfan would have occurred. The endosulfan residue levels Saiyed et al. (2003) reported in blood samples were 1,000 times higher than those reported in water samples. Based on the physicochemical properties of endosulfan, such a finding is highly unlikely. Finally, the reproductive effects of endosulfan reported by Saiyed et al. (2003) are inconclusive. We are concerned with the comment made by EHP’s Science Editor, Jim Burkhart, in the press release dated 1 December 2003 (EHP 2003): Decades of spraying this pesticide, and only this pesticide, on the village provided a unique opportunity to analyze its impact. Although the sample size is somewhat limited, the results are quite compelling. Calling the results “compelling” has caused significant paranoia among users of endosulfan and the general public. A number of pesticides were in use around Padre village for many decades, so it was not correct to state that only one pesticide was used. In conclusion, we hope we have shown that the article by Saiyed et al. (2003) does not contribute to the knowledge on the behavior of endosulfan or to the research to determine the cause of health problems of the people in Padre village. In view of the foregoing facts, we believe that EHP should reevaluate their review of the article by Saiyed et al. (2003).