CORRESPONDENCE/REBUTTAL pubs.acs.org/est
Response to Comment on “Are Oral Contraceptives a Significant Contributor to the Estrogenicity of Drinking Water?”
W
e appreciate Dr. Gryzbowski’s feedback and welcome dialogue on this important issue. We agree estrogens in the environment are a concern for environmental health, and we were originally motivated to investigate this topic to help clarify the complex range of scientific information on this issue. While oral contraceptives cannot be completely removed from this complicated equation, we believe our findings suggest there are many other sources of estrogenic substances, including untreated agricultural waste and industrial pollution that can contribute in significant ways to estrogenic properties of our waterways. Accordingly, we would like to respond to the comments from Dr. Gryzbowski. First, in reference to the figure on contribution of different natural estrogens and 17-R estradiol (EE2), from different segments in the Dutch population, we agree it is challenging to present this data. Ideally, we would have data from more populations (for example other countries), and data that would allow more nuanced evaluation of sources of natural estrogen and EE2 (for example, information on the variability in the data). Nevertheless, both the figure and the data show a very small (∼1%) contribution from oral contraceptives to overall volume of estrogen excretions from the human population in The Netherlands (though as we note in the figure caption, this does not account for potency differences). We used the same data as Dr. de Mes1 from the Dutch government to create our figure. We agree an additional reference to her publication is appropriate.1 Second, Table 1 contains information intended to compare natural estrogen excretion by humans on a daily basis to illustrate all portions of the population excrete natural estrogens, including men. Later in the paper we also consider additional sources of estrogens to waterways (such as agricultural waste and industrial sources). Cattle, depending on their sex and reproductive status, will excrete 45 100 000 μg of total estrogens per day per animal.2 Researchers have estimated that women on the pill excrete 26 μg of total estrogens per day (∼16 μg of natural estrogens3 + ∼10 μg of EE2 from pill 4). It is important to keep in mind that excretion by humans enters wastewater treatment systems and the active forms of estrogens are reduced further, 50 98%, unlike the other sources of estrogen to waterways (see refs 25, 26, 27, 28, 37, 43, 60, 62, 63, and 64 from our original publication). Third, Dr. Gryzbowski suggests including sulfate-conjugated EE2 as part of the total EE2 in human excretion because it has the possibility of reverting back to “active” EE2 in the environment. This is a plausible scenario, though it is difficult to estimate the rate and efficiency of this reaction, as these factors depend on many environmental variables. Additionally, it would not significantly affect the amount of estimated EE2 that enters the environment, as it is only approximately 10% of the total estimated to be excreted into wastewater prior to sewage treatment. Finally, we appreciate the additional information presented by Dr. Gryzbowski about the relative potency of EE2 compared to E2. This is a challenging area to evaluate as there are many methods for evaluating relative potencies. We originally calculated r 2011 American Chemical Society
our values from the following references: Van den Belt, et al. 2004,5 Folmar et al. 20026 using the in vitro values. Unfortunately, we did not include the Folmar citation originally and we are taking this opportunity to correct the references. If including all methods of potency determination (both in vitro and in vivo), one might estimate a somewhat higher potency for EE2 than we originally reported in our publication. However, this should still be considered in light of the following findings: (1) wastewater treatment systems have been shown to be highly effective in removing synthetic estrogens before they reach the environment and drinking water treatment removes virtually all of them before reaching our tap; and (2) there are many other sources of estrogens in the environment that enter waterways untreated, including agricultural waste, industrial synthetic estrogens and estrogenic plant compounds. We agree that we should take steps to reduce presence of all endocrine disrupting compounds in our environment, which includes EE2. In particular, we note that reducing sources of estrogens in the environment is an important approach to mitigating exposures, including methods that reduce the excretion of EE2, such as low-dose hormonal contraceptives. A critical piece of missing data is a systematic testing of various surface and drinking water samples in the United States with appropriately low limits of detection so we can get an accurate picture of what chemicals are actually present and at what levels. We believe this is an issue that should be more thoroughly addressed in environmental policy worldwide. And further attention, such as through these correspondences, helps raise important awareness on this issue. Wise Amber O’Brien Kacie and Woodruff Tracey J.*
’ AUTHOR INFORMATION Corresponding Author
*Phone: 510 986 8942; e-mail:woodruff
[email protected].
’ REFERENCES (1) de Mes, Titia; Grietje, Zeeman; Gatze, Lettinga. Occurrence and fate of estrone, 17b-estradiol and 17a-ethynylestradiol in STPs for domestic wastewater. Rev. Environ. Sci. Bio/Technol. 2005, 4, 275–311. (2) Lange, I. G.; Daxenberger, A.; Schiffer, B.; Witters, H.; Ibarreta, D.; Meyer, H. H. D. Sex hormones originating from different livestock production systems: fate and potential disrupting activity in the environment. Anal. Chim. Acta 2002, 473, 27–37. andJohnson, A. C.; Williams, R. J.; Matthiessen, P. The potential steroid hormone contribution of farm animals to freshwaters, the United Kingdom as a case study. Sci. Total Environ. 2006, 362 (1 3), 166–178. (3) Johnson, A. C.; Belfroid, A.; Di Corcia, A. Estimating steroid oestrogen inputs into activated sludge treatment works and observations on their removal from the effluent. Sci. Total Environ. 2000, 256 (2 3), 163–173. Published: August 12, 2011 7606
dx.doi.org/10.1021/es202309x | Environ. Sci. Technol. 2011, 45, 7606–7607
Environmental Science & Technology
CORRESPONDENCE/REBUTTAL
(4) Johnson, A. C.; Williams, R. J. A model to estimate influent and effluent concentrations of estradiol, estrone, and ethinylestradiol at sewage treatment works. Environ. Sci. Technol. 2004, 38 (13), 3649–3658. (5) Van den Belt, K.; Berckmans, P.; Vangenechten, C.; Verheyen, R.; Witters, H. Comparative study on the in vitro/in vivo estrogenic potencies of 17[beta]-estradiol, estrone, 17[alpha]- ethynylestradiol and nonylphenol. Aquat. Toxicol. 2004, 66. (6) Folmar, L. C.; Hemmer, M. J.; Denslow, N. D.; Kroll, K.; Chen, J.; Cheek, A.; Richman, H.; Meredith, H.; Grau, E. G. A comparison of the estrogenic potencies of estradiol, ethynylestradiol, diethylstilbestrol, nonylphenol and methoxychlor in vivo and in vitro. Aquat. Toxicol. 2002, 60, 101–110.
7607
dx.doi.org/10.1021/es202309x |Environ. Sci. Technol. 2011, 45, 7606–7607
