Birth Control – But for Whom?

In light of the changing political climate, specifically with the recent overturning of Roe v. Wade in the United States, the rate of birth control prescriptions is on the rise (Langmaid, 2022). The most common form of birth control remains oral contraceptives (OCs), with 75% of Canadian and 88% of American females taking OCs at some point in their lifetime (Government of Canada, 2015; Barakat et al., 2020; Britton et al., 2020). While OCs effectively prevent pregnancy, recent studies have discussed the potential for the hormones found in these contraceptives to leech into local waterways, causing detrimental effects on an ecological level (Britton et al., 2020). 

OCs are a hormonal form of prescription birth control taken every 24 hours to prevent pregnancy, regulate menstrual cycles, treat acne, endometriosis, and ovarian cysts, as well as reduce the risks of endometrial and ovarian cancers (Government of Canada, 2015; Barakat et al., 2020; Britton et al., 2020). There are two main types of hormonal OCs — progesterone-only and estrogen-progesterone, also known as the combined oral contraceptive pill (COC), which is the most widely used form (Cooper, Patel and Mahdy, 2022). Progesterone is a hormone formed during pregnancy by the adrenal cortex and gonads (Cable and Grider, 2022; Cooper, Patel and Mahdy, 2022). Progesterone is also the primary hormone present responsible for preventing pregnancy by suppressing ovulation, thickening cervical mucus, lowering fallopian tube motility, and thinning the endometrium (Britton et al., 2020). Estrogen, on the other hand, is the female reproductive hormone responsible for the control of menstrual bleeding (Cooper, Patel and Mahdy, 2022; Delgado and Lopez-Ojeda, 2022). Estrogen prevents irregular bleeding and prevents follicle development (Britton et al., 2020). 

While beneficial for their intended purpose, these hormonal OCs make their way into local waterways due to a combination of factors (Figure 1). Estrogen’s presence in waterways is partially due to the incomplete removal of the hormone during the water treatment process (Caldwell et al., 2010). Individuals on OCs release significantly higher concentrations of estrogen in their urine which cannot be fully filtered out by current water-treatment systems. While research has found that the concentration of estrogen in our drinking water is small enough to have no significant effect on humans, many aquatic species that survive in waterways are facing detrimental effects (Caldwell et al., 2010; Gonsioroski, Mourikes and Flaws, 2020).

Figure 1: Estrogen levels in waterways and subsequently filtered drinking water are the result of a combination of factors including landfill runoff, agricultural (pesticide) runoff, livestock excretions, industrial production, and residential waste. Estrogen levels from hormonal OCs fall under residential (home) waste, as estrogen is released through urine and carried to wastewater treatment plants. EE2 is the type of estrogen found in many OCs. From there it is treated and the remaining estrogen is released into waterbodies or filtered as drinking water (Wise, O’Brien and Woodruff, 2011).

Prolonged estrogen exposure impairs the development and reproductive function of species. One example of this is the feminization of fish (Gonsioroski, Mourikes and Flaws, 2020). Estrogen exposure beyond normal limits impacts gonad development by interacting with estrogen receptors (Figure 2). This causes an inversely proportional relationship between the number of fish with normal testes and the number of intersex fish (Gross-Sorokin, Roast and Brighty, 2006). Since intersex male fish have decreased sperm production and mobility, their reproductive success is reduced (Kidd et al., 2007). Female fecundity, or the ability to produce many offspring, was also reduced (DeQuattro et al., 2012). With prolonged exposure to estrogen in waterways, the male and female reproductive systems of fish populations are greatly impacted.

Figure 2: Biological section of minnow gonadal tissue. Tissue sample A is a control ovary sample from a minnow residing in a lake without added estrogen. Tissue sample B is from a female minnow in a lake with high estrogen levels. The arrow points to a follicle that has failed to develop due to estrogen exposure. Tissue sample C is a control testes sample from a minnow residing in a lake without added estrogen. Tissue sample D is from a male minnow in a lake with high estrogen levels who has become intersex. The arrow is indicating developing ovaries in the intersex male minnow (Kidd et al., 2007).

While birth control has great benefits for those electing to use it, the negative effects of hormonal OCs on aquatic species ensure that it is not a perfect solution. Further research needs to be done to identify birth control options that are safe, effective, and environmentally friendly for all. 


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Kidd, K.A., Blanchfield, P.J., Mills, K.H., Palace, V.P., Evans, R.E., Lazorchak, J.M. and Flick, R.W., 2007. Collapse of a fish population after exposure to a synthetic estrogen. Proceedings of the National Academy of Sciences, 104(21), pp.8897–8901.

Langmaid V., 2022. Contraception demand up after Roe reversal, doctors say | CNN. [online] Available at: <> [Accessed 4 December 2022].

Wise, A., O’Brien, K. and Woodruff, T., 2011. Are Oral Contraceptives a Significant Contributor to the Estrogenicity of Drinking Water? Environmental Science & Technology, 45(1), pp.51–60.

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