Firstly, phthalates are known to be weak endocrine disruptors and androgen blocking chemicals. This means that when phthalates are absorbed into the body, they mimic and block female hormones, and in males, they suppress hormones related to sexual development. This suppressed sexual development then leads to the aforementioned decrease in fertility and penis size in men. Men’s fertility is affected as these chemicals decrease sperm quality and count, leading to decreased instances of pregnancy, leading to Dr. Swan stating that on average, men today have approximately half the sperm his grandfather did. Swan also stresses the importance of timing and other factors with respect to the issue of falling sperm counts, saying, “Babies are now entering the world already contaminated in chemicals from the mother’s womb”. For example, she states that if a mother smokes while pregnant with his son, his sperm count is decreased by 40%; if he is then later in life exposed to endocrine disruptors such as phthalates, there is a high likelihood his sperm counts drop so low that he is infertile. 

The second issue, which was of course the real headline grabbing effect of these phthalates, and maybe why you’re still reading this article, is their effect on penis size. Dr. Swan has long theorized about the effects of these phthalates on fertility, working on a study in 2005, which linked the effects of phthalates on sexual development of males after noting the effects of these chemicals on rats. During this study, she observed what she calls “phthalate syndrome”, which includes smaller penis sizes and testicles that had not fully developed by the 12-month checkup on baby boys. It was found in 2005, and backed up by further recent research, that these phthalates are affecting penis size and development by decreasing the anogenital distance (AGD) in men. Anogenital distance is the distance from the anus to the genitals and is important as it provides an index on fetal androgen exposure and masculinization. It has been found that shortened AGD has been correlated with these decreases in penis size and fertility. As a result, increases in phthalate exposure in the womb causes these decreases in penis size and development.

Pollution impacting species fertility is nothing new. For example, Bisphenol A (BPA) is a pollutant, which has frequently been in the news due to research finding that it disrupts hormone signaling and reproductive function in many species, leading to bans of the substance being used in baby bottles. You may have also noticed many plastic bottles being marketed as “BPA Free” due to active efforts by people to avoid these chemicals. There are also many forms of pollution with environmental toxicants being just one. For example, light pollution is resulting in decreased instances of successful sea turtle nesting as females will not lay eggs in brightly illuminated areas, as well as attracting baby turtles once they have hatched. This leads to many of the hatchlings dying as they are born in unsuitable spots or are attracted to lights rather than the ocean. These effects are, however, paid more attention to, as sea turtles are a species at risk, and reactive rather than proactive measures can be now implemented. For humans, I’m not sure we will have the luxury of a reactive approach.