Humans Causing Their Own Doom, PFAS Effects on Reproductive Hormones

You may have heard of the newly emerging environmental issue on PFAS contamination. PFAS otherwise known as Perfluoroalkyl substances is a man-made chemical widely used in fire extinguishers and firefighting foam, food packaging, waterproof fabrics, non-stick cookware, cosmetics, pharmaceuticals, pesticides, cleaning agents, and paints (Salihovic et. al. 2015 & Seo et. al. 2018).

Exposure has been mainly from the consumption of fish, meat, and dairy, drinking water contamination, and home products (Salihovic et. al. 2015). There is also a strong correlation between contamination of drinking water and spatial proximity to industrial point source pollution, military fire training run-off, and wastewater treatment plants (Blake et. al. 2018).

There is also a strong correlation between contamination of drinking water and spatial proximity to industrial point source pollution, military fire training run-off, and wastewater treatment plants (Blake et. al. 2018).

PFAS can affect thyroid hormone homeostasis and has led to decreased thyroid stimulating hormones (TSH). TSH increases basal metabolic rate, aid in bone growth and affects protein synthesis. There have also been studies reporting increased mortality rates caused by diabetes based on PFAS exposure (Seo et. al. 2018).

PFAS is associated with a wide variety of diseases, including endocrine disruption, developmental health effects, cancer and metabolic changes (Blake et. al. 2018). In particular, PFAS levels are associated with lower SHBG levels, lower FSH levels, and lower testosterone levels in adolescent and young females (Tsai et. al. 2015). PFAS has also been linked to lower testosterone levels in males (Joensen et. al. 2013& Zhou et. al. 2016).

SHBG is a sex hormone binding globulin and binds to testosterone and estrogen (SHBG 2019). FSH is a follicle stimulating hormone that regulates development, growth, pubertal maturation and reproductive processes. FSH stimulates the production of testosterone, therefore it makes sense that there have been lower FSH and testosterone with increased PFAS levels.

Testosterone is important for the development of reproductive tissues, triggers the growth of muscles, bone mass, and body hair increases sex drive and produces sperm (Wein 2013). This hormone is essential in the male reproductive system. A significant decline in testosterone could affect the fitness of male humans.

Since PFAS bioaccumulates, concentrations are higher in older people, males, and is correlated with higher cholesterol as well since it binds to lipids and fats (Seo et. al. 2018).

PFAS cannot be fully eliminated from municipal water systems (Blake et. al. 2018). If you are concerned about PFAS contamination in your water use a trusted water source and avoid drinking or cooking water contaminated with PFAS.

 

References

Blake et. al. (2018) Associations between longitudinal serum perfluoroalkyl substances (PFAS) levels and measures of thyroid hormone, kidney function, and body mass index in the Fernald Community Cohort. Environmental Pollution pp 894-904.

Joensen et. al. (2013) PFOS in serum is negatively associated with testosterone levels, but not with semen quality, in healthy men. Human Reproduction pp 599-608

Salihovic et. al. (2015) Perfluoroalkyl substances (PFAS) including structural PFOS isomers in plasma from elderly men and women from Sweden: Results from the Prospective Investigation of the Vasculature in Uppsala Seniors. Environment International pp 21-27.

Sex Hormone Binding Globulin (2019) University of Rochester Medical Center. Retrieved from https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=167&ContentID=shbg_blood

Seo et. al. (2018) Influence of exposure to perfluoroalkyl substances (PFASs) on the Korean general population: 10-year trend and health effects. Environmental International pp 149-161.

Tsai et. al. (2015) Association between perfluoroalkyl substances and reproductive hormones in adolescents and young adults. International Journal of Hygiene and Environmental Health pp 437-443.

Wein (2013) Understanding How Testosterone Affects Men. National Institutes of Health. Retrieved from https://www.nih.gov/news-events/nih-research-matters/understanding-how-testosterone-affects-men

Zhou et. al. (2016) Association of perfluoroalkyl substances exposure with reproductive hormone levels in adolescents: By sex status. Environment International pp 189-195.

The Need for Illumination is Causing Havoc Among Sea Turtles

Light pollution is not just the obstruction of the night sky, it is also hundreds of thousands of lights illuminate the sky and that light reflects from the sky causing, “sky glow.” This is a major problem for ecosystems that include nocturnal animals (Longcore and Rich 2004). Responses to light pollution are orientation/disorientation, attraction and repulsion. For a hatchling sea turtle, disorientation is the unfortunate response (Longcore and Rich 2004 & Bourgeois et al. 2009).

 (Longcore and Rich Ecological light pollution 2004)

Hatchlings emerge at night on sandy beaches and use the high silhouettes of the dune vegetation, which absorbs light, as an indicator to move in the opposite direction towards the lower brighter horizon (Longcore and Rich 2004 & Bourgeois et al. 2009). The ocean break reflects light and allows hatchlings to seafind (Salmon 2003).

Their cues are mainly associated with light intensity and horizontal elevation (Bourgeois et al. 2009). With lighting on the beachfront, there is no longer the reception of those cues. (Longcore and Rich 2004). Some hatchlings rely on elevation cues over light, but the movement towards the brightest light occurs when the horizon elevation is similar in each direction (Bourgeois et al. 2009).

Their optic orientation systems are adapted to natural illumination and therefore fail to cope with artificial light (Verheijen 1985). This disorientation causes the path to the ocean to elongate, which increases mortality of sea turtles through exhaustion, dehydration, increased predation and human traffic (Bourgeois et al. 2009). Even if they do make it to the ocean, they are more likely to die because of the amount of energy it took them to get there and the high energetic cost of their first days of life is not enough to sustain them (Bourgeois et al. 2009).

Another way anthropogenic light pollution affects sea turtle sensory systems is the disruption of nest-site selection. Brightly lit beaches have shown significantly fewer turtles emerge to nest on their shores (Witherington and Martin 2003).

The white light which contains both long and short wavelengths deters turtles while longer wavelength light does not (Salmon 2003). Female sea turtles lay their eggs at night and the artificial light repels them most likely because it disorients them and makes them think it is day time (Witherington and Martin 2003). This is most likely a survival tactic to protect their eggs from predators that are hunting during the day.

To protect these sea turtles, regulations should be made to either turn the light sources off or reduce the number and wattage of them. Also, if lights are necessary, positioning them so that their light does not reach the beach would help as well (Witherington and Martin 2003). If you are interested in getting involved with sea turtle conservation, check out Caretta Research Project located in Savannah, GA at carettaresearchproject.org

(Hailey Hayes Caretta Research Project July 2018 Savannah, GA)

 

References

Bourgeois et al. (2009) Influence of artificial lights, logs and erosion on leatherback sea turtle hatchling orientation at Pongara National Park, Gabon. Biological Conservation pp 85-93.

Longcore and Rich (2004) Ecological light pollution. Frontiers in Ecology and the Environment.

Salmon (2003) Artificial night lighting and sea turtles. Biologists pp 163-169

Witherington and Martin (2003) Understanding, Assessing, and Resolving Light-Pollution Problems on Sea Turtle Nesting Beaches. Florida Marine Research Institute Technical Reports.

Verheijen (1985) Photopollution: Artificial light optic spatial control systems fail to cope with. Incidents, causations, remedies. Experimental Biology pp1-18.