The first time I can remember hearing about microplastics and their negative effect on our health was during my pediatric endocrine fellowship, at least 15 years ago. In all honesty, at the time I was not very impressed. It seemed to me something that only the “crunchy” crowd was worried about. Well, I am here to admit, my instincts were probably wrong. Fast forward to 2024, and wow has the outlook changed. More and more research has been published linking microplastics with a whole host of adverse biologic effects, ranging from hormones and fertility to cancer risk and cognitive health. Today scientists and thought leaders from across the ideological and political spectrum are sounding the alarm on the harm that microplastics have on our bodies.

It is a tough problem, because plastics are part of our everyday life in a way that don’t realize until we really think about it. There is simply no way to get away from them. Outside of moving to the rain forest and hunting and growing our own food, it is really a question of decreasing exposure as opposed to completely avoiding it.

But thankfully there are some effective ways to reduce our exposure. Some of them are fairly easy, while others are more costly and involve more sacrifice. We review some practical suggestions at the end of the article. Before we do that, we’ll discuss exactly what plastics and microplastics are, and what their harmful biologic effects are thought to be. The effects are wide-ranging, and just about any system in the body can be impacted, but in this article we will focus specifically on the endocrine system and the brain.

What are microplastics?

We want to live “naturally” but our environment is no longer “natural.” We are bombarded with toxic chemicals on every front. One of the most ubiquitous compounds that is relatively new in our modern world is plastic. You cannot go through a day without encountering plastic. Their lightweight, flexible, durable nature has made them a favorite with manufacturers worldwide. Discovered in the 1860s, plastics did not enter the mainstream public until 1950s and their use has grown exponentially since then. Today plastics are everywhere: in the food we eat, in the air we breathe, in the water we drink and in the clothes we put on. Plastics easily degrade into micro or nano-plastics, and microplastics have been found in every organ tissue in the body, negatively affecting cell energy production, cell signaling and causing inflammation and cell death.

There are two broad categories of potential harm from plastics. The first is microplastics, which are small pieces of plastic (< 5 mm in length) that occur in the environment as a result of plastic exposure. Microplastics are present in a variety of products, from cosmetics to synthetic clothing to plastic bags and bottles.

The second category is the release of compounds used in the manufacture of plastics, such as bisphenol A (BPA) and phthalates. These chemicals can leach into our food and water. BPA is used in the manufacture of clear, hard polycarbonate plastics and is present in packaging, bottles, compact discs, medical devices, and the plastic linings of food cans and paper cups. Phthalates are plasticizers, which are softeners used to make plastic products less brittle. They are found in medical devices, food packaging, automobile upholstery, flooring materials, and computers as well as in pharmaceuticals, perfumes, and cosmetics.

Microplastics and Our Endocrine System

Phthalates have an anti-androgenic affect, which means they prevent the hormone testosterone (and precursors of testosterone) from exerting its biologic effects in the body. Prenatal exposure has been shown to affect male reproductive development. Increased prenatal phthalate levels are associated with decreased anogenital distance (AGD), which is the distance between the anus and the genitalia. This distance is generally twice as long in males as females. A study by Swan et al. in 2005 showed that babies with high total exposure to phthalates were ninety times more likely to have a short AGD. A 2015 study by the same author showed that women who had high levels of phthalates in their urine during pregnancy gave birth to sons who were ten times more likely to have shorter than expected AGDs. Males with a short AGD (defined as less than the median length) have lower semen volume and sperm count, and have seven times the chance of having infertility problems as those with a longer AGD. The levels of phthalates that are associated with significant AGD reductions are found in approximately one-quarter of Americans as tested by the CDC.

BPA mimics estrogen, acting as a “xenoestrogen” binding to estrogen receptors, which then can activate or block estrogen and results in altered estrogen metabolism. High BPA levels are linked with earlier puberty and decreased fertility. One study showed a higher prenatal BPA level was linked with an earlier puberty onset in girls. Another study of women undergoing IVF treatment showed a decrease in viable eggs with increasing urinary BPA. Increased BPA levels in men are also associated with decreased fertility, as well as decreased testosterone levels and a reduction in sperm quality. In addition, both BPA and phthalates interfere with the thyroid hormone receptors, disrupting T3 and T4 levels, which affect energy metabolism and cognitive function.

The historical rise in infertility rates, decline in men’s testosterone levels, and increasing prevalence of hormonal disorders such as polycystic ovarian syndrome (PCOS) likely have many contributing factors, but the increase in microplastic exposure is one very plausible explanation. It is also likely one of the reasons many middle-aged adults need hormone support to combat the anti-androgenetic and xenoestrogen effects of microplastics, which result in lower testosterone levels, lower thyroid levels, disrupted estrogen and progesterone levels.

Microplastics and Our Brain

One of the most alarming organs that microplastics are accumulating in is the brain. The brain has an extra barrier of protection that the other organ systems do not have called the blood/brain barrier, this is to protect the brain from harm. Unfortunately, microplastics have been able to cross the blood brain barrier and accumulate in the microglial cells, which are the brain’s immune cells, leading to an immune response and cell death. Brain samples from 2024 show an 50% increase in plastic from 2016 samples (Reference?). Individuals with dementia had 10 times more plastic by weight than those without dementia (Reference?). Microplastic accumulation was seen in the hippocampus and prefrontal cortex, areas that affect memory, learning and emotions. With the rapid increase in microplastic accumulation in the brain, we could be seeing an increase in neurodegenerative disease and increasing cognitive impairments.

Microplastics are not only affecting our aging brain, but also the developing brain. BPA has been associated with neurodevelopment problems. Prenatal BPA levels are linked with an increased risk of autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), anxiety and depression in children, especially boys. A Harvard School Public Health study showed a high prenatal BPA level was linked to behavior problems, including anxiety, depression, impaired social skills; all symptoms that overlap with ASD. Another study showed that the children of pregnant women with high BPA levels were more likely to have poor neurodevelopment. Increased BPA in pregnancy was linked with social deficits, increased anxiety and structural changes in the prefrontal cortex and hippocampus, the same areas affected by autism.

Conclusion

Microplastics and the chemicals associated with them are ever present, and the impact of microplastics on our health is far reaching and well documented. The historical rise in infertility rates, decline in men’s testosterone levels, and increasing prevalence of hormone disorders such as polycystic ovarian syndrome (PCOS) are all likely multifactorial in nature, but it is very plausible that the increase in microplastic exposure is a primary contributing factor. It is also likely one of the reasons many middle-aged adults benefit from hormone optimization to combat the hormone disrupting effects of microplastics, which result in abnormal function of our thyroid, testosterone, estrogen, and progesterone systems.

Strategies to Reduce Microplastic Exposure:

• Water:
• Avoid drinking water from plastic bottles or aluminum cans which are plastic lined, both can leach microplastics and BPA into your water.
• At home install a water filter that can eliminate microplastics in your tap water, use glass or metal water bottles when away from home.
• Food:
• Choose rock salts over sea salts, which have been shown to contain more microplastics.
• Choose fresh, non-processed food.
• Limit canned foods, the aluminum can is often lined with plastic. Look for glass packaging.
• Avoid food packaged in microwave ready containers, heating will release more microplastics into the food.
• Store food in glass or metal containers.
• Use non-plastic wraps and baggies—beeswax paper, compostable bags

• Kitchen:
• Exchange plastic cutting boards for stainless steel, wood, marble, or bamboo cutting boards,
• Avoid non-stick cookware which can leach PFAS into your food,
• Avoid plastic utensils and kitchenware, instead use metal, glass or wooden options.
• Switch to a glass or stainless steel blender, plastic blenders have been shown to release microplastics into food due to force of blending.
• When microwaving food, use glass containers rather than plastic or to-go containers to prevent release of microplastic into your food. Don’t microwave with plastic wrap.

• House:
• Regularly dust, vacuum and mop to cut down on airborne microplastic fibers.
• Don’t wear shoes in the house.
• Install a HEPA air filter and HEPA vacuum filter can improve your indoor air quality.
• Choose non-plastic toys, especially baby toys which often go in the mouth.

• Laundry:
• Opt for natural fibers in your clothing, if you have synthetic fabrics use a microfiber filter or wash synthetic clothes in a microplastic trapping laundry bag.

• Bathroom:
• Review personal care products and look for BPA and phthalate free, or microplastic free labels.

• Travel:
• Paper coffee and tea cups are lined with plastic and the heat from the beverage releases more microplastics into your drink. Many coffee shops will fill your own travel mug.
• Receipts on thermal paper can be a source of BPA by absorption through your skin, opt for no receipt or a digital receipt when possible. Using hand sanitizer or lotion right before handling a receipt has been shown to increase BPA absorption.

References

Afreen et al. Adverse health effects and mechanisms of microplastics on female reproductive system: a descriptive review. Environ Sci Pollut Res Int. 2023 Jul;30(31):76283-76296. doi: 10.1007/s11356-023-27930-1. PMID: 37247153

Berger et al. Association of Prenatal Urinary Concentrations of Phthalates and Bisphenol A and Pubertal Timing in Boys and Girls. Environ Health Perspect. 2018 Sep;126(9):97004. doi: 10.1289/EHP3424. PMID: 30203993

Campen et al. Bioaccumulation of Microplastics in Decedent Human Brains Assessed by Pyrolysis Gas Chromatography-Mass Spectrometry. Res Sq [Preprint]. 2024 May 6. doi: 10.21203/rs.3.rs-4345687/v1. PMID: 38765967

Hafezi et al. The Endocrine Disruptor Bisphenol A (BPA) Exerts a Wide Range of Effects in Carcinogenesis and Response to Therapy. Curr Mol Pharmacol. 2019;12(3):230-238. PMID: 30848227

Landrigan et al. The Minderoo-Monaco Commission on Plastics and Human Health. Ann Glob Health. 2023 Mar 21;89(1):23. PMID: 36969097

Patrick, Rhonda. (2024) “What Microplastics are doing to the Brain, Body, and Reproductive Systems” https://www.foundmyfitness.com/episodes/microplastics

Swan et al. Study for Future Families Research Team. Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environ Health Perspect. 2005 Aug;113(8):1056-61. PMID: 16079079

Swan et al. TIDES Study Team. First trimester phthalate exposure and anogenital distance in newborns. Hum Reprod. 2015 Apr;30(4):963-72. PMID: 25697839

Zhang et al. Microplastics May Be a Significant Cause of Male Infertility. Am J Mens Health. 2022 May-Jun;16(3):15579883221096549. doi: 10.1177/15579883221096549. PMID: 35608037