Plastics have been associated with disturbances in the endocrine system, which in a broader sense can be related to problems with reproduction, cancers, thyroid, obesity, metabolism and neurodevelopment.
What are Endocrine Disruptors?
While many chemicals, both natural and man-made, may mimic or interfere with our hormones, some have become so common in our day to day lives, that they have warranted special investigation and review. Called "endocrine disruptors", these chemicals are linked with developmental, metabolic, reproductive, brain, immune, and other problems1 in different organs and glands of the endocrine system, which is the hormone-based communication network in the body. Endocrine disruptors include bisphenol A, dioxins, perchlorate, perfluoroalkyl and polyfluoroalkyl substances (PFAS), phthalates, phytoestrogens, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and triclosan, among others.
Though plastics are certainly not the only compounds of concern on this topic, they are accumulating at such massive levels in our environments globally as well as in our own bodies, that they should be of particular interest. Indeed, bits of plastic dust have been floating around our environment for as long as humans have been using plastic. This has been measured with some sobering results; for example, in the western United States, samples taken from 11 different national park lands found that plastic airborne dust was accumulating to the tune of more than 1,000 metric tons of microplastics—the weight of 120 million to 300 million plastic water bottles, falling from the sky each year.2 And small forms of them, called 'microplastics', have recently been found in the blood, lungs, and placenta of live humans!3,4,5
Spotlight on PLASTICS
"I want to say just one word to you, just one word. Are you listening? Plastics."
It's been over 50 years since that famous scene with Dustin Hoffman in the 1967 classic film, The Graduate. And he was definitely right!
Plastics are synthetic substances composed of many repeating organic units which can be molded into shape while soft but then take on harder properties with varying levels of elasticity once fully cured. Some of the components of plastics that have been shown to have negative effects on health include:
Bisphenol A (BPA) - BPA was originally designed to be a synthetic estrogen, similar to diethylstibestrol (DES), another endocrine-disrupting chemical prescribed in the United States until the 1970s and was found to be associated with multiple types of reproductive cancers. BPA is currently used to make polycarbonate plastics and epoxy resins, which are found in many plastic products including food storage containers, from where it can leach into food consumed by people. It has been in food packaging products since the 1960s. BPA is also used in production of polycarbonate tableware, water bottles, coatings for thermal receipt paper and baby bottles. The degree to which BPA leaches from polycarbonate bottles into liquid may depend more on the temperature of the liquid or bottle, than the age of the container.6 BPA can also be found in most samples of human breast milk studied and as much as 93% of a healthy infant population urine samples, aged 3–15 months, who were without known environmental exposure to BPA.7
Phthalates - Ortho-phthalates, called just 'phthalates' for short, are used to make plastics more flexible. Overwhelming abundant in modern manufacturing, they appear in numerous consumer products including food production materials, plastic wraps, and packaging, medical supplies and coatings of medicines, flooring, wall coverings, and other home materials, as well as cosmetics and other personal care products. Approximately 4.9 million metric tons are produced annually worldwide.8 Regrettably, as mounting evidence of neurotoxicity from exposure has developed, sometimes manufacturers have simply substituted one implicated phthalate for another similar compound which has not yet achieved a burden of proof.9
Polybrominated diphenyl ethers (PBDEs) - PBDEs are a class of flame retardants used for household products such as furniture foam, textiles and carpets. They are also used in electronics and plastics to reduce the risk of ignition and slow down burning rates. PBDEs have been shown to leach into the surrounding environment and have been globally detected in soil, sediment, food, and air.10 Measures of PBDEs in house dust indicate widespread contamination in homes and house dust may be an important human exposure pathway.11 Though some types of PBDEs were voluntarily discontinued for production in the U.S. in 2004 and again in 2013 after intense scientific scrutiny and concern, other types, such as DecaBDE continue to be produced and used in the U.S., primarily in television casings. DecaBDE is classified as a possible human carcinogen by the U.S. Environmental Protection Agency.12 Is it any wonder then that "[i]n the U.S., PBDE levels in people are generally 10–100 times higher than levels measured in people in Europe and Asia".12
Bisphenol S (BPS) - BPS is a common replacement for BPA and found in plastic bottles labeled 'BPA free". It is still used in water bottles and sippy cups, but also thermal paper coatings and many other applications where BPA is often used. The scientific literature shows similar toxicology effects on animals as BPA, including metabolic, neurological, respiratory, endocrine, reproductive and behavioral effects as well as the ability to be transferred from mother to child via placenta and milk.13 Though some countries have passed restrictions to the use of BPS, these are largely not present in the United States.
Plastics as Endocrine Disruptors and Effects on Human Health
There are an ever-growing number of animal studies to support all of the associations with health concerns listed below. Many animal studies precede what research gets done with people. And the findings may surprise you!
Infertility:
Infertility is a problem facing many men as well as women. Among different ingredients used in plastics, BPA has drawn a considerable amount of attention on this topic due to its tendency to interact with estrogen receptors, where it acts as an agonist or antagonist. This is largely due to its biochemical arrangement, or 'phenolic structure'. Increased levels of urinary BPA concentration have been shown to correlate with a reduced number of sperm in the ejaculate, as well as reduced motility and viability.14, 15 "The pathomechanism of the fertility disrupting potential of BPA in women as well as in men seems to be due to its estrogenic activity in the hypothalamus which in turn disrupts the proper function of the gonadotropin-releasing hormone (GnRH) pulse generator [and] thus the adequate secretion of the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) is impaired."16
Another way in which BPA can negatively effect fertility is by contributing to polycystic ovary syndrome (PCOS), which is the most common endocrine disorder in premenopausal women. Menstrual irregularities and fertility problems are common among women with PCOS, which often also show physical signs of elevated male hormones, such as facial hair and acne. "Recent observations point to the higher levels of BPA in biological fluids of women with PCOS and its role in the pathogenesis of hyperandrogenism and hyperinsulinemia. It seems that mother's exposure to BPA during pregnancy may also lead to the development of PCOS in the female offspring."17
But BPA is not the only fertility related concern among plastics! In a study published in 2015, several forms of phthalates including urinary mono-n-butyl phthalate (MnBP), mono-(2-ethylhexyl) phthalate (MEHP) and mono-2-ethyl-5-carboxypentyl phthalate were significantly higher among infertile than in fertile men.18
Type 1 Diabetes (T1D):
"Type 1 diabetes (T1D) is an autoimmune disease caused by immune-mediated pancreatic β-cell destruction. The endocrine disrupting chemical bisphenol A (BPA) has widespread human exposure and can modulate immune function and the gut microbiome (GMB), which may contribute to the increasing T1D incidence worldwide".19 Furthermore, some studies have found higher levels of metabolites from phthalates clearly associated and higher among newly diagnosed children with T1D, compared with controls.20
Obesity:
Some research has even linked the increased use of synthetic compounds like PBDEs, phthalates and bisphenol A, with obesity!21 There has been a direct and mutually upward relationship between chemical production and the percentage of overweight adults globally over the last 70 years. This begs the question, as our bodies are being exposed to many different types of endocrine disruptors, of which plastics are only a part, could synthetic chemicals be contributing to altering body
composition? This sheds light on the marked failure of food restriction diets to effect long-term weight loss for many people. For example, several epidemiological studies have found that high urinary concentrations of BPA in adults and children were associated with obesity and increased waist circumference.22
Much of the research on fat and lipid-metabolism diseases has been done on animals. A surprising amount of this has been done on zebrafish(Danio rerio) since, according to a paper published in Nature, 70 per cent of protein-coding human genes are related to genes found in the zebrafish, and 84 per cent of genes known to be associated with human disease have a zebrafish counterpart.23 When studying the effects of multiple endocrine disruptors on zebrafish, including BPA, researchers found liver fat accumulation related to both acute and chronic exposure with dysregulation of lipid-metabolism regulating genes.23. These effects showed up in not just one, but multiple genetic pathways and also resulted in hepatic, or liver, inflammation.
Attention Deficit Hyperactivity Disorder (ADHD):
It has been approximately thirty years since the scientific community acknowledged certain synthetic chemicals are capable of crossing the placental and brain barriers and interfering with development and function. During that time the prevalence of neurodevelopmental disorders such as autism and ADHD has increased dramatically. The proper development of a fetus' neurological system is highly sensitive to hormone signaling from the mother, including the thyroid specifically.24 "If a chemical were to interfere with the commencement of development of the cochlea at 6 weeks through its antithyroid effect, it might also affect other thyroid-sensitive tissues emerging at the same time. This might partly explain the list of irregularities or sequelae of anomalies that fit within the definition of the ADHD and autism syndromes".24
Of the many types of chemicals shown to disrupt endocrine function and have associations with ADHD, those used in the making of plastics have a lot of data. Multiple studies have found associations between prenatal exposure to phthalates and adverse neurological development in offspring.25 A 2020 investigation with over 200 adolescents was the first of its kind to study this age group and use urinary biomarker concentrations for several contaminants.26. The higher the phthalates, the higher the risk of ADHD and worsening of hyperactivity, aggression and conduct problems. A 2016 study looked at the urinary concentrations of BPA for over 400 pediatric participants and found clear correlations of higher amounts of BPA and likelihood of an ADHD diagnosis.27 In both of these studies, boys were considerably more likely than girls to have ADHD. Likewise, a 2017 meta-analysis reviewed over a dozen studies for information about PBDEs and intelligence or ADHD and concluded, you guessed it, "... there was sufficient evidence supporting an association between developmental PBDE exposure and reduced IQ" as well as "moderate" quality data for ADHD connections.27
High Blood Pressure (Hypertension):
Though animal studies on this topic are few and all we have to go by, it is worth noting some findings from 2020 because human data is so limited and, with the new blood pressure guidelines from the American Heart Association, almost half of the United States population has hypertension. In this study published in the Journal of the Endocrine Society, scientists exposed pregnant rats to low levels of saline, BPA, and two BPA alternatives, Bisphenol S (BPS) or Bisphenol F (BPF) and followed the development of their offspring. The offspring were implanted with devices to measure their blood pressure and after measuring the blood pressures at intervals over the next six months, they found systolic (the top number in a blood pressure reading) and diastolic blood pressure (the bottom number) were significantly increased in animals exposed to BPA, BPS and BPF compared with those exposed to saline.29
Ways to Reduce Exposure to Plastics
There are many ways to try and reduce exposure to plastics and minimize their effects on your health and the health of the ones you care about.
Dietary Choices:
BPA and phthalate exposures can be reduced by avoiding canned and packaged foods; also, "[f]oods and dietary patterns associated with healthier food choices (e.g., organic grown/ raised/ caught foods, folic acid supplements, vegetarianism) were generally associated with lower urinary phthalate metabolite and BPA concentrations".30 Foods of animal origin tend to have higher concentrations of phthalates, for example, because those compounds are slightly lipophilic, or 'fat-loving', and can bio-accumulate in fat-containing foods.31 Multiple food monitoring studies have consistently found higher concentrations of phthalates and BPA in meat, meat products, and seafood.32-34
Some vegetables are particularly helpful when it comes to eliminating these chemicals from the body. These foods and beverages are ones that support the liver phase II pathway of sulfation, which is one of the two means through which your liver tries to remove BPA and other components of plastics.35 Beverages that support sulfation include coffee, cocoa, green tea and black tea (for their caffeine content).36 Foods that support sulfation include apple, apricot, artichokes, arugula, asparagus, lentils, peas, oats, barley, cabbage, horseradish, Brussel sprouts, leeks, cress, peaches, spinach, watercress, Brazil nuts, almonds, peanuts, walnuts, ginger, poultry, fish, seafood and meat.36 Glucuronidation is the other phase II pathway of interest in the removal of plastics and foods that support it are largely the same: cruciferous vegetables, coffee, asparagus, peanuts, salmon, shrimp but also grapes, soy, citrus, olives, berries, pomegranate, tomatoes, walnuts, and bean sprouts, among others.36, 39, 16
Food and Liquid Container Choices:
When I write above that exposures can be reduced by avoiding canned and packaged foods, I am not exaggerating. One study was shown to have participants achieve reduced amounts of these compounds after limited consumption of foods packaged and prepared in plastics and cans, and increased concentrations of these chemicals with resumption of packaged food on the menu.37 Choose glass, porcelain or metal water bottles over plastic.
With regard to canned goods, the private non-profit organization called Environmental Working Group (EWG) released a study dating back to analysis of 252 canned food brands in 2014, to find out which of them packed their food into cans coated with BPA-laden epoxy. The findings were published in 2015 and reported companies which omitted BPA, contrasted with ones that continued to include it. Though at this writing the information has become dated, it does provide some initial stepping off point as many of these brands can still be found today.38
Food Preparation:
When you must use plastic, avoid heating your food and beverages in plastic as much as possible (e.g., microwave). Remember from above, more of it will degrade at higher temperatures. This goes for plastic containers with BPA as well as plastic wrap with phthalates. The National Institute of Environmental Health Science clearly states: "Don’t microwave polycarbonate plastic food containers. Polycarbonate is strong and durable, but over time it may break down from over use at high temperatures".6
Avoidance of Fragrances and Phthalate-containing Beauty Products:
The presence of phthalates in self-care and beauty products has been repeatedly reviewed in the past decades by the Federal Drug Administration (FDA), where their recurrent findings "determined that there wasn’t a sound, scientific basis to support taking regulatory action against cosmetics containing phthalates".40 Despite the FDA's information page on phthalates as being noted to be current as of 02/25/2022, more than half of the webpage is dedicated to a survey last updated in 2013, which cautions that: "This survey was intended to monitor trends in the use of phthalates in cosmetics, not as a comprehensive analysis of all cosmetics on the market. The law does not require cosmetic firms to file their formulations with FDA".40
In the absence of much regulatory support or guidance, consider seeking answers from the private non-profit organization Environmental Working Group (EWG) and use of their Skin Deep® website at: https://www.ewg.org/skindeep/ . Per their own self-styled description: "EWG's Skin Deep® cosmetic database gives people practical solutions to protect themselves and their families from everyday exposures to potentially toxic chemicals in personal care and beauty products. Skin Deep®, launched in 2004, lists easy-to-navigate hazard ratings for nearly 70,000 products and 9,000 ingredients on the market. The U.S. government doesn't review the toxicity of products before they're sold. Companies are allowed to use almost any ingredient they wish without regard for how safe they are. The aim of Skin Deep® is to fill in where industry and government leave off".41
Probiotics:
Some strains of probiotics have been studied for their ability to degrade BPA. Ones found to be helpful include Bifidobacterium breve and Lactobacillus casei,42 as well as Bacillus pumilus, which is found in kimchi.43
Liver and Kidney Support:
With thought to supporting the detoxification pathways noted above, consideration could be given to nutritional supplements such as N-acetylcysteine, taurine, calcium D-glucurate, magnesium, molybdenum and a B-Complex.
Unfortunately, with the scope and magnitude of this problem not going away, but only worsening, these considerations should have far-reaching application in nearly every household. Due to the multi-faceted nature of these concerns, working with a naturopathic physician or other qualified professional who is trained in supporting the various organ systems, diagnostics, dietary and supplement interventions is always advisable.
References:
1. Endocrine Disruptors and Your Health. National Institute of Environmental Health Sciences. 2020. May.
2. Brahney, J. et al. Plastic Rain in Protected Areas of the United States. Science. 2020 Jun 12;368(6496):1257-1260.
3. Leslie, H. et al., Discovery and quantification of plastic particle pollution in human blood. Environmental International. 2022. March.
4. Jenner, L. et al., Detection of microplastics in human lung tissue using μFTIR spectroscopy. Science of Total Environment. 2022. Mar 29;831:154907.
5. Ragusa, A., et al. Plasticenta: First evidence of microplastics in human placenta. Environ Int. 2021. January.
8. Engel, S. et al. Neurotoxicity of Ortho-Phthalates: Recommendations for Critical Policy Reforms to Protect Brain Development in Children. Am J Public Health. 2021 Apr;111(4):687-695.
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18. Chang, W.H, et al, Phthalates might interfere with testicular function by reducing testosterone and insulin- like factor 3 levels. Hum Reprod. November 2015.
19. Xu J, et al. 2019. Sex-dependent effects of bisphenol A on type 1 diabetes development in non-obese diabetic (NOD) mice. Arch Toxicol 93(4):997-1008.
20. Castro-Correia, C., et al. Phthalates and type 1 diabetes: is there any link? Environmental Science and Pollution Research. 2018.
21. Baillie-Hamilton, P., et al. Chemical Toxins: A Hypothesis to Explain the Global Obesity Epidemic. The Journal of Alternative and Complementary Medicine. November. 2022.
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23. Sun, L., et al. Differential mechanisms regarding triclosan vs. bisphenol A and fluorene-9- bisphenol induced zebrafish lipid-metabolism disorders by RNA-Seq. Chemosphere. July. 2020.
25. Engel, S., et al. Neurotoxicity of Orth-Phthalates: Recommendations for Critical Policy Reforms to Protect Brain Development in Children. Am J Public Health. April. 2021.
26. Shoaff, J.R., et al. Association of Exposure to Endocrine-Disrupting Chemicals During Adolescence With Attention-Deficit/Hyperactivity-Disorder-Related Behaviors. JAMA Netw Open. August. 2020.
27. Tewar, S., et al. Association of Bisphenol A exposure and Attention-Deficit/Hyperactivity Disorder in a national sample of U.S. children. Environ Res. October. 2016.
28. Lam, J., et al. Developmental PBDE Exposure and IQ/ADHD in Childhood: A Systematic Review and Meta-analysis. Environ Health Perspect. August. 2017.
29. Al Mansi, M.H. et al. SAT-719 Prenatal Exposure to Bisphenol A, S and F Increases Blood Pressure in Female Rats. Journal of the Endocrine Society. May. 2020.
35. Yalcin, Emine B et al. “Bisphenol A sulfonation is impaired in metabolic and liver disease.” Toxicology and applied pharmacology vol. 292 (2016): 75-84.
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38. Environmental Working Group. BPA in Canned Food: Behind the Brand Curtain. 2015
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43. Yamanaka, H. et al. Degradation of Bisphenol A by Bacillus pumilus Isolated from Kimchi, a Traditionally Fermented Food. Appl Biochem Biotechnol. 2007;136(1):39-51.
The content and any recommendations in this article are for informational purposes only. They are not intended to replace the advice of the reader's own licensed healthcare professional or physician and are not intended to be taken as direct diagnostic or treatment directives. Any treatments described in this article may have known and unknown side effects and/or health hazards. Each reader is solely responsible for his or her own healthcare choices and decisions. The author advises the reader to discuss these ideas with a licensed naturopathic physician.