It's all around us—in our houses, walls, plumbing pipes, bottles and cans, rugs, dental fillings, eyeglass lenses, phones, cars, garden mulch and much more. We are talking, of course, about plastic.
Aside from the devastating impact on the planet's health, plastic's impact on human health has been insidious. Decade after decade we have watched as prostate and breast cancer rates have risen, fertility rates in men have dropped, young girls have entered early puberty, young boys have become increasingly hyperactive and children have become fatter. All of these conditions result from multiple factors, but the effects of plastic cannot be discounted.
Endocrine disruptors are the link between human health hazards and plastic. Some of the better publicized endocrine disruptors include dioxins and PCBs, which have polluted our nation's waterways. In the human body, endocrine disruptors mimic the actions of the hormone estrogen. They upset the hormonal balance and can stimulate the growth of tumors in the breast, uterus or prostate. They can affect fertility, pregnancy, and worse, can affect the fetus by interfering with testosterone, disrupting normal sexual development. This disruption is not often apparent until adulthood and includes the increased risk of cancer.
One of the main chemicals used to produce plastics is bisphenol A, or BPA, an endocrine disruptor that is prevalent in a vast number of widely used products, not least of which are plastic food and beverage bottles and the lining of metal cans. Heat, repeated washing, acidity, and alkalinity cause the BPA in plastics to leach into our food and beverages. Further, BPA leaches into our groundwater from all the plastic sitting in landfills. And of course we ingest BPA from all the fish we eat that has previously ingested all that plastic floating around in the ocean.
In one study, the Centers for Disease Control found 95 percent of urine samplescontained some amount of BPA. It's in our blood, our amniotic fluid, our breast milk. Small children are most at risk because they put everything in their mouths, they breathe and drink more, relative to their size, and they excrete waste more slowly.
The health risks of BPA have been observed primarily through animal testing, and there is some controversy as to whether human risk can be extrapolated from animal testing. However, many of the adverse effects of BPA, such as reproductive cancers, obesity, type-2 diabetes and even autism, have been observed to be increasing in the human population in the past 50 years, mirroring the rise of plastic consumption. While correlation is not causation, the signs are certainly not encouraging.
Although the U.S. Food and Drug Administration has maintained that the levels of BPA are safe, Sarah Janssen of the Natural Resources Defense Council told Mother Earth News, “BPA should be considered a hazard to human development and reproduction with clear evidence of adverse effects." Many countries, including the U.S., have banned the presence of BPA in baby bottles. Unfortunately, the common substitute is often Biphenol S (BPS), which is also an endocrine disruptor and seems to cause many of the same problems as BPA.
Polycarbonate water bottles, popular among those who seek to minimize plastic pollution, are a major source of human BPA exposure. Studies have shown that BPA leaches into water even at room temperature, and when exposed to boiling water, BPA leached 55 times more rapidly than it did prior to exposure to the heat.
Another class of endocrine disruptor called phthalates is also present in plastic products containing PVC. Phthalates are used to soften plastic and can be found in toys, deodorants and shampoos, shower curtains, raincoats, food packaging and a myriad of other products. Phthalates are loosely bound to plastic and easily absorbed into food, beverages and saliva, and like BPA, have been commonly detected in our bodies. Most concerning is the effect phthalates have on reproductive health in males. Exposure in fetuses has been linked to the malformation of the male reproductive system.
The dangers from plastic are not just from ingestion. During the industrial manufacturing of plastic, all manner of toxic chemicals are released, many of which are carcinogenic or neurotoxic. These would include vinyl chloride, from PVC; dioxins and benzene, from polystyrene; and formaldehyde, from polycarbonates. Many of these toxins are known as POPs, or persistent organic pollutants. They are highly toxic, and like plastic, they don't easily go away.
Plastic comes in many variations, different combinations of resins and polymers creating plastics with different properties, and different types of plastic present different dangers. The numbers embedded on most plastic products identify the type of plastic it is made from, ostensibly so it can be properly recycled. (The reality is that barely 10 percent of plastic is recycled, or more accurately down-cycled, say from a soda bottle to winter coat insulation, so it still ends up in a landfill.)
Here are the most common plastics, by number, and some of the hazards they present.
1. PET: polyethylene terephthalate
PET is commonly used in commercially sold water bottles, soft drink bottles, sports drink bottles and condiment bottles (like ketchup). While it is generally considered a “safe" plastic, and does not contain BPA, in the presence of heat it can leach antimony, a toxic metalloid, into food and beverages, which can cause vomiting, diarrhea and stomach ulcers. Some studies have shown up to 100 times the amount of antimony in bottled water than in clean groundwater. The longer the bottle is on the shelf or exposed to heat or sunshine, the more antimony is likely to have leached into the product.
2. HDPE: high-density polyethylene
HDPE is commonly used in milk and juice bottles, detergent bottles, shampoo bottles, grocery bags, and cereal box liners. Like PET, it is also considered “safe," but has been shown to leach estrogenic chemicals dangerous to fetuses and juveniles.
3. PVC: polyvinyl chloride
PVC can be flexible or rigid, and is used for plumbing pipes, clear food packaging, shrink wrap, plastic children's toys, tablecloths, vinyl flooring, children's play mats, and blister packs (such as for medicines). PVC contains a phthalate called DEHP, which can cause male traits to become more feminized (DEHP-containing products have been banned in many countries, but not the U.S.). In some products, DEHP has been replaced with another chemical called DiNP, which has similarly been shown to have hormone disruption properties.
4. LDPE: low-density polyethylene
LDPE is used for dry cleaning bags, bread bags, newspaper bags, produce bags, and garbage bags, as well as “paper" milk cartons and hot/cold beverage cups. LDPE does not contain BPA, but as with most plastics, it can leach estrogenic chemicals.
5. PP: polypropylene
PP is used to make yogurt containers, deli food containers and winter clothing insulation. PP actually has a high heat tolerance and as such, does not seem to leach many of the chemicals other plastics do.
6. PS: polystyrene
PS, also popularly known as Styrofoam, is used for cups, plates, take-out containers, supermarket meat trays, and packing peanuts. Polystyrene can leach styrene, a suspected carcinogen, especially in the presence of heat (which makes hot coffee in a Styrofoam container an unwise choice).
7. Everything else
Any plastic item not made from the above six plastics is lumped together as a #7 plastic. Any plastic designated #7 is likely to leach BPA and/or BPS, both potent endocrine disruptors linked to interfering with proper mood, growth, development, sexual function, reproductive function, and puberty, among other essential human developmental processes. They are also suspected of increasing the risk of adult reproductive cancers, obesity, heart disease, and type 2 diabetes.
The Dangers of Outgassing
The danger from chemicals in plastic is not limited to leaching from bottles and food wraps. Another significant source of concern is from outgassing (also known as offgassing). That new-car smell, or the odor from a new synthetic-fiber carpet or new plastic toy is actually called outgassing.
What is chemically happening is that volatile organic compounds (VOCs) are evaporating into the air around us. These gases are, in many cases, hazardous to human health.
These VOCs include aldehydes, alcohols, plasticizers, and alkanes. PVC is probably the worst outgassing offender and is prevalent throughout the household. A buildup of VOCs in the household (sometimes called sick building syndrome) can result in symptoms such as dizziness, nausea, allergies, skin/eye/nose/throat irritations, and asthma. Long-term damage can include cancer and heart disease. Heat can speed up the process of outgassing, so it may be helpful to put new products containing plastic out in the sun for a few hours to minimize the indoor VOC buildup.
The ABCs of Avoiding Plastics
The obvious solution to avoiding plastic toxicity is to avoid plastics, which, in a world awash in plastic, is pretty difficult. In the absence of this, it makes sense to limit your close encounters with plastic as best as you can.
- Never heat or microwave your food in plastic containers, which increases the leaching of chemicals.
- Avoid contact with BPA by avoiding plastic wrap (use wax or parchment paper, or aluminum foil), plastic food containers (use metal or glass containers), and disposable water bottles (use reusable non-plastic or BPA-free bottles).
- Look for BPA-free on the label of products (while this is not a guarantee of safety, it at least limits BPA exposure). Use metal and wooden eating and cooking utensils instead of plastic utensils.
- Find food and water containers that are BPA-free. Avoid phthalates by primarily avoiding PVC products (labeled as #3 plastic).
- Look for phthalates-free labels.
- When possible, air new plastic products like blowup mattresses, synthetic-fiber rugs, tablecloths, and toys outside for a few hours to let the VOCs disperse.
- Avoid plastics numbered #6 and #7 whenever possible.
Larry Schwartz is a Brooklyn-based freelance writer with a focus on health, science and American history.
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By Ana Maldonado-Contreras
- Your gut is home to trillions of bacteria that are vital for keeping you healthy.
- Some of these microbes help to regulate the immune system.
- New research, which has not yet been peer-reviewed, shows the presence of certain bacteria in the gut may reveal which people are more vulnerable to a more severe case of COVID-19.
You may not know it, but you have an army of microbes living inside of you that are essential for fighting off threats, including the virus that causes COVID-19.
How Do Resident Bacteria Keep You Healthy?<p>Our immune defense is part of a complex biological response against harmful pathogens, such as viruses or bacteria. However, because our bodies are inhabited by trillions of mostly beneficial bacteria, virus and fungi, activation of our immune response is tightly regulated to distinguish between harmful and helpful microbes.</p><p>Our bacteria are spectacular companions diligently helping prime our immune system defenses to combat infections. A seminal study found that mice treated with antibiotics that eliminate bacteria in the gut exhibited an impaired immune response. These animals had low counts of virus-fighting white blood cells, weak antibody responses and poor production of a protein that is vital for <a href="https://doi.org/10.1073/pnas.1019378108" target="_blank">combating viral infection and modulating the immune response</a>.</p><p><a href="https://doi.org/10.1371/journal.pone.0184976" target="_blank" rel="noopener noreferrer">In another study</a>, mice were fed <em>Lactobacillus</em> bacteria, commonly used as probiotic in fermented food. These microbes reduced the severity of influenza infection. The <em>Lactobacillus</em>-treated mice did not lose weight and had only mild lung damage compared with untreated mice. Similarly, others have found that treatment of mice with <em>Lactobacillus</em> protects against different <a href="https://doi.org/10.1038/srep04638" target="_blank" rel="noopener noreferrer">subtypes of</a> <a href="https://doi.org/10.1038/s41598-017-17487-8" target="_blank" rel="noopener noreferrer">influenza</a> <a href="https://doi.org/10.1371/journal.ppat.1008072" target="_blank" rel="noopener noreferrer">virus</a> and human respiratory syncytial virus – the <a href="https://doi.org/10.1038/s41598-019-39602-7" target="_blank" rel="noopener noreferrer">major cause of viral bronchiolitis and pneumonia in children</a>.</p>
Chronic Disease and Microbes<p>Patients with chronic illnesses including Type 2 diabetes, obesity and cardiovascular disease exhibit a hyperactive immune system that fails to recognize a harmless stimulus and is linked to an altered gut microbiome.</p><p>In these chronic diseases, the gut microbiome lacks bacteria that activate <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">immune cells</a> that block the response against harmless bacteria in our guts. Such alteration of the gut microbiome is also observed in <a href="https://doi.org/10.1073/pnas.1002601107" target="_blank" rel="noopener noreferrer">babies delivered by cesarean section</a>, individuals consuming a poor <a href="https://doi.org/10.1038/nature12820" target="_blank" rel="noopener noreferrer">diet</a> and the <a href="https://doi.org/10.1038/nature11053" target="_blank" rel="noopener noreferrer">elderly</a>.</p><p>In the U.S., 117 million individuals – about half the adult population – <a href="https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/" target="_blank" rel="noopener noreferrer">suffer from Type 2 diabetes, obesity, cardiovascular disease or a combination of them</a>. That suggests that half of American adults carry a faulty microbiome army.</p><p>Research in my laboratory focuses on identifying gut bacteria that are critical for creating a balanced immune system, which fights life-threatening bacterial and viral infections, while tolerating the beneficial bacteria in and on us.</p><p>Given that diet affects the diversity of bacteria in the gut, <a href="https://www.umassmed.edu/nutrition/melody-trial-info/" target="_blank" rel="noopener noreferrer">my lab studies show how diet can be used</a> as a therapy for chronic diseases. Using different foods, people can shift their gut microbiome to one that boosts a healthy immune response.</p><p>A fraction of patients infected with SARS-CoV-2, the virus that causes COVID-19 disease, develop severe complications that require hospitalization in intensive care units. What do many of those patients have in common? <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e2.htm" target="_blank" rel="noopener noreferrer">Old age</a> and chronic diet-related diseases like obesity, Type 2 diabetes and cardiovascular disease.</p><p><a href="http://doi.org/10.1016/j.jada.2008.12.019" target="_blank" rel="noopener noreferrer">Black and Latinx people are disproportionately affected by obesity, Type 2 diabetes and cardiovascular disease</a>, all of which are linked to poor nutrition. Thus, it is not a coincidence that <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6933e1.htm" target="_blank" rel="noopener noreferrer">these groups have suffered more deaths from COVID-19</a> compared with whites. This is the case not only in the U.S. but also <a href="https://www.washingtonpost.com/world/europe/blacks-in-britain-are-four-times-as-likely-to-die-of-coronavirus-as-whites-data-show/2020/05/07/2dc76710-9067-11ea-9322-a29e75effc93_story.html" target="_blank" rel="noopener noreferrer">in Britain</a>.</p>
Discovering Microbes That Predict COVID-19 Severity<p>The COVID-19 pandemic has inspired me to shift my research and explore the role of the gut microbiome in the overly aggressive immune response against SARS-CoV-2 infection.</p><p>My colleagues and I have hypothesized that critically ill SARS-CoV-2 patients with conditions like obesity, Type 2 diabetes and cardiovascular disease exhibit an altered gut microbiome that aggravates <a href="https://theconversation.com/exercise-may-help-reduce-risk-of-deadly-covid-19-complication-ards-136922" target="_blank" rel="noopener noreferrer">acute respiratory distress syndrome</a>.</p><p>Acute respiratory distress syndrome, a life-threatening lung injury, in SARS-CoV-2 patients is thought to develop from a <a href="http://doi.org/10.1016/j.cytogfr.2020.05.003" target="_blank" rel="noopener noreferrer">fatal overreaction of the immune response</a> called a <a href="https://theconversation.com/blocking-the-deadly-cytokine-storm-is-a-vital-weapon-for-treating-covid-19-137690" target="_blank" rel="noopener noreferrer">cytokine storm</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">that causes an uncontrolled flood</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">of immune cells into the lungs</a>. In these patients, their own uncontrolled inflammatory immune response, rather than the virus itself, causes the <a href="http://doi.org/10.1007/s00134-020-05991-x" target="_blank" rel="noopener noreferrer">severe lung injury and multiorgan failures</a> that lead to death.</p><p>Several studies <a href="https://doi.org/10.1016/j.trsl.2020.08.004" target="_blank" rel="noopener noreferrer">described in one recent review</a> have identified an altered gut microbiome in patients with COVID-19. However, identification of specific bacteria within the microbiome that could predict COVID-19 severity is lacking.</p><p>To address this question, my colleagues and I recruited COVID-19 hospitalized patients with severe and moderate symptoms. We collected stool and saliva samples to determine whether bacteria within the gut and oral microbiome could predict COVID-19 severity. The identification of microbiome markers that can predict the clinical outcomes of COVID-19 disease is key to help prioritize patients needing urgent treatment.</p><p><a href="https://doi.org/10.1101/2021.01.05.20249061" target="_blank" rel="noopener noreferrer">We demonstrated</a>, in a paper which has not yet been peer reviewed, that the composition of the gut microbiome is the strongest predictor of COVID-19 severity compared to patient's clinical characteristics commonly used to do so. Specifically, we identified that the presence of a bacterium in the stool – called <em>Enterococcus faecalis</em>– was a robust predictor of COVID-19 severity. Not surprisingly, <em>Enterococcus faecalis</em> has been associated with <a href="https://doi.org/10.1053/j.gastro.2011.05.035" target="_blank" rel="noopener noreferrer">chronic</a> <a href="https://doi.org/10.1016/S0002-9440(10)61172-8" target="_blank" rel="noopener noreferrer">inflammation</a>.</p><p><em>Enterococcus faecalis</em> collected from feces can be grown outside of the body in clinical laboratories. Thus, an <em>E. faecalis</em> test might be a cost-effective, rapid and relatively easy way to identify patients who are likely to require more supportive care and therapeutic interventions to improve their chances of survival.</p><p>But it is not yet clear from our research what is the contribution of the altered microbiome in the immune response to SARS-CoV-2 infection. A recent study has shown that <a href="https://doi.org/10.1101/2020.12.11.416180" target="_blank" rel="noopener noreferrer">SARS-CoV-2 infection triggers an imbalance in immune cells</a> called <a href="https://doi.org/10.1111/imr.12170" target="_blank" rel="noopener noreferrer">T regulatory cells that are critical to immune balance</a>.</p><p>Bacteria from the gut microbiome are responsible for the <a href="https://doi.org/10.7554/eLife.30916.001" target="_blank" rel="noopener noreferrer">proper activation</a> <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">of those T-regulatory</a> <a href="https://doi.org/10.1038/nri.2016.36" target="_blank" rel="noopener noreferrer">cells</a>. Thus, researchers like me need to take repeated patient stool, saliva and blood samples over a longer time frame to learn how the altered microbiome observed in COVID-19 patients can modulate COVID-19 disease severity, perhaps by altering the development of the T-regulatory cells.</p><p>As a Latina scientist investigating interactions between diet, microbiome and immunity, I must stress the importance of better policies to improve access to healthy foods, which lead to a healthier microbiome. It is also important to design culturally sensitive dietary interventions for Black and Latinx communities. While a good-quality diet might not prevent SARS-CoV-2 infection, it can treat the underlying conditions related to its severity.</p><p><em><a href="https://theconversation.com/profiles/ana-maldonado-contreras-1152969" target="_blank">Ana Maldonado-Contreras</a> is an assistant professor of Microbiology and Physiological Systems at the University of Massachusetts Medical School.</em></p><p><em>Disclosure statement: Ana Maldonado-Contreras receives funding from The Helmsley Charitable Trust and her work has been supported by the American Gastroenterological Association. She received The Charles A. King Trust Postdoctoral Research Fellowship. She is also member of the Diversity Committee of the American Gastroenterological Association.</em></p><p><em style="">Reposted with permission from <a href="https://theconversation.com/a-healthy-microbiome-builds-a-strong-immune-system-that-could-help-defeat-covid-19-145668" target="_blank" rel="noopener noreferrer" style="">The Conversation</a>. </em></p>
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