Environmental toxins that find their way into our air, food, and water over the past few decades have dramatically increased. Many of these substances have adverse health effects in both humans and animals that may account for the increase of cancer, including an increase in colon cancer in younger age groups. The following article that appeared in a recent issue of Medscape for Physicians summarizes the toxicology and dangers of several of the more common environmental adulterants.
If the pandemic served as a window into our health, what it revealed was a US population that is not only sick but also seemingly only getting sicker. Life expectancy is falling precipitously. Three fourths of Americans are overweight or obese, half have diabetes or prediabetes, and a majority are metabolically unhealthy. Furthermore, the rates of allergic, inflammatory, and autoimmune diseases are rising at rates of 3%-9% per year in the West, far faster than the speed of genetic change in this population.
Of course, diet and lifestyle are major factors behind such trends, but a grossly underappreciated driver in what ails us is the role of environmental toxins and endocrine-disrupting chemicals. In years past, these factors have largely evaded the traditional Western medical establishment; however, mounting evidence now supports their significance in fertility, metabolic health, and cancer.
Although several industrial chemicals and toxins have been identified as carcinogens and have subsequently been regulated, many more remain persistent in the environment and continue to be freely used. It is therefore incumbent upon both the general public and clinicians to be knowledgeable about these exposures. Here, we review some of the most common exposures and the substantial health risks associated with them, along with some general guidance around best practices for how to minimize exposure.
Microplastics
"Microplastics" is a term used to describe small fragments or particles of plastic breakdown or microbeads from household or personal care products, measuring less than 5 mm in length.
Plastic waste is accumulating at alarming and devastating proportions — by 2050, it is estimated that by weight, there will be more plastic than fish in the oceans. That translates into hundreds of thousands of tons of microplastics and trillions of these particles in the seas. A recent study demonstrated that microplastics were present in the bloodstream in the majority of 22 otherwise healthy participants.
Since the 1950s, plastic exposure has been shown to promote tumorigenesis in animal studies, and in vitro studies have demonstrated the toxicity of microplastics at the cellular level. However, it is not well known whether the plastic itself is toxic or if it simply serves as a carrier for other environmental toxins to bioaccumulate.
According to Tasha Stoiber, a senior scientist at the Environmental Working Group (EWG), "Microplastics have been widely detected in fish and seafood, as well as other products like bottled water, beer, honey, and tap water." EWG states there are no formal advisories on fish consumption to avoid exposure to microplastics at the moment.
Pressure also is mounting for a ban on microbeads in personal care products.
Until such bans are put in place, it is advised to avoid single-use plastics, favor reusable tote bags for grocery shopping rather than plastic bags, and opt for loose leaf tea or paper tea bags rather than mesh-based alternatives.
Phthalates
Phthalates are chemicals used to make plastics soft and durable, as well as to bind fragrances. They are commonly found in household items such as vinyl (eg, flooring, shower curtains) and fragrances, air fresheners, and perfumes.
Phthalates are known hormone-disrupting chemicals, exposure to which has been associated with abnormal sexual and brain development in children, as well as lower levels of testosterone in men. Exposures are thought to occur via inhalation, ingestion, and skin contact; however, fasting studies demonstrate that a majority of exposure is probably food related.
To avoid phthalate exposures, recommendations include avoiding polyvinyl chloride plastics (particularly food containers, plastic wrap, and children's toys), which is identifiable by the recycle code number 3, as well as air fresheners and fragranced products.
The EWG's Skin Deep database provides an important resource on phthalate-free personal care products.
Despite pressure from consumer advocacy groups, the US Food and Drug Administration has not yet banned phthalates in food packaging.
Bisphenol A (BPA)
BPA is a chemical additive used to make clear and hard polycarbonate plastics, as well as epoxy and thermal papers. BPA is one of the highest-volume chemicals, with roughly 6 billion pounds produced each year. BPA is traditionally found in many clear plastic bottles and sippy cups, as well as in the lining of canned foods.
Structurally, BPA acts as an estrogen mimetic and has been associated with cardiovascular disease, obesity, and male sexual dysfunction. Since 2012, BPA has been banned in sippy cups and baby bottles, but there is some debate as to whether its replacements (bisphenol S and bisphenol F) are any safer; they appear to have similar hormonal effects as BPA.
As with phthalates, the majority of ingestion is thought to be food related. BPA has been found in more than 90% of a representative study population in the United States.
Guidance advises avoiding polycarbonate plastics (identifiable with the recycling code number 7), as well as avoiding handling thermal papers such as tickets and receipts, if possible. Food and beverages should be stored in glass or stainless steel. If plastic must be used, opt for polycarbonate- and polyvinyl chloride–free plastics, and food and beverage should never be reheated in plastic containers or wrapping. Canned foods should ideally be avoided, particularly canned tunas and condensed soups. If canned products are bought, they should ideally be BPA free.
Dioxins and Polychlorinated Biphenyls (PCBs)
Dioxins are mainly the byproducts of industrial practices; they are released after incineration, trash burning, and fires. PCBs, which are somewhat structurally related to dioxins, were previously found in products such as flame retardants and coolants. Dioxins and PCBs are often grouped in the same category under the umbrella term "persistent organic pollutants" because they break down slowly and remain in the environment even after emissions have been curbed.
Tetrachlorodibenzodioxin, perhaps the best-known dioxin, is a known carcinogen. Dioxins also have been associated with a host of health implications in development, immunity, and reproductive and endocrine systems. Higher levels of PCB exposure have also been associated with an increased risk for mortality from cardiovascular disease.
Notably, dioxin emissions have been reduced by 90% since the 1980s, and the US Environmental Protection Agency (EPA) has banned the use of PCBs in industrial manufacturing since 1979. However, environmental dioxins and PCBs still enter the food chain and accumulate in fat.
The best ways to avoid exposures are through limiting meat, fish, and dairy consumption and trimming the skin and fat from meats. The level of dioxins and PCBs found in meat, eggs, fish, and dairy are approximately 5-10 times higher than they are in plant-based foods. Research has shown that farmed salmon is likely to be the most PCB-contaminated protein source in the US diet; however, newer forms of land-based and sustainable aquaculture probably avoid this exposure.
Pesticides
The growth of modern monoculture agriculture in the United States over the past century has coincided with a dramatic surge in the use of industrial pesticides. In fact, over 90% of the US population have pesticides in their urine and blood, regardless of where they live. Exposures are thought to be food related.
Approximately 1 billion pounds of pesticides are used annually in the United States, including nearly 300 million pounds of glyphosate, which has been identified as a probable carcinogen by European agencies. The EPA has not yet reached this conclusion, although the matter is currently being litigated.
A large European prospective cohort trial demonstrated a lower risk for cancer in those with a greater frequency of self-reported organic food consumption. In addition to cancer risk, relatively elevated blood levels of a pesticide known as beta-hexachlorocyclohexane (B-HCH) are associated with higher all-cause mortality. Also, exposure to DDE — a metabolite of DDT, a chlorinated pesticide heavily used in the 1940s-1960s that still persists in the environment today — has been shown to increase the risk for Alzheimer's-type dementia as well as overall cognitive decline.
Because these chlorinated pesticides are often fat soluble, they seem to accumulate in animal products. Therefore, people consuming a vegetarian diet have been found to have lower levels of B-HCH. This has led to the recommendation that consumers of produce should favor organic over conventional, if possible. Here too, the EWG provides an important resource to consumers in the form of shopper guides regarding pesticides in produce.
Per- and Polyfluoroalkyl Substances (PFAS)
PFAS are a group of fluorinated compounds discovered in the 1930s. Their chemical composition includes a durable carbon-fluoride bond, giving them a persistence within the environment that has led to their being referred to as "forever chemicals."
PFAS have been detected in the blood of 98% of Americans, and in the rainwater of locations as far afield as Tibet and Antarctica. Even low levels of exposure have been associated with an increased risk for cancer, liver disease, low birthweight, and hormonal disruption.
The properties of PFAS also make them both durable at very high heat and water repellent. Notoriously, the chemical was used by 3M to make Scotchgard for carpets and fabrics and by Dupont to make Teflon for nonstick coating of pots and pans. Although perfluorooctanoic acid (PFOA) was removed from nonstick cookware in 2013, PFAS — a family of thousands of synthetic compounds — remain common in fast-food packaging, water- and stain-repellent clothing, firefighting foam, and personal care products. PFAS are released into the environment during the breakdown of these consumer and industrial products, as well as from dumping from waste facilities.
Alarmingly, the EWG notes that up to 200 million Americans may be exposed to PFAS in their drinking water. In March 2021, the EPA announced that they will be regulating PFAS in drinking water; however, the regulations have not been finalized. Currently, it is up to individual states to test for its presence in the water. The EWG has compiled a map of all known PFAS contamination sites.
To avoid or prevent exposures from PFAS, recommendations include filtering tap water with either reverse osmosis or activated carbon filters, as well as avoiding fast food and carry-out food, if possible, and consumer products labeled as "water resistant," "stain-resistant," and "nonstick."
In a testament to how harmful these chemicals are, the EPA recently revised their lifetime health advisories for PFAS, such as PFOA, to 0.004 parts per trillion, which is more than 10,000 times smaller than the previous limit of 70 parts per trillion. The EPA also has proposed formally designating certain PFAS chemicals as "hazardous substances."
