The popularity of mani-pedi culture endangers consumers, salon and spa workers, and manicurists alike via exposure to toxic chemicals with well-defined health consequences

It's no secret that our skin is our largest absorptive organ, and that what we apply topically penetrates its way into our systemic circulation, pervading our every tissue. Our skin is, after all, even at its thickest points, only a few millimeters thick. Although most are aware of the detriment posed by the chemicals in personal care products applied to the skin, which shimmy their way into our cells, tissues, and organs, fingernail polish is oftentimes overlooked, as the nails are perceived as sturdier structures less permeable to chemical agents. However, the capillary bed in the cuticle surrounding the nail, in tandem with solvents that render the nails more absorbent, may lead to increased absorption of the cocktail of chemicals in nail polish which elicit tangible effects upon our physiology.

Formaldehyde

Formaldehyde, for one, is a preservative in nail polish that confers protection against microbial growth. A colorless, water-soluble aldehyde, formaldehyde is a highly reactive substance due to its strong electrophilic properties--meaning that it can steal electrons from biological molecules due to its vacant electron-devoid orbitals, altering the stability and properties of molecules in our bodies as a result.

It is most famous as an embalming and fixation material in anatomy, histology and pathology laboratories, rendering medical students particularly vulnerable during cadaver dissections. It is also derived from cigarette smoke and vehicular exhaust, and is rampant in the construction industry as part of materials such as concrete, plaster, carpet, wallboards, rubber, textiles, plywood, paper, adhesives, dyes, plastics, engineered flooring, insulation, paints, floor finishes, and in the combustion of wood or liquid-based fuels.

Although these industrial uses are better known, few realize that formaldehyde sneaks into cosmetics, toothpaste, deodorants, hair care, and other personal care products such as nail polish. Not only is it classified as a known human carcinogen, but it also induces changes to the respiratory tract (1). In mouse models, it induces asthmatic symptoms (2) and early Alzheimer's-like changes (3). Researchers in the Turkish Journal of Urology state,

"FA [formaldehyde], which causes an increase in cytotoxic effects by compromising the intracellular balance, has a strong tendency to combine with proteins, nucleic acids (DNA and RNA) and unsaturated fatty acids by non-enzymatic processes. These combinations result in inflammatory reactions, allergic reactions, cytotoxicity, necrosis and mutagenic and carcinogenic effects by developing denaturation in proteins. Moreover, free oxygen radicals are increased in the tissues affected by FA, and this increase accelerates the processes (apoptosis or necrosis) that cause cell death" (1).

Toluene

The sweet, pungent scent typical of many nail polishes is created by the chemical toluene, an industrial solvent that is also the most widely abused inhaled volatile drug in consumer products such as lacquers, glues, paint thinners, adhesives and industrial cleaning products. Acute exposure to toluene vapors, the effects of which have been studied in humans who abuse spray paint and similar substances, is associated with rhabdomyolysis, acute hepatorenal injury, and profound metabolic acidemia (4). It is also linked to teratogenicity, meaning that its use in pregnant women can impair normal development of the fetus (5).

Most notably, however, toluene is one of the best-studied neurotoxins, which has a severe impact on myelin of the central nervous system. The myelin sheath is a layer of fatty tissue that engulfs nerve fibers like insulation on a wire, speeding the transmission of electrical signals, and it is degraded by exposure to toluene--a chemical which is known to cause white matter changes and brain atrophy in the central nervous system. In an extreme example, abuse of toluene can produce a devastating neurological disorder characterized by dementia (6). Although some of these pathophysiological changes were observed at levels of exposure typical of chronic toluene abuse via the practice of huffing, it could be surmised that low-level chronic exposures to toluene via nail polish may also trigger more subtle, subclinical changes that over time pose a larger and cumulative detriment to health.

Dibutyl phthalate (DBP)

Many nail polishes in the early 2000s incorporated the plasticizer dibutyl phthalate (DBP), a compound which helps retain color, prevent chipping, and improve flexibility of the polish. A potent estrogen mimicking compound which induces testicular toxicity and impairs spermatogenesis, the process of the creation of new sperm (7), evidence has also mounted that DBP leads to obesity, interferes with thyroid health, and disrupts fetal development (8). That DBP was found to be a reproductive and developmental toxicant lead the European Union to ban its use in cosmetics in 2004 (8).

Following this legislative action, companies began to launch so-called "3-Free" polishes, devoid of the three most widely publicized toxic trio of chemicals, including DBP, toluene, and formaldehyde. A slew of "n-Free" labels emerged thereafter, without any standardization or formal regulations mandating which chemicals be omitted.

Triphenyl phosphate (TPHP)

In many cases, the phasing out of DBP was accompanied by its concomitant replacement with triphenyl phosphate (TPHP). A chemical primarily used as plasticizer or as a flame retardant impregnated into furniture and baby products under the pretense that it stops the spread of fire, TPHP is used in nail polishes to impart durability and flexibility. Some of its more common uses are in polyurethane foam, hydraulic fluids, varnishes, and lacquers (9).

Although data on the effects of TPHP on human health is inadequate, research links TPHP to endocrine disruption, meaning that it alters the exquisitely fine-tuned balance of human hormones that is so important for health. Other effects of TPHP include alteration of thyroid hormone levels, reproductive toxicity including decreased semen quality, altered metabolic function and weight gain, developmental toxicity, and genotoxicity (damage to DNA). There is even preliminary evidence in animal models that perinatal exposure to TPHP exacerbates the development of obesity and may accelerate onset of type 2 diabetes in UCDavis-type 2 diabetes mellitus rats (10).

Women may bear the disproportionate burden of exposure to this toxic chemical. Studies have shown that levels of the TPHP metabolite, DPHP, are approximately double in women relative to men (11). However, DPHP exposure is not exclusive to women alone, as it is in fact ubiquitous in the population, with one study of adults living in North Carolina demonstrating that it was present in 90% of the sample (11).

In another study, researchers set out to examine the extent to which nail polish is a source of TPHP exposure. Subjects provided urine samples before and after applying a brand of polish containing 0.97% TPHP by weight. Researchers found that diphenyl phosphate (DPHP), a byproduct of TPHP metabolism, increased by nearly seven-fold 10–14 hours after fingernail painting (9).

One 2015 study in Environment International found TPHP in concentrations of up to 1.68 percent by weight in 8 of 10 nail polishes tested, and what's more, 2 of the 8 polishes failed to disclose its presence on their product labels (9). Of more than 3000 products catalogued in the Environmental Working Group Skin Deep® cosmetic database, more than half disclose the use of TPHP, including popular brands such as Sally Hansen, Revlon, Maybelline, and OPI (9). All of this is especially troubling in light of industry statistics, which estimate that 97% of U.S. girls aged 12-14 use nail products, as the window during puberty is especially vulnerable for hormonal disruptions.

The Autoimmune Connection

Compounds in nail polish have also been linked to autoimmune disease, which is troubling since autoimmune conditions afflict nearly 50 million Americans and constitute one of the top 10 leading causes of death in females. In a case-control study conducted through the Canadian Network for Improved Outcomes in SLE (CaNIOS) published in the journal Rheumatology, researchers found relatively strong but imprecise associations between working in a setting that included nail polish applications and later development of systemic lupus erythematosus (SLE), an autoimmune disorder which affects multiple organ systems. People with lupus, in fact, were 10.2-fold more likely to have worked in job that entailed nail polish applications (12). Researchers conclude,

The markedly elevated risk of SLE among manicurists in our study adds further impetus for additional research on autoimmune-related effects of specific exposures found in this setting, or possibly from the components found in cosmetics and other beauty products" (12).

In addition, another large population-based study demonstrated significant associations between frequent nail polish use and risk of primary biliary cirrhosis (PBC), an autoimmune liver disease. The mechanism in the latter case, discussed by Vojdani in the journal Autoimmune Diseases, is that halogenated compounds in nail polish have affinity for mitochondrial proteins (13). In other words, chemicals in nail polish covalently bind to proteins within organelles of our own cells.

This leads mitochondrial proteins to exhibit enhanced immunogenicity, meaning that they are more likely to be recognized by the immune system as foreign and provoke an immune reaction. In this case, the immune system responds by producing the anti-mitochondrial antibodies which are typical of PBC (13). Animal studies likewise demonstrate the ability of phthalates contained in nail polish and other cosmetics to induce auto-reactivity--an attack against self.

"n-Free" Nail Polishes Still Contain Toxicants

The slew of brands that is capitalizing upon consumer demand for organic products has led to the unleashing of 3-, 5-, 7-, and 10- free nail polishes that impart a false sense of safety. These products are oftentimes active participants in the practice known as "greenwashing," wherein certain buzz words and ambiguous advertising slogans such as "nontoxic" or "natural"--which carry no legal weight--are used to capture the organic market. However, these 3-5-7-10-free nail polishes oftentimes still contain toxicants such as benzophenone-1, an endocrine disruptor with links to cancer.

A chemical filter used for the protection from UV radiation, benzophenone-1 is classified by the International Agency for Research on Cancer (IARC) as possibly carcinogenic to humans, and is linked to neuronal delay, congenital malformations, male infertility, and problems with behavioral development. There is also evidence of benzophenone-1 accumulation in placenta (14). Researchers in the Journal of Preventive Medicine & Hygiene write of benzophenone,

"These ingredients have good lipophilic properties and after only a few hours from their application on the skin, it is possible to detect them in biological fluids like maternal milk" (15).

Progress Going Forward: Redefining Self Care

It is incumbent upon us to call our legislators and demand that Congress improve the laws governing the regulation of cosmetics, as the only statute on the books has not been updated since 1938, and at present, only bans 11 ingredients, compared to over 1,300 presently banned in Europe. Currently, cosmetic companies are not required to submit safety records, report serious adverse events, disclose all ingredients, or adopt good manufacturing practices. The Food and Drug Administration (FDA) does not even have the authority to enforce the recall of personal care products that are deemed contaminated.

Not only is it past due time that we demand better regulations in the beauty industry, but it is high time that we reconceptualize the notion of what constitutes self care in terms that do not equate to sacrificing our health in the process. The predominant cultural meme around self-care is entangled both with consumerism and usage of endocrine-disrupting, cancer-causing products--facials, massages, and spa days replete with phthalate-laden chemicals.

But we can flip the script, and overturn this notion on its head at any time--both by practicing conscious capitalism and supporting companies that do their due diligence with ingredient quality, sourcing, and sustainability, and by reframing self-care as rituals that are less a blow to our wallet and more a deliberate practice of self-love. As strategies that bring us more than a temporary reprieve, a momentary sanctuary, and a transient dopamine hit. As ceremonies that ground us. That move us. That bring us home to ourselves. It is up to all of us to shift the narrative, to vote with our dollars, and to stop padding the wallets of products, corporations, and services that stand in the way of--rather than facilitate--women's health. No one should have to compromise their health span, and jeopardize their longevity, in the name of beauty.

References

1. Inci, M. et al. (2013). Toxic effects of formaldehyde on the urinary system. Turkish Journal of Urology, 39(1), 48-52.

2. Qiao, Y. et al. (2009). Irritant and adjuvant effects of gaseous formaldehyde on the ovalbumin-induced hyperresponsiveness and inflammation in a rat model. Inhalant Toxicology, 21(14), 1200-1207.

3. Liu, X. et al. (2017). Acute formaldehyde exposure induced early Alzheimer-like changes in mouse brain. Toxicology Mechanisms and Methods, 1-30.

4. Rodrigo Camara-Lemarroy, C. Et al. (2015). Acute toluene intoxication–clinical presentation, management and prognosis: a prospective observational study. BMC Emergency Medicine, 15(19). doi: 10.1186/s12873-015-0039-0

5. Hannigan, J.H., & Bowen, S.E. (2010). Reproductive toxicology and teratology of abused toluene. Systems Biology & Reproductive Medicine, 56(2), 184-200. doi: 10.3109/19396360903377195.

6. Filley, C.M. et al. (2004). The Effects of Toluene on the Central Nervous System. Journal of Neuropathology & Experimental Neurology, 63(1), 1-12.

7. Aly, H.A. et al. (2016). Dibutyl phthalate induces oxidative stress and impairs spermatogenesis in adult rats. Toxicology & Industrial Health, 2(8), 1467-1477.

8. Young, A.S. et al. (2018). Phthalate and Organophosphate Plasticizers in Nail Polish: Evaluation of Labels and Ingredients. Environmental Science Technology, 52(21): 12841–12850. doi: 10.1021/acs.est.8b04495

9. Mendelsohn, E. et al. (2016). Nail Polish as a Source of Exposure to Triphenyl Phosphate. Environment International, 86, 45-51.

10. Green, A.J. et al. (2017). Perinatal triphenyl phosphate exposure accelerates type 2 diabetes onset and increases adipose accumulation in UCD-type 2 diabetes mellitus rats. Reproductive Toxicology, 68, 119-129. doi: 10.1016/j.reprotox.2016.07.009.

11. Hoffman, K. et al. (2015). Monitoring Indoor Exposure to Organophosphate Flame Retardants: Hand Wipes and House Dust. Environmental Health Perspectives, 123(2),160–165.

12. Cooper, G.S. et al. (2010). Occupational and environmental exposures and risk of systemic lupus erythematosus: silica, sunlight, solvents. Rheumatology (Oxford), 49(11), 2172–2180.

13. Vojdani, A. (2014). A potential link between environmental triggers and autoimmunity. Autoimmune Diseases, 1-18. doi:10.1155/2014/437231

14. Valle-Sistac, J. et al. (2016). Determination of parabens and benzophenone-type UV filters in human placenta. First description of the existence of benzyl paraben and benzophenone-4. Environmental International, 88, 243-249. doi: 10.1016/j.envint.2015.12.034.

15. Panico, A. et al. (2019). Skin safety and health prevention: an overview of chemicals in cosmetic products. Journal of Preventive Medicine & Hygiene, 60(1), E50–E57. doi: 10.15167/2421-4248/jpmh2019.60.1.1080