Recent developments in nanomaterials in personal care products

01 Preamble

Personal care products - such as cleaners, moisturizers, deodorants, and sunscreens - are ubiquitous in modern life. Nanomaterials are increasingly being used in personal care products to improve product efficacy. For example, silver nanoparticles have anti-fungal and anti-bacterial properties, which are well suited for some efficacy skin care products and shampoos. Between 2012 and 2017, Nanodatabase (maintained by DTU Environment, the Danish Ecology Council and the Danish Consumer Council) increased its catalog of nanoproducts from 407 to 1,089, an increase of nearly 168%. This growth in nanomaterials requires consideration of the potential safety impact of these additives on consumers.

In this review, we first examined the existing literature on exposure, toxicity, and sustainability of nanoparticle additives. Then we look at US regulations and guidelines on how to deal with commercial applications of nanomaterials.

02 Dew

To gain insight into the types of nanomaterials contained in personal care products reaching consumers, we first analyzed online inventories of three types of nanomaterials. We compared the number of nano personal care products in the Consumer Product Catalog (CPI) to the number in the Nanodatabase and Skin Deep Cosmetics databases. Product catalogs in CPI and Nanodatabase search for "Health and Fitness," "Personal Care Products," "Cosmetics," and "Sunscreens," respectively. We then narrowed the search results to TiO2, ZnO, and Ag.

As of June 27, 2018, both CPI and Nanodatabase show that Ag is the most prevalent of the three nanomaterials (found in 158 products). ZnO is the least popular, being found in 29 products in CPI and 30 products in Nanodatabase. However, Skin Deep Cosmetics showed TiO2 to be the most common, with titanium dioxide found in nearly 97 percent of nano personal care products, while Ag was the least common.

The difference between Skin Deep Cosmetics versus CPI and Nanodatabase can be partially optimized by relevant search parameters. Skin Deep Cosmetics is specialized in classifying chemical products such as oils, waxes, creams, liquids, foams and powders. In contrast, CPI and Nanodatabase's "personal care products" category also includes non-chemical products such as straighteners, hair dryers, and combs. The Ag-enabled products cataloged in CPI and Nanodatabase contain a large number of such tools. After excluding the "personal care products" category in the CPI or "suspended in liquids" containing Ag, TiO2 became the most common nanomaterial.

By comparing the products containing TiO2, ZnO and Ag, the Skin Deep Cosmetics database is still different from the CPI and Nanodatabase, especially the latter two Ag is twice the former. In addition, while CPI and Nanodatabase indicate that Ag is the most widely used nanomaterial in personal care products, Piccinno et al report that the average annual production of TiO2(3,000 mt/year) and ZnO(550 mt/year) exceeds that of Ag(55 mt/year) worldwide.

According to the proportion of TiO2, ZnO and Ag, it is estimated that the proportion of cosmetics is 70-80%, 70% and 20% respectively. The output of cosmetics is shown in Table 2. The estimated yields of these three nanomaterials are TiO2 > ZnO > Ag, corresponding to the ranking in the Skin Deep Cosmetics database. Keller et al. estimate that the use of nanomaterials in cosmetics accounted for 16% of the global engineered nanomaterials in 2010.

Although the CPI and Nanodatabase information is not completely correct, we continue to use both databases because some products in the CPI are not found in Nanodatabase. We searched the "Health and Fitness" category and keywords such as "Cosmetics", "Personal Care" or "Sunscreen", and found a total of 981 personal care products in Nanodatabase, whose nanomaterial distribution is shown in Figure 1. Ag-containing products include soaps, sprays, and topical creams because Ag has good antibacterial properties. TiO2 and ZnO have been widely used in sunscreen emulsions because of their potential to absorb a broad spectrum of ultraviolet rays.

We also adjusted the position of nanomaterials in cosmetics through the classification structure reported in the literature. As shown in Figure 2, the majority of nanomaterialized products surveyed are used in products that can be suspended (57% of products), or attached to the surface of the product (36% of products). We observed that most products with surface-bound or solidly dispersed nanomaterials are tools, such as straighteners, hair dryers, and combs. Table 3 shows the data of TiO2, ZnO and Ag.

Product exposure scenarios vary depending on product type, nanomaterial type, and exposure pathway. Figure 3 and Table 4 show the results of the search after exposed path optimization. Based on the intended use of these products by consumers, we estimate that 90% of personal care products are made through contact on the skin, 6% through inhalation, and 4% through ingestion.

Most nano personal care products are creams, shampoos and other chemicals applied directly to the skin. The inhalation and ingestion risks of TiO2, ZnO and Ag are mainly through the types of products such as sunscreen powders, spray products and lip balms. Although most products are applied to the surface of the skin, these products can be indirectly inhaled or ingested during and/or after application to the skin. And that includes a potential eye exposure risk.