Recent developments in nanomaterials in personal care products

The available data on nanomaterials exposure in personal care products is not comprehensive. Because manufacturers are not legally required to disclose the amount of nanomaterials used in personal care products, we cannot estimate individual consumers' exposure to nanomaterials based on personal care product sales alone. A growing number of modelling studies assess consumer exposure to nanomaterials in consumer products, including cosmetics such as sunscreen, toothpaste or shampoo, and consumer products for children.

However, product-specific testing is required to verify that the estimates made using these models are correct. In the United States, the literature on nanoscale personal care products lacks standardized exposure models and comprehensive nanomaterial exposure data collection. Because the FDA does not require premarket exposure testing for nanomaterials, manufacturers are left to their own devices to confirm or deny the presence of nanomaterials in personal care products.

As a result, consumers do not have access to the data until the product is released. There are only limited, retrospective exposure analyses conducted by independent academic researchers who also attempt to characterize nanomaterials contained in personal care products. For example, Botta et al. studied four commercially available sunscreens and reported using ICP-AES to determine the percentage of TiO2 by weight from 3.72% to 5.33%. The concentration of additional products of nanoparticles reported in the literature is shown in Table 5. The data from these limited selection of consumer products justify the need for further research on personal care product exposure as a first step in regulation.

Recent studies on skin exposure have focused on sunscreens and moisturizers containing TiO2 and ZnO nanoparticles. The recommended amount of UV protection for the skin is approximately 4 oz/day, which corresponds to local exposure to approximately 60 g or 3.8 mg/cm2 of TiO2 and/or ZnO per day. However, skin contact is not limited to skin care products, but also includes casual skin contact with aerosols.

For example, using the ConsExpo and ECETOC TRA models, skin exposure after a single application of the nano-cleaning spray is estimated at 0.0106-1.43 mg/kg. However, the degree of dermal absorption reported in the literature varies, with some studies claiming that nanoparticles penetrate the skin barrier into the bloodstream, while others claim that nanoparticles are only present in the stratum corneum. To date, there is little evidence that nanomaterials can penetrate dermis under natural environmental conditions.

In some cases, those nanomaterials that can be used for dermal absorption show greater penetration of the epidermis, such as those found in wound dressings and anti-aging creams. After 4 to 6 days of use of silver-containing wound dressings, the scanning electron microscope (SEM) can observe silver clusters in the reticular dermis. Using icp to measure dry tissue, the total amount of Ag transferred to the skin was detected to be 40.1 μg /g (range 6-199μg /g).

Assuming a tissue mass of 150 mg and a bandage containing 4% Ag, the maximum amount of Ag measured by the skin species is 30µg. In another study, Ag nanoparticles were only found in the stratum corneum after human skin was exposed to textiles containing Ag nanoparticles for five consecutive days, which was inferred to be due to particle aggregation. The results show that the variation of Ag nanoparticles in the release depends on the incorporation method and wetting conditions of Ag.

Research into inhalation exposure of nano personal care products such as cosmetic powders and sprays has received a lot of attention. These results indicate that: (a) a small amount of nanomaterials are usually released during normal use of these products; (b) Released nanoparticles typically exhibit altered composition, shape and size due to interactions with other components; (c) The health effects of these interactions are still largely unknown. It is estimated that a person using a cleaning product containing nanomaterials at one time may inhale 3.3× 10-6.75 ×10-2 mg/m3.

For aerosol products containing Ag nanoparticles, Quadros and Marr estimate that 0.62 ng of Ag is inhaled after 20 sprays, which corresponds to an aerosol concentration range of 1.6× 10-7-3.7 ×10-5 mg/m3.

For nanopowder, the highest aerosol concentration measured in a controlled laboratory simulation was 3.4×104 units /cm3 at 14.1 nm. Depending on size, respiration rate, type of respiration (nose or mouth), and pre-existing lung conditions, aerosolized aggregates and pure nanomaterials appear to deposit. Smaller aerosols may penetrate deep into the respiratory tract, with 10-20nm sized aerosols deposited in the alveolar region.

The oral and ocular pathways of exposure appear to be the least studied. Oral exposure to nanomaterials in cosmetics may occur primarily with direct use of products such as toothpaste, mouthwash, or throat sprays. Dutch Romperberg et al. estimated that young children may consume 2.16μg TiO2/kg per day from food, supplements, and toothpaste. Using a toothbrush containing Ag nanoparticles may also lead to oral administration of silver nanoparticles. The literature reports that about 10 ng Ag is released in the form of 1-3% particles over 4 months, which is considered insignificant. Accidental ingestion can also accidentally transfer, by touching the hand to the mouth, by draining into the throat after inhalation, or by draining into the nasal cavity after eye exposure.