Nanoparticles in Sunscreens: Safety Matters and an Ivy Discovery
Nanoparticles and Sunscreen
Although sunlight is essential for life on Earth, it has its drawbacks. One of these is the ability of ultraviolet light to cause skin cancer. Some form of sun protection is necessary. For many people, this protection consists of sunscreen. Unfortunately, the skin can absorb certain chemicals, including some potentially harmful ones found in certain sunscreens. A secretion from the English ivy plant may provide a safer sunblock.
Mineral sunscreens contain either titanium dioxide or zinc oxide. They are often considered to be safer than chemical sunscreens, but they have a major drawback. The minerals give the skin a white appearance, which many people find unappealing. To avoid or reduce this whitening effect, many sunscreen manufacturers use the minerals in their nanoparticle form.
Nanoparticles are tiny and sometimes behave differently from particles of normal size. Sunscreens containing nanoparticles are generally considered to be safe. There are some concerns about the effect of the particles on our body in specific situations, however, such as when they are applied to damaged skin. The English ivy secretion contains nanoparticles that block ultraviolet light and might be safer than the ones produced from minerals.
The information in this article is given for general interest. Anyone with questions about sunscreen safety should consult their physician.
Titanium Dioxide and Zinc Oxide Sunscreens
Sunscreens containing titanium dioxide and zinc oxide are often called mineral sunscreens because both substances are found in the Earth. In contrast, chemical sunscreens contain sunblock substances produced in a laboratory. Mineral sunscreens are also known as physical sunscreens. They act as barriers to dangerous light rays by reflecting and scattering light. In their normal form, they appear to be safe and unable to penetrate the skin.
When chemicals are reduced to nanoparticles, their properties change. The change is often beneficial, as in the case of significantly reducing the white colour of mineral sunscreens. Nanoparticles are helpful in medicine, technology, and manufacturing. The ones produced by humans (as opposed to natural ones) are a relatively new creation. In many cases, their potential uses and effects are still being explored.
Nanoparticles are very tiny particles between 1 and 100 nm (nanometres) in diameter. A nanonmetre is a billionth of a metre or one millionth of a millimetre. The millimetre is the smallest division on a metric ruler.
Can Nanoparticles in Mineral Sunscreen Penetrate the Skin?
Cosmetics companies claim that titanium dioxide and zinc oxide nanoparticles in sunscreens can’t penetrate human skin. They say that the particles form a layer on the surface of the skin instead, thereby avoiding any damage to our bodies, and that any penetration is limited to the stratum corneum. The stratum corneum is the surface layer of the skin. It's composed of dead cells filled with keratin, a protein that prevents water loss from the body. Dead skin cells are gradually shed from our body.
The majority of the scientific research into mineral sunscreen safety agrees with the cosmetic companies. Most experiments show that healthy human skin is able to prevent penetration of nanoparticles or that the particles penetrate only the outer layer of the stratum corneum. Some experiments have raised questions, however.
Scientists have discovered that long exposure to a titanium dioxide sunscreen allows the nanoparticles to penetrate the skin of hairless mice. It's unclear how applicable this is to human life. Other researchers say that skin damaged by factors such as sunburn, shaving wounds, and blemishes may absorb nanoparticles to a greater depth than healthy skin. They also say that the smaller the nanoparticles, the further they can travel into the skin.
Skin contact with TiO2 is not likely to cause harm due to minimal penetration through the skin under normal use conditions. However, information on long-term use of sunscreens containing nanoparticles on hairy, damaged, flexed or aged skin is limited.— Australian Government Department of Health
Possible Effects of Titanium Dioxide and Zinc Oxide Nanoparticles on the Body
Titanium dioxide in the form of a dry and pure powder is considered to be a possible carcinogen (cancer causer). The general public doesn't encounter the chemical in this form in sunscreens. The problem may be a concern in certain industries, however.
Two main areas are being investigated in relation to sunscreen nanoparticle safety: the production of inflammation and damage to DNA.
- When titanium dioxide nanoparticles are injected under the skin of mice, they have been found to cause inflammation.
- When titanium dioxide or zinc oxide nanoparticles react with ultraviolet light, they produce reactive particles that can damage DNA. DNA, or deoxyribonucleic acid, is our genetic material. Sunscreen manufacturers use coated nanoparticles, however. The coating material prevents the nanoparticles from reacting with light.
- Not all nanoparticle coatings are equally effective. In addition, researchers are trying to discover whether some coatings are removed by the chlorine in swimming pools, as research suggests.
- Some scientists say that we should be investigating the effects of sunscreen nanoparticles that enter the lungs or digestive tract.
At the moment, there seem to be fewer safety concerns about zinc oxide nanoparticles than titanium dioxide ones. The European Commission considers sunscreens with nano titanium dioxide to be safe for healthy, intact, or sunburned skin but says that inhalation could be dangerous. It says that powders or sprayable products containing titanium dioxide nanoparticles should not be used.
The American Cancer Society says that it's important that we choose a sunscreen that we are reasonably comfortable with and use it regularly. The society says that the potential development of skin cancer is a more serious concern than the possible danger of sunscreens.
Does the safety of sunscreens worry you?
A Potentially Safer Sunscreen From English Ivy
Mingjun Zhang is a scientist at the University of Tennessee. He has found that ivy nanoparticles block ultraviolet light from the sun much better than conventional sunscreens containing nanoparticles. In fact, the ivy sunscreen may be four times better than a mineral sunscreen at protecting us from the dangers of sunlight. In addition, the ivy particles are sticky and should adhere to skin more effectively.
When he tested isolated cells, the scientist found that the English ivy particles were not toxic to the cells, while titanium dioxide nanoparticles showed significant toxicity. In addition, the scientist found that the ivy particles could be broken down by protein-digesting enzymes, which suggests that they would be biodegradable in the human body.
It has been suggested—but not proved—that the ivy particles would be unlikely to penetrate skin because of their relatively large size. Another advantage of the ivy sunscreen would be the fact that it could be almost colourless, depending on the carrier liquid. Mingjun Zhang is investigating additional biomedical uses of the ivy particles.
English ivy is an attractive garden plant and wall covering or a noxious weed, depending on where it's located and one's point of view. The plant grows aggressively and can be invasive in some habitats. Its vertical stems form adventitious roots that enable the plant to attach to surfaces.
The English Ivy Plant
English ivy (scientific name Hedera helix) is a popular evergreen plant in gardens. It grows fast and is a great climber. Rootlets extend from ivy stems to attach them to tree trunks and walls. These rootlets produce a yellow, adhesive liquid that not only enables ivy to cling to vertical objects but also contains nanoparticles that can block ultraviolet light.
The English ivy plant is native to Europe and Asia but has been introduced to other parts of the world. It can grow in the shade created by trees and is a popular ground cover in dark areas. It also grows well when exposed to full sunlight. Ivy can form an attractive coat on the walls of houses and is able to climb as high as 50 meters (164 feet) in a favourable habitat. The plant needs to be trimmed frequently since its growth can quickly get out of control. When it escapes from gardens, it’s often regarded as a weed and an invasive species.
Juvenile ivy leaves have three to five lobes, but adult leaves are not lobed. Instead, they are oval and have a pointed tip. The small flowers occur in clusters and have a green-white color. The fruit is a black, berry-like structure.
English Ivy Nanoparticles
A new sunscreen with a safety profile that most scientists accept would be very useful. English ivy might provide such a sunscreen.
The yellow secretion containing ivy's nanoparticles is produced by its adventitious roots. Adventitious roots are those that are produced in an unusual location, such as from an above-ground stem. The ones produced by ivy are short and are known as rootlets. The secretion is released by the fine hairs covering the rootlets.
Ivy nanoparticles have a diameter of 60 to 85 nm and are generally larger than those in mineral sunscreens. Mineral sunscreen nanoparticles come in a range of sizes but may be as small as 20 nm in diameter.
The science is the easy part. The hard part is the economics, the millions of dollars it takes to get FDA approval.— Joe Laszlo, Agriculture Research Service in Peoria, Illinois, via phys.org
Testing a New Sunscreen
As exciting as the University of Tennessee discoveries are, more research needs to be done. A usable English ivy sunscreen has to be created, tested, and approved. I haven't seen any news announcing that these steps have happened yet.
Even when researchers have demonstrated that a substance is helpful, it may take a long time to be approved for public use by a federal agency. One reason for the delay after a potentially helpful product has been created is the safety tests that must be performed. As might be expected, heath agencies want to see that any substance put on or in the human body is safe. The testing and approval process for a product sometimes takes years and may be expensive. The quote above comes from a scientist who has discovered another natural substance that appears to act as a sunscreen.
If an English ivy sunscreen is created and if it's shown to be safe as well as effective, new commercial products may appear. Additional sunscreen choices for consumers would be a great outcome of the research and tests.
- Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness" from the US National Library of Medicine
- "Depletion Of The Protective Aluminum Hydroxide Coating In TIO2-Based Sunscreens By Swimming Pool Water Ingredients" from the Environmental Protection Agency, or the EPA
- "Nano Titanium Dioxide" from the Australian Government Department of Health
- Sunscreen with titanium dioxide nanoparticles from the European Commission
- English ivy may give sunscreen a makeover from the Eurekalert news service
- A scientist has created a sunscreen from ivy from the phys.org news service
- Ivy adhesive nanoparticles for biomedical applications (a grant application with details about the particles) from Grantome
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
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© 2011 Linda Crampton