Enjoying Outside - How Sunscreen Works

Kristie Erhardt • August 9, 2024

Photo: Holtenwellness.com

 

Ultraviolet (UV) light or radiation is a form of energy from the sun. On the electromagnetic scale, UV light has shorter wavelengths than visible light, which is why humans can’t see it, but longer wavelengths than X-rays. However, we can most definitely feel it; UV light is what causes sunburns, suntans and freckles, as well as more serious skin and eye diseases. Thankfully our atmosphere, primarily our ozone layer, filters out a lot of this radiation which is why reducing and minimizing impacts to air quality is so important. There are many types of ultraviolet light but the four most commonly known are: UVA, UVB, UBC and Near-ultraviolet. UVA has the longest wavelengths of the UV lights and is primarily associated with skin aging. It is not absorbed by the atmosphere at all and can penetrate deep into the middle layer (dermis) of the skin. UVB has shorter wavelengths than UVA and is associated with skin burning and affects mainly the outer layer (epidermis) of the skin. Much of the sun’s UVB is absorbed by the atmosphere. UVC has the shortest wavelength and is useful as a germicide. In nature it is completely absorbed by the atmosphere. Near-ultraviolet light is visible to insects, fish, some birds and some mammals. UVA and UVB have been proven to harm the DNA in skin cells leading to an increased risk of damage, premature aging and possibly even skin cancer. Exposure to UVA and UVB light can also cause eye damage such as cataracts and some cancers. However, some UV light is beneficial. Exposure to UVB is responsible for the formation of vitamin D and in some climates or locations that don’t have abundant sunlight, vitamin D may need to be supplemented. UVC is known to kill active microbes such as viruses and bacteria. Recent work has indicated that use as a germicide may make indoor air as pure as outdoor air which could greatly lessen the transmission of viruses in indoor settings such as schools and hospitals.     

 

Thankfully for those of us that like to spend extended time outdoors, modern science has gifted us with sunscreen that can help prevent sun damage while we play or work outside. Although there are different types of sunscreens and they work in different ways, their main objective is to prevent UVA and UVB radiation from reaching the surface of your skin. 

 

Physical sunscreens contain very finely ground minerals such as zinc oxide or titanium dioxide that physically sit on the surface of the skin and act as a shield to reflect the sun’s rays away from our skin. The minerals are what causes most mineral sunscreen, sometimes called sunblock, to be a dense consistency and look white on the skin. Physical sunblocks work extremely well and rarely cause irritation or allergic reactions (both zinc oxide and titanium dioxide are main ingredients in diaper rash creams) and it's these types of sunscreens that are considered reef safe or reef friendly because they aren’t leaving added chemicals in the ocean.

 

The ingredients in chemical sunscreens create a thin film on the skin that absorbs the ultraviolet radiation before it reaches the surface skin. These sunscreens are usually clear or rub in to be invisible which is more appealing to a lot of people but can cause stinging or irritation to the skin. These types of sunscreens usually contain about 20% of the active ingredient and the rest is emollients, stabilizers and fragrances which are responsible for the irritation for some people. Chemical sunscreens come in a variety of formulas from gels, creams, lotions and sprays.

 

Sun Protection Factor (SPF) is a way to measure how effective that sunscreen or block is. It is a measure of how much UV light gets to the surface of your skin. As it would seem, the higher the SPF number, the higher the protection factor. That doesn’t mean that you can stay out in the sun longer without reapplying though, it simply means that it’s filtering out more or less of the UV rays. An SPF of 30 allows about one-thirtieth (or 3.3%) of the UV to reach the surface of your skin which means that it filters about 96.7% of the UV light. Doctors and those in the skin care industry recommend a sunscreen with at least an SPF of 50 or greater.

 

Broad spectrum sunscreens provide protection from both UVA and UVB light. Many broad spectrum sunscreens are a combination of both physical and chemical blockers and are the most effective sunscreens. Sunscreen should be applied 15-30 minutes before going out in the sun and reapplied at least every two hours or more frequently after swimming, sweating or towel drying. Sport and water-resistant sunscreens should stay on wet skin and be effective for 40-80 minutes. All sunscreen should also be applied liberally; at least a teaspoon for the face and neck, another teaspoon for each arm and leg, another for the front and another for the back of the body. A good estimate is about a shot glass worth of sunscreen for your entire body. And don’t forget to do your ears, they take a beating sitting out there on their own. There are even specific sunscreens available for your hair and scalp.

 

In general, sunscreens are considered safe as long as you’re not allergic to any ingredients and it’s best to use sun protection daily, even on cloudy days. Water, sand and snow reflect sunlight and can result in a nasty and unexpected burn. For babies under six months of age, doctors recommend clothing and hats with SPF rather than sunscreens that can irritate their delicate skin.

 

So slather it on, front and back, top to bottom, and go enjoy the outside!

RECENT ARTICLES

March 5, 2026
Tuleyome is pleased to announce that Nate Lillge has been promoted to Program Director where he will oversee Tuleyome’s land conservation and stewardship program and our adventures, outreach and education program.  Nate joined Tuleyome ten years ago. A talented manager with a passion for the outdoors and sharing it with others, Nate has been key to Tuleyome’s successes, from the design, building and maintenance of some of our region’s iconic trails to the expansion of Berryessa Snow Mountain National Monument with the addition of Molok Luyuk. Nate is a true partner to all, dedicated to this place and its communities, an authority on the region, and a true champion of the land. Nate has spent his career dedicated to the experience and stewardship of place. Fun, knowledgeable, dedicated and brilliant, Tuleyome welcomes our new Program Director, Nate Lillge.
By Bryan Pride March 5, 2026
Just months after we rejected the notion of selling off our public lands, some in Congress are at it again. This time, the attack is more calculated; bypassing the communities, tribal nations, and local stakeholders who spent years shaping how our public lands are managed. Whether you hunt, fish, farm, hike, or simply love the outdoors, Congress is now overriding your voice and threatening the legal foundation that protects your access to these lands. What is the Congressional Review Act? The Congressional Review Act (CRA) was passed in 1996. It required that all federal agency “rules” be submitted to Congress and gave Congress 60 days to pass legislation to disapprove the rule. If Congress takes no action, the rule goes into effect. For nearly 30 years, the CRA was used sparingly, only used to review federal regulations. But Congress has now started using the CRA in a new and unprecedented way: to overturn Bureau of Land Management Resource Management Plans (RMPs) and National Monument Management Plans ; the blueprints that guide how our public lands are managed and protected. Resource Management Plans (RMPs) and National Monument Management Plans aren’t just paperwork. They are the result of years of public engagement that include tribal consultation, community input and scientific analysis that determine how millions of acres of public land are used and protected. These plans govern everything from recreation use and grazing permits to oil and gas leases, conservation designations, and wildfire management. Why this is everyone’s problem For decades, neither BLM nor Congress considered these plans to be “rules” subject to congressional review. They were understood as long-term planning documents: overarching guidance for how agencies managed land, embracing principles appropriate to the particular lands and their characteristics. Land management plans have never, in the 50 years we’ve been preparing and following them, been considered rules. That is, not until this Congress. Since October 2025, Congress has rescinded five BLM management plans covering tens of millions of acres in Alaska, Montana, and North Dakota and overturned a decision that protected the Arctic National Wildlife Refuge from oil and gas leasing. By treating these plans as “rules” subject to the CRA, Congress has called into question the legal validity of every management plan finalized since 1996. At threat are 123 BLM plans and 176 active Forest Service plans covering over 166 million acres, 14 of them are in California, including those governing Berryessa Snow Mountain National Monument and other lands in the region An Attack on One Monument is an Attack on All The CRA threat has now reached our National Monuments. As of February 26, 2026, Senator Mike Lee formally began the process of fast-tracking the destruction of the Grand Staircase-Escalante National Monument Management Plan in Utah, the first time the CRA has ever been applied to a National Monument. The Grand Staircase-Escalante National Monument Management Plan took years to develop. BLM engaged in extensive government-to-government consultation with tribal nations who have lived in and around the monument since time immemorial; nations whose ancestral cultural sites are woven throughout the monument’s 1.9 million acres. Local governments, ranchers, outfitters, scientists, conservationists, and community members all had a seat at the table. The result is a plan that balances wildlife protection, outdoor access, dark night skies, grazing, and cultural preservation, reflecting the full breadth of what makes Grand Staircase-Escalante, known as the “Science Monument”, so remarkable. What makes the decision particularly alarming is the irreversibility. Once Congress rescinds a management plan under the CRA, BLM is barred from issuing another plan that is “substantially the same.” without another act of Congress. Years of tribal consultation, community collaboration, and scientific analysis cannot simply be redone, and the protections that came from that work cannot be easily restored. The monument’s geology, fossils, wildlife habitat, grazing access, and cultural resources would all be left in a management vacuum, vulnerable to illegal vehicle use, landscape-level clearcutting of native pinyon-juniper forests, and unchecked extractive activities. This is the pattern. What happens in Utah, Alaska, Montana, and North Dakota today sets the precedent for what can happen at Berryessa Snow Mountain National Monument and every other monument. Once Congress establishes that Monument Management Plans are fair game to be overridden through congressional review, no monument, no matter how beloved, no matter how many years of work went into its protection is truly safe. An attack on one monument is an attack on all of them. What Tuleyome is doing about it We’re working with a nationwide coalition to prevent further misuse of the CRA. We are supporting legislation clarifying that land management plans are not subject to the CRA. We are ensuring that our elected officials know how much the public supports public lands and wants them protected. We are committed to fighting back, working alongside community members, tribal nations, and coalition partners to keep our public lands in public hands. We will continue to monitor developments and keep you informed. What you can do about it. Contact your representatives and let them know that public lands belong to all of us, and decisions about how they are managed should stay rooted in our communities, not decided in Washington D.C. Ask them to vote against resolutions that use the CRA to roll back our resource management or monument management plans. Monitor Tuleyome’s social media to stay up to date on fast moving issues and see how you can help. Connect with efforts to protect the Grand Staircase-Escalante National Monument Management Plan. Stay tuned. We’ll let you know what’s happening and how you can make a difference.
By Kristie Ehrhardt March 5, 2026
Yes, indeed! Although I do not advocate for eating things you find in nature, there is one plant in particular that is both lovely to look at and to nosh on. As you may have heard, we here at Tuleyome are beginning to schedule wildflower tours of our very own “deep home place”, the Berryessa Snow Mountain National Monument (Monument). One of the plants that is a reliable observation, easily identifiable and flowering right now as we speak is miner’s lettuce! I must first say please do not harvest miner’s lettuce from the Monument as it is not only delightful for us to look at, it is an important food source for caterpillars and butterflies. Miner’s lettuce ( Claytonia perfoliata ) belongs to the Purslane family - Montiaceae. Claytonia is one of 17 genera and 230 known species that range from small, herbaceous plants to woody shrubs. Many of the genera of Montiaceae are edible and that does include miner’s lettuce. Miner’s lettuce is native to western North America from Mexico to as far north as British Columbia. Apparently European explorers liked it so much that they carried it back to Europe with them in the 18th century and cultivated it at the Kew Botanical Gardens in London, It has since naturalized throughout the natural landscape. Utilized by Native Americans for generations, miner’s lettuce is a valuable source of vitamins and minerals. During the gold rush, settlers ate it to prevent scurvy, hence the clever common name. According to a study published in the Journal of the American Dietetic Association, a mere 100 grams of miner’s lettuce, about the size of a dinner plate, contains about 35% of your recommended daily amount of vitamin C, 22% of vitamin A and about ten percent of the iron required daily. It also contains protein and the entire plant, with the exception of the roots, is edible, even the itty bitty flowers. Young stems are tender and sweet while the succulent leaves have a bright, fresh taste and seem to melt in your mouth. Strangely enough, we found out last weekend that domestic goats do not care for it; apparently chewing on the rope holding the fence panels together was more tantalizing. It’s also been noted that deer tend to ignore it as well. Entire pages have been dedicated to the plant lauding it for its yumminess in salads, sandwiches and even sushi. Although it is delicious raw, personal experience speaking here, with a very light salad dressing or even just a splash of lemon juice; it can also be cooked as used as you would spinach. However, like spinach, the plant can contain toxic amounts of sodium oxalate which may potentially promote kidney stones among other terrible things. Miner’s lettuce is common in the spring and can usually be found in a moist, shady environment. After a good rain it may pop up in sunny areas but the best stands are usually in well-shaded, cool areas. As the temperatures rise, the plants in the sunny areas begin to dry up and turn blush pink to a deep red. Plants in dryer locations have a bitter taste. It is easy to identify with its basal rosette, many long petioles and leaves that wrap completely around the stem looking like saucers or little lily pads. In young plants these leaves will be bright green and heart-shaped but as the plants mature, they become more rounded or cup-shaped. Mature plants may also have tiny, dainty white to light pink flowers dangling from the center of the saucer-shaped leaf. The plant usually flowers from February to May or even June if conditions are right. While I most definitely do not promote harvesting plants in native or natural ecosystems, miner’s lettuce can easily be cultivated in your own backyard! The best flavor comes from a cool, shady, damp location so plan for an early crop. But, it can also tolerate full sun if the soil remains good and moist. Miner’s lettuce also seems to favor occasional minor ground disturbance and growing it as a seasonal ground cover can be pleasing to the eye and the tummy! Miner’s lettuce can be planted in late summer to early fall in mild climates and harvested all winter. It can also be sown in the spring and with apple water be harvested until the summer heat arrives. The plants can be cut and allowed to regrow several times a season as long as they are eventually allowed to finally flower and set seed as they are an annual species and reproduce by seed. Miner’s lettuce can be used in any recipe that calls for fresh, steamed or cooked greens. Eat your vegetables! Next time you’re hiking in our favorite Monument (you know which one!) keep an eye out for miner’s lettuce and give it a nod. You might find it in several of the habitat types there including chaparral, oak woodlands, riparian and maybe even a parking lot!