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

Policy Corner: California's 30x30 Initiative

By Bryan Pride • February 11, 2026
In 2020, Governor Newsom committed California to an ambitious goal: conserve 30% of our lands and coastal waters by 2030. This “30x30” initiative isn’t just about setting aside more protected areas; it’s a comprehensive strategy to protect biodiversity, expand equitable access to nature, and build resilience to climate change across California’s diverse landscapes and waters. California has made meaningful progress towards the 30x30 goal. Currently, 24.4% of our lands and 16.2% of coastal waters meet the 30x30 conservation criteria, defined as areas that are durably protected and managed to sustain functional ecosystems and the diversity of life they support. But with less than five years remaining, we still need to conserve millions of additional acres to reach this critical goal. The Power In Nature Coalition No single organization can achieve 30x30 alone. That’s why Tuleyome is a proud member of the Power In Nature Coalition; a network made powerful by the collective work of over 250 community groups, conservation organizations, land trusts, and Indigenous organizations working together to conserve and protect the diverse landscapes of California. This statewide network coordinates advocacy, identifies priority conservation projects , and ensures that 30x30 implementation protects biodiversity, fosters meaningful relationships, and partners with state agencies and diverse communities. Power In Nature works on multiple fronts: defending conservation funding in state budgets, identifying potential 30x30 projects across California, and advocating for policies that support rather than undermine conservation progress. Power In Nature has multiple regional groups to elevate geographical priorities and empower local organizations to connect state-level policy to on-the-ground conservation work in their communities. Tuleyome’s Role in Advancing 30x30 At Tuleyome, our work protecting the Berryessa Snow Mountain National Monument directly contributes to California’s 30x30 goals. We’re actively engaged with Power In Nature’s Sacramento Valley regional group, as well as the Far North and Bay Area regional groups, helping coordinate conservation efforts across our region and connecting local priorities to statewide advocacy. Tuleyome has also participated in Power In Nature Advocacy Days, where we met with state elected officials to discuss policies and legislation that further or hinder the 30x30 conservation goals. How You Can Support 30x30 Whether you’re a landowner, community member, or fellow conservation advocate, there are many ways you can support 30x30 progress. There are multiple qualifying conservation lands that have not been added to the Conserved Areas Explorer and this is one of the many ways people can get involved to help track areas protected. If you’re interested in learning more about 30x30 activities in your region, check out the Power In Nature regional groups and sign up to attend monthly regional meetings or gain access to Power In Nature’s newsletter. Most importantly, through Power In Nature, you can make your voice heard by participating in local advocacy days or contacting your state legislators to encourage their support for full funding to conservation agencies and protection of environmental review processes. California’s commitment to conserve 30% of our lands and waters by 2030 is achievable, but only if we work together to make it a reality. If you have questions about how to get involved with 30x30 or Power In Nature, don’t hesitate to reach out! Bryan Pride Tuleyome Policy Director

Monumental Questions - Even Better Birding in the Monument?!

By Kristie Ehrhardt • February 11, 2026
You might already know that the Berryessa Snow Mountain National Monument (Monument) is a wonderland for birdwatchers. With a range of habitat types from aquatic, riparian, native grassland, oak woodlands, conifer forests to subalpine the range of species found in the Monument is staggering. If you prefer to break it down by county rather than habitat, western Colusa County boasts a birders paradise in Bear Valley and Lake County offers the shores of Clear Lake. Napa County showcases Quail Ridge Reserve and Lake Hennessey. Yolo County puts forth a plethora of hot spots including Putah Creek, Lake Solano, and the Cache Creek preserve which is home to Bald and Golden Eagles, Osprey and others! And, this is just a smattering of the treasure trove for bird nerds to enjoy in the nearly 345,000 publicly accessible acres of Monument. But, how do you know where and when to go to see what? Even if you’re an experienced birder, it can be overwhelming to know where and when to begin. I know people that travel to different states to check birds off of their “life list”. I also know people, some of them are those same people, that travel all over the globe to get a glimpse of a rare bird - or maybe it’s just rare to someone from Sacramento. Either way it’s enticing and rewarding to be part of a community with a common interest. There’s almost a secret code between birders. There’s definitely a code to name abbreviations and a spiffy way to keep count if you’re recording them. There’s also a way to estimate the number of birds in a flock but if you’re just wanting to sneak up on a feathered friend near or far, how do you know where to start? Try downloading the Cornell Lab eBird app. The app lets you input your own findings as well as investigate other people’s observations. You can base your search on your location or use a near or far location that you’d like to go explore. Or, you can browse by species and see exactly where to go to find them. The eBird app uses citizen science and operates similarly to the iNaturalist app, a favorite among biologists, naturalists and other interested folks. With the eBird app, you can contribute your sightings or even sound recordings to the community platform making it the largest birding community in the world. You can also create your own lists and have the app track them for you. The app not only makes birding more inclusive and interesting for individual birders but it is beneficial for the network of scientists as well. The combined data from the app helps conservationists understand how numbers of birds shift as well as aiding in developing genetic species distribution models that show where and when birds are in the region. This information helps develop and establish better conservation strategies for individual species and collective populations of birds. The app is easy, fun and rewarding for novice and veteran birders, conservationists, scientists and ultimately the birds themselves.

Enjoying Outside! - Visit the Capay Valley Almond Festival!

By Kristie Ehrhardt • February 11, 2026
The Capay Valley Almond Festival has been a regional tradition since 1915. It showcases the Esparto/Capay Valley region and was originally held in the fall after the almond harvest was complete. Years later it was rescheduled to occur on the last Sunday in February to celebrate the almond trees while in blossom. The Almond Festival is the only local celebration that not only incorporates the dazzling landscape but it also honors five Capay Valley towns: Esparto, Capay, Brooks, Guinda and Rumsey. The 21-mile route along Highway 16 covers each town, offering their own unique ambiance and activities all while celebrating the almond bloom in Yolo County. You will also find local crafts, family fun, delicious food and other entertainment at each location. A bit about California’s almond history! Much like the European Starling’s initial introduction into the United States, the first attempt at almond production in California was not as glorious as anticipated. Almond trees were first planted in California as early as 1853 using European varieties that were not adapted for our climate conditions. Most of these subpar trees were either converted into other fruit trees or used for firewood. Even though the inaugural attempt wasn’t fruitful (haha, get it?), lessons were learned about cross pollination and where to plant the next go-around. Science happened and by the 1880’s other varieties were being cultivated and during the Citrus Fair in 1886, the two varieties that are still grown today were introduced. By the 1900’s cross pollination tactics advanced and were in place and our commercial production was on its way. This combined with the fact that almond trees were productive in soils that were too sandy for other fruit trees and could be prolific without the use of much artificial water, the crop finally seemed to be destined for success. During the twenty year span between the mid 1960’s and the mid 1980’s, irrigation methods advanced and became more available to land in the San Joaquin Valley, which held ideal conditions for almond production, creating a booming industry that still remains today. In 2020, 1.25 million acres of California were in almond production. We yield 2.8 BILLION (!) pounds of almonds which provides 100% of the United States commercial supply and over 80% of the world’s demand. Almonds are in the top five most valuable California exports bringing in almost five billion dollars.