Bits of Rays

Differences between UV rays

There are a few differences between the sun's harmful Ultraviolet A and Ultraviolet B rays:

• UVA
• Penetrates the inner skin tissue and affect the cells that produce elastin and collagens that help keep our skin elastic. Thus a major contributor to skin damage, skin cancer and immune system damage.
• Intensity of rays is constant during the day.
• Not filtered by plain glass.
• Penetrates deeper than UVB enhancing UVB's carcinogenic effects.
• Lack of universal standard method to measure UVA protection in sun protection products.
• UVB
• Affects the outer layer of skin and the primary cause of tan and sunburn
• Intensity of rays highest during the summer between 10am-2 pm.
• Filtered by plain glass.
• Associated with an increased risk for basal and squamous cell cancers and melanoma skin cancer.
• Produces Vitamin D.
• Protection from UVB rays is indicated by a SPF rating on sun protection products.


• UVC
  • Completely absorbed by the atmosphere and therefore no effects to humans.

Common UV Filters

1. Chemical/synthetic compounds penetrate the skin and absorb UV rays:

• The Good - can be formulated for broad-spectrum protection against UVA and UVB by combining several substances, some providing UVA protection, some UVB protection, and some both.
• The Not-so-Good - many chemicals used for their absorption characteristics are linked to skin irritation, hormone disruption, and damage to skin cell DNA. See our Sunscreen Ingredients to Avoid List.
• Chemical sunscreens may also contain fragrance, preservatives, synthetic dyes, mineral oil and petrochemicals.


2. Mineral-based compounds stay on skin's surface and reflect and/or scatter UV rays:

• The Good - physically blocks UV rays by lying on top of skin. Zinc oxide and titanium dioxide block both UVA and UVB rays.
• The Not-so-Good - titanium dioxide (TiO2), the most common ingredient in "non-chemical sunscreens" has shown phototoxicity (or the capability to damage skin upon exposure to light), but as a sunblock appears to be safe.
• To ensure a more transparent application, manufacturers use nanometer-sized particles which may be able to penetrate the skin. See Avoid list. (some feel the "white nose" made famous by beach lifeguards is unattractive … go figure!).



3. Broad Spectrum Sunscreen - protect from both UVA and UVB.

Sunscreen vs. Sunblock

• Sunscreens absorb and reflect the sun's rays via a chemical reaction - the chemicals actually bind to cellular molecules to absorb and dissipate UV rays into the skin.
• Sun blocks - like zinc oxide and titanium dioxide - are opaque mineral-based chemicals that deflect and physically prevent UVA and UVB rays from penetrating into the skin.
• Most commercial products offer a combination of the two.
• Note that on sunscreen labels companies rarely distinguish between sunscreens and sunblock, and instead use the term "sunscreen" for both. Look for zinc oxide or titanium dioxide as the active ingredient when choosing sun protection.

Active Ingredients

Sunscreen and sunblock labels must identify the active ingredients designed to provide the sun protection.

Mineral-based sunscreen class their active ingredients as natural health products.

• Titanium dioxide
• Titanium oxide
• Zinc oxide

Chemical sunscreen active ingredients are products that contain any of these ingredients and are classified as a “drug product”.

Active Ingredients that protect against...

What is SPF?

• Sun Protection Factor.
  
• Rates the protection only against UVB rays - the rays that cause sunburn.
  
• SPF rates how much longer exposed skin will take to burn with the sunscreen on it compared to without it. For example, an SPF 15 means that if your skin usually burns in 10 minutes, instead your skin would burn in 10 times 15 minutes, or two and a half hours.
• 15-30 SPF range is suitable for most people. Over 40 SPF does not provide much greater benefit and generally requires more chemicals ingredients to increase SPF.
  

Waterproof

Water resistant and very water resistant can be used on a label to describe the sunscreen/sun block’s ability to maintain its protection while in the water. In Canada, sun protectors that are very water resistant can identify on the label that they are water-proof.

Photostability

Sunscreens break down in the sun - this is called photoinactivation (the ability of sunscreen to resist rays at various wavelengths). All active ingredients (except titanium dioxide and zinc oxide) absorb the sun's energy so it doesn't penetrate our skin, and then releases that captured energy by breaking apart, reacting with other chemicals in the sunscreen, or even kicking off free radicals. Photostability (refers to the ability of a sunscreen to remain intact) may vary among sunscreen formulations. The Environmental Working Group analysis indicated that 54% of products on the market contain ingredients that may be unstable alone or in combination, causing consumers to receive less protection than they expect. In particular, some “active ingredients”, like avobenzone, octyl methoxycinnamate, octyl dimethyl PABA, break down more readily than others when exposed to sunlight, lose their ability to absorb the sun's harmful rays, and stop working effectively in as little as 30 minutes, up to several hours.

Manufacturers are not required to produce stable products. The test used to establish a product's UVB rating accounts for stability in part, since it tests the product in simulated sunlight on human volunteers over the time needed to produce a sunburn. A product's UVA protection, however, is not subject to testing and rating, and the filters that contribute to UVA protection in a product may or may not be stable.

Nanoparticles

Nanoparticle technology is the micro-sizing of minerals like zinc and titanium to reduce the size of the mineral compounds so when applied on skin they are transparent as opposed to opaque white.

There are concerns about the health and environmental effects with two sides of the argument:

1. The Environmental Working Group summarized literature and concluded that nanoparticles applied topically showed no absorption of small-scale zinc and titanium sunscreen ingredients through healthy skin. They rate zinc and titanium based products as the safest and most effective compounds for sun protection available but note concern for nanotechnology and call for further research.

2. Friends of the Earth suggest that the smaller particles can penetrate the body and create unnatural biochemical reactions. They cite the lack of reliable safety data and lack of standard labeling as concerns.

Natural Alternatives

Some “organic” (as in their natural state) elements have mild UV blocking properties. These include unrefined Shea Butter, coconut oil, and other oils. There are not a lot of studies in this area and others mainly recommend using a tried-and-true product with “active ingredients”. Nevertheless, some of these products, have reported good antidotal results, and are suitable for skin moisturizing and after sun care. (Patti uses the Shea Lav on her shoulders and legs each day in the summer).

A few more tidbits

• Medications and topical retinoids (such as alpha hydroxy acids) increase sun sensitivity.
• Check with your pharmacist about medications, and read cosmetic labels for sun-sensitizing products.
• Take extra care to apply sunscreen every day, and wear appropriate clothing and a hat when outdoors.

Links

Environmental Working Group, Sunscreen database, 2007
Sun. Canadian Cancer Society, 2007
Sun Safety. Canadian Dermatology Association, 2007
Health Canada fact sheets: Babies, Children and Sun Safety, A Parent's Guide to Sun, and Air and Sun Protection
How Sunburn and Sun Tans Work by Marshall Brain, How Stuff Works, retrieved from webstie June 17, 2007
Using SunSense, Canadian Cancer Society, 2007.
What Sunscreen Should I Use? Vincent Standley. The Green Guide, 2005.
Increasing use of high sun protection factors in sunscreen products, Roche, Inc.
Sunscreens and Sunblocks - Product Report, The Green Guide, June, 2006
A Consumer Guide for Avoiding Nano-Suncreens, Friends of the Earth, 2007