Dr Shaun Presow (Manager Hazardous Substances Reassessments at the Environmental Protection Authority) shines some light on how sunscreens work, what’s in them, and how the EPA is ensuring they are safe to use.
This is an excerpt from the EPA’s Science at work series of science communication stories.
We use sunscreen on our skin to protect it from the harmful effects of ultraviolet (UV) light by absorbing, blocking, or reflecting this UV radiation.
But to understand how sunscreen does this, we need to know what we’re protecting ourselves from and why.
What is UV light and how does it affect us?
UV radiation is a form of energy from the sun that you can’t see because its wavelengths are shorter than visible light.
It is usually subdivided into UVA, UVB, and UVC - too much UVB is the main cause of sunburn.
Some exposure to UVB rays is good for us and helps our bodies produce vitamin D - an essential vitamin for healthy bones, muscle strength, and maintaining a healthy immune system.
Although sunlight is necessary for us to function, UV light can also be harmful and wearing sunscreen is one of the best ways to protect our skin from these harmful effects.
Exposure to UV can cause a variety of changes to our skin, both cosmetic and more serious, and it increases the risk of developing skin cancer - the most common cancer affecting New Zealanders.
What is in sunscreen
Sunscreens are made from a variety of ingredients, the most important being sun filters that block the UV rays and protect your skin from the sun. These are called the active ingredients.
These creams, lotions, and sprays also need to be spreadable and feel nice, so other ingredients called formulation stabilisers and sensory enhancers are also added.
Some sunscreen companies add other ingredients, such as aloe vera, that don’t have an impact on how the sunscreen works but are added to make the product stand out from the competition.
What are the types of active ingredients in sunscreens?
The active ingredients in sunscreens fall into two types - mineral and chemical. Each type uses a different mechanism for filtering UV radiation.
What is SPF?
The sun protection factor (SPF) of a sunscreen is a measure of how well it protects the skin from sunburn.
It indicates how long it takes untanned skin to start to redden with sunscreen applied compared to how long it takes without any sunscreen.
For example, SPF 50 filters around 98 percent of the UV, so only 1/50 of the radiation will reach your skin and it will take 50 times longer to burn than without sunscreen protection.
SPF ratings are mainly for UVB protection, as this light is the main cause of sunburn. ‘Broad-spectrum’ sunscreen protects you from all types of UV light.
How the EPA ensures sunscreens are safe
The EPA sets the rules for sunscreen ingredients under the Cosmetic Products Group Standard. These rules are for all cosmetic products, including sunscreen, and ensure that products are safe for people and the environment.
To further protect people, we’ve recently updated the rules to bring them in line with international developments, and to continue protecting consumers and our environment.
Continue reading the story: Taming the sun – the science of sunscreen | EPA
