As a result of the COVID19 pandemic, ultraviolet (UV) steriliser is currently the craze right now, so much so that UV equipment suppliers have reported record sales. Is such UV equipment useful in killing viruses? How much exposure is required? Is UV light safe on baby bottles?
UV Radiation and the Electromagnetic Spectrum
UV light is part of the electromagnetic spectrum. It is at the higher end of energy compared to visible light and is followed in energy by X-rays and the Gamma rays.
To answer this, we need to understand that the UV spectrum in sunlight contains three types of UV. First there is UVA, which makes up the majority of the UV radiation reaching the Earth’s surface. UVA light is responsible for tanning and can cause premature aging as well as damage that can lead to skin cancer.
Next there’s UVB, which can damage the DNA in our skin, leading to sunburn and eventually skin cancer (recently scientists have discovered that UVA can also do this). Both are reasonably well known, and can be blocked out by most good sun creams.
"UVC is really nasty stuff – you shouldn't be exposed to it" – Dan Arnold
There is also a third type: UVC. This relatively obscure part of the spectrum consists of a shorter, more energetic wavelength of light. It is particularly good at destroying genetic material – whether in humans or viral particles. So, only one type of UV light kills germs but they are also extremely dangerous.
|| Wavelength Range (nm)
||320 - 400
||280 - 320
||100 - 280
Effect of UVC on Humans and viruses
According to the Skin Cancer Foundation, UVC is also carcinogenic and harmful. Luckily, most of us are unlikely to have ever encountered any. That’s because it’s filtered out by ozone in the atmosphere long before it reaches our fragile skin.
And because UVC radiation is so dangerous, UVC light emitting devices used by hospitals to kill pathogens on surfaces and in the air, are only used when rooms are unoccupied. Even then, the amount of UV light required varied widely, depending on factors such as the shape and type of material the virus was on. Based on a report from BBC, the verdict is still not quite out yet as to whether UVC is effective on coronavirus.
Effect of UVC on Plastics
In the same way UV rays such as from sunlight are harmful and damaging to our skin, plastic can be affected too. Plastic fibers are now found in many modern day applications and among them, most baby bottles.
UV radiation attacks all types of polymers, but some show better UV resistance than most. The UV breaks down the chemical bonds in a polymer in a process called photodegradation, which ultimately causes the change in appearance and deterioration in properties. The main visible effects are
- chalky appearance
- dis-discoloration (yellowing or whitening) of the material,
- brittleness in the material
Polypropylene (PP) and polyester are two families of plastics that are commonly found in day-to-day uses.
Polypropylene is a simple chain polymer. It is frequently used in packaging, food containers, laboratory equipment, and in applications that require heat, chemical, or electrical resistance.
It has a high degradation rate when exposed to UV light like the Sun due to its chemical structure. The UV light weakens the plastic by causing the bond holding the polymer to break, making polypropylene unsuitable for uses that require long term exposure to sunlight. PP is also widely used in most baby bottles due to its cost effectiveness.
If you are using PP bottles, it is advisable to store them in a place away from the sun or avoid prolonged exposure to UV light.
Polyester is different. It is a family of plastics that share a similar structure of an ester between two binding R-groups.
With regards to UV resistance, polyester performs better relative to PP. According to studies from North Carolina State University, polypropylene fibers can only withstand approximately 6 days exposure to high-intensity UV light before losing 70% of their strength, while data shows polyester fibers can withstand 12 months exposure to sunlight and still retain over 67% of their strength.
Tritan, Polyphenylsulfone (PPSU) and Polyethersulphone (PES) are examples of polyester plastics.
While polyester are more UV-resistant than polymers (e.g. PP), it is still recommended to avoid prolonged exposure of the bottles to the sun or UV light.
In additional to plastics, Ultraviolet (UV) rays also accelerate the deterioration of Silicone silicone material commonly used for teats, straws and pacifiers of many brands of baby care products. This degradation lead to hardening of silicone material which may cause crack and tear on products.
We understand during this pandemic period, some may prefer to be more cautious with regards to germs and viruses. If you are one of them, please exercise extra precaution when using UV light emitting devices. We generally recommend using a good cleaning/washing liquid instead.
If you have no choice and really have to expose your bottles to sunlight or UV light, choose a glass bottle as most commonly used glass are highly resistant to UV radiation. Alternatively, you could change your plastics bottles more frequently than usual if you believe in using UV sterilisation.