ANTI-POLLUTION
Preventing UV damage with copper chelation
Sarah Glynn - Innospec
As humans our body is constantly swimming in our exposome, and exposure to our environment can have positive effects on our bodies, whether that be exposure to phytoncides released from trees which increase the activity of cells which release anti-cancer proteins,1
or pollens released from those same
trees which cause the allergic reaction known as hay fever. One of the many boons and assaults on
our body is UV radiation, which is the primary source (estimated 90%) of the body’s vitamin D,2
However,
as well as being shown to produce a positive effect on mood and depression.3
exposure to UV radiation is also infamously known to cause sunburn, skin cancer and premature ageing of the skin, and it is estimated that 65-90% of melanomas are attributable to UV exposure.4
UV radiation: affects any part of the body in its path It is not just our skin which is affected by UV radiation: our hair is also weathered by exposure to UV radiation. This exposure is a less considered environmental insult to the hair, as the main culprits of hair damage are seen to be heat, mechanical stress, moisture, and beauty treatments. The transformative effects on the hair of
UV radiation have been at times coveted by consumers, with there being many instances throughout history of lemon juice being used to enhance the lightening effect of photobleaching, or through more modern-day beauty products which also recreate the subtle lightening effect of photobleaching. The overall effect of UV radiation on hair
however can be considered as negative, as even the gentle lightening effect is due to the damage of melanins present in the hair. That is to say, UV radiation is the initiator for oxidative reactions which can take place on and in the hair which lead to structural damage of the hair fibre.5
Understanding UV: how UVA and UVB interact with the hair fibre UV radiation is only one part of the electromagnetic spectrum of radiation and can be categorised into UVA and UVB radiation. UVA and UVB are differentiated in terms of UVA has a longer wavelength which is between 400-320nm, and UVB has a shorter wavelength between 320-280nm.6
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While both wavelengths can penetrate the
hair fibre, UVB radiation only penetrates the top 5μm of the hair fibre where the cuticle resides, and therefore the morphological damage received by the hair from this radiation is concentrated in the cuticle layer.7 The longer wavelength UVA radiation can
penetrate further into the hair fibre, and can reach as far as the cortex.7
Hair protein loss from
UV exposure takes place when hair fibres are irradiated with UV radiation with wavelengths between 254-400nm.9 This range encompasses both UVA and
UVB regions of the electromagnetic spectrum, with UVB being the more prolific of the two forms for protein damage.7
Exposure of the hair
fibre to UVA radiation additionally causes the aforementioned photobleaching of the hair by inducing chemical changes in eumelanin (oxidative fission of o-indolequinone moiety) and pheomelanin (conversion of benzothiazine to benzothiazole moiety and chain elongation).8
Beyond UV: amino acids and oxidative damage The protein damage received by the hair from UV radiation varies depending on the amino acids that are being irradiated, as their chemical structure determines their susceptibility to UV radiation. The amino acids cysteine,
methionine, tryptophan, tyrosine, and histidine are the most prone to UV damage.9 Chromophores present in these amino acids
are susceptible when UV radiation is absorbed, whether that be the C-S bonds of cysteine and methionine or the conjugated pi systems of tryptophan, tyrosine and histidine.7 A well-known byproduct of cysteine oxidation is cysteic acid10
and it has been
chosen as a biomarker to determine the amount of oxidative damage the hair receives from UV exposure, as cysteic acid has extensively been used as such to determine the effect of oxidative hair damage. Cysteine makes up 11-18% of the amino acids
present in keratin, of which the hair fibre is made up of 65-95%,11
therefore the hair fibre is
cysteine rich enough that it can be considered indicative of the hair’s overall level of oxidative damage.
Where does copper come into it? In this tale of UV radiation, amino acids, and the hair fibre, the transition metal copper may seem out of place. However, copper along with other metals are also part of the hair’s exposome, and can penetrate the hair fibre as part of everyday weathering. Copper can penetrate the hair fibre when it contacts the hair while being dissolved in water,
October 2025 PERSONAL CARE
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