Optical brighteners are synthetic chemicals added to products such as laundry powders, liquid, soakers and other cleaning products to give an illusion of cleaner surfacesⁱⁱ. In laundry powders they adhere to clothes^iv and reflect light in the blue spectrum while absorbing UV light. This makes clothes appear whiter and cleaner to the human eye, however this is purely aesthetic. Because optical brighteners are designed to stick to clothes, they end up being in contact with our skin for prolonged periods of time, which raises some concerns about the effects of these chemicals on skin and possible irritation (although there is only limited evidence to suggest this). Optical brighteners can also end up in waterways, where they are slow to biodegrade^iv and can therefore cause long term effects on the aquatic environment. They can also adhere to plants, where their UV absorbing effects can disrupt bee pollination^vii.

REFERENCES:

ii) Optical brightener - Wikipedia, the free encyclopedia

iv) Human & Environmental Risk Assessment on ingredients of European household cleaning products Substance: Fluorescent Brightener FWA-1

vii) Effects of Optical Brighteners Used in Bio pesticide Formulations on the Behaviour of Pollinators