Each component of the headphone is rated either 'red', 'yellow', or 'green'.
A green rating means there is between zero and 0.8 mg/kg of harmful bisphenols.
A yellow rating means there is between 0.8 and 10 mg/kg.
A red rating means there is more than 10 mg/kg, which is the limit suggested by the European Chemicals Agency.
The one Apple product listed (Apple AirPods Pro 2. Gen. USB–C ) is all green.
Two of the Sony products listed have yellow for the ear-touching parts of the product (Sony Ult Wear and Sony Noise Cancelling WF–1000XM5). The other Sony products are green.
One of the Sennheiser products (Sennheiser Momentum Wireless 4 ) is listed as red for the ear-touching portion of the product.
One of the Bose products (Bose QuietComfort Headphones ) is listed as red for the ear-touching portion of the product.
Bisphenol A (BPA) appeared in 98% of samples, and its substitute, bisphenol S (BPS), was found in more than three-quarters. Synthetic chemicals used to stiffen plastic, BPA and BPS mimic the action of oestrogen inside organisms, causing a range of adverse effects including the feminisation of males, early onset puberty in girls, and cancer. Previous studies have shown that bisphenols can migrate from synthetic materials into sweat, and that they can be absorbed through the skin.
Well that sucks...
A challenge is that we operate with deny lists, not allow lists of these materials. A product may switch to be BPA-free, but what did they switch to and what are the effects of the substitute? Often we only get to know a decade later or more. From the linked article on the previous study which found shocking amounts of bisphenols in women's underwear[1]:
Experience shows that it can take up to 6 months for manufacturers to introduce a new chemical to the market. On the other hand, if these substances are found to be harmful, it takes on average 20 years (!) to ban them from consumer goods’ production.
I cannot find any mention of this on website of the "ToxFREE project" [0] or "ToxFree LIFE for All project" [1] (are these the same thing?). I want to see what headphones they tested and what the results from each one were, in addition to where the samples were taken from. Where's the data?
Two of the Sony products listed have yellow for the ear-touching parts of the product (Sony Ult Wear and Sony Noise Cancelling WF–1000XM5). The other Sony products are green.
One of the Sennheiser products (Sennheiser Momentum Wireless 4 ) is listed as red for the ear-touching portion of the product.
One of the Bose products (Bose QuietComfort Headphones ) is listed as red for the ear-touching portion of the product.