The original white lead pigments have oxidized and turned black.

原来白色的铅颜料已经氧化发黑了。

《柯林斯英汉双解大词典》

The lead pigments are a big source of lead pollution.

含铅颜料是主要的铅污染源。

youdao

Glaze is mostly translucent, but da Vinci would also slip in small amounts of pigments, such as manganese and lead oxides.

釉料大多是半透明的，但达芬奇也会添加少量色素，如锰，氧化铅。

youdao

Some of the older pigments are lead-based and difficult to acquire because of EU health-and-safety regulations.

WSJ: Forging Ahead With a Goya Classic

Glaze is mostly translucent, but da Vinci would also slip in small amounts of pigments, such as manganese and lead oxides.

ECONOMIST: The da Vinci method

The albino condition, caused by a lack of colouring pigments in the skin, can lead to the animal being susceptible to sunburn, but the zoo said its wallaby enclosure had lots of shade and it should lead a "normal life".

BBC: Rare albino wallaby born at Linton Zoo