しかしながら、これらの溶剤は発がん性が指摘された。

、。

However, these solvents have been pointed out as carcinogenic.

Literal

However, these solvents [topic-は] carcinogenicity [subject-が] was-pointed-out.

Academic-register writing. しかしながら ('however,' 'nevertheless') is a formal/written counterpart to しかし or でも, used mostly in essays, academic writing, and formal speeches. 発がん性 ('carcinogenicity') is a Sino-Japanese compound: 発 (generate) + がん (cancer, usually written in hiragana or 癌) + 性 (property) = 'the property of causing cancer.' The 性 suffix is productive for forming '-ness/-ity' nouns. 指摘される is the passive of 指摘する ('to point out') — a common academic/news collocation for noting something noteworthy or problematic.