Artists used a lot of pigments or other materials, that are highly toxic, such as arsenic, mercury or lead. Some of those materials were in use for hundreds of years.
Are there any known cases of great masters, who got sick from working with such toxic elements? Or at least diseases (or maybe fatalities), where such a causality is suspected?
I know it's not exactly what you're after, as you're probably referring to visual artists. But both Beethoven and Handel, it has been postulated, may have died due to lead (or arsenic) poisoning of some sort - due to posthumous tests done on strands of their hair showing high lead content.
So it's quite likely some artists did too... However, like Beethoven there, one of the problems is posthumously diagnosing such illnesses, which may have been written off as something else at the time:
Sir Isaac Newton and Ludwig van Beethoven are but two notables whose body lead burden identifiable from their hair would today constitute poisoning.
Sources: David Hunter Handel's Ill Health: Documents and Diagnoses (2008): Royal Musical Association Research Chronicle, No. 41, pp.69-92.
Russell Martin Beethoven's Hair (2001): Broadway Books.