I can answer this question in strictly literal terms, but might not be able to get to the root of what you're asking.

Records of a foundry being active in the neighborhood called getto actually disappear in the mid-1400s, over fifty years prior to the forced removal of the city's Jewish residents to the neighborhood. What seems to have happened is that over the course of the 15th century, the assignment of state contracts to select foundries for the armament of war-galleys had concentrated economies of scale such that most foundries without state charters either went out of business or moved to the eastern part of the city (close to the Arsenal) in the hope of earning spillover work or subcontracts. It would seem the foundries in Cannaregio are among these: by the 1460s, proto-Real Estate entrepreneurs (the Da Brolo brothers) dispose a will mentioning homes in the neighborhood that they had built (or intended to build — the documentation is vague) with the intention to renting them (and the Da Brolo family crest is still visible on the wellheads in the Ghetto, possibly indicating there wasn't a whole long going on in the neighborhood prior to the brothers developing the land since wells/cisterns are pretty much the first thing the Venetians built when expanding the city). There is actually very little documentation at all on the getto foundry itself, but we can deduce it seems to have smelted mostly (even exclusively) bronze, and was certainly tapped to provide naval artillery in the late 14th and earliest 15th century. It is possible that the neighborhood came to be synonymous with the foundry because there just wasn't a whole lot there apart from the foundry itself.

This doesn't exclude that there were health problems experienced by the ghetto's residents, however they were more likely linked to overcrowding and sanitation rather than to the activity of early heavy industries in the vicinity. Unfortunately I don't know of any study or book examining the demographic evolution of the Venetian Ghetto and can't offer more details, sorry I can't be of more help!